U.S. patent application number 15/308966 was filed with the patent office on 2017-04-20 for system and method for generation of reactive oxygen species and applications thereof.
The applicant listed for this patent is Clean Chemistry, Inc.. Invention is credited to Wayne Buschmann.
Application Number | 20170107128 15/308966 |
Document ID | / |
Family ID | 50233510 |
Filed Date | 2017-04-20 |
United States Patent
Application |
20170107128 |
Kind Code |
A1 |
Buschmann; Wayne |
April 20, 2017 |
SYSTEM AND METHOD FOR GENERATION OF REACTIVE OXYGEN SPECIES AND
APPLICATIONS THEREOF
Abstract
Reactive oxygen species formulations as well as methods for
making and using such formulations. Reactive oxygen species
formulations comprising one or more parent oxidants, such as
peroxides, or peroxyacids, and one or more reactive oxygen species.
(ROS). The formulations optionally contain in addition one or more
reactive species other than ROS. The reactive oxygen species and
other reactive species when present provide chemical reactivity,
oxidative activity and/or antimicrobial activity not provided
otherwise by the parent oxidant.
Inventors: |
Buschmann; Wayne; (Boulder,
CO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Clean Chemistry, Inc. |
Boulder |
CO |
US |
|
|
Family ID: |
50233510 |
Appl. No.: |
15/308966 |
Filed: |
September 7, 2013 |
PCT Filed: |
September 7, 2013 |
PCT NO: |
PCT/US13/58650 |
371 Date: |
November 4, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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61698550 |
Sep 7, 2012 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C01B 13/00 20130101;
C02F 2103/06 20130101; C07C 409/26 20130101; C02F 1/722 20130101;
C02F 2103/002 20130101; C07C 407/00 20130101; C25B 1/30 20130101;
C25B 9/06 20130101; B09C 1/002 20130101; C09K 8/54 20130101; C07C
407/00 20130101; C02F 1/4672 20130101; C02F 2103/007 20130101; C25B
9/08 20130101; C02F 2103/10 20130101; C09K 8/528 20130101; A61L
2/186 20130101; C01B 13/145 20130101; A01N 59/00 20130101; C07C
409/26 20130101; A01N 2300/00 20130101; A61L 2202/21 20130101; A01N
37/16 20130101; C02F 1/66 20130101; C11D 7/04 20130101; A61L 2/0088
20130101; B09C 1/08 20130101; C25B 9/02 20130101; A01N 37/16
20130101; C02F 2305/023 20130101; C02F 2305/02 20130101; B09C
2101/00 20130101; A61L 2/18 20130101; A01N 59/00 20130101; C09K
8/524 20130101; C09K 2208/32 20130101; C02F 2303/04 20130101 |
International
Class: |
C02F 1/72 20060101
C02F001/72; C25B 1/30 20060101 C25B001/30; C25B 9/06 20060101
C25B009/06; C01B 13/00 20060101 C01B013/00; A01N 59/00 20060101
A01N059/00; A61L 2/18 20060101 A61L002/18; C11D 7/04 20060101
C11D007/04; C01B 13/14 20060101 C01B013/14; C02F 1/66 20060101
C02F001/66; C07C 407/00 20060101 C07C407/00 |
Claims
1. A method for generating a reactive oxygen species formulation,
the method comprising: generating an alkaline hydrogen peroxide
solution; mixing the alkaline hydrogen peroxide solution with an
acyl donor such that a peracid concentrate is produced, wherein the
peracid concentrate has minimal hydrogen peroxide residual;
adjusting the pH of the peracid concentrate to the activated pH
range for generating the reactive oxygen species.
2. The method of claim 1 wherein the reactive oxygen species
formulation is a singlet oxygen precursor formulation.
3. The method of claim 1 wherein the reactive oxygen species
formulation comprises singlet oxygen and superoxide.
4. The method of claim 1 wherein the acyl donor is an acetyl
donor.
5. The method of claim 1 wherein the alkaline hydrogen peroxide
solution is generated from the combination of an alkali and a
hydrogen peroxide concentrate or wherein the alkaline hydrogen
peroxide solution is generated electrochemically.
6. The method of claim 5 wherein the reactive oxygen species
formulation is a singlet oxygen precursor formulation.
7. The method of claim 5 wherein the reactive oxygen species
formulation comprises singlet oxygen and superoxide.
8. The method of claim 5 wherein the acyl donor is an acetyl
donor.
9. The method of any one of claims 1-8 wherein the hydrogen
peroxide solution is generated using a molar ratio of
H.sub.2O.sub.2 to alkali in the range 1:1.2 to 1:2.5
10. The method of any one of claims 1-8 wherein the peracid
concentrate is produced by mixing the alkaline hydrogen peroxide
solution with the acyl donor such that the molar ratio of hydrogen
peroxide to acyl donor is in the range 1:1.25 to 1:4.
11. The method of any one of claims 1-8 further comprising the step
of further activating the reactive oxygen species using activation
chosen from a Fenton or Fenton-like catalyst, ultrasound,
ultraviolet radiation or thermal activation.
12. The method of any one of claims 1-8 further comprising the step
of further activating the reactive oxygen species using activation
chosen from a Fenton or Fenton-like catalyst, ultrasound,
ultraviolet radiation or thermal activation and wherein the
reactive oxygen species formed in the further activation step is
hydroxyl radical.
13. The method of any one of claims 1-8 further comprising storing
the alkaline hydrogen peroxide in a holding tank for immediate or
future use.
14. The method of any one of claims 1-8 further comprising the step
of distributing the reactive oxygen species to its point of use,
wherein the reactive oxygen species is distributed in at least one
form chosen from the group consisting of: the form of a liquid, an
ice, a foam, an emulsion, a microemulsion and an aerosol; and
wherein the reactive oxygen species is applied to the point of use
by an application chosen from the group consisting of: injection,
flooding, spraying, and circulation.
15. The method any one of claims 1-8 wherein the alkaline hydrogen
peroxide concentrate is electrochemically generated, has a pH in
the range of 12.0 to 13.0, and has a percent weight of hydrogen
peroxide in the range of 0.1 to 3 wt %.
16. The method any one of claims 1-8 wherein the alkaline hydrogen
peroxide concentrate is electrochemically generated, and the acid
concentrate is co-generated during the step of electrochemically
generating the alkaline hydrogen peroxide concentrate.
17. A reactive oxygen species precursor formulation comprising a
peracid concentrate comprising a mixture of alkaline hydrogen
peroxide and an acyl donor. wherein the precursor formulation is
capable of generating singlet oxygen by the reaction of alkaline
hydrogen peroxide and the acyl donor; the precursor formulation
having minimal hydrogen peroxide residual to minimize quenching of
singlet oxygen, and the precursor formulation having a pH between
6.5 and 12.5.
18. The reactive oxygen species precursor formulation of claim 17
wherein the molar ratio of hydrogen peroxide to acetyl donor
reactive groups is in the range 1:1.25 to 1:4.
19. The reactive oxygen species precursor formulation of claim 17
further comprising superoxide.
20. The reactive oxygen species precursor formulation of claim 19
wherein the initial molar ratio of superoxide to peracid ranges
from 5:1 to 3:1.
21. The reactive oxygen species precursor formulation of claim 19
wherein the initial molar ratio of superoxide to peracid ranges
from 3:1 to 0.7 to 1.
22. The reactive oxygen species precursor formulation of any one of
claims 17-21 wherein the initial pH ranges from 6.0 to 9.5.
23. A singlet oxygen formulation prepared by reacting the precursor
formulation of any one of claims 17-21 with an acid concentrate
resulting in formation of both peracetic acid and peracetic acid
anion,
24. The reactive oxygen species of claim 23 exhibiting an ORP of
600 mv vs SHE or more.
25. The reactive oxygen species of claim 23 exhibiting an ORP of
700 mv vs SHE or more.
26. A method for generating a superoxide formulation comprising:
electrochemically generating a solution containing a mixture of
superoxide and peroxide wherein the molar ratio of superoxide to
hydrogen peroxide co-generated ranges from 0.01:1 to 10:1 and the
pH ranges from 8 to 13.
27. The method of claim 26 wherein an acid concentrate is
co-generated during the step of electrochemically generating a
superoxide solution and the method further comprises a step of
adjusting the pH of electrochemically generated solution with the
co-generated acid.
28. The method of claim 26 further comprising a step of diluting
the superoxide solution to near point of use concentration.
29. The method of claim 26 wherein the electrochemically generated
solution contains hydroperoxyl radicals or hydroxyl radicals.
30. The method of claim 26 further comprising the step of further
activating the electrochemically generated solution using
activation chosen from a Fenton or Fenton-like catalyst,
ultrasound, ultraviolet radiation and thermal activation, to
produce a radical species.
31. A superoxide formulation prepared by electrochemically
generating a mixture of superoxide and hydrogen peroxide wherein
the molar ratio of superoxide to hydrogen peroxide co-generated
ranges from 0.01:1 to 10:1 and the pH is 8-13.
32. The superoxide formulation of claim 21 wherein the pH is
12-13.
33. A method for oxidizing one or more environments or substrates
which comprises contacting the one or more environments or
substrates with a reactive oxygen species formulation of claim
23-25 or which is prepared by the method of any one of claims 1-8
or claims 26-30.
34. A method for oxidizing one or more environments or substrates
which comprises contacting the one or more environments or
substrates with a reactive oxygen species formulation of claim
23-25 or which is prepared by the method of any one of claims 1-8
or claims 26-30 which comprises: cleaning in place of pipes, tanks
and other processing equipment; removal of contaminants from water
including wastewater, greywater, raw water, produced water or
ground water; denaturing or killing microorganisms; soil
decontamination or remediation; hard surface cleaning or
decontamination; cleaning of membrane filtration systems; flushing
of well casings and water distribution pipes; and in-situ chemical
oxidation.
35. A method for oxidizing one or more substances in an environment
which comprises contacting the one or more substances with a
formulation comprising superoxide and singlet oxygen.
36. The method of claim 35 which comprises: cleaning in place of
pipes, tanks and other processing equipment; removal of
contaminants from water including wastewater, greywater, raw water,
produced water or ground water; soil decontamination or
remediation; hard surface cleaning or decontamination; cleaning of
membrane filtration systems; flushing of well casings and water
distribution pipes; and in-situ chemical oxidation.
37. A method for treating waste water comprising: which comprises
contacting the one or more environments or substrates with a
reactive oxygen species formulation of claim 23-25 or which is
prepared by the method of any one of claims 1-8 or claims
26-30:
38. A method for treating waste water comprising: electrochemically
co-generating a cathode output solution comprising superoxide and
hydrogen peroxide; mixing the cathode output solution into a waste
water source; and optionally adjusting the pH of the cathode output
solution before the step of mixing the cathode output solution into
a waste water source.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. provisional
application 61/698,550 filed Sep. 7, 2012, which is incorporated by
reference herein in its entirety.
BACKGROUND
[0002] It is well known that a combination of reactive oxidant
species can be beneficial to water treatment, cleaning,
decontamination and remediation applications as they will combat a
variety of substrate types which may be present and react with a
variety of oxidation byproducts during their breakdown.
[0003] Several common issues arise with the use of conventional
reactive oxygen species formulations including, for example,
limited shelf life, low mobility of oxidants and/or catalysts;
highly acidic or alkaline oxidants which cause significant changes
in the natural soil or groundwater pH; limited options for oxidant
types available from a single product or system; and logistic,
cost, regulatory (e.g., permitting requirements), or safety issues
associated with bringing large quantities of strong oxidizers and
hazardous chemicals on site. Additionally, the use of conventional
iron-based hydrogen peroxide Fenton catalysts and sodium persulfate
activators, such as iron (II) sulfate, require an acidic pH of less
than 4 to be active, but as the pH increases toward neutral pH, the
precipitation of iron oxides and oxyhydroxides occurs. Precipitated
iron can cause pore plugging in soils, fouling and staining of
equipment and can promote population blooms of iron bacteria which
cause biofouling of soils, and accelerated microbial corrosion of
steel well casings, pipes and equipment.
[0004] This invention relates to methods and systems for generating
reactive oxidant species, as well as to formulations contain such
reactive oxidant species and particularly to formulations
containing mixtures of different reactive oxidant species. The
formulation of the invention provide for improved activity and
overcome problems associated with the use of such formulation.
[0005] The invention further provides methods of use of the
inventive formulation, particularly in which the improved activity
of the formulations is employed. The invention in particular
provides methods water treatment.
[0006] Reactive Oxygen Species are discussed in the following.
Hydroxyl Radicals
[0007] Of the common oxidants used in water treatment and
remediation, the hydroxyl radical has the most positive standard
oxidation potential of 2.80 V and is very effective at oxidizing a
wide variety of substances. Hydroxyl radicals react very rapidly
with a wide variety of oxidizable substrates. However, the hydroxyl
radical lifetime is very short in aqueous media, merely several
nanoseconds, and therefore must be produced within several tens of
angstroms of a target substrate due to minimal diffusion path
length. Hydroxyl radicals can further be quenched by undesirable
reactions including reactions with radical quenchers, precursor
oxidants and other hydroxyl radicals. For example, carbonate and
bicarbonate ions present in natural waters are effective radical
quenchers. Further, hydrogen peroxide and ozone can react with
hydroxyl radicals; therefore when generating hydroxyl radicals from
hydrogen peroxide and/or ozone precursors in water, the precursor
is traditionally kept below 10 g/mL to avoid excessive consumption
of hydroxyl radicals by the parent oxidant.
[0008] One issue with using hydroxyl radicals in water treatment is
their ability to oxidize halide salts with much lower standard
potentials and even to oxidize sulfate dianion to the persulfate
radical anion. A single electron oxidation of halide by a hydroxyl
radical will produce hypochlorous acid, hypobromous acid and their
hypohalite forms depending on the pH. However, an excess of
hydroxyl radicals in the presence of hypohalites will further
oxidize the hypohalites in subsequent steps to chlorate, which is
toxic, and bromate, which is carcinogenic.
[0009] Fenton Catalyst Activation
[0010] Fenton catalyst activation of hydrogen peroxide occurs when
a reduced iron species, Fe.sup.2+, is oxidized by hydrogen peroxide
thereby producing hydoxyl radical (.OH), and an oxidized iron
species, Fe.sup.3+. The catalytic cycle is completed when hydrogen
peroxide reduces Fe.sup.3+ back to Fe.sup.2+ thereby producing
hydroperoxyl radical (HOO.), which is in equilibrium with
superoxide. The Fenton process is summarized in Equations A and
B:
Fe.sup.2++H.sub.2O.sub.2.fwdarw.Fe.sup.3++.OH+OH.sup.- Eq. A:
Fe.sup.3++H.sub.2O.sub.2.fwdarw.Fe.sup.2++.OOH+H.sup.+ Eq. B:
Similar Fenton-like chemistry occurs with other peroxides such as
peroxyacetic acid. Iron sulfate is the most common Fenton catalyst
and must be used at a pH near or below pH 4 to avoid excessive
precipitation of Fe.sup.3+ oxides and oxyhydroxides. Other iron
catalyst forms such as iron minerals (e.g., magnetite) and chelated
iron compounds have stability at higher pH.
[0011] Ultrasound Activation
[0012] Ultrasound activation of hydrogen peroxide in aqueous
solution occurs when ultrasound waves induce cavitation of water
forming bubbles, which leads to very high localized heating as
cavitation bubbles collapse resulting in the thermal dissociation
of hydrogen peroxide to hydroxyl radicals as in Equation C.
H.sub.2O.sub.2+heat.fwdarw.2.OH Eq. C:
Similar thermal dissociation of peracids occurs to generate two
different radical species as in Equation D.
AcOOH+heat.fwdarw.AcO.+.OH Eq. D:
[0013] Ultraviolet Activation
[0014] Ultraviolet light activation of hydrogen peroxide occurs by
the absorption of ultraviolet light, typically in the wavelength
range of 180 to 220 nanometers, which leads to dissociation of
hydrogen peroxide forming hydroxyl radicals as summarized in
Equation E.
H.sub.2O.sub.2+UV light.fwdarw.2.OH Eq. E:
Similar ultraviolet activation and dissociation of peracids occurs
to generate two different radical species as in Equation F.
AcOOH+UV light.fwdarw.AcO.+.OH Eq. F:
[0015] Thermal Activation:
[0016] Thermal activation of hydrogen peroxide can be conducted,
for example, by impinging a liquid, spray, mist, vapor, or steam
containing hydrogen peroxide upon a hot surface coated with a
catalyst (e.g., silver oxide, iron oxide, ruthenium oxide, glass,
quartz, Mo glass, Fe.sub.3-xMn.sub.xO.sub.4 spinels,
Fe.sub.2O.sub.3 with Cu-ferrite, MgO and Al.sub.2O.sub.3.) and
heating to above 200.degree. C., to form hydroxyl radicals as in
Equation G.
H.sub.2O.sub.2+heat+catalyst surface.fwdarw.2.OH Eq. G:
[0017] The initial peroxide activation step in Equation G is
followed by a series of radical propagation steps in the gas phase
where intermediate radical species form such as the hydroperoxyl
radical.
[0018] Singlet Oxygen
[0019] Singlet oxygen is molecular oxygen in an excited electronic
state. Singlet oxygen is most commonly produce in aqueous solutions
by photolysis of dissolved oxygen directly by ultraviolet radiation
or indirectly by energy transfer from a visible light
photsensitizer dye to molecular oxygen. However, the use of
photosensitizing dyes such as methylene blue, certain
metalloporphyrins, semiconductors and other materials to generate
singlet oxygen to degrade contaminants in water, disinfection and
other uses are not practical for wastewater treatment due to
degradation of dyes by singlet oxygen over time (i.e.,
photobleaching) and at elevated concentrations.
[0020] Another common method of singlet oxygen generation is by
chemical reactions, where singlet oxygen is released as a
byproduct, including, for example, the Haber-Weiss reaction (see
eq. 4, below), the reaction between hydrogen peroxide and
hypochlorite, the decomposition of 9,10-diphenylanthracene
endoperoxide and the reaction between neutral and ionized forms of
organic peroxyacids. However, these methods cause the rapid
quenching of the singlet oxygen species by physical and chemical
pathways. Chemical quenching reactions occur when singlet oxygen is
consumed by a non-beneficial chemical reaction involving electron
transfer. Physical quenching reactions occur by radiative or
non-radiative relaxation of the excited state by physical contact
with its surroundings without electron transfer. In these methods,
excess hydrogen peroxide is a very effective quenching agent
resulting in little or no oxidative activity from singlet oxygen
generated in the presence of significant concentrations of hydrogen
peroxide. When hydrogen peroxide is present in significant
concentrations, as is the case for most commercially produced
peroxyacetic acid, singlet oxygen is rapidly quenched by hydrogen
peroxide, which reduces singlet oxygen concentration. Chlorine,
azide, certain tertiary amines and beta-carotene are other known
examples of singlet oxygen quenchers.
[0021] Peroxyacetic acid (i.e. AcOOH) is typically made by
commercial producers by an equilibrium reaction between
concentrated acetic acid (i.e. AcOH). The equilibrium reaction can
be catalyzed by a mineral acid such as sulfuric acid at a pH<1
and occurs over a time period of several hours to several days
depending on the concentration of hydrogen peroxide, acetic acid
and acid catalyst. There is typically a significant concentration
of residual hydrogen peroxide and acetic acid in peroxyacetic acid
made by the equilibrium reaction. For example, the [peroxyacetic
acid][H.sub.2O]/[acetic acid][H.sub.2O.sub.2] concentration ratios
are often between 1.8 and 2.5 for commercial grades having between
5 and 30 wt % peroxyacetic acid. Peroxyacetic acid solutions are
generally unstable at room temperature and pose a significant fire
hazard. Therefore peroxyacetic acid is typically produced on site
by the equilibrium process or shipped in vented containers from a
producer. Peroxyacetic acid may be distilled under reduced pressure
to obtain a pure form with low hydrogen peroxide residual, however,
distillation is generally not practical and can create a severe
explosion hazard.
[0022] Superoxide
[0023] Superoxide is the radical anion form of molecular oxygen
(.O.sub.2.sup.-) and is a mild reducing agent with a standard
oxidation potential commonly reported as -0.33 V in aqueous
environments. Superoxide can be produced in bulk as the anhydrous
potassium salt, KO.sub.2, which rapidly reacts with water or carbon
dioxide releasing molecular oxygen and potassium hydroxide or
potassium carbonate, respectively. Superoxide can also be produced
in situ by ultraviolet irradiation of oxygen containing solutions,
including seawater, by enzymatic processes and by electrochemical
reduction of oxygen. For large scale applications, superoxide is
typically supplied as a bulk chemical or generated in situ from
activated hydrogen peroxide reactions. Potassium superoxide is a
water-sensitive hazardous material and combustion aid, which may be
prohibitive barriers to its use in some locations. Also, potassium
superoxide must be fed into a treatment process as a solid feed,
which can be problematic due to water absorption, caking and
clogging of solid feeders.
SUMMARY OF THE INVENTION
[0024] The invention provides reactive oxygen species formulations
as well as methods for making and using such formulations.
[0025] The invention provides reactive oxygen formulations
comprising one or more parent oxidants, such as peroxides, or
peroxyacids, and one or more reactive oxygen species (ROS). The
formulations can optionally contain in addition one or more
reactive species other than ROS. In these formulations, the
reactive oxygen species and other reactive species, if present,
provide chemical reactivity, oxidative activity and/or
antimicrobial activity not provided otherwise by the parent
oxidant. The invention provides methods for making such formulation
and applications of such formulations. In specific embodiments, ROS
and other reactive species are generated in situ in the formulation
by an activation event, such as a change in pH to an activation pH,
a change in temperature (e.g., heating), irradiation with
electromagnetic radiation (e.g., UV or microwave, for example) or
by the addition of one or more precursors or a combination of
precursors. In an embodiment, peracid containing precursors are
activated by adjusting the pH of the formulation to be within an
activation pH range. In an embodiment. In an embodiment, additional
ROS or other reactive species are generated in a formulation after
a selected time delay.
[0026] Additional ROS or other reactive species can be generated in
formulations by a variety of methods including, but not limited to,
creation in-situ by secondary reactions of the singlet oxygen
precursor(s); creation in-situ by catalyst-activated reactions;
creation in-situ by ultraviolet light-activated reactions; and/or
by addition of reactive oxygen species. Combination of different
ROS in a formulation can function additively, synergistically or
react in a manner to provide entirely different ROS imparting new
characteristics to solutions. Formulations of the invention can be
subjected to two or more activation events to generate one or more
ROS and optionally to generated reactive species other than
ROS.
[0027] In an embodiment, reactive oxygen species formulations are
active for up to several hours, during which time the reactive
species therein are consumed and degrade to oxygen, water, and
simple, non-toxic and biodegradable organic acids and alcohols. In
an embodiment, reactive oxygen species formulations optionally
contain additives that can enhance a treatment, decontamination,
cleaning or separation process.
[0028] In an embodiment, reactive oxygen species formulations
include at least one peroxygen species (e.g., peroxy acid, and/or
hydrogen peroxide) which may be present at least in part in ionic
form, in various combinations with one or more of singlet oxygen,
superoxide, or peroxyl radicals. In an embodiment, certain
formulations are formulated to create additional reactive oxygen
species by reaction between singlet oxygen and superoxide and other
radical species produced as decomposition byproducts of at least
one peroxy acid in combination with singlet oxygen and/or
superoxide.
[0029] The presence of ROS or other reactive species in the
formulations herein may in some cases be directly detected and it
may be possible to determine the concentrations of certain reactive
species, e.g., using spectroscopic methods. However, in
formulations herein the presence of reactive species may only be
indirectly demonstrated by measurement of changing properties of
the formulation, e.g., oxidative-reductive potential (ORP)
measurements or pH change, by changes in concentration of
precursors (e.g., rate of peroxyacetic acid concentration decline)
or by changes in reactivity of the formulation, e. g., the rate of
oxidation of dyes (bleaching) rate or the rate or occurrence of
oxidation of certain species, e.g., polysaccharide breakdown.
[0030] In specific embodiments, reactive oxygen species
formulations of this invention include those having ORP of 550 mV
vs SHE or higher. In specific embodiments, reactive oxygen species
formulations of this invention include those having ORP of 600 mV
vs SHE or higher. In specific embodiments, reactive oxygen species
formulations of this invention include those having ORP of 650 mV
vs SHE or higher and are improved for use as antimicrobials. In
specific embodiments, reactive oxygen species formulations of this
invention include those having ORP of 700 mV vs SHE or higher. In
specific embodiments, reactive oxygen species formulations of this
invention include those having ORP of 800 mV vs SHE or higher. In
specific embodiments, reactive oxygen species formulations of this
invention include those having ORP of 900 mV vs SHE or higher. In
specific embodiments, reactive oxygen species formulations of this
invention include those having ORP of 650 mV vs SHE or higher which
is retained for 4 hours or longer (as measured in ORP measurements
described herein) which are improved for use as antimicrobials. In
specific embodiments, reactive oxygen species formulations of this
invention include those having ORP of 700 mV vs SHE or higher which
is retained for 4 hours or longer (as measured in ORP measurements
described herein). In specific embodiments, reactive oxygen species
formulations of this invention include those having ORP of 650 mV
vs SHE or higher which is retained for 10 hours or longer and are
improved for use as antimicrobials. In specific embodiments,
reactive oxygen species formulations of this invention include
those having ORP of 700 mV vs SHE or higher which is retained for
10 hours or longer. In specific embodiments, reactive oxygen
species formulations of this invention include those having ORP of
650 mV vs SHE or higher which is retained for 20 hours or longer.
In specific embodiments, reactive oxygen species formulations of
this invention include those having pH of 6-8, and ORP of 650 mV vs
SHE or higher which is retained for 10 hours or longer. In specific
embodiments, reactive oxygen species formulations of this invention
include those having pH 6-8 and ORP of 650 mV vs SHE or higher
which is retained for 20 hours or longer. In specific embodiments,
reactive oxygen species formulations of this invention include
those having ORP of 700 mV vs SHE or higher which is retained for
20 hours or longer. In specific embodiments, reactive oxygen
species formulations of this invention include those having pH of
6-8, and ORP of 700 mV vs SHE or higher which is retained for 10
hours or longer. In specific embodiments, reactive oxygen species
formulations of this invention include those having pH 6-8 and ORP
of 700 mV vs SHE or higher which is retained for 20 hours or
longer.
[0031] In specific embodiments, the formulations are prepared and
used as liquid formulations. In related embodiments, the
formulations are in the form of an ice, foam, emulsion,
microemulsion or an aerosol as desired for a selected oxidation
application and for a selected method of dispensing or applying the
formulation. The formulations are typically prepared in aqueous
solution and may contain one or more co-solvents. The formulations
optionally comprise one or more additives or stabilizers as defined
herein below. The formulations can have a selected pH (or range of
pH), selected relative concentrations or molar or weight ratios of
components (or range of such ratios), and/or selected ionic
strength. Formulations are described herein as generated to form
ROS and optional other reactive species, but it will be appreciated
that the formulations contain reactive species, some of which may
be very reactive and short-lived, thus the concentrations of
formulation components and other formulation characteristics (e.g.,
pH) will change after the formulation is generated or activated. It
will also be appreciated, particularly in view of examples herein,
that initially generated reactive species in a formulation may
react to generate secondary reactive species, such that the
components and concentrations thereof in the compositions and other
characteristics of the formulations will change with time as well
as with conditions such as temperature. In an embodiment, the ROS
and other reactive species are generated in the formulations by one
or more activation events (activations). Multiple activation events
may be separated in time. Activation events include any physical or
chemical change that generates the desired reactive species and can
include, for example, the mixing of one or more precursors, the
adjustment of pH to an activation pH, adjustment of relative
concentrations of one or more precursors, addition or presence of a
catalyst or other activating material, electromagnetic irradiation
(e.g., UV radiation with e.g., exposure for a selected time), a
change in temperature, ultrasonic treatment or the like. Secondary
reactive species may simply be generated with the passage of
sufficient time to allow for the reaction of primary reactive
species to generate the secondary reactive species. In certain
embodiments, ROS or ROS precursors are generated
electrochemically.
[0032] In an embodiment, the reactive oxygen formulations comprise
the ROS, singlet oxygen. In another embodiment, the reactive oxygen
formulations comprise the ROS, superoxide. In another embodiment
the reactive oxygen formulations comprise a combination of
superoxide and singlet oxygen. In other embodiments, formulations
herein can comprise one or more of singlet oxygen, superoxide,
hydroxyl radical, hydroperoxy radical, or hydrogen trioxide. In
additional embodiments, formulation herein can comprise one or more
ROS in combination with other reactive species which can include,
for example, one or more organic radicals, such as organo-peroxyl
radicals, acyl radicals, hydrocarbon radicals (e.g., methyl or
other alkyl radicals), or carboxyl radicals. In additional
embodiments, formulation herein can comprise one or more ROS in
combination with other reactive species, such as radicals or
trioxyorganoacids, such as trioxyacetic acid.
[0033] In an embodiment, reactive oxygen formulations comprise a
parent oxidant that is peroxyacid, such as peroxyacetic acid, or a
mixture thereof with hydrogen peroxide and the ROS, singlet oxygen.
In an embodiment, single oxygen is generated by reaction of parent
oxygen species, particular when the pH of the precursor formulation
is within the activation pH range. In a preferred embodiment,
minimal or no hydrogen peroxide is present in the formulation to
avoid quenching of singlet oxygen. In another, embodiment, a
selected amount of hydrogen peroxide is present in the formulation
to control activity of singlet oxygen. A preferred method of
generating peroxyacetic acids with minimal hydrogen peroxide is by
a non-equilibrium chemical reaction between an acetyl donor
molecule and alkaline hydrogen peroxide, as described herein.
Formulations containing peroxyacid in combination with singlet
oxygen is found to be more active than peroxy acid. Such
formulations can function as biocides and are capable of oxidizing
unsaturated hydrocarbons, certain aromatic hydrocarbons, dyes and
can breakdown polysaccharides, such as guar gum. These formulations
are also reactive with polyamines, nitrile rubber, and EDTA, but
are compatible with salinity, scaling minerals, saturated
hydrocarbons, phosphonic acids, several polymers, stainless steel
and aluminum.
[0034] In an embodiment, the invention provides a method for
generating a reactive oxygen species formulation comprising (1)
generating an alkaline hydrogen peroxide solution from the
combination of an alkali and a hydrogen peroxide concentrate; (2)
mixing the alkaline hydrogen peroxide solution with an acyl or
acetyl donor such that a peracid concentrate is produced, wherein
the peracid concentrate has minimal hydrogen peroxide residual; and
(3) adjusting the peracid pH level to the activated pH range for
generating the reactive oxygen species. The reactive oxygen species
formulation can be a singlet oxygen precursor formulation. In an
embodiment, the hydrogen peroxide solution is generated using a
molar ratio of H.sub.2O.sub.2 to alkali in the range of 1:1.2 to
1:2.5. The molar ratio of H.sub.2O.sub.2 to alkali can be 1:1.2 to
1:1.4, 1.4 to 1:2.0 or 1:2.0 to 1:2.5. In an embodiment, the
peracid concentrate is produced by mixing the alkaline hydrogen
peroxide solution with the acyl or acetyl donor such that the molar
ratio of hydrogen peroxide to acyl or acetyl donor ranges
from1:1.25 to 1:4. The molar ratio of hydrogen peroxide to acyl or
acetyl donor can be 1:1.25 to 1:1.5, 1:1.5 to 1:2, or 1:2 to 1:4.
In an embodiment, the activated pH range is in the range of pH 6.5
to 12.5. The activated pH range can be 6.5 to 9.5 or 9.5 to12.5. In
an embodiment, the method further comprises entraining byproducts
of the reaction between the alkaline hydrogen peroxide solution and
the acyl or acetyl donor. In an embodiment, the method further
comprises diluting the peracid concentrate. In an embodiment, the
method further comprises mixing the peracid solution with an
additives concentrate. In an embodiment, the method comprises
storing the alkaline hydrogen peroxide in a holding tank for
immediate or future use. In an embodiment, mixing the alkaline
hydrogen peroxide solution with an acyl or acetyl donor produces a
concentrated peracid solution.
[0035] In an embodiment, the invention provides a method for
generating a reactive oxygen species formulation wherein an
alkaline hydrogen peroxide concentrate is electrochemically
generating, the electrochemically generated alkaline hydrogen
peroxide concentrate is combined with an acyl or acetyl donor to
produce a peracid concentrate, wherein the peracid concentrate has
minimal hydrogen peroxide residual and the peracid solution is
combined with an acid concentrate to produce the reactive oxygen
species formulation having a pH level in the activated pH range. In
an embodiment, the electrochemically generated alkaline hydrogen
peroxide concentrate has a pH in the range of 12.0 to 13.0, and a
percent weight of hydrogen peroxide in the range of 0.1 to 3 wt %.
In an embodiment, the acid concentrate is co-generated during
electrochemically generating the alkaline hydrogen peroxide
concentrate. The co-generated acid concentrate can have 0.1 wt % to
20 wt % acid. In an embodiment, the peracid concentrate is produced
by mixing the electrochemically generated alkaline hydrogen
peroxide solution with the acyl or acetyl donor such that the molar
ratio of hydrogen peroxide to acyl or acetyl donor is in the range
of1:1.25 to 1:4. The molar ratio of hydrogen peroxide to acyl or
acetyl donor can be 1:1.25 to 1:1.5, 1:1.5 to 1:2, or 1:2 to 1:4.
In an embodiment, the activated pH range is in the range of pH 6.5
to 12.5. The activated pH range can be 6.5 to 9.5 or 9.5 to 12.5.
In an embodiment, the method further comprises entraining
byproducts of the reaction between the alkaline hydrogen peroxide
solution and the acyl or acetyl donor. In an embodiment, the method
further comprises diluting the peracid concentrate. In an
embodiment, the method further comprises mixing the peracid
solution with an additives concentrate. In an embodiment, the
method comprises storing the alkaline hydrogen peroxide in a
holding tank for immediate or future use. In an embodiment, mixing
the alkaline hydrogen peroxide solution with an acyl or acetyl
donor produces a concentrated peracid solution.
[0036] In an embodiment, the invention provides a method for
generating a superoxide reactive oxygen species formulation
comprising electrochemically co-generating a solution containing
hydrogen peroxide and superoxide. In an embodiment, the formulation
containing co-generated hydrogen peroxide and superoxide has a pH
of 8-13. In an embodiment, the molar ratio of superoxide to
hydrogen peroxide co-generated ranges from 0.01:1 to 10:1. In an
embodiment, the pH of the superoxide solution is adjusted by
addition of an acid concentrate. In an embodiment, the acid
concentrate is co-generated during the step of electrochemically
generating the superoxide solution. In an embodiment, the
superoxide solution is combined with an additives concentrate. In
an embodiment, the superoxide solution is diluted. More
specifically, the superoxide solution is diluted to a near point of
use concentration. In an embodiment, co-generation of hydrogen
peroxide and superoxide produces at least one radical species which
can among others be a hydroperoxyl radical and/or a hydroxyl
radical.
[0037] In related embodiments, the methods for generating reactive
oxygen formulations further comprise further activating the
reactive oxygen species using activation chosen from the group a
Fenton or Fenton-like catalyst, ultrasound, ultraviolet radiation
and thermal activation. More specifically activation produces
radical species, which can be the hydroxyl radical.
[0038] In an embodiment, a reactive oxygen formulation produced by
the methods herein is distributed to its point of use. The form in
which the reactive oxygen formulation is distributed can as a
liquid, an ice, a foam, an emulsion, a microemulsion or an aerosol.
The invention also provides reactive oxygen formulations for point
of use applications which are appropriately formulated for
application by injection, flooding, spraying, and/or
circulation.
[0039] In specific embodiments, in the methods herein the reactive
oxygen species is singlet oxygen. The invention also provides
formulations containing reactive oxygen species, particularly those
prepared by the methods of the invention. In specific embodiments,
the reactive oxygen species formulations are singlet oxygen
formulations. Such formulations can be concentrated or can be
diluted. Diluted formulation can be prepared by addition of
water.
