U.S. patent application number 13/284558 was filed with the patent office on 2012-11-01 for chemical oxidation method and compounds.
This patent application is currently assigned to EnChem Engineering, Inc.. Invention is credited to Raymond G. Ball.
Application Number | 20120277516 13/284558 |
Document ID | / |
Family ID | 47068436 |
Filed Date | 2012-11-01 |
United States Patent
Application |
20120277516 |
Kind Code |
A1 |
Ball; Raymond G. |
November 1, 2012 |
CHEMICAL OXIDATION METHOD AND COMPOUNDS
Abstract
A method and system for the reduction of contamination in soil
and groundwater is provided. Cyclic oligosaccharides can be used,
for example, to carry oxidants, carry activators, solubilize
organic contaminants and promote biodegradation.
Inventors: |
Ball; Raymond G.; (Newton,
MA) |
Assignee: |
EnChem Engineering, Inc.
Newton
MA
|
Family ID: |
47068436 |
Appl. No.: |
13/284558 |
Filed: |
October 28, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12464478 |
May 12, 2009 |
8049056 |
|
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13284558 |
|
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61052447 |
May 12, 2008 |
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Current U.S.
Class: |
588/315 ;
405/128.75 |
Current CPC
Class: |
B09C 2101/00 20130101;
C02F 1/72 20130101; C02F 2101/366 20130101; B09C 1/08 20130101;
C02F 1/78 20130101; B01J 20/24 20130101; C02F 2101/306 20130101;
C02F 1/725 20130101; C02F 2101/363 20130101; C02F 2103/06 20130101;
B09C 1/02 20130101; C02F 2101/322 20130101; B09C 1/002 20130101;
C02F 2101/38 20130101; C02F 2101/327 20130101 |
Class at
Publication: |
588/315 ;
405/128.75 |
International
Class: |
A62D 3/38 20070101
A62D003/38; B09C 1/08 20060101 B09C001/08; A62D 3/33 20070101
A62D003/33 |
Claims
1-85. (canceled)
86. A method of reducing the concentration of an organic compound
in contaminated material, the method comprising: introducing an
oligosaccharide to the contaminated material; introducing ozone to
the contaminated material; and forming a clathrate from the ozone
and the oligosaccharide.
87. The method of claim 86 further comprising the step of
introducing at least one oxidant in addition to the ozone to the
contaminated material.
88. The method of claim 87 wherein the at least one oxidant
comprises at least one of a persulfate compound, a permanganate
compound, a percarbonate compound and a peroxide compound.
89. The method of claim 87 further comprising introducing an
activator to the material.
90. The method of claim 86 wherein ozone is introduced to the
contaminated material prior to introducing the oligosaccharide.
91. The method of claim 86 wherein the oligosaccharide is
introduced to the contaminated material prior to introducing the
ozone.
92. The method of claim 86 wherein the ozone and the
oligosaccharide are simultaneously introduced to the contaminated
material.
93. The method of claim 86 further comprising the step of oxidizing
at least a portion of at least one organic contaminant present in
the contaminated material.
94. The method of claim 86 wherein the ozone and the
oligosaccharide are introduced to the contaminated material through
different injection wells.
95. The method of claim 86 wherein the ozone and the
oligosaccharide are introduced to the contaminated material through
a common injection well.
96. The method of claim 86 further comprising altering a rate at
which the ozone is released from the clathrate by altering the pH
of a fluid comprising the clathrate.
97. The method of claim 86 further comprising desorbing or
solubilizing an organic compound from the material with the
clathrate.
98. A method of reducing the concentration of an organic compound
in contaminated material, the method comprising: forming a
clathrate solution comprising an ozone and an oligosaccharide; and
introducing the clathrate solution to the contaminated
material.
99. The method of claim 98 further comprising the step of
introducing at least one oxidant in addition to the clathrate to
the contaminated material.
100. The method of claim 99 wherein the at least one oxidant
comprises at least one of a persulfate compound, a permanganate
compound, a percarbonate compound and a peroxide compound.
101. The method of claim 99 further comprising introducing an
activator to the material.
102. The method of claim 98 further comprising the step of
oxidizing at least a portion of at least one organic contaminant
present in the contaminated material.
103. The method of claim 98 further comprising altering a rate at
which the ozone is released from the clathrate by altering the pH
of a fluid comprising the clathrate.
104. The method of claim 98 wherein the clathrate is introduced to
the contaminated material through an injection well.
105. The method of claim 98 further comprising desorbing or
solubilizing an organic compound from the material with the
clathrate.
Description
RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S.
application Ser. No. 12/464,478, filed May 12, 2009, which claims
the benefit of U.S. Provisional Patent Application No. 61/052,447,
titled "Oxidant Stabilization," filed May 12, 2008. Each of these
applications is hereby incorporated by reference herein.
FIELD OF THE INVENTION
[0002] The present invention relates generally to the chemical
oxidation of organic contaminants and, in particular, to the
stabilizing of ozone for the purpose of destroying organic
contaminants.
BACKGROUND
[0003] Both State and Federal governments have issued regulations
governing hazardous organic and inorganic contaminants in the
environment. Subsurface soil and groundwater contamination with
organic and inorganic contaminants has been the concern of State
and Federal government since the 1970's. Action levels and clean-up
standards have been promulgated by both State and Federal
government for numerous organic and inorganic contaminants.
Regulated organic contaminants in the subsurface environment
include, but are not limited to: polychlorinated biphenyls (PCBs);
chlorinated volatile organic compounds (CVOCs) such as
tetrachloroethene (PCE), trichloroethene (TCE), trichloroethane
(TCA), dichloroethene (DCE), vinyl chloride; fuel constituents such
as benzene, ethylbenzene, toluene, xylene, methyl tert butyl ether
(MTBE), tertiary butyl alcohol (TBA), polynuclear aromatic
hydrocarbons (PAHs), ethylene dibromide (EDB); pesticides such as
(but not limited to) DDT; herbicides such as (but not limited to)
silvex. Regulated inorganic contaminants in the subsurface
environment include: heavy metals, such as lead, arsenic, chromium,
mercury, and silver. The State and Federal regulations that govern
these subsurface contaminants outline a protocol for subsurface
investigation to identify the extent of contamination,
identification of the human health and ecological risk posed by the
contaminants, development of remedial action alternatives for
reducing or eliminating any significant risk posed by the
contaminants, and selection and implementation of remedial measures
to achieve the remediation goals.
[0004] In situ (ISCO) and ex situ (ESCO) chemical oxidation
technologies have emerged as prominent remedial measures due to
cost-effectiveness and timeliness for achieving remediation goals.
This technology can be used alone or in combination with other
complementary technologies, such as soil vapor extraction (SVE) for
removal of volatile organic compounds from the unsaturated zone,
multi-phase extract for removal of organic contaminant from the
unsaturated and saturated zones, or vertical recirculation systems
in the saturated zone. ESCO can be applied by excavating subsurface
soil and spraying or mixing chemical oxidants into the soil. ESCO
can also be applied to solid surfaces such as vehicles and
equipment.
SUMMARY OF THE INVENTION
[0005] In one aspect, a clathrate is provided, the clathrate
comprising a host molecule and an ozone guest.
[0006] In another aspect, a method for the stabilization of ozone
is provided, the method comprising adding a cyclic oligosaccharide
and ozone to an aqueous medium to produce an ozone clathrate
solution.
[0007] In another aspect an aqueous solution is provided, the
aqueous solution comprising a clathrate of ozone and a cyclic
oligosaccharide wherein the pH of the solution is between 5.0 and
9.0 and the clathrate concentration is greater than 0.1 mg/L.
[0008] In another aspect a method of reducing the concentration of
organic compound contamination in contaminated material is
provided, the method comprising forming ozone clathrate, providing
the clathrate to the contaminated material, releasing ozone from
the clathrate into solution, and oxidizing the organic compound to
reduce the concentration of the organic compound in the material by
at least 50%.
[0009] In another aspect, a method of reducing the concentration of
an organic compound in contaminated material is provided, the
method comprising forming a clathrate solution comprising ozone and
an oligosaccharide and introducing the clathrate solution to the
contaminated material. The clathrate may be formed either in situ
or ex situ. Similarly, the clathrate may be introduced to the
contaminated material in situ or ex situ. It is contemplated that
this method may include additional steps such as introducing an
oxidant and/or activator in addition to the ozone to the
contaminated material and oxidizing the organic compound to destroy
at least a portion of the compound.
[0010] In another aspect, a method of reducing the concentration of
an organic compound in contaminated material is provided, the
method comprising introducing an oligosaccharide to the
contaminated material, introducing ozone to the contaminated
material, and forming a clathrate from the ozone and the
oligosaccharide. The oligosaccharide and the ozone may be
introduced to the contaminated material in any order or
simultaneously and the introductions may occur in situ or ex situ.
