U.S. patent application number 11/071224 was filed with the patent office on 2005-09-08 for methods for making chlorous acid and chlorine dioxide.
Invention is credited to Sampson, Allison H., Sampson, Richard L..
Application Number | 20050196337 11/071224 |
Document ID | / |
Family ID | 25442863 |
Filed Date | 2005-09-08 |
United States Patent
Application |
20050196337 |
Kind Code |
A1 |
Sampson, Allison H. ; et
al. |
September 8, 2005 |
Methods for making chlorous acid and chlorine dioxide
Abstract
Chlorous acid is generated from a chlorite salt precursor, a
chlorate salt precursor, or a combination of both by ion exchange.
The ion exchange material facilitates the generation of chlorous
acid by simultaneously removing unwanted cations from solution and
adding hydrogen ion to solution. Chlorine dioxide is generated in a
controlled manner from chlorous acid by catalysis. Chlorine dioxide
can be generated either subsequent to the generation of chlorous
acid or simultaneously with the generation of chlorous acid. For
catalysis of chlorous acid to chlorine dioxide, the chlorous acid
may be generated by ion exchange or in a conventional manner. Ion
exchange materials are also used to purify the chlorous acid and
chlorine dioxide solutions, without causing degradation of said
solutions, to exchange undesirable ions in the chlorous acid and
chlorine dioxide solutions with desirable ions, such as stabilizing
ions, and to adjust the pH of chlorous acid and chlorine dioxide
solutions.
Inventors: |
Sampson, Allison H.;
(Easton, CT) ; Sampson, Richard L.; (Easton,
CT) |
Correspondence
Address: |
JACOBSON HOLMAN PLLC
400 SEVENTH STREET N.W.
SUITE 600
WASHINGTON
DC
20004
US
|
Family ID: |
25442863 |
Appl. No.: |
11/071224 |
Filed: |
March 4, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11071224 |
Mar 4, 2005 |
|
|
|
09919918 |
Aug 2, 2001 |
|
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Current U.S.
Class: |
423/477 |
Current CPC
Class: |
C01B 11/024 20130101;
C01B 11/023 20130101; C01B 11/022 20130101; B01J 39/04 20130101;
B01J 41/02 20130101; B01J 39/02 20130101; C01B 11/08 20130101; C01B
11/028 20130101; B01J 41/04 20130101; B01J 31/08 20130101 |
Class at
Publication: |
423/477 |
International
Class: |
C01B 011/02 |
Claims
1. A process for producing halogen oxide, the process comprising:
feeding a dilute aqueous alkali metal halite solution into a cation
exchange column, wherein the cation exchange column contains a
cation exchange material; contacting the dilute aqueous alkali
metal halite solution with the cation exchange material to produce
an effluent containing halous acid; and feeding the effluent halous
acid into contact with a catalytic material in a moist environment
for a time sufficient to produce a halogen oxide.
2. (canceled)
3. (canceled)
4. (canceled)
5. (canceled)
6. (canceled)
7. (canceled)
8. (canceled)
9. (canceled)
10. (canceled)
11. (canceled)
12. (canceled)
13. A process for generating chlorous acid and chlorine dioxide
which comprises contacting a chlorite salt precursor and an acid
with a catalytic material in a moist environment for a time
sufficient to form chlorous acid and chlorine dioxide together.
14. The process as described in claim 13 wherein said catalytic
material is on said cation exchange material.
15. The process as described in claim 13 wherein said catalytic
material is an ion exchange material.
16. (canceled)
17. (canceled)
18. (canceled)
19. (canceled)
20. (canceled)
21. (canceled)
22. (canceled)
23. (canceled)
24. (canceled)
25. (canceled)
26. (canceled)
27. (canceled)
28. A process for purifying a chlorous acid solution which
comprises contacting said chlorous acid solution with an ion
exchange material in a moist environment for a time sufficient to
remove unwanted ions from said chlorous acid solution.
29. The process as described in claim 28 wherein said ion exchange
material is mixed with an additive.
30. A process for purifying a chlorine dioxide solution which
comprises contacting said chlorine dioxide solution with an ion
exchange material in a moist environment for a time sufficient to
remove unwanted ions from said chlorine dioxide solution.
31. The process as described in claim 30 wherein said ion exchange
material is mixed with an additive.
32. A process for substituting desirable ions for undesirable ions
in a chlorous acid solution which comprises contacting said
chlorous acid solution with an ion exchange material containing
said desirable ions in a moist environment for a time sufficient to
substitute said desirable ions for said undesirable ions in said
chlorous acid solution.
33. The process as described in claim 32 wherein said ion exchange
material is mixed with an additive.
34. The process as described in claim 32 wherein said desirable ion
is a stabilizing ion.
35. A process for substituting desirable ions for undesirable ions
in a chlorine dioxide solution which comprises contacting said
chlorine dioxide solution with an ion exchange material containing
said desirable ions in a moist environment for a time sufficient to
substitute said desirable ions for said undesirable ions in said
chlorine dioxide solution.
36. The process as described in claim 35 wherein said ion exchange
material is mixed with an additive.
37. The process as described in claim 35 where said desirable ion
is a stabilizing ion.
38. A process for adjusting the pH of a chlorous acid solution
which comprises contacting said chlorous acid solution with an ion
exchange material in a moist environment for a time sufficient to
adjust the pH of said chlorous acid solution.
39. The process as described in claim 38 wherein said ion exchange
material is mixed with an additive.
40. A process for adjusting the pH of a chlorine dioxide solution
which comprises contacting said chlorine dioxide solution with an
ion exchange material in a moist environment for a time sufficient
to adjust the pH of said chlorine dioxide solution.
41. The process as described in claim 40 wherein said ion exchange
material is mixed with an additive.
42. The process of claim 1 wherein said aqueous alkali metal halite
comprises an aqueous solution of a chlorite salt.
43. The process of claim 1 wherein said cation exchange material is
selected from the group consisting of weak acid cation resins and
powders, strong acid cation exchange resins and powders, and cation
selected membranes, or any combination of the foregoing.
44. The process of claim 1 wherein said halous acid effluent
comprises an aqueous solution containing chlorous acid.
45. The process of claim 1, wherein said catalytic material is
selected from the group consisting of platinum, palladium,
manganese dioxide, carbon and ion exchange material.
46. The process of claim 1, wherein said halogen oxide produced is
chlorine dioxide.
