Water treatment device, water treatment system, and water treatment method

Abstract

This water treatment device, which simultaneously removes an oxidizing agent component and a boron component contained in water to be treated, comprises, between an anode 11 and a cathode 12: a treatment chamber 23 which is partitioned by an anion-exchange membrane 32 disposed on the anode 11 side and a cation-exchange membrane 33 provided on the cathode 12 side, and which is filled with a catalyst having the ability to decompose oxidizing agents; and a pair of concentration chambers 22, 24 which are disposed adjacent to the treatment chamber with the anion-exchange membrane 32 and the cation-exchange membrane 33 interposed therebetween, respectively, and which are filled with an ion-exchange resin. At least some of the ion-exchange resin filling the concentration chambers 22, 24 is a cation-exchange resin. The water to be treated is supplied to the treatment chamber 23, and the oxidizing agent component is removed from the water being treated.

Description

Water treatment device, water treatment system and water treatment method

[0001] The present invention relates to a water treatment device and method for simultaneously removing an oxidant component and a boron component from water to be treated, and a water treatment system equipped with the water treatment device.

[0002] Ultrapure water used in the manufacture of semiconductor devices and the like is produced, for example, by pretreating raw water to obtain filtrate, then treating the filtrate with a reverse osmosis membrane, irradiating the water that passes through the reverse osmosis membrane with ultraviolet light to decompose the organic components in the permeate, and then performing an ion exchange treatment on the water that has passed through the ultraviolet oxidation treatment. In the ultraviolet oxidation treatment, organic components in the water are oxidized to carbonic acid and organic acids, so in order to remove the carbonic acid and organic acids produced in the ultraviolet oxidation treatment, an ion exchange treatment must be performed after the ultraviolet oxidation treatment.

[0003] Hydrogen peroxide is inevitably generated during ultraviolet oxidation treatment. To increase the efficiency of decomposition of organic components during ultraviolet oxidation treatment, hydrogen peroxide is sometimes added to the water to be treated that is supplied to the treatment. Hydrogen peroxide is a strong oxidizing agent that deteriorates the ion exchange resin used in ion exchange treatment and also deteriorates the membrane if membrane treatment is performed after ion exchange treatment. Therefore, it is desirable to remove hydrogen peroxide from the treated water during ultraviolet oxidation treatment. Since oxidizing components other than hydrogen peroxide may also be generated during ultraviolet oxidation treatment, it is also desirable to remove such oxidizing components from the treated water during ultraviolet oxidation treatment. There is also a demand for removing oxidizing components such as hydrogen peroxide from the treated water in fields other than the production of ultrapure water.

[0004] For example, Patent Document 1 discloses a hydrogen peroxide removal device for removing hydrogen peroxide from water to be treated, which includes an anode, a cathode, and a hydrogen peroxide removal chamber disposed between the anode and the cathode and at least partially filled with a metal catalyst capable of decomposing hydrogen peroxide, and in which a DC voltage is applied between the anode and the cathode. In the hydrogen peroxide removal chamber, a metal catalyst made of a platinum group metal, particularly palladium (Pd), is supported on the surface of an ion exchanger, such as an ion exchange resin. Patent Document 2 discloses a water treatment device for decomposing and removing organic matter contained in the water to be treated, which includes a means for adding hydrogen peroxide to the water to be treated, an ultraviolet oxidation device for performing ultraviolet oxidation treatment on the water to which hydrogen peroxide has been added, and a hydrogen peroxide removal device disposed downstream of the ultraviolet oxidation device.

[0005] However, there is a demand for further reduction in the boron content in ultrapure water used in semiconductor device manufacturing and the like. Boron in water is a weak acid component that is difficult to remove by conventional ion exchange treatment, in which the water to be treated is passed through an ion exchange resin. Therefore, attempts have been made to remove boron from the water to be treated using electrodeionization (EDI) devices. An EDI device produces deionized water from the water to be treated by combining electrophoresis and electrodialysis, and at least its deionization compartment is filled with an ion exchange resin. An EDI device has the advantage of eliminating the need for chemical regeneration of the ion exchange resin. However, even with an EDI device, simply filling the deionization compartment with a conventional ion exchange resin may not be sufficient to remove weak acid components such as boron.

[0006] Conventional ion exchange resins are bead- or granular-shaped, with a typical particle size of more than 0.4 mm and less than 1 mm. However, to improve the removal performance of weak acids in EDI devices, it has been proposed to pack the desalination compartment with an ion exchange resin having a smaller particle size. For example, Patent Document 3 discloses packing a single bed of ion exchange resin with an average particle size of 150 to 250 μm into the desalination compartment of an EDI device. Patent Document 4 discloses packing a single bed of ion exchange resin with an average diameter of 0.2 to 0.3 mm into the desalination compartment. Furthermore, Patent Document 5 discloses packing a mixture of ion exchange resin particles having different uniform particle sizes into the desalination compartment in order to reduce the electrical resistance of the desalination compartment. However, even if the removal performance of boron components in an EDI device is improved by packing a small-particle ion exchange resin into the desalination compartment, the boron removal performance may still be insufficient.