[0040] In specific embodiments, the invention provides a reactive
oxygen species precursor comprising a peracid concentrate
comprising a mixture of alkaline hydrogen peroxide and an acyl or
acetyl donor. The reactive oxygen species precursor can be a
diluted singlet oxygen precursor. More specifically, the diluted
singlet oxygen precursor has a pH in the range 6.5 to 12.5, in the
range 6.5 to 9.5 or in the range 9.5 to 12.5. The reactive oxygen
species precursor can be a concentrated singlet oxygen precursor.
More specifically, the concentrated singlet oxygen precursor has a
pH in the range 6.5 to 12.5, in the range 6.5 to 9.5 or in the
range 9.5 to 12.5.
[0041] In an embodiment, the invention provides a peracid
formulation capable of generating singlet oxygen, particularly
where the singlet oxygen is generated by the reaction of alkaline
hydrogen peroxide and an acyl or acetyl donor. The invention also
provides a method for making such peracid formulations. Preferably
the peracid formulation has minimal hydrogen peroxide residual to
minimize quenching of the singlet oxygen. In an embodiment, the
peracid formulation has a pH in the activated pH range. In a
specific embodiment, in the peracid formulation, the ratio of
alkaline hydrogen peroxide to acyl or acetyl donor reactive groups
is in the range 1:1.25 to 1:2 to 1:4. More specifically, the ratio
of alkaline hydrogen peroxide to acyl or acetyl donor reactive
groups is 1:1.25 to 1:1.5, 1:1.5 to 1:2, or 1:2 to 1:4. The peracid
formulation can have pH in the range 6.5 to 12.5, 6.5 to 9.5 or 9.5
to 12.5. In a specific embodiment, the peracid formulation is
further reacted with an acid concentration resulting in both
peracetic acid and paracetic acid anion, wherein the reaction of
the peracid formulation and acid concentrate comprises the
reaction:
AcOOH+AcOO.sup.-.fwdarw..sup.1O.sub.2+AcOH+AcO.sup.-.
[0042] Peracid formulation of the invention can be distributed in
any suitable form and can be distributed in the form of a liquid,
an ice, a foam, an emulsion, a microemulsion or an aerosol. The
peracid formulations of the invention can be applied to a point of
use by an application chosen from injection, flooding, spraying,
and circulation. The peracid formulations of the invention can be
used for clean-in-place applications in food, dairy, beverage and
biopharma; hard surface cleaning; decontamination; remediation of
soil and groundwater; cleaning of membrane filtration systems;
flushing of well casings and water distribution pipes; and in-situ
chemical oxidation, among others.
[0043] In an embodiment, the invention provides an
electrochemically generated, reactive oxygen species solution
comprising superoxide formulation co-generated with a hydrogen
peroxide solution. More specifically, the superoxide/hydrogen
peroxide solutions are generated such that the ratio of superoxide
to hydrogen peroxide is 0.01:1 to 10:1. More specifically, the
superoxide to hydrogen peroxide solutions are generated such that
the ratio of superoxide to hydrogen peroxide ranges from 0.01:1 to
0.5:1, from 0.5:1 to 1.5:1, from 1.5:1 to 3:1, from 3:1 to 5:1, or
from 5:1 to 10:1. In an embodiment, the electrochemically
generated, reactive oxygen species solution has initial pH of 8-13,
or 8-9, or 9-12, or12-13.
[0044] In an embodiment, the invention provides a formulation
containing an electrochemically generated hydroperoxyl radical. In
an embodiment, the radical is created by the reaction of
electrochemically generated superoxide formulation co-generated
with hydrogen peroxide formulation by the reaction:
O.sub.2..sup.-+H.sub.2O.sub.2.sup.1O.sub.2+.OH+OH.sup.-.
[0045] The invention provides methods of oxidation which employ
reactive oxygen species formulations as described herein. The
oxidation method includes application of one or more selected
reactive oxygen species formulations to an environment, a substrate
in an environment or to a substrate that is to be subjected to
oxidization. The term substrate is used herein broadly to refer to
a place, a material, a chemical and/or a biological species that is
to be subject to at least partial oxidation. In an embodiment, the
place or substrate are containers, tanks, pools, equipment or pipes
that are subjected to oxidative cleaning. In an embodiment, the
environment is water and the substrate is one or more organic or
inorganic chemical species that are to be oxidized and/or the
substrate is microorganism that are to be killed. In an embodiment,
the environment or substrate is a soil sample or a contaminated
soil environment from which contaminants are to be removed at least
in part by oxidation. In an embodiment, the environment or
substrate is water containing undesirable chemical or biological
species that are to be at least in part removed by oxidative
treatment. In an embodiment, water to be treated is waste water,
greywater, raw water, ground water, or a tailing pond. In an
embodiment, the substrate is paper, pulp or textiles and the
formulations function for bleaching of the substrate. In an
embodiment, the environment or substrate is contaminated with
higher than desirable levels of microorganisms wherein the
environment or substrate is to be disinfected.
[0046] In an embodiment, the invention provides a method for
treating water
[0047] In an embodiment, the invention provides a method for
treating waste water employing formulations of the invention
containing reactive oxygen species. In a specific embodiment, the
method includes electrochemically co-generating a cathode output
solution comprising superoxide and hydrogen peroxide; mixing the
cathode output solution into a waste water source; and adjusting
the pH of the mixture. In an embodiment, pH is adjusted after the
step of mixing the cathode output solution into the waste water
source.
[0048] In applications of the reactive oxygen species formulations
of this invention, the formulation is brought into contact with the
environment and/or substrate to be oxidized or treated. The
environment and/or substrate can be contacted with an activated
liquid formulation containing reactive oxygen species.
Alternatively, the environment and/or substrate can be contacted
with a liquid precursor formulation that will generate reactive
oxgen species on activation and the formulation is activated as or
after it comes into contact with the environment or substrate. For
example, the environment or substrate may itself provide for
activation, such as a pH adjustment to the activation pH. One or
more additional steps of activation to form additional reactive
species can occur after the formulation or precursor formulation
contact the environment and/or substrate. For example, steps of pH
adjustment may occur after contact. Contact with the environment or
substrate may be controlled addition of a selected volume or
concentration of formulation or its precursor to the environment or
in contact with the substrate. Alternatively, contact can occur by
addition of the substrate to the formulation or a precursor
thereof.
[0049] Other embodiments of the invention will be become apparent
on review of the following drawings and detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0050] FIG. 1 shows one exemplary system 100 for generation of a
diluted reactive oxygen species 116 where in one embodiment bulk
chemical feedstock constituents are used.
[0051] FIG. 2 shows an exemplary method 200 for generating reactive
oxygen species output 116 using system 100 of FIG. 1.
[0052] FIG. 3 shows one exemplary system 300 for generation of a
concentrated reactive oxygen species output 314 using bulk chemical
precursor constituents, in one embodiment.
[0053] FIG. 4 shows an exemplary method 400 for generating reactive
oxygen species output 314 using system 300 of FIG. 3.
[0054] FIG. 5 shows an exemplary system 500 for generating
chemicals using an electrochemical reactor 514 to produce a diluted
reactive oxygen species output.
[0055] FIGS. 6A/6B depict a cross-sectional view of the general
configuration and components of an exemplary electrochemical
reactor 600 for use in system 500 of FIG. 5. More details of this
and similar configurations and electrochemical reactors are found
in published International application WO2012166997 which is
incorporated by reference herein in its entirety.
[0056] FIG. 7 depicts an embodiment of a reactor system 700 that
has a reactor system fluid process flow, also known as a flow
pathway, that enables gas recirculation within reactor system
700.
[0057] FIG. 8 shows an exemplary method 800 for generating a
diluted reactive oxygen species output 522 using system 500 of FIG.
5.
[0058] FIG. 9 shows an exemplary system 900 for generating
chemicals using an electrochemical reactor 914 and mixing the
reactor's 914 outputs together and optionally with other materials
to produce a concentrated reactive oxygen species output 922.
[0059] FIG. 10 shows an exemplary method 1000 for generating a
concentrated reactive oxygen species output 922 using system 900 of
FIG. 9.
[0060] FIG. 11 shows an exemplary system 1100 for generating
chemicals using an electrochemical reactor 1114 to produce a
superoxide reactive oxygen species output.
[0061] FIG. 12 shows an exemplary method 1200 for generating a
concentrated superoxide reactive oxygen species output 1122 using
system 1100 of FIG. 11, in one embodiment.
[0062] FIG. 13 shows exemplary results of the percent color removal
of 50 mg/L MB (Methylene blue) solutions observed over time
starting with different initial peroxyacetic acid
concentrations.
[0063] FIG. 14A shows graph 1400 that shows the full spectra of
samples diluted to 100+/-4 mg/L hydrogen peroxide and adjusted to
pH 12.00+/-0.04.
[0064] FIG. 14B shows the spectra of FIG. 14A with hydrogen
peroxide absorbance subtracted off.
[0065] FIGS. 15A/B show graphs 1500, 1550 that show the evolution
of the UV absorbance spectrum over five hours for the co-generated
hydrogen peroxide and superoxide output produced at 8 amps in
Example 11 diluted to 100+/-4 mg/L hydrogen peroxide, adjusted to
pH 12.00+/-0.04 and analyzed over time.
[0066] FIGS. 16A/B show graphs 1600, 1650 that shows the evolution
of the UV absorbance spectrum over five hours for the co-generated
hydrogen peroxide and superoxide output produced at 8 amps in
Example 11 diluted to 100+/-8 mg/L hydrogen peroxide, adjusted to
pH 11.04+/-0.04 and analyzed over time.
[0067] FIG. 17 shows an exemplary system and flow process for
electrochemically generating a CIP cleanser, in one embodiment.
[0068] FIG. 18 shows one exemplary system used in Example 17 to
show an exemplar of producing a superoxide precursor formulation
using an electrochemical generator used in a water treatment
application, in one embodiment.
[0069] FIG. 19 is a graph illustrating oxidative-reductive
potential (ORP, mV vs SHE, see Example 18) as a function of PH for
several formulations of Example 18. Solid Squares=28.5 mM
PAA+approximately 129 mM Superoxide; Open Squares=28.5 mM PAA
[0070] Solid Circles=28.5 mM PAA+29.4 mM HP; Open Diamonds=29.4 mM
HP+approximately 133 mM Superoxide.
[0071] FIG. 20 is a graph illustrating the effect on
oxidative-reductive potential (ORP, mV vs SHE, see Example 18) for
a S-PM solution (containing PAA and superoxide) diluted in
distilled water (solid squares) or tap water (solid diamonds).
[0072] FIG. 21 is a graph illustrating the change over time of
oxidative-reductive potential (ORP, mV vs SHE, see Example 18) for
solution 3 at pH 7 (solid triangles) or 9 (open circles).
[0073] FIG. 22 is a graph illustrating the effect on
oxidative-reductive potential (ORP, mV vs SHE, see Example 18) for
solution 3 of Example 18.
[0074] FIGS. 23A and B are graphs illustrating the change in
oxidative-reductive potential (ORP, mV vs SHE, see Example 18) as a
function of time in various PAA+superoxide containing formulations
as a function of the molar ratio of PAA to superoxide. FIG. 23A
extends over the period of 500 minutes. FIG. 23B extends over the
period of over 40 hours.
[0075] FIGS. 24A and B are graphs illustrating the rate of
methylene blue oxidation by certain reactive oxygen species
formulations of this invention. FIG. 24A compares the rate of
methylene blue oxidation for a PM formulation (solid circles) to a
S-PM formulation (solid squares) and FIG. 24B compares the rate of
methylene blue oxidation for the S-PM formulation (solid squares)
to an analogous S-PM-B formulation (solid triangles).
[0076] FIG. 25 is a flow chart illustrating an exemplary water
treatment process (2500) employing reactive oxygen species
formulation of this invention in one or more process steps.
DETAILED DESCRIPTION
[0077] Reactive Oxygen Species from Bulk Chemicals:
[0078] In the following embodiments, systems and methods are shown
to generate reactive oxygen species. More specifically, reactive
oxygen species can be formed in situ from a mixture of bulk
chemical feedstocks in close proximity to various substrates that
are to be treated. The term substrate is used very broadly herein
for materials, compounds, atoms or ions (organic or inorganic) to
be oxidized or microorganisms to be denatured or killed.
[0079] In the following embodiments, exemplary systems and methods
are shown, for example, that describe alternatives to the use of
hydroxyl radical oxidation chemistry that are more compatible with
saline or highly contaminated waters and that minimize chlorate and
bromate formation by having lower standard oxidation potentials
than chloride, bromide or their hypohalite forms while possessing
high chemical reactivity toward a variety of substrates.
[0080] In another embodiment, an exemplary system and method is
shown for enabling the production of larger quantities and higher
concentrations of singlet oxygen from chemical precursor
formulations not containing singlet oxygen quenching agents.
[0081] In yet another embodiment, an exemplary method and system is
shown for singlet oxygen production to occur for extended periods
of time while the amount and rate of singlet oxygen evolved can be
controlled by the more readily measurable precursor formulation and
concentration.
[0082] FIG. 1 shows one exemplary system 100 for generation of a
diluted reactive oxygen species 116 using bulk chemical feedstock
constituents, in an embodiment. In an embodiment, diluted reactive
oxygen species output 116 is used in applications where a fluid is
conveyed to a surface or material including clean in place, hard
surface cleaning, decontamination, remediation and in situ chemical
oxidation applications. System 100 includes hydrogen peroxide
(H.sub.2O.sub.2 ) concentrate 102, alkali concentrate 104, acetyl
donor 106, makeup water 108, additives concentrate 110, acid
concentrate 112, peracid holding tank 114, reactive oxygen species
output 116, pumps 118, and mixing chambers 120. In one embodiment,
reactive oxygen species output 116 is diluted singlet oxygen
precursor solution. The system of FIG. 1 is illustrated for use of
an acetyl donor, as discussed herein more generally acyl donors
(both oxygen-acyl and nitrogen-acyl donors) can be employed in
preparation of formulations herein. Choice of acyl donor or mixture
of donors employed determines the peracid or mixture of peracids in
a given formulation.
[0083] Hydrogen Peroxide Concentrate 102 is typically an aqueous
hydrogen peroxide solution, for example. However, in alternative
embodiments, hydrogen peroxide concentrate 102 may include other
chemical forms of peroxide chosen from the group including: calcium
peroxide, potassium peroxide, sodium peroxide, lithium peroxide,
percarbonates, and perborates.
[0084] In one embodiment, alkali concentrate 104 is an aqueous
sodium hydroxide solution. In an alternative embodiment, Alkali
concentrate 104 is potassium hydroxide. Acyl or acetyl donor 106 or
mixture of donors may be in liquid or solid form, or dissolved in a
solvent when reacted with a solution of hydrogen peroxide.
[0085] Acid concentrate 112, for example, includes at least one pH
buffer chosen from the group including: weak acid electrolytes
including acetate, citrate, propionate, phosphate and sulfate.
[0086] In an embodiment, reactive oxygen species output 116 is a
peroxyacetic acid in the absence of hydrogen peroxide and includes
at least one chemical precursor species capable of releasing
singlet oxygen. In alternative embodiments, reactive oxygen species
output 116 includes two chemical precursor species may be used to
release singlet oxygen. In yet another embodiment, reactive oxygen
species output 116 includes more than two chemical precursor
species to release singlet oxygen.
[0087] FIG. 2 shows an exemplary method 200 for generating reactive
oxygen species output 116 using system 100 of FIG. 1. FIG. 2 is
illustrated for use of an acetyl donor, but as discussed more
generically an acyl donor can be employed. In an embodiment, the
reactive oxygen species output 116 generated by method 200 is
singlet oxygen. In step 202, an alkaline hydrogen peroxide anion
solution 122 is created by mixing H.sub.2O.sub.2 concentrate 102
with alkali concentrate 104 in mixing tank 120(1). For example,
molar ratios of H.sub.2O.sub.2 concentrate 102 to alkali in alklai
concentrate 104 may range from 1:1.2 to 1:2.5. In an embodiment,
the preferred molar ratio range is 1:1.4 to 1:2, for example. The
preferred molar ratio range is determined by the preferred pH range
of the alkaline hydrogen peroxide solution of pH 12.0 to 12.6,
which promotes the reaction between hydrogen peroxide and the
acetyl or acyl donor. In one embodiment, hydrogen peroxide
concentrate 102 is a weak acid with a pKa of 11.6 and therefore its
combination with alkali converts it in an acid-base equilibrium to
the hydrogen peroxide anion form as in Equation 1 below:
HOOH+OH.sup.-||HOO.sup.-+H.sub.2O [1]
In some embodiments, raising the pH of a hydrogen peroxide solution
enough to put a significant proportion of hydrogen peroxide into
the anion form requires an excess of alkali 104 over hydrogen
peroxide 102. In one embodiment, the molar excess of alkali 104
over H.sub.2O.sub.2 102 may range from 20% to 100% greater alkali
104. For example, a preferred molar excess range is 20% to 40%
greater alkali 104. The equilibrium reaction in Equation 1 consumes
alkali in a 1:1 molar ratio, therefore an excess of alkali over
hydrogen peroxide is required to raise the pH of the alkaline
hydrogen peroxide solution to the preferred pH range.
[0088] In step 204, the resulting alkaline hydrogen peroxide 122 is
combined with an acyl or acetyl donor 106 in mixing tank 120(2) to
create a resulting alkaline peracid concentrate 122'. In one
embodiment, alkaline peracid concentrate 122' may be a peroxyacetic
acid solution. In one embodiment, the acyl or acetyl donor is added
in proportion to the hydrogen peroxide. In an alternative
embodiment, the molar ratio of H.sub.2O.sub.2 122 to acyl or acetyl
donor 106 reactive group equivalents can range from 1:1.25 to 1:4.
For example, a preferred molar ratio range is 1:1.5 to 1:2. If the
ratio is too low a high hydrogen peroxide residual will remain in
the peracid concentrate where it will significantly quench singlet
oxygen. If the ratio is higher than needed to achieve a low
hydrogen peroxide residual that does not significantly quench
singlet oxygen then excess acyl or acetyl donor remains unused. In
one embodiment, the acyl or acetyl donor is an oxygen-acyl or
oxygen-acetyl donor shown in Equation 2a below:
HOO.sub.-+AcOR.fwdarw.AcOO.sub.-+ROH [2a]
Where Ac is acyl [--C(O)R'] or acetyl [--C(O)CH.sub.3] and R and R'
are hydrocarbon-based substituents and more specifically are alkyl
or aryl groups. In an alternative embodiment, the acyl or acetyl
donor is a nitrogen-acyl or nitrogen-acetyl donor as shown in
Equation 2b below:
HOO_+AcNR.sub.2.fwdarw.AcOO.sub.-+RNH [2b]
Where Ac is acyl [--C(O)R'] or acetyl [--C(O)CH.sub.3] and R and R'
are hydrocarbon-based substituents and more specifically are alkyl
or aryl groups.
[0089] In Equations 2a/2b above, the reaction between an acyl or
acetyl donor 106 and hydrogen peroxide 122 occurs at alkaline pH by
nucleophilic attack of the acyl carbonyl carbon atom by the
hydrogen peroxide anion, which displaces the donor molecule
fragment as an alcohol or amine in a manner analogous to
saponification. In some embodiments, the non-equilibrium reactions
generalized in Equations 2a/2b are conducted between pH 10 and pH
13.
[0090] The use of non-equilibrium reaction in Equations 2a/2b
produces alkaline peracid concentrate 122' with concentrations of
less than approximately 10 wt % peroxyacetic acid and/or other
organic peracids that are produced efficiently and rapidly.
Alkaline peracid concentrate can be produced with concentrations of
less than approximately 5 wt % peroxyacetic acid and/or other
organic peracids. Using the non-equilibrium reaction allows the
hydrogen peroxide residual to be minimized if necessary. Minimizing
the hydrogen peroxide residual, for example, significantly
increases the concentration of the singlet oxygen available to
oxidize target substrates. In one embodiment, for example, the
[peroxyacetic acid][water]/[hydrogen peroxide] concentration ratios
are from 10, 100, or 1000 depending on the ratio of hydrogen
peroxide to acyl or acetyl donor ratio in Equations 2a/2b. Hydrogen
peroxide is preferably minimized in alkaline peracid concentrate.
Hydrogen peroxide is preferably less than 3% the mass concentration
of peroxyacetic acid or other peracid, and more preferably less
than 0.5% the mass concentration of peroxyacetic acid or other
peracid. Concentrates having only trace or no detectible levels of
hydrogen peroxide are preferred. In one embodiment, at least one
molar equivalent of acyl or acetyl donor 106 reactive groups is
added for each equivalent of hydrogen peroxide in alkaline hydrogen
peroxide anion solution 122 used in Equations 2a/2b to consume all
of the hydrogen peroxide. In alternative embodiments, excess acyl
or acetyl donor 106 reactive groups is necessary to minimize the
hydrogen peroxide residual due to the competing conversion of acyl
or acetyl donor 106 reactive groups to the corresponding carboxylic
acid by the alkali concentrate 104 used to raise the pH of the
H.sub.2O.sub.2 concentrate 102. In one embodiment, the molar excess
of acyl or acetyl donor 106 reactive groups over H.sub.2O.sub.2
solution 122 may range from 25% to 300% greater acyl or acetyl
donor 106. For example, a preferred molar excess range is 50% to
100% greater acyl or acetyl donor 106 reactive groups.
[0091] In optional step 206, as indicated by the dashed lines,
method 200 entrains byproducts 124 produced by the reactions of
Equations 2a/2b. For example, byproducts 124 are entrained in
solution with the alkaline peracid concentrate 204. In one
embodiment, byproducts 124 are useful as co-solvents, pH buffers,
chelating agents or stabilizers and carbon substrates for microbial
processes after a chemical oxidation process. For example, the
byproduct 124 of acetyl donors 106 of monacetin, diacetin and
triacetin is glycerol, a potential co-solvent and favorable carbon
source for microbes. In another embodiment, byproduct 124 of acetyl
donor 106 of TAED, diacetylethylenediamine, acts as a chelating
agent for transition metal ions and potentially serves as a
peroxide stabilizer. In yet another embodiment, byproduct 124 is
the carboxylic acid produced after alkaline peracid concentrate
122' reacts with a material or decomposes. Alternatively, acetic
acid, a byproduct 124 of peroxyacetic acid, serves as a co-solvent,
a pH buffer, a chelating agent, and a biological substrate.
[0092] In step 208, method 200 dilutes the resulting alkaline
peracid concentrate 122' to nearly point of use concentration by
adding makeup water 108. The amount of dilution is dependent on the
concentration of alkaline peracid concentrate 122' and the desired
point of use concentration of reactive oxygen species output 116.
For example, the alkaline peracid concentration 122' may be 19 wt %
to 21 wt % using 50 wt % hydrogen peroxide concentrate 102, 50 wt %
sodium hydroxide as the alkali concentrate 104 and triacetin as the
acetyl donor 106. In another example, the alkaline peroxyacetic
acid concentration can be 17 wt % to 19 wt % using 30 wt % hydrogen
peroxide concentrate 102, 50 wt % sodium hydroxide as the alkali
concentrate 104 and triacetin as the acetyl donor 106.
[0093] In step 212, method 200 then stores the resulting
combination in peracid holding tank 114. In optional step 210, as
indicated by a dashed outline, method 200 adds additives
concentrate 110 to the resulting diluted peracid from step 208, and
then stores the combination in peracid holding tank 114 in step
212. In one embodiment, the alkaline peracid stored in peracid
holding tank 114 contains all constituents for formulation of
reactive oxygen species output 116 except for the final activating
pH adjustment. This allows for the diluted alkaline peracid 122''
to have a modest lifetime prior to use and be stored in peracid
holding tank 114 for several minutes to a few hours, depending on
the concentration determined in step 208, and any additives added
in step 210. In an alternative embodiment, optional step 210 may be
performed by adding an additive concentration 110 of peroxide
stabilizer before, during, or after combination of the acyl or
acetyl donor 106 in step 204.
[0094] In step 214, method 200 adjusts the diluted peracid's 122''
pH to the activated pH level for producing reactive oxygen species
output 116 by adding acid concentrate 112 and mixing in mixing
chamber 120(3). The resulting reactive oxygen species output 116 is
then distributed to its point of use in liquid form. The reactive
oxygen species output 116 may then be used in the form of a liquid,
an ice, a foam, an emulsion, a micro-emulsion or an aerosol applied
by means such as injection, flooding, spraying, circulation or any
other means of conveying a fluid. In one embodiment, the diluted
peracid's 122'' pH does not require the addition of acid
concentrate 112 and is ready for immediate distribution 214 to its
point of use.
[0095] In one embodiment, during step 214, an acid concentration
112 is combined with diluted peracid 122'' such that there is a
population of both peracetic acid and peracetic acid anion which
react together to generate singlet oxygen according to Equation 3
below:
AcOOH+AcOO.sup.-.fwdarw..sup.1O.sub.2+AcOH+AcO.sup.- [3]
Wherein the reaction rate for Equation 3 above follows a second
order kinetics and is maximized when the ratio of the two forms of
peroxyacetic acid is equivalent at its pKa of 8.3. The evolution
and release of singlet oxygen occurs over time ranging from minutes
to several hours depending on the rate of reaction in Equation 3
above. In one embodiment, the evolution of singlet oxygen from
peroxyacetic acid, or other organic peracid having a similar pKa,
the pH is between 6 and 11 or between 6.5 and 9.5. In another
embodiment the evolution of singlet oxygen from peroxyacetic acid,
or other organic peracid having a similar pKa, may be substantially
retarded between about pH 9.5 and 12.5. For example, as pH becomes
more alkaline the peracetic acid anion dominates the composition
leaving very little peracetic acid to react with by the reaction in
Equation 3. Retardation of singlet oxygen production extends the
lifetime of the peroxyacetic acid or peracid solution and also
allows for singlet oxygen use at elevated pH relevant to certain
applications which use alkaline oxidants or cleansers up to pH 12
to 12.5.
[0096] In optional step 216, as shown by the dashed outline, method
200 further activates the reactive oxygen species output 116 by
means of a Fenton or Fenton-like catalyst, ultrasound, ultraviolet
radiation or thermal activation (not shown in FIG. 1) to produce
other reactive species.
[0097] FIG. 3 shows one exemplary system 300 for generation of a
concentrated reactive oxygen species output 314 using bulk chemical
precursor constituents, in one embodiment. FIG. 3 is illustrated
with use of an acetyl donor, but as discussed herein can more
generally use an acyl donor. In one embodiment, concentrated
reactive oxygen species output 314 is used in applications where a
concentrate is dosed into a liquid stream, including, but not
limited to water and wastewater treatment; cooling tower water
treatment and cooling tower system cleaning; desulfurization and
deodorization of gases; water treatment in forestry operations,
pulp and paper making processes; oil and gas produced water and
hydraulic fracturing flowback water treatment. System 300 includes
hydrogen peroxide (H.sub.2O.sub.2) concentrate 302, alkali
concentrate 304, acyl or acetyl donor 306, acid concentrate 308,
additives concentrate 310, alkaline hydrogen peroxide holding tank
312, reactive oxygen species output 314, pumps 316 and mixing
chambers 318. In one embodiment, reactive oxygen species output 316
is concentrated singlet oxygen precursor solution.
[0098] In one embodiment, alkali concentrate 304 is an aqueous
sodium hydroxide solution. In another embodiment, alkali
concentrate is an aqueous potassium hydroxide solution. Acyl or
acetyl donor 306 or mixture of donors may be in liquid or solid
form, or dissolved in a solvent when reacted with a solution of
hydrogen peroxide.
[0099] Acid concentrate 308, for example, includes at least one pH
buffer chosen from the group including: weak acid electrolytes
including acetate, citrate, propionate, phosphate and sulfate.
Additives concentrate 310, for example, includes at least one of
the following additives chosen from the group including: salts,
surfactants, co-solvents, stabilizers, and emulsifiers.
[0100] In an embodiment, reactive oxygen species output 314 is a
peroxyacetic acid in the absence of hydrogen peroxide and includes
at least one chemical precursor species capable of releasing
singlet oxygen. In alternative embodiments, reactive oxygen species
output 316 includes two chemical precursor species may be used to
release singlet oxygen. In yet another embodiment, reactive oxygen
species output 316 includes more than two chemical precursor
species to release singlet oxygen.
[0101] FIG. 4 shows an exemplary method 400 for generating reactive
oxygen species output 314 using system 300 of FIG. 3. FIG. 4 is
illustrated with use of an acetyl donor, but as discussed herein
can more generally use an acyl donor. In an embodiment, reactive
oxygen species output 316 generated by method 400 is concentrated
singlet oxygen precursor solution. In step 402, an alkaline
hydrogen peroxide anion solution 320 is created by mixing
H.sub.2O.sub.2 concentrate 302 with alkali concentrate 304. For
example, molar ratios of H.sub.2O.sub.2 concentrate 302 to alkali
304 may range from 1:1.2 to 1:2.5. In one embodiment, a preferred
molar ratio range is 1:1.4 to 1:2. In one embodiment, hydrogen
peroxide is a weak acid with a pKa of 11.6 and therefore its
combination with alkali converts it in an acid-base equilibrium to
the hydrogen peroxide anion form as in Equation 1 above. In some
embodiments, raising the pH of a hydrogen peroxide solution enough
to put a significant proportion of hydrogen peroxide into the anion
form requires an excess of alkali over hydrogen peroxide. For
example, the molar excess of alkali 304 over H.sub.2O.sub.2
concentrate 302 may range from 20% to 100% greater alkali 304. In
one embodiment, a preferred molar excess range is 20% to 40%
greater alkali 304.
[0102] In step 404, the resulting alkaline hydrogen peroxide 320 is
stored in alkaline hydrogen peroxide holding tank 312 for immediate
or later use. Alkaline hydrogen peroxide 320 has a longer lifetime
prior to use which allows the alkaline hydrogen peroxide 320 to be
stored for several minutes to a few hours in alkaline hydrogen
peroxide holding tank 312 without as much decomposition as a
peracid at a similar concentration.
[0103] In step 406, the alkaline hydrogen peroxide 320 is combined
with an acyl or acetyl donor 306 in mixing tank 318(1) to create a
resulting alkaline peracid concentrate 320'. In one embodiment, the
acetyl donor 30 is added in proportion to the alkaline hydrogen
peroxide 320. In one embodiment, the molar ratio of H.sub.2O.sub.2
320 to acyl or acetyl donor 304 reactive groups may range from
1:1.25 to 1:4. For example, a preferred molar ratio range is 1:1.5
to 1:2. In one embodiment, the acyl or acetyl donor is an
oxygen-acyl or oxygen-acetyl donor shown in Equation 2a above,
where Ac is acyl [--C(O)R'] or acetyl [--C(O)CH.sub.3] and R and R'
are hydrocarbon-based substituents, and more specifically are alkyl
or aryl groups. In an alternative embodiment, the acyl or acetyl
donor is a nitrogen-acyl or nitrogen-acetyl donor as shown in
Equation 2b above, where Ac is acyl [--C(O)R'] or acetyl
[--C(O)CH.sub.3] and R and R' are hydrocarbon-based substituents,
or more specifically are alkyl or aryl groups.
[0104] In Equations 2a/2b above, the reaction between an acyl or
acetyl donor 306 and alkaline hydrogen peroxide 320 occurs at
alkaline pH by nucleophilic attack of the acyl carbonyl carbon atom
by the hydrogen peroxide anion, which displaces the donor molecule
fragment as an alcohol or amine in a manner analogous to
saponification. In some embodiments, the non-equilibrium reactions
generalized in Equations 2a/2b are conducted between pH 10 and pH
13.
[0105] The use of non-equilibrium reaction in Equations 2a/2b
provides, for example, alkaline peracid concentrates 320' with
concentrations of less than approximately 10 wt % peroxyacetic acid
or less than 5 wt % peroxyacetic acid and other organic peracids
are produced efficiently and rapidly. Using the non-equilibrium
reaction allows the hydrogen peroxide residual to be minimized, if
necessary. In one embodiment, for example, the peroxyacetic acid
water/peroxide concentration ratios can be 10, 100, or 1000
depending on the ratio of hydrogen peroxide to acyl or acetyl donor
ratio in Equations 2a/2b. Hydrogen peroxide is preferably minimized
in alkaline peracid concentrate. Hydrogen peroxide is preferably
less than 3% the mass concentration of peroxyacetic acid or other
peracid, and more preferably less than 0.5% the mass concentration
of peroxyacetic acid or other peracid. Concentrates having only
trace or no detectible levels of hydrogen peroxide are preferred.
In one embodiment, at least one molar equivalent of acyl donor 106
is added for each equivalent of hydrogen peroxide in alkaline
hydrogen peroxide anion 320 used in Equations 2a/2b to consume all
of the hydrogen peroxide. In alternative embodiments, excess acyl
donor 306 reactive groups is necessary to minimize the hydrogen
peroxide residual due to the competing conversion of acyl donor 306
reactive groups to the corresponding carboxylic acid by the alkali
concentrate 304 used to raise the pH of the H.sub.2O.sub.2
concentrate 302. The molar ratio of hydroxide to hydrogen peroxide
affects the preferred ratio of acyl or acetyl donor reactive groups
to hydrogen peroxide. For example, in an embodiment, for example,
for bulk chemical mixing illustrated in FIG. 3, the preferred molar
ratio of sodium hydroxide to hydrogen peroxide is 1:1 resulting in
a preferred ratio of acyl donor reactive groups to hydrogen
peroxide of about 2:1. This will provide preferred low relative
amounts of hydrogen to peracid. In another embodiment, for example,
for alkaline hydrogen peroxide produced by an electrochemical
reactor in cathode output, as illustrated in FIG. 5, the molar
ratio of sodium hydroxide to hydrogen peroxide is about 2:1, with
the ratio increasing as current efficiency for hydrogen peroxide
production decreases, resulting in a preferred ratio of acyl donor
reactive groups to hydrogen peroxide of at least 2:1 and preferably
about 2.3:1. In another embodiment, alkaline hydroperoxide and
superoxide produced by in the cathode output of an electrochemical
reactor, as illustrated in FIG. 11, the molar ratio of sodium
hydroxide to hydrogen peroxide is about 4.5:1, with the ratio
increasing as current efficiency for hydrogen peroxide and
superoxide production decreases, resulting in a preferred ratio of
acyl donor reactive groups to hydrogen peroxide of at least 3:1. In
the above examples the ratio of acyl donor reactive groups to
hydrogen peroxide can be increased by 2-fold or more without
significant detriment to performance.
[0106] In optional step 408, as indicated by the dashed lines,
method 400 entrains byproducts 320 produced by the reactions of
Equations 2a/2b occurring in step 406. For example, byproducts 322
are entrained in solution with the alkaline peracid concentrate
320'. In one embodiment, byproducts 322 are useful as co-solvents,
pH buffers, chelating agents or stabilizers and carbon substrates
for microbial processes after a chemical oxidation process. For
example, the byproduct 322 of acetyl donors 306 of monacetin,
diacetin and triacetin is glycerol, a potential co-solvent and
favorable carbon source for microbes. In another embodiment,
byproduct 322 of acetyl donor 106 of TAED, diacetylethylenediamine,
acts as a chelating agent for transition metal ions and potentially
serves as a peroxide stabilizer. In yet another embodiment,
byproduct 322 is the carboxylic acid produced after an alkaline
peracid concentrate 320' reacts with a material or decomposes.
Alternatively, acetic acid, a byproduct 322 of peroxyacetic acid,
serves as a co-solvent, a pH buffer, a chelating agent, and a
biological substrate.
[0107] In step 410, method 400 adjusts the alkaline peracid
concentrate 320' pH to the activated pH level for producing
reactive oxygen species output 314 by adding acid concentrate 308
and mixing in mixing chamber 318(2). The resulting reactive oxygen
species output 314 is then distributed to its point of use in
liquid form. The reactive oxygen species output 314 may then be
used in the form of a liquid, an ice, a foam, an emulsion, a
micro-emulsion or an aerosol applied by means such as injection,
flooding, spraying, circulation or any other means of conveying a
fluid. In one embodiment, the alkaline peracid concentrate 320' pH
does not require the addition of acid concentrate 308 and is ready
for immediate distribution 410 to its point of use.
[0108] In one embodiment, during step 410, an acid concentration
308 is combined with alkaline peracid concentrate 320' such that
there is a population of both peracetic aid and peracetic acid
anion which react together to generate singlet oxygen according to
Equation 3 above, wherein the reaction rate for Equation 3 above
follows a second order kinetics and is maximized when the ratio of
the two forms of peroxyacetic acid is equivalent at its pKa of 8.3.