47. A process for generating chlorine dioxide, the process
comprising: feeding a dilute aqueous chlorite salt solution into a
cation exchange column, wherein the cation exchange column contains
a strong cation exchange material; contacting the dilute aqueous
chlorite salt solution with the strong cation exchange material to
produce an effluent containing chlorous acid; and feeding the
effluent chlorous acid into contact with a platinum catalyst in a
moist environment for a time sufficient to produce chlorine
dioxide.
48. A process for generating chlorine dioxide, the process
comprising: feeding a dilute aqueous chlorate salt precursor
solution and an acid into an anion exchange column, wherein the
anion exchange column is in a reducing ionic form; contacting the
dilute aqueous chlorate salt precursor solution with the anion
exchange material in a reducing ionic form to produce an effluent
containing chlorous acid; and feeding the effluent chlorous acid
into contact with a palladium catalyst in a moist environment for a
time sufficient to produce chlorine dioxide.
Description
FIELD OF INVENTION
[0001] The present invention relates to a method for generating
chlorous acid from an aqueous chlorite salt solution or an aqueous
chlorate salt solution, or a combination of both solutions. The
present invention also relates to a method for generating chlorine
dioxide by means of catalysis of chlorous acid, either subsequent
to or simultaneously with generation of the chlorous acid from a
chlorite/chlorate salt solution.
BACKGROUND OF THE INVENTION
[0002] The generation of chlorous acid by the acidification of an
aqueous chlorite salt solution or stabilized aqueous chlorine
dioxide solution (stabilized chlorite salt solution) by an acid is
well known by the following reaction:
Na.sup.+ClO.sub.2.sup.-+H.sup.+.fwdarw.H.sup.+ClO.sub.2.sup.-+Na.sup.+
(1)
[0003] It is also well known that over time, chlorous acid slowly
decomposes to chlorine dioxide by the following reaction:
5 HClO.sub.2.fwdarw.4 ClO.sub.2+HCl+2H.sub.2O (2)
[0004] This reaction (2) predominates at low acid and high chlorite
concentrations, making the reaction difficult to control,
especially in high alkalinity water supplies. Further, this
decomposition is slow. At chlorite concentrations greater than
20,000 mg/L, the reaction rate is 5 minutes at a pH <0.5.
However, if the pH of the same chlorite solution is increased to
>1.0, the reaction is not complete after 60 minutes.
[0005] It is also well known that in an oxidizing environment, such
as in the presence of chlorine or an anode, chlorine dioxide can be
generated from chlorous acid by the following reaction:
HClO.sub.2-e.sup.-.fwdarw.ClO.sub.2+H.sup.+ (3)
[0006] It is further known that chlorous acid is generated by the
acidification of chlorate salt by the following two-step
reaction:
Na.sup.+ClO.sub.3.sup.-+H.sup.+.fwdarw.H.sup.+ClO.sub.3.sup.-+Na.sup.+
(4)
HClO.sub.3+HCl-->HClO.sub.2+HOCl (5)
[0007] In this reaction, hypochlorous acid, the ionized form of
chlorine in water, is also generated reaction (5). The generation
of chlorine dioxide occurs via the one of the following
mechanisms:
HClO.sub.3+HClO.sub.2-->2ClO.sub.2+H.sub.2O (6)
HOCl+HCl-->Cl.sub.2+H.sub.2O (7)
or
2HClO.sub.2+HOCl+HCl .fwdarw.2ClO.sub.2+2HCl+H.sub.2O (8)
[0008] The generation of chlorine dioxide from chlorate salt,
however, is very difficult to control. In practice, excess acidity
is required to start the reaction, but if the acidity is too high,
the following side reaction predominates, and little to no chlorine
dioxide is generated.
ClO.sub.3.sup.-+6H++6 e.sup.--->Cl.sup.-+3H.sub.2O (9)
[0009] In practice, the following reduction reactions are used to
generate chlorine dioxide from chlorate salt. High concentrations
of all precursors must be used to start the reactions, but when the
reactions do not go to completion, undesirable byproducts or
unreacted precursor materials contaminate the chlorine dioxide
solutions. In addition, the chloride ion must be present, either
from the decomposition of chlorate or the addition of the chloride
ion itself, for chlorine dioxide to be generated. Overall reactions
for the generation of chlorine dioxide from chlorate are listed
below.
2ClO.sub.3.sup.-+SO.sub.2-->2ClO.sub.2+SO.sub.4.sup.2- (10)
4ClO.sub.3.sup.-+CH.sub.3OH+4H.sup.+-->4ClO.sub.2+HCOOH+3H.sub.2O
(11)
ClO.sub.3.sup.-+Cl.sup.-+2H.sup.+-->ClO.sub.2+Cl.sub.2+H.sub.2O
(12)
2ClO.sub.3.sup.-+H.sub.2O.sub.2+2H.sup.+-->2ClO.sub.2+O.sub.2+2H.sub.2O
(13)
[0010] It is further known that a mixture of chlorite salt and
chlorate salt in the presence of hydrogen ion will generate
chlorine dioxide by the following overall reaction:
2H.sup.++ClO.sub.2.sup.-+ClO.sub.3.sup.-.fwdarw.2ClO.sub.2+H.sub.2O
(14)
[0011] This reaction is also shown in a different format in
reaction (6). However, the rate of reaction to chlorine dioxide of
the chlorite salt is 100 times faster than the rate of reaction to
chlorine dioxide of the chlorate salt.
[0012] The use of chlorine dioxide in many applications has been
limited due to the inability to control the reaction chemistries
and the inefficiency of the reactions in solutions. Since chlorine
dioxide is an unstable gas, even in solution, it must be generated
on-site and used shortly after generation. Large-volume industrial
applications such as pulp and paper bleaching, municipal water
pretreatment and disinfection, food processing disinfection, and
cooling tower disinfection have been successful due to the ability
in these applications to safely handle concentrated and aggressive
oxidizers and acids.
[0013] Some consumer and medical applications have also had
success. Chlorite salt-based toothpastes, mouthwashes, and
disinfecting skin gels use either the pH of the mouth or a
weak-acid activator to slightly acidify the chlorite salt so that
some chlorous acid is formed. The chlorous acid will then slowly
decompose to chlorine dioxide by reaction (2).
[0014] It is also described in U.S. Pat. No. 6,200,557 B1 that in a
topical solution designed to treat HIV, the chemical addition of
phosphates will retard the loss of chlorine dioxide from solution
at pH 6-7.4. This is especially beneficial in this topical
application so that contact time of chlorine dioxide on the skin
surface is increased to allow better treatment of the HIV.
