AU2000241892B2 - Electrolytic process and apparatus for the controlled oxidation and reduction of inorganic and organic species in aqueous solutions - Google Patents

Description

WO 01/78879 PCT/USOO/08732 ELECTROLYTIC PROCESS AND APPARATUS FOR THE CONTROLLED OXIDATION AND REDUCTION OF INORGANIC AND ORGANIC SPECIES IN AQUEOUS SOLUTIONS FIELD OF INVENTION The present invention relates generally to the oxidation or reduction of inorganic and organic species in an aqueous solution by passing the aqueous solution through a packed bed ion exchange electrolytic reactor. More specifically, the present invention relates to a modification of the process and apparatus disclosed in our earlier U.S. Patents Nos. 5,419,816, issued May 1995, 5,609,742, issued March 11, 1997, 5,705,050, issued June 6, 1998 and 6,024,850, issued February 15, 2000, the disclosure of which are all incorporated herein by reference for all purposes as if fully set forth, in order to achieve an improved oxidation or reduction of the species or a specialized end product.

BACKGROUND OF THE INVENTION It is generally known that oxidizing and reducing inorganic and organic species in dilute aqueous solutions by electrolysis is nearly impossible to accomplish because of the poor mobility of these species in such aqueous solutions to reach the anodic or cathodic site where the oxidation or reduction takes place. The poor mobility causes a starvation of the reactive species to the respective anode or cathode, and this starvation is called polarization.

In an open cell electrolytic system with the latest dimensionally stable electrodes, high concentrations of the species to be oxidized or reduced must be flowed through the reactor to achieve even low conversion rates due to this problem of polarization. However, in a packed bed ion exchange electrolytic system as described in Sampson US Pat. No 5,419,816 (the "Sampson '816 patent"), much higher conversion percentages are achieved at much lower concentrations of the inorganic or organic species to be oxidized or reduced. The Sampson '816 patent describes a process for oxidizing a species in a dilute aqueous solution by passing the species though an electrolytic reactor packed with a monobed of modified cation exchange material. This modified cation exchange material has been treated such that a portion of its ion exchange sites are converted to so-called "semiconductor junctions" so that oxidation occurs both at the anode surface and at the semiconductor junction sites. A similar electrolytic process is described and claimed in Sampson U.S. Patent No. 5,609,742 (the "Sampson '742 patent") for reducing a species using a monobed of modified anion exchange material with the reduction taking place at the cathode surface and at the semiconductor junction sites.

-1- SUBSTITUTE SHEET (RULE 26) WO 01/78879 PCT/USOO/08732 Whereas the Sampson '816 patent describes the packed bed of the electrolytic process and apparatus as being all of one species, such as all modified cation exchange resin or all modified anion exchange resin, Sampson US Pat. No. 5,705,050 (the "Sampson '050 patent") describes that variations in the bed are possible, including the presence of additional material. The Sampson '816 patent also identifies only one type physical form for the monobed ion exchange material, whereas the Sampson '050 patent describes other physical forms as being utilized. However, these earlier processes and apparatuses encounter certain drawbacks in certain oxidation or reduction applications, or in customizing the final product stream.

SUMMARY OF THE INVENTION In describing the present invention, specific terminology will be resorted to 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 to limit, the broad technical application and utility of the present invention.

As used herein, the term "modified particulate ion exchange material" has the same meaning as taught by the Sampson '816 patent, and the term "modified ion exchange material" has the same meaning as "modified particulate ion exchange material" except the ion exchange material is not necessarily particulate in nature, which means it is not necessarily in granules, beads, or grains. Such non-particulate ion exchange material may include, but is not limited to, ion exchange powder and membranes or diaphragms, such as described in the Sampson '050 patent. Such ion exchange materials having different physical properties are known to those skilled in the art and understanding a particular ion exchange material having particular physical properties is considered within the skill of those knowledgeable in the field.

Also, as used herein, the term "unmodified ion exchange material" means conventional ion exchange materials, without modification as taught by the Sampson '816 and Sampson U.S.

Patent No. 6,024,850 (the "Sampson '850 patent") and without regard to the physical properties of the material. Hence, unmodified ion exchange material can take any physical form and includes granules, beads, grains, powder and membranes or diaphragms. Examples of conventional unmodified ion exchange resins or materials are disclosed in the Sampson '816 and '850 patents.

The terms "unmodified ion exchange membrane" and "modified ion exchange membrane" have the same meaning as "unmodified ion exchange material" and "modified ion exchange -2- SUBSTITUTE SHEET (RULE 26) WO 01/78879 PCT/US00/08732 material", respectively, except in each instance the ion exchange material, whether unmodified or modified, is in the physical form of a membrane or diaphragm.

Further, the term "monobed" has a special meaning as used herein, and refers to a bed of ion exchange material having the same ionic species, all cationic or all anionic, but not necessarily possessing the same physical properties. Hence, the monobed of ion exchange material in accordance with the present invention may consist of a mixture of ion exchange beads (particulate) and one or more ion exchange membranes of the same charge, as well as other physical forms of the ion exchange material.

Also, as used herein, the term "segment" refers to discrete portions of the monobed, each segment possessing its own physical properties through which an aqueous solution can pass without entering another segment or segments. The term "layer" refers to discrete portions of the segment or monobed, each layer possessing its own physical properties and through which the aqueous solution passes sequentially.

In addition, the term "primary electrode" refers to the anode for oxidation and to the cathode for reduction.

It has been discovered that when ion exchange materials are modified so as to create semiconductor junctions, in accordance with the teaching of the Sampson '816 and '850 patents, the majority of the transfer sites converted to semiconductor junctions exist near the surface of the ion exchange material. This surface phenomenon is advantageous in many circumstances, because the semiconductor sites are more readily accessible to the species to be oxidized or reduced. However, the remaining transfer sites on the ion exchange material are deep within the ion exchange material. This subsurface concentration tends to retard the desired ion diffusion through the monobed toward the respective anode or cathode. We have discovered that this problem can be overcome by including a portion of unmodified ion exchange material in the monobed with the modified material in order to increase the number of transfer sites available at the surface of the particulate resin.

Further, it has been discovered that by separating the monobed into discreet segments for separate passage of different aqueous streams, further beneficial results can be achieved. It has also been discovered that dividing the monobed, or segments of the monobed, into separate layers through which the aqueous solution passes, including one or more layers of unmodified ion exchange material, modified ion exchange material and/or a mixture of each, can serve to refine the desired results to be achieved by the particular oxidation or reduction reaction.

The present invention is, therefore, directed at an improved packed bed electrolytic process and apparatus, which allows for better control of the oxidation or reduction process in -3- SUBSTITUTE SHEET (RULE 26) WO 01/78879 PCT/USOO/08732 aqueous solutions, especially dilute aqueous solutions, and to better customize the properties of the final aqueous solution. The invention utilizes an electrolytic reactor comprising an anode, a cathode, and a packed bed of ion exchange material provided between the anode and cathode.

The anode and cathode chambers may be separated by one or more ion exchange membranes or diaphragms for certain applications, but a continuous cationic pathway must exist to the anode for improved oxidation to occur, and a continuous anionic pathway must exist to the cathode for improved reduction to occur. The packed bed may, if desired, contain other species interspersed in the packed bed to perform functions other than oxidation or reduction. If one or more ion exchange membranes are used to separate the anode and/or cathode chambers, each membrane may or may not be made of modified ion exchange material.