It is contemplated that this method may include additional steps
such as introducing an oxidant and/or activator in addition to the
ozone to the contaminated material and oxidizing the organic
compound to destroy at least a portion of the compound.
[0011] In another aspect, a method of increasing stability of ozone
in water, soil, rock or sediment is provided, the method comprising
forming an ozone/oligosaccharide clathrate solution, and injecting
the clathrate solution into the water, soil, rock or sediment.
[0012] In another aspect, a method of reducing the concentration of
organic contaminants in soil, sediment, water or groundwater using
chemical oxidation is provided, the method comprising injecting a
cyclic oligosaccharide into a borehole at a remediation site,
injecting one or more oxidants into a borehole at the remediation
site, oxidizing at least a portion of the organic contaminants
present at the site, and oxidizing at least a portion of the cyclic
oligosaccharide molecules to reduce the cyclic oligosaccharide to
fragments that can be utilized by microbes as a co-metabolite to
promote biodegradation of the organic contaminant. It is also
understood that the organic contaminant can become more
biodegradable after it is solubilized by the cyclic oligosaccharide
and/or partially oxidized by the oxidant(s).
[0013] The compounds and methods disclosed herein may be used to
remediate organic compound contamination in situ or ex situ. They
may be used in conjunction with known and future methods that
employ various oxidants including, for example, ozone, persulfate,
permanganate, percarbonate and peroxide. Activators may also be
included. In some cases, the ozone can form a superoxide radical to
aid in oxidative processes. Components may be provided (e.g.,
injected) together or separately. The clathrate host can be
recycled and can be recharged with additional ozone.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The above-mentioned and other features of this disclosure,
and the manner of attaining them, will become more apparent and
better understood by reference to the following description of
embodiments described herein taken in conjunction with the
accompanying drawings, wherein:
[0015] FIG. 1 is a graph showing experimental results of ozone
concentration vs. time;
[0016] FIG. 2 is a graph showing experimental results of
trichloroethene concentration versus time;
[0017] FIG. 3 is a graph showing experimental results of
trichloroethene concentration versus time in the presence of
cyclodextrin;
[0018] FIG. 4 is a graph showing experimental results of pyrene
remediation in a soil/groundwater matrix;
[0019] FIG. 5 is a graph showing experimental results of change of
dissolved ozone concentration over time; and
[0020] FIG. 6 is a copy of a photograph depicting the visual
results of an indigo colorimetric ozone test.
DETAILED DESCRIPTION
[0021] The terms "cyclodextrin" (CD) and "derivitized cyclodextrin"
(dCD) are used as they are in the art and include compounds such as
alpha, beta, or gamma cyclodextrin and derivatives thereof such as
hydroxy-propyl beta cyclodextrin (HP-.beta.-CD), amino-propyl
cyclodextrin, carboxy-methyl cyclodextrin (CMCD) and randomly
methylated beta-cyclodextrin (RAMEB). Cyclodextrin includes
derivitized cyclodextrin unless otherwise specified. Cyclodextrins
are cyclic oligosaccharides and, more specifically, cyclic
oligoglucosides.
[0022] The term "microencapsulation" is defined as a method of
controlled release whereby a solid, liquid, or gas is packaged in
minute sealed capsules that release their contents at controlled
rates under the influence of specific conditions. CDs can be
considered as empty capsules of molecular size that form complexes
with guest molecules resulting in an encapsulation process on the
molecular scale.
[0023] A "clathrate" or "clathrate compound" is used herein as it
is used in the art and means an inclusion complex having a lattice
of at least two molecules in which one molecule traps the other.
The two molecules are not covalently bonded to each other but are
held together by weaker forces such as hydrogen bonds. Clathrates
may be referred to as host-guest complexes or inclusion compounds.
An example of a clathrate is a complex of ozone retained within the
interior cavity of a cyclodextrin molecule. Clathrates are not to
be confused with surfactants and need not function as surfactants.
An "ozone clathrate" is a clathrate in which the guest is one or
more ozone molecules. A "cyclic oligosaccharide clathrate" is a
clathrate in which the host is a cyclic oligosaccharide.
[0024] Clathrates, such as cyclodextrin clathrates, can
microencapsulate ozone in aqueous solution, increasing its
solubility and stability. Cyclodextrins are also capable of
desorbing organic and inorganic contaminants from, soils, slurries,
sediment and other materials. These compounds also are believed to
be biodegradable and do not react directly with oxidants used in
chemical remediation. Thus, cyclodextrins (and related compounds)
can provide a biodegradable vehicle for both stabilizing ozone and
desorbing organic contaminants.
[0025] An ozone clathrate can be formed, for instance, by injecting
ozone into water to produce an aqueous solution (e.g., with a
Mazzei injector) and adding a clathrate host component such as an
oligosaccharide (e.g., cyclodextrin). Alternatively, the water may
contain the cyclodextrin prior to injection of the ozone into the
solution. The solution may contain ozone/oligosaccharide clathrate
as well as unassociated ozone and unassociated oligosaccharide.
[0026] In one aspect, a method of stabilizing ozone to improve the
oxidation of organic contaminants is provided. A clathrate
consisting of ozone and a cyclic oligosaccharide, such as
cyclodextrin, can prolong the in situ or ex situ half life of
ozone, attenuate the amount of ozone in solution and provide for an
expanded zone of influence at a remediation site. A clathrate
including ozone may also be more soluble in water than ozone alone.
Thus the clathrate can provide both enhanced stability and enhanced
solubility of ozone. Via a clathrate, ozone can be delivered in a
hydrophobic phase that is suspended in a hydrophilic phase. When a
target contaminant is contacted, the contaminant molecule may be
drawn to the oxidant by the clathrate or the oxidant may be
delivered to the reactive site by the clathrate. The oxidant, which
may be ozone, can be associated with the clathrate, meaning that
the ozone is microencapsulated by the clathrate and carried in the
aqueous solution and through the zone of contamination as a single
ozone clathrate complex. One or more ozone molecules may be
associated with a clathrate molecule and one or more cyclodextrins
may be associated with an ozone molecule. For instance, an ozone
molecule may be retained inside a cyclodextrin molecule. As a
result, the ozone molecule is protected from ambient reducing
agents and its activity can be prolonged. This may provide a
greater zone of influence for a given concentration of oxidant.
[0027] A cyclic oligosaccharide is of a generally toroidal shape
that can form a clathrate by retaining one or more ozone molecules
in the interior cavity of the torus. A host-guest relationship
between the cyclic oligosaccharide and the ozone is formed in which
the ozone is stabilized via its stearic attraction to the cyclic
oligosaccharide. It is believed that as a component of the
clathrate, the ozone is protected from reduction by substances that
would otherwise contact the ozone molecule in solution. These
reducing agents may be numerous in environments such as ground
water and soil. The microencapsulated ozone is isolated from these
non-target reducing compounds, allowing a greater percentage of the
ozone to remain for reaction with target contaminants. For in situ
methods, this stabilization effect allows a greater percentage of
the compound to be transported in the unsaturated or saturated zone
of the subsurface farther away from the injection point, thus
providing for a decreased number of vertical or horizontal
injection points. It is believed that the cyclodextrin clathrate
may also act as a reactor where guest molecules of both contaminant
(e.g., organic solvent) and oxidant molecules (e.g., ozone)
associate with either the hydrophobic cavity or the hydrophilic
hydroxyl groups of the cyclodextrin and come in close contact with
each other. This close stearic interaction can promote reaction
between the contaminant and the oxidant molecule.
[0028] The use of an ozone clathrate (such as ozone/cyclodextrin)
can provide for a stable concentration of ozone in the reaction
zone. For instance, initial ozone concentration in solution may be
significantly lower when compared to the concentration typically
realized upon introduction of a conventional ozone solution. This
means that less ozone may be destroyed by native reducing agents
that are not targets of the remediation. Over time, often a matter
of minutes, the ozone concentration may become higher when a
clathrate is used because the microencapsulated ozone is protected
from reducing agents and is released from the clathrate only when
the unassociated ozone concentration drops below a specific
concentration, for example, 1 ppm or 2 ppm by weight. This chemical
equilibrium between the ozone clathrate and free ozone in solution
can provide a consistent concentration of ozone to the reaction
zone. In some embodiments, the solubility of the organic or
inorganic hydrophobic contaminant may be enhanced by the
introduction of a clathrate and the contaminant can be concentrated
by the oligosaccharide component of the clathrate. This may also
result in more frequent contact between the hydrophobic contaminant
and the ozone molecule because the hydrophobic contaminant may
exhibit an affinity for the oligosaccharide that is hosting the
ozone.