[0015] However, in all of the prior art processes, controlling the
reactions has remained a major obstacle. In addition, unreacted
precursor components and reaction by-products are undesirably
carried over into the product solutions. Also, in many instances,
the pH of the product is so low due to the excess acid in solution
that it cannot be used in certain applications.
SUMMARY OF THE INVENTION
[0016] In accordance with the present invention, it has been
discovered that chlorous acid can be generated in a controlled
manner from an aqueous chlorite salt solution or an aqueous
chlorate salt solution, or a combination of both, by ion exchange.
It has further been discovered that chlorine dioxide can be
generated from chlorous acid by the use of at least one catalytic
material. The chlorous acid for conversion to chlorine dioxide can
be by ion exchange reaction in accordance with the present
invention, or by conventional acidification. Preferred catalysts in
accordance with the present invention include platinum, palladium,
manganese dioxide, carbon and ion exchange material.
[0017] The chlorous acid may be generated separately in a first
step and subsequently catalyzed to form the chlorine dioxide in a
second step, or the chlorous acid and the chlorine dioxide may be
generated simultaneously in the same reaction environment in the
presence of the requisite catalyst. The process may be performed in
either a continuous or a batch manner, and the reaction must be
carried out in an aqueous solution or otherwise aqueous moist
environment, i.e., in the presence of water or water vapor.
[0018] In the preferred embodiment of the present invention, the
chlorous acid is generated by a salt cation/hydrogen ion exchange
of chlorite salt or chlorate salt, or a combination of both, and
the chlorous acid is then catalyzed in a moist environment to form
chlorine dioxide either subsequently or simultaneously. Further, it
has been found in accordance with the present invention, that
chlorous acid, generated by the chemical acidification of chlorite
salt or chlorate salt or both can also be catalyzed in a moist
environment to form chlorine dioxide either subsequently or
simultaneously.
[0019] In addition, it has been found in accordance with the
present invention that additional precursors may be used with the
chlorite salt solution or chlorate salt solution to enhance the
catalysis of chlorous acid in a moist environment to form chlorine
dioxide either subsequently or simultaneously. Such precursors
include but are not limited to permanganate ion, chloride ion,
sodium acid sulfite, peroxide and alcohol.
[0020] Still further, it has been found in accordance with the
present invention that anion exchange materials are a preferred
source of chlorite and/or chlorate ion, exchanged with a counter
anion in a moist acidic environment to form chlorous acid, and
further catalyzed in the moist environment to form chlorine dioxide
either subsequently or simultaneously. By the ion exchange, a
solution of chlorous acid can be generated from chlorite salt
and/or chlorate salt by the salt cation/hydrogen ion exchange.
Additionally, ionic contaminants otherwise contained in the
chlorous acid and/or chlorine dioxide solution can be removed with
ion exchange, and ionic stabilizers may be added to the chlorous
acid and/or the chlorine dioxide solutions via ion exchange. Still
further, the pH of the chlorous acid and/or chlorine dioxide
solutions may be adjusted by the use of ion exchange.
[0021] It is, therefore, an object of the present invention to
generate chlorine dioxide from chlorous acid in the presence of at
least one catalytic material in either a continuous or batch
process in an aqueous solution or otherwise aqueous moist
environment.
[0022] Another object of the present invention is to generate a
chlorous acid solution generally free of cations, except hydrogen
ion, in either a continuous or batch process, in an aqueous
solution or otherwise aqueous moist environment.
[0023] A further object of the present invention is to generate
chlorous acid and chlorine dioxide simultaneously in the presence
of at least one catalytic material in either a continuous or batch
process in an aqueous solution or otherwise aqueous moist
environment.
[0024] A still further object of the present invention is to
utilize an anion exchange material to supply chlorite ion and/or
chlorate ion for the generation of chlorous acid in either a
continuous or batch process in an aqueous solution or otherwise
aqueous moist environment.
[0025] Still another object of the present invention is to purify
the resulting chlorous acid and/or chlorine dioxide solution to
remove any ionic contaminants by the use of ion exchange in either
a continuous or batch process.
[0026] Yet a further object of the present invention is to adjust
the pH of either the chlorous acid solution and/or the chlorine
dioxide solution by use of ion exchange in either a continuous or
batch process.
[0027] A final object of the present invention to be stated herein
is to add ionic stabilizers to either the chlorous acid solution
and/or the chlorine dioxide solution by using ion exchange in
either a continuous or batch process.
[0028] These together with other objects and advantages, which will
become subsequently apparent, reside in the details of the
technology as more fully hereinafter described and claimed,
reference being had to the accompanying drawings forming a part
hereof, wherein like numerals refer to like parts throughout.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] FIG. 1 shows an exploded elevational view of a plastic tube
used in the tests of Examples 1-11 described in this
application.
[0030] FIG. 2 is a graph showing the chlorine dioxide concentration
versus time of a decomposing chlorous acid solution generated by
ion exchange.
DETAILED DESCRIPTION OF THE INVENTION
[0031] In describing the present invention, specific terminology
will be used for the sake of clarity. However, the invention is not
intended to be limited to the specific terms so selected, or to the
specific embodiments disclosed. It is to be understood that each
specific term includes all technical equivalents, which operate in
a similar manner to accomplish a similar purpose, and the specific
embodiments are intended to illustrate, but not limit, the broad
technical application and utility of the present invention.
[0032] As used herein, the term "solution" shall mean a mixture
formed by a process by which a solid, liquid, or gaseous substance
is mixed with a liquid, whether that liquid is a droplet, aerosol,
vapor, or mist. Also, as used herein, the term "moist environment"
shall mean that the environment in which the reaction occurs
contains water moisture, ranging from a slightly humid environment
to fully wet. Also, as used herein, the term "precursor" shall be
used to mean any solution and/or combination of solutions used to
generate chlorous acid and/or chlorine dioxide.
[0033] It is well known to those knowledgeable of the manufacture
of chlorine dioxide that chlorous acid is formed by the
acidification of chlorite salt and/or chlorate salt by the
reactions (1), (4), and (5). In these reactions, hydrogen ion is
placed in solution where it partially acidifies the chlorite salt
and/or chlorate salt. The equilibrium conditions of the solution
prevent the total acidification of the chlorite and/or chlorate
salts, however, because sodium ion remains in solution. It has now
been surprisingly found that if the sodium ion is replaced by a
hydrogen ion by means of a cation exchange material, the
equilibrium conditions of the solution change, and total
acidification of the chlorite salt and/or chlorate salt is
possible, thereby making a pure chlorous acid solution.