In accordance with the present invention, at least some of the ion exchange material in the monobed must have a portion of its ion exchange sites converted to semiconductor junctions as taught in the Sampson '816 and '850 patents. However, unmodified ion exchange material of the same ionic charge as the modified material is included in the monobed. Preferably, the anode and cathode are constructed of materials that allow either to act as an anode or a cathode, which is a practice well known to those skilled in the art of electrochemistry. An aqueous solution containing an inorganic or organic species to be treated is passed through the packed bed electrolytic reactor, and a direct current is applied.

Further, in accordance with this invention, the monobed of unmodified ion exchange material and modified ion exchange material, is packed between the primary electrode and either an oppositely charged ion exchange segment or membrane or the counter electrode such that a continuous ionic pathway exists through the monobed to the primary electrode. The ion exchange material in the monobed can be a combination of various physical forms, such as a combination of beads and membranes, so long as they are of the same charge. For oxidation, the monobed of unmodified cation exchange beads, modified cation exchange beads, and unmodified or modified cation exchange membranes would be in direct contact with the anode, and the cathode chamber may or may not contain ion exchange material. If the cathode chamber contains cation exchange material so as to form a continuous cationic pathway from the cathode to the anode, the cathode chamber becomes a part of the monobed. For reduction, a monobed of unmodified anion exchange beads, modified anion exchange beads, and unmodified or modified anion exchange membranes would be in direct contact with the cathode, and the anode chamber may or may not contain ion exchange material. If the anode chamber contains anion exchange material so as to form a continuous anionic pathway from the anode to the cathode, the anode chamber becomes a part of the monobed. In addition, it is possible under certain circumstances -4- SUBSTITUTE SHEET (RULE 26) WO 01/78879 PCT/US00/08732 to include some quantities of the opposite ion exchange material, or other materials which do not transfer ions, in the otherwise monobed to achieve a particular result. Determining an appropriate additional material and its concentration to achieve a particular result is considered within the skill of those knowledgeable in this field.

Also, in accordance with the present invention, the monobed can be divided into segments by unmodified or modified ion exchange membranes. Each of the segments can contain unmodified or modified ion exchange material, or a combination of both, or no material if adjacent the counter electrode, the cathode for oxidation or the anode for reduction. One or more aqueous solutions are then separately and/or sequentially passed through each of the segments during the oxidation or reduction process.

Lastly, in accordance with the present invention, the monobed, or any particular segment of the monobed, can be formed into layers through which the aqueous solution to be treated sequentially passes during the electrolytic reaction. Each layer can comprise unmodified ion exchange material or modified ion exchange material, or a mixture of both. The design of the layers and the selection of the unmodified and modified ion exchange material to be included in each layer should be selected to best achieve the desired oxidation or reduction conversion and final characteristics for the exiting solution.

It has been found that the present invention is particularly useful in controlling the oxidation of chlorite ion to chlorine dioxide. When oxidizing chlorite ion to chlorine dioxide, it is difficult to prevent the further oxidation of chlorine dioxide to chlorate, an undesirable byproduct. Typically, as the pH of the solution containing the chlorite ion rises, the chemistry favors the further oxidation to chlorate. It is, therefore, advantageous when oxidizing chlorite ion to keep the pH low and to keep the solution away from the anode, where oxidation is not easily controlled.

By separating the monobed into segments by an ion exchange membrane or membranes, separating at least one segment from the anode and passing the chlorite aqueous solution through the segment separated from the anode, the desired conversion to chlorine dioxide can be achieved.

Further, if the monobed or monobed segment through which the chlorite solution passes is properly layered, the layers can ensure a lower pH where the oxidation occurs, thus producing a better conversion to chlorine dioxide.

It has also been discovered that a similar phenomenon exists concerning iodide ion oxidation to iodine. Unlike chlorine dioxide chemistry, where shifting the pH of the chlorite solution can generate chlorine dioxide without direct oxidation (although only 80% conversion can be achieved), iodine formation requires direct oxidation. However, as the pH of iodine goes SUBSTITUTE SHEET (RULE 26) WO 01/78879 PCT/USOO/08732 down, 12 dominates the product. As the pH of the iodine goes up, HOI dominates the product.

12 is considered a better bactericide, whereas HOI is considered a better virucide. By creating segments within the monobed, the pH can be varied, and the desired iodine species can be favored. In addition, iodine can be further oxidized to iodate. It has been found that by isolating the solution to be oxidized from the anode, byproduct formation can be reduced.

It is, therefore, an object of this invention to provide a process and apparatus for better controlling the electrolytic oxidation or reduction of an inorganic or organic species, especially in dilute aqueous solutions.

A further object of the present invention is to provide a process and apparatus, in which the monobed includes both the particulate component and the separating membrane to better control the oxidation or reduction of an inorganic or organic species, especially in dilute aqueous solutions.

A still further object of the present invention is to provide a process and apparatus, which includes a monobed of particulate and one or more membranes divided into segments in order to better control the oxidation or reduction of an inorganic or organic species, especially in dilute aqueous solutions.

Yet a further object of the present invention is to provide a process and apparatus in which the monobed contains different layers of modified and unmodified ion exchange materials to better control the oxidation or reduction of an inorganic or organic species, especially in dilute aqueous solutions.

Another object of the present invention is to provide a process and apparatus, which includes a monobed of various physical forms containing one or more additional ingredients in the otherwise monobed, to achieve a particular result or results beyond oxidation or reduction.

A final object of the present invention is to control the pH of the aqueous product stream containing the species in its oxidized or reduced form to achieve a product stream with the desired properties.

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 Figure 1 shows a cross-sectional view illustrating a packed bed electrolytic reactor in accordance with the present invention.

-6- SUBSTITUTE SHEET (RULE 26) WO 01/78879 PCT/US00/08732 Figure 2 shows a cross-sectional view illustrating another packed bed electrolytic reactor in accordance with the present invention.

Figure 3 shows a cross-sectional view illustrating a further packed bed electrolytic reactor in accordance with the present invention.

Figure 4 shows a cross-sectional view illustrating still another packed bed electrolytic reactor in accordance with the present invention.

Figure 5 is a graph showing iodine concentration versus time produced by oxidation of an aqueous iodide solution by a process in accordance with the present invention utilizing a monobed of cation exchange material in direct contact with the anode, with the monobed divided into segments including the cathode chamber.

Figure 6 is a graph showing iodine concentration versus current produced by oxidation of an aqueous iodide solution by a process in accordance with the present invention utilizing a monobed of cation exchange material in direct contact with the anode, with the monobed divided into segments, including the cathode chamber, and a portion of the segments is present in layers.

Figure 7 is a graph showing iodine concentration versus current produced by oxidation of an aqueous iodide solution by a process in accordance with the present invention utilizing a monobed of cation exchange material in direct contact with the anode with the monobed divided into segments, including the cathode chamber. The graph shows the iodine concentration when a portion of the monobed exists as an unmodified cation exchange membrane and when a portion of the monobed exists as a modified cation exchange membrane.