[0029] Examples of cyclic oligosaccharides include cyclic
oligoglucosides such as .alpha.-cyclodextrin, .beta.-cyclodextrin,
.gamma.-cyclodextrin and randomly methylated .beta.-cyclodextrin
(RAMEB). A clathrate comprising hydroxypropyl .beta.-cyclodextrin
(HP-.beta.-CD) in particular has been shown to provide higher and
more stable concentrations of ozone in solution when compared to
ozone alone. Cyclic oligosaccharides may also be used to form
clathrates with other oxidizing, reducing or radical forming
compounds useful in chemical and biological remediation. These
compounds may include, for example, oxygen, hydrogen, peroxide,
persulfate, permanganate or other peroxygen compound. One
embodiment includes an ozone/cyclodextrin clathrate, persulfate and
hydrogen peroxide. In various embodiments, the persulfate may be
either monopersulfate or dipersulfate.
[0030] Compounds capable of forming clathrates may be natural or
synthetic. Examples of compounds capable of forming natural
clathrates include cyclodextrins, carbon nanotubes, ureas, and
zeolites. Natural clathrates may be biodegradable and may exhibit
low, or no toxicity. Many oligosaccharides are biodegradable in
situ. In preferred embodiments the oligosaccharide (e.g.,
cyclodextrin) is stable for more than a day but degrades in less
than a year (half life) in situ. This can provide for efficient
delivery of ozone and desorption of target organic compounds while
avoiding long term residual injectate contamination, such as can
happen with the use of surfactants.
[0031] In one aspect, the present invention relates to the
treatment of material contaminated with undesirable organic or
inorganic compounds that can be destroyed by oxidation. Material
includes, for example, soil, sediment, clay, rock, sand, till and
the like (hereinafter collectively referred to as "soil").
Additional treatable materials include contaminated water and
groundwater found in the pore spaces of soil and rock, process
water resulting from various industrial processes or wastewaters
(e.g., tar sand waste water). Material also includes, for example,
"separate-phase" contaminants such as dense and/or light
non-aqueous phase liquids (NAPL). Material can further include a
surface contaminated with an undesirable organic or inorganic
compound, such as the inside of a pipe through which liquid or
solids flow, or the surface of a natural or synthetic fabric. The
present invention also relates to a solution for the treatment of
suspensions, slurries and solids containing chemical warfare
agents. Treatment may proceed in situ or ex situ. Contaminants may
be treated in the saturated zone, the unsaturated zone or the smear
zone. The use of the clathrate can improve flow rates through the
unsaturated zone without sacrificing hydraulic conductivity that
can result from the use of surfactants and other materials designed
to release contaminant from the material. A clathrate may also
improve results when used with a sparging system. For example, the
clathrate may enhance the solubility of oxygen, ozone or air in a
sparging system, resulting in a greater concentration of reactants
in the reaction zone.
[0032] ISCO and ESCO technologies can use strong oxidizing agents
to treat contaminated soil by chemically degrading recalcitrant and
hazardous chemicals. Such oxidizers include, for example, hydrogen
peroxide, Fenton's reagent, ozone, permanganate, percarbonate,
activated and unactivated persulfates, and other peroxygens. One
key aspect to the ability of an oxidizer to function is its ability
to permeate through the subsurface either above the groundwater
table (unsaturated zone) or below the groundwater table (saturated
zone) while interacting with target compounds throughout the entire
zone of contamination. Oxidizing species, such as ozone and
peroxides have relatively short life times within the subsurface
ranging from minutes with ozone to hours with peroxides.
Persulfates can survive for greater periods, typically reported in
days. In general, there is a desire to have longer lived active
species available for organic species decomposition in order to
increase the zone of reaction while minimizing the number of
injection points throughout the area of subsurface
contamination.
[0033] ISCO technology can be used alone or in combination with
other complementary technologies, such as soil vapor extraction
(SVE) for removal of volatile organic compounds from the
unsaturated zone, multi-phase extraction for removal of organic
contaminants from the saturated zone, vertical or horizontal
recirculation systems in the saturated zone, or air sparging of the
saturated zone. Both ISCO and ESCO technologies can be combined
with different methods of heat application such as radio frequency
heating or steam injection for treatment of soil, water, and
sediment. Also, they can be combined with bioremediation for
enhanced post oxidation treatment.
[0034] Various methods of ISCO delivery have been developed for
different situations and conditions to improve contact between the
contaminant and oxidant. ISCO has been applied to soil and
groundwater treatment for the last decade and the demand for this
technology continues to grow and evolve.
[0035] ESCO can be applied to soil by several methods including a
backhoe, excavator, soil mixing auger, mixing jet, windrow mixer or
excavation and placement into a reactor vessel. ESCO can be applied
to sediment by dredging and mixing in a reactor vessel. ESCO can
also be applied to solid surfaces such as vehicles and equipment by
spraying as described in U.S. Pat. No. 6,459,011, which is hereby
incorporated by reference herein.
[0036] Certain contaminants at concentrations greater than their
aqueous solubility limit exist as non-aqueous phase liquids (NAPLs)
in soil, water or sediment. When in water or an aqueous
environment, it becomes important whether the NAPL has a density
lighter than water or greater than water. If less dense than water
(LNAPLs), the contaminants will float and if more dense than water
(DNAPLs), they will sink. Examples of LNAPLs are petroleum
hydrocarbons such as gasoline, diesel fuel, and fuel oils. Examples
of DNAPLs are various chlorinated organic compounds such as
tetrachlorethene (PCE), trichloroethene (TCE), polychlorinated
biphenyls (PCB) or manufactured gas plant (MGP) wastes. Chemicals
associated with MGP waste include volatile organic compounds (VOCs)
like benzene and toluene, polynuclear aromatic hydrocarbons (PAHs)
like pyrene, tar acids like phenol and cresol, creosote, and coal
tar pitch.
[0037] Ozone can be applied to the unsaturated zone, the saturated
zone, and/or the smear zone. Ozone can be applied to the
unsaturated zone using, for example, vent wells for ozone injection
and/or SVE technology whereby a vacuum is induced in the subsurface
to distribute the ozone through the area of contamination. Ozone
can also be applied to the saturated zone using sparging techniques
whereby ozone is added with air or pure oxygen and sparged into the
groundwater. Ozone is highly reactive and short lived in the
aqueous environment in which soil treatment typically occurs. This
limits the radius of influence from either a vertical or horizontal
injection point. Ozone can react with a great number of
contaminants in a variety of ways including: 1) direct reaction of
ozone with organic compounds, and 2) reaction by free hydroxyl
radicals. The solubility of ozone in aqueous solution is about 14
mM at 20 degrees C.
[0038] There are many factors, such as pH, pressure, temperature,
and ionic strength, which can affect the stability of aqueous
ozone. The stability of an ozone solution is highly dependent on pH
and decreases as alkalinity increases. A higher temperature aqueous
solution yields faster ozone depletion. Also, higher ionic strength
typically accelerates depletion. Ozone solution stabilization can
be considered as either short-term (less than one minute) or
long-term (greater than one minute). Short-term aqueous ozone
stabilization can be practically achieved by lowering the pH,
decreasing the temperature, involving an inhibitor such as an OH
radical scavenger, or lowering the ionic strength of solution.
Buffer agents such as phosphates are not inert to ozone. Long term
ozone stabilization may be achieved by forming a clathrate with a
cyclic oligosaccharide.
[0039] Cyclic oligosaccharides may be torus shaped with a
hydrophobic interior and hydrophilic exterior. The interior of the
torus may be relatively nonpolar compared to water. In the case of
cyclodextrin, the interior cavity dimension increases with alpha,
beta, and gamma cyclodextrin and derivatives thereof. Clathrates of
cyclic oligosaccharides are not static species. Substrates included
in the cavity rapidly exchange with free substrate molecules in
solution. The association of the host and guest molecules and the
disassociation of the formed clathrate is governed by a
thermodynamic equilibrium:
Cyclic Oligosaccharide+Substrate====Cyclic
Oligosaccharide*Substrate
[0040] Dissociation Constant for 1:1 molar ratio cyclic
oligosaccharide to guest substrate is:
K.sub.D 1:1=[Cyclic Oligosaccharide*Substrate]/[Cyclic
Oligosaccharide][Substrate]
[0041] This is the most common case; however, 2:1, 1:2, 2:2 or even
more complicated associations may exist simultaneously. With
increasing temperature the solubility of cyclic oligosaccharides
typically increases, but the complex stability may decrease.