[0007] International Publication No. 2021 / 261143 JP 2022-138429 A JP 2016-150304 A JP 2017-176968 A JP 10-258289 A

[0008] The hydrogen peroxide removal devices disclosed in Patent Documents 1 and 2 are structurally similar to EDI devices. These hydrogen peroxide removal devices can be constructed by supporting a catalyst with oxidant-decomposing properties on at least a portion of the ion exchanger packed in the desalination compartment of the EDI device. Therefore, these hydrogen peroxide removal devices can not only remove oxidants such as hydrogen peroxide, but also desalination. Therefore, it is conceivable that such hydrogen peroxide removal devices could be improved to remove boron components simultaneously with the removal of oxidants.

[0009] An object of the present invention is to provide a water treatment device and method for simultaneously removing oxidant components and boron components from water to be treated, and a water treatment system equipped with such a water treatment device.

[0010] One aspect of the water treatment device of the present invention comprises a treatment chamber between an anode and a cathode, partitioned by a pair of ion exchange membranes consisting of a first ion exchange membrane placed on the anode side and a second ion exchange membrane placed on the cathode side, and containing a catalyst having oxidant decomposition ability; and a pair of concentration chambers placed adjacent to the treatment chamber via the first ion exchange membrane and the second ion exchange membrane, respectively, and filled with ion exchange resin, wherein at least a portion of the ion exchange resin filled in the concentration chamber is a cation exchange resin, and water to be treated is supplied to the treatment chamber, and oxidants and boron are removed from the water to be treated.

[0011] A water treatment system according to one embodiment of the present invention comprises an ultraviolet oxidation device and a water treatment device according to one embodiment of the present invention, wherein outlet water from the ultraviolet oxidation device is supplied to a treatment chamber as water to be treated, and at least a portion of the water supplied to a concentration chamber is outlet water from the ultraviolet oxidation device.

[0012] One embodiment of the water treatment method of the present invention is a water treatment method for removing oxidants and boron contained in water to be treated, and includes a treatment step of applying a DC voltage between an anode and a cathode, and passing the water to be treated through a treatment chamber that is partitioned by a first ion exchange membrane on the side facing the anode and by a second ion exchange membrane on the side facing the cathode, and is at least partially filled with a catalyst having oxidant decomposition ability, and a pair of concentration chambers that are arranged adjacent to the treatment chamber via the first ion exchange membrane and the second ion exchange membrane, respectively, and are filled with ion exchange resin, and at least a cation exchange resin is filled in.

[0013] According to the present invention, it is possible to simultaneously remove oxidizing agent components such as hydrogen peroxide and boron components from water to be treated.

[0014] FIG. 1 is a diagram showing a basic aspect of a water treatment device according to the present invention. FIG. 1 is a diagram showing a water treatment device of a first embodiment. FIG. 2 is a diagram explaining leakage of a boron component. FIG. 3 is a diagram showing an example of filling an ion exchange resin in a treatment chamber. FIG. 4 is a diagram showing an example of filling an ion exchange resin in a treatment chamber. FIG. 5 is a diagram showing an example of filling an ion exchange resin in a treatment chamber. FIG. 6 is a diagram showing an example of filling an ion exchange resin in a treatment chamber. FIG. 7 is a diagram showing a water treatment device of a second embodiment. FIG. 8 is a diagram showing another example of a water treatment device of the second embodiment. FIG. 9 is a diagram showing another example of a water treatment device of the second embodiment. FIG. 10 is a flow sheet showing an example of the configuration of a pure water production system. FIG. 11 is a flow sheet showing an example of the configuration of a pure water production system. FIG. 12 is a diagram explaining a water treatment device used in Example 1. FIG. 13 is a diagram explaining a water treatment device used in Example 2. FIG. 14 is a diagram explaining water treatment devices of Comparative Example 1 and Reference Example 3. FIG. 15 is a diagram explaining a water treatment device used in Reference Examples 1 and 2. FIG. 16 is a graph showing the results of Reference Examples 1 to 3. FIG. 17 is a graph showing the amount of palladium supported on recovered ion exchange resin. FIG. 18 is a graph showing the results of Reference Examples 4 and 5.