The evolution and release of singlet oxygen occurs over time
ranging from minutes to several hours depending on the rate of
reaction in Equation 3 above. In one embodiment, the evolution of
singlet oxygen from peroxyacetic acid, or other organic peracid
having a similar pKa, the pH is between 6 and 11 or more
specifically between 6.5 and 9.5.
[0109] In optional step 412, as indicated by a dashed outline,
method 400 adds additives concentrate 310 to the resulting peracid
from step 410, and then distributes the resulting solution for
use.
[0110] In optional step 414, as shown by the dashed outline, method
400 further activates the reactive oxygen species output 314 by
means of a Fenton or Fenton-like catalyst, ultrasound, ultraviolet
radiation or thermal activation (not shown in FIG. 3) to produce
radical species such as hydroxyl radicals.
[0111] Generation of Reactive Oxygen Species Using Electrochemical
Generator
[0112] In the following embodiments, reactive oxygen species are
generated by creating the necessary constituents and their mixing
through the generation of all or a portion of these materials on
site in a manner that minimizes the number of bulk chemical
feedstocks and eliminates hazardous bulk chemical feedstocks. For
example, the required components of hydrogen peroxide, alkali, and
acid may be co-generated electrochemically from simple feedstocks
including water, oxygen gas, and a salt or brine.
[0113] In the following embodiments, alternative methods are shown,
for example, for delivering reactive oxygen compositions which can
also generate hydroxyl radicals in cases where chlorate and bromate
formation is not a primary issue.
[0114] FIG. 5 shows an exemplary system 500 for generating
chemicals using an electrochemical reactor 514 and mixing the
reactor's 514 outputs together and optionally with other materials
to produce a diluted reactive oxygen species output 522. FIG. 5 is
illustrated with use of an acetyl donor, but as discussed herein
can more generally use an acyl donor. In one embodiment, diluted
reactive oxygen species output 520 is used, but not limited to, in
applications where a fluid is conveyed to a surface or material as
the primary reactive oxygen species in addition to the parent
oxidants at the point of use or in situ. In some embodiments,
applications include, but are not limited to, in situ chemical
oxidation for remediation of soil and groundwater; ex-situ chemical
oxidation for remediation of soil, construction or demolition
debris; hard surface cleaning and decontamination, clean-in place
applications in food, dairy, beverage and biopharma production and
processing; cleaning of membrane filtration systems; and flushing
of well casings and water distribution pipes.
[0115] System 500 includes an electrochemical reactor 514 including
inputs of a makeup water 502(1), brine 504, oxygen gas 506, and
power source 508, an acyl or acetyl donor 510, an additives
concentrate 512, pumps 516, holding tanks 518, mixing chambers 520,
and reactive oxygen species output 522. In one embodiment, the
electrochemical reactor 514 is that embodied by PCT Application No.
PCT/US2012/040325 titled "Electrochemical Reactor and Process."
This published PCT application is incorporated by reference herein
in its entirety for its description of electrochemical reactors and
processes. More specifically, the reference includes description
for reactor device configurations including cathodes and anodes
which are useful in embodiments of this invention. The reference
also includes descriptions of reactors useful for preparation of
oxidants including hydrogen peroxide, superoxide, sodium
hypochlorite, hypochlorites among others and for generation of
alkali, and acids. Details of reactor cathodes and anodes and
processes for production of oxidants are also incorporated by
reference herein. An exemplary electrochemical reactor is shown in
FIG. 6.
[0116] Exemplary Electrochemical Reactor
[0117] FIGS. 6A/6B depict an exemplary a cross-sectional view of
the general configuration and components of an exemplary
electrochemical reactor 600 for use in system 500 of FIG. 5, in one
embodiment. In one embodiment, electrochemical reactor 600 has a
general tubular or annular configuration. The housing for
electrochemical reactor 600 has three distinct parts an anode
housing 620, a seat plate 634, and an end plate 636, each of which
may be fabricated in quantity from structural thermoplastics (pure
and filled) including, but not limited to, polyvinyl chloride
(PVC), chlorinated polyvinylchloride (CPVC), polyvinylidine
difluoride (PVDF), polyethylene, polytetrafluoroethylene (PTFE),
ethylene tetrafluoroethyelene (ETFE), acrylonitrile butadiene
styrene (ABS) polymer blends, etc.
[0118] In an embodiment, anode housing 620 is an extruded tube,
such as a standard schedule 80 pipe that is modified with tube
fittings, feed-throughs, O-ring, or gasket sealing surfaces and
threaded bolt holes. In an embodiment, anode housing 620 contains
the anolyte solution within electrochemical reactor 600. In an
embodiment, anode housing 620 contains the anolyte solution within
an anolyte chamber 618. In an embodiment, anode housing 620
provides structural integrity to electrochemical reactor 600 and is
what seat plate 634 and end plate 636 are fastened to, thereby
holding electrochemical reactor 600 and its contents together as a
single unit. In some embodiments, anode housing 620 is made from
PVC.
[0119] In an embodiment, seat plate 634 contains a central opening
with a tapered surface on which a separator 614 is sealed. A
cathode 612 extends through seat plate 634. A cathode current
distributor and compression ferrule 630 contacts cathode 612 and
anchors it in place while simultaneously compressing separator 614
to make a gas-tight seal between a cathode flow channel 610 and the
anolyte chamber 618. Seat plate 634 also has gasket or O-ring
sealing surfaces for making gas-tight seals with anode housing 620
and with cathode current distributor and compression ferrule
assembly 630.
[0120] In an embodiment, cathode current distributor and
compression ferrule 630 may be constructed of a rigid material that
is conductive and non-corrosive such as stainless steel alloys,
high nickel alloys, and high purity titanium, for example. In an
embodiment, cathode current distributor and compression ferrule 630
is 316 stainless steel. In yet another embodiment, the surfaces of
current distributor and compression ferrule 630 facing into cathode
flow channel 610 and manifold are masked with a non-conductive
material such as a thermoplastic, a polymer coating, or an
elastomeric adhesive coating.
[0121] In an embodiment, end plate 636 provides a gas inlet 602 and
catholyte fluid distribution manifolds which are accessed through
the catholyte inlet or outlet 608. In an embodiment end plate 636
seals against the end of a gas distributor tube 606 creating a
separate gas chamber 604 down the center axis of electrochemical
reactor 600. End plate 636 contains gasket and O-ring sealing
surfaces for making gas-tight seals with gas distributor tube 606
and cathode current distributor and compression ferrule assembly
630. In an embodiment, end plate 636 provides the compressive force
to seal separator 614 to seat plate 634, seal seat plate 634 to
anode housing 620, seal the faces of the cathode current
distributor and compression ferrule assembly 630 to end plate 636
and seat plate 634, seal gas distributor tube 606 and fasten
electrochemical reactor 600 together.
[0122] In an embodiment, end plate 636 holds the cathode electrical
feed-through posts 632, which contact cathode current distributor
and compression ferrule 630 and are connected by means of
conductors to the negative pole (direct current, DC) or ground
(alternating current, AC) of a power supply. In one embodiment,
electrical feed-through posts 632 are made from a material that is
conductive and non-corrosive such as stainless steel alloys, high
nickel alloys, and high purity titanium, for example. In an
embodiment, cathode electrical feed-through posts 632 are 18-8
stainless steel.
[0123] In one embodiment, gas distribution tube 606 is a porous or
microporous material that allows gas to permeate through its wall
and resists water permeation. In an embodiment, gas distribution
tube 606 is a non-conductive, hydrophobic material such as
polyethylene, polypropylene, polytetrafluoroethylene, or
polyvinylidene difluoride, for example. In an embodiment, gas
distribution tube 606 may be a microporous ceramic such as alumina,
zirconia, titania or other suitable material with a hydrophobic
coating. Gas distribution tube 606 may be made by casting-sintering
or extrusion production methods, for example. In an embodiment, gas
distribution tube 606 contains pores having a diameter rating that
is less than about 10 microns. In an embodiment, gas distribution
tube 206 contains pores having a diameter rating that is less than
about or equal to 5 microns. The pores of gas distribution tube 606
may be masked in part to bias the gas permeation through regions of
gas distribution tube 606 for purposes including making the ends
gas and liquid impermeable in the catholyte manifold and current
collector regions, compensating for pressure gradients, gas loading
in the catholyte, and/or modulating residence time in the cathode
flow chamber.
[0124] In an embodiment, cathode flow channel 610 is defined by gas
distribution tube 606 and separator 614. Cathode 612 resides within
cathode flow channel 610 immersed in the catholyte liquid while gas
is supplied from the back side of cathode 612 and the front side of
cathode 612 faces the separator 614. Cathode 612 may be positioned
anywhere within cathode flow channel 610, including having direct
contact with the separator 614 and/or gas distribution tube
606.
[0125] In one embodiment, separator 614 separates the catholyte and
anolyte fluids from one another, thereby keeping the respective
reactants and products from mixing in an uncontrolled manner,
providing control of two-phase fluid dynamics (flow distribution,
mixing, electrode contact, partial pressures of gases), preventing
undesirable side reactions, preventing electrode shorting or shunt
losses, and allowing for precise control of process conditions at
each electrode. In an embodiment separator 614 may be a porous,
microporous or nanoporous separator composed of materials including
polypropylene, polyethylene, polytetrafluoroethylene,
polyvinylidine difluoride, polysulfone, polyethersulfone or a
ceramic material (e.g., alumina, zirconia, rare earth oxide,
nitride). In an embodiment, separator 614 may be an ion exchange
including cation exchange membranes (e.g., perfluorosulfonic acid,
sulfonated polyfluorostyrene, sulfonated
polystyrene-divinylbenzene, perfluorosulfonimide, and perfluoro
carboxylate membranes) or anion exchange membranes (e.g.,
quaternary ammonium polystyrene-divinylbenzene and doped
polybenzimidazole membranes), for example. Separator 614 may be
formed into a tubular shape by casting, extrusion, or rolling flat
sheets and bonding a seam. In an embodiment, separator 614 is a
tubular perfluorosulfonic acid membrane such as Nafion.TM..
[0126] In an embodiment, cathode 612, also known as a cathode
electrode, is a high porosity or high surface area material that
can conform to a tubular shape and be continuously conductive down
the length of its form. Cathode 612 may be a pure metal, an alloy,
a conductive polymer, a carbonized or graphitized polymer. In an
embodiment cathode 612 has a coating that imparts conductivity,
reaction selectivity, catalysis, adsorption, resistance to hydrogen
evolution, increased surface area or modifies wetability. In an
embodiment, cathode 612 may be made of one or more porous material
formats including sintered or bonded particles, sintered or bonded
fibers, woven mesh, continuous fibers or filaments, cloths, felts,
and electro-spun or melt-spun filamentous forms. In an embodiment
the electrode porosity and pore structure of cathode 612 may be
uniform, graded or random. In an embodiment cathode 612 has an
electrode specific surface area greater than about 10 m.sup.2 per 1
m.sup.2 superficial area. In an embodiment cathode 612 has an
electrode specific surface area greater than about 100 m.sup.2 per
1 m.sup.2 superficial area. In an embodiment cathode 612 is
continuous carbon fibers. The carbon fiber surfaces cathode 612 may
be modified to possess carbon oxide species. In another embodiment,
the carbon fiber surfaces of cathode 612 are coated with a catalyst
that may be an organic material (e.g., adsorbed or bonded molecules
or polymers) or an inorganic material (e.g., adsorbed, bonded or
electrodeposited metals, semiconductors, alloys and their oxide or
sulfide derivatives) or a mixture thereof.
[0127] In one embodiment, anode 616, also known as an anode
electrode, can be a dimensionally stable anode consisting of an
expanded titanium mesh coated with a catalyst. The catalyst is
optimized for oxidation of species in an anolyte solution filling
anolyte chamber 618, such as water or halides or other redox active
materials, at reduced overpotentials or voltage. In some
embodiments, the catalyst is a precious metal, noble metal,
platinum group metal or oxides of such metals. In an embodiment,
the catalyst is iridium oxide.
[0128] In an embodiment, anode 616 is in a tubular form, and may be
in direct contact with separator 614, and may provide mechanical
support to separator 614. In an embodiment, at least one titanium
anode current collector tab 626 is affixed to the side of anode 616
and provides a point of attachment for the anode electrical
feed-through post 628, which is also titanium.
[0129] In one embodiment, a heat transfer coil, which is not
depicted in FIG. 6A or FIG. 6B, can be positioned in anolyte
chamber 618 with feedthroughs using two of the anolyte inlet and
outlet/vent ports 622 and 624, respectively. If required, the heat
transfer coil may be used in the reactor process for cooling or
heating the anolyte solution. In an embodiment, the heat transfer
coil is a metal or plastic tube made of a non-corrosive material
such as stainless steel alloys, high purity titanium, high nickel
alloys, polyvinyl chloride, polypropylene, polyvinylidene
difluoride, polytetrafluoroethylene. The heat transfer fluid
circulated through the coil may be water, catholyte solution, gas,
air, glycol solutions, for example.
[0130] FIG. 7 depicts an embodiment of a reactor system 700 that
has a reactor system fluid process flow, also known as a flow
pathway, that enables gas recirculation within reactor system 700.
A regulated gas makeup stream enters the gas circulation loop
through the gas inlet line 702. The gas passes through the gas feed
flow control valve 704 and the gas feed flow meter 706 and then
enters the gas chamber 708 of the reactor. At least one boundary of
the gas chamber is a gas distributor (not depicted in FIG. 7, but
described above and depicted in FIG. 6 as gas distributor 606). The
gas passes through the gas distributor and into the cathode chamber
710. Excess gas not consumed in electrochemical process exits
cathode chamber 710 co-linearly with liquid catholyte and cathodic
products formed through the cathode product line 712. The liquid
and gas mixture passes through a cooling coil 714 prior to entering
a gas-liquid separator 716. The separated liquid, which can contain
products formed in cathode chamber 710, is collected in a cathode
product tank 718. The separated gas flows through a gas
recirculation line 720, through a gas pump 722 and is returned to
gas inlet line 702. A portion of the separated gas is removed from
the system through a gas bleed flow control valve 724 and a gas
bleed flow meter 726. Bleed rate of gas from the system is
preferably the same as the mass flow of the gas makeup stream
entering the system less the mass consumption of gas in the reactor
less the mass production of gas recovered from the anode chamber
746 and added to the gas makeup stream through an anode gas vent
754.
[0131] While gas is passing through the system described in
reference to FIG. 7, a catholyte solution makeup 730 is added to
the cathode feed tank 732 where the head space of the tank can be
open to the gas makeup stream through a gas pressure line 728. In
some embodiments, the pneumatic pressure for the gas makeup stream
may be used to feed the catholyte solution into cathode chamber 710
of the reactor. In additional embodiments, the hydraulic pressure
of the catholyte solution makeup may be used to feed the catholyte
solution into cathode chamber 710 of the reactor. The catholyte
flows from cathode feed tank 732 through the catholyte inlet line
734, passes through a catholyte flow control valve 736 and
catholyte flow meter 738 and enters cathode chamber 710 of the
reactor. Excess liquid catholyte not consumed in electrochemical
process and cathodic products formed exit cathode chamber 710
co-linearly with gas through cathode product line 712. The liquid
and gas mixture passes through cooling coil 714 prior to entering
gas-liquid separator 716. The separated liquid, which can contain
products formed in cathode chamber 710, is collected in cathode
product tank 718. The liquid cathode product can be removed from
the system during or after operation through the cathode product
drain 740.
[0132] While gas and catholyte is passing through the system
described in reference to FIG. 7 an anolyte solution makeup 742 is
added to the anode feed tank 744. The anolyte is supplied through
anolyte feed line 746 to the anode chamber 748 by the action of
gravity or a pump (not shown). Excess liquid anolyte not consumed
in electrochemical process and anodic products formed, including
gas, exit the anode chamber collinearly through the anode product
line 750 and then pass through a gas-liquid separator 752. The
separated liquid is returned to anode feed tank 744 while the
separated gas is optionally fed to the gas makeup stream through
anode gas vent 754. Anode gas vent 754 also serves to expose anode
chamber 748 to the gas inlet line pressure such that the
differential pressure between anode chamber 748 and cathode chamber
710 remains constant at any gas inlet line pressure or during
pressure fluctuations in the system. The liquid anode or anode
product can be removed from the system during or after operation
through the anode product drain 756. While gas, catholyte, and
anolyte are passing through the system described in reference to
FIG. 7 a voltage or current is applied to the reactor by a
controller (not shown in FIG. 6 or 7).
[0133] Referring back to FIG. 5, it is noted that the present
embodiments herein are not limited to only the electrochemical
reactor 600 discussed above, or those disclosed in published
International application WO2012/166997; thus, alternative
electrochemical reactors may be incorporated and used in the
embodiments herein.
[0134] In one embodiment, electrochemical reactor 514 creates two
outputs including alkaline hydrogen peroxide 524 output and acid
concentrate 526 output, as discussed below with reference to
Examples 1-3.
[0135] In one embodiment, brine 504 is a solution that contains
ions necessary for producing alkaline hydrogen peroxide and acids
in two separate streams. The brine 504 may also contain pH buffers
and co-solvents compatible with the reaction process, which
contribute to the reactive oxygen species output 522 formulation.
For example, pH buffers include weak chemical electrolytes chosen
from the group including: acetate, citrate, propionate, phosphate
and sulfate.
[0136] Acyl or acetyl donor 510 includes, but is not limited to, an
acyl or acetyl donor chosen from the group including: monoacetin,
diacetin, triacetin, acetylsalicylic acid, methyl benzoate, ethyl
lactate and tetraacetylethylenediamine (TAED). In alternative
embodiments, other synthetic or natural esters, mono-, di- and
triacylglycerides and phospholipids having acyl substituents
possessing more than one carbon can provide other types of organic
peracids by the non-equilibrium reaction mechanism. Acyl or acetyl
donor 510 or mixture of donors may be in liquid or solid form, or
dissolved in a solvent when reacted with a solution of hydrogen
peroxide. Additives concentrate 512, for example, include at least
one of the following additives chosen from the group including:
salts, surfactants, co-solvents, stabilizers, and emulsifiers.
[0137] FIG. 8 shows an exemplary method 800 for generating a
diluted reactive oxygen species output 522 using system 500 of FIG.
5. FIG. 8 is illustrated with use of an acetyl donor, but as
discussed herein can more generally use an acyl donor. In step 802,
method 800 generates an alkaline hydrogen peroxide 524 output, and
an acid concentrate 526 output. Acid concentrate output 526 is then
stored in holding tank 518(1). Exemplary processes for generating
outputs 524 and 526 are discussed below in Examples 1-3. In one
embodiment, both output streams 524 and 526 are in concentrated
liquid forms produced at a constant rate. For example, the alkaline
hydrogen peroxide 524 output may contain 0.1 wt % to 3 wt %
hydrogen peroxide at pH 12.0 to 13.0. Typical alkaline hydrogen
peroxide 524 output may contain 0.3 wt % to 0.8 wt % hydrogen
peroxide at pH 12.1 to 12.6. The acid concentrate 526 output may
contain 0.1 wt % to 20 wt % depending on the concentration and
composition of anolyte solution makeup 742. For example, a 20 wt %
sodium acetate solution as anolyte solution makeup 742 may produce
13.5 wt % acetic acid at 85% conversion efficiency. In an
alternative embodiment, an anolyte solution makeup 742 is a 5 wt %
sodium sulfate solution that may produce 3.6 wt % bisulfate acid at
85% conversion efficiency.
[0138] In step 804, the alkaline hydrogen peroxide 524 output is
combined with acyl or acetyl donor 510 in mixing tank 520(1) to
create alkaline peracid concentrate 524'. In one embodiment,
alkaline peracid concentrate 524' may be peroxyacetic acid. In one
embodiment, the acyl or acetyl donor 510 is added in proportion to
the hydrogen peroxide 524. In one embodiment, the molar ratio of
H.sub.2O.sub.2 524 to acyl or acetyl donor 510 reactive group
equivalents may range from 1:1.25 to 1:4. For example, a preferred
molar ratio range is 1:1.5 to 1:2.5, more preferably the molar
ratio range is 1:1.9 to 1:2.1 and most preferably the molar ratio
is 1:2. If the ratio is too low a high hydrogen peroxide residual
will remain in the peracid concentrate where it will significantly
quench singlet oxygen. If the ratio is higher than needed to
achieve a low hydrogen peroxide residual that does not
significantly quench singlet oxygen, then excess acyl or acetyl
donor remains unused. In one embodiment, the acyl or acetyl donor
is an oxygen-acyl or oxygen-acetyl donor shown in Equation 2a
below:
HOO.sup.-+AcOR.fwdarw.AcOO.sup.-+ROH [2a]
Where Ac is acyl [--C(O)R'] or acetyl [-C(O)CH.sub.3] and R and R'
are hydrocarbon-based substituents and more specifically are alky
or aryl groups. In an alternative embodiment, the acyl or acetyl
donor is a nitrogen-acyl or nitrogen-acetyl donor as shown in
Equation 2b below:
HOO.sup.-+AcNR.sub.2.fwdarw.AcOO.sup.-+RNH [2b]
Where Ac is acyl [--C(O)R'] or acetyl [--C(O)CH.sub.3] and R and R'
are hydrocarbon-based substituents and more specifically are alkyl
or aryl groups.
[0139] In Equations 2a/2b above, the reaction between an acyl or
acetyl donor 510 and alkaline hydrogen peroxide 524 occurs at
alkaline pH by nucleophilic attack of the acyl carbonyl carbon atom
by the hydrogen peroxide anion, which displaces the donor molecule
fragment as an alcohol or amine in a manner analogous to
saponification. In some embodiments, the non-equilibrium reactions
generalized in Equations 2a/2b are conducted between pH 10 and pH
13.
[0140] A particular advantage of the use of non-equilibrium
reaction in Equations 2a/2b is that peracid solutions 524'' with
concentrations of less than approximately 10 wt % peroxyacetic acid
and/or other organic peracids can be produced efficiently and
rapidly. Peracid solutions 524'' with concentrations of less than
approximately 5 wt % peroxyacetic acid and/or other organic
peracids can be produced. Using the non-equilibrium reaction allows
the hydrogen peroxide residual to be minimized if necessary. In one
embodiment, for example, the peroxyacetic acid water/peroxide
concentration ratios can be 10, 100, or 1000 depending on the ratio
of hydrogen peroxide to acyl donor ratio in Equations 2a/2b.
Hydrogen peroxide is preferably minimized in alkaline peracid
concentrate. Hydrogen peroxide is preferably less than 3% the mass
concentration of peroxyacetic acid or other peracid, and more
preferably less than 0.5% the mass concentration of peroxyacetic
acid or other peracid. Concentrates having only trace or no
detectible levels of hydrogen peroxide are preferred. In one
embodiment, at least one molar equivalent of acyl or acetyl donor
510 reactive groups is added for each equivalent of hydrogen
peroxide in alkaline hydrogen peroxide anion solution 524 used in
Equations 2a/2b to consume all of the hydrogen peroxide.
[0141] In optional step 806, as indicated by the dashed lines,
method 800 entrains byproducts 528 produced by the reactions of
Equations 2a/2b. In one embodiment, byproducts 528 are entrained in
solution with the alkaline peracid concentrate 524'. In one
embodiment, byproducts 528 are useful as co-solvents, pH buffers,
chelating agents or stabilizers and carbon substrates for microbial
processes after a chemical oxidation process. For example, the
byproduct 528 of acetyl donors 510 of monacetin, diacetin and
triacetin is glycerol, a potential co-solvent and favorable carbon
source for microbes. In another embodiment, byproduct 528 of acetyl
donor 510 of TAED, diacetylethylenediamine, acts as a chelating
agent for transition metal ions and potentially serves as a
peroxide stabilizer. In yet another embodiment, byproduct 528 is
the carboxylic acid produced after alkaline peracid concentrate
524' reacts with a material or decomposes. Alternatively, acetic
acid, a byproduct 528 of peroxyacetic acid, serves as a co-solvent,
a pH buffer, a chelating agent, and a biological substrate.
[0142] In step 808, the resulting alkaline peracid concentrate 524'
is then diluted with makeup water 502(2) introduced by pump 516(2)
to create a diluted peracid 524'' to nearly the point of use
concentration and is stored in holding tank 518(2). In optional
step 810, as indicated by the dashed outline, additional additives
concentrate 512 is combined with diluted peracid 524'' and then
stored into holding tank 518(2).
[0143] In step 812, the diluted peracid's 524'' pH is adjusted, by
combining diluted peracid 524'' with created acid concentrate 526,
to the activated pH level for producing reactive oxygen species
output 522 The resulting reactive oxygen species output 522 is then
distributed to its point of use in liquid form. The reactive oxygen
species output 522 may then be used in the form of a liquid, an
ice, a foam, an emulsion, a micro-emulsion or an aerosol applied by
means such as injection, flooding, spraying, circulation or any
other means of conveying a fluid. In one embodiment, the diluted
peracid's 524'' pH does not require the addition of acid
concentrate 526 and is ready for immediate distribution to its
point of use.
[0144] In one embodiment, during step 812, an acid concentration
526 is combined with diluted peracid 524'' such that there is a
population of both peracid (e.g., peracetic acid) and the
corresponding peracid anion (e.g., peracetate anion)which react
together to generate singlet oxygen according to Equation 3
below:
AcOOH+AcOO.sup.-.fwdarw..sup.1O.sub.2+AcOH+AcO.sup.- [3]
Wherein the reaction rate for Equation 3 above follows a second
order kinetics and is maximized when the ratio of the two forms of
peroxyacetic acid is equivalent at its pKa of 8.3. The evolution
and release of singlet oxygen occurs over time ranging from minutes
to several hours depending on the rate of reaction in Equation 3
above. In one embodiment, the evolution of singlet oxygen from
peroxyacetic acid, or other organic peracid having a similar pKa,
the pH is between 6 and 11 or more specifically between 6.5 and
9.5.
[0145] In optional step 814, as indicated by the dashed outline,
the reactive oxygen species output 522 may further be activated by
means of a Fenton or Fenton-like catalyst, ultrasound, ultraviolet
radiation, or thermal activation to produce other reactive species,
which can include additional reactive oxygen species, such as
hydroxyl radical, or reactive species other than reactive oxygen
species, e.g., hydrocarbon radicals, such as alkyl radicals.
[0146] FIG. 9 shows an exemplary system 900 for generating
chemicals using an electrochemical reactor 914 and mixing the
reactor's 914 outputs together and optionally with other materials
to produce a concentrated reactive oxygen species output 922. In
one embodiment, concentrated reactive oxygen species output 922 is
used, for example, in applications where a concentrate is dosed
into a liquid stream which is to be treated or used to distribute
the precursor solution throughout a larger system while generating
singlet oxygen, for example, as the primary reactive oxygen species
in addition to the parent oxidant(s) at the point of use or
in-situ. In some embodiments, applications include water and
wastewater treatment; cooling tower water treatment and cooling
tower system cleaning; desulfurization and deodorization of gases;
water treatment in forestry operations, pulp and paper making
processes; oil and gas produced water and hydraulic fracturing
flowback water treatment.
[0147] System 900 includes an electrochemical reactor 914 including
inputs of a makeup water 902, brine 904, an oxygen gas 906, and
power source 908, an acyl or acetyl donor 910, an additives
concentrate 912, holding tanks 916, pumps 918, mixing chambers 920,
and reactive oxygen species output 922. In one embodiment, the
electrochemical reactor 914 is that embodied by published
International application WO2012166997. An exemplary
electrochemical reactor is shown in FIGS. 6-7.
[0148] In one embodiment, brine 904 is a solution that contains
ions necessary for producing alkaline hydrogen peroxide and acids
in two separate streams. In one embodiment, brine 904 may contain 5
wt % sodium sulfate. A small fraction of brine 904 may be fed as a
side stream to the cathode feed tank 732 where it is diluted by a
factor of 20 with water to 0.25 wt % sodium sulfate before being
fed to the catholyte inlet line 734 to serve as an electrolyte. The
remaining majority of brine 904 is fed to the anolyte solution
makeup 742 and converted to approximately 3.6 wt % sodium bisulfate
acid at 85% conversion efficiency. The sodium displaced from sodium
sulfate is transported from anode to cathode to support current
flow in the reactor and combines with anionic oxygen species
produced at the cathode including hydroxide, hydroperoxide and
superoxide. In an alternative embodiment, all of brine 904 is fed
to anolyte solution makeup 742 while a separate brine (not shown)
of different composition and concentration is fed separately into
the catholyte feed tank 732. The brine 904 may also contain pH
buffers and co-solvents compatible with the reaction process, which
contribute to the reactive oxygen species output 922 formulation.
For example, pH buffers include weak chemical electrolytes chosen
from the group including: acetate, citrate, propionate, phosphate
and sulfate. Co-solvents may include a substance chosen from the
group including: alcohols such as methanol, ethanol, propanol,
propylene glycol, glycol ethers, glycerol, ethyl lactate, soybean
oil, vegetable oil, sunflower oil, peanut oil and guar gum.
[0149] Acyl or acetyl donor 910 or mixture of donors may be in
liquid or solid form, or dissolved in a solvent when reacted with a
solution of hydrogen peroxide. Additives concentrate 912, for
example, include at least one of the following additives chosen
from the group including: salts, surfactants, co-solvents,
stabilizers, and emulsifiers.
[0150] FIG. 10 shows an exemplary method 1000 for generating a
concentrated reactive oxygen species output 922 using system 900 of
FIG. 9. FIG. 10 is illustrated with use of an acetyl donor, but as
discussed herein can more generally use an acyl donor. In step
1002, method 1000 generates an alkaline hydrogen peroxide 924
output, and an acid concentrate 926 output. Alkaline hydrogen
peroxide output 924 and acid concentrate output 926 is then stored
in separate holding tanks 916(1), 916(2), respectfully, for
immediate or later use. Alkaline hydrogen peroxide 924 has a longer
lifetime prior to use which allows the alkaline hydrogen peroxide
924 to be stored for several minutes to a few hours in holding tank
916(1) without as much decomposition as a peracid at similar
concentration. Exemplary processes for generating outputs 924 and
926 are discussed below in examples 1-3. In one embodiment, both
output streams 924 and 926 are in concentrated liquid forms
produced at a constant rate.
[0151] In step 1004, the alkaline hydrogen peroxide 924 output is
combined with acyl or acetyl donor 910 in mixing tank 920(1) to
create peracid 924'. In one embodiment, the acyl or acetyl donor is
an acyl or oxygen-oxygen-acetyl donor shown in Equation 2a above
where Ac is acyl [--C(O)R'] or acetyl [--C(O)CH.sub.3] and R and R'
are hydrocarbon-based substituents and more specifically are alkyl
or aryl groups. In an alternative embodiment, the acyl or acetyl
donor is a nitrogen-acyl or nitrogen-acetyl donor as shown in
Equation 2b above. Where Ac is acyl [--C(O)R'] or acetyl
[--C(O)CH.sub.3] and R and R' are hydrocarbon-based substituents
and more specifically are alkyl or aryl groups.
[0152] In Equations 2a/2b above, the reaction between an acetyl or
acyl donor 910 and alkaline hydrogen peroxide 924 occurs at
alkaline pH by nucleophilic attack of the acyl carbonyl carbon atom
by the hydrogen peroxide anion, which displaces the donor molecule
fragment as an alcohol or amine in a manner analogous to
saponification. In some embodiments, the non-equilibrium reactions
generalized in Equations 2a/2b are conducted between pH 10 and pH
13.
[0153] The use of non-equilibrium reaction in Equations 2a/2b
provides peracid solutions 924' with concentrations of less than
approximately 10 wt % peroxyacetic acid and/or other organic
peracids that are produced efficiently and rapidly. Peracid
solutions 924' with concentrations of less than approximately 5 wt
% peroxyacetic acid and/or other organic peracids can be produced.
Using the non-equilibrium reaction allows the hydrogen peroxide
residual to be minimized if necessary. In one embodiment, for
example, the peroxyacetic acid water/peroxide concentration ratios
can be 10, 100, or 1000 depending on the ratio of hydrogen peroxide
to acyl or acetyl donor ratio in Equations 2a/2b. Hydrogen peroxide
is preferably minimized in alkaline peracid concentrate. Hydrogen
peroxide is preferably less than 3% the mass concentration of
peroxyacetic acid or other peracid, and more preferably less than
0.5% the mass concentration of peroxyacetic acid or other peracid.
Concentrates having only trace or no detectible levels of hydrogen
peroxide are preferred.
[0154] In one embodiment, at least one molar equivalent of acyl or
acetyl donor 910 reactive groups is added for each equivalent of
hydrogen peroxide in alkaline hydrogen peroxide anion solution 924
used in Equations 2a/2b to consume all of the hydrogen
peroxide.
[0155] In optional step 1006, as indicated by the dashed lines,
byproducts 928 produced by the reactions of Equations 2a/2b are
collected. In one embodiment, byproducts 928 are useful as
co-solvents, pH buffers, chelating agents or stabilizers and carbon
substrates for microbial processes after a chemical oxidation
process. For example, the byproduct 928 of acetyl donors 910 of
monacetin, diacetin and triacetin is glycerol, a potential
co-solvent and favorable carbon source for microbes. In another
embodiment, byproduct 928 of acetyl donor 910 of TAED,
diacetylethylenediamine, acts as a chelating agent for transition
metal ions and potentially serves as a peroxide stabilizer. In yet
another embodiment, byproduct 928 is the carboxylic acid produced
after a peracid 924' reacts with a material or decomposes.
Alternatively, acetic acid, a byproduct 928 of peroxyacetic acid,
serves as a co-solvent, a pH buffer, a chelating agent, and a
biological substrate.
[0156] In step 1008, the concentrated peracid's 924' pH is
adjusted, by combining concentrated peracid 924' with created acid
concentrate 926, to the activated pH level for producing reactive
oxygen species output 922 The resulting reactive oxygen species
output 922 is then distributed to its point of use in liquid form.
The reactive oxygen species output 922 may then be used in the form
of a liquid, an ice, a foam, an emulsion, a micro-emulsion or an
aerosol applied by means such as injection, flooding, spraying,
circulation or any other means of conveying a fluid.
[0157] In one embodiment, during step 1008, an acid concentration
926 is combined with concentrated peracid 924' such that there is a
population of both peracetic aid and peracetic acid anion which
react together to generate singlet oxygen according to Equation 3
above. Wherein the reaction rate for Equation 3 above follows a
second order kinetics and is maximized when the ratio of the two
forms of peroxyacetic acid is equivalent at its pKa of 8.3. The
evolution and release of singlet oxygen occurs over time ranging
from minutes to several hours depending on the rate of reaction in
Equation 3 above. In one embodiment, the evolution of singlet
oxygen from peroxyacetic acid, or other organic peracid having a
similar pKa, the pH is between 6 and 11, or more specifically 6.5
and 9.5.
[0158] In one embodiment, the concentrated peracid's 924' pH does
not require the addition of acid concentrate 926 and is ready for
immediate distribution to its point of use.
[0159] In optional step 1010, as indicated by the dashed outline,
additional additives concentrate 912 is combined with concentrated
peracid 924' and then distributed as reactive oxygen species output
922 to the point of use.
[0160] In optional step 1012, as indicated by the dashed outline,
the reactive oxygen species output 922 may further be activated by
means of a Fenton or Fenton-like catalyst, ultrasound or
ultraviolet radiation to produce other reactive species, which can
include other reactive oxygen species, such as hydroxyl or
hydroperoxyl radicals, or reactive species other than reactive
oxygen species, such as hydrocarbon radicals, e.g., alkyl
radicals.
[0161] FIG. 11 shows an exemplary system 1100 for generating
chemicals using an electrochemical reactor 1114 and mixing the
reactor's 1114 outputs together and optionally with other materials
to produce a superoxide reactive oxygen species output 1122. In one
embodiment, the superoxide reactive oxygen species output 1122 is a
concentrated superoxide precursor. Alternatively, the superoxide
reactive oxygen species output 1122 is a diluted superoxide
precursor. In one embodiment, superoxide reactive oxygen species
output 1122 is used, but not limited to, applications where a
concentrate is dosed into a liquid stream, or applied to a surface
or material. In some embodiments, applications include water and
wastewater treatment; cooling tower water treatment and cooling
tower system cleaning; desulfurization and deodorization of gases;
water treatment in forestry operations, pulp and paper making
processes; oil and gas produced water and hydraulic fracturing
flowback water treatment; in-situ chemical oxidation for
remediation of soil and groundwater; ex-situ chemical oxidation for
remediation of soil; construction or demolition debris; hard
surface cleaning and decontamination; cleansing applications in
food, dairy, beverage and biopharma production and processing;
cleaning of membrane filtration systems.