[0042] In many embodiments, the cyclic oligosaccharide is water
soluble and may be, for instance, soluble in an aqueous solution
(at neutral pH and a temperature of 25.degree. C.) at a
concentration of greater than 10 mM, greater than 20 mM, greater
than 50 mM, greater than 100 mM or greater than 500 mM. Preferred
oligosaccharides may have molecular weights in the range of, for
example, 500 to 5000, 500 to 2000, 500 to 1500, 700 to 1400, 800 to
1200 or 900 to 1100. The cyclic oligosaccharides may comprise an
appropriate number of saccharide units including, for example, 4,
5, 6, 7, 8, 9, 10, 11 and/or 12 saccharide units. The
oligosaccharide may be naturally occurring or may be synthetic.
Preferred cyclic oligosaccharides may include cyclic
oligoglucosides such as cylcodextrins (CD). Cyclodextrins include,
for example, .alpha.-cyclodextrin, .beta.-cyclodextrin and
.gamma.-cyclodextrin as well as derivatives thereof. Derivatives of
.beta.-cyclodextrin includes, for example, those derivatives
structured to improve aqueous solubility, such as hydroxypropyl
.beta.-cyclodextrin.
[0043] In some embodiments, cyclic oligosaccharides may form
clathrates with ozone at molar ratios in the range of 5:1, 2:1,
1:1, 1:2, 1:3, 1:4, or greater. A single aqueous solution may
include different clathrates that exhibit different molar ratios of
cyclic oligosaccharides and ozone. In some embodiments the
clathrate solution may also contain unassociated ozone and/or
unassociated cyclic oligosaccharide. To activate the ozone to
participate in chemical oxidation, the ozone can be released from
the clathrate. In one set of embodiments the release can be
facilitated by, for example, altering pressure, altering
temperature and/or reducing the pH of the solution. For instance
the pH of the solution may be reduced by half a pH unit, from 7.0
to 6.5, to provide for the release of ozone from the clathrate.
This pH reduction may be accomplished in one embodiment by the in
situ decomposition of persulfate. As pH drops, the activity of
ozone increases. This increase in activity results in a reduction
in the amount of free ozone available and the drop in ozone
concentration pulls free ozone from the clathrate due to the
equilibrium relationship between the ozone clathrate and free ozone
in solution.
[0044] Ozone clathrates may be formed in situ or ex situ. Clathrate
solutions may be injected directly into the saturated zone,
unsaturated zone and/or smear zone or, in other embodiments, the
ozone and cyclic oligosaccharide may form a clathrate after
entering the saturated zone, unsaturated zone and/or smear zone.
For instance, the cyclic oligosaccharide may be introduced into the
saturated zone sequentially with the ozone. The two components can
subsequently associate in situ to form the clathrate. In some
embodiments it may be preferred to prepare the clathrate solution
prior to injecting the components into the ground. This may help
reduce the premature and wasteful decomposition of ozone and may
reduce side reactions such as oxidation of naturally occurring
materials in the soil and/or groundwater. Cyclic oligosaccharides
have limited reactivity with soil and thus should not interfere
with desired reaction paths. They also do not react with ozone and
do not scavenge hydroxyl radicals, leaving them available for
organic contaminant destruction. Cyclodextrin can be biodegradable
in soil. Cyclodextrin does not interact or adsorb to soil as
surfactants do, which, in the case of surfactants, may contribute
to the organic carbon load in the soil.
[0045] The ozone clathrates may be used in conjunction with other
oxidation systems to destroy organic contaminants. Additional
useful oxidants may include, for example, any combination of
peroxide, persulfate, permanganate, percarbonate and unassociated
(non-clathrate) ozone. These additional oxidants may be provided
simultaneously with the ozone clathrate and may be introduced via a
common aqueous solution or through separate means, such as separate
injectors. Additional oxidants may also be provided to the
contaminated material prior to or after delivery of the ozone
clathrate. For instance, a groundwater site can first be treated
with an ozone clathrate, then with unassociated ozone and finally
with a combination of persulfate and hydrogen peroxide.
Unassociated clathrate host (e.g., cyclodextrin) may also be
provided to the contaminated material to facilitate desorption of
contaminants.
[0046] A remediation system featuring a clathrate may be operated
at or close to ambient temperature which can help reduce the
volatilization of contaminants. For example, either in situ or ex
situ, the clathrate solution can be maintained at a temperature of
less than 60.degree. C., less than 50.degree. C., less than
40.degree. C. or less than 30.degree. C.
[0047] In general, soil treatment for hydrophobic organic
contaminants benefits from a two step mechanism involving both
desorption from the solid phase to the aqueous phase followed by
flushing and/or either chemical or biological oxidation. To enhance
flushing, surfactants can be circulated in an aqueous solution so
as to desorb hydrophobic organic contaminants from soil into the
aqueous phase. Surfactants function by reducing the interfacial
tension at the solid-liquid interphase to desorb organic
contaminants from soil. When surfactants and chemical or biological
oxidation is used, there are two primary mechanisms that typically
occur: 1) adsorbed soil contaminants are first desorbed and then
oxidized in the aqueous phase, or 2) sorbed contaminants are
directly oxidized while sorbed to the soil and also oxidized in the
aqueous phase. For strongly sorbed hydrophobic organic
contaminants, the desorption step may be the rate-limiting step in
the destruction of the contaminant.
[0048] An ozone clathrate may stabilize ozone and may also provide
a vehicle for desorbing organic contaminants from a solid phase
such as soil or sediment. Clathrates are not surfactants or
co-solvents but can exhibit a similar ability to desorb organic
compounds from the soil or sediment. When compared to surfactants
or co-solvents, clathrates may exhibit properties that make them
preferable to surfactants. For example, many clathrates are less
likely to form emulsions, can enhance bioremediation by
solubilizing the contaminant, can simultaneously desorb organics,
are typically biodegradable and are less likely to mobilize LNAPL
or DNAPL, which can make remediation much more difficult. Unlike
surfactants, clathrates may have little or no effect on interfacial
tension while still being useful to remediate NAPL via
microencapsulation. As shown below in Experiment 2, in at least
some cases, clathrates do not add to oxidant demand. In addition,
clathrates typically do not result in soil sorption or pore
exclusion as surfactants have been found to do. Furthermore,
clathrates do not seem to be adversely affected by changes in pH or
ionic strength.
[0049] In one set of embodiments an ozone clathrate may be used to
control the rate of oxidation. This rate can be adjusted in
response to a change in the rate of desorption from the material
containing the contaminants of interest. For instance, if the rate
of contaminant desorption is low, the rate of ozone release from
the clathrate can be reduced so the ozone is kept in reserve until
oxidizable contaminants become stearically available. This can be
accomplished, for example, by increasing the pH of the solution and
can reduce the amount of ozone that would otherwise be scavenged by
various reducing agents that are not the target contaminant. If the
rate of desorption is high, the rate of release of ozone from the
clathrate can be increased, by lower pH for example, to maximize
the rate of reaction with the contaminant. Thus, the system can be
tuned to maximize the rate of destruction while minimizing the
amount of ozone required to do so when compared to requirements for
treatment with unassociated ozone. These rates may also be
controlled by, for example, changing the clathrate host, altering
the concentration of clathrate provided, altering the
ozone:oligosaccharide ratio, altering flow rates of the clathrate
solution, altering the ratio of clathrate:oxidizer, and/or changing
the temperature of the system. In some cases, a combination of
different ozone clathrates may be used.
[0050] In some embodiments, activators can be added to improve the
rate of reaction of the remediation process. An activator is a
chemical or condition (e.g., temperature) that can be added or
altered to improve the rate of destruction. Activators can include
catalysts and changes to the environment, such as the application
of heat. Appropriate activators for oxidation systems may be, for
example, heat, an increase in pH, a transition metal such as
ferrous, ferric, or zero valent iron, hydrogen peroxide, and/or a
hydroxyl radical. Zero valent iron may also be used alone without
an oxidant to dehalogenate certain halogenated compounds such as
chlorinated organic compounds.
[0051] Other reagents may be used in conjunction with the
clathrate. For instance, complexing agents such as sodium citrate,
EDTA, sodium oxalate and tetrasodium pyrophosphate can be added to
further enhance desorption and oxidation of PAH and other
compounds. This may be particularly useful when heavy metals are
present in the matrix. Other compounds such as surfactants and
co-solvents may be used to aid in the desorption of contaminants
from various matrices. These compounds may be biodegradable
surfactants or biodegradable co-solvents. These include, for
example, citrus terpenes such as d-limonene.
[0052] The type of oligosaccharide that is chosen may also be
useful in controlling reaction rates. For instance, certain
structures and functional groups may retain ozone more securely
than others. The ability of a specific oligosaccharide to host
ozone can be determined by one of skill in the art by repeating
experiment 1 (described below) with the specific oligosaccharide
being evaluated.