Figure 8 is a graph showing chlorine dioxide concentration versus time produced by oxidation of an aqueous chlorite solution by a process in accordance with the present invention utilizing a monobed of cation exchange material with the monobed divided into segments, including the cathode chamber, and a portion of the segments is present in layers.

Figure 9 is a graph showing hydrogen peroxide concentration versus time at different electric currents produced by reduction of an aqueous hydrogen peroxide solution by a process in accordance with the present invention utilizing a monobed of anion exchange material in direct contact with the cathode with the monobed divided into segments, where the anode chamber does not contain anion exchange material and remains a distinct anode chamber.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to Figure 1, there is shown a cross-sectional view illustrating a basic packed bed electrolytic reactor 10 of the present invention. The electrolytic reactor 10 includes an anode 11 and a cathode 12. Interposed between the anode 11 and the cathode 12 exists a -7- SUBSTITUTE SHEET (RULE 26) WO 01/78879 PCT/USOO/08732 monobed 16 of cation exchange material in segments. For oxidation to occur, it is necessary for the monobed 16 of cation exchange material to be in direct contact with the anode 11. The monobed 16 consists of two segments: a particulate cation exchange material 14 and a cation exchange membrane 13. The cation exchange material 14 must be modified cation exchange material or a mixture of modified and unmodified cation exchange material. The cation exchange membrane 13 can be modified or unmodified as part of the monobed 16. The cation exchange material 14 may be layered, if desired, such as in three equal layers, for example. The bottom layer would be unmodified cation exchange material, the middle layer would be an equal mixture of modified and unmodified cation exchange material, and the top layer would be modified cation exchange material.

It is optional whether or not ion exchange material is present in the cathode chamber 17.

If the cathode chamber 17 contains ion exchange material, such as particulate ion exchange material 15, as shown in Figure 1, and that ion exchange material is cation exchange material, the cathode chamber 17 becomes a segment of the monobed 16. The cation exchange material in cathode chamber 17 may be modified, unmodified, or a combination to achieve certain results.

An additive or additives may also be interspersed within any of the cation exchange materials 14 and 15 to achieve certain results.

The dilute aqueous solution containing the species to be oxidized passes upwardly through the monobed 16 while the electric current flows between the anode and the cathode. The aqueous solution to be treated can also pass simultaneously or sequentially through the cathode chamber 17 if part of the monobed 16 or, alternatively, a separate flushing solution can pass through the cathode chamber 17 if it is not part of the monobed 16.

Referring now to Figure 2, there is shown a cross-sectional view illustrating a basic packed bed electrolytic reactor 20 of the present invention. The electrolytic reactor 20 includes an anode 21 and a cathode 22. Interposed between the anode 21 and the cathode 22 exists a monobed 26 of anion exchange material in segments. For reduction to occur, it is necessary for the monobed 26 of anion exchange material to be in direct contact with the cathode 22. The monobed 26 consists of two segments: a particulate anion exchange material 24 and an anion exchange membrane 23. The anion exchange material 24 must be a modified anion exchange material or a mixture of a modified and an unmodified anion exchange material. The anion exchange membrane 23 may be modified or unmodified. The anion exchange material 25 may be layered, if desired, such as in three equal layers, for example. The bottom layer would be unmodified anion exchange material, the middle layer would be an equal mixture of modified and -8- SUBSTITUTE SHEET (RULE 26) WO 01/78879 PCT/USOO/08732 unmodified anion exchange material, and the top layer would be modified anion exchange material.

It is optional whether or not ion exchange material is present in the anode chamber 27.

If the anode chamber 27 contains ion exchange material, such as particulate ion exchange material 25, as shown in Figure 2, and that ion exchange material is anion exchange material, the anode chamber 27 becomes a segment of the monobed 26. The anion exchange material in anode chamber 27 may be modified, unmodified, or a combination to achieve certain results. An additive or additives may also be interspersed within any of the anion exchange materials 24 and to achieve certain results.

The dilute aqueous solution containing the species to be oxidized passes upwardly through the monobed 26 while the electric current flows between the anode and the cathode. The aqueous solution to be treated can also pass simultaneously or sequentially through the anode chamber 27 if part of the monobed 26 or, alternatively, a separate flushing solution can pass through the anode chamber 27 if it is not part of the monobed 26.

Referring now to Figure 3, there is shown a cross-sectional view illustrating a basic packed bed electrolytic reactor 100 of the present invention. The electrolytic reactor 100 includes an anode 101 and a cathode 102. Interposed between the anode 101 and the cathode 102 exists a monobed 116 of cation exchange material divided into segments. For oxidation to occur, it is necessary for the monobed 116 of cation exchange material to be in direct contact with the anode 101. The monobed 116 consists of four segments: a particulate cation exchange material 110, a cation exchange membrane 104, a particulate cation exchange material 108, and a cation exchange membrane 106.

It is optional whether or not ion exchange material is present in the cathode chamber 117.

If the cathode chamber 117 contains ion exchange material, such as particulate ion exchange material 112, as shown in Figure 3, and that ion exchange material is cation exchange material, the cathode chamber 117 becomes a segment of the monobed 116. The cation exchange material of each segment may be modified, unmodified, or a combination to achieve certain results, but sufficient modified cation exchange material must be present in the monobed to achieve the desired oxidation. Where the particulate cation exchange materials 108, 110 or 112 include a combination of modified and unmodified cation exchange material, such material can be in layers, depending upon the final result to be achieved. For example, each particulate segment could be divided into three equal layers, with the lower layer comprising unmodified resin, the middle layer comprising a mixture of the modified and unmodified resin, and the top layer comprising modified resin. An additive or additives may also be interspersed within any of the -9- SUBSTITUTE SHEET (RULE 26) WO 01/78879 PCT/USOO/08732 cation exchange materials 108, 110 and 112 to achieve certain results. The aqueous solutions which flow upwardly through the monobed segments 108, 110 and 112 can vary depending upon the final results to be achieved, as described in more detail in the examples which follow.

Referring now to Figure 4, there is shown a cross-sectional view illustrating a basic packed bed electrolytic reactor 120 of the present invention. The electrolytic reactor 120 includes an anode 121 and a cathode 122. Interposed between the anode 121 and the cathode 122 exists a monobed 136 of anion exchange material divided into segments. For reduction to occur, it is necessary for the monobed 136 of anion exchange material to be in direct contact with the cathode 122. The monobed 136 consists of four segments: a particulate anion exchange material 132, an anion exchange membrane 126, a particulate anion exchange material 128, and an anion exchange membrane 124.

It is optional whether or not ion exchange material is present in the anode chamber 135.

If the anode chamber 135 contains ion exchange material, such as particulate ion exchange material 130 as shown in Figure 4, and that ion exchange material 130 is anion exchange material, the anode chamber 135 becomes a segment of the monobed 136. The anion exchange material of each segment may be modified, unmodified, or a combination to achieve certain results, but sufficient modified anion exchange material must be present in the monobed to achieve the desired reduction. Where the particulate anion exchange materials 128, 130 or 132 include a combination of modified and unmodified anion exchange material, such material can be in layers, depending upon the final result to be achieved. For example, each particulate segment could be divided into three equal layers, with the lower layer comprising unmodified resin, the middle layer comprising a mixture of the modified and unmodified resin, and the top layer comprising modified resin. An additive or additives may also be interspersed within any of the anion exchange materials 128, 130 and 132 to achieve certain results. The aqueous solutions which flows upwardly through the monobed segments 128, 130 and 132 can vary depending upon the final results to be achieved, as described in more detail in the examples which follow.