[0162] System 1100 includes an electrochemical reactor 1114
including inputs of a makeup water 1102(1), brine 1104, an oxygen
gas 1106, and power source 1108, an additives concentrate 1110,
holding tanks 1116, pumps 1118, mixing chambers 1120, and
superoxide reactive oxygen species output 1122. In one embodiment,
the electrochemical reactor 1114 is that embodied by published
International application WO2012166997. An exemplary
electrochemical reactor is shown in FIGS. 6-7.
[0163] In one embodiment, brine 1104 is a solution that contains
ions necessary for producing alkaline hydrogen peroxide and acids
in two separate streams. The brine 1104 may also contain pH buffers
and co-solvents compatible with the reaction process, which
contribute to the reactive oxygen species output 1122 formulation.
For example, pH buffers include weak chemical electrolytes chosen
from the group including: acetate, citrate, propionate, phosphate
and sulfate. Co-solvents may include a substance chosen from the
group including: alcohols such as methanol, ethanol, propanol,
propylene glycol, glycol ethers, glycerol, ethyl lactate, soybean
oil, vegetable oil, sunflower oil, peanut oil and guar gum.
[0164] Additives concentrate 1110, for example, include at least
one of the following additives chosen from the group including:
salts, surfactants, co-solvents, stabilizers, and emulsifiers.
[0165] FIG. 12 shows an exemplary method 1200 for generating a
concentrated superoxide reactive oxygen species output 1122 using
system 1100 of FIG. 11, in one embodiment. In step 1202,
electrochemical generator 1114 is used to create a superoxide
solution 1124, as depicted below in Example 4. In one embodiment,
superoxide solution 1124 additionally contains hydrogen peroxide
co-generated with superoxide. In yet another embodiment, in step
1202, electrochemical generator 1114 creates superoxide solution
1124, with or without co-generation of hydrogen peroxide, and
additionally co-generates an acid concentrate 1126. The proportion
of superoxide to hydrogen peroxide co-generated can be adjusted by
the nature of the cathode surface. For carbon cathodes, a higher
degree of oxidation of the cathode surface can correlate with
higher superoxide to hydrogen peroxide ratios. Also, when using
such cathodes increasing cathodic current density can provide
relatively minor increases in the superoxide to hydrogen peroxide
production ratios. The molar ratio of superoxide to hydrogen
peroxide co-generated by the reactor can range from approximately
0.01:1 to 10:1. Molar ratios of superoxide to hydrogen peroxide can
range between 0.5:1 to 1.5:1, 1.5:1 to 3:1 or 3:1 to 5:1. One
preferred molar ratio range-of superoxide to hydrogen peroxide is
1:1 to 6. Another preferred molar ratio range of superoxide to
hydrogen peroxide is 3:1 to 5:1. Variation in the molar ratio of
superoxide to hydrogen peroxide in these formulations can affect
the oxidation properties of the formulations.
[0166] Electrochemically generated superoxide solutions in the
above ranges are more stable than those solutions generated from
bulk chemicals. Superoxide solutions produced from bulk chemicals,
at modestly alkaline pH's, i.e. 10-12.5 pH, contains HOOH in
equilibrium with NaOOH, causing the bulk chemical superoxide
solutions to have less stability. In contrast, electrochemically
generated superoxide solutions at pH greater than about 12.5 can be
made to initially contain HOO-- (e.g., NaOOH), which in the
presence of only O.sub.2-- (e.g., NaO.sub.2) and HO-- (e.g., NaOH)
produces more stable solutions. Upon adding a proton source, such
as an acid, the degradation of electrochemically generated
superoxide solutions accelerates.
[0167] In alternate embodiments, hydrogen peroxide may be added
from an independent source including bulk chemical concentrate
production as described in conjunction with FIGS. 1-4. Superoxide
solution 1124 may then be used as formed, or stored in holding tank
1116(1). Co-generated acid is stored in holding tank 1116(2).
Hydrogen peroxide addition form an independent source facilitates
adjustment of the molar ratio of superoxide to hydrogen peroxide in
formulations.
[0168] In step 1204, the superoxide solution 1124 is combined with
additives 1110, such as salts, co-solvents, or surfactants to
increase lifetime and working time of superoxide formulations; the
resulting solution may then be distributed to its point of use. In
step 1206, superoxide solution 1124 is combined with additives
concentrate 1126 to adjust the pH level of the superoxide for pH
sensitive applications such as groundwater and soil remediation.
The initial pH can range from pH 8 to pH 13. A preferred initial pH
range is pH 9 to pH 12. As the superoxide solution reacts and is
consumed, the pH decreases, as shown by the superoxide data
examples below, leaving a final pH closer to neutral. In step 1208,
the superoxide solution 1124 is diluted with makeup water 1104(2)
for concentration sensitive applications.
[0169] In step 1210, the electrochemical reactor 1114 creates an
output of both hydrogen peroxide and superoxide; method 1200 then
generates the hydroperoxyl radical and hydroxyl radical according
to the Equations 4-7 below.
O.sub.2..sup.-+H.sub.2O.sub.2.sup.1O.sub.2+.OH.sup.- [4]
Wherein the Haber-Weiss reaction of Equation 4 between superoxide
radical anion and hydrogen peroxide form excited state (singlet)
molecular oxygen, hydroxyl radical and hydroxide anion. Hydroxyl
radicals will react with an excess of hydrogen peroxide in an
equilibrium reaction forming water and the hydroperoxyl radical as
shown below in Equation 5:
.OH+H.sub.2O.sub.2.fwdarw.H.sub.2O+HO.sub.2. [5]
In one embodiment, hydroperoxyl radicals further subsequently react
with excess hydrogen peroxide to form water, ground state molecular
oxygen and hydroxyl radical as shown below in Equation 6:
HO.sub.2.+H.sub.2O.sub.2.fwdarw.H.sub.2O+O.sub.2+.OH [6]
[0170] In step 1210, as the superoxide solution 1124 pH decreases
the population of hydroperoxyl radical increases via the
equilibrium in Equation 7 below:
HO.sub.2..revreaction.O.sub.2..sup.-+H.sup.+ [7]
In one embodiment, hydroxyl radical evolution is most relevant at
lower concentrations of parent oxidants since hydroxyl radicals
rapidly react with the parent oxidants. In one embodiment, evolved
hydroxyl radicals initiate oxidation reactions which the parent
oxidants are not capable of, thereby enhancing the oxidative
activity.
[0171] In yet another embodiment, in step 1212, the superoxide
formulation 1124 containing hydrogen peroxide may be exposed to a
Fenton catalyst, Fenton-like catalyst, ultrasound, ultraviolet
radiation, or thermal activation (not shown in FIG. 11) to produce
radical species such as hydroxyl radicals.
[0172] Steps 1204-1212 are all optional steps as shown by the
dashed outlines. The implementation of steps 1204-1212 depends on
the application required. For example, pH sensitive uses such as
soil and groundwater remediation require diluted superoxide
solution 1124, and additional additives may be required to be
combined with the solution.
[0173] In step 1214, the superoxide solution 1124, and any
additional components combined in optional steps 1204-1212 are
distributed to the point of use. In one embodiment, the point of
use is various substrates including materials, compounds, atoms or
ions (organic or inorganic) to be reduced, oxidized or degraded and
microorganisms to be denatured or killed. In one embodiment, the
superoxide solution 1124 is used soon after its production due to
its relatively short half life determined by initial concentration,
salinity, pH, temperature and other oxidants and constituents
present. In another embodiment, the resulting superoxide solution
as distributed as superoxide reactive oxygen species output 1122 is
then used in the form of, for example, a liquid, an ice, a foam, an
emulsion, a microemulsion or an aerosol applied by means such as
injection, flooding, spraying, circulation or by any other means of
conveying a liquid.
[0174] In this invention, formulations containing both superoxide
and hydrogen peroxide are preferably prepared by electrochemical
reaction as described above. Bulk chemical mixing is not an
effective method for making such formulations. Superoxide in the
form of KO.sub.2 is commercially available, but is currently a
relatively expensive specialty chemical. Further, dissolution of
KO.sub.2 in water results in formation of oxygen, KOH and hydrogen
peroxide making the formation of superoxide/hydrogen peroxide
solutions inefficient. In contrast addition of hydrogen peroxide to
electrochemically prepared mixtures of superoxide and hydrogen
peroxide allows ready adjustment of the ratio of superoxide to
hydrogen peroxide.
[0175] The exemplary system of FIG. 5 can be adapted and employed
to prepare a superoxide+PAA formulation which generates singlet
oxygen and other reactive species (S-PM formulations). In one
embodiment, electrochemical reactor 514 is adapted to create two
outputs including superoxide with hydrogen peroxide 524 output and
acid concentrate 526 output.
[0176] In one embodiment, brine 504 is a solution that contains
ions necessary for producing alkaline superoxide with hydrogen
peroxide and acids in two separate streams. The brine 504 may also
contain pH buffers and co-solvents compatible with the reaction
process, which contribute to the reactive oxygen species output 522
formulation. For example, pH buffers include weak chemical
electrolytes chosen from the group including: acetate, citrate,
propionate, phosphate and sulfate.
[0177] Acetyl donor 510 (exemplified with acetyl, but acyl donor
can be used) includes, but is not limited to, an acyl or acetyl
donor chosen from the group including: monoacetin, diacetin,
triacetin, acetylsalicylic acid, methyl benzoate, ethyl lactate and
tetraacetylethylenediamine (TAED). In alternative embodiments,
other synthetic or natural esters, mono-, di- and triacylglycerides
and phospholipids having acyl substituents possessing more than one
carbon can provide other types of organic peracids by the
non-equilibrium reaction mechanism. Acyl or acetyl donor 510 or
mixture of donors may be in liquid or solid form, or dissolved in a
solvent when reacted with a solution of hydrogen peroxide.
Additives concentrate 512, for example, include at least one of the
following additives chosen from the group including: salts,
surfactants, co-solvents, stabilizers, and emulsifiers.
[0178] FIG. 8 shows an exemplary method 800 for generating a
diluted reactive oxygen species output 522 using system 500 of FIG.
5. In step 802, method 800 adapted for production of PAA+superoxide
formulations generates an alkaline superoxide with hydrogen
peroxide 524 output, and an acid concentrate 526 output. Acid
concentrate output 526 is then stored in holding tank 518(1). In
one embodiment, both output streams 524 and 526 are in concentrated
liquid forms produced at a constant rate. For example, the alkaline
superoxide with hydrogen peroxide 524 output may contain 0.1 wt %
to 1 wt % hydrogen peroxide and 0.1 wt % to 2 wt % superoxide at pH
12.5 to 14.0. Typical alkaline hydrogen peroxide and superoxide 525
output may contain 0.2 wt % to 0.3 wt % hydrogen peroxide and 0.5
wt % to 1.2 wt % superoxide at pH 12.8 to 13.5. The acid
concentrate 526 output may contain 0.1 wt % to 20 wt % depending on
the concentration and composition of anolyte solution makeup 742.
For example, a 20 wt % sodium acetate solution as anolyte solution
makeup 742 may produce 13.5 wt % acetic acid at 85% conversion
efficiency. In an alternative embodiment, an anolyte solution
makeup 742 is a 5 wt % sodium sulfate solution that may produce 3.6
wt % bisulfate acid at 85% conversion efficiency.
[0179] In step 804, the alkaline superoxide with hydrogen peroxide
524 output is combined with acyl or acetyl donor 510 in mixing tank
520(1) to create alkaline superoxide with peracid concentrate 524'.
In one embodiment, alkaline superoxide with peracid concentrate
524' may be superoxide with peroxyacetic acid. In one embodiment,
the acyl or acetyl donor 510 is added in proportion to the hydrogen
peroxide in the superoxide with hydrogen peroxide 524 output
solution. In one embodiment, the molar ratio of H2O2 in 524 to acyl
or acetyl donor 510 reactive group equivalents may range from 1:3
to 1:4. For example, a preferred molar ratio is 1:3 when the
alkaline superoxide with hydrogen peroxide 524 output pH is
13.0-13.4. In one embodiment, the acyl or acetyl donor is an
oxygen-acyl or oxygen-acetyl donor shown in Equation 2a below:
HOO.sup.-+AcOR.fwdarw.AcOO.sup.-+ROH [2a]
[0180] Where Ac is acyl [--C(O)R'] or acetyl [--C(O)CH3] and R and
R' are hydrocarbon-based substituents. In an alternative
embodiment, the acyl or acetyl donor is a nitrogen-acyl or
nitrogen-acetyl donor as shown in Equation 2b below:
HOO.sup.-+AcNR2.fwdarw.AcOO.sup.-+RNH [2b]
[0181] Where Ac is acyl [--C(O)R'] or acetyl [--C(O)CH3] and R and
R' are hydrocarbon-based substituents. The acetyl donor and its
reaction products and byproducts should be compatible with, or
provide synergistic behavior in combination with, superoxide.
[0182] In Equations 2a/2b above, the reaction between an acetyl or
acyl donor 510 and alkaline hydrogen peroxide 524 occurs at
alkaline pH by nucleophilic attack of the acyl carbonyl carbon atom
by the hydrogen peroxide anion, which displaces the donor molecule
fragment as an alcohol or amine in a manner analogous to
saponification. In some embodiments, the non-equilibrium reactions
generalized in Equations 2a/2b are conducted between pH 10 and pH
14.
[0183] A particular advantage of the use of non-equilibrium
reaction in Equations 2a/2b is that peracid solutions 524'' with
concentrations of less than approximately 10 wt % peroxyacetic acid
and other organic peracids or less than 5 wt % peroxyacetic acid
and other organic peracids can be produced efficiently and rapidly.
Using the non-equilibrium reaction allows the hydrogen peroxide
residual to be minimized if necessary. In one embodiment, for
example, the peroxyacetic acid water/peroxide concentration ratios
can be 10, 100, or 1000 depending on the ratio of hydrogen peroxide
to acyl or acetyl donor ratio in Equations 2a/2b. Hydrogen peroxide
is less than 3% the mass concentration of peroxyacetic acid, more
preferably less than 0.5% the mass concentration of peroxyacetic
acid, and preferably 0% the mass concentration of peroxyacetic
acid.
[0184] In one embodiment, at least one molar equivalent of acetyl
or acyl donor 510 reactive groups is added for each equivalent of
hydrogen peroxide in alkaline hydrogen peroxide anion solution 524
used in Equations 2a/2b to consume all of the hydrogen peroxide. In
alternative embodiments, excess acetyl or acyl donor 510 reactive
groups is used to minimize the hydrogen peroxide residual due to
the competing conversion of acetyl or acyl donor 510 reactive
groups to the corresponding carboxylic acid by the alkali in the
superoxide with hydrogen peroxide 524 output. The molar ratio of
hydroxide to hydrogen peroxide affects the preferred ratio of
acetyl donor reactive groups to hydrogen peroxide. For example, in
one embodiment, the preferred molar ratio of sodium hydroxide to
hydrogen peroxide is 1:1 resulting in a preferred ratio of acetyl
donor reactive groups to hydrogen peroxide of about 2:1 to ensure
the preferred low HP:PAA. In another embodiment the molar ratio of
sodium hydroxide to hydrogen peroxide is about 2:1 resulting in a
preferred ratio of acetyl donor reactive groups to hydrogen
peroxide of at least 2:1 and preferably about 2.3:1. In another
embodiment, for example where the electrochemical reactor of FIG.
11 is adapted to produce alkaline HP+superoxide in its cathode
output, the molar ratio of sodium hydroxide to hydrogen peroxide is
about 4.5:1 resulting in a preferred ratio of acetyl donor reactive
groups to hydrogen peroxide of at least 3:1. In the above examples
the ratio of acetyl donor reactive groups to hydrogen peroxide can
be increased by 2-fold or more without significantly impacting
performance.
[0185] In optional step 806, as indicated by the dashed lines,
method 800 entrains byproducts 528 produced by the reactions of
Equations 2a/2b. In one embodiment, byproducts 528 are entrained in
solution with the alkaline superoxide with peracid concentrate
524'. In one embodiment, byproducts 528 are useful as co-solvents,
pH buffers, chelating agents or stabilizers and carbon substrates
for microbial processes after a chemical oxidation process. For
example, the byproduct 528 of acetyl donors 510 of monacetin,
diacetin and triacetin is glycerol, a potential co-solvent and
favorable carbon source for microbes. In another embodiment,
byproduct 528 of acetyl donor 510* of TAED,
diacetylethylenediamine, acts as a chelating agent for transition
metal ions and potentially serves as a peroxide stabilizer. In yet
another embodiment, byproduct 528* is the carboxylic acid produced
after alkaline peracid concentrate 524' reacts with a material or
decomposes. Alternatively, acetic acid, a byproduct 528 of
peroxyacetic acid, serves as a co-solvent, a pH buffer, a chelating
agent, and a biological substrate.
[0186] In step 808, the resulting alkaline superoxide with peracid
concentrate 524' is then diluted with makeup water 502(2)
introduced by pump 516(2) to create a diluted superoxide with
peracid 524'' to nearly the point of use concentration and is
stored in holding tank 518(2)*. In optional step 810, as indicated
by the dashed outline, additional additives concentrate 512 is
combined with diluted peracid 524'' and then stored into holding
tank 518(2).
[0187] In step 812, the diluted superoxide with peracid 524''
solution pH is adjusted, by combining diluted superoxide with
peracid 524'' with created acid concentrate 526, to the activated
pH level for producing reactive oxygen species output 522*. The
resulting reactive oxygen species output 522 is then distributed to
its point of use in liquid form. The reactive oxygen species output
522 may then be used in the form of a liquid, an ice, a foam, an
emulsion, a micro-emulsion or an aerosol applied by means such as
injection, flooding, spraying, circulation or any other means of
conveying a fluid. In one embodiment, the diluted superoxide with
peracid 524'' solution pH does not require the addition of acid
concentrate 526 and is ready for immediate distribution to its
point of use.
[0188] In one embodiment, during step 812, an acid concentration
526 is combined with diluted superoxide with peracid 524'' such
that there is a population of both peracetic acid and peracetic
acid anion which react together to generate singlet oxygen
according to Equation 3 below:
AcOOH+AcOO.sup.-.fwdarw..sup.1O.sub.2+AcOH+AcO.sup.- [3]
[0189] Wherein the reaction rate for Equation 3 above follows a
second order kinetics and is maximized when the ratio of the two
forms of peroxyacetic acid is equivalent at its pKa of 8.3. The
evolution and release of singlet oxygen occurs over time ranging
from minutes to several hours depending on the rate of reaction in
Equation 3 above. In one embodiment, the evolution of singlet
oxygen from peroxyacetic acid, or other organic peracid having a
similar pKa, the pH is between 6 and 11, or between 6.5-9.5.
[0190] In one embodiment the diluted superoxide with peracid 524''
is held in Holding Tank 518(2) less than 5 minutes to utilize the
synergistic activity of superoxide combined with a peracid, singlet
oxygen and other beneficial reactive species evolved in the 524''
solution. The freshly-made diluted superoxide with peracid 524''
exhibits a significantly higher chemical reactivity than the
diluted peracid 524'' [in FIG. 5] solution without an elevated
concentration of superoxide.
[0191] In another embodiment the diluted superoxide with peracid
524'' having a pH between 6 and 11 [adjusted before entering Tank
518(2)] is held in Holding Tank 518(2) for 20 to 35 minutes before
use to allow a synergistic interaction between superoxide and
singlet oxygen in the presence of a peracid to evolve a new
reactive chemical species, complex or formulation exhibiting a
significantly elevated ORP and reduced chemical reactivity relative
to the freshly-made diluted superoxide with peracid 524'' and
relative to the diluted peracid 524'' [in FIG. 5].
[0192] In optional step 814, as indicated by the dashed outline,
the reactive oxygen species output 522* may further be activated by
means of a Fenton or Fenton-like catalyst, ultrasound, ultraviolet
radiation, or thermal activation to produce other reactive
species.
[0193] The molar ratio of superoxide to hydrogen peroxide
co-generated by the reactor can range from approximately 0.01:1 to
10:1. A preferred molar ratios ranges of superoxide to hydrogen
peroxide is 1:1 to 6:1. Another preferred molar ratio range of
superoxide to hydrogen peroxide is 3:1 to 5:1. The molar ratio
range of superoxide to hydrogen peroxide include the ranges 0.5:1
to 1.5:1, and 1.5:1 to 3:1. Electrochemically generated superoxide
solutions in the above ranges are more stable than those solutions
generated from bulk chemicals. Superoxide solutions produced from
bulk chemicals, at modestly alkaline pH's, i.e. 10-12.5 pH, contain
HOOH in equilibrium with NaOOH, causing the bulk chemical
superoxide solutions to have less stability. In contrast,
electrochemically generated superoxide solutions at pH greater than
approximately 12.6 can be made to initially contain NaOOH, which in
the presence of only NaO.sub.2 and NaOH produces more stable
solutions. Upon adding a proton source, such as an acid, the
degradation of electrochemically generated superoxide solutions
accelerates.
Definitions
[0194] Generally, terms used herein not otherwise specifically
defined have meanings corresponding to their conventional usage in
the fields related to the invention.
[0195] "Reactive Oxygen Species" means a species such as singlet
oxygen, superoxide, the hydroxyl radical and the hydroperoxyl
radical, for example. Reactive species are often characterized by
their strong oxidizing or reducing activity, high chemical
reactivity and often short or transient lifetimes in aqueous
media.
[0196] An acyl group, as known in the art, is a --C(O)R' group,
where R is generally a hydrocarbon-based group and more
specifically is an alkyl group, or aryl group (e.g., phenyl or
benzyl). An acetyl group is a type of acyl group where R' is a
methyl group, i.e., --C(O)CH.sub.3. An "Acyl donor" or particularly
an "Acetyl donor" functions to transfer an acyl or particularly an
acetyl group, respectively, to another chemical species as shown in
equations 2a and 2b above. Acyl or acetyl donors can be oxygen-acyl
or oxygen-acetyl donors as shown in Equation 2a or nitrogen-acyl or
nitrogen-acetyl donors as shown in Equation 2b above. "Acyl Donor"
includes, but is not limited to, an acetyl donor chosen from the
group including: monoacetin, diacetin, triacetin, acetylsalicylic
acid, and tetraacetylethylenediamine (TAED). Acyl donors that are
not acetyl donors include methyl benzoate and ethyl lactate. In
alternative embodiments, "Acyl Donor" may include other synthetic
or natural esters, mono-, di- and triacylglycerides and
phospholipids having acyl substituents possessing more than one
carbon which provide other types of organic peracids by the
non-equilibrium reaction mechanism. An "Acyl donor" may be capable
of reacting to transfer one or more acyl groups.
[0197] "Parent Oxidant" is generally defined as an oxidant, which
may constitute a majority or minority of the oxidant in a
formulation, from which other Reactive Oxygen Species or Other
Reactive Species are derived from. There may be more than one
parent oxidant present in an oxidizing solution. The Parent Oxidant
can transform or re-speciate in the presence of Reactive Oxygen
Species or Other Reactive Species; or the Parent Oxidant can form
complexes, clusters, ion pairs, hydrogen bonds or other
associations with Reactive Oxygen Species or Other Reactive Species
which provide synergistic properties including enhanced stability
or lifetime and increased activity or decreased activity towards
chemical and biological substrates.
[0198] "Reactive Oxygen Species" include hydroxyl radical,
superoxide, hydroperoxyl radical, hydrogen trioxide and singlet
oxygen.
[0199] "Other Reactive Species" include trioxyacetic acid,
trioxyorganoacids, organo-peroxyl radicals, acyl radical, methyl
radical, carboxyl radicals, and other radicals depending on the
parent oxidant composition, structure and reactivity.
[0200] "Catalyst" includes transition metal ions, complexes,
oxides, mixed-valence compounds, halides, sulfides, particles and
surfaces. Transition metals include copper, iron, manganese, and
any other suitable metal with chemical reactivity towards a Parent
Oxidant leading to the formation of Reactive Oxygen Species and
Other Reactive Species. Catlayst can be used to activate generation
of reactive oxygen species.
[0201] "Activating Materials" includes Catalysts, chemical
compounds, oxidants and other materials that react with the parent
oxidant in a manner that produces Reactive Oxygen Species and Other
Reactive Species.
[0202] "Activation event" or "Activation method" are events or
methods that generate one or more reactive oxygen species. An
activation event can be adjustment of pH to a selected range or the
addition of an activating material. An activation method can be
irradiation with electromagnetic radiation or application of
ultrasound, among others.
[0203] "Ultraviolet Light" includes any wavelength of light or
combination of wavelengths of light suitable for activating or
cleaving a peroxide's oxygen-oxygen bond, oxygen-hydrogen bond, or
oxygen-carbon bond thereby producing reactive radicals including
hydroxyl radical, superoxide, hydroperoxyl radical organo-peroxyl
radicals, acyl radical, carboxyl radicals, and other
oxygen-centered or carbon-centered radicals depending on the parent
oxidant composition, structure and reactivity.
[0204] Other possible activation methods:
[0205] Other types of radiation can perform similarly to
ultraviolet light activation, including ultrasound, sonic
cavitation and microwave (sonic and electromagnetic energy).
[0206] Activation can also be conducted by energy transfer from a
material (e.g., a photo-activated dye or an activated semiconductor
surface activated by light or electrical field).
[0207] Thermal activation can be used as is practiced in wet
peroxide oxidation processes.
[0208] Synergistic benefits of the activated PeroxyMax systems are
demonstrated in comparative ORP measurements, oxidation experiments
(e.g., MB oxidation assays) and biocidal data.
[0209] "Reactive groups" in association with "acetyl donor"
distinguish between those acetyl or acyl groups that will react
with alkaline hydrogen peroxide and those that are non-reactive.
One example is TAED, shown below, where only two of the four acetyl
groups are reactive.
##STR00001##
Another example is triacetin, shown below, where all three acetyl
groups are reactive.
##STR00002##
Yet another example is ethyl lactate, shown below, where only one
group is reactive.
##STR00003##
[0210] "Additives concentrate" or "Additives" means any additional
substance added to the chemical formulations described herein.
"Additives concentrate", or "additives" includes, for example, at
least one of the following additives chosen from the group
including: salts, surfactants, co-solvents, stabilizers,
emulsifiers, mineral acids, organic acids, alkali, pH buffers,
non-oxidizing molecules, ionized molecules and ionized atoms.
[0211] "Alkali concentrate" or "Alkali" includes any alkali
material. In a preferred embodiment, alkali concentrate is an
aqueous sodium hydroxide solution, or an aqueous potassium
hydroxide solution.
[0212] "Salts" include, for example, at least one salt chosen from
the group including: lithium, sodium and potassium chloride;
lithium, sodium and potassium sulfate; calcium chloride or
magnesium sulfate below pH 9; and lithium, sodium and potassium
salts of acetate, citrate, propionate, phosphate and
polyphosphates.
[0213] "Surfactants" may be anionic and nonionic for charge
compatibility and include at least one surfactant chosen from the
group including: sulfonic acid salts, alcohol sulfates, carboxylic
acid salts, fatty acids, polyether alcohols and sodium dodecyl
sulfate.
[0214] "Co-solvents" include, for example, at least one co-solvent
chosen from the group including: alcohols such as methanol,
ethanol, propanol, propylene glycol, glycol ethers, glycerol, ethyl
lactate, soybean oil, vegetable oil, sunflower oil, peanut oil and
guar gum.
[0215] "Stabilizers" include, chemical species which may be organic
or inorganic which function to stabilize a reactive species of the
formulations herein. A given stabilizer may be selected to
stabilize a parent oxidant, such as PAA or superoxide. A stabilizer
may be selected to stabilize a reactive oxygen species such as
single oxygen. Such stabilizers of parent oxidants or reactive
oxygen species are particularly useful when formulations or
formulation precursors containing parent oxidant are to be stored
or held before activation or before use. It will be appreciated
that stabilizers are intended for temporary stabilization during
such storage or to reduce the rate of reactivity, if desired for a
given application, as the reactive species in the formulations
herein are intended to react when activated to form other reactive
species or to be active for their application. A stabilizer can be
chosen from the group including: phosphoric acid, phytic acid,
tetrasodium pyrophosphate, sodium hexametaphosphate, sodium
tetrametapyrophosphate, organic phosphates, ethylenediamine
tetraacetic acid and citric acid, chelating agents, and saline
water. Useful organic phosphonates, include
diethylenetriamine-NNN'N''N''-penta(methylphosphonic acid)
commercially available as Dequest.RTM. 2060S. A stabilizer may be a
peroxide stabilizer. Chelating agents which function to chelate
metals which may be present in water, soil or other substrates to
be treated may be used to protect formulations from undesired
reaction with metals. It will be appreciated by those of ordinary
skill in the art that dilution, pH adjustment or lowered
temperature can function to stabilize parent oxidants and reactive
oxygen species.
[0216] "Emulsifiers" include, for example, at least one foaming and
antifoaming agents chosen from the group including: surfactants,
oils, co-solvents and polymers including polyethylene glycol.
[0217] "Foaming" and "antifoaming agents" include, for example,
surfactants, oils, co-solvents and polymers including polyetheylene
glycol.
[0218] "Byproducts" means any additional substance that results
from a chemical reaction. Byproducts may be useful as co-solvents,
pH buffers, chelating agents or stabilizers and carbon substrates
for microbial processes after a chemical oxidation process. For
example, the byproduct of monoacetin, diacetin and triacetin is
glycerol, a potential co-solvent and favorable carbon source for
microbes. Another example is the byproduct of TAED,
diacetylethylenediamine, which can act as a chelating agent for
transition metal ions and potentially serve as a peroxide
stabilizer. Another example of a byproduct is the carboxylic acid
produced after a peracid reacts with a material or decomposes.
Acetic acid, a byproduct of peroxyacetic acid, can serve as a
co-solvent, a pH buffer, a chelating agent, and a biological
substrate.
[0219] Oxygen-based oxidants have a wide variety of oxidation
potentials, reaction pathways, and oxidation kinetics depending on
what reactive materials are present and the conditions under which
they are used. Because of these differences the oxidation products
and oxidation byproducts will vary between oxidant type, amount
used and other conditions such as pH and temperature. Oxidation
products of organic materials are typically organic acid fragments,
small organic acids, alcohols and substituted alkanes. Complete
mineralization of organic materials to carbon dioxide and water can
occur. Often, the organic oxidation products are more readily
consumed by biological activity than the original materials.
Oxidation using formulations containing reactive oxygen species of
this invention can, for example, in an embodiment by at least
partial oxidation, facilitate biodegradation of organic
materials.
[0220] Formation of other undesirable or regulated oxidation
byproducts will depend on both the oxidant and the reactive
material(s) present that may be oxidized. Organic materials
possessing nitrogen atoms may be oxidized and release nitrate as a
byproduct. This is a particular issue during the oxidation of
natural organic material (NOM) such as humic substances and reduced
hydrocarbons from conventional oil reservoirs, oil sands and
natural gas shales.
[0221] "Hydrogen Peroxide Concentrate" typically means an aqueous
hydrogen peroxide solution. However, in alternative embodiments,
hydrogen peroxide concentrate may include other chemical forms of
hydrogen peroxide chosen from the group including: calcium
peroxide, potassium peroxide, sodium peroxide, lithium peroxide,
percarbonates, and perborates.
[0222] "Brine" contains ions necessary for producing alkaline
hydrogen peroxide and acids in two separate fluid streams, for
example. Brine may also be formulated to contain pH buffers and
co-solvents compatible with the generation process, which
contribute to the hydrogen peroxide solution formulation.
Oxidative Reduction Potential (ORP)
[0223] The oxidative reductive potential (ORP) is a measure of how
oxidizing or reducing a solution is relative to a standard
reference potential measured in volts. Standard reference
potentials are measured relative to the hydrogen/hydrogen ion
reduction-oxidation potential of 0.000 V at unit activity for the
standard hydrogen electrode (SHE). Generally, solutions with
potentials greater than 0 V vs SHE are considered oxidizing
(electron accepting) while solutions with potentials less than 0 V
vs SHE are considered reducing (electron donating). The measured
ORP of water is influenced by its pH or hydrogen ion activity. As
the hydrogen ion activity (e.g., concentration, temperature)
increases, the ORP of water increases to more positive values. ORP
is also influenced by the presence of reducing or oxidizing agents
relative to their standard reduction-oxidation potentials and
solution activities.
[0224] Standard oxidation potentials are often cited to compare the
oxidative strength of oxidants (Table 1). The standard potential is
a thermodynamic value which is always lower than the measured ORP
in solution. This difference is caused by kinetic factors, such as
the overpotential or activation barrier of electron transfer at an
electrode surface and the solution activity of the oxidant, which
is proportional to the concentration. Neither the standard
potential nor ORP reflect the chemical reactivity of an oxidant
regarding its reaction mechanism with a substrate, which is an
additional kinetic factor.
[0225] For example, according to the standard potentials (Table 1)
hydrogen peroxide is a stronger oxidant than hypochlorous acid.
However, the ORP of hypochlorous acid (29 mM) at pH 7 is over 1.1 V
(SHE)m while the ORP of hydrogen peroxide (29 mM) at pH 7 is about
0.5 V (SHE) indicating that hypochlorous acid is the stronger
oxidant. Free radicals of chlorine are strong electron acceptors
and also rapidly attack and substitute unsaturated and aromatic
hydrocarbons, amines, thiols, aldehydes, ketones, and biological
materials such as DNA and proteins. Hydrogen peroxide is a strong
electron acceptor, but it is not a free radical and is less
chemically reactive than chlorine. This difference in chemical
reactivity is reflected in the ORP. In practice, chlorine is used
as a broad-spectrum biocide in water treatment whereas hydrogen
peroxide is not. Hydrogen peroxide can be activated to form highly
reactive free radicals (i.e., hydroxyl radical, superoxide) in
various ways, e.g., by addition of a catalyst or irradiation with
ultraviolet light.
TABLE-US-00001 TABLE 1 Standard Potentials of Oxidants (values at
pH 7 unless noted) Oxidant Standard Potential (V) Hydroxyl Radical
2.80 Ozone Gas 2.07 Ozone (pH 0) 2.08 Ozone (pH 14) 1.24 Sodium
Peroxodisulfate (pH 0) 2.12 Sodium Persulfate (peroxodisulfate) 2.0
Oxone (peroxymonosulfate) 1.82 Caro's Acid (pH 0) 1.81 Peroxyacetic
Acid 1.81 Hydrogen Peroxide 1.78 Hydrogen Peroxide (pH 0) 1.80
Hydrogen Peroxide (pH 14) 0.87 Potassium Permanganate 1.68
Hypochlorous Acid 1.61 Hypobromous Acid 1.57 Chlorine Dioxide 1.57
Chlorine Dioxide (pH 0) 0.93 Chlorine Gas 1.36 Oxygen Gas 1.23
Bromine (aq) 1.07 Hypochlorite 0.81 Hypobromite 0.76 Singlet Oxygen
0.65 Superoxide -0.33
[0226] ORP is used as a general measure of the antimicrobial
strength of a solution containing an oxidizing antimicrobial agent,
biocide or disinfectant. ORP can be correlated to relative oxidant
concentration for lower oxidant concentrations at constant pH and
temperature. This feature is the basis for ORP monitoring systems
sometimes used in water treatment and disinfection processes where
oxidant dose can be adjusted to maintain a desired ORP and
corresponding biocidal activity for a particular oxidant.
[0227] Water solutions containing oxidizing biocides which have
ORP's of greater than about 650 mV (SHE) are generally considered
to be suitable for disinfection (Suslow, T. "Oxidation-Reduction
Potential (ORP) for Water Disinfection Monitoring, Control, and
Documentation" Univ. California Publication 8149
http://anrcatalog.ucdavis.edu) while ORP's above about 800 mV (SHE)
are suitable for sterilization. Below about 475 mV (SHE) there is
typically little to no biocidal activity for oxidizing biocides
even after long contact times. Known exceptions to these ORP
benchmarks include in-situ generation of short-lived reactive
oxygen species such as hydroxyl radical, by ultraviolet-activated
hydrogen peroxide, or singlet oxygen, by dye-sensitized
photo-activation of molecular oxygen.