[0053] In another set of embodiments, the density and/or viscosity
of clathrate solution may be controlled to improve contact with the
contaminant(s). The viscosity of the clathrate solution can be
preselected in order to achieve enhanced contaminant
contact/reaction efficiencies. For instance, higher viscosity
solutions may be chosen when high porosity soils are encountered.
Likewise, low viscosities may be preferred when soil porosities are
low. Viscosities may be adjusted by, for example, adjusting the
clathrate concentration or the ratio of clathrate to unassociated
cyclodextrin (or other oligosaccharide). For those target
contaminants that have a density greater than water (DNAPL), the
solution can be formulated to have a density greater (e.g., >1.0
g/cm.sup.3) than water so as to deliver the most clathrate--oxidant
directly to the contaminant. The clathrate solution may have a
lower density (e.g., <1.0 g/cm.sup.3) for those target
contaminants that have a density less than water (LNAPL). A lower
density may be achieved by, for example, adding an acceptable
co-solvent that renders the density of the solution less than 1.0
g/cm.sup.3. Alternatively, a gas may be introduced to the solution
to increase buoyancy which can improve contact with LNAPL. One
method of controlling the density of the clathrate solution is to
increase or decrease the concentration of the clathrate to increase
or decrease the density of the solution.
[0054] In another embodiment, the clathrate may be used to generate
a superoxide radical (anion) such as O.sub.2r. Superoxide radicals
may be useful in oxidizing many organic contaminants. Examples of
how a superoxide radical can be formed are provided below. The
concentration of superoxide radicals can be increased by using the
ozone clathrate to provide a continuously high level of ozone to
the solution. OHr=hydroxyl radical, HO.sub.2r=perhydroxyl radical,
O.sub.2r=superoxide radical.
O.sub.3+H.sup.+.fwdarw.OHr+O.sub.2(water reaction) 1)
O.sub.3+OH.sup.-.fwdarw.HO.sub.2r+O.sub.2(water reaction) 2)
O.sub.3+H.sub.2O.sub.2.fwdarw.HO.sub.2r+OHr+O.sub.2(hydrogen
peroxide reaction) 3)
O.sub.3+OHr.fwdarw.HO.sub.2r+O.sub.2(chain reactions from all of
the above (1,2,3)) 4)
O.sub.3+HO.sub.2r.fwdarw.O.sub.2r+OHr+O.sub.2(chain reactions from
all of the above (1,2,3)) 5)
In addition,
H.sub.2O.sub.2+OHr.fwdarw.H.sub.2O+O.sub.2r(reaction between
hydrogen peroxide and hydroxyl radical) 6)
H.sub.2O.sub.2+SO.sub.4r.fwdarw.SO.sub.4.sup.2-+HO.sub.2r+H.sup.+(reacti-
on between hydrogen peroxide and sulfate radical) 7)
and;
HO.sub.2r.revreaction.O.sub.2r+H.sup.+(superoxide radical is
deprotonated form of perhydroxyl radical and is dependent on the pH
of the solution) 8)
[0055] Ozone clathrates may be useful in the destruction of a
number of contaminants, both organic and inorganic. These
contaminants can include, for example, solvents, heavy metals,
pesticides, herbicides, fungicides, preservatives, wood
preservatives, munitions, explosives, chemical warfare agents,
fuels, oils, greases, pharmacologicals, endocrine disruptors (EDC)
and viral and/or microbial agents. Classes of organic compounds
that can be treated include both dense and light non-aqueous phase
liquids (NAPL), dissolved or sorbed organic compounds, volatile
organics, semi-volatile organics, chlorinated volatile organics,
non-volatile organics, halogenated organics and heavy metals.
Specific compounds that can be remediated include, for example,
polychlorinated biphenyls (PCBs); tetrachloroethylene (PCE),
trichloroethylene (TCE), trichloroethane (TCA), dichloroethene
(DCE), chlorophenols, vinyl chloride; fuel constituents such as
benzene, ethylbenzene, toluene, xylene, methyl tert butyl ether
(MTBE), tertiary butyl alcohol (TBA), polynuclear aromatic
hydrocarbons (PAHs), dioxins, furans, ethylene dibromide (EDB);
DDT, silvex and geosimin. Inorganic contaminants may include
metals, such as lead, arsenic, chromium, mercury, silver, cadmium,
nickel and/or cobalt. The use of an ozone clathrate can reduce
target contaminant concentrations by more than 50%, more than 75%,
more than 90%, more than 95%, more than 98% or more than 99%, by
weight. In different embodiments, absolute levels of contaminants
can be reduced to less than 1%, less than 1,000 ppm, less than 100
ppm, less than 10 ppm, less than 1 ppm, less than 100 ppb or less
than 10 ppb, by weight.
[0056] The method described in US Patent Publication No.
US2008/0008535A1 to Ball, and which is hereby incorporated by
reference herein, can be used to apply a clathrate solution to a
remediation site. The technology described herein may also be
useful when applied to other remediation methods. Examples of other
methods include gravity feed, caissons, trenches, injection and/or
extraction wells, recirculation wells (vertical or horizontal),
push-pull injection/extraction or reactive walls. Examples of in
situ sediment remediation methods include harrows, in situ
ozonators and reactive caps. Examples of ex situ methods for soil,
water, or sediment include many types of batch, semi-batch, plug
flow, slurry-phase reactors, or pressure-assisted reactors.
[0057] The ozone clathrate may be provided over a broad range of
concentrations. Many clathrate forming compounds, such as cyclic
oligosaccharides, are highly soluble in aqueous solutions. For
instance, cyclodextrin can be provided at concentrations of greater
than 0.1 mg/L, greater than 1 mg/L, greater than 10 mg/L, greater
than 100 mg/L, greater than 1000 mg/L, greater than 5 g/L, greater
than 10 g/L, greater than 100 g/L, or greater than 200 g/L.
Clathrate concentrations may be similar. A saturated ozone solution
used in the field is typically at a concentration of about 10 mg/L.
By microencapsulating ozone in a clathrate, the ozone concentration
can be significantly increased, to greater than 20 mg/L, greater
than 50 mg/L, or greater than 100 mg/L, or greater than 500 mg/L.
In addition, the oligosaccharide portion of the clathrate can be
re-charged with ozone after the ozone has been released from the
clathrate into solution. This re-charging may take place above
ground or in situ.
[0058] A clathrate solution may be used ex situ or in situ and may
be provided at a rate appropriate for controlled destruction of the
target contaminants. Injection rates may also be controlled in
response to depth, soil conditions, permeability, number of
injectors and previous treatment. In some embodiments, the
clathrate solution can be provided (e.g., injected) at a rate of 1
L/min, 5 L/min, 10 L/min, 50 L/min, 100 L/min or more.
[0059] The following provides an example of how a clathrate
solution may be used with the system provided in U.S. Patent
Publication No. US2008/0008535A1. Initially, a super-saturated
ozone in water solution is mixed with a cyclic oligosaccharide
using, for instance, an in-line static mixer, a venturi, a porous
metal sieve/diffuser or a pressure vessel or combinations thereof
and injected into the subsurface at a specified flow rate and for a
specified time selected based on the conditions at the site.
Hydrogen peroxide (which may be buffered) and buffered persulfate
may be either simultaneously or sequentially injected into the
subsurface. The same or different injection wells may be used for
the different components. The chemical oxidation process may be
monitored by taking measurements of, for example, pH, ORP,
conductivity, temperature, dissolved oxygen, dissolved ozone,
hydrogen peroxide, persulfate, sulfate and phosphate. If monitoring
indicates that contaminants remain after several weeks, the
procedure may be repeated using the same or different injection
wells.
[0060] In another embodiment a solution of ozone and a solution of
a cyclic oligosaccharide may be introduced independently to the
saturated zone, unsaturated zone or smear zone. For instance, a
cyclodextrin solution may be injected into the ground
simultaneously or sequentially (before or after) with a solution or
supersaturated solution of ozone. Upon mixing, the clathrate may be
formed in situ.
[0061] In another embodiment, a clathrate solution may be produced
by adding solid cyclic oligosaccharide to an ozone solution. For
instance, powdered hydroxypropyl beta cyclodextrin may be added to
a supersaturated ozone solution at atmospheric pressure. In this
manner, foaming that might occur by bubbling ozone through a cyclic
oligosaccharide solution can be avoided while still achieving high
clathrate concentrations.
[0062] In another set of embodiments a cyclic oligosaccharide can
be used to remediate soil, sediment, surfaces, and water samples
with or without ozone. Cyclodextrin is exemplary of these cyclic
oligosaccharides and may be preferred, although other cyclic
oligosaccharides can be equally useful.