While the arrangements of anode, cathode, and packed bed illustrated in Figures 1, 2, 3, and 4 are presently considered preferable, any arrangement in which a sufficient quantity of modified ion exchange material combined with unmodified ion exchange material is packed between the anode and cathode in a conventional electrolytic reactor, or at least one of the chambers of a divided electrolytic reactor, can be used in accordance with this invention. Other embodiments of the invention include, but are not limited to, separation of anolyte and catholyte compartments to control intermixing of gases in solution and provision of any number of packed SUBSTITUTE SHEET (RULE 26) WO 01/78879 PCT/USOO/08732 bed chambers separated by ion exchange membranes or diaphragms placed between the anode and cathode to effect other oxidation, reduction, or displacement reactions. Further, the disinfecting and sterilizing applications taught in the aforesaid four Sampson patents can also be achieved by the process and apparatus of the present invention.

The anode and cathode may be made of any suitable material, based on the intended use of the electrolytic reactor. For example, for halous acid production from a halide solution, the anode may be made of conventional material, such as ruthenium or iridium on titanium, and the cathode may be made of the same material or of stainless steel. Suitable anode and cathode materials are known to those skilled in the art, and selection of a particular anode or cathode material is considered within the skill of those knowledgeable in this field.

DESCRIPTION OF SPECIFIC EXAMPLES For Examples 1 3, the following testing procedures were used to test for iodine, 12. To test for iodine, the DPD Method 8031 of the Hach Company using a Direct Reading Spectrophotometer Model No. DR-2000 for the measurement of iodine (0 7.0 mg/1) was used, except the instrument was blanked with deionized water between each sample. To bring the concentration of iodine within the range of the spectrophotometer, standard dilutions of the concentrated iodine solutions were made using deionized water, as is the common practice.

For Examples 4 5, the following testing procedures were used to test for chlorine dioxide, C10.. To test for chlorine dioxide, the Method 8138 of the Hach Company using a Direct Reading Spectrophotometer Model No. DR-2000 for the measurement of chlorine dioxide (0 700 mg/1) was used. To bring the concentration of iodine within the range of the spectrophotometer, standard dilutions of the concentrated iodine solutions were made using deionized water, as is the common practice.

For Example 6, the following testing procedures were used to test for hydrogen peroxide

H

2 0 2 The solution was tested on a Hach DR 2000 Spectrophotometer using the Ozone test. Not knowing a direct test for hydrogen peroxide, the ozone test was used and the results multiplied by EXAMPLE I OXIDATION OF IODIDE IONS BY USING AN ELECTROLYTIC REACTOR WITH UNMODIFIED AND MANGANESE MODIFIED CATION EXCHANGE MATERIAL A potassium iodide feed solution was prepared by adding potassium iodide salt to deionized water such that the final concentration of iodide approximated 300 mg/ iodide. A -11- SUBSTITUTE SHEET (RULE 26) WO 01/78879 PCT/USOO/08732 continuous stream of the 300 mg/i iodide feed solution was passed through a packed bed electrolytic reactor having a structure as illustrated in Figure 3 and described above in connection therewith.

In this example, segment 108 contained modified inorganic cation exchange material having approximately 15% of its transfer sites converted to semiconductor junctions with manganese as taught in the Sampson '816 patent. Segment 110 contained unmodified organic cation exchange material and the cathode chamber 117 also contained unmodified organic cation exchange material, such that the cathode chamber 117 acted as a segment of the monobed 116.

The cation exchange membranes 104 and 106 were unmodified in this example.

The iodide solution was passed through the reactor from bottom to top through segment 108 such that the iodide solution had a flow rate of about 150 mi/min through segment 108 of the electrolytic reactor. Softened, dechlorinated tap water was passed upwardly through segment and the cathode chamber 117 independently such that the flow rates through each segment and 117 was approximately 50 mllmin. Wh-ile passing the iodide solution through segment 108 and softened dechlorinated tap water through segments 110 and 117 of the packed bed electrolytic reactor, a controlled current of 2.0 Amps was applied to the anode and cathode in accordance with the Sampson '816 patent.

The results of the electrolytic process in Example 1 are shown in Figure 5. Figure shows the total iodine concentration (ing/l) of the exiting solution versus time. As shown therein, oxidation of iodide ions occurs when the iodide solution to be oxidized is isolated from the anode by passing the solution through one of the segments of the monobed, but not other segments of the monobed. It is also shown that the segments of the monobed may consist of unmodified and modified cation exchange material for the oxidation of iodide to iodine. Iodine is generated from iodide by the following oxidation reaction: 2 1- -2 e- 12 EXAMPLE12 OXIDATION OF IODIDE IONS BY USING AN ELECTROLYTIC REACTOR WITH UNMODIFIED AND PLATINUM MODIFIED CATION EXCHANGE MATERIAL, SOME EXISTING IN LAYERS A potassium iodide feed solution was prepared by adding potassium iodide salt to deionized water such that the final concentration of iodide approximated 300 mg/I iodide. A continuous stream of the 300 mg/I iodide feed solution was passed through a packed bed -12- SUBSTITUTE SHEET (RULE 26) WO 01/78879 PCT/USOO/08732 electrolytic reactor having a structure as illustrated in Figure 3 and described above in connection therewith.

In this example, segment 108 contained layers in equal thirds of unmodified organic cation exchange material and modified inorganic cation exchange material having approximately 20% of its transfer sites converted to semiconductor junctions with platinum as taught in the Sampson '816 patent. The bottom layer consisted of 100% unmodified organic cation exchange beads. The middle layer contained a mixture of 50% unmodified organic cation exchange beads and 50% modified inorganic cation exchange particles. The top layer consisted of 100% modified inorganic cation exchange particles. Segment 110 contained unmodified organic cation exchange material, and the cathode chamber 117 contained unmodified organic cation exchange material such that the cathode chamber 117 acted as a segment of the monobed 116. The cation exchange membranes 104 and 106 were unmodified in this example.

The iodide solution was passed through the reactor from bottom to top through the layers of segment 108 such that the iodide solution had a flow rate of about 150 ml/min through segment 108 of the electrolytic reactor. Softened dechlorinated tap water was passed upwardly through segment 110 and cathode chamber 117 independently such that the flow rate through each segment 110 and 117 was approximately 50 ml/min. While passing the iodide solution through segment 108 and softened dechlorinated tap water through segments 110 and 117 of the packed bed electrolytic reactor, a controlled current of 2.0 Amps, 2.25 Amps, 2.45 Amps, and 2.6 Amps was applied to the anode and cathode in accordance with the Sampson '816 patent.

The results of the electrolytic process in Example 2 are shown in Figure 6. Figure 6 shows the total iodine concentration (mg/1) of the exiting solution versus current. As shown therein, oxidation of iodide ions occurs when the iodide solution to be oxidized is isolated from the anode by passing the solution through one of the segments of the monobed, but not other segments of the monobed. It is also shown that the segments of the monobed may consist of unmodified and modified cation exchange material for the oxidation of iodide to iodine and that the segments may contain layers of unmodified and modified cation exchange material. In this example, as the current increases, so does the oxidation of iodide, thus increasing the concentration of iodine in the product. Iodine is generated from iodide by the same oxidation reaction set forth previously.