[0034] Chlorous acid and aqueous solutions containing chlorous acid
are particularly useful in applications where low-level
disinfection over a long period of time is desirable. Some of these
applications include disinfection of skin, the mouth, and cow
teats. In addition, chlorous acid has a relatively low volatility
level, making it applicable for surface disinfection in
environments where off-gassing could be harmful. However, due to
relatively high levels of residual chlorite in chlorous acid
solutions and their inability to rapidly disinfect, chlorine
dioxide is preferred in applications such as the disinfection of
drinking water, cooling towers, food, and surfaces. In addition,
chlorine dioxide is desirable for oxidizing organic contaminants
and reducing iron and manganese levels in drinking water.
[0035] Further, it has been surprisingly discovered that a chlorous
acid solution can be readily catalyzed to form chlorine dioxide.
The source of the chlorous acid solution can be either that
generated by ion exchange or by conventional acidification. If the
latter, the catalytic conversion of the chlorous acid to chlorine
dioxide drives the acidification reaction to completion or
substantial completion.
[0036] By definition, catalysts work by changing the activation
energy for a reaction, i.e. the minimum energy needed for the
reaction to occur. This is accomplished by providing a new
mechanism or reaction path through which the reaction can proceed.
When the new reaction path has a lower activation energy, the
reaction rate is increased, and the reaction is said to be
catalyzed. When catalysis is used to generate chlorine dioxide from
chlorous acid in the present invention, it was surprisingly found
that neither high concentrations of precursor solutions nor high
concentrations of chlorous acid were required to initiate the
reactions. Further, it was surprisingly discovered that the
reactions proceeded toward completion rapidly, thus decreasing the
opportunity for undesirable byproducts or unreacted precursor
materials to contaminate the chlorine dioxide solutions.
[0037] There are many catalysts that can be used within the scope
of the present invention. These include, but are not limited to
platinum, palladium, manganese dioxide, carbon, and ion exchange
material. Further, it is well known that depositing such catalysts
on various substrates, such as zeolites, aids in the catalysis by
increasing surface area. Such catalysts are commercially available,
and it is within the scope of those skilled in the art to choose an
appropriate catalytic material and/or substrate to catalyze
chlorous acid to chlorine dioxide.
[0038] Further, it has been discovered that an anion exchange
material can be used to contribute a controlled amount of anions to
the precursor, chlorous acid solution, and/or chlorine dioxide
solution. For example, the chloride ion must be present for
chlorous acid to be generated from a chlorate salt precursor.
Although the necessary chloride may be present from the
decomposition of chlorate, anion resin in the chloride form may be
used to contribute additional chloride ion to the acidified
chlorate salt precursor.
[0039] Ion exchange material can also be used to remove unwanted
ions from the precursor, chlorous acid, and/or chlorine dioxide
solution. For example, if the reaction to chlorine dioxide does not
go to completion, unreacted chlorite and/or chlorate anion will be
present in the chlorine dioxide solution. Anion exchange material
can be used to remove the chlorite and/or chlorate ion. Further, if
the precursor solution is acidified chemically, excess sodium ion
will be present in the chlorine dioxide solution. Cation exchange
material can be used to remove the sodium ion.
[0040] Ion exchange materials, such as inorganic and organic
resins, membranes, powders, gels, and solutions are well known to
those skilled in the art, and the type of ion exchange material
used does not limit the invention. Examples of ion exchange
materials are weak acid cation resins and powders, strong acid
cation resins and powders, weak base anion resins and powders,
strong base anion resins and powders, sulfonated polystyrene
solutions, cation and anion selective membranes. Selection of a
particular ion exchange material is considered within the skill of
those knowledgeable in the field.
[0041] In one form of the present invention, cation exchange
material is used to exchange the salt cation in a chlorite
precursor with hydrogen ion to form chlorous acid. The resulting
chlorous acid is then placed in contact with a catalytic material
for a time sufficient to form chlorine dioxide. If the chosen
catalyst is able to perform oxidation, such as manganese dioxide on
the surface of greensand, reaction (3) predominates, and 100% of
the chlorous acid can convert to chlorine dioxide. However, if the
chosen catalyst is unable to perform oxidation, such as platinum,
reaction (2) predominates, and only 80% of the chlorous acid can
convert to chlorine dioxide.
[0042] In another form of the present invention, acid is added to
the chlorite precursor to form chlorous acid with the salt cation
still present in solution. The chlorous acid is then placed in
contact with a catalytic material for a time sufficient to form
chlorine dioxide. The choice of which acid to use depends upon the
application. For example, if the chlorous acid and/or chlorine
dioxide solution is to be used in a food processing application, an
acid such as acetic acid may be preferred. If the chlorous acid
and/or chlorine dioxide solution is to be used in a high purity
industrial application, electrochemically-generated acid may be
used. The choice of acid is well within the scope of knowledge of
those skilled in this technology.
[0043] In another form of the present invention, an acidic reducing
agent precursor is added to the chlorate precursor as the chlorate
precursor is placed in contact with a catalytic material for a time
sufficient to cause the generation of chlorous acid and chlorine
dioxide simultaneously. If hydrochloric acid is used, it supplies
both the acidity and the chloride required for the reaction.
However, any acid source may be used, and the necessary chloride
may come from the decomposition of the chlorate ion.
[0044] In another form of the present invention, an acid precursor
and a reducing agent precursor are added to the chlorate precursor
as the chlorate precursor is placed in contact with a catalytic
material for a time sufficient to cause the generation of chlorous
acid and chlorine dioxide simultaneously. Any acid source may be
used, and the necessary chloride may come from the decomposition of
the chlorate ion.
[0045] In another form of the present invention, a chlorate
precursor is placed in contact with a cation exchange material
mixed with a catalytic material. The salt cation in the chlorate
precursor is exchanged with hydrogen ion as the chlorate precursor
contacts both the cation exchange material and the catalytic
material for a time sufficient to cause the generation of chlorous
acid and chlorine dioxide simultaneously. If necessary, other
precursors, such as sodium chloride, may be dosed along with the
chlorate precursor to aid in the reaction.
[0046] In yet another form of the present invention, a reducing
agent is placed in contact with the chlorate precursor either prior
to the precursor being placed in contact with the catalytic
material or as the precursor is placed in contact with the
catalytic material for a time sufficient to form chlorine dioxide.