[0228] There are several limitations to ORP measurement as a method
for evaluating antimicrobial activity. ORP is not sensitive to very
short-lived reactive oxygen species such as hydroxyl radicals,
singlet oxygen, hydrogen trioxide and hydroperoxide radical in the
presence of parent oxidants such as, for example, hydrogen
peroxide, peroxyacetic acid, molecular oxygen and ozone. ORP is not
sensitive to non-oxidizing biocides and chemical reactivity which
impart other mechanisms for disrupting cellular viability. Examples
of non-oxidizing chemical biocides include glutaraldehyde, which
acts by crosslinking protein structures, and antimicrobial
quaternary ammonium compounds, which disrupt cell membranes. ORP is
also insensitive to the tolerance of various microorganisms to a
given biocide, which affects the concentration and contact time
required to inactivate or destroy a specific microorganism. For
example, chlorine use in water treatment is not effective against
certain spores (e.g., Cryptosporidium oocysts) while chlorine
dioxide and ozone are.
[0229] In the present invention the production of reactive oxygen
species including singlet oxygen in the absence of hydrogen
peroxide, production of superoxide by electrochemical generation
and the combining of these reactive oxygen species in the presence
of hydroperoxides is conducted to produce liquid formulations with
enhanced ORP's and oxidation capabilities.
Applications of Reaction Oxygen Species Formulations
[0230] The invention provides methods of oxidation which employ
reactive oxygen species formulations as described herein. The
oxidation method includes application of one or more selected
reactive oxygen species formulations to an environment, a substrate
in an environment or to a substrate that is to be subjected to
oxidization. The terms environment and substrate are used herein
broadly to refer to a place, a material, a chemical and/or a
biological species that is to be subject to at least partial
oxidation. The environment can be, among others, water in situ, for
example, ground water, a pool, a pond, a tailing pond, an area of
contaminated soil, industrial processing equipment (e.g., pipes,
pumps, tanks and other container, filters, etc. to be cleaned
inpace). A substrate can be any item or place that are to be
oxidatively cleaned for example, containers, tanks, pipes, counter
tops, appliances, food preparation surfaces and equipment, food and
beverage containers, filters, food items during food processing,
that are subjected to oxidative cleaning. In specific embodiments,
the substrate is water containing undesirable chemical or
biological species that are to be at least in part removed by
oxidative treatment. Water to be treated includes waste water,
greywater, raw water, ground water, tailing pond water, refinery
waste water, frac flowback water, produced water, water from oil
sands extraction processes, various industrial and food processing
waters. In an embodiment, the environment or substrate is
contaminated with higher than desirable levels of microorganisms
wherein the environment or substrate is to be disinfected. The
reactive oxygen species formulations can be used as antimicrobial
agents, disinfectants and biocides. For example, the formulations
can be used for cleaning and disinfection of medical or dental
equipment, food processing equipment, containers and surfaces.
[0231] The formulations of the invention can be used in various
applications as oxidants and/or biocides. As described herein,
different formulations, as assessed by ORP measurement and dye
oxidation rate among other properties, can exhibit enhanced
activity as a chemical oxidant or as a disinfectant or biocide.
[0232] The invention provides uses of the reactive oxygen species
formulations herein for various industrial or domestic oxidation,
clean up and disinfection applications.
[0233] Exemplary non-limited applications of formulation of the
invention include: general industrial clean up, clean in place
applications, equipment cleaning, water treatment, soil treatment
and decontamination, cleaning for packing and bottling, fruit,
vegetable and other food processing (e.g., meat and fish) cleaning
and disinfection applications, food preparation cleaning and
disinfection applications, medical and dental equipment clean up
and disinfection; or bleaching applications to pulp and paper,
textiles or in laundry or related applications.
[0234] More specific applications include without limitation, Frac
flowback water treatment and reuse; produced water treatment,
refinery wastewater treatment, oilsands extraction and process
water treatment; process water cleaning and reuse, waste water
treatment, mine water treatment, cooling tower cleaning,
cleaning/disinfections of water wells, pipes and containers, flue
gas scrubbing water treatment, textile dye recycle and waste water
treatment, pulp and paper processing waste water treatment and
recycle, specialty bleaching applications, clean in place
applications in food and beverage processing, water filter
cleaning, membrane clean up, more general in situ antimicrobial
filter cleaning and disinfection, cleaning and disinfection of
vehicles, cleaning an disinfection in food preparation
services.
[0235] Formulations of the invention can be used in various
antimicrobial, disinfection and biocide applications including
without limitation: fruit and vegetable washing, meat and fish
processing and storage, food equipment clean up, water disinfection
and maintenance, pool cleaning and disinfection applications.
[0236] In various water and soil applications, it can be desirable
to employ biological treatment processes for removal of organic
contaminants. In specific embodiments, for decontamination
applications, particularly as applied to water and soil treatments,
one or more oxygen reactive species formulations of the invention
are employed to provide at least partial oxidation of more
recalcitrant organic contaminants, for example, with certain
activated formulation of the invention prior to application of
known biological treatment processes to allow for more rapid
treatment of smaller organics in the biological treatment process.
In a water treatment, contact of the water with the formulations of
the invention or activated formulations of the invention can be
configured upstream of a biological treatment process.
[0237] Reactive oxygen species formulations can be employed as an
antimicrobial agent or oxidizing agent for treatment of water,
including without limitation, process streams or waste streams.
Reactive oxygen species formulations can be used in water
treatment: to cause chemical transformation or degradation of
components or contaminants; to promote or enhance flocculation,
micro-flocculation, coagulation and subsequent clarification and
separation of inorganic and organic materials; to promote or
enhance biological treatment processes; to promote or enhance wet
peroxide oxidation processes; as a pretreatment, intermediary
treatment or post treatment process to other treatment and
separation processes.
[0238] In water treatment processes, the chlorine-free and
bromine-free reactive oxygen species formulations of the invention
can be used to provide for treatment without formation of undesired
chlorinated or brominated byproducts. In water treatment processes,
the chlorine-free and bromine-free active oxygen species
formulations of the invention can be used to provide for treatment
in the absence of chlorine dioxide and/or ozone.
[0239] In water treatment process, the reactive oxygen species
formulations of the invention can be used in place of or in
combination with wet peroxide oxidation or ultraviolet (UV)
light-activated advanced oxidation processes (AOP).
[0240] For applications of the formulations herein the formulation
is contacted with a substrate or environment to be oxidized or
treated. Any means of contacting can be employed, that is suitable
for retention of the oxidation activity of the formulation and that
is suitable for the environment and/or substrate. Formulations are
liquid and can be employed in a concentrated form or a diluted
form. Formulations can be diluted, if desired, before, during or
after initial contact. The concentration of formulations in contact
with an environment and/or substrate may be varied during
contact.
[0241] A given application may employ separate contacting events
which may be the same of different and which may employ the same
formulation or precursor formulation. A given application may
employ contact with more than one formulation or precursor thereof.
The environment and/or substrate can, for example, be contacted
with an activated liquid formulation containing reactive oxygen
species. Alternatively, the environment and/or substrate can be
contacted with a liquid precursor formulation that will generate
reactive oxygen species on activation and the formulation is
activated as or after it comes into contact with the environment or
substrate.
[0242] For example, the environment or substrate may itself provide
for activation, such as a pH adjustment to the activation pH. One
or more additional steps of activation to form additional reactive
species can occur after the contact of the formulation or the
precursor formulation with the environment and/or substrate. For
example, steps of pH adjustment may occur after contact between the
formulation and the environment or substrate. Contact with the
environment or substrate may be controlled by addition of a
selected volume or concentration of formulation or its precursor to
the environment or in contact with the substrate. Alternatively,
contact can occur by addition, including controlled addition of the
substrate to the formulation or a precursor thereof.
[0243] The time between formulation activation and contact can be
controlled. The timing of additional steps of activation can be
controlled with respect to initial contact, initial activation or
other steps of activation.
[0244] Contact can be combined with stirring or other agitation,
with scrubbing, scrapping or other abrasive method if appropriate
for the environment and/or substrate. Contact may be combined with
removal of flocculant, precipitant or other solids present or
formed in the environment or on contact with the substrate. The
environment or substrate may be pre-treated prior to contact. The
treated environment to substrate may be subject to another form of
cleaning or disinfection.
[0245] When a Markush or other grouping is used herein, all
individual members of the group and all combinations and
subcombinations possible of the group are intended to be
individually included in the disclosure. Every formulation or
combination of components described or exemplified can be used to
practice the invention, unless otherwise stated.
[0246] Without wishing to be bound by any particular theory, there
can be discussion herein of beliefs or understandings of underlying
principles relating to the invention. It is recognized that
regardless of the ultimate correctness of any mechanistic
explanation or hypothesis, an embodiment of the invention can
nonetheless be operative and useful.
[0247] One of ordinary skill in the art will appreciate that
process methods (adding, mixing, dispensing, etc.), device
elements, materials (e.g., salts, acids, bases, etc.), analytical
and spectroscopic methods, and system configurations other than
those specifically exemplified can be employed in the practice of
the invention without resort to undue experimentation. All
art-known functional equivalents, of any such methods, device
elements, materials, and configurations are intended to be included
in this invention. Whenever a range is given in the specification,
for example, range of ratios, a temperature range, a time range, or
a composition range, all intermediate ranges and subranges, as well
as all individual values included in the ranges given are intended
to be included in the disclosure.
[0248] The terms and expressions which have been employed are used
as terms of description and not of limitation, and there is no
intention in the use of such terms and expressions of excluding any
equivalents of the features shown and described or portions
thereof, but it is recognized that various modifications are
possible within the scope of the invention claimed. Thus, it should
be understood that although the present invention has been
specifically disclosed by preferred embodiments and optional
features, modification and variation of the concepts herein
disclosed may be resorted to by those skilled in the art, and that
such modifications and variations are considered to be within the
scope of this invention.
[0249] Each reference cited herein is incorporated by reference
herein in its entirety. References can be incorporated by reference
herein to provide additional description of device and system
elements, for example, electrochemical reactors, processes for use
of such device and system elements and additional applications of
the process and formulations of the invention.
EXAMPLES
Example 1
Cogeneration of Alkaline Hydrogen Peroxide and Citric Acid
[0250] A reactor system with the reactor of FIG. 6A and fluid
process flow illustrated in FIG. 4 was used in this example. The
cathode's active superficial area was approximately 255 cm.sup.2.
The anolyte reservoir and chamber were charged with a 10% weight to
volume solution of trisodium citrate in distilled water. A filtered
compressed air stream was fed into the gas feed line at a rate of 5
liters per minute at 1.3 psig. A solution of 0.05 molar sodium
sulfate and 0.01 molar sodium chloride in distilled water was fed
into the catholyte feed line at a rate of 13 mL per minute at
approximately 1.0 psig. A DC current was applied to the reactor at
5.0 amps and 4.55-4.65 volts. The catholyte output reached a steady
state composition of 720 mg/L hydrogen peroxide with a pH of 12.4
(pH measured at a 20-fold dilution) within twelve minutes of
applying the electric current and remained there at ambient
temperature near 15 degrees centigrade until the process conditions
were changed after 29 minutes. The air feed rate was then increased
to ca. 15 liters per minute at 2 psig. The catholyte inlet pressure
increased to 1.5 psig. The DC current was maintained at 5.0 amps
while the voltage increased to 4.74 volts. The catholyte output
reached a new steady state composition of 1040 to 1080 mg/L
hydrogen peroxide at a pH of 12.3 (pH measured at a 20-fold
dilution) within five minutes of changing the air feed rate until
the reactor was shut down after 46 minutes.
[0251] To the existing catholyte feed was added 0.001 molar
trisodium citrate and the reactor restarted under the previous
process conditions and nearly the same catholyte output was
achieved at 1000-1080 mg/L hydrogen peroxide at a pH of 12.3
decreasing to 12.0 (pH measured at a 20-fold dilution) during the
first 35 minutes of operation. While maintaining the current at 5.0
amps (air feed was reduced to 5 liters per minute at 46 minutes)
the pH of the catholyte output continued to decrease to a pH of
10.2 (not diluted) at 2 hours 25 minutes when the system was shut
down. The anolyte solution was drained from the reactor and had a
pH of 2.5 indicating the production of citric acid.
Example 2
Generation of Hydrogen Peroxide by Cogeneration of Alkaline
Hydrogen Peroxide and Sulfate Acids
[0252] A reactor system with the reactor of FIG. 6A and fluid
process flow illustrated in FIG. 4 was used in this example. The
cathode's active superficial area was approximately 255 cm.sup.2.
The anolyte reservoir and chamber were charged with a 1.9 L
solution of 0.25 molar sodium sulfate in distilled water, initial
pH=9.5. A ca. 93% oxygen gas stream generated by a pressure swing
adsorption oxygen concentrator was circulated through the gas feed
line at a rate of 14.5 liters per minute at 2.9 psig. A 0.02 molar
solution of sodium sulfate in distilled water was fed into the
catholyte feed line at a rate of 12.8 mL per minute at 1.5 psig. A
DC current was applied to the reactor at 7.0 amps and 3.7 volts
between anode and cathode posts. The catholyte output reached a
steady state composition of 2400 to 2450 mg/L hydrogen peroxide at
a pH of 12.5 within twenty minutes of applying the electric current
and remained there with an output product temperature of 19 to
20.degree. C. until about 60 minutes. Over the following 75 minutes
the hydrogen peroxide output concentration decreased to about 2000
mg/L with a pH of 12.5 and temperature increasing to 21.degree. C.
The process was shut down after a total operating time of 135
minutes. The total collected hydrogen peroxide product stream had a
volume of 1.7 L with a measured composition of 2300 mg/L hydrogen
peroxide at pH 12.5. The anolyte was removed from the reactor with
a volume of 1.8 L and a measured pH of 1.42 indicating conversion
of sodium sulfate to its acid forms. The hydrogen peroxide and
anolyte product streams were combined producing a pH neutralized
product with a measured composition of 1050 mg/L hydrogen peroxide
at a pH of 9.8, 0.2 pH units higher than the starting anolyte
solution, and a calculated sodium sulfate content of 0.15 M.
Example 3
Cogeneration of Alkaline Hydrogen Peroxide and Sodium
Hypochlorite
[0253] A reactor system with the reactor of FIG. 6A and fluid
process flow illustrated in FIG. 4 was used in this example. The
cathode's active superficial area was approximately 255 cm.sup.2.
The anolyte reservoir and chamber were charged with a 1.8 L
solution of 0.25 M sodium hydroxide and 0.067 M sodium chloride in
distilled water, initial pH=13.2. A ca. 93% oxygen gas stream
generated by a pressure swing adsorption oxygen concentrator was
circulated through the gas feed line at a rate of 14.5 liters per
minute at 3.0 psig. A 0.02 M solution of sodium sulfate in
distilled water was fed into the catholyte feed line at a rate of
12.8 mL per minute at 1.7 psig. A DC current was applied to the
reactor at 7.0 amps and 2.7 volts between anode and cathode posts.
The catholyte output reached a steady state composition of 2300 to
2450 mg/L hydrogen peroxide at a pH of 12.6 within twenty minutes
of applying the electric current and remained there with an output
product temperature of 19 to 21.degree. C. until the process was
shut down after 138 minutes of operation. The final output pH had
decreased slightly to 12.5. The total collected hydrogen peroxide
stream had a volume of 1.7 L with a measured composition of 2350
mg/L hydrogen peroxide at pH 12.6. The anolyte was removed from the
reactor with a volume of 1.75 L and a measured pH of 12.0. The
total chlorine content was measured to be near 40 mg/L+/-10
mg/L.
Example 4
Superoxide Production
[0254] Evidence for enhanced superoxide production was observed
using the electrochemical reactor of FIG. 6A and process flow of
FIG. 7. At 5 amps a relatively low hydrogen peroxide production
current efficiency of less than 60% is accompanied by a lower than
normal pH (e.g., 2000-2400 mg/L hydrogen peroxide and pH 12.40). As
the current density is increased to 8 amps, the hydrogen peroxide
production current efficiency decreases rapidly to less than 40%
and the pH decreases by at least 0.1 pH units (e.g., 2600 mg/L
hydrogen peroxide and pH 12.26). This change of efficiency at high
current is explained by production of superoxide. If the loss of
hydrogen peroxide production efficiency were due to current going
into the four electron reduction of molecular oxygen as shown in
Equation 8 below, or into the splitting of water as shown in
Equation 9 below, then a significant amount of hydroxide would have
been generated thereby raising the pH significantly. This was not
observed.
O.sub.2+H.sub.2O+2e.sup.-HO.sub.2.sup.-+OH.sup.- [8]
2H.sub.2O4e.sup.-+O.sub.2+4H.sup.+ [9]
Furthermore, significant electrolytic splitting of water at the
cathode would require a larger overpotential at the cathode (ca.
0.5 V more negative) and be reflected in a higher cell voltage.
However, the cell voltage remained unchanged relative to higher
efficiencies as in the examples above. Based on these data,
substantial reaction by Equation 8 or 9 does not appear to
occur.
[0255] Additional evidence in support of superoxide production is
the decoloration of methylene blue (MB) dye with the fresh cathode
output solution produced with the above characteristics. A 25 mg/L
solution of methylene blue can be decolorized to the eye, partially
within minutes and completely within 5 hours of mixing with the
aforementioned freshly produced cathode product (e.g., 2600 mg/L
hydrogen peroxide and pH 12.26). The decoloration of methylene blue
does not occur on this time scale or at all when using catholyte
product aged for at least 24 hours or using store bought hydrogen
peroxide to make a simulated catholyte product in control
experiments. The decoloration of methylene blue dye is thought to
be caused by or at least initiated by the direct action of
generated superoxide or by the evolution of hydroxyl radicals via
the Haber-Weiss reaction in Equation 4, below, over time relative
to the control experiments.
O.sub.2..sup.-+H.sub.2O.sub.2=O.sub.2+.OH+OH.sup.- [4]
Example 5
Generation of Singlet Oxygen Using Bulk Chemical Precursors
[0256] A generation system from FIG. 1 and associated method from
FIG. 2 was used to producing a singlet oxygen precursor formulation
using bulk chemical precursors. A 30 g/L aqueous hydrogen peroxide
solution 102 is pH adjusted with sodium hydroxide alkali
concentrate 104 to pH 12.0 to 12.4, using approximately 50 g sodium
hydroxide per liter of 30 g/L hydrogen peroxide. The resulting
alkaline hydrogen peroxide solution is mixed 120(1) and reacted
with an acetyl donor 106, triacetin in a ratio of 128 g triacetin
per liter of alkaline hydrogen peroxide solution. The resulting
alkaline peracid concentrate 122' will contain approximately 65 g/L
peroxyacetic acid and 0.9 g/L hydrogen peroxide, assuming 97%
conversion of the hydrogen peroxide to peroxyacetic acid. The
resulting alkaline peracid concentrate 122' will also contain about
54 g/L glycerol byproduct 124.
[0257] The peroxyacetic acid concentrate is then diluted to its
point of use concentration before or during pH adjustment to
minimize losses resulting from accelerated peroxyacetic acid
decomposition at higher concentrations when in its activated pH
range. In the present example, the above peroxyacetic acid
concentrate is diluted to 1.5 g/L, a dilution factor of 41.5 times.
The peroxyacetic acid solution is diluted with 40.5 L of make up
water 108 (e.g., fresh water or salt water) and then mixed with an
acid concentrate 112 necessary for adjusting the pH to activate
singlet oxygen evolution, where an initial pH range is between pH 8
and pH 9. For example, 12 g hydrochloric acid (100% base) is added
per 1 L of concentrate. Additionally, other additives may be added
to the solution by combining them with water 108 used to dilute
alkaline peracid concentrate 122', for example, additives can
include, for example, sodium or calcium chloride, tetrasodium
pyrophosphate, sodium lauryl sulfate and/or glycerol.
[0258] For the above exemplary singlet oxygen precursor formulation
the hydrogen peroxide stock solution, alkali types, and acid types
and other additives including salts, surfactants, co-solvents,
stabilizers, and emulsifiers can be substituted with compatible
alternatives known in the art to accommodate specific application
requirements. The resulting singlet oxygen reactive oxygen species
output 116 may then be used in the form of a liquid, an ice, a
foam, an emulsion, a microemulsion or an aerosol applied by means
such as injection, flooding, spraying, circulation or by any other
means of conveying a fluid.
[0259] The above Example 5 may also be implemented using the system
of FIG. 3 and method of FIG. 4, without diluting the alkaline
peracid concentrate 122'.
Example 6
Singlet Oxygen from Electrochemically Generated Chemicals
[0260] A generation system from FIG. 5 and associated method from
FIG. 8 was used in the present example, in an embodiment, to
produce a singlet oxygen precursor formulation using an
electrochemical generator. In the present example, the hydrogen
peroxide, alkali, and acid may be generated electrochemically and
on site as an alternative to supplying them as bulk chemicals.
Alkaline hydrogen peroxide 524 and acid concentrate 526 are
generated by electrochemical reduction. Electrochemical reduction
of oxygen is conducted at a suitable cathode and water is oxidized
at a suitable anode in an electrochemical reactor 514 in which the
anode and cathode chambers are separated by a membrane. Oxygen gas
506 and a 4 g/L aqueous sodium acetate solution 504 are supplied to
the cathode while 50 g/L aqueous sodium acetate solution 504 is
supplied to the anode. A direct current 508 is applied to the
electrodes thereby driving the reduction of oxygen at the cathode
to produce hydrogen peroxide 524 and sodium hydroxide as the
majority products from the cathode while water is oxidized at the
anode to produce acetic acid 526 and oxygen gas as majority
products from the anode.
[0261] In this example, the cathode product solution has a
composition of approximately 6 g/L hydrogen peroxide (as
H.sub.2O.sub.2), 4 g/L sodium acetate and a pH of about 12.4 (as
NaOH), assuming a 94% current efficiency for oxygen reduction to
hydrogen peroxide. The anode product solution has a composition of
approximately 31 g/L acetic acid and 7/5 g/L sodium acetate
assuming an 85% sodium acetate to acetic acid conversion. The anode
product solution volume is about 0.46 L per 1L of cathode product
solution.
[0262] The alkaline hydrogen peroxide cathode product solution is
mixed and reacted with an acetyl donor 510, for example, triacetin
in a ratio of 25.5 g triacetin per liter of alkaline hydrogen
peroxide solution 524. The resulting concentrate will contain
approximately 13 g/L peroxyacetic acid 524' and 0.17 g/L hydrogen
peroxide, assuming 97% conversion of the hydrogen peroxide to
peroxyacetic acid. The concentrate will also contain about 11 g/L
glycerol byproduct 528.
[0263] In the present example, the above peroxyacetic acid
concentrate 524' is diluted to 1.5 g/L, a dilution factor of 8.7
times. Dilution is achieved by diluting the acidic anode product
solution with 7.24 L of water 502(2) (e.g., fresh water or salt
water). Additional additives 512 can also be added, such as sodium
or calcium chloride, tetrasodium pyrophosphate, sodium lauryl
sulfate, and glycerol. The solution is then combined with acid
concentrate 526 to produce a singlet oxygen reactive oxygen species
output 522 with a pH in the range of pH 8 to pH 9.
[0264] For the above exemplary singlet oxygen precursor formulation
the hydrogen peroxide stock solution, alkali types, and acid types
and other additives including salts, surfactants, co-solvents,
stabilizers, and emulsifiers can be substituted with compatible
alternatives known in the art to accommodate specific application
requirements. The resulting singlet oxygen reactive oxygen species
522 may then be used in the form of a liquid, an ice, a foam, an
emulsion, a microemulsion or an aerosol applied by means such as
injection, flooding, spraying, circulation or by any other means of
conveying a fluid.
[0265] The above Example 6 may also be implemented using the system
of FIG. 9 and method of FIG. 10, without diluting the peroxyacetic
acid concentrate 524'.
Example 7
Electrochemical Generation of H.sub.2O.sub.2 as a "Control" for
Superoxide Production Experiments (Experiments 8-9)
[0266] A reactor system with an electrochemical reactor of FIG. 6
and fluid process flow illustrated in FIG. 7 was used in this
example. A carbon fiber cathode suitable for high efficiency
hydrogen peroxide production was installed in the reactor with an
active superficial area of 255 cm.sup.2. The anolyte reservoir and
chamber were charged with a 2.5 L solution of about 1.5 M sodium
hydroxide in distilled water. The anolyte was recirculated through
the anode chamber over time. A ca. 93% oxygen gas stream generated
by a pressure swing adsorption oxygen concentrator at about 5 L per
minute was circulated through the gas feed line and reactor by a
pump at a rate of 10 liters per minute at 2.6 psig while a 5 L per
minute bleed stream of oxygen gas was released from the system. The
catholyte was a 0.05 M solution of sodium sulfate in distilled
water adjusted to pH 11.2 with sodium hydroxide to precipitate
trace magnesium in the electrolyte. The catholyte solution was fed
into the catholyte feed line at a rate of 12.8 mL per minute at 1.3
psig (single pass, flow through). A DC current was applied to the
reactor at 5.0 amps (current control). The negative pole of the
power supply was grounded. Hydrogen peroxide concentration was
analyzed by titration using a Hach Inc. HYP-1 Hydrogen Peroxide
Test and pH was measured using an Oakton pH 11 Series meter with a
temperature compensated double junction pH electrode.
[0267] The catholyte output reached a steady state composition of
3700+/-50 mg/L hydrogen peroxide and pH 12.25+/-0.04 at 25 to
26.degree. C. The current efficiency for hydrogen peroxide
production was calculated to be 90.8% assuming a two electron
reduction of molecular oxygen.
Example 8
Superoxide Generation Using Electrochemical Reactor
[0268] A generation system from FIG. 11 and associated method from
FIG. 12 was used in the present example to show an exemplar of
producing a superoxide precursor formulation using an
electrochemical generator, in one embodiment. Superoxide
concentrate 1124 and, optionally, acid concentrate 1126 are
electrochemically generated using an electrochemical reactor 1114.
Electrochemical reduction of oxygen is conducted at a suitable
cathode and water is oxidized at a suitable anode in an
electrochemical reactor 1114 in which the anode and cathode
chambers are separated by a membrane. Oxygen gas 1106 and a 4 g/L
aqueous sodium acetate solution 1104 are supplied to the cathode,
while a 50 g/L aqueous sodium acetate solution 1104 is supplied to
the anode. A direct current 1108 is applied to the electrodes
thereby driving the reduction of oxygen at the cathode to produce
superoxide, hydrogen peroxide and sodium hydroxide as the majority
products 1124 of the cathode, while water is oxidized at the anode
to produce acetic acid and oxygen gas as the majority products 1126
of the anode.
[0269] In this example, the cathode product solution 1124 has a
composition of approximately 3.0 g/L superoxide (as
O.sub.2..sup.-), 3.2 g/L hydrogen peroxide (as H.sub.2O.sub.2), 4
g/L sodium acetate and a pH of about 12.2 (as NaOH), assuming a 90%
current efficiency for oxygen reduction to superoxide and hydrogen
peroxide. The anode product solution 1126 has a composition of
approximately 31 g/L acetic acid and 7.5 g/L sodium acetate
assuming 85% sodium acetate to acetic acid conversion. The anode
product solution volume is about 0.46 L per 1 L of cathode product
solution.
[0270] The superoxide-containing cathode product solution 1124 is
then diluted to its point of use concentration before or during pH
adjustment to minimize losses resulting from accelerated superoxide
decomposition at lower pH. In this example, the superoxide is
diluted to 1.0 g/L, a dilution factor of 3 times. In one example,
dilution can be achieved by diluting the acidic anode product
solution with 1.54 L of water (e.g., fresh water or salt water),
adding other desirable additives to the diluted anode product
solution and then combining the diluted anode product solution with
the superoxide-containing cathode product solution. Examples of
additives include sodium chloride, sodium lauryl sulfate,
isopropanol and soybean oil.
[0271] Due to the decreasing lifetime of superoxide in aqueous
media as the pH becomes less alkaline, non-aqueous co-solvents or
emulsion compositions may be employed to improve the lifetime and
activity of superoxide solution 1124. Alternatively, the alkaline
superoxide-containing cathode product solution may be utilized
directly, followed by pH neutralization or adjustment with the
acidic anode product solution.
[0272] For the above exemplary singlet oxygen precursor formulation
the hydrogen peroxide stock solution, alkali types, and acid types
and other additives including salts, surfactants, co-solvents,
stabilizers, and emulsifiers can be substituted with compatible
alternatives known in the art to accommodate specific application
requirements. The resulting singlet oxygen reactive oxygen species
1122 may then be used in the form of a liquid, an ice, a foam, an
emulsion, a microemulsion or an aerosol applied by means such as
injection, flooding, spraying, circulation or by any other means of
conveying a fluid. The above example may also be implemented
without diluting the superoxide solution 1124.
Example 9
Dye Oxidation with Singlet Oxygen
[0273] Methylene blue (MB) is a heterocyclic aromatic compound with
the molecular formula C.sub.16H.sub.18N.sub.2SCl and is
considerably resistant to oxidation. MB is a useful model dye for
comparing the oxidative strengths of various oxidizers based on the
rate of color loss from solutions when treated. Methylene blue
dissolved in water has an intense absorption band maximum near 662
nm in the visible part of the electromagnetic spectrum resulting in
its intense blue color. Observing the loss of this absorption and
blue color by oxidation of the dye provides a preliminary
comparison between oxidizers. Observing can be done by an observer
noting color change, particularly using color standards, or by use
of appropriate spectrometric measurement.
[0274] A series of MB oxidation trials were conducted near room
temperature (17-22.degree. C.) by combining equal volumes of
oxidant formulations with 100 mg/L MB stock solution resulting in a
50 mg/L MB initial concentration. The change in MB solution color
was evaluated over time by visual comparison to a series of color
standards made by serial dilution of the same 100 mg/LMB stock
solution. Color standards were 50, 25, 10, 5, 1, and 0.5 mg/L MB.
Color comparisons were made with test samples and color standards
contained in 12 mm inner diameter Pyrex test tubes positioned in
front of a back-lit, diffuse white field. Solution pH and
temperature was measured with a temperature compensated pH
electrode using an Oakton pH11 meter with three point calibration.
Hydrogen peroxide concentration was measured using the HACH
hydrogen peroxide test method based on ammonium molybdate-catalyzed
triiodide titration with sodium thiosulfate.
[0275] The following bulk chemical reagents were purchased and used
as received: Triacetin, 99%,(Acros Organics); Methylene Blue, 1%
w/v aqueous solution (Ricca Chemical Company); Hydrogen peroxide,
2.7% w/v (measured)(Kroger Co.); Sodium Hydroxide, 100% (Rooto
Corp.); Sodium Sulfate, 100% anhydrous (Duda Diesel); and Distilled
water from Kroger Co.
[0276] For example, electrochemically generated hydrogen peroxide
concentrate solution was produced one to three days prior to use
and stored at 2-4.degree. C. in a high density polyethylene bottle.
The composition of the electrochemically generated hydrogen
peroxide solution in distilled water at room temperature was 4800
mg/L (+/-50 mg/L) hydrogen peroxide, pH 12.81 (+/-0.04) as sodium
hydroxide, and 7.1 g/L sodium sulfate. Hydrogen peroxide
concentration was stable for several days.
[0277] Electrochemically co-generated sulfate acid concentrate with
pH 1.40 (+/-0.04) was produced from a 0.31 molar (44.0 g/L) sodium
sulfate brine in distilled water. The approximate calculated
composition of the acid concentrate at 20.degree. C.
(pKa.apprxeq.0.973) was 0.091 M sodium sulfate and 0.24 M sodium
bisulfate.
[0278] Peroxyacetic acid formulations were made by mixing
electrochemically generated hydrogen peroxide solution with
tiacetin as the acetyl donor. The molar ratio of hydrogen peroxide
to acetyl donor group was adjusted to produce non-equilibrium
perxyacetic acid solutions. The triacetin molecule possesses three
molar equivalents of acetyl groups. A 2.00 mL volume of the oxidant
formulation was combined with 2.00 mL of 100 mg/L MB aqueous
solution. The initial pH was then adjusted by quickly titrating in
electrochemically generated sulfate acid concentrate in amounts
less than 0.5-2% of the total solution volume. The initial
concentration of peroxyacetic acid was estimated based on the
initial hydrogen peroxide concentration. The amount of unreacted
hydrogen peroxide residual was not measured, but its effect was
observed in the percent color removal results.
[0279] Table 2 below represents examples of MB oxidation test
results demonstrating the relative effects of oxidant, pH,
concentration and molar ratio of acetyl donor groups reacted with
hydrogen peroxide. The initial MB concentration was 50 mg/L in all
cases. Entry 1 used commercially produced hydrogen peroxide as the
parent oxidant near neutral pH without adjustment. Entry 2 used
electrochemically generated hydrogen peroxide at high strength
without pH adjustment. Entry 3 used commercially produced hydrogen
peroxide reacted with triacetin near pH 12.2, a known amount of
hydrogen peroxide was added and then pH adjusted with
electrochemically generated sulfate acid concentrate. Entries 4-13
used electrochemically generated hydrogen peroxide reacted with
triacetin and diluted to varying initial concentrations of
peroxyacetic acid as the parent oxidant.
[0280] The results in Table 2 demonstrate, for example, that
singlet oxygen evolving formulations are significantly stronger
oxidants than hydrogen peroxide or peroxyacetic acid solutions
alone. Hydrogen peroxide by itself did not have any observed
effects during this test and after the test solution in Entry 1 had
sat for several days. Alkaline hydrogen peroxide in Entry 2
eventually caused a small amount of MB to precipitate after several
hours more and has a slight shift in solution color to a purple
hue, but color loss did not progress significantly. A control test
with 50 mg/L MB without any oxidant, but in the presence of 1M
sodium hydroxide gave a similar result to Entry 2, indicating that
hydrogen peroxide had little or no effect on the observed changes.
Entry 3 demonstrates that the presence of a significant
concentration of hydrogen peroxide in the peroxyacetic acid
formulation severely inhibits oxidative activity toward MB and
color removal.
TABLE-US-00002 TABLE 2 MB Oxidation Test Results Molar reaction
ratio, Final % Color Entry HP:acetyl Initial Conc., Initial Final
Time Re- no. equiv. Parent Oxidant pH pH (h) moval 1 1:0 50 mg/L,
HP 6.1-6.4 NR 3 0 2 1:0 2150 mg/L, HP 12.0-12.2 NR 3 0 3 1:2 7000
mg/L, PAA 9.00 NR 48 <10 5000 mg/L, HP 4 1:1 <240 mg/L, PAA
3.54 3.71 7 0 5 1:1 <240 mg/L, PAA 8.55 6.93 7 25 6 1:2 240
mg/L, PAA 4.50 4.55 8 0 7 1:2 240 mg/L, PAA 9.00 7.90 8 65 8 1:4
240 mg/L, PAA 4.60 4.73 7 0 9 1:4 240 mg/L, PAA 8.49 7.75 7 50 10
1:2 465 mg/L, PAA 3.97 3.70 7 20 11 1:2 465 mg/L, PAA 9.01 7.99 7
82 12 1:2 950 mg/L, PAA 9.01 8.16 7 93 13 1:2 1900 mg/L, PAA 9.00
8.46 5 99.5 HP = hydrogen peroxide; PAA = peroxyacetic acid; NR =
not recorded
[0281] Entries 5, 7 and 9 in Table 2, above, demonstrate the effect
of HP:acetyl donor equivalent ratio on oxidation activity as
impacted by hydrogen peroxide residual, which leads to inhibited
oxidative activity presumably due to singlet oxygen quenching. When
the HP:acetyl donor equivalent ratio is 1:1, the MB color loss is
significantly lower than when the ratio is 1:2 or 1:4. The
difference in results between HP:acetyl donor equivalent ratios of
1:2 and 1:4 is minimal, when normalized to reaction time indicating
that an excess of acetyl donor is not necessarily detrimental to
oxidative activity.