EXAMPLE 3 OXIDATION OF IODIDE IONS BY USING AN ELECTROLYTIC REACTOR WITH UNMODIFIED AND PLATINUM MODIFIED CATION EXCHANGE MATERIAL, SOME EXISTING IN MIXTURES -13- SUBSTITUTE SHEET (RULE 26) WO 01/78879 PCT/USOO/08732 A potassium iodide feed solution was prepared for procedures and below by adding potassium iodide salt to deionized water such that the final concentration of iodide approximated 300 mg/ iodide.

A continuous stream of the 300 mg/1 iodide feed solution was passed through a packed bed electrolytic reactor having a structure as illustrated in Figure 3 and described above in connection therewith. In this example, segment 108 contained a mixture of 50% unmodified organic cation exchange material and 50% modified inorganic cation exchange material having approximately 20% of its transfer sites converted to semiconductor junctions with platinum as taught in the Sampson '816 patent. Segment 110 contained a 50- 50 mixture of the unmodified organic and modified inorganic cation exchange material, and the cathode chamber 117 contained unmodified organic cation exchange material, such that the cathode chamber 117 acted as a segment of the monobed 116. The cation exchange membranes 104 and 106 were unmodified in this example.

The iodide solution was passed from bottom to top through segment 108 of the reactor such that the iodide solution had a flow rate of about 150 ml/min through the segment 108.

Softened dechlorinated tap water was passed upwardly through segment 110 and cathode chamber 117 independently such that the flow rate through each segment 110 and 117 was approximately 50 ml/min. While passing the iodide solution through segment 108 and softened dechlorinated tap water through segments 110 and 117 of the packed bed electrolytic reactor, a controlled current of 1.0 Amps was applied to the anode and cathode in accordance with the Sampson '816 patent.

The procedure of Example 3(A) above was repeated, with the exception that the cation exchange membrane 104 was modified such that approximately 20% of its transfer sites were converted to semiconductor junctions as taught in the Sampson '850 patent.

The results of the electrolytic process in procedures 3(A) and 3(B) above are shown in Figure 7. Figure 7 shows the total iodine concentration (mg/l) of the exiting solution versus time.

As shown therein, oxidation of iodide ions occurs when the iodide solution to be oxidized is isolated from the anode by passing the solution through one of the segments of the monobed, but not other segments of the monobed. It is also shown that the segments of the monobed may consist of unmodified and modified cation exchange material for the oxidation of iodide to iodine. In this example, it is clear that when a continuous path of modified cation exchange material exists between the segment containing the iodide solution to be oxidized and the anode, enhanced oxidation occurs. Iodine is generated from iodide by the same oxidation reaction set forth previously.

-14- SUBSTITUTE SHEET (RULE 26) WO 01/78879 PCT/USOO/08732 EXAMPLE 4 OXIDATION OF CHLORITE IONS BY USING AN ELECTROLYTIC REACTOR WITH UNMODIFIED AND PLATINUM MODIFIED CATION EXCHANGE MATERIAL A sodium chlorite feed solution was prepared for procedures and below by adding sodium chlorite salt to softened dechlorinated tap water such that the final concentration of chlorite approximated 750 mg/1 chlorite.

A continuous stream of the 750 mg/1 chlorite feed solution was passed through a packed bed electrolytic reactor having a structure as illustrated in Figure 1 and described above in connection therewith. In this example, segment 14 contained modified inorganic cation exchange material having approximately 20% of its transfer sites converted to semiconductor junctions with platinum as taught in the Sampson '816 patent. The cathode chamber 15 contained unmodified organic cation exchange material, such that the cathode chamber 15 acted as a segment of the monobed 16. The cation exchange membrane 13 was unmodified in this example.

The chlorite solution was passed from bottom to top through segment 14 of the electrolytic reactor such that the chlorite solution had a flow rate of about 150 ml/min through segment 14. Softened dechlorinated tap water was passed upwardly through the cathode chamber such that the flow rate through the segment 15 was approximately 50 ml/min. While passing the chlorite solution through segment 14 and softened dechlorinated tap water through segment 15 of the packed bed electrolytic reactor, a controlled current of 2.0 Amps was applied to the anode and cathode in accordance with the Sampson '816 patent.

A continuous stream of the 750 mg/1 chlorite feed solution was passed through a packed bed electrolytic reactor having a structure as illustrated in Figure 3 and described above in connection therewith. In this example, both segments 110 and 108 contained modified inorganic cation exchange material having approximately 20% of its transfer sites converted to semiconductor junctions with platinum as taught in the Sampson '816 patent. The cathode chamber 117 contained unmodified organic cation exchange material, such that the cathode chamber 117 acted as a segment of the monobed 116. The cation exchange membranes 104 and 106 were unmodified in this example.

The chlorite solution was passed from bottom to top first through segment 110 and second through segment 108 of the electrolytic reactor such that the chlorite solution had a flow rate through each of the segments 110 and 108 of about 150 ml/min. Softened dechlorinated tap water was passed upwardly through the cathode chamber 117 such that the flow rate was approximately ml/min. While passing the chlorite solution through segments 110 and 108 and softened dechlorinated tap water through segment 117 of the packed bed electrolytic reactor, a controlled SUBSTITUTE SHEET (RULE 26) WO 01/78879 PCT/US00/08732 current of 2.0 Amps was applied to the anode and cathode in accordance with the Sampson '816 patent.

A continuous stream of softened dechlorinated tap water was passed through a packed bed electrolytic reactor having a structure as illustrated in Figure 3 and described above in connection therewith. The softened dechlorinated tap water was passed through the reactor from bottom to top through segment 110 such that the softened dechlorinated tap water had a flowrate of about 150 ml/min through segment 110 of the electrolytic reactor. The softened dechlorinated tap water exiting segment 110 was blended with a concentrated sodium chlorite solution such that the resulting blended solution had a final concentration of 750 mg/1 chlorite.

A continuous stream of the blended 750 mg/1 chlorite solution was passed upwardly through segment 108 such that the chlorite solution had a flowrate of about 150 ml/min through segment 108 of the electrolytic reactor. In this example, both segments 110 and 108 contained modified inorganic cation exchange material having approximately 20% of its transfer sites converted to semiconductor junctions with platinum as taught in the Sampson '816 patent. The cathode chamber 117 contained unmodified organic cation exchange material, such that the cathode chamber 117 acted as a segment of the monobed 116. The cation exchange membranes 104 and 106 were unmodified in this example.

Softened dechlorinated tap water was also passed independently upwardly through cathode chamber 117 such that the flow rate through the cathode chamber segment 117 was approximately 50 ml/min. While passing the softened dechlorinated tap water through segment 110, the chlorite solution through segment 108, and softened dechlorinated tap water through segment 117 of the packed bed electrolytic reactor, a controlled current of 2.0 Amps was applied to the anode and cathode in accordance with the Sampson '816 patent.

The results of the electrolytic process in procedures and are shown in Chart 1 below.