[0063] It has been found that cyclic oligosaccharides such as
cyclodextrin can perform a variety of functions in a remediation
project. Cyclic oligosaccharides can act as a carrier for oxidants
and/or activators. They can solubilize a wide range of organic
contaminants such as flame retardants including polybrominated
diphenyl ethers (PBDE), perfluoroalkyl compounds; hydrocarbon based
fuels (gasoline, diesel, #2, #4 and #6 fuel oils, jet fuel,
kerosene), halogenated organics, MTBE, ethylene dibromide,
pesticides, herbicides, PCBs, dioxins, furans, endocrine
disruptors, and polycyclic hydrocarbons as well as non-aqueous
phase liquids (NAPLs) either dense (DNAPL) or light (LNAPL). Cyclic
oligosaccharides can also serve as an energy source for
bioremediation and can promote biological activity as a
co-metabolite that can further remediate contaminated soil or
water. Thus, in a single process, cyclic oligosaccharide can
deliver an oxidant or activator, solubilize an organic contaminant
and promote biological remediation. These different functions can
be controlled by regulating the ratios of cyclic oligosaccharide,
oxidant and contaminants. Contaminant concentration at a site can
be estimated using methods known to those of skill in the art.
Oxidant concentrations can be determined by knowing the efficiency
of the oxidation system for a target contaminant. The amount of
cyclic oligosaccharide can be determined once the practitioner
decides what oxidants and/or activators are to be delivered to a
site and the amount of residual cyclic oligosaccharide that is
desired. Ratios of cyclic oligosaccharide to oxidant to contaminant
(on a molar basis) may preferably range from 1000:1000:1 to 1:1:1
to 1:1000:1000. In some cases, the amount of oxidant can be
increased to achieve greater levels of destruction. For instance,
the amount of oxidant to contaminant may be 2:1, 5:1 or 10:1.
Oxidant type and concentrations may also be chosen to provide an
environment that promotes microbial activity. Materials such as
phosphates may also be included and can provide a nutrient source
for microbes as well as a pH buffer. pH may be controlled between 5
and 10 or 6 and 9 to promote microbial activity. Other nutrients
such as nitrogen and trace minerals can be added to promote
biodegradation. Examples of a nitrogen source include ammonium
persulfate and nitrous oxide gas.
[0064] Specific cyclic oligosaccharides can be chosen to form a
clathrate with a specific guest molecule. For example, a chosen
cyclic oligosaccharide may include a large cavity for forming a
clathrate with a large activator, oxidant or contaminant. Preferred
oligosaccharides can be found and selected using the following
technique. First, a solution of candidate cyclic oligosaccharide
compound(s) is formed and a stoichiometric amount of the target
activator, oxidant or contaminant compound is added. The solution
is mixed well and the pH is controlled to promote clathrate
formation. Effective formation of a clathrate can be determined
using spectrometric techniques or by nuclear magnetic resonance
(NMR) to determine how much free compound is unassociated with the
oligosaccharide.
[0065] An oligosaccharide such as cyclodextrin can be delivered to
the site of contamination by injecting an aqueous solution of the
compound through a bore hole into the saturated, unsaturated or
smear zone. It may be mixed with an oxidant stream such as ozone,
persulfate or peroxide, percarbonate, permanganate, perphosphates
or may be delivered independently. The oligosaccharide may be
delivered before or after administration of the oxidant(s). A gas
may be used to aid in dispersing the oligosaccharide and can help
to mix the oligosaccharide with the groundwater media. The gas may
be introduced with, or separately from, the oligosaccharide.
Appropriate gases include air, oxygen, ozone, nitrogen, and nitrous
oxide. The oligosaccharide may be delivered at a variety of pHs,
including 3.0 to 11.0, 5.0 to 9.0 and 6.0 to 8.0. The solution may
be buffered, for example, by a phosphate solution such as sodium
phosphate. Phosphate can also aid in precipitating metals in situ
and may be added in quantities greater than that necessary for
proper pH control. Phosphates can also be used to promote microbial
activity for biodegradation.
[0066] Cyclic oligosaccharides may be used in conjunction with one
or more chemical oxidants that can be used in soil, sediment,
surfaces, water and groundwater remediation. For instance, cyclic
oligosaccharides may be used with peroxide, persulfate,
permanganate, percarbonate, ozone, perphosphates or any combination
thereof. In different cases, cyclic oligosaccharides may or may not
form a clathrate with the oxidant. For example, ozone may form a
clathrate while permanganate does not. Cyclic oligosaccharides may
also be used in combination with activators such as organic or
inorganic activators. Activators are materials that are not
oxidizers themselves but instead promote the oxidation of organic
contaminants with other oxidizers such as peroxide, persulfate,
permanganate, percarbonate and ozone. Inorganic activators include
iron (ferrous, ferricor, and zero valent) and in general, divalent
or trivalent transition metals. Ozone can also act as an activator.
A clathrate can also be formed using native iron that is present in
situ. Activators may be released from the clathrate by, for
example, adjusting the pH of the solution. For instance, iron can
be released from a cyclic oligosaccharide clathrate by lowering the
pH of the solution below pH 5.0 or raising the pH above pH 9.0.
[0067] A cyclic oligosaccharide can be used to deliver an oxidant
or activator in an aqueous carrier either in situ or ex situ. An
activator or oxidant can be added to an aqueous solution of a
cyclic oligosaccharide and the activator or oxidant may form a
clathrate with the oxidant or activator. This may, for example,
improve solubility and stability of the oxidant or activator. For
instance, an inorganic activator such as iron can form a clathrate
with a cyclic oligosaccharide and can then be delivered to the
saturated, unsaturated or smear zones. The clathrate may then
release the activator or oxidant resulting in free activator or
oxidant and either free cyclic oligosaccharide or a decomposition
product thereof. The cyclic oligosaccharide may allow the activator
or oxidant to be carried further into the hydrophobic region of the
site than would be possible in the absence of the cyclic
oligosaccharide.
[0068] Cyclic oligosaccharides such as cyclodextrin can solubilize
organic contaminants that may be present on a surface or in the
water, soil, sediment or groundwater. The organic contaminants may
be adsorbed on, or retained by, sand, rock, clay and/or organic
material that is present at the contaminated site. Cyclic
oligosaccharides typically act unlike surfactants in that the
cyclic oligosaccharides do not form micelles and do not have a
polar head and hydrophobic tail. Cyclic oligosaccharides such as
cyclodextrin have a hydrophobic inner cavity and a hydrophilic
exterior wall. Therefore, while it has been found that cyclic
oligosaccharides can help solubilize organic contaminants in situ
and ex situ, this is typically done in the absence of micelle
formation. Nonetheless, cyclic oligosaccharides have been found to
be effective at associating with organic contaminants and releasing
them from soil, sediment, DNAPL and LNAPL phases into the aqueous
phase where they can be destroyed by oxidants in aqueous solution.
Cyclic oligosaccharides can act as carriers for oxidants and
activators while surfactants are typically not capable of this and
are limited to aiding in the solubilization of contaminants.
[0069] Surfactants may be biodegradable or may be stable over the
long term. They may also be destroyed by the oxidants being used or
may be stable in the presence of these oxidants. In one set of
embodiments, a cyclic oligosaccharide can be used in conjunction
with an anionic surfactant based on sulfate, sulfonate, or
carboxylate anions. These include surfactants such as sodium
dodecyl sulfate (SDS); or nonionic surfactant based on alkyl
polyethylene oxide and its copolymers, alkyl polyglucosides, fatty
alcohols, cocamide MEA, and such as the polysorbates, Tween 20 or
Tween 80; or anionic/nonionic mixtures such as Simple Green.RTM.
manufactured by Sunshine Makers, Inc. Other surfactants that can be
used include: Alfoterra.RTM., brand of branched alcohol propoxylate
sulfate, sodium salt anionic surfactants manufactured by Sasol
North America; Citrus Burst #1, #2, and #3 and EZMulse.RTM. brand
of citrus based surfactants manufactured by Florida Chemical
Company. The cyclic oligosaccharide and the surfactant may act in a
complementary manner by solubilizing different compounds or by
solubilizing the same compound at different rates. When compared to
surfactants, the cyclic oligosaccharide may also be more effective
at desorbing organic contaminants from specific materials.
Vegetable oils, fatty acids, fatty acid methyl esters, from sources
such as soy oil, sunflower oil, or canola oil can also be used as a
co-solvent in conjunction with cyclic oligosaccharides and
surfactants to aid in desorption. Citrus derived oils such as
d-limonene can also be used as a co-solvent. Chelating agents such
as citric acid, acetic acid, EDTA, phosphonates can be added to
assist in transporting activators or to bind natural metals. The
addition of heat or hot water can also be used to improve the
desorption and biodegradation aspects of the process.
[0070] Remediation of contaminated materials through the use of
chemical oxidation can be followed by bioremediation.