[0282] When the initial peroxyacetic acid solution pH was above 8
the oxidation and color loss of MB was observed (Table 2). When the
initial peroxyacetic acid solution pH was below 5, there was little
to no color loss observed. When the pH remained above approximately
6.5 an increase in the peroxyacetic acid concentration resulted in
faster and greater color loss of MB. This trend is demonstrated by
the results in graph 1300 of FIG. 13 showing the percent color
removal of 50 mg/L MB solutions observed over time starting with
different initial peroxyacetic acid concentrations. The results in
graph 1300 of FIG. 13 also demonstrate that the singlet oxygen
evolution occurs over a period of several hours. This result is
reinforced by the observation of gas bubble evolution, which
persists for several hours when the initial peroxyacetic acid
concentrations are significantly greater than 1900 mg/L.
Example 10
pH Control and Formulation of Nitrate Oxidation Byproduct
[0283] As materials are oxidized and the peroxyacetic acid
transforms to acetic acid, the pH of the treatment solution
decreases. The initial pH and/or pH buffer concentration of the
singlet oxygen precursor solutions should be adjusted to control
the change in pH during the active oxidation period, such that the
final pH is in a desirable range. Table 3 shows oxidation results
for raw hydraulic fracturing and flowback water with singlet oxygen
precursor formulations. Data in Table 3, below, demonstrate how the
initial pH, the amount of parent oxidant and the amount of
oxidation can be used control the final pH of the oxidized water.
This example also illustrates the production of nitrate as a
byproduct of the oxidation of nitrogen-containing organic materials
with singlet oxygen formulations.
TABLE-US-00003 TABLE 3 Oxidation Results For Raw Hydraulic
Fracturing and Flowback Water Total Final Raw oxi- Initial (6 h)
water dation oxi- oxi- Nitrate Sample PAA:TOC volume volume dation
dation byproduct No. mass ratio (mL) (mL) pH pH (mg/L) 1 .sup. 0:1
37 56.7 8.19 8.19 BDL 2 2.4:1 37 56.7 8.87 6.73 0.92 3 1.2:1 37
56.7 8.77 6.81 0.52 4 0.6:1 37 56.7 8.67 7.00 0.31 BDL = below
detection limit of 0.1 mg/L
[0284] Raw hydraulic fracturing and flowback water generated by oil
and gas development operations was obtained from an undisclosed
location in Colorado, USA after temporary impoundment in a lagoon.
The composition of the raw water was approximately 5000 mg/L total
organic carbon (hereinafter "TOC"), approximately 10,000 mg/L total
dissolved solids (hereinafter "TDS"), appeared opaque with
suspended silt and dark brown organic material and had a pH of 8.19
indicating alkalinity content. The raw water also possessed a mild
odor of volatile organic compounds (i.e., petrochemicals).
[0285] Singlet oxygen formulation concentrate, formulated by the
above embodiments, was added to the raw water in varying amounts
with distilled water added to maintain equivalent dilutions between
samples. The approximate mass ratios of peroxyacetic acid to TOC
are reported in Table 3, above, to distinguish singlet oxygen
precursor doses. The singlet oxygen precursor formulation was made
by mixing and reacting 1.40 mL triacetin with 16.3 mL of a 1% w/v
hydrogen peroxide stock solution adjusted to pH 12.4 with NaOH. The
resulting peroxyacetic acid solution concentrate was adjusted to pH
8.9 with about 2.0 mL of electrochemically generated sulfate acid
concentrate of pH 1.32. The samples in Table 3, above, were
prepared by mixing 37 mL of raw water with: 19.7 mL of distilled
water for control sample no. 1; 19.7 mL of singlet oxygen precursor
formulation for sample no. 2; 9.8 mL of singlet oxygen precursor
formulation plus 9.8 mL distilled water, for sample no. 3; and 4.9
mL of singlet oxygen precursor formulation plus 14.8 mL distilled
water, for sample no. 4. The samples were each contained in 100 mL
glass jars at room temperature.
[0286] The initial pH was measured immediately after sample
preparation. The initial pH was affected by the amount of singlet
oxygen precursor formulation added to the sample. Samples
containing singlet oxygen precursor formulation evolved gas rapidly
enough to effervesce for 1-2 hours. Effervescence also served as an
effective mixing mechanism. Within the first 30 minutes of
oxidation, the color of sample nos. 2-4 had become paler, than the
control sample no. 1. After 5-6 hours visible gas evolution had
subsided and the oxidized samples were a significantly paler tan
color than the control. Sample no. 2 was the palest in color
corresponding with the greatest singlet oxygen precursor dose.
[0287] The final pH was measured at 6 hours. Higher initial singlet
oxygen precursor formulation concentration led to lower final pH.
Oxidized samples had a final pH of 6.7 to 7.0 demonstrating the
potential to balance pH with the singlet oxygen precursor
formulation and dose. The precursor formulation used in this
example contained acetate and acetic acid, which can act as a pH
buffer and reduce alkalinity, respectively. As oxidation proceeded,
additional acetic acid (the byproduct from peroxyacetic acid
reactions) and potentially partial oxidation products with
carboxylic acid groups accumulated leading to a decrease in pH over
time.
[0288] Nitrate was found to be an oxidation byproduct of the
organic material in the hydraulic fracturing flowback water.
Results of ion chromatography analysis of the samples in Table 3,
above, corrected for dilution, show that byproduct nitrate content
was proportional to singlet oxygen precursor formulation
concentration. Nitrogen-containing materials, such as natural
organic materials, were sufficiently oxidized to liberate nitrogen
as nitrate. Nitrate was not detected in the non-oxidized raw
water.
[0289] In view of the many possible embodiments to which the
principles of the disclosure may be applied, it should be
recognized that the embodiments herein should not be taken as
limiting the scope of the present disclosure.
Example 11
Electrochemical Co-Generation of Hydrogen Peroxide and
Superoxide
[0290] A reactor system with an electrochemical reactor of FIG. 6
and fluid process flow illustrated in FIG. 7 was used in this
example. A carbon fiber cathode suitable for combined hydrogen
peroxide and superoxide production was installed in the reactor
with an active superficial area of 255 cm.sup.2. The anolyte
reservoir and chamber were charged with a 2.5 L solution of about
1.5 M sodium hydroxide in distilled water. The anolyte was
recirculated through the anode chamber over time. A ca. 93% oxygen
gas stream generated by a pressure swing adsorption oxygen
concentrator at 5 L per minute was circulated through the gas feed
line and reactor by a pump at a rate of 9.0 liters per minute at
3.0 psig, while a 5 L per minute bleed stream of oxygen gas was
released from the system. The catholyte was a 0.05 molar solution
of sodium sulfate in distilled water adjusted to pH 11.2 with
sodium hydroxide to precipitate trace magnesium in the electrolyte.
The catholyte solution was fed into the catholyte feed line at a
rate of 12.8 mL per minute at 1.6 psig (single pass, flow through).
A DC current was applied to the reactor at either 5.0 amps or 8.0
amps (current control). The negative pole of the power supply was
grounded. Hydrogen peroxide concentration was analyzed by titration
using the Hach Inc. HYP-1 Hydrogen Peroxide Test and pH was
measured using an Oakton pH 11 Series meter with a temperature
compensated double junction pH electrode.
[0291] At 5.0 amps operating current the catholyte output reached a
steady state composition of 2000+/-50 mg/L hydrogen peroxide and pH
12.20+/-0.04 at 25 to 27.degree. C. The current efficiency for
hydrogen peroxide production was calculated to be 48.4% assuming a
two electron reduction of molecular oxygen. A maximum potential
concentration of superoxide anion produced was calculated to be
3400 mg/L, assuming 90% of the balance of the applied current
caused the one electron reduction of molecular oxygen.
[0292] At 8.0 amps operating current, the catholyte output reached
a steady state composition of 2500+/-50 mg/L hydrogen peroxide at
27 to 28.degree. C. and pH 12.58+/-0.04 measured at a 10-fold
dilution to adjust the pH to within the accurate range of the pH
probe. The current efficiency for hydrogen peroxide production was
calculated to be 37.8%, assuming a two electron reduction of
molecular oxygen. A maximum potential concentration of superoxide
anion produced was calculated to be 6800 mg/L assuming 90% of the
balance of the applied current caused the one electron reduction of
molecular oxygen.
Analysis of Electrochemically Generated Hydrogen Peroxide and
Superoxide (Examples 7 and 11):
[0293] Catholyte outputs from Examples 7 and 11 above were analyzed
by ultraviolet-visible absorption spectroscopy between 21 and
24.degree. C. Data was collected using an Ocean Optics
USB4000-UV-VIS absorbance system (200-850 nm) with SpectraSuite
software. Disposable 1 cm Plastibrand disposable macro cuvettes
were used with a 220 nm cutoff. Hydrogen peroxide concentration was
analyzed by titration using the Hach Inc. HYP-1 Hydrogen Peroxide
Test and pH was measured using an Oakton pH 11 Series meter with a
temperature compensated double junction pH electrode. All samples
were diluted with distilled water to 100 mg/L hydrogen peroxide and
pH adjustments were made using sodium hydroxide or pH 1.40 sodium
bisulfate solution. Hydrogen peroxide UV standards were made from
3% topical hydrogen peroxide and sodium hydroxide combined in
distilled water. Standards included 100 mg/L hydrogen peroxide at
pH 6.7, 10.0, 11.0 and 12.0. Standards were also made with 0.10
mol/L NaOH (nominally pH 13) and 1.0 mol/L NaOH (nominally pH 14)
measured by weight of sodium hydroxide dissolved in distilled water
at room temperature.
[0294] The previously reported absorption band maximum for dilute
aqueous superoxide generated by radiolysis of dissolved oxygen in
the presence of sodium formate and ethylenediaminetetraacetic acid
at pH 10.5 was 245 nm. See "Reactivity of HO.sub.2/O.sub.2.sup.-
Radicals in Aqueous Solution," Beilski, et al., J. Phys. Chem. Ref.
Data, Vol. 14, No. 4, 1985. The reported absorption band maximum
for dilute hydroperoxyl radical (HO.sub.2.) in aqueous perchloric
acid at pH 1.5 was 225 nm.
[0295] FIGS. 14A/B shows graphs 1400, 1450 that compares the UV
absorbance spectra of fresh catholyte outputs, within 2 minutes of
production, of the high efficiency hydrogen peroxide output 1402 in
Example 7, and the co-generated hydrogen peroxide and superoxide
output 1404 in Example 11. Both outputs were produced at 5
amps.
[0296] FIG. 14A shows graph 1400 that illustrates the full spectra
of samples diluted to 100+/-4 mg/L hydrogen peroxide and adjusted
to pH 12.00+/-0.04 and graph 1450 of FIG. 14B shows the same
spectra with hydrogen peroxide absorbance subtracted off. The
co-generated hydrogen peroxide and superoxide output exhibits
additional absorbance intensity on the shorter wavelength side of
the hydrogen peroxide band and a weak absorbance band in the
subtracted spectrum. The high efficiency hydrogen peroxide output
did not exhibit a second absorbance band after subtracting off the
hydrogen peroxide absorbance. Hydrogen peroxide at 100+/-4 mg/L and
pH 12.0 has an absorbance maximum near 232 nm, while the weak
absorbance band of the co-generated hydrogen peroxide and
superoxide output is shifted to shorter wavelength.
[0297] The weak absorbance band of the co-generated hydrogen
peroxide and superoxide output increases in intensity over time at
pH 12, which is behavior not observed for alkaline hydrogen
peroxide alone.
[0298] FIGS. 15A/B show graphs 1500, 1550 that illustrate the
evolution of the UV absorbance spectrum over five hours for the
co-generated hydrogen peroxide and superoxide output produced at 8
amps in Example 11 diluted to 100+/-4 mg/L hydrogen peroxide,
adjusted to pH 12.00+/-0.04 and analyzed over time. Graph 1500
shows the full spectra of the output including hydrogen peroxide at
two minutes after production 1502, three hours after production
1504 and five hours after production 1506. Graph 1550 shows the
same spectra with hydrogen peroxide absorbance subtracted off at
two minutes after production 1552, three hours after production
1554, and five hours after production 1556. The growing band in
graph 1550 has an absorbance maximum near 224 nm at five hours,
which is consistent with the reported position of the hydroperoxyl
radical. The original spectrum in graph 1500 shows an 18% decrease
in absorbance and a shift in the absorbance band maximum from 230
nm, to 228 nm at three hours, to 226 nm at five hours. These
spectral changes were accompanied by a decrease in pH to
11.66+/-0.04, but there was no measurable decrease in hydrogen
peroxide concentration. The aforementioned behavior is consistent
with the buildup of a different species with lower molar
absorptivity by a slow chemical reaction or equilibrium process and
a slow loss of a non-hydrogen peroxide species in the
electrochemically generated output.
[0299] For comparison, the same output produced at 8 amps in
Example 11, diluted to 100+/-4 mg/L hydrogen peroxide and adjusted
to pH 13 (0.10 mol/L NaOH) did not exhibit any change in the 224 nm
hydrogen peroxide subtracted peak intensity or hydrogen peroxide
concentration over 5 hours (data not shown). The original spectra
did show a 10% decline in peak intensity of the hydrogen peroxide
peak near 231 nm over five hours without any wavelength shift in
peak maximum position. This behavior shows a more stable output
solution with a slower loss of a non-hydrogen peroxide species in
the electrochemically generated output.
[0300] FIGS. 16A/B show graphs 1600, 1650 that illustrates the
evolution of the UV absorbance spectrum over five hours for the
co-generated hydrogen peroxide and superoxide output produced at 8
amps in Example 11 diluted to 100+/-8 mg/L hydrogen peroxide,
adjusted to pH 11.04+/-0.04 and analyzed over time. Graph 1600
shows the full spectra of the output including hydrogen peroxide at
two minutes after production 1602, one and a half hours after
production 1604 and five hours after production 1606. Graph 1650
shows the same spectra with hydrogen peroxide absorbance subtracted
off at two minutes after production 1652, one and a half hours
after production 1654, and five hours after production 1656. The
221 nm band in graph 1650 increases in intensity for a period of
time, then decreases in intensity. The original spectrum in graph
1600 shows a 56% decrease in absorbance and a shift in the
absorbance band maximum from 225 nm to 222 nm at five hours. These
spectral changes were accompanied by a decrease in pH to
9.47+/-0.04 and a 20% decrease in hydrogen peroxide concentration
to 80+/-4 mg/L. Approximately 55-60% of the decrease in absorbance
in graph 1600 is attributable to the decrease in pH. In graph 1650
the initial spectrum of the output shows a broad absorption
shoulder in the 240 to 260 nm region, which is consistent with the
absorption region for the "free" form of dilute, aqueous
superoxide. This shoulder is often observed for freshly made
reactor output solutions. These results show that a lower initial
pH leads to a more reactive and less stable output solution
including the formation of a different species with lower molar
absorptivity than hydrogen peroxide; a more rapid loss of this
different species involving the consumption of hydrogen peroxide;
and a more rapid loss of a non-hydrogen peroxide species in the
electrochemically generated output.
[0301] The UV spectra of co-generated hydrogen peroxide and
superoxide outputs show that the initially generated alkaline
hydrogen peroxide changes in form in the presence of superoxide,
especially when the pH is near or below hydrogen peroxide's pKa of
11.6. Likewise, the "free" form of superoxide is quenched by the
presence of hydrogen peroxide, especially at high concentrations.
Hydrogen peroxide has been reported to behave as a stabilizing
co-solvent which increases the chemical reactivity of aqueous
superoxide solutions. See "Identification of the Reactive Oxygen
Species Responsible for Carbon Tetrachloride Degradation in
Modified Fenton's Systems," Watts, et al., Environmental Science
& Technology, Vol. 38, No. 20, 2004. Hydrogen peroxide is a
weak acid and can potentially serve as a proton source for
superoxide, which has a pKa of 4.8. Based on the UV spectra it
appears that hydrogen peroxide in its fully protonated form can
interact with superoxide to form a different species, such as, for
example, an "adduct," in an equilibrium process and/or lead to the
reactions in Equations 1 and 3. At pH 11 hydrogen peroxide is
consumed more rapidly, consistent with the processes in Equations 1
and 3, which produce hydroxyl radicals. A measurable increase in
the concentration of hydrogen peroxide and pH over time was never
observed, indicating that the disproportionation reaction in
Equation 6 was negligible for the reactor output.
[0302] The stability of the co-generated hydrogen peroxide and
superoxide output solutions was significantly greater than the
lifetimes cited earlier, 1.5 minutes at pH 11 and 41 minutes at pH
12.5 in aqueous solution. The lifetimes of active species at pH 12
and higher were at least five hours in the diluted reactor output
solutions. The stability of the concentrated, undiluted output
solutions was lower as evidenced by gas bubble evolution observed
after approximately 30 minutes time. At pH 11 the degradation of
active oxygen species was accelerated, but persisted for at least
five hours in the diluted reactor output solutions. Enhanced
oxidation activity, of these output solutions was demonstrated to
persist for more than 12 hours at pH 11-12 in the example cited
below.
Example 12
Advanced Oxidation of Methylene Blue with Electrochemically
Co-Generated Hydrogen Peroxide and Superoxide
[0303] Catholyte output solution was generated by the method cited
in Example 11 at 5 amps operating current. Output solution
contained 2500+/-50 mg/L hydrogen peroxide and a calculated maximum
potential concentration of 3050 mg/L superoxide at pH 12.1. Freshly
generated output solution (2.0 mL) was added to 2.0 mL of 100 mg/L
methylene blue solution acidified with bisulfate. The prepared
oxidation test solution had an initial pH of 11.9 and contained 50
mg/L methylene blue, 1250 mg/L hydrogen peroxide, a maximum
potential superoxide concentration of 1500 mg/L. Solution
temperature was 25.degree. C. The methylene blue color was
evaluated over time by comparison to the series of methylene blue
color standards as described in Example 9. A slight decrease in
color intensity, ca. 10%, was observed after 5.6 hours had passed
without a significant change in pH. The solution was colorless to
the eye after 50 hours. For comparison, hydrogen peroxide alone had
no visible effect on methylene blue after several days.
Example 13
Singlet Oxygen Formulation for In-Situ Chemical Oxidation
[0304] Singlet oxygen may be used for remediation and
decontamination of a body of soil, a geologic formation, an
excavated soil, or construction or demolition debris.
[0305] A singlet oxygen formulation is prepared from bulk
chemicals, formulated using the system and methods depicted in
FIGS. 3 and 4, for in-situ chemical oxidation (ISCO) for
remediation of soil contaminated with diesel fuel (60 mg/kg) and
polycyclic aromatic hydrocarbons (PAH's, 40 mg/kg). The resulting
singlet oxygen formulation can be used to oxidize 85-95% of the
contaminants, oxygenate the soil and supply non-toxic, low
molecular weight organic substrates to heterotrophic bacteria which
may consume residual contaminants and their oxidation byproducts.
The present example applies to a soil sample having soil porosity
of 20%, soil pH 8.0-8.5, and soil density of 2.4 g/cm.sup.3. The
soil type is clayey with low vapor permeability, the depth of
contamination is up to 4 meters. The method can employ injection
and recovery wells.
[0306] Chemical feeds are prepared using the system 300 of FIG. 3
and method 400 of FIG. 4. Application includes applying six soil
pore volumes of oxidant formulation containing a 4:1 mass ratio of
peroxyacetic acid to contaminant to set the singlet oxygen dose,
and a treatment rate of 32 cubic yards per day. Chemical inputs on
a 100% basis are 24.3 lb/day hydrogen peroxide, 40.7 lb/day sodium
hydroxide, 9.8 lb/day hydrochloric acid, 103.9 lb/day triacetin and
7942 gal/day water. The injection concentrations of oxidant
formulation constituents are about 800 mg/L peroxyacetic acid,
<15 mg/L hydrogen peroxide, 664 mg/L glycerol, 912 mg/L sodium
acetate, 238 mg/L sodium chloride and an initial solution pH of
8.5-9.5. Additional sodium chloride can be added to match the
salinity of the soil, if necessary. Non-toxic additives including
co-solvents (e.g., triacetin, glycerol), compatible surfactants
(e.g., sodium dodecyl sulfate) and stabilizers (e.g., phytic acid)
are optionally added to enhance performance. The prepared
formulation are fed as a liquid into injection wells to infiltrate
the soil at ambient temperature. A residence time of at least six
hours is employed and provides singlet oxygen generation activity,
provides peroxyacetic acid reaction time with contaminants and also
allows Fenton-like peroxide activation processes to occur with any
reduced iron minerals present.
[0307] Recovered, spent flushing fluids have pH similar to that of
the soil body treated and contain salinity, hardness (e.g.,
calcium/magnesium carbonate), suspended solids (e.g., iron or
manganese oxides), glycerol, acetate, additives, oxidation
byproducts (e.g., nitrate, low molecular weight hydrocarbons) and
potentially non-oxidized contaminants and microbes. The spent
flushing fluids are optionally treated on site for discharge, sent
to a municipal water treatment facility, disposed of in an
injection well, or are processed for water recovery and recycle
back into the remediation process or other use.
Example 14
Superoxide Formulation for Ex-Situ Chemical Oxidation and Reduction
for Remediation
[0308] Superoxide formulations can be used for remediation and
decontamination of a body of soil, a geologic formation, an
excavated soil, or construction or demolition debris.
[0309] The following example illustrates a superoxide formulation
for ex situ chemical oxidation for remediation of soil contaminated
with 10 mg/kg non-aqueous phase liquids (NAPL) containing low
volatility halogenated materials which can include brominated flame
retardants, dioxins, and/or polychlorinated biphenyls (PCB's). The
superoxide formulation is prepared using the system of FIG. 5. The
resulting superoxide formulation is used to chemically oxidize more
than 99% of the contaminants and flush residuals out of the soil.
The soil sample of the example has a pH 7.0-7.5, average soil
density is 2.4 g/cm.sup.3, and the soil type is a sand/alluvial
mixture. The soil is excavated for treatment and then is returned
to its origin.
[0310] In the present example, treatment includes applying the
equivalent of 4 soil pore volumes (20% porosity assumed) of
superoxide formulation containing a 3:1 mass ratio of hydrogen
peroxide to contaminant to set the superoxide dose, and a treatment
rate of 32 cubic yards per day. Chemical input and output rates are
calculated based on the process described for FIGS. 7 and 11, using
an electrochemical reactor of the type in FIG. 6. Inputs into the
electrochemical generator are 834 lb/day sodium sulfate, 218
gal/day water, 5600 L/day oxygen gas at STP and approximately 1070
kWh per day to operate the system. The reactor can produce 100
lb/day hydrogen peroxide at 40% current efficiency (produced as
sodium peroxide), a maximum potential mass of 235 lb/day superoxide
at about 50% current efficiency (produced as sodium superoxide),
approximately 28 lb/day sodium hydroxide and, in a separate output
stream, 711 lb/day sodium bisulfate. Sodium bisulfate may be used
for pH adjustment of superoxide formulations and/or treated soil,
if desired. The reactor output can be diluted with 4880 gal/day
water to produce an oxidant formulation of about 90 mg/L hydrogen
peroxide, up to 212 mg/L superoxide, up to 750 mg/L sodium sulfate
and an initial solution pH of 10.5-11.5. A relatively low
concentration of oxidants is employed to avoid the quenching of
generated hydroxyl radicals, similar to an ultraviolet-hydrogen
peroxide advanced oxidation process. Other additives such as
surfactants and co-solvents are optionally used, but are
selectively used to minimize consumption of hydroxyl radicals
produced by the formulation. The prepared formulations are applied
as a liquid to the excavated soil and allowed to contact the soil
for a period of time at ambient temperature or elevated
temperature. The soil is optionally flushed in a second step with
excess co-generated acid or sodium bisulfate, to balance the pH of
the soil if becomes elevated during treatment and if desired.
[0311] Recovered, spent soil washing fluids will have a pH similar
to that of the soil and contain salinity, hardness (e.g.,
calcium/magnesium carbonate), additives and potentially oxidation
or reduction byproducts or non-oxidized or reduced contaminants and
microbes. The spent flushing fluids are optionally treated on site
for discharge, sent to a hazardous waste facility, disposed of in
an injection well, or processed for water recovery and recycle back
into the remediation process or other use.
Example 15
Clean in Place (CIP) Applications for Food, Beverage, Dairy, and
Biopharma Processing Equipment Cleaning
[0312] Clean in place (CIP) applications involve preparing
cleansers and sanitizer solutions and dispensing them into pipes,
tanks and other processing equipment that is not disassembled for
cleaning. The chemical activity of such solutions provides the
cleansing and sanitizing capabilities. CIP cleansers and sanitizers
are prepared in day tanks, often ranging in capacity from 50 to 500
gallons, and distributed to equipment when needed during cleaning
cycles. Alkaline cleansers and oxidizing alkaline cleansers are
particularly useful for removing soils and organic residues. Acids
are particularly useful for removing scaling minerals.
Antimicrobial sanitizers are particularly useful for disinfection.
The use of non-chlorine based cleansers and sanitizers is of
interest to minimize corrosion of stainless steel processing
equipment and to avoid chlorinated oxidation or disinfection
byproducts.
[0313] Acid compatible sanitizers, such as peroxyacetic acid, can
be used to reduce the number of system cleaning flushes needed
relative to chlorine and chlorine bleach based sanitizers, which
are not compatible with acid pH of less than about pH 4 due to the
release of chlorine gas Alkaline oxidizing cleansers may be more
effective at removing organic soils, proteins and fat deposits than
alkali detergents alone. See U.S. Pat. No. 7,754,064, FIGS. 13-14,
for example.
[0314] FIG. 17 shows an exemplary system and flow process for
electrochemically generating a CIP cleanser, in one embodiment. An
electrochemically generated CIP cleanser and sanitizer formulation
is used for food, beverage, dairy and biopharma processing
equipment. Alkaline oxidizing cleanser 1720 and acid sanitizer 1722
are co-generated and stored in 500 gallon day tanks 1716, 1718,
respectively until use. The alkaline oxidizing cleanser 1720 is
formulated to contain 0.01 M NaOH (pH 12.0) and 200 mg/L
peroxyacetic acid to generate singlet oxygen, by method 500. The
acid sanitizer 1722 is formulated to contain 0.02 M citric acid (pH
2.6) and 400 mg/L peroxyacetic acid, generated by, for example,
using the electrochemical reactor of FIG. 6. Surfactants and
stabilizers are optionally used in either a cleanser or sanitizer
solution, but are not required, and not shown in FIG. 17. Cleanser
solutions 1720, 1722 are heated to 55-60.degree. C. prior to
distribution as is customary for CIP processes.
[0315] The above specified formulations use two identical
electrochemical reactors, for example, the electrochemical reactor
discussed with reference to FIG. 6 above, with the exception of
their cathode surface compositions and feed rates, in parallel to
generate the required chemicals by the process outlined in FIG. 17.
Electrochemical production is designed for 500 gallons each of
alkaline and acid cleansers. Reactor inputs makeup water 1702,
brine 1704, oxygen gas 1706, and power source 1708 and outputs
1724, 1726 are listed on a 100% basis.
[0316] Electrochemical reactor 1714 contains an activated carbon
cathode surface for high efficiency hydrogen peroxide production
and produces alkaline hydrogen peroxide and citric acid
concentrates in two separate output streams. Inputs for reactor
1714 are 6.93 lb/day sodium citrate 1704, 230 L/day oxygen gas 1706
at STP, 15 gal/day water 1702(1) and approximately 9.9 kWh
electricity 1708 to operate the system. Outputs for reactor 1714
are (i) an alkaline H.sub.2O.sub.2 concentrate 1724 including 1.12
lb/day hydrogen peroxide (at 84% cathode current efficiency)
combined with 0.38 lb/day sodium hydroxide and (i) an acid
concentrate output 1726 including 4.53 lb/day citric acid in a
separate stream. The alkaline hydrogen peroxide 1724 is reacted
with 4.78 lb/day triacetin 1710 and two thirds of the resulting
peroxyacetic acid solution 1724' is fed to the alkaline cleanser
holding tank 1716 while the remainder is fed to the acid sanitizer
holding tank 1718. Less than about 15 mg/L hydrogen peroxide is
present in the peroxyacetic acid output 1724'.
[0317] Electrochemical reactor 1715 contains a nickel cathode
surface for high efficiency sodium hydroxide production and
produces alkaline hydrogen peroxide 1728 and citric acid 1730
concentrates in two separate output streams. Inputs for reactor
1715 are 17.7 lb/day sodium citrate 1705, 320 L/day oxygen gas 1707
at STP, 17 gal/day water 1702(2) and approximately 18.3 kWh
electricity 1709 to operate the system. Outputs for reactor 1715
are 1.66 lb/day sodium hydroxide 1728 (at 98% cathode current
efficiency) and 11.57 lb/day citric acid 1730 in a separate stream.
The sodium hydroxide 1728 is fed to the alkaline cleanser holding
tank 1716 while the citric acid 1730 is fed to the acid sanitizer
holding tank 1718.
[0318] The alkaline cleanser holding tank 1716 and acid sanitizer
holding tanks 1718 are filled with water 1702 during chemical
production bringing their final volumes to 500 gallons each. The
use of triacetin 1710 to generate the peroxyacetic acid 1724'
results in about 340 mg/L glycerol plus 475 mg/L sodium acetate in
the alkaline cleanser and 170 mg/L glycerol plus 235 mg/L acetic
acid in the acid sanitizer 1722.
[0319] In some exemplary CIP applications milder cleansers are
desirable. Singlet oxygen generation is not desirable when
materials to be treated (or which may come in contract with
formulation) are susceptible to degradation by singlet oxygen.
Relevant examples include desalination filter membranes and
polymers including polyamides, polysulfone, polyurethane,
polyetheylene terephthalate, epoxy resins,
polyacrylonitrile-butadiene copolymer (nitrile rubber) and natural
rubber. To quench singlet oxygen generation by the alkaline
cleanser solution described in the above CIP example a lower amount
of triacetin 1710 is used thereby leaving a hydrogen peroxide
concentration, in combination with peracid solution 1724', high
enough to quench singlet oxygen evolved by peroxyacetic acid. For
example, the triacetin input 1710 may be decreased by 67% to about
1.63 lb/day thereby increasing the hydrogen peroxide concentration
to about 100 mg/L and decreasing the peroxyacetic acid
concentration to about 200 mg/L in the alkaline cleanser solution
1720. As a result the acid sanitizing solution 1722 will contain
about 50 mg/L hydrogen peroxide and 100 mg/L peroxyacetic acid. The
alkali and acid concentrations remain virtually unchanged unless
their production by electrochemical reactor 1715 is decreased.
Example 16
Singlet Oxygen Production Using Bulk Chemicals for Oil Production
Well Flushing Applications
[0320] Well casings and pipelines are serviced to remove bacterial
growth, slime buildup, mineral scale deposits, corrosion and
contamination. These issues are common among oil and gas production
wells and pipelines, groundwater wells, raw water and wastewater
pipelines, and potable water and greywater distribution systems.
Microbial control, removal of slime (the decaying remains of dead
bacteria and other organic materials), microbial corrosion control
and scale removal are significant maintenance issues for prolonging
the production capacity and lifetime of a well. Pipelines carrying
raw water, wastewater, produced water, greywater and other
untreated water will encounter microbial growth and slime formation
and will require cleaning. Methods for cleaning well bore casings
and pipelines include chemical flushing with oxidizers and acids
and mechanical cleaning such as brushing and scraping.
[0321] Compatibility of oxidants with seawater and brackish water
is desirable in locations where there are no natural freshwater
resources available. Flushing solution activity should persist for
at least 5 hours and be effective in the range of pH 8-9. Ideally
flushing solutions should be pH balanced and be safe for municipal
disposal or discharge.
[0322] The following example presents an application of chemical
flushing of an oil production well with a singlet oxygen
formulation made from bulk chemicals. The singlet oxygen
formulation is created using method 400 and system 300 discussed
above. In this example, the production well is located in a coastal
region where seawater is used as floodwater for enhanced oil
recovery. The well depth is about 12,000 feet below surface and has
an average casing diameter of 6 inches and volume of about 4,630
gallons.
[0323] Chemical inputs and outputs are stated as quantities per
well volume. Chemical inputs on a 100% basis are 5.4 lb hydrogen
peroxide, 8.9 lb sodium hydroxide, 2.2 lb hydrochloric acid, 22.8
lb triacetin, 9.6 lb nonionic polyether alcohol surfactant/wetting
agent and 4630 gal water of which the majority (e.g., >90%) can
be seawater filtered through a 1 micron rated filter. The prepared
injection concentrations of oxidant formulation constituents are
about 300 mg/L peroxyacetic acid, <10 mg/L hydrogen peroxide,
250 mg/L glycerol, 340 mg/L sodium acetate, 250 mg/L
surfactant/wetting agent, 90 mg/L sodium chloride (not including
the salt added by seawater) and an initial pH of 8.5-9.5. An
oxidant-compatible corrosion inhibitor such as tetrasodium
pyrophosphate is optionally added to enhance performance.
[0324] The above prepared formulation is fed as a liquid into a
well bore (or pipeline) at ambient temperature. A residence time of
at least four to six hours is employed to provide singlet oxygen
generation activity and oxidative breakdown of organic materials;
to provide peroxyacetic acid contact time with microbes; and to
allow Fenton-like peroxide activation processes to occur with
catalytically active reduced iron surfaces or other metal surfaces
present.
[0325] The use of seawater, with a natural bromide content of about
65 mg/L, as the primary water source for the flushing solution
provides some hypobromous acid or hypobromite ion by oxidation of
bromide by peroxyacetic acid. Hypobromous acid may function as an
additional oxidant that can participate in the performance of the
singlet oxygen flushing solution and has significant oxidation and
antimicrobial activity up to about pH 8.5.
[0326] Recovered, spent flushing fluids will have a pH similar to
that of seawater or groundwater and contain salinity, hardness
(e.g., calcium/magnesium carbonate), suspended solids (e.g., iron
or manganese oxides), suspended organic materials such as slime
deposits, glycerol, acetate, surfactant and corrosion inhibitor
additives, oxidation byproducts (e.g., nitrate, low molecular
weight hydrocarbons) and potentially non-oxidized contaminants and
microbes. The spent flushing fluids are optionally treated on site
for discharge, sent to a municipal water treatment facility,
disposed of in an injection well, or processed for water recovery
and recycle back into well operations.
Example 17
Superoxide Formulation for Oil Sand Tailing Pond Water
Treatment
[0327] Oil Sand Tailing Ponds in northern Alberta, Canada represent
a very large impoundment of contaminated and toxic water created by
bitumen extraction and processing. Water quality has been degraded
through multiple reuse cycles to the point that it is no longer
suitable for reuse. Natural biodegradation and attenuation of
contaminants can be extremely slow or ineffective for remediating
these waters due to the presence of recalcitrant organic
contaminants such as naphthenic acids, phenols and polycyclic
aromatic hydrocarbons and cold temperatures. A representative
composition of tailing pond water for application of treatment
includes 2000 mg/L inorganic TDS, pH 8.3, 0.025 mg/L cyanide, 50
mg/L naphthenic acids, 10 mg/L oil and grease, 0.5 mg/L phenols,
0.01 mg/L polycyclic aromatic hydrocarbons, and several trace
metals such as iron (2 mg/L), copper (0.05 mg/L), chromium (0.01
mg/L), and lead (0.1 mg/L) among others.
[0328] The general treatment strategy is to oxidize recalcitrant
organic contaminants with a superoxide and hydrogen peroxide
formulation to allow for more rapid treatment of smaller organic
fragments downstream in a biological treatment process. Oxidation
may be provided by hydroxyl radicals formed directly by superoxide
and hydrogen peroxide by the reactions in Equations [4] and [6].
Hydroxyl radicals are expected to be formed during treatment by
Fenton chemistry with catalytically active metals surfaces present
in the tailing pond water, including iron and copper. Waste heat
from equipment and bitumen processing can provide heat to support
treatment operations.
[0329] A generation system from FIG. 18 is used in the present
example to produce a superoxide precursor formulation by
electrochemical generator, in one embodiment. Superoxide
concentrate 1124 and, optionally, acid concentrate 1126 are
electrochemically generated using an electrochemical reactor 1114.