CHART 1 pH Conv Example 4(A) 2.79 43 Example 4(B) 2.94 58 Example 4(C) 5.56 88 Chart 1 shows the pH of the chlorine dioxide product stream and the percent conversion of the chlorite feed to chlorine dioxide product. The chemistry of chlorine dioxide is complex and -16- SUBSTITUTE SHEET (RULE 26) WO 01/78879 PCT/USOO/08732 cannot be ignored for this example. As the pH of the chlorite solution decreases, the following reaction occurs, and chlorine dioxide is liberated: NaC10 2 4 H 4 C10 2 NaCI 4 Na 2 However, at theoretical reaction completion, there can only exist 80% conversion of the chlorite ion to chlorine dioxide. This conversion is sometimes referred to as the maximum possible yield. In order for conversion percentages of greater than 80% to theoretically exist, oxidation of the chlorite ion must occur by the following overall net electrochemical reaction: C102- e C10 2 At theoretical reaction completion, 100% conversion of the chlorite ion to chlorine dioxide is possible. However, it is well known that electrochemical oxidation of the chlorite ion will result in high concentrations of chlorate, the least desirable byproduct of chlorine dioxide generation, due to the further oxidation of the chlorine dioxide to chlorate by the following reaction: 2 e When uncontrolled oxidation of chlorite ion occurs, and chlorate is formed, the resultant solution contains a lower concentration of chlorine dioxide than would be expected. Due to the complexity of chlorine dioxide chemistry, the oxidation of the chlorite ion is difficult to control.

All three reactions listed above occur simultaneously in an uncontrolled oxidative acidic environment.

It is clear from the results in this example that the oxidation of chlorite ion can be controlled by the utilization of segments within the monobed of cation exchange material in the packed bed electrolytic reactor in accordance with the present invention.

EXAMPLE 5 OXIDATION OF CHLORITE IONS BY USING AN ELECTROLYTIC REACTOR WITH UNMODIFIED AND PLATINUM MODIFIED CATION EXCHANGE MATERIAL, SOME EXISTING IN LAYERS A continuous stream of softened dechlorinated tap water was passed through a packed bed electrolytic reactor having a structure illustrated in Figure 3 and described above in -17- SUBSTITUTE SHEET (RULE 26) WO 01/78879 PCT/US00/08732 connection therewith. The softened dechlorinated tap water was passed through the reactor from bottom to top through segment 110 such that the softened dechlorinated tap water had a flow rate of about 150 ml/min through segment 110 of the electrolytic reactor. In this example, segment 110 contained unmodified organic cation exchange material. The softened dechlorinated tap water exiting segment 110 was blended with a concentrated sodium chlorite solution such that the resulting blended solution had a final concentration of 750 mg/1 chlorite. A continuous stream of the blended 750 mg/1 chlorite solution was passed through segment 108 such that the chlorite solution had a flow rate of about 150 ml/min through segment 108 of the electrolytic reactor.

In this example, segment 108 contained layers in equal thirds of unmodified organic cation exchange material and modified inorganic cation exchange material having approximately of its transfer sites converted to semiconductor junctions with platinum as taught in the Sampson '816 patent. The bottom layer consisted of 100% unmodified organic cation exchange beads. The middle layer contained a mixture of 50% unmodified organic cation exchange beads and 50% modified inorganic cation exchange particles. The top layer consisted of 100% modified inorganic cation exchange particles. The cathode chamber 117 contained unmodified organic cation exchange material, such that the cathode chamber 117 acted as a segment of the monobed 116. The cation exchange membranes 104 and 106 were unmodified in this example.

Softened dechlorinated tap water was passed through the cathode chamber 117 such that the flow rate through the cathode chamber segment 117 was approximately 50 ml/min. While passing the softened dechlorinated tap water through segment 110, the chlorite solution through segment 108, and softened dechlorinated tap water through segment 117 of the packed bed electrolytic reactor, a controlled current of 4.0 Amps was applied to the anode and cathode in accordance with the Sampson '816 patent.

The procedure described in Example 5(A) above was repeated, with the exception that the softened dechlorinated tap water exiting segment 110 was sent to drain. A new softened dechlorinated tap water feed stream was blended with the concentrated sodium chlorite solution such that the resulting blended solution had a final concentration of 750 mg/1 chlorite. A continuous stream of the 750 mg/1 chlorite solution was passed through segment 108 such that the chlorite solution had a flow rate of about 150 ml/min through segment 108 of the electrolytic reactor.

The results of the electrolytic process in procedures 5(A) and 5(B) are shown in Chart 2 below.

-18- SUBSTITUTE SHEET (RULE 26) WO 01/78879 PCT/US00/08732 CHART 2 Product Blended pH pH Conv Example 5(A) 2.80 11.78 82 Example 5(B) 2.66 11.52 82 Chart 2 shows the pH of the chlorine dioxide product stream, the pH of all streams blended together, and the percent conversion of the chlorite feed to chlorine dioxide product.

As explained n connection with Example 4, the chemistry of chlorine dioxide is complex and cannot be ignored for this example as well. It is clear from this example that oxidation of chlorite ion occurs within the layered segments of the monobed of cation exchange material in the packed bed electrolytic reactor when the chlorite solution is isolated from the anode. It is also clear from this example that the pH of the final solution can be controlled to achieve a desired result.

EXAMPLE 6 OXIDATION OF CHLORITE IONS BY USING AN ELECTROLYTIC REACTOR WITH UNMODIFIED AND PLATINUM MODIFIED CATION EXCHANGE MATERIAL, SOME EXISTING IN LAYERS, IN A PRODUCTION SYSTEM An electrochemical chlorine dioxide generator, System 1000, manufactured and sold by Halox Technologies Corporation, operated as prescribed by the Company, was used in the following example. The Halox System 1000 generator is a packed bed electrolytic reactor having a structure as illustrated in Figure 3 and described above in connection therewith.

A tap water feed, an 8.2% sodium chlorite solution, a drain line, and power were provided for the unit's operation. Within the unit, the tap water feed was filtered and softened. A continuous stream of softened tap water was passed through segment 110 of the reactor from bottom to top such that the softened tap water had a flow rate of about 150 ml/min through segment 110 of the electrolytic reactor. In this example, segment 110 contained unmodified organic cation exchange material. The softened tap water exiting segment 110 was blended with the 8.2% sodium chlorite solution such that the resulting blended solution had a final concentration of approximately 1000 mg/1 chlorite on average over a 7 hour period. A continuous stream of the 1000 mg/1 chlorite solution was passed through segment 108 such that the chlorite solution had a flow rate of about 127 ml/min on average over a 7 hour period through segment 108 of the electrolytic reactor.

In this example, segment 108 contained layers in equal thirds of unmodified organic cation exchange material and modified inorganic cation exchange material having approximately -19- SUBSTITUTE SHEET (RULE 26) WO 01/78879 PCT/USOO/08732 of its transfer sites converted to semiconductor junctions with platinum as taught in the Sampson '816 patent. The bottom layer consisted of 100% unmodified organic cation exchange beads. The middle layer contained a mixture of 50% unmodified organic cation exchange beads and 50% modified inorganic cation exchange particles. The top layer consisted of 100% modified inorganic cation exchange particles. Softened tap water was passed through the cathode chamber 117 containing unmodified organic cation exchange material, such that the cathode chamber 117 acted as a segment of the monobed 116, at a flow rate through the segment 117 of approximately 50 ml/min. The cation exchange membranes 104 and 106 were unmodified in this example. While passing the softened tap water through segment 110, the chlorite solution through segment 108, and softened tap water through segment 117 of the packed bed electrolytic reactor, a controlled current of 4.0 Amps was applied to the anode and cathode in accordance with the Sampson '816 patent.