In this form of the present invention, the catalytic material aids
in reactions (10), (11), (12), and (13).
[0047] In another form of the present invention, a mixed chlorite
and chlorate precursor is acidified as it is placed into contact
with a catalytic material for time sufficient to form chlorine
dioxide.
DESCRIPTION OF SPECIFIC EMBODIMENTS AND EXAMPLES
Precursor Solution for Examples 1-6
[0048] In Examples 1-6, a single chlorite precursor solution was
used for all Examples. The chlorite precursor solution was prepared
by diluting an aqueous 25% sodium chlorite solution with reverse
osmosis water. The pH of the resultant solution was measured to be
8.5 with a Hach Sension 1 pH meter. The chlorite concentration in
the precursor solution was measured to be 823 mg/L by using a Hach
Digital Titrator, Iodometric Test Kit for Chlorine. To begin the
measurement, 100 ml of reverse osmosis water was placed in a 250-ml
Erlenmeyer flask, and 2 ml of the sample precursor solution was
placed into the reverse osmosis water. One Potassium Iodide Powder
Pillow and one Dissolved Oxygen Reagent 3 Pillow were added to the
solution in the flask, swirled to mix, and placed in the dark for
10 minutes to allow the reaction to go to completion. Using a 0.113
N Sodium Thiosulfate Cartridge in the Digital Titrator, the
solution was titrated to a pale yellow. Next, Starch Indicator
Solution was added until the solution turned blue. The solution was
titrated again until the solution remained colorless for 30
seconds. The titrator reading was recorded and divided by 800 to
determine the milliliters of titrant used. Then the values were
plugged into the following formula to determine the concentration
of chlorite in the precursor solution: 1 ml of titrant .times.
normality of sodium thiosulfate .times. 67 , 450 ml of sample
.times. 4
Plastic Testing Tubes for Examples 1-10
[0049] A sample of the plastic tubes used for carrying out the
tests set forth in Examples 1-10 in the present application is
shown in FIG. 1 and generally designated by reference numeral 100.
The plastic test tube 100 includes a generally cylindrical body 102
having a conventional connection closure mounted at each end in the
form of an inlet bottom connection 104 and an outlet upper end
connection 106. Porex support media was cut to fit the inner
diameter of the cylindrical tube 102, and a Porex disk 108 was
placed at each end between the end of the cylindrical tubing 102
and the end closures 104 and 106 to act as support for the filling.
The feed tubing ran to the inlet bottom connection 104 and outlet
tubing ran from the outlet upper end connection 106.
Example 1
Chlorous Acid Generation by Cation Exchange
[0050] In Example 1, one 30 ml plastic test tube 100 as shown in
FIG. 1 was clipped to a wall with pipe clips. The feed tubing ran
from a reservoir containing the precursor solution to the bottom of
the tube. The product tubing ran from the top of the tube to a
brown sample bottle. In this example, the tube was filled with a
commercially available strong acid organic cation resin in the
hydrogen form, sold under the name Resintech CG-8, such that the
tube was full.
[0051] A continuous stream of the chlorite precursor solution was
passed upwardly through the tube such that the flow rate was 30
ml/min. A 250 ml sample of solution was taken from the tube's top
end and placed in the brown bottle, sealed, and stored in a dark
cabinet. A Hach 2010 Spectrophotometer using Method 8138 for the
measurement of chlorine dioxide (0-700 mg/L) was used to test the
stored sample for chlorine dioxide at one-hour intervals for eight
hours.
[0052] The results of the foregoing test demonstrate, first, that
chlorous acid may be generated from a chlorite precursor when
placed in contact with a cation exchange material. Second, the
development of chlorous acid to chlorine dioxide over time in this
test are shown in FIG. 2, which demonstrates the slow reaction time
for chlorous acid to decompose to chlorine dioxide.
Example 2
Chlorous Acid Generation by Cation Exchange from a Chlorite
Precursor and Subsequent Catalytic Chlorine Dioxide Generation
[0053] In Example 2, two identical 30 ml plastic test tubes 100 as
shown in FIG. 1 were clipped to a wall with pipe clips.
Interconnecting plastic tubing ran from the first test tube to the
second so that solution flowed from the bottom to the top of each
test tube. The feed tubing ran from a reservoir containing the
precursor solution to the bottom of the first test tube. The
product tubing ran from the top of the second test tube to the
flow-through cell of a Hach 2010 Spectrophotometer using Method
8138 for the measurement of chlorine dioxide (0-700 mg/L).
[0054] (A) The first test tube was filled with the Resintech CG-8
strong acid organic cation resin in the hydrogen form such that the
tube was full. The second test tube was packed with a commercially
available inorganic cation resin in the hydrogen form, sold under
the name Resintech SIR-600, having platinum catalyst placed on the
surface of the inorganic cation resin such that the tube was full.
To place the platinum on the surface of the Resintech SIR-600
resin, a 100-ml solution of platinnic chloride was made such that
the solution contained 1 gram of platinum. The platinnic chloride
solution was then sprayed in a fine mist onto the surface of one
liter of Resintech SIR-600 resin so as to form an even coating. The
coated Resintech SIR-600 resin was then placed in an oven at
550.degree. F. for three hours. Although platinnic chloride was
used in this test, any soluble platinum salt could have been used
for the coating material. Such salts and methods are well known to
those schooled in the art of catalysis, and many are readily
available as standard products. A continuous stream of the chlorite
precursor solution was passed sequentially through the first and
then the second test tube such that the flow rate was 30
ml/min.
[0055] (B) The first test tube was filled with the Resintech CG-8
strong acid organic cation resin in the hydrogen form such that the
tube was full. The second test tube was packed with acid-washed
carbon particles such that the drying tube was full. A continuous
stream of the chlorite precursor solution was passed sequentially
through the first and then the second test tube such that the flow
rate was 30 ml/min.
[0056] (C) The first test tube was filled with the Resintech CG-8
strong acid organic cation resin in the hydrogen form such that the
tube was full. The second test tube was packed with acid-washed
carbon particles having platinum catalyst placed on the surface of
the acid-washed carbon such that the tube was full. The platinum
was placed on the surface of the acid-washed carbon particles by
the same method described in Example 2(A) above for depositing
platinum on the surface of the cation resin. A continuous stream of
the chlorite precursor solution was passed sequentially through the
first and then the second test tube such that the flow rate was 30
ml/min.