Electrochemical reduction of oxygen is conducted at a suitable
cathode and water is oxidized at a suitable anode in an
electrochemical reactor 1114 in which the anode and cathode
chambers are separated by a membrane. Oxygen gas 1106 and a 2 g/L
aqueous sodium sulfate solution 1104 are supplied to the cathode
while a 47.5 g/L aqueous sodium sulfate solution 1104 is supplied
to the anode. A direct current 1108 is applied to the electrodes
thereby driving the reduction of oxygen at the cathode to produce
superoxide, hydrogen peroxide and sodium hydroxide as the majority
products 1124 of the cathode, while water is oxidized at the anode
to produce sodium bisulfate acid and oxygen gas as the majority
products 1126 of the anode.
[0330] In this example the cathode product solution 1810 has a
composition of approximately 8.2 g/L superoxide (as
O.sub.2..sup.-), 5.0 g/L hydrogen peroxide (as H.sub.2O.sub.2), 1.3
g/L sodium hydroxide and a pH of about 12.6 (as NaOH), assuming a
40% current efficiency for oxygen reduction to superoxide and 50%
current efficiency for oxygen reduction to hydrogen peroxide. The
anode product solution 1812 has a composition of approximately 30
g/L sodium bisulfate and 13 g/L sodium sulfate assuming about 90%
sodium sulfate to sodium bisulfate acid conversion. The anode to
cathode product solution volume ratio is about 1.73.
[0331] The superoxide-containing cathode product solution 1810 is
then diluted to its point of use concentration (i.e., 75 mg/L
hydrogen peroxide, 124 mg/L superoxide, 20 mg/L NaOH) by mixing
directly with raw tailing pond water 1820 in a 1:65.7 volume ratio.
This mixture is held in an oxidation tank 1124 with a residence
time of 6 to 24 hours after which the oxidized water is pH adjusted
with the anode product solution 1126 in a 38.5:1 volume ratio. The
pH-adjusted oxidized tailing pond water 1822 is then sent to a
secondary treatment process. An example of a secondary treatment
process is an aerobic bioreactor stage, to remove organic residuals
and nitrification, followed by an anaerobic bioreactor stage, for
sulfate reduction, removal of metal as sulfides and
denitrification.
Example 18
Oxidative Reductive Potentials of ROS Solutions
[0332] Formulations of reactive oxygen species were produced to
determine their resulting ORP readings at various pH's and
concentrations. Formulations included (1) hydrogen peroxide with
superoxide produced by electrochemical generation; (2) singlet
oxygen-generating peroxyacetic acid produced by bulk chemical
mixing (PM formulations); and (3) singlet oxygen-generating
peroxyacetic acid with superoxide produced by electrochemical
generation and bulk chemical mixing. A formulation containing
approximately equi-molar concentrations of peroxyacetic acid and
hydrogen peroxide (control A) was also made by bulk chemical mixing
to determine the effect of hydrogen peroxide, which is present in
"merchant" equilibrium peroxyacetic acid solutions, on the ORP of
peroxyacetic acid.
[0333] Solution pH was measured using a high sodium pH electrode,
Oakton model 35805-05, with Oakton pH 11 series meter and auto
temperature compensation probe. The pH electrode and meter were
calibrated with a standard three point calibration. ORP
measurements were made using an Oakton model 35805-15 ORP electrode
with Oakton pH 11 series meter and auto temperature compensation
probe. Raw ORP readings were corrected to the standard hydrogen
electrode (SHE) using the Theremo/Orion ORP standard 967901
(420.+-.3 mV vs SHE at 25.degree. C.). ORP measurements were made
while stiffing the solution until a stable reading was obtained and
repeated up to four times on the same sample. Samples were kept at
25.+-.3.degree. C. using a temperature regulated water bath.
Hydrogen peroxide concentration was analyzed by colorometric
titration using the Hach Inc. HYP-1 Hydrogen Peroxide Test.
[0334] ORP vs pH measurements were made on formulations normalized
to 1000 mg/L (29.4 mM) hydrogen peroxide concentration.
Peroxyacetic acid concentration of 2170 mg/L (28.5 mM) was made to
be approximately equi-molar to 1000 mg/L hydrogen peroxide assuming
97% conversion of hydrogen peroxide to peroxyacetic acid. Sample pH
was adjusted to between pH 3 and 13 using concentrated sodium
bisulfate and sodium hydroxide solutions and sample dilutions were
made using distilled water. Sample pH was adjusted as needed during
the measurement period to maintain a constant pH and was plus or
minus 0.03 pH units of the set point during ORP measurements.
[0335] ORP vs concentration measurements were made on formulations
normalized to 1000 mg/L (29.4 mg/L) hydrogen peroxide or 2170 mg/L
(28.5 mM) peroxyacetic acid then diluted by a factor of 10, 50 and
100 times with distilled water and the pH adjusted to between pH 3
and 13 with sodium bisulfate and sodium hydroxide solutions. Sample
pH was adjusted as needed during the measurement period to maintain
a constant pH and was plus or minus 0.03 pH units of the set point
during ORP measurements.
[0336] Solution 1: A formulation containing hydrogen peroxide and
superoxide was produced by the method described in Example 11 at a
reactor current of 8.0 amps. The reactor was operated for 1.75
hours to reach a steady-state cathode output containing 2500 mg/L
hydrogen peroxide, a calculated maximum of about 14,000 mg/L
superoxide anion, 7100 mg/L sodium sulfate, a pH of 13.3 and an ORP
of 88 mV (SHE). Samples for ORP measurements were prepared by
adjusting the pH of 8.0 mL of fresh cathode output with
concentrated sodium bisulfate while diluting it to 20.0 mL with
distilled water to make 1000 mg/L (29.4 mM) hydrogen peroxide
concentration.
[0337] Solution 2: The cathode output generated as noted above was
also used to produce peroxyacetic acid solutions containing
superoxide and capable of producing singlet oxygen by mixing 8.0 mL
of fresh cathode output with 0.10 g of triacetin (99%, Acros
Organics) for approximately 3 to 4 minutes. This concentrate was
diluted to 20.0 mL with distilled water, while adjusting the pH to
make 2170 mg/L (28.5 mM) peroxyacetic acid concentration.
[0338] Solution 3: Peroxyacetic acid solutions capable of producing
singlet oxygen were produced by mixing 2.0 mL of a 10.0 g/L
hydrogen peroxide stock solution (made from 3 wt % topical solution
and adjusted to pH 12.5 with sodium hydroxide) with 0.09 g
triacetin for 3 to 4 minutes. The resulting concentrate was diluted
to 20.0 mL with distilled water while adjusting the pH to make 2170
mg/L (28.5 mM) peroxyacetic acid concentration.
[0339] Control solution A: To the peroxyacetic acid solution
concentrate (CPA, at pH 12.5) was added 2.0 mL of 10.0 g/L hydrogen
peroxide solution. The resulting concentrate was diluted to 20.0 mL
with distilled water while adjusting the pH to make 2170 mg/L (28.5
mM) peroxyacetic acid and 1000 mg/L (29.4 mg/L) hydrogen peroxide
concentration.
[0340] FIG. 19 shows the ORP values of Solutions 1 through 3 and
control A in the range of pH 3 to 13 varied by increments of one pH
unit. Solution 1 (open diamonds) containing hydrogen peroxide and
superoxide had the lowest ORP values overall in qualitative
agreement with the presence of superoxide which has a standard
potential of -0.33 V (SHE). The ORP of 1000 mg/L hydrogen peroxide
alone at the same pH values (data not shown) was about midway
between that of Solution 1 and Control solution (solid
circles).
[0341] Solution 2 (opens squares) containing peroxyacetic acid with
superoxide had a greater ORP than Control solution A, at a pH of
less than 11, demonstrating that the presence of hydrogen peroxide
in peroxyacetic acid lowers the observed ORP. The ORP of Solution 2
exceeded 650 mV (SHE) as the pH decreased to about pH 6 and lower.
The ORP of Control solution A did not exceed 650 mV (SHE), until
the pH was decreased to about pH 4 and lower.
[0342] According to the methylene blue dye oxidation activity
described in Example 9 the generation of singlet oxygen by the
Solution 2 formulation is necessary to provide the oxidative power
to decolorize methylene blue. The pH range in which methylene blue
oxidation occurs best is between pH 6 and 11.5. Outside of this pH
range methylene blue is not significantly oxidized or oxidized at
significantly slower rates. The presence of hydrogen peroxide in
significant concentrations, as in Control Solution A, inhibits
methylene blue oxidation throughout this pH range. Hydrogen
peroxide alone at comparable concentrations has no visible effect
on methylene blue.
[0343] Solution 2 has significantly stronger oxidative activity as
shown by oxidation of MB than other hydrogen peroxide containing
solutions in the range of about pH 6 to 11.5. However, there is no
distinctive signature in the ORP of this enhanced activity as
presented in FIG. 19. Singlet oxygen has a relatively low standard
potential of 0.65 V (SHE) compared to that of peroxyacetic acid,
1.81 V (SHE), and has a very short half life in water on the order
of microseconds. For these reasons it is thought that singlet
oxygen does not affect the ORP even though its chemical reactivity
is significantly greater towards certain materials than
peroxyacetic acid and hydrogen peroxide.
[0344] The ORP of Solution 2 increased slightly over the first 10
to 20 minutes after the initial preparation. The magnitude of
increased ORP showed some pH dependence and one set of analyses
showed increases of 17% at pH 9.0, 3% at pH 7.0, 1% at pH 6.0 and
0% at pH 5.0. The slightly elevated ORP was persistent for at least
4 hours at 25.degree. C. It is also observed in methylene blue dye
oxidation experiments that enhanced oxidative activity of the
Solution 2 formulation can persist for 6-8 hours or more. This
behavior indicates that there is a dynamic chemical process
occurring in these solutions above pH 5 which involves peroxyacetic
acid and singlet oxygen evolution.
[0345] The effect of diluting Solution 2 with distilled water on
ORP was negligible in the range of 2170 to 22 mg/L peroxyacetic
acid at pH 7.0, 6.0 and 5.0. The ORP of Solution 2 decreased by
about 10% at pH 9.0 after diluting from 2170 mg/L to 22 mg/L
peroxyacetic acid.
[0346] The production of other reactive oxygen species also
contributes to the ORP in Solution 2. The presence of other ions,
salt and catalytic impurities, such as iron, can affect the ORP
value of freshly made solutions and an increase in ORP over time.
The interaction of singlet oxygen and certain other ROS, such as
superoxide discussed below, can produce solutions with
significantly higher ORP. These ORP effects are most pronounced at
alkaline pH indicating that an additional ROS that is more active
or stabilized at alkaline pH is present.
[0347] The catalytic decomposition of hydroperoxides, such as
hydrogen peroxide and peracetic acid, can produce other ROS such as
superoxide radical, hydroxyl radical, hydroperoxyl radical and
peracetyl radical. For example, at pH 9.0 the ORP of Solution 2
will increase over a period of several hours when diluted with
unfiltered tap water from a groundwater source containing 16-18
grains hardness as shown in FIG. 20. In this figure, the relative
effects of use of distilled water (solid squares) and tap water
(solid diamonds) to dilute solution 2 is illustrates. PAA
concentration in these solutions was 28.5 mM.
[0348] Solution 3 containing peroxyacetic acid and superoxide
exhibited a significantly higher ORP of 825 mV to 1065 mV (SHE) in
the range of about pH 6 to 11, which corresponds with the active pH
range for superoxide production. The combination of superoxide with
singlet oxygen in this formulation produces one or more reactive
oxygen species which significantly impact the measured ORP.
According to the methylene blue dye oxidation activity described in
Example 9, the rate of oxidation is enhanced by the Solution 3
formulation over that of the Solution 2 formulation, in agreement
with the presence of additional reactive oxygen species with higher
oxidation potential reflected in the higher ORP observed.
[0349] Additional evidence for the production of one or more
reactive oxygen species in the Solution 3 formulation was observed
by monitoring ORP over time at pH 7 (solid triangles) or 9 (open
circles), as shown in FIG. 21. When Solution 3 was initially
prepared the ORP values were greater than that of Solution 2, but
steadily increased over the first 20 minutes (at both pH's). This
behavior shows the buildup of at least one additional oxidizing
species with a modest half life (e.g., minutes) depending on the
rate of formation relative to decomposition. A maximum ORP is
reached after the first 20 minutes and begins to decline after
about 1 hour. The rate of ORP decline is accelerated at higher
pH.
[0350] The effect of diluting Solution 3 on ORP was measured in the
range of 2170 to 22 mg/L peroxyacetic acid at pH 9.0 (open circles)
and 7.0 (solid triangles) with data shown in FIG. 22. Solution
concentrates were prepared as described earlier containing 2170
mg/L peroxyacetic acid and allowed to equilibrate at 25.degree. C.
for 30 minutes prior to diluting by 10, 50 and 100 times with
distilled water and pH adjustment. The ORP of Solution 3 decreased
with decreasing peroxyacetic acid and superoxide concentrations.
Logarithmic curve fits are included in FIG. 22. The range of ORP
over this wide range of concentration does not follow the expected
behavior exhibited by Solution 2. The observed behavior indicates a
dynamic chemical process is active involving a chemical reaction or
re-speciation between multiple chemical species. For example, as
the Solution 3 concentration is decreased the rate of reaction
between multiple reactants to produce the transient reactive oxygen
species responsible for the elevated ORP also decreases relative to
the half life of the transient species. A lower Solution 3
concentration effectively results in reducing the equilibrium
concentration of the transient reactive oxygen species responsible
for the elevated ORP.
Example 19
Exemplary Methods for Generating Formulations
A. Exemplary Method for Making Peroxyacetic Acid Formulation to
Evolve Single Oxygen.
[0351] PM formulation prepared from 3% wt/wt or wt/vol
H.sub.2O.sub.2) which produces 60.4 g/L PAA (assuming 98% HP
conversion to PAA and no dilution by acid pH adjustment or other
processes). Starting with 10 mL of 30 g/L (3%) H.sub.2O.sub.2;
0.353 g NaOH [1:1 molar ratio HP:NaOH]; 1.283 g (1.11 mL) triacetin
(acetyl donor) [1:0.667 molar ratio HP:triacetin, which is the 1:2
molar ratio of HP to acetyl donor because triacetin provides three
acetyl groups. Optional pH adjustment with H.sub.2SO.sub.4
(alternate acids that can be used include HCl, acetic acid, citric
acid, phosphoric acid, bisulfate [NaHSO.sub.4], or lactic
acid).
[0352] Procedure conducted at room temperature, 15-25.degree. C. is
the typical range. Dissolve 0.353 g NaOH in 10.0 mL of 30.0 g/L
H.sub.2O.sub.2, about 1 min mixing time. The pH will be about
12.7-12.8 as H.sub.2O.sub.2 is converted substantially to NaOOH in
this step. Preferably move to this step as quickly as possible,
i.e. within 1 minute after dissolving NaOH as H.sub.2O.sub.2 will
begin to degrade at room temperature forming oxygen gas and NaOH.
Add the alkaline hydrogen peroxide to 1.283 g triacetin and mix
rapidly until there are no oil droplets remaining, approx 1-3 min
mixing time. The pH of the resulting mixture will be about
10.1-10.7. If necessary, add 0.1 M acid or NaOH to adjust the pH to
the desired initial pH (pH 8-10 is a typical range for several
applications). The volume of acid added will dilute initial
prepared PAA concentration. Allow the mixture to "activate"
naturally by inherent reactions by allowing concentrate to sit for
up to 5 minutes. Singlet oxygen will begin to evolve. Side
reactions not evolving singlet oxygen can evolve other transient
reactive oxygen species and organic radicals which provide
synergisms to enhance oxidative activity, antimicrobial activity
and increase the ORP of the oxidant solution. Using a pH of 7 or
greater allows for a more significant increase in ORP to occur over
time, presumably due to a stabilization of certain reactive oxygen
species as the pH increases. In an embodiment, begin use of the
prepared formulation 2-5 minutes after preparation to minimize loss
of initial PAA concentration. Durning use PAA continues to react
forming singlet oxygen, molecular oxygen, (probably carbon
dioxide), acetic acid and sodium acetate and the pH decreases as
reaction proceeds. A desired amount of the concentrated formulation
can be introduced into a target liquid stream; or applied to a
surface, vessel or pipe (more generally any substrate).
Alternatively, the concentrated formulation can be diluted to a
lower use concentration. Dilution of the concentrate (e.g., with
water 10.times. or more) will extend working time in a day tank or
buffer tank without significant loss of activity.
B. Exemplary Method for Making Peroxyacetic Acid Formulation to
Evolve Single Oxygen.
[0353] PM formulation prepared from 1% wt/wt or wt/vol H2O2 which
produces 21.1 g/L PAA (assuming 98% HP conversion to PAA and no
dilution by acid pH adjustment or other processes) starting with 30
mL of 10 g/L (1%) H.sub.2O.sub.2 [use three times the volume as in
A]; 0.353 g NaOH [1:1 molar ratio HP:NaOH]; and 1.283 g (1.11 mL)
triacetin [1:0.667 molar ratio HP:triacetin]. The pH is optionally
adjusted with H.sub.2SO.sub.4 (alternate acids include HCl, acetic
acid, citric acid, phosphoric acid, bisulfate [NaHSO4], or lactic
acid).
[0354] Procedure is conducted at room temperature, 15-25.degree. C.
is a typical range. Dissolve 0.353 g NaOH in 30.0 mL of 10.0 g/L
H2O2, about 1 min mixing time. pH will be about 12.5-12.6.
H.sub.2O.sub.2 is converted substantially to NaOOH in this step.
Move this step within about 4 hours, because the hydrogen peroxide
will begin to degrade at room temperature. Add the alkaline
hydrogen peroxide to 1.283 g triacetin and mix rapidly until there
are no oil droplets remaining, approx 1-3 min mixing time. The pH
will be about 9.8-10.6. If necessary, add 0.1 M acid or NaOH to
adjust pH to desired initial pH (pH 8-10 is a typical range for
several applications). The volume of acid added will dilute initial
prepared PAA concentration. Allow the formulation to "activate"
naturally by inherent reactions by allowing concentrate to sit for
up to 10 minutes. Singlet oxygen will begin to evolve. Side
reactions not evolving singlet oxygen can evolve other transient
reactive oxygen species and organic radicals which provide
synergisms to enhance oxidative activity, antimicrobial activity
and increase the ORP of the oxidant solution. Again use of pH of 7
or greater allows for a more significant increase in ORP to occur
over time, presumably due to a stabilization of certain reactive
oxygen species as pH increases. Preferably begin use of the
prepared concentrate formulation within 2-10 minutes after
preparing to minimize loss of initial PAA concentration. PAA
continues to react forming singlet oxygen, molecular oxygen, acetic
acid and sodium acetate as the pH decreases as reaction proceeds.
Dose desired amount of the concentrate into target liquid stream;
or apply to a surface, vessel or pipe; or dilute to a lower use
concentration. Diluting the concentrate (e.g., with water 10.times.
or more) to extend working time in a day tank or buffer tank
without significant loss of activity.
C. Third Exemplary Method for Preparation of a Peroxyacetic Acid
Formulation for Evolution of Singlet Oxygen. Continuous Dose
Preparation (Dosing Skid).
[0355] Any appropriate device configuration for automated
preparation including mixing apparatus, means for delivery of
solutions, holding tanks and means for dispensing product can be
employed. The method produces a 5% PAA (50 g/L concentration using
3% hydrogen peroxide feedstock (assuming 97% HP conversion) at a
rate of 224 kg/day PAA (100% pure PAA basis). Starting with 2.34
L/min of 30 g/L (3.0%) H.sub.2O.sub.2; 111 mL/min 50% wt/wt NaOH
[1:1 molar ratio HP:NaOH]; 262 mL/min triacetin [1:0.667 molar
ratio ITP:triacetin]; 27.3 mL/min of 98% H.sub.2SO.sub.4 (example
rate for pH adjustment).
[0356] Process is conducted at ambient temperature, 10-30.degree.
C. Feed the 50% NaOH into the 3% H.sub.2O.sub.2 stream and pass
through a static mixer. The pH will be about 12.7. It may be useful
to dissipate heat released on addition. Feed triacetin into the
alkaline peroxide stream and pass through a static mixer with an
appropriate residence time (e.g., 1-3 min). The pH of the mixture
will be around 10.1-10.7. Feed the up to 16% H.sub.2SO.sub.4 into
the alkaline PAA stream and pass through a static mixer to adjust
pH to desired initial pH (pH 8-10 is a typical range for several
applications). Collect prepared oxidant solution concentrate in a
buffer tank or holding tank for up to 5 minutes to allow the
solution to "activate" naturally by inherent reactions. Singlet
oxygen will begin to evolve. Side reactions not evolving singlet
oxygen can evolve other transient reactive oxygen species and
organic radicals which provide synergisms to enhance oxidative
activity, antimicrobial activity and increase the ORP of the
oxidant solution. Begin use of the prepared formulation concentrate
2-5 minutes after preparing to minimize loss of initial PAA
concentration. PAA continues to react forming singlet oxygen,
molecular oxygen, (probably carbon dioxide), acetic acid and sodium
acetate and pH decreases as reaction proceeds. Dispense desired
rate of above concentrate stream into target liquid stream; or
apply to a surface, vessel or pipe; or dilute to a lower use
concentration. Dilute concentrate (e.g., with water 10.times. or
more) to extend working time in a day tank or buffer tank without
significant loss of activity.
D. Exemplary Method for Preparing Peroxyacetic Acid Formulation to
Evolve Singlet Oxygen in the Presence of Superoxide
[0357] Prepare parent oxidant solution concentrate as described in
Example 18 (solution 3). Adjust the solution pH to between 5 and 12
and allow the solution to equilibrate to produce an elevated ORP
solution. The solution is then used as-is or by dilution in an
application such as, for example, hard surface cleaning, clean in
place sanitizing, sterilizing medical instruments, decontamination,
filter cleaning, water and wastewater treatment, produce washing
flumes and hydrocoolers, meat processing lines and chiller tanks,
pulp and textile bleaching, cooling tower water treatment.
E. Exemplary Method for Preparation of Peroxyacetic Acid/Superoxide
Formulation to Evolve Singlet Oxygen.
[0358] The method is a continuous dose preparation method (dosing
skid). Any appropriate device configuration for automated
preparation including mixing apparatus, means for delivery of
solutions, holding tanks and means for dispensing product can be
employed. The method produces 7.0 g/L PAA+10.5 g/L Superoxide as
O.sub.2.sup.- (assuming 98% HP conversion) at a solution volume
rate of 60 mL/min=86.4 L/day and at a chemical mass rate of 0.60 kg
PAA+0.91 kg superoxide per day on a 100% chemical basis at 1:3.6
molar ratio of PAA: superoxide.
[0359] Starting with 60 mL/min of reactor cathode output,
containing 5.8 g/L NaOOH, 15.8 g/L NaOH and 19.8 g/L NaO.sub.2 in
the presence of 2.8 g/L Na2SO4 electrolyte[the HP:NaOH:NaO.sub.2
molar ratio is about 1:3.8:3.5]; 1.16 mL/min (1.35 g/min) triacetin
[1:1 molar ratio HP:triacetin, which is a 1:3 molar ratio of HP to
acetyl donor; with pH adjustment with 4.3 mL/min of 4.0 mol/L
NaHSO.sub.4 solution. (alternate acids include H.sub.2SO.sub.4,
HCl, acetic acid, citric acid, phosphoric acid, or lactic
acid).
[0360] The process is conducted at ambient temperature,
10-30.degree. C. Feed the 1.16 mL/min triacetin into the 60 mL/min
reactor cathode output stream. Mix these two streams with a
suitable device such as a plug-flow static mixer and a reaction
time of 1-2 minutes. Feed 4.3 mL/min of 4.0 mol/L NaHSO.sub.4
solution into the above stream and mix by with a suitable device
such as a plate type static mixer.
[0361] Use Case 1a: Convey the prepared oxidant concentrate
directly to its point of use to minimize loss of PAA and superoxide
concentrations and to utilize the synergistic enhancement of
oxidative power or reactivity towards organic materials over the
formulations of PAA without superoxide.
[0362] Use Case 2a: Collect prepared oxidant solution concentrate
in a buffer tank or holding tank for up to 30 minutes to allow a
chemical transformation to occur involving superoxide and singlet
oxygen in the presence of PAA. The resulting oxidant formulation
will develop a significantly higher ORP (from about pH 6 to pH 11)
and exhibit less reactivity with organic materials. An elevated ORP
will remain for a period of time with its maximum ORP and rate of
decline dependent on the PAA:superoxide ratio, pH and
concentration.
Example 20
Exemplary Embodiments of Reactive Oxygen Species Formulations
[0363] The following provides exemplary reactive oxygen species
formulations in liquid form which are useful in various oxidation
applications as described herein. Each formulation is particularly
useful as an oxidizing biocide, a sanitizer and/or as a selective
oxidant for inorganic and organic material oxidation, breakdown of
polysaccharides, odor control and enhanced coagulation and
microflocculation. Each exemplary formulation has a different
activity and reactivity profile.
1. PAA (Peroxyacetic Acid)+Singlet Oxygen Formulation (Designated
PM)
[0364] PM formulations contains a peroxyacetic acid composition
that produces singlet oxygen at high efficiency as the primary
reactive oxygen species. Its biocidal activity is generally more
rapid than oxidation of materials providing selectivity for
microbial control over material oxidation at low use
concentrations. PM formulations can also form other reactive oxygen
species and other reactive species in addition to singlet oxygen,
which provide synergistic performance enhancements. This
formulation contains peroxyacetic acid prepared employing an acetyl
donor (e.g., triacetin). Formulations having similar properties
(designated PM*) can be prepared which contain peroxyacids other
than peroxyacetic acid (or mixtures of peroxyacids). It will also
be appreciated that alternate cation components of the formulation,
exemplified by sodium ion, can be employed without significant
detriment, as long as solubility of components is maintained.
Formulation Compositions and Production Methods
[0365] PM is efficiently made by mixing bulk chemicals to produce a
concentrate composition containing peroxyacetic acid as the parent
oxidant. In a preferred embodiment a 1:1 molar ratio of hydrogen
peroxide, 3 wt % solution, and sodium hydroxide, 50 wt % solution,
are combined at room temperature and subsequently reacted with an
acetyl donor, such as triacetin, pure liquid, in a 1:2 molar ratio
of hydrogen peroxide to acetyl donor reactive groups. The resulting
oxidant formulation, or concentrate, contains 5.7-5.8 wt %
peroxyacetic acid, 0-0.05 wt % hydrogen peroxide, 4.6-4.7 wt %
glycerol, 4.6-4.7 wt % acetic acid, 1.7-1.8 wt % sodium ion, a pH
of 10.1-10.7 and has a measured ORP of 425-455 mV vs SHE. The
concentrate's pH is within the activated singlet oxygen forming
range of pH 6-12 and is evolving singlet oxygen at the expense of
the peroxyacetic acid being consumed over time and a concomitant
decrease in pH. The concentrate's pH can optionally be lowered to a
pH within the activated singlet oxygen forming range by adding an
acid.
[0366] PM formulations can also be made by producing an alkaline
hydrogen peroxide solution with an electrochemical reactor to which
the acetyl donor is added to produce a concentrate composition
containing peroxyacetic acid as the parent oxidant. PM formed using
electrochemical reactor output is designated PME. Again alternative
formulations designated PME* can be formed using acyl donors other
than acetyl donors. An exemplary reactor output stream contains
0.82 wt % sodium peroxide, 2.4 wt % sodium hydroxide and 0.28 wt %
sodium sulfate. This reactor output stream is reacted with an
acetyl donor, such as triacetin, pure liquid, in a 1:3 molar ratio
of hydrogen peroxide to acyl donor reactive groups. The resulting
oxidant formulation (PME), or concentrate, contains 1.06-1.08 wt %
peroxyacetic acid, 0-0.01 wt % hydrogen peroxide, 1.30-1.31 wt %
glycerol, 1.70-1.72 wt % acetic acid, about 0.18 wt % sulfate ion,
1.30-1.31 wt % sodium ion and a pH of 12.5-13. The pH of the
concentrate as initially formed is greater than the desired
activated singlet oxygen forming range of pH 6-12, and is can
optionally be lowered to a pH within the activated singlet oxygen
forming range by adding additional acid. The concentrated high pH
precursor formulation (PME precursor) can optionally be stored
before its activation by lowering the pH. Specifically, the pH of
the precursor formulation (as formed or after a desired period of
storage) can be adjusted to pH 10-11 to activate the formation of
singlet oxygen by adding, for example, sulfuric acid, 98 wt %, in
about a 0.36:1 molar ratio relative to the initial molar
concentration of sodium hydroxide in the electrochemical reactor
output. The ORP range and peroxyacetic acid consumption rates of
this PME formulation are similar to those of the PM formulation
formed by bulk chemical mixing. As an alternative, for PME where
the pH of the reactor output is higher than about 12, acid, such as
sulfuric acid, can be added to the reactor output prior to addition
of acetyl donor to bring the reactor output into the pH 6-12 range
and in this case a 1:2 molar ratio of hydrogen peroxide:acetyl
donor groups can be used to generate PME, thereby increasing
production efficiency relative to acetyl donor consumption.
Triacetin is the preferred acetyl donor for PM, and PME
formulations.
PM Formulation Stability
[0367] The initial 5.7-5.8 wt % peroxyacetic acid concentration in
the exemplary PM formulation above decreases by about 2% in about 2
minutes. The peroxyacetic acid consumption rate and singlet oxygen
evolution rate can be decreased improving stability by diluting the
PM formulation. For example, a diluted PM having peroxyacetic acid
concentration of 0.5 wt % with pH 9.5 to 10.5 will exhibit a slower
rate of decrease of peroxyacetic acid concentration of about 2% in
about 10 minutes (an about 5-fold enhancement in stability). The
peroxyacetic acid consumption rate and singlet oxygen evolution
rate of PM formulation can also be decreased by lowering the pH of
the PM formulation to within the range pH to 5-6.5.
[0368] The thermal stability of peracids is known to be enhanced by
increasing the number of carbons in the peracid molecule, thereby
increasing their size and molecular weight. Stabilizers, as are
known in the art, are often added to prevent impurities from
catalyzing decomposition reactions of peracids. The rate of
bi-molecular peracid reaction(s) leading to the formation of
singlet oxygen and other reactive species can be decreased by
increasing the size of the peracid molecule(s) and increasing the
viscosity of the carrier medium thereby effectively reducing the
diffusion rates of peracids. Increasing steric bulk of the peracids
can also be used to hinder the bi-molecular peracid reaction rate.
Peracids that are larger and more stable than peroxyacetic acid
include peroxylactic acid, peroxypropionic acid, peroxybutyric
acid, and long-chain aliphatic peroxy acids (C6 and greater) can be
employed to enhance stability and slow the rate of single oxygen
generation in formulations in PM* and PME* formulations. The
peracid of the formulation is determined by the acyl donor or
mixture of donors employed in preparation of the formulation.
2) HPS--Hydrogen Peroxide+Superoxide Formulation
[0369] The formulations designated HPS contain hydrogen peroxide
and superoxide. Superoxide in these formulations can be transformed
at least in part to hydroperoxyl radical by pH adjustment. [see:
Equation 7] HPS formulations are mild oxidants that can participate
in both oxidative and reductive reaction mechanisms, have biocidal
activity and serve as a precursor for more active oxidant
formulations discussed below.
General Composition
[0370] HPS formulations of this invention are produced using an
electrochemical reactor that reduces molecular oxygen in an aqueous
stream at the cathode to simultaneously produce hydrogen peroxide
anion, superoxide anion and hydroxide anions. It has been found
that the superoxide component in such electrochemically-formed
mixtures is stabilized and decomposes at a slower rate than similar
mixtures prepared by simple mixture of bulk chemicals. In a
preferred embodiment molecular oxygen reduction is conducted in the
presence of water containing 0.2-0.8 wt % sodium sulfate
electrolyte at an activated carbon cathode. In a preferred
embodiment the HPS formulations comprise 0.39-0.41 wt % sodium
peroxide, 1.3-1.8 wt % sodium superoxide 1.2-1.6 wt % sodium
hydroxide, 0.2-0.8 wt % sodium sulfate, pH 13.0-13.5 and ORP of
70-90 mV vs SHE. The concentrate's pH can optionally be lowered to
a pH that transforms sodium peroxide to hydrogen peroxide (pKa
11.6) and further transforms sodium superoxide to hydroperoxyl
radical (pKa 4.9). It will be appreciated that alternate cation
components of the formulation, exemplified by sodium ion, can be
employed without significant detriment, as long as solubility of
components is maintained.
Stability
[0371] The controlled, efficient production of stabilized
superoxide in aqueous solution is an advantage of the HPS
formulations. Superoxide is known to be stabilized and its lifetime
extended in aqueous media by the presence of high salinity,
alkaline pH, alkaline hydrogen peroxide and other agents that can
form stable complexes with superoxide such as cryptands and
titanium complexes. Superoxide is also known to be stable for
extended periods of time in non-aqueous phases such as ionic
liquids and organic solvents. Stability of HPS formulations can be
adjusted employing known stabilizers of superoxide.
[0372] For HPS formulations, decreasing the pH below approximately
pH 11 can significantly increases the decomposition rate of
superoxide as observed by ultraviolet spectroscopic analysis, by an
accelerated decline in measured hydrogen peroxide concentration
and/or by a visible increase in gas evolution rate. The
decomposition rate of the superoxide can also be slowed by dilution
of the concentrate.
[0373] Various exemplary HPS formulations: Effect of the ratio of
hydrogen peroxide (HP) to superoxide
[0374] In HPS formulations, the ratio of hydrogen peroxide to
superoxide to hydroxide is primarily dependent on cathode activity
and current efficiency for each oxygen reduction process. The ratio
of hydrogen peroxide to superoxide can also be increased by adding
hydrogen peroxide, as bulk chemical or electrochemically generated
solution, to an electrochemically generated HP-superoxide
composition. HPS formulations include those having a ratio of
superoxide to hydrogen peroxide of 3:1 or higher and those having a
ratio of superoxide to hydrogen peroxide of 3:1 or lower. In one
embodiment, designated High superoxide HPS (HHPS), the formulation
contains superoxide and hydrogen peroxide having a molar ratio of
superoxide to hydrogen peroxide in the range of 5:1-3:1. In another
embodiment, in a subset of HHPS formulations the molar ratio of
superoxide to hydrogen peroxide is in the range of 5:1 to 3.5:1 or
in the range of 5:1 to 4:1. In another embodiment, designated Low
superoxide HPS (LHPS), the formulation contains superoxide and
hydrogen peroxide having a molar ratio of superoxide to hydrogen
peroxide in the range of 3.0:1 to 0.7:1. In another embodiment, in
a subset of LHPS formulations the molar ratio of superoxide to
hydrogen peroxide is in the range of 2.5:1 to 0.7:1 or in the range
of 2:1 to 0.7:1.
3) S-PM-A--PAA+Singlet Oxygen+Superoxide Formulation-High Oxidation
Reactivity
[0375] S-PM formulations contain superoxide and peroxyacetic acid
which produces singlet oxygen and optionally other reactive
species. S-PM formulations are prepared by addition of an acetyl
donor. S-PM* formulations similar to S-PM formulations can be made
using acyl donors other than acetyl donors. In a specific
embodiment, S-PM-A, and alternatively S-PM*-A formulations, contain
superoxide and a peroxyacetic acid composition that produces
singlet oxygen at high efficiency. Combining superoxide with
peroxyacetic acid and singlet oxygen significantly enhances the
formulation's oxidation activity relative to PM or PM* formulations
as shown by an enhanced rate of oxidation of organic material,
exemplified by dye oxidation [e.g., methylene blue dye oxidation].
The selectivity for oxidation of chemical species relative to
biocidal activity of S-PM-A or S-PM*-A formulations is increased
relative to PM or PM* formulations. S-PM-A and S-PM*-A formulations
are more preferred for applications involving oxidation of chemical
species, rather than applications for disinfection or other
antimicrobial applications.
Composition
[0376] S-PM-A is made by first producing an alkaline hydrogen
peroxide-superoxide solution with an electrochemical reactor, as
described for HPS formulations with the exception that the molar
ratio of superoxide to hydrogen peroxide in the alkaline hydrogen
peroxide-superoxide solution used ranges from 5:1 to 3:1 and more
preferably is 5:1 to 3.5:1 or 5:1 to 4:1. A peroxyacetic acid
concentrate containing superoxide is then formed by addition of an
acetyl donor to the alkaline hydrogen peroxide-superoxide. This
mixture is a precursor formulation containing peroxyacetic acid as
a parent oxidant to form singlet oxygen on activation. Activation
of this precursor peroxyacetic acid-superoxide formulation by
adjusting the pH to 6-12 generates singlet oxygen. S-PM*-A
formulations are similarly made employing an acyl donor other than
an acetyl donor to prepare the precursor formulation.