Bioremediation may commence spontaneously after chemical oxidation
procedures but often may need to be primed by inoculating with
bacteria and/or nutrients. Cyclodextrin and other cyclic
oligosaccharides can serve as a energy source for co-metabolism by
bacteria but the compounds are typically stable and require
significant time in situ before bacteria are able to digest and
utilize the polysaccharides. However, by partially oxidizing the
oligosaccharide with a chemical oxidant such as persulfate or
peroxide, for example, the structure of the oligosaccharide is
partially decomposed and the resulting fragments of the
oligosaccharide can provide an immediate energy source to any
bacteria that may be present. These fragments may include, for
example, mono, di and trisaccharides. The site may also be
inoculated with bacteria to accelerate biological activity. The
presence of cyclic oligosaccharide fragments can provide an
immediate boost to the biological activity that results in faster
and more complete bioremediation that can occur subsequent to or
during chemical oxidation processes. The biological activity may
have long lasting residual effects that provide for remediation
down to very low contaminant levels after completion of chemical
oxidation. Furthermore, the bioremediation can help to destroy
additional organic contaminants that may migrate to the site after
completion of the chemical remediation process.
[0071] In one example, a remediation process may proceed as
described below. A site may be contaminated with a variety of poly
aromatic hydrocarbons (PAH) present in the saturated and
unsaturated zones. The site may include a DNAPL layer. Several
wells are drilled at the site providing access to the saturated
zone. Aqueous solutions of oxidants such as peroxide, persulfate
and ozone may be injected into the saturated zone. Concurrently, a
solution of a cyclodextrin/iron clathrate is provided either
together with one of the oxidants or as a separate stream. A mixing
gas may also be injected such as through a sparger. After being
injected into the saturated zone, the iron leaves the clathrate and
serves as an activator to promote the oxidation of organic
materials present in the saturated zone. The cyclodextrin, now free
of the iron, migrates through portions of the saturated or smear
zones and solubilizes hydrocarbons that are adsorbed on the
surrounding soil, sediment, and rock. The solubilized hydrocarbons
are now associated with the cyclodextrin, drawn into the aqueous
phase, and are subjected to oxidation from the oxidant or
combination of oxidants that may be present. During the oxidation
process, the organic contaminant is mineralized and the
cyclodextrin is fragmented. These fragments can then metabolized by
native or inoculated bacteria which use the cyclodextrin fragments
as an energy source to increase the size and activity of the
bacterial colony. These bacteria may then proceed with metabolizing
any remaining organic contaminants or portions of organic
contaminants that are present. The bacteria may remain in situ for
months or years and can reduce the concentration of organic
contaminants that enter the area by transport from adjacent areas
or via desorption from existing materials.
[0072] In a single operation involving desorption, chemical
oxidation, and bio-oxidation, any dissolved organic contaminant,
organic contaminant/cyclodextrin complex and dissolved cyclodextrin
may be simultaneously destroyed using one or more oxidants. For
example, the concentration of the contaminant, the
contaminant/cyclodextrin complex and the free cyclodextrin may each
be reduced by more than 50%, more than 75% or more than 90% by
weight.
[0073] In another embodiment a cyclic oligosaccharide may be
selected to form a clathrate having properties that cause it to
reside in a particular portion of the soil or water column. For
instance, if the target contaminant is a dense compound the
combination of the cyclic oligosaccharide and activator or oxidant
are chosen to produce a clathrate denser than water so that the
clathrate will concentrate in the vicinity of the contaminant. This
can allow for maximization of contact of the contaminant with the
oxidant or activator while reducing the use of oxidant that never
comes into contact with the target contaminant. The cyclic
oligosaccharide can form a clathrate with an activator and both the
resulting clathrate and oxidant can be chosen to be of greater,
lesser or equal density to water. For instance, if the clathrate
density is greater than 1.0 it will tend to sink within the soil
and groundwater media. When treating DNAPL, for instance, this
denser clathrate will serve to concentrate active components, such
as oligosaccharide, oxidant and/or activator in the lower portion
of the saturated zone close to, or in contact with, the DNAPL. Very
little, if any, of these compounds will be wasted in areas above
the DNAPL that contain little or no contamination.
Experiment 1A
[0074] An experiment was conducted to determine how the stability
of an aqueous ozone solution compares to the stability of an
aqueous solution of a clathrate comprising ozone and
hydroxypropyl-.beta.-cyclodextrin. A first bubble column contained
DI water. A second column contained a 20 mM (26.2 g/L) solution of
hydroxypropyl-.beta.-cyclodextrin in DI water. Each column was
ozonated for approximately 10 minutes. After ozonation, each column
was analyzed for ozone (Analytical Technologies Inc. Model
#Q45H/64) and ORP (Orion Model #920A ion specific electrode).
Readings were taken each minute for the first 15 minutes and every
5 minutes thereafter until ozone concentrations were seen to level
off to background levels. Results are provided below in Table 1
(NA=Not Analyzed) and indicate the maintenance of a much higher
free ozone concentration in the clathrate solution (about 2 ppm)
than in the pure ozone solution (<1 ppm). For example, as seen
in FIG. 1, even after two hours the ozone concentration in the
clathrate solution (pH 6.8) was stable at about 2 ppm while the
ozone concentration in the pure ozone solution dropped below 2 ppm
in about 20 minutes and below about 1 ppm in an hour. The clathrate
provided for a more consistent level of ozone throughout the two
hour time window while the sample without the clathrate exhibited
very high initial concentrations that tailed off more quickly when
compared to the clathrate sample.
TABLE-US-00001 TABLE 1 O.sub.3 Concentration (mg/L) Time (min)
O.sub.3 O.sub.3 + CD 0 9 9 1 8.6 3 2 7 3.5 3 6.4 2.6 4 6 2.5 5 5
3.5 6 4.4 1.8 7 3.5 1.9 8 3.2 2.8 9 3 2.3 10 2.7 2.6 11 2.5 2.8 12
2.3 2.9 13 2.2 4.7 14 2.1 2.7 15 2 2.4 20 1.7 2.6 25 1.5 2.5 30 1.4
4.7 35 1.3 1.9 40 1.2 2.3 45 1 2.7 50 1 2.3 55 1 2 60 1 2.2 65 1
2.3 70 1 2.5 75 NA 2 80 NA 1.9 85 NA 2.3 90 NA 2.1 95 NA 2.1 100 NA
2.6 105 NA 2.5 110 NA 2.2 115 NA 2.4 120 NA 2.1 960 NA 2.1
Experiment 1B
[0075] Experiment 1B was performed to provide confirmation of the
experiment 1A results using a different analytical method for ozone
analysis based on titration. The experiment, methods, and findings
are discussed here.
[0076] The experiment illustrates that the presence of cyclodextrin
can affect and stabilize the dissolved ozone concentration in an
aqueous system. In one test, the apparent half life (by probe) of
ozone in a 0.5% cyclodextrin solution was reduced from around 13
minutes to about 1 minute. This means the formed ozone clathrate
sequesters the ozone and renders it undetectable by the probe. To
determine the dissolved ozone concentrations below the detection
limit of the probe (0.1 mg/l), the Indigo Colorimetric Method
(Standard Methods) was used. In this method, free ozone destroys
the blue indigo color. The grade of decoloration can be measured
spectro-photometrically to quantify the ozone concentration. The
change in color is instantaneous.
[0077] In another test, indigo solution was combined with a
cyclodextrin-stabilized ozone solution, the solution did not
decolorize instantaneously. It took 80 minutes for the solution to
decolorize completely. This indicates that over the course of 80
minutes the equivalent of 0.5 mg/l (the upper detection limit for
this method) dissolved ozone was released from the
cyclodextrin/ozone clathrate to the aqueous phase to react with the
indigo. FIG. 6 displays this phenomenon in a time-series of
pictures taken over 80 min. The initial picture was taken when the
dissolved ozone probe read 0.0 mg/l (ND). The samples in each
picture are, from left to right, a deionized water control, a CD
control, t=0 min, t=5 min, t=15 min, t=30, t=45 min, t=80 min,
t=100 min, t=130 min and t=220 min. The results show that even the
sample drawn 80 minutes after no dissolved ozone could be detected
by the probe contained at least 0.5 mg/l of cyclodextrin-complexed
ozone when tested using the Indigo Colorimetric Method. FIG. 5
shows these results analytically, i.e. based on the continuously
metered ORP values. The fact that the ORP was still greater than
1,000 mV after 15 min when the ozone probe failed to detect any
free ozone and greater than 600 mV after 100 minutes shows the
continued activity of ozone in solution.
[0078] These results mean that cyclodextrin may be used to prolong
the activity of aqueous ozone, thereby increasing the oxidant's
reaction time and effectiveness. This is especially beneficial for
in-situ applications when the goal is to deliver ozone deep into
the contaminated soil formation.