[0057] (D) The first test tube was filled with the Resintech CG-8
strong acid organic cation resin in the hydrogen form such that the
tube was full. The second test tube was packed with regenerated
manganese greensand such that the tube was full. A continuous
stream of the chlorite precursor solution was passed sequentially
through the first and then the second test tube such that the flow
rate was 30 ml/min.
[0058] (E) The first test tube was filled with the Resintech CG-8
strong acid organic cation resin in the hydrogen form such that the
tube was full. The second test tube was packed with the Resintech
SIR-600 inorganic cation exchange resin having manganese dioxide
placed on the surface of the inorganic cation exchange material
such that the tube was full. To place the manganese dioxide on the
surface of the Resintech SIR-600 resin, a 100-ml solution of
manganese sulfate was made such that the solution contained 1 gram
of manganese. The manganese sulfate solution was then sprayed in a
fine mist onto the surface of one liter of Resintech SIR-600 resin
so as to form an even coating. The coated Resintech SIR-600 resin
was then placed in an oven at 550.degree. F. for three hours which
converted the manganese to manganese dioxide. Although manganese
sulfate was used in this test, any soluble manganese salt could
have been used for the coating material. Such salts and methods are
well known to those schooled in the art of catalysis, and many are
readily available as standard products. A continuous stream of the
chlorite precursor solution was passed sequentially through the
first and then the second test tube such that the flow rate was 30
ml/min.
[0059] (F) The first test tube was filled with the Resintech CG-8
strong acid organic cation resin in the hydrogen form such that the
tube was full. The second test tube was packed with a chlorite
regenerated form of a commercially available organic anion exchange
material having palladium on the resin, sold under the name Lewatit
K7333 by Bayer Corporation, such that the tube was full. As
purchased, the resin is in the hydroxyl form, but for this example,
the resin was regenerated with sodium chlorite solution so as to
place the resin in the chlorite form. A continuous stream of the
chlorite precursor solution was passed sequentially through the
first and then the second test tube such that the flow rate was 30
ml/min.
[0060] The results of the tests in Examples 2(A) through 2(F) are
shown in the following Table 1.
1 TABLE 1 Chlorine Dioxide Example No. Concentration (mg/L) 2(A)
575 2(B) 427 2(C) 526 2(D) 549 2(E) 804 2(F) 284
[0061] Table 1 shows the concentration of chlorine dioxide after
the chlorous acid from the first tube has been catalytically
converted to chlorine dioxide in the second tube in the tests of
Examples (A) through (F).
[0062] It will be seen that chlorous acid is significantly more
readily converted to chlorine dioxide in the presence of a
catalyst, as shown in all of Examples 2(A) through 2(F), compared
to known chemical decomposition, as shown in Example 1, in which
the chlorine dioxide concentration reaches only about 130 mg/L
after eight hours, see FIG. 2.
Example 3
Simultaneous Generation of Chlorous Acid and Chlorine Dioxide by a
Combination of Cation Exchange and Catalysis from a Chlorite
Precursor
[0063] In Example 3, one 30 ml plastic test tube 100 as shown in
FIG. 1 was clipped to a wall with pipe clips. The feed tubing ran
from a reservoir containing the precursor solution to the bottom of
the tube. The product tubing ran from the top of the tube to the
flow-through cell of a Hach 2010 Spectrophotometer using Method
8138 for the measurement of chlorine dioxide (0-700 mg/L). In this
example, the test tube 100 was packed with a 50/50 mixture of the
Resintech CG-8 strong acid organic cation resin in the hydrogen
form and the Resintech SIR-600 inorganic cation resin in the
hydrogen form having platinum catalyst placed on the surface of the
inorganic cation resin in the method as described above in Example
2(A) such that the test tube was full.
[0064] A continuous stream of the chlorite precursor solution was
passed through the test tube such that the flow rate was 30 ml/min.
The resultant concentration of chlorine dioxide from the test tube
was 522 mg/L. It will thus be seen that the simultaneous generation
of chlorous acid and chlorine dioxide readily occurs from a
chlorite precursor solution in the presence of a cation exchange
material and suitable catalyst.
Example 4
Simultaneous Generation of Chlorous Acid and Chlorine Dioxide by a
Combination of Acidification and Catalysis from a Chlorite
Precursor
[0065] In Example 4, one 30 ml plastic test tube 100 as shown in
FIG. 1 was clipped to a wall with pipe clips. The feed tubing ran
from a reservoir containing the precursor solution to the bottom of
the test tube. The product tubing ran from the top of the test tube
to the flow-through cell of a Hach 2010 Spectrophotometer using
Method 8138 for the measurement of chlorine dioxide (0-700 mg/L).
In this example, the test tube 100 was packed with the Resintech
SIR-600 inorganic cation resin in the hydrogen form having platinum
catalyst placed on the surface of the inorganic cation resin in the
method as described above in Example 2(A) such that the test tube
was full.
[0066] A continuous stream of the chlorite precursor solution was
acidified to a pH of 2.5 and passed through the test tube such that
the flow rate was 30 ml/min. The resultant concentration of
chlorine dioxide from the test tube was 522 mg/L. It will thus be
seen that the simultaneous generation of chlorous acid and chlorine
dioxide readily occurs from an acidified chlorite precursor
solution in the presence of a suitable catalyst.
Example 5
Purification of a Chlorine Dioxide Solution with Ion Exchange
[0067] (A) In Example 5 (A), two 30 ml plastic test tubes 100 as
shown in FIG. 1 were clipped to a wall with pipe clips.
Interconnecting plastic tubing ran from the first test tube to the
second so that solution flowed from the bottom to the top of each
tube. The feed tubing ran from a reservoir containing the precursor
solution to the bottom of the first test tube. The product tubing
ran from the top of the second test tube to the flow-through cell
of a Hach 2010 Spectrophotometer using Method 8138 for the
measurement of chlorine dioxide (0-700 mg/L). The first test tube
was filled with the Resintech CG-8 strong acid organic cation resin
in the hydrogen form such that the tube was full. The second test
tube was packed with the Resintech SIR-600 inorganic cation resin
in the hydrogen form having platinum catalyst placed on the surface
of the inorganic cation resin in the method as described above in
Example 2 (A) such that the tube was full. A continuous stream of
the chlorite precursor solution was passed sequentially through the
test tubes such that the flow rate was 30 ml/min.
[0068] (B) In Example 5 (B), three 30 ml plastic test tubes 100 as
shown in FIG. 1 were clipped to a wall with pipe clips.