[0377] For S-PM-A generation, an exemplary reactor output stream
contains 0.4 wt % sodium peroxide, 1.5 wt % sodium superoxide, 1.4
wt % sodium hydroxide, 0.2 wt % sodium sulfate, pH 13.1 having an
ORP of 80 mV vs SHE. It will be appreciated that alternate cation
components, other than sodium ions, can be employed in the
formulations without significant detriment, as long as solubility
of components is maintained. The reactor output stream is reacted
with an acetyl donor, such as triacetin, pure liquid, in a 1:3
molar ratio of hydrogen peroxide to acyl donor reactive groups (1:1
molar ratio of hydrogen peroxide to triacetin which has three
acetyl group). The resulting precursor formulation or concentrate,
contains up to 0.86 wt % superoxide anion, 0.52-0.53 wt %
peroxyacetic acid, 0-0.005 wt % hydrogen peroxide, 0.64-0.65 wt %
glycerol, 0.84-0.85 wt % acetic acid, about 0.13 wt % sulfate ion,
0.80-0.81 wt % sodium ion and a pH of 12.9-13.1. The pH of this
precursor concentrate is greater than the activation pH range for
forming singlet oxygen of pH 6-12. The pH of the precursor
concentrate is adjusted to pH 10-11 to activate the formation of
singlet oxygen by adding acid to form the S-PM-A formulation. For
example, to the precursor described above, sulfuric acid, 98 wt %,
in about a 0.40:1 molar ratio relative to the initial molar
concentration of sodium hydroxide in the electrochemical reactor
output is added. The higher pH precursor concentrate can be stored
after production, and activated by addition of acid after storage
to generate the S-PM-A formulation. S-PM-A formulations exhibit ORP
of 260-400 mV vs SHE which increases over time (presumably as
single oxygen and possibly other reactive species form) with a
concomitant decrease in pH. The concentrate's pH can optionally be
lowered to a pH within the activated singlet oxygen forming range
by adding additional acid.
[0378] As noted for generation of PM formulations, S-PM-A
formulations can also be produced by first adding acid to the
reactor output containing superoxide and peroxide to lower the pH
to the activation pH range of 6-12 and thereafter add the acetyl
donor (or acyl donor for S-PM*-A formulations). In this case,
singlet oxygen formation can begin on addition of the acyl donor.
S-PM-A and S-PM-*-A formulations can be diluted as desired.
4) S-PM-B--PAA+Singlet Oxygen+Superoxide Formulation-High ORP
[0379] S-PM-B formulations are derivatives of S-PM-A formulations
having significantly higher ORP, but lower oxidative reactivity to
organic materials than S-PM-A formulations as shown in ORP data
(e.g., FIG. 23A) and methylene blue oxidation data (FIG. 24B) As a
result, S-PM-B formulations have higher selectivity for biocidal or
disinfection activity over oxidation of chemical species compared
to PM solutions. S-PM*-B formulations exhibit similar selectivity
as biocides with higher ORP compared to comparable S-PM*-A
formulations and PM* formulations.
Preparation and Composition
[0380] S-PM-B formulations are prepared as the A-PM-A formulations
employing electrochemically generated mixtures of superoxide and
hydrogen peroxide (molar ration superoxide: hydrogen peroxide as
noted for S-PM-A formulations), however it is preferred to add the
acetyl donor to the reactor output to form the precursor
concentrate containing peroxyacetic acid prior to addition of acid
to lower the pH. Additionally, the pH of this precursor concentrate
containing peroxyacetic acid is adjusted to pH 6-11 to activate the
formation of singlet oxygen. Preferably the pH is initially
adjusted to 10-11. After this pH adjustment, the ORP of the
formulation is initially 260-400 mV vs SHE. Over 20-30 minutes the
ORP increases significantly with a concomitant decrease in pH. The
ORP stabilizes for a period of time at a significantly elevated ORP
of about 825-875 mV vs SHE at pH 10, before the ORP starts to
decline as the oxidants are consumed or decompose. The elevated ORP
is characteristic of the S-PM-B formulations and persists for up to
approximately 60 minutes before declining The maximum ORP and the
rate of decline depend on oxidant solution pH and concentration.
[see ORP vs pH vs time data] Reducing pH within the activation pH
range and reducing concentration by dilution lead to longer
lifetimes of the elevated ORP state for this composition. The
enhanced ORP is produced in an activated pH range of 6-11.
[0381] Thus, the S-PM-B formulations are prepared by first
producing an alkaline hydrogen peroxide-superoxide solution with an
electrochemical reactor and having a molar ratio of superoxide to
hydrogen peroxide of 5:1 to 3:1 and forming a peroxyacetic acid
concentrate containing superoxide by addition of an acetyl donor to
the alkaline hydrogen peroxide-superoxide (a precursor formulation
for the S-PM-A formulations). This forms a precursor formulation
containing peroxyacetic acid as a parent oxidant to form singlet
oxygen. Activation of this precursor peroxyacetic acid-superoxide
formulation by addition of acid such that the pH is in the range of
6-11 followed by a delay of at least about 20 minutes provides the
S-PM-B formulation. The S-PM-B formulation can be decreased in pH
to 6-9 or diluted to extend its activity. S-PM*-B formulations are
made employing an acyl donor other than an acetyl donor to prepare
the precursor formulation. The change in ORP with time indicates
the formation of one or more reactive species in addition to
superoxide, peroxyacetic acid and superoxide.
[0382] It will be appreciated that S-PM-A or S-PM*-A formulations
with pH of 6-11 will convert to S-PM-B or S-PM*-B formulations with
time. Thus, the S-PM-A or S-PM*-A formulations with pH of 6-11 can
be used in dual application for initial oxidation of chemical
species and later biocide and disinfection.
5) S-PM-C--PAA+Singlet Oxygen+Superoxide Formulation-Extended
Lifetime
[0383] S-PM-C formulations exhibit a long-lasting, elevated ORP
which is intermediate to S-PM-A and S-PM-C formulations by the
interaction of superoxide with singlet oxygen in the presence of
peroxyacetic acid. Similar S-PM*-C formulation are prepared using
an acyl donor other than an acetyl donor. S-PM C and S-PM*-C
formulations contain superoxide and a peroxyacetic acid and produce
singlet oxygen at high efficiency, but the superoxide to
peroxyacetic acid ratio is lower compared to the corresponding
S-PM-A and S-PM-B formulations. S-Pm-C and S-PM*-C formulations
exhibit significantly higher ORP and comparable oxidative
reactivity relative to PM formulations. An important difference for
S-PM-C and S-PM*-C formulations is that the elevated ORP can
persist for a period of days, instead of less than 24 hours as in
S-PM-A and S-PM-B formulations. S-PM-C and S-PM*-C formulations
thus provide a residual ORP level that can maintain biostatic
conditions for extended periods of time.
[0384] S-PM-A is made by first producing an alkaline hydrogen
peroxide-superoxide solution with an electrochemical reactor, as
described for HPS formulations with the exception that the molar
ratio of superoxide to hydrogen peroxide in the alkaline hydrogen
peroxide-superoxide solution used ranges from 3.0:1 to 0.7:1. 2.5:1
to 0.7:1 or in the range of 2:1 to 0.7:1.
Composition
[0385] S-PM-C is made by first producing an alkaline hydrogen
peroxide-superoxide solution as described for S-PM-A formulations
with the exception that the molar ratio of superoxide to hydrogen
peroxide in the alkaline hydrogen peroxide-superoxide solution used
ranges from 3.0:1 to 0.7:1. To obtain this ratio of superoxide to
hydrogen peroxide, hydrogen peroxide solution is added to
electrochemical reactor output to decrease the ratio of superoxide
to hydrogen peroxide. An exemplary reactor output stream contains
0.4 wt % sodium peroxide, 1.5 wt % sodium superoxide, 1.4 wt %
sodium hydroxide, 0.2 wt % sodium sulfate, pH 13.1 and ORP of 80 mV
vs SHE. To this reactor output stream is added 3 wt % hydrogen
peroxide such that the modified composition is 0.6 wt % sodium
peroxide, 1.5 wt % sodium superoxide, 1.3 wt % sodium hydroxide,
0.2 wt % sodium sulfate and has pH 12.9-13.1. This modified
hydrogen peroxide-superoxide composition is then reacted with an
acetyl donor, such as triacetin, pure liquid, in a 1:2.4 molar
ratio of hydrogen peroxide to acyl donor reactive groups to form a
high pH precursor to the S-PM-C formulation. S-PM*-C precursor
concentrates are similarly produced using an acyl donor other than
an acetyl donor. It will be appreciated that alternate cation
components, other than sodium ions, can be employed in the
formulations without significant detriment, as long as solubility
of components is maintained.
[0386] The resulting peroxyacetic acid concentrate precursor,
contains up to 0.86 wt % superoxide anion, 0.78-0.80 wt %
peroxyacetic acid, 0-0.007 wt % hydrogen peroxide, 0.77-0.78 wt %
glycerol, 0.88-0.89 wt % acetic acid, about 0.13 wt % sulfate ion,
0.72-0.73 wt % sodium ion and a pH of 12.5-13.0. The pH of this
precursor concentrate is greater than the activated singlet oxygen
forming pH range of 6-12 and the elevated ORP activated pH range of
6-11. The pH of the precursor is then adjusted to pH 6-11 by
addition of acid. Preferably the PH is adjusted to 7-8 to activate
the formation of singlet oxygen. For example, sulfuric acid, 98 wt
%, in about a 0.45:1 molar ratio relative to the initial molar
concentration of sodium hydroxide in the electrochemical reactor
output is added to achieve pH 7-8. The ORP of the resulting S-PM-C
formulation with pH 7-8 is 680-720 mV vs SHE which then increases
over about 4 hours, with a concomitant decrease in pH, to a
stabilized ORP of 770-800 mV vs SHE at pH 7. The pH of the
concentrate can optionally be lowered, raised or held constant
within the activated singlet oxygen forming range by adding
additional acid or base. The elevated ORP of the S-PM-C formulation
remains nearly constant at constant pH for about 34 hours when the
formulation contains 0.2-0.3 wt % peroxyacetic acid. The ORP of the
formulation then continues to decline slowly with time, but can
persist above 740 mV for 45 hours or more.
[0387] FIGS. 23A and B illustrate the effect on ORP as a function
of time of variation of initial molar ratio of PAA: superoxide
(noting that amount of PAA present in formulation is directly
related to the amount of hydrogen peroxide in the precursor
hydrogen peroxide+superoxide precursor employed) in S-PM
formulations. In FIG. 23A ORP is shown as a function of time up to
500 minutes. In FIG. 23B ORP data is shown for the same formulation
at time up to 2400 minutes (40 hours). The formulations all
contained 28.5 mM PAA at an initial pH of 7. In FIG. 23A,
formulations vary by molar ratio of PAA:superoxide, with 1:4.5
(solid circles); 1:3.1 (solid diamonds); 1:2.4 (solid squares) and
1:1.9 (solid triangles). In FIG. 23B, in addition to the
formulations with varying molar ratio of PAA:superoxide, the ORP of
a formulation containing PAA and singlet oxygen with no superoxide
pH 7 (a PM formulation, gray open circles, ORP .about.600 mV vs.
SHE) and the ORP of the reactor output containing
hydrogen+superoxide at pH 9 (black open circles, increasing rapidly
to ORP .about.900 mV vs. SHE). The ORP of the formulation having
molar ratio of PAA:superoxide of 1:3.1 (about 1:3) increases over
about 7 hours to close to 800 and persists for over 40 hours above
700. The ORP of the formulation having molar ratio of
PAA:superoxide of 1:4.5 increases more rapidly to OORP of about
1000, but declines to below 800 by about 7 hours.
[0388] FIG. 23C illustrates the rate of methylene blue oxidation by
S-PM formulations as a function of molar ratio of PAA:superoxide.
MB oxidation rate assays are described in Example 9. Formulations
have 25 mM PAA initial concentration at pH 7 and molar ratio of
PAA: superoxide of 1:4.5 (solid squares); 1:2.4 (solid diamonds)
and open circles is a PM formulation (no superoxide).
[0389] FIGS. 24A and B illustrate the rate of methylene blue
oxidation for PM formulation (FIG. 24A, solid circles), S-PM
formulation (molar ratio PAA:superoxide of 1:4.5) (FIGS. 24A and B,
solid squares) and an S-PM-B formulation (molar ratio
PAA:superoxide of 1:4.5) (FIG. 24, solid triangles).
6. Further Activation of Formulations Described in 1-5 Above.
[0390] PM, HPS, and various S-PM formulations can be further
activated to generate additional reactive oxygen species and/or
other reactive species. Activation includes, among others:
[0391] Ultraviolet light, catalyst, ultrasound, sonic cavitation
and microwave (sonic and electromagnetic energy):
[0392] Energy transfer from a material (e.g., a photo-activated dye
or an activated semiconductor surface activated by light or an
electrical field); or
[0393] Thermal activation (heating).
[0394] Benefits of the additionally activated formulation are
demonstrated in comparative ORP measurements, oxidation experiments
and biocidal data.
[0395] Further activation can be applied to each PM, HPS or various
S-PM formulations after its generation by pH adjustment (to form
singlet oxygen) or by mixing components (HPS formulations).
Alternatively, a step of further activation can be applied to high
pH peracid containing precursors the pH or which is thereafter
adjusted to activate singlet oxygen formation. Further activation
can be applied to a formulation before, after or at the same time
that it is dispensed into the environment in which the formulation
is to be used or into contact with a substrate or environment which
is to be treated with the formulation. For example, a formulation
can be subject to a brief period of UV irradiation before
dispensing or as it is being dispensed for use. For example, a
formulation can be subject to microwave irradiation of ultrasound
before dispensing or as it is being dispensed for use. For example,
a formulation can be heated for a selected time before it is
dispensed or can be employed in its application at a temperature
higher than ambient.
Example 21
UV Activation of PM Formulations
[0396] UV light-activated PM formulations containing peroxyacetic
acid exhibit an increased oxidative reactivity over PM
formulations. After UV light irradiation of the formulation ceases
the formulation retains an elevated activity level for a period of
time (about 40 minutes in the examples below) before returning to
the activity level of the peroxyacetic acid remaining in the PM
formulation. The activation methods described can also be applied
to PM* formulations which contain peracids other than peroxyacetic
acid.
[0397] A flow-through UV irradiation device can be added to the
output of an oxidant production or dosing system (such as those
illustrates in the figures herein) with little impact on the
process design making this activation method feasible for scaleup.
A flow-through UV irradiation device can alternatively be
positioned immediately upstream of the point of use of a
formulation to be activated, particularly if there is a long run
between the oxidant production apparatus and the point of use.
[0398] There is relatively little loss of peracid (e.g., 5-10%
reduction) caused by UV irradiation, thereby not significantly
increasing chemical consumption cost. The brief UV irradiation time
also contributes relatively little power cost to the process cost.
Clean, non-fouling formulation comes in contact with a UV lamp or
window thereby minimizing cleaning and maintenance cost for the UV
irradiation device.
A. Batch UV Activation Procedure:
[0399] Conducted at about room temperature, 15-25.degree. C. is a
typical range (PAA=peroxyacetic acid). [0400] 1. 10.4 mL of a PM
formulation containing 22.7 g/L PAA was diluted to 96 mL and 2.46
g/L PAA as measured by iodometric titration (HACH method). [0401]
2. 80 mL of the diluted PM formulation was placed in a 100 mL glass
beaker. [0402] 3. A UV pen lamp was immersed in the PM formulation
and turned on to irradiate the formulation for 4.5 minutes. During
irradiation the formulation was gently stirred with the UV pen
lamp. After irradiation the PAA concentration of the formulation
had decreased by about 300 mg/L to 2.13 g/L PAA as measured by
iodometric titration. [0403] 4. Immediately after irradiation the
formulation was used directly, correcting for the decrease in PAA
concentration, or further diluted to a point of use concentration.
The UV-activated PM formulation can be dosed into a solution or
applied to a surface to be treated. UV-enhanced oxidative activity
of the activated PM formulation persisted for up to approximately
40 minutes in this example.
[0404] The solution pH, ORP and oxidant concentration, measured as
PAA, were monitored over time in the above example:
[0405] Before UV irradiation: 2.46 g/L PAA, pH=9.5, ORP=423 mV (vs
SHE); About 1 minute after UV irradiation ceased: 2.13 g/L PAA,
pH=9.0, ORP=489 mV (vs SHE); 20 minutes after UV irradiation
ceased: 2.02 g/L PAA, pH=8.9, ORP=493 mV (vs SHE); and 40 minutes
after UV irradiation ceased: 2.13 g/L PAA, pH=8.9, ORP=497 mV (vs
SHE).
[0406] The above measured decrease in PAA concentration after UV
irradiation followed by at least a partial recovery of the oxidant
concentration was a consistent result for freshly made PM
formulations. The oxidant concentration after UV irradiation is not
necessarily just due to PAA. For example, after three UV
irradiation cycles on a PM formulation prepared by the same
procedure the titrated oxidant molar concentration increased by a
factor of 1.6 times.
[0407] The same UV irradiation process as employed for PM
formulations was conducted on a "merchant" PAA solution containing
2.2 g/L PAA and 2.2 g/L hydrogen peroxide adjusted to pH 9.0. In
contrast to the activation observed with irradiation with PM
formulations, there was no change to the initial ORP of 358 mV (vs
SHE) at pH 9.0 after 4.5 minutes of UV irradiation on irradiation
of the "merchant" PAA solution.
B. Methylene Blue Dye Oxidation with UV-Activated PM
Formulations--Batch Method
[0408] A PM formulation was prepared by the method described in A
above. Prior to UV irradiation the pH of the formulation was
adjusted to 9.3 resulting in a pH of 9.1 after 4.5 minutes of UV
irradiation.
[0409] Activated PM formulation (2.0 mL) was added to 2.0 mL of a
100 mg/L methylene blue dye solution (25 mM PAA) and allowed to
react at room temperature. A control PM formulation (25 mM PAA)(2.0
mL) was also added to 2.0 mL of the 100 mg/L methylene blue dye
solution The resulting test solutions initially contained 1.90 g/L
PAA and 50 mg/L methylene blue at about pH 7-8. Methylene blue dye
was oxidized (as assessed by the rate of dye decolorization) by
UV-irradiated PM formulation and the non-irradiated PM formulation.
UV-irradiated PM formulation showed a significant enhanced rate of
dye oxidation compared to the control upon dosing of about 20%
(data not shown). The UV-irradiated PM formulation exhibited a
fast-acting bleaching activity which was not observed for any other
PAA-oxidant system examined by this method. Between 35-60 minutes
after dosing, the rate of methylene blue decolorization by the
UV-activated formulation decreased to a rate similar to, or slower
than that of PM formulation control.
[0410] UV irradiation of PM formulations resulted in both increased
ORP and increased reactivity with methylene blue dye compared to
non-irradiated PM formulations.
[0411] The UV pen lamp used in the above examples emits a mercury
vapor emission wavelength of 258 nm with a fluence rating of 80
Js.sup.-1 cm.sup.-2 in clear water. The immersed portion of the
lamp is about 4.0 cm long and 1.3 cm in diameter providing about
8.2 cm.sup.2 lamp area in direct contact with the solution. The 258
nm wavelength is in the range known to dissociate the oxygen-oxygen
bond of peroxides into radicals. For example, hydrogen peroxide is
dissociated into two hydroxyl radicals, which is the basis of the
UV-hydrogen peroxide advanced oxidation process (AOP). PAA is known
to be similarly dissociated on irradiation with UV light of
wavelength of around 258 nm into hydroxyl and acyloxy radicals in
an AOP.
[0412] Acyloxy radical is known to undergo decarboxylation forming
methyl radical and carbon dioxide. Methyl radical can react with
molecular oxygen to form methyl peroxy radical. All of these
radical species are typically transient and short-lived. AOP
applied to hydrogen peroxide or PAA is effective only during
irradiation by UV light and does not result in enhanced oxidative
activity in the absence of UV light. This is in contrast to the
retained enhanced oxidative activity observed over a significant
and useful time period after irradiation of PM formulations is
ended. Continuous irradiation of the PM formulations is not
required to obtain activity enhancement.
[0413] For PM formulations irradiated by UV light an elevated
oxidative activity persists after UV irradiation has ceased. While
not wishing to be bound by any particular theory, it is currently
believed that in UV-activated PM formulations, UV-generated radical
species are stabilized by other constituents present or may react
with other formulation constituents to form other reactive species
with longer half lives to account for the observed retention in
activity after irradiation is ended. Other constituents unique to
the PM formulations include singlet oxygen and glycerol. Singlet
oxygen may also be directly affected by UV irradiation.
C. Continuous Dosing Apparatus and Process--UV-Activated PM
Formulations
[0414] In a continuous UV-activated oxidant production or dosing
process PM formulations pass through a suitable flow-through UV
apparatus. The total UV irradiation energy can be adjusted by
oxidant solution residence time in the UV apparatus and the fluence
of the UV source relative to the concentration of the oxidant
solution and activity required for the application. This same
approach applies to a PeroxyMax-Superoxide oxidant production and
UV-activation process.
Example 22
Catalyst Activation of PM Formulations
[0415] Catalyst-activated PM formulations exhibit an increased
oxidative reductive potential (ORP) compared to PM formulations.
This "activation" method was initially observed when municipal tap
water, which contained copper originated from contact with copper
pipes was used for making formulation. Catalyst activation leading
to dramatically elevated ORP's was also observed during the
treatment of produced water from oil and gas production wells which
is believed to be the result of metals in the produced water.
[0416] To activate the PM formulation a suitable catalyst is added.
Catalyst can be added to the output of an oxidant production or
dosing apparatus with little impact on the process design.
Alternatively the oxidant solution can be added to a target liquid
stream, surface or environment to be treated which possesses
materials or surfaces suitable to act as "activation" catalysts. In
these cases the catalyst can be selectively added or may be
inherently present in the target to be treated.
[0417] A. Batch Catalyst Activation Procedure:
[0418] Conducted at 25.degree. C. [0419] 1. 2.0 mL PM formulation
containing 22.0 g/L PAA was diluted to 20.0 mL with distilled
water, including pH adjustment with 0.2 mol/L NaHSO.sub.4, to make
2.20 g/L PAA oxidant solution. [0420] 2. 2.0 mL PM formulation
containing 22.0 g/L PAA was diluted to 20.0 mL with tap water,
including pH adjustment with 0.2 mol/L NaHSO4, to make 2.20 g/L PAA
oxidant solution. The tap water contained 16-18 grains of hardness,
about 0.18 mg/L copper, total chlorine of about 0.5 mg/L and pH
7.5.
[0421] The ORP of the above prepared solutions was monitored over
time at 25.degree. C. while maintaining a constant pH of 9.0 by
titrating concentrated NaOH into the samples, if necessary, before
each measurement. The tap water-containing oxidant sample exhibited
a higher initial ORP, which increased significantly over time,
compared to the oxidant sample prepared with distilled water. Dirty
glassware or equipment in contact with the oxidant solution can
have a similar effect to that of the tap water-containing oxidant
example.
[0422] These results show that the PM formulations can be readily
activated by the presence of low levels of impurities (e.g.,
metals) to produce additional reactive oxygen species and other
reactive species, which can be synergistic with the parent oxidant
solution composition.
Example 23
Produced Water Treatment: Catalytic Activation and Biocidal
Performance
[0423] A raw produced water sample was obtained from an undisclosed
location in the Piceance Basin in western Colorado, USA. The
general water characteristics included total dissolved solids near
12 g/L, total organic carbon content around 0.2-0.3 g/L, pH 6.5-6.8
and ORP 130-185 mV (vs SHE). The water had a strong odor of
volatile organic compounds, similar to fuel and aromatic
hydrocarbons, but no perceptible smell of hydrogen sulfide. The
water was turbid with very fine dark grey-black suspended solids,
which was primarily iron sulfide produced as a result of sulfate
reducing bacteria activity. A small amount of free oil phase would
separate to the top of a water sample, appearing as a thin sheen,
after sitting undisturbed at room temperature for 2-3 days.
A. Catalyzed Activation ORP Response in Produced Water
[0424] ORP measurements were conducted on 50 mL of solution in 100
mL glass jars with air tight lids. PM formulation was dosed 5
minutes after preparation as a 20.2 g/L concentrate into the
appropriate amount of raw produced water to give a final volume of
50 mL and the desired initial oxidant dose concentration(dosage
based on PAA concentration). For comparison, a "merchant" PAA
formulation containing 7.78 g/L PAA, 3.47 g/L H.sub.2O.sub.2, and
acetic acid at pH 4.4 was prepared. Oxidant concentrate was
slug-dosed into the raw produced water while mixing and each sample
was mixed for 2 additional minutes. The pH of each sample was
adjusted to pH 7.0 and held constant by titrating in concentrated
sodium hydroxide or sodium bisulfate when necessary. Sample
preparations and analysis were conducted at room temperature,
22.degree. C.
[0425] The PM formulations were dosed into raw produced water
samples at 100 and 500 mg/L PAA initial concentrations. The
"merchant" PAA formulation was similarly dosed at 500 mg/L PAA
initial concentration. The color of all three samples rapidly
turned from grey to pale yellow-orange. A light brown, small
particle floc formed over several minutes and settled over several
hours after measurements were completed. The solutions remaining
after floc settled were clear and nearly colorless. It was also
observed that conducting jar tests with PM formulations having 20
to 500 mg/L PAA doses in larger solution volumes, 1 L or more,
resulted in the formation of significantly larger floc particles,
which could settle within about 1.5 hours.
[0426] Samples containing PM formulations show a very rapid initial
increase in ORP followed by slower changes over the next several
hours. The sample dosed with PM formulation having 100 mg/L PAA
showed an ORP increase to nearly 760 mV (vs SHE) and then a slow
decrease in ORP as the oxidant was consumed over time. The sample
dosed with PM formulation having 500 mg/L PAA showed an ORP
increase after 1 hour contact time from about 890 mV to over 1000
mV (vs SHE) and the ORP remained above this value for nearly 23
hours after the initial oxidant dose (after 19.5 hours the ORP
started to slowly decline). The "merchant" PAA formulation
exhibited a brief, initial increase in ORP to around 670 mV, but
rapidly settled in less than 8 minutes to a lower, constant
potential of 470 mV (vs SHE).
[0427] For samples treated with PM formulations, the magnitude of
increase in ORP and its duration correlates with the initial
oxidant dose, oxidant consumption rate and oxidant residual. At 180
minutes the residual oxidant concentration was measured in each
sample by iodometric titration and reported as PAA. The samples
having PM formulation dosed at 500 mg/L and 100 mg/L initial PAA
doses had total oxidant residuals, as PAA, of about 160 mg/L and 30
mg/L, respectively. The "merchant" PAA 500 mg/L initial dose had a
total oxidant residual, as PAA, of about 160 mg/L. The sample dosed
with "merchant" PAA did not exhibit elevated ORP.
[0428] Samples dosed with PM formulation at 10 and 20 mg/L PAA
initial concentration exhibited some effect on ORP, but the oxidant
was consumed rapidly. These examples are reported in the biocidal
efficacy tests below.
[0429] Components of the water samples functioned to catalyze
oxidant activation as evidenced by the change in ORP observed in
treated samples. Without wishing to be bound by any particular
theory of action, component expected to be acting as catalysts in
the produced water samples could include the iron sulfide suspended
solids or dissolved transition metals such as copper, iron and
manganese. Iron sulfide is a good catalyst candidate since the iron
is in the reduced, ferrous, oxidation state, which is the preferred
oxidation state for Fenton-like catalysts. The iron sulfide is
oxidized by the PM formulation oxidants as evidenced by the rapid
change in sample color from dark grey-black to a light brown
insoluble material characteristic of ferric oxyhydroxides. Copper
and manganese could also contribute significant catalyst
activity.
B. Biocidal Performance in Produced Water
[0430] Biological control is one of the most critical issues in oil
and gas exploration and production. Biological control is essential
prior to sending water into a well as makeup water in drilling
muds, hydraulic fracturing fluids and flood water. Similarly,
biological control is necessary upstream of water treatment
processes or prior to disposing of produced water, flowback water
or other process waste water by deep well injection. Without
effective biological control microorganisms from formation and
surface environments, particularly sulfur-reducing, acid-forming
and slime forming bacteria, will foul and degrade well casings,
corrode pumps and equipment and foul the formation leading to
accelerated loss of reservoir permeability and productivity.
Oxidizing biocides are a fast-acting line of defense and represent
a significant expense in operations. Oxidizing biocides should be
very active and have a limited lifetime with no reactive residuals
so that they do not interfere with non-oxidizing biocide chemicals
used to provide longer-term biostatic conditions.
[0431] Biocidal efficacy tests of PM formulation with produced
water samples (as in A above) were conducted on 50 mL of solution
in 100 mL glass jars with air tight lids. PM formulations were
dosed at 10 mg/L and 20 mg/L initial concentration of PAA. PM
formulations were diluted with distilled water to 1.01 g/L five
minutes after its preparation as a 20.2 g/L concentrate. Dilution
allowed for a more accurately measured quantity of oxidant to be
dosed on a PAA basis into the appropriate amount of raw produced
water to give a final volume of 50 mL. Similarly, a "merchant" PAA
formulation containing 7.78 g/L PAA, 3.47 g/L H.sub.2O.sub.2, and
acetic acid at pH 4.4 was prepared and diluted 20-fold with
distilled water and dosed on a PAA basis. A topical hydrogen
peroxide solution was diluted to 1.00 g/L H.sub.2O.sub.2 and a
bleach solution was diluted to 1.00 g/L sodium hypochlorite (NaOCl)
for more accurate dosing. A UV-activated PM formulation was
prepared as described in Example XX producing an activated
formulation containing 2.1 g/L PAA that was dosed into samples
immediately after UV irradiation. Oxidant formulations were
slug-dosed into the raw produced water while mixing and each sample
was mixed for 5 additional minutes. Microbial tests were conducted
after a 1 hour contact time. Sample preparations were conducted at
room temperature, 21-23.degree. C.
[0432] Microbial analysis was conducted using SaniCheck B dip
slides for general bacteria counting from Biosan Laboratories, Inc.
Dip slides were immersed in the sample solution for 3-5 seconds,
excess liquid drained off and finally incubated for 30 hours at
28-30.degree. C. as described by the product instructions. The
colony density developed on the dip slides was compared to a
conversion chart scaled in 1 log increments up to 10.sup.7 cfu/mL
bacteria concentration. Results of these assays are summarized in
Table 4.
TABLE-US-00004 TABLE 4 Antimicrobial Activity of Oxidant
Formulations Oxidant Raw Water Treated Water Concentration,
Bacteria Bacteria Oxidant Type mg/L Count, cfu/mL Count, cfu/mL
None 0 10{circumflex over ( )}7 na H2O2 10 10{circumflex over ( )}7
10{circumflex over ( )}6 "merchant" PAA 10 10{circumflex over ( )}7
10{circumflex over ( )}5 NaOCl 10 10{circumflex over ( )}7
10{circumflex over ( )}4 PeroxyMax PAA 10 10{circumflex over ( )}7
10{circumflex over ( )}3 PeroxyMax PAA 20 10{circumflex over ( )}7
10{circumflex over ( )}2 UV-Activated 10 10{circumflex over ( )}7
10{circumflex over ( )}4 PeroxyMax PAA
[0433] PM formulation had the most effective biocidal activity in
the produced water. Hydrogen peroxide exhibited very little
biocidal activity and was not expected to contribute significantly
to the biocidal activity of the "merchant" PAA formulation. NaOCl
provided the second-best biocidal activity. UV-activated PM
formulation was similar in biocidal efficacy to NaOCl. UV-activated
PM formulation had been demonstrated to be a more active oxidant
than PM formulation in clean water tests, but exhibited lower
activity than PM formulations in these biocide assays. The lower
biocide activity of UV-activated PM formulation is consistent with
the elevated reactivity of UV-activated PM formulation for other
organic and inorganic contaminants in the produced water which
leads to less selective towards microbes. This higher oxidative
activity on UV activation is expected to be useful for waste water
treatment processes where the degradation and removal of chemical
contaminants and volatile organic compounds is desired for water
reuse or enhancing biological treatment processes.
[0434] For the oxidants tested in Table 4 at 10 mg/L and 20 mg/L
oxidant doses, the greatest oxidative color change in the samples
(assessed by visual comparison) for the dark suspended iron sulfide
material occurred with PM formulations. The color change was only
partial, even at 20 mg/L dose, indicating that much of the iron
sulfide was not oxidized. Hydrogen peroxide and NaOCl had no
detectable effect on the dark iron sulfide material and "merchant"
PAA fell in the middle of the range by visual comparison.
Example 24
Exemplary General Water Treatment Process
[0435] FIG. 25 illustrates a exemplary water treatment process
employing a reactive oxygen formulation of this invention.
[0436] Referring to FIG. 25, water to be treated enters the
treatment process [2501] and treated product water exits 2520,
illustrated by exemplary ouputs 2520a-d of different quality. The
influent can be from any source, directly from a source of
production, a side-stream or slip-stream of a process, or from an
impoundment or storage vessel (e.g., tank or lagoon) or may have
undergone pre-processing such as grit and solids separation, gas
recovery and/or pH adjustment.
[0437] Pre-treatment steps 2502 are optionally applied. For
example, volatile materials (e.g., volatile organic compounds,
dissolved gases, ammonia) are optionally removed by air stripping
[2502a]. For example, readily oxidizable materials (e.g., dissolved
or suspended metals like reduced iron and manganese) can optionally
be pre-oxidized [2502b] with oxygen in air to reduce the
consumption of oxidants used downstream. This step is excluded when
it is beneficial to deodorize or oxidize and degrade gaseous
materials in the liquid phase or if the liquid stream is
susceptible to foaming. One or more steps of filtering can also be
applied. Reactive oxygen species formulations are added 2503 to
oxidize materials, provide a biocide, promote flocculation and/or
enhance filtration and biological treatment performance. Reactive
oxygen species formulations can also contain alkalinity or acid for
pH adjustment, precipitants, coagulants, antiscalants and
demulsifiers. A separate source of acid or base can optionally be
provided 2504.
[0438] Biological treatment 2505 (aerobic and/or anaerobic) can be
used to remove dissolved and suspended organic materials, metals,
nutrients (e.g., nitrates, phosphates, sulfates) and reactive
species oxidation byproducts. Clarification 2506 is used to remove
free oil and grease, suspended solids (e.g., microflocculated
solids and biological detritus), colloidal and dissolved organics
and metals (e.g., Fe, Mn). Clarification methods can include
coagulation and flocculation, electrocoagulation, flotation,
settling, centrifugation, particle filtration (e.g., sand, dual
media, micro- and ultra-filtration) and absorptive media. Forward
osmosis filtration can also be used as an alternative clarification
process.
[0439] ROS antimicrobial treatment 2507 can optionally be used as a
final biocide prior to product water output as a biocidal
pre-treatment to a water softening process 2508; and as a biocidal
pre-treatment to a water softening 2508 and desalination process
2509. antimicrobial treatment 2507 can alternatively be used to
increase the peroxide and concentration prior to wet peroxide and
wet ROS oxidation treatment 2510.
[0440] A water softening process can be provided 2508 including
methods such as lime softening, ion exchange, absorptive media,
nanofiltration and electro-capacitive deionization. Desalination
process 2509 can include methods such as nanofiltration, reverse
osmosis, forward osmosis, membrane distillation, thermal
distillation, multi-effect distillation, electro-capacitive
deionization, and electrodeionization.
[0441] Additional optional treatment 2510 can be provided dependent
upon water quality desired. For example, wet peroxide oxidation
treatment including elevated temperature, elevated pressure, a
catalyst, a catalytic surface, and combinations of such conditions
can be applied to promote wet peroxide. An additional step of wet
ROS oxidation of organic and inorganic materials can also be
applied.
[0442] FIG. 25 illustrates a general example of a treatment process
where each stage can be incorporated, excluded or moved to a
different location in the exemplary sequence depending on the
influent composition and product water quality required for reuse,
repurposing, discharge or further processing.
* * * * *
References