[0079] Experiment 1B verified the results of experiment 1A that the
cyclic oligosaccharide (HP-.beta.-CD) does form a clathrate and
that the clathrate slowly releases ozone into solution as
determined visually and spectrophotometrically.
Experiment 2
[0080] A second experiment was conducted to determine what negative
interaction may exist, if any, between oxidants and
hydroxypropyl-.beta.-cyclodextrin in the presence of
trichloroethylene (TCE) at a concentration exceeding the solubility
limit of TCE in water. Eight samples were developed to analyze
remedial efficiencies of the persulfate/ozone/hydrogen peroxide
system described in U.S. Patent Application Publication No.
2008/0008535A1. The experiment was run with and without the
presence of HP-.beta.-CD. The reactor composition was as
follows:
[0081] 1) TCE & Phosphate Buffer
[0082] 2) TCE, HP-.beta.-CD & Phosphate Buffer
[0083] 3) TCE, Ozone & Phosphate Buffer
[0084] 4) TCE, Ozone, HP-.beta.-CD & Phosphate Buffer
[0085] 5) TCE, OxyZone & Phosphate Buffer
[0086] 6) TCE, OxyZone, HP-.beta.-CD & Phosphate Buffer
[0087] 7) TCE, Oxygen & Phosphate Buffer
[0088] 8) TCE, Oxygen, HP-.beta.-CD & Phosphate Buffer
[0089] Reactors were 1000 ml HDPE bottles, and were secured on a
LABLINE Multi-Magnestir magnetic stirrer and were stirred for 26
hours at 20.degree. C. Samples were taken from the reactors using a
peristaltic pump and were stored in 43 ml VOAs. Samples were taken
at 0, 1.75, 6, and 26 hours. The concentrations of the compounds in
the reactors were as follows: [0090] Na.sub.2S.sub.2O.sub.8=65 g/L
[0091] H.sub.2O.sub.2=125 mg/L [0092] HP-.beta.-CD=5 g/L [0093]
TCE=2000 mg/L [0094] Buffer=3.44 g/L Monobasic Potassium Phosphate
[0095] 4.54 g/L Dibasic Potassium Phosphate
[0096] Reactors treated with gas received 50 mL/min of either pure
oxygen gas or 6% ozone gas by weight. This is equivalent to
approximately 3.2 mg/min of ozone in the reactors treated with
ozone (Reactors 3-6).
[0097] Results are provided below in Table 2 (and graphically in
FIGS. 2 and 3) and indicate that persulfate/ozone/hydrogen peroxide
and HP-.beta.-CD do not interact in a negative manner. The presence
of HP-.beta.-CD decreased the oxidation rate, as the TCE
concentration for persulfate/ozone/hydrogen peroxide alone at 6
hours was 283 ppb, while for persulfate/ozone/hydrogen peroxide
with HP-.beta.-CD the TCE concentration at 6 hours was 96.9 ppm.
However, the TCE concentration at 26 hours without HP-.beta.-CD
with HP-.beta.-CD were 73.5 ppb and 75.5 ppb, respectively. If
HP-.beta.-CD was generating oxidant demand, the HP-.beta.-CD sample
would not reach the same TCE destruction levels as the sample
without the HP-.beta.-CD.
[0098] The results also demonstrate a significant reduction in the
oxidation rate and efficiency of ozone alone when HP-.beta.-CD is
in solution, potentially by the HP-.beta.-CD inhibiting contact
between ozone and TCE trapped within the HP-.beta.-CD cavity.
Additionally, the results show that the presence of HP-.beta.-CD
inhibits TCE volatilization. This is demonstrated by the retention
of TCE in the control sample containing HP-.beta.-CD (sample 2)
relative to the control sample without HP-.beta.-CD (sample 1).
This second point is further evidence for uptake of TCE into the
HP-.beta.-CD cavity. Therefore, the cyclic oligosaccharide
(HP-.beta.-CD) stabilized the ozone in solution, decreased the
contaminant losses due to volatilization and did not adversely
affect the oxidation capacity of the system which included ozone,
persulfate and hydrogen peroxide.
TABLE-US-00002 TABLE 2 TCE Concentration (mg/L) Time (hrs) Sample
1.75 6 26 TCE 1030 644 256 TCE + CD 984 837 685 TCE + O.sub.3 444
96 0.162 TCE + O.sub.3 + CD 106 5.86 5.83 TCE + S.sub.2O.sub.8 +
H.sub.2O.sub.2 + O.sub.3 220 0.283 0.0735 TCE + S.sub.2O.sub.8 +
H.sub.2O.sub.2 + O.sub.3 + CD 316 96.9 0.0755 TCE + O.sub.2 555 386
137 TCE + O.sub.2 + CD 321 226 168
Experiment 3
[0099] Another experiment was conducted to evaluate the effect of
an ozone clathrate on the potential for enhanced desorption and
degradation of strongly sorbed organic contaminants such as
polycycylic aromatic hydrocarbons (PAHs). Pyrene was used as the
target compound to be representative of PAHs sorbed onto soil in a
soil and groundwater matrix. Pyrene was solubilized in methanol and
the solution was mixed with the sand thoroughly. The methanol was
subsequently evaporated under a fume hood leaving the pyrene
adsorbed onto the sand. The sand/pyrene material was allowed to sit
for three days prior to analysis for pyrene concentration and its
use in the experiments. Eight samples were developed to analyze
remedial efficiencies of sodium persulfate, hydrogen peroxide, and
ozone with and without the presence of HP-.beta.-CD. The reactor
composition was as follows:
[0100] 9) Pyrene Sand & Deionized Water
[0101] 10) Pyrene Sand, Oxygen & Deionized Water
[0102] 11) Pyrene Sand, Ozone & Deionized Water
[0103] 12) Pyrene Sand, HP-.beta.-CD & Deionized Water
[0104] 13) Pyrene Sand, Oxygen, HP-.beta.-CD & Deionized
Water
[0105] 14) Pyrene Sand, Ozone HP-.beta.-CD & Deionized
Water
[0106] Semi-batch reactors were 1200 ml borosilicate glass columns
for 24 hours at 20.degree. C. fitted with inlet and outlet for
ozone or oxygen gas and off-gas. One pore volume (600 mL) of
deionized water was added to each column. After the reaction
period, sand samples were taken from the center of the columns and
stored in 8 oz amber glass jars. The initial concentrations of the
compounds in the reactors were as follows: [0107] HP-.beta.-CD=5
g/L [0108] Pyrene=500 mg/kg
[0109] Reactors treated with gas received 50 mL/min of either pure
oxygen gas or 6% ozone gas in oxygen gas by weight. This is
equivalent to approximately 3.2 mg/min of ozone in the reactors
treated with ozone (Reactors 2-3, 5-6).
[0110] Sand samples were analyzed by GC/MS using EPA Method 8270
for PAHs. Results are provided below in Table 3 (and in FIG. 4) and
indicate that the Ozone/HP-.beta.-CD clathrate provides the
greatest reduction in pyrene concentration in soil, from an initial
concentration of approximately 500 ppm to 101 ppm. The presence of
HP-.beta.-CD alone decreased the concentration of pyrene in sand to
238 ppm, indicating a significant desorption effect relative to
deionized water alone, which resulted in a pyrene concentration of
490 ppm.
TABLE-US-00003 TABLE 3 Pyrene Concentration Sample (mg/kg) Pyrene
490 Pyrene + CD 238 Pyrene + O.sub.2 335 Pyrene + O.sub.2 + CD 231
Pyrene + O.sub.3 180 Pyrene + O.sub.3 + CD 101
[0111] It is to be understood that this disclosure is not limited
in its application to the details of construction and the
arrangement of components set forth in the following description or
illustrated in the drawings. The embodiments herein are capable of
other embodiments and of being practiced or of being carried out in
various ways. Also, it is to be understood that the phraseology and
terminology used herein is for the purpose of description and
should not be regarded as limiting. The use of "including,"
"comprising," or "having" and variations thereof herein is meant to
encompass the items listed thereafter and equivalents thereof as
well as additional items. Unless limited otherwise, the terms
"connected," "coupled," and "mounted," and variations thereof
herein are used broadly and encompass direct and indirect
connections, couplings, and mountings. In addition, the terms
"connected" and "coupled" and variations thereof are not restricted
to physical or mechanical connections or couplings.
[0112] The foregoing description of several methods and embodiments
has been presented for purposes of illustration. It is not intended
to be exhaustive or to limit the claims to the precise steps and/or
forms disclosed, and obviously many modifications and variations
are possible in light of the above teaching. It is intended that
the scope of the invention be defined by the claims appended
hereto.
* * * * *