Interconnecting plastic tubing ran from the first test tube to the
second and from the second to the third so that solution flowed
from the bottom to the top of each test tube. The feed tubing ran
from a reservoir containing the precursor solution to the bottom of
the first test tube. The product tubing ran from the top of the
third test tube to the flow-through cell of a Hach 2010
Spectrophotometer using Method 8138 for the measurement of chlorine
dioxide (0-700 mg/L). The first and second test tubes were filled
as in Example 5(A). The third test tube was packed with a 50/50
mixture of the Resintech CG-8 strong acid organic cation resin in
the hydrogen form and a commercially available weak base organic
anion resin in the hydroxyl form, sold under the name Resintech
WBMP, such that the tube was full. A continuous stream of the
chlorite precursor solution was passed sequentially through the
test tubes such that the flow rate was 30 ml/min.
[0069] The results of the tests in Examples 5(A) and 5(B) are shown
in the following Table 2.
2 TABLE 2 Chlorine Dioxide Example No. Concentration (mg/L) 5(A)
546 5(B) 542
[0070] Table 2 shows the concentration of chlorine dioxide before
purification by ion exchange (Example 5 (A)), and after
purification by ion exchange (Example 5(B)). It will thus be seen
that the concentration of chlorine dioxide is not affected if the
chlorine dioxide solution is purified by ion exchange.
Example 6
pH Adjustment of a Chlorine Dioxide Solution with Ion Exchange
[0071] (A) In Example 6(A), two 30 ml plastic test tubes 100 as
shown in FIG. 1 were clipped to a wall with pipe clips.
Interconnecting plastic tubing ran from the first test tube to the
second so that solution flowed from the bottom to the top of each
tube. The feed tubing ran from a reservoir containing the precursor
solution to the bottom of the first test tube. The product tubing
ran from the top of the second test tube to the flow-through cell
of a Hach 2010 Spectrophotometer using Method 8138 for the
measurement of chlorine dioxide (0-700 mg/L). The first test tube
was filled with the Resintech CG-8 strong acid organic cation resin
in the hydrogen form such that the tube was full. The second test
tube was packed with the Resintech SIR-600 inorganic cation resin
in the hydrogen form having platinum catalyst placed on the surface
of the inorganic cation resin in the method as described above in
Example 2 (A) such that the tube was full. A continuous stream of
the chlorite precursor solution was passed sequentially through the
test tubes such that the flow rate was 30 ml/min. The pH of the
resultant solution was 2.4.
[0072] (B) In Example 6(B), three 30 ml plastic test tubes 100 as
shown in FIG. 1 were clipped to a wall with pipe clips.
Interconnecting plastic tubing ran from the first test tube to the
second and from the second to the third so that solution flowed
from the bottom to the top of each tube. The feed tubing ran from a
reservoir containing the precursor solution to the bottom of the
first test tube. The product tubing ran from the top of the third
test tube to the flow-through cell of a Hach 2010 Spectrophotometer
using Method 8138 for the measurement of chlorine dioxide (0-700
mg/L). The first and second test tubes were filled as in Example
6(A). The third test tube was packed with an inorganic anion resin,
hydrotalcite, in the carbonate form such that the drying tube was
full. A continuous stream of the chlorite precursor solution was
passed sequentially through the test tubes such that the flow rate
was 30 ml/min. The pH of the resultant solution was 8.1.
[0073] The results of the tests in Examples 6(A) and 6(B) are shown
in the following Table 3.
3 TABLE 3 Chlorine Dioxide Example No. Concentration (mg/L) 6(A)
546 6(B) 541
[0074] Table 3 shows the concentration of chlorine dioxide before
and after pH adjustment. It will accordingly be seen that the
concentration of chlorine dioxide is not affected if the pH of the
chlorine dioxide solution is adjusted by ion exchange.
Example 7
Addition of Stabilizing Ion to Chlorine Dioxide Solution
[0075] (A) In Example 7 (A), two 30 ml plastic test tubes 100 as
shown in FIG. 1 were clipped to a wall with pipe clips.
Interconnecting plastic tubing ran from the first test tube to the
second so that solution flowed from the bottom to the top of each
tube. The feed tubing ran from a reservoir containing the precursor
solution to the bottom of the first test tube. The product tubing
ran from the top of the second test tube to the flow-through cell
of a Hach 2010 Spectrophotometer using Method 8138 for the
measurement of chlorine dioxide (0-700 mg/L). The first test tube
was filled with the Resintech CG-8 strong acid organic cation resin
in the hydrogen form such that the tube was full. The second test
tube was packed with the Resintech SIR-600 inorganic cation resin
in the hydrogen form having platinum catalyst placed on the surface
of the inorganic cation resin in the method described above in
Example 2 (A) such that the tube was full. A continuous stream of
the chlorite precursor solution was passed sequentially through the
test tubes such that the flow rate was 30 ml/min. The pH of the
resultant solution was 2.4.
[0076] (B) In Example 7 (B), three 30 ml plastic test tubes 100 as
shown in FIG. 1 were clipped to a wall with pipe clips.
Interconnecting plastic tubing ran from the first test tube to the
second and from the second to the third so that solution flowed
from the bottom to the top of each tube. The feed tubing ran from a
reservoir containing the precursor solution to the bottom of the
first test tube. The product tubing ran from the top of the third
test tube to the flow-through cell of a Hach 2010 Spectrophotometer
using Method 8138 for the measurement of chlorine dioxide (0-700
mg/L). The first and second test tubes were filled as in Example
7(A). The third test tube was packed with an inorganic anion resin,
hydrotalcite, in the phosphate form such that the tube was full. A
continuous stream of the chlorite precursor solution was passed
sequentially through the tubes such that the flow rate was 30
ml/min. The pH of the resultant solution was 7.8.
[0077] The results of the tests in Examples 7(A) and 7(B) are shown
in the following Table 4.
4 TABLE 4 Chlorine Dioxide Example No. Concentration (mg/L) 7(A)
546 7(B) 544
[0078] Table 4 shows the concentration of chlorine dioxide before
and after the addition of a stabilizing ion. It will thus be seen
that the concentration of chlorine dioxide is not affected when a
stabilizing ion, such as phosphate, is added to the chlorine
dioxide solution.