The results of the electrolytic process in this example are shown in Figure 8. Figure 8 shows the concentration of chlorine dioxide in the product stream versus time. Again, as explained in Example 4, the chemistry of chlorine dioxide is complex and also cannot be ignored for this example. However, the average percent conversion in this example over the 7 hour period is 89%, indicating that controlled oxidation of chlorite ion to chlorine dioxide occurs within the layered segments of the monobed of cation exchange material in the packed bed electrolytic reactor.

EXAMPLE 7 REDUCTION OF HYDROGEN PEROXIDE BY USING AN ELECTROLYTIC REACTOR WITH UNMODIFIED AND SPS MODIFIED ANION EXCHANGE MATERIAL A hydrogen peroxide feed solution was prepared by adding hydrogen peroxide to deionized water such that the final concentration of hydrogen peroxide approximated 35 mg/l hydrogen peroxide.

A continuous stream of the 35 mg/l hydrogen peroxide feed solution was passed through a packed bed electrolytic reactor having a structure as illustrated in Figure 4 and described above in connection therewith. The hydrogen peroxide solution was passed through the reactor from bottom to top through segment 128 such that the hydrogen peroxide solution had a flow rate of about 150 ml/min through segment 128 of the electrolytic reactor. In this example, segment 128 contained modified organic anion exchange material having approximately 20% of its transfer sites converted to semiconductor junctions with SPS 70 as taught in the Sampson '742 patent.

Softened dechlorinated tap water was passed through segment 132, which contained unmodified SUBSTITUTE SHEET (RULE 26) WO 01/78879 PCT/USOO/08732 organic anion exchange material. Softened dechlorinated tap water was also independently passed through the anode chamber 135 which contained unmodified organic cation exchange material such that the anode chamber 135 did not act as a segment of the monobed 136. The flow rate of the tap water through each segment 132 and 135 was approximately 50 ml/min. The anion exchange membranes 126 and 124 were unmodified in this example. While passing the hydrogen peroxide solution through segment 128 and softened dechlorinated tap water through segments 132 and 135 of the packed bed electrolytic reactor, a controlled current of 1.5 Amps and Amps was applied to the anode and cathode in accordance with the Sampson '816 patent.

The results of the electrolytic process in Example 7 are shown in Figure 9. Figure 9 shows the total hydrogen peroxide concentration (mg/1) of the exiting solution versus current.

As shown therein, reduction of hydrogen peroxide occurs when the hydrogen peroxide solution to be reduced is isolated from the cathode by passing the solution through one of the segments of the monobed, but not other segments of the monobed, and where the anode compartment does not act as a segment of the monobed. This example also shows that the segments of the monobed may consist of unmodified and modified anion exchange material for the reduction of hydrogen peroxide.

In order to optimize and/or customize the desired oxidation or reduction reaction, the aqueous solution containing the species to be oxidized or reduced preferably may be pretreated by various means. Some examples of pretreatment, which may be used, but are not always necessary in accordance with this invention, include the following: filtration for clarity; carbon filtration for the removal of undesirable organics; specialized ion exchange of the common salts found in water to the desired salts to form specific oxidized or reduced species; addition of nonoxidizable or non-reducible species to control pH or another function; and addition of desired species to deionized or other high purity waters to form specific oxidized or reduced species.

Other pretreatments may occur to those skilled in the art depending upon the species to be oxidized or reduced, the make-up of the aqueous solution, the nature of the ion exchange material and semiconductor junctions, and other variables.

It is preferred that the ion exchange material be packed tightly in the electrolytic reactor so as to ensure intimate contact between the ion exchange material particles themselves, the ion exchange membranes, and the electrodes, if in contact with one or both electrodes. This intimate contact ensures the highest efficiency of the purification or the conversion, if oxidation or reduction. However, it is contemplated as part of this invention that loose packing of the ion exchange material can be employed in appropriate circumstances. Although not necessarily achieving the highest overall efficiency for the system, there may be circumstances in which -21- SUBSTITUTE SHEET (RULE 26) WO 01/78879 PCT/USOO/08732 loose packing can be employed, since the benefits obtained by the present invention can still be achieved.

While the monobed of the electrolytic process and apparatus of the present invention is preferably, for most applications, a single species, such as all cation exchange material or all anion exchange material, it has been found that variation in the monobed is possible in certain circumstances, and minor amounts of the opposite ion exchange material can be tolerated. In addition, additives can be introduced into the monobed under certain circumstances in order to achieve desired results in the final exit stream from the electrolytic reactor.

Further, the electrolytic process and apparatus of the present invention can be operated in a bipolar fashion as taught by the Sampson '050 patent. However, in order for the electrolytic process and apparatus to be operated in a bipolar fashion, the configuration of the reactor, the monobed and the flow pattern of the aqueous solutions must be symmetrical in order for the process to continue its designed mode of operation when the polarity is reversed.

Although specific examples are given in order to provide an understanding of the concepts of the present invention, any oxidizable or reducible organic or inorganic species can be oxidized or reduced by the present invention. Some examples of oxidizable species include halide salts, organic acids, total organic carbon, bacteria, and inorganic salts. Some examples of reducible species include halous acids, tri halo methane compounds, metallic oxides, phenolic compounds, and peroxygen compounds.

Further, the foregoing descriptions and drawings 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.

-22- SUBSTITUTE SHEET (RULE 26)

Claims (38)