Example 8
Simultaneous Generation of Chlorous Acid and Chlorine Dioxide by a
Combination of Cation Exchange and Catalysis from a Chlorate
Precursor
[0079] In Example 8, a precursor solution was made containing both
chlorate ion and chloride ion such that the concentration of the
solution was 7,830 mg/L as chlorate and 4087 mg/L as chloride. The
precursor solution was then placed in a reservoir and flowed
through the apparatus.
[0080] One 30 ml plastic test tube 100 as shown in FIG. 1 was
clipped to a wall with pipe clips. The feed tubing ran from a
reservoir containing the precursor solution to the bottom of the
test tube. The product tubing ran from the top of the tube to the
flow-through cell of a Hach 2010 Spectrophotometer using Method
8138 for the measurement of chlorine dioxide (0-700 mg/L). In this
example, the test tube was packed the same as in Example 3.
[0081] A continuous stream of the chlorate precursor solution was
passed through the test tube such that the flow rate was 30 ml/min.
The resultant concentration of chlorine dioxide from the test tube
was 93 mg/L. It will thus be seen that a simultaneous generation of
chlorous acid and chlorine dioxide from a chlorate precursor
solution occurs in the presence of a cation exchange material and
suitable catalyst.
Example 9
Simultaneous Chlorous Acid and Chlorine Dioxide Generation using
Ion Exchange and a Hydrochloric Acid Precursor
[0082] In Example 9, one 30 ml plastic test tube 100 as shown in
FIG. 1 was clipped to a wall with pipe clips. The feed tubing ran
from a gas-washing bottle containing 150 ml of a 30% hydrochloric
acid precursor solution to the bottom of the test tube. The product
tubing ran from the top of the test tube to a second gas-washing
bottle that contained 200 ml of reverse osmosis water. The test
tube was packed with a chlorate regenerated form of a commercially
available organic anion exchange material having palladium on the
resin, sold under the name Lewatit K7333 by Bayer Corporation, such
that the tube was full. As purchased, the resin is in the hydroxyl
form, but for this example, the resin was regenerated with sodium
chlorate solution so as to place the resin in the chlorate form.
The hydrochloric acid vapor was stripped from the hydrochloric acid
precursor solution with compressed air and the vapor then flowed
through the test tube. The final product from the test tube was
sparged into the water in the second gas-washing bottle. The
resultant solution from the second gas-washing bottle was tested
for chlorine dioxide with a Hach 2010 Spectrophotometer using
Method 8138 for the measurement of chlorine dioxide (0-700
mg/L).
[0083] A continuous stream of hydrochloric acid precursor vapor was
passed through the test tube for 5 minutes. After 5 minutes, the
concentration of chlorine dioxide was measured in the second
gas-washing bottle. The resultant concentration of chlorine dioxide
from the tube collected in the second gas-washing bottle was 187
mg/L. It will hence be seen that a simultaneous generation of
chlorous acid and chlorine dioxide occurs in the presence of an
acidic reducing agent, a suitable catalyst, and an anion exchange
material in the chlorate form.
Example 10
Simultaneous Chlorous Acid and Chlorine Dioxide Generation using
Ion Exchange and a Sodium Acid Sulfite Precursor
[0084] In Example 10, one 30 ml plastic test tube 100 as shown in
FIG. 1 was clipped to a wall with pipe clips. The feed tubing ran
from a gas-washing bottle containing 150 ml of a 20% sodium acid
sulfite (NaHSO.sub.3) precursor solution to the bottom of the test
tube. The product tubing ran from the top of the test tube to a
second gas-washing bottle that contained 200 ml of reverse osmosis
water. The test tube was packed with the same organic anion
exchange material in the chlorate form having palladium on the
resin as described in Example 9 such that the tube was full. The
sodium acid sulfite vapor was stripped from the sodium acid sulfite
precursor solution with compressed air and the sodium acid sulfite
vapor then flowed through the tube. The final product from the test
tube was sparged into the water in the second gas-washing bottle.
The resultant solution from the second gas-washing bottle was
tested for chlorine dioxide with a Hach 2010 Spectrophotometer
using Method 8138 for the measurement of chlorine dioxide (0-700
mg/L).
[0085] A continuous stream of sodium acid sulfite precursor vapor
was passed through the tube for 5 minutes. After 5 minutes, the
concentration of chlorine dioxide was measured in the second
gas-washing bottle. The resultant concentration of chlorine dioxide
from the test tube collected in the second gas-washing bottle was
576 mg/L. It will therefore be seen that a simultaneous generation
of chlorous acid and chlorine dioxide occurs in the presence of an
acidic reducing agent, a suitable catalyst, and an anion exchange
material in the chlorate form.
Example 11
Simultaneous Chlorous Acid and Chlorine Dioxide Generation using an
Ion Exchange Catalyst and a Sodium Acid Sulfite Precursor
[0086] In Example 11, one 30 ml plastic test tube 100 as shown in
FIG. 1 was clipped to a wall with pipe clips. The feed tubing ran
from a gas-washing bottle containing 150 ml of a 20% sodium acid
sulfite (NaHSO.sub.3) precursor solution to the bottom of the test
tube. The product tubing ran from the top of the test tube to a
second gas-washing bottle that contained 200 ml of reverse osmosis
water. The test tube was packed with a known inorganic anion resin,
hydrotalcite, regenerated to be in the chlorate form, such that the
drying tube was full. The sodium acid sulfite vapor was stripped
from the sodium acid sulfite precursor solution with compressed air
and the sodium acid sulfite vapor then flowed through the tube. The
final product from the test tube was sparged into the water in the
second gas-washing bottle. The resultant solution from the second
gas-washing bottle was tested for chlorine dioxide with a Hach 2010
Spectrophotometer using Method 8138 for the measurement of chlorine
dioxide (0-700 mg/L).
[0087] A continuous stream of sodium acid sulfite precursor vapor
was passed through the test tube for 5 minutes. After 5 minutes,
the concentration of chlorine dioxide was measured in the second
gas-washing bottle. The resultant concentration of chlorine dioxide
from the test tube collected in the second gas-washing bottle was
318 mg/L. It will thus be seen that a simultaneous generation of
chlorous acid and chlorine dioxide occurs in the presence of an
acidic reducing agent and a catalytic anion exchange material in
the chlorate form.
[0088] The foregoing descriptions and examples should be considered
as illustrative only of the principles of the invention. Since
numerous applications of the present invention will readily occur
to those skilled in the art, it is not desired to limit the
invention to the specific examples disclosed or the exact
construction and operation shown and described. Rather, all
suitable modifications and equivalents may be resorted to, falling
within the scope of the invention.
* * * * *