1. What is claimed is: 1. An electrolytic process for oxidizing a species in a aqueous solution, comprising the steps of: passing an aqueous feed solution containing said species to be oxidized through a monobed of cation exchange material interposed between an anode and a cathode; said monobed containing unmodified cation exchange material and modified cation exchange material, and establishing a continuous cationic pathway to said anode; applying a direct current across the anode and cathode; and contacting said feed solution with said bed for a time to cause at least a portion of said species to be oxidized by said monobed so that said aqueous solution contains said species in an oxidized form.
2. 2. A process as defined in claim 1, wherein said modified cation exchange material includes particulate modified cation exchange material.
3. 3. A process as defined in claim 1, wherein said modified cation exchange material includes a modified cation exchange membrane.
4. 4. A process as defined in claim 1, and further including the step of recovering said aqueous solution containing the oxidized species.
5. 5. A process as defined in claim 1 , wherein said continuous cationic pathway to said anode is established by said monobed being in direct contact with said anode.
6. 6. A process as defined in claim 1, wherein said monobed includes an additive without substantially retarding oxidation of said species and diffusion of ions through said monobed.
7. 7. A process as defined in claim 1, wherein said monobed is divided into segments and the step of passing said aqueous feed solution through said monobed includes passing said aqueous feed solution through at least one of said segments.
8. 8. A process as defined in claim 7, wherein at least one of said segments exists in layers of particulate cation exchange material and the step of passing said aqueous feed solution through said monobed includes passing said aqueous feed solution through said layers.
9. 9. A process as defined in claim 1, wherein said cathode chamber contains cation exchange material such that said cathode chamber acts as a segment of the monobed.
10. 10. A process as defined in claim 1 , wherein said cathode chamber contains no cation exchange material such that said cathode chamber does not act as a segment of the monobed.
11. 11. A process as defined in claim 4, wherein the pH of the aqueous stream containing said oxidized species can be controlled to achieve a certain result.
12. 12. An electrolytic process for reducing a species in a aqueous solution, comprising the steps of: passing an aqueous feed solution containing the said species to be reduced through a monobed of anion exchange material interposed between an anode and a cathode; said monobed containing unmodified anion exchange material and modified anion exchange material, and establishing a continuous anionic pathway to said cathode; applying a direct current across the anode and cathode; and contacting said feed solution with said bed for a time to cause at least a portion of said species to be reduced by said monobed so that said aqueous solution contains said species in a reduced form.
13. 13. A process as defined in claim 12, wherein said modified anion exchange material includes particulate modified anion exchange material.
14. 14. A process as defined in claim 12, wherein said modified anion exchange material includes a modified anion exchange membrane.
15. 15. A process as defined in claim 12, and further including the step of recovering said aqueous solution containing said reduced species.
16. 16. A process as defined in claim 12, wherein said continuous anionic pathway to said cathode is established by said monobed being in direct contact with said anode.
17. 17. A process as defined in claim 12, wherein said monobed includes an additive without substantially retarding reduction of said species and diffusion of ions through said monobed.
18. 18. A process as defined in claim 12, wherein said monobed is divided into segments and the step of passing said aqueous feed solution through said monobed includes passing said aqueous feed solution through at least one of said segments.
19. 19. A process as defined in claim 18, wherein at least one of said segments exists in layers of particulate anion exchange material and the step of passing said aqueous feed solution through said monobed includes passing said aqueous feed solution through said layers.
20. 20. A process as defined in claim 12, wherein said anode chamber contains anion exchange material such that said anode chamber acts as a segment of the monobed.
21. 21. A process as defined in claim 12, wherein said anode chamber contains no anion exchange material such that said anode chamber does not act as a segment of the monobed.
22. 22. A process as defined in claim 12, wherein the pH of the aqueous stream containing said reduced species can be controlled to achieve a certain result.
23. 23. An electrolytic reactor for the oxidation of an organic or inorganic species in an aqueous solution which comprises an anode, a cathode and a monobed of cation exchange material between said anode and said cathode such that said cation exchange material is in physical contact with said anode, said monobed of cation exchange material containing unmodified cation exchange material and modified cation exchange material.
24. 24. An electrolytic reactor as defined in claim 23, wherein said monobed of cation exchange material is divided into segments and at least one of said segments is particulate cation exchange material and another of said segments is a cation exchange membrane.
25. 25. An electrolytic reactor as defined in claim 24, wherein said particulate cation exchange material exists in layers in said segment.
26. 26. An electrolytic reactor as defined in claim 25, wherein said layers include three equal layers, a lower layer comprising unmodified cation exchange material, an intermediate layer comprising a mixture of unmodified and modified cation exchange material, and an upper layer comprising modified cation exchange material.
27. 27. An electrolytic reactor for the reduction of an organic or inorganic species in an aqueous solution which comprises an anode, a cathode and a monobed of anion exchange material between said anode and said cathode such that said anion exchange material is in physical contact with said cathode, said monobed of anion exchange material containing unmodified anion exchange material and modified anion exchange material.
28. 28. An electrolytic reactor as defined in claim 27, wherein said monobed of anion exchange material is divided into segments and at least one of said segments is particulate anion exchange material and another of said segments is an anion exchange membrane.
29. 29. An electrolytic reactor as defined in claim 28, wherein said particulate anion exchange material exists in layers in said segment.
30. 30. An electrolytic reactor as defined in claim 29, wherein said layers include three equal layers, a lower layer comprising unmodified anion exchange material, an intermediate layer comprising a mixture of unmodified and modified anion exchange material, and an upper layer comprising modified anion exchange material.
31. 31. An electrolytic process for oxidizing chlorite ions to chlorine dioxide in an aqueous solution by an electrolytic reactor having an anode, a cathode and a monobed of cation exchange material interposed between the anode and the cathode, which process comprises the steps of: dividing said monobed into segments, said segments including at least a first segment comprising particulate cation exchange material in contact with said anode, a second segment comprising a cation exchange membrane separating said first segment from a third segment comprising particulate cation exchange material, at least a portion of which is modified, and a fourth segment comprising a cation exchange membrane separating said third segment from said cathode; applying a direct current across the anode and cathode; passing a flushing solution through said first segment and between said fourth segment and said cathode; and passing said aqueous feed solution containing said chlorite ion upwardly through said third segment for a contact time sufficient to cause at least a portion of said chlorite ion to oxidize to chlorine dioxide.
32. 32. An electrolytic reactor for oxidizing chlorite ion in an aqueous solution to chlorine dioxide, which comprises an anode, a cathode and a monobed of cation exchange material interposed between said anode and said cathode such that said monobed is in direct contact with said anode, said monobed divided into segments including at least a first segment comprising particulate cation exchange material, a second segment comprising a cation exchange membrane separating said first segment from a third segment comprising particulate cation exchange material, at least a portion of which is modified, and a fourth segment comprising a cation exchange membrane separating said third segment from said cathode, means for passing a flushing solution between said second segment and said anode and between said fourth segment and said cathode; and means for passing said aqueous feed solution upwardly through said third segment for a contact time sufficient to cause at least a portion of said chlorite ion to oxidize to chlorine dioxide.
33. 33. An electrolytic reactor as defined in claim 32, wherein said particulate cation exchange material in said third segment exists in three equal layers comprising a lower layer of unmodified cation exchange material, an intermediate layer comprising a mixture of unmodified and modified cation exchange material and an upper layer comprising unmodified cation exchange material.
34. 34. A process as defined in claim 7, wherein the step of passing said aqueous feed solution through said monobed includes passing said aqueous feed solution sequentially through at least two of said segments.
35. 35. A process as defined in claim 18, wherein the step of passing said aqueous feed solution through said monobed includes passing said aqueous feed solution sequentially through at least two of said segments.
36. 36. An electrolytic process for altering a species in an aqueous solution by oxidizing or reducing said species, comprising the steps of: passing an aqueous feed solution containing said species through a monobed of ion exchange material interposed between a primary electrode and a counter electrode of an electrolytic reactor, said ion exchange material having a charge opposite to a charge of said primary electrode; said monobed containing unmodified ion exchange material and modified ion exchange material, and establishing a continuous ionic pathway to said primary electrode, said ionic pathway having a charge the same as said ion exchange material; applying a direct current across the primary electrode and counter electrode; and contacting said feed solution with said monobed for a time to cause at least a portion of said species to be altered by said monobed so that said aqueous solution contains said species in an altered form.
37. 37. A process as defined in claim 36, wherein said direct current across said primary electrode and counter electrode is applied in a bipolar fashion.
38. 38. An electrolytic reactor for the oxidation or reduction of an organic or inorganic species in an aqueous solution which comprises a primary electrode, a counter electrode and a monobed of ion exchange material between said electrodes such that said ion exchange material is in physical contact with said primary electrode, said monobed of ion exchange material containing unmodified ion exchange material and modified ion exchange material.