[0015] FIG. 1 shows a basic embodiment of a water treatment device according to the present invention. The water treatment device 10 shown in FIG. 1 includes at least one treatment chamber 23 between an anode chamber 21 equipped with an anode 11 and a cathode chamber 25 equipped with a cathode 12. The treatment chamber 23 is partitioned by a first ion exchange membrane located on the anode 11 side and a second ion exchange membrane located on the cathode 12 side. The anode chamber 21 and the cathode chamber 25 are collectively referred to as electrode chambers. The treatment chamber 23 is filled with an ion exchanger carrying, at least in part, a catalyst capable of decomposing oxidants. The catalyst capable of decomposing oxidants will be described later. In the example shown in FIG. 1 , the first ion exchange membrane located on the anode 11 side is an anion exchange membrane (AEM) 32, and the second ion exchange membrane located on the cathode 12 side is a cation exchange membrane (CEM) 33. The ion exchanger is typically an ion exchange resin (IER), and in the figure, an ion exchange resin carrying a catalyst having an oxidant decomposing ability is indicated by "Cat. IER."

[0016] 1 , an anode 11 and a cathode 12 face each other, and an anode chamber 21, a concentration chamber 22, a treatment chamber 23, a concentration chamber 24, and a cathode chamber 25 are arranged between the anode 11 and the cathode 12 in this order from the anode 11 side. The anode chamber 21 and the concentration chamber 22 are separated by a cation exchange membrane 31, the concentration chamber 22 and the treatment chamber 23 are separated by an anion exchange membrane 32, the treatment chamber 23 and the concentration chamber 24 are separated by a cation exchange membrane 33, and the concentration chamber 24 and the cathode chamber 25 are separated by an anion exchange membrane 34. The water treatment device 10 shown in FIG. 1 is structurally equivalent to an EDI device, and the deionization chamber of the EDI device is used as the treatment chamber 23 of the water treatment device 10, and the treatment chamber 23 is filled with an ion exchanger at least partially carrying a catalyst having oxidant-decomposing ability. In the water treatment device 10, the treatment chamber 23 receives the water to be treated and decomposes and removes oxidizing components such as hydrogen peroxide in the water, and also removes weak acid components such as carbon dioxide and boron. In order to remove the weak acid components, at least a portion of the ion exchanger packed in the treatment chamber 23 must be an anion exchanger.

[0017] The catalyst capable of decomposing oxidants supported on the ion exchanger in the treatment chamber 23 can be, for example, a metal catalyst capable of decomposing hydrogen peroxide. Alternatively, enzymes (e.g., catalase and peroxidase) capable of decomposing dissolved oxygen and oxidants such as hydrogen peroxide can also be used. Examples of metal catalysts capable of decomposing hydrogen peroxide include platinum group metal catalysts such as palladium and platinum, as well as iron, manganese, nickel, gold, silver, copper, chromium, aluminum, and compounds thereof. Metal oxide catalysts such as manganese dioxide, cobalt oxide, titanium oxide, and zinc oxide can also be used as metal catalysts capable of decomposing hydrogen peroxide. Among these, platinum group metal catalysts are more preferably used as catalysts capable of decomposing oxidants because they exhibit high catalytic activity in the decomposition of oxide components such as hydrogen peroxide. A platinum group metal catalyst is a catalyst containing one or more metals selected from ruthenium, rhodium, palladium, osmium, iridium, and platinum. The platinum group metal catalyst may contain any one of these metal elements alone or a combination of two or more of them. Among these, platinum, palladium, and platinum / palladium alloys have high catalytic activity and are particularly suitable for use as platinum group metal catalysts. In the following description, the catalyst having the ability to decompose oxidants will be described as a platinum group metal catalyst.

[0018] Ion exchangers supporting a platinum group metal catalyst can be produced by supporting platinum group metal particles on the ion exchanger using known methods. For example, one method involves immersing an anion exchanger in an aqueous solution of palladium chloride in hydrochloric acid, adsorbing the chloropalladate anions onto the anion exchanger via ion exchange, and then contacting the anion exchanger with a reducing agent to support palladium metal nanoparticles onto the anion exchanger. Another method involves filling a column with the anion exchanger, passing an aqueous solution of palladium chloride in hydrochloric acid through the column to adsorb the chloropalladate anions onto the anion exchanger via ion exchange, and then passing a reducing agent through the column to support palladium metal nanoparticles onto the anion exchanger. The reducing agent used in these methods is not particularly limited, and examples include alcohols such as methanol, ethanol, and isopropanol; carboxylic acids such as formic acid, oxalic acid, citric acid, and ascorbic acid; ketones such as acetone and methyl ethyl ketone; aldehydes such as formaldehyde and acetaldehyde; sodium borohydride; and hydrazine.

[0019] The water treatment device 10 is configured such that concentrate chamber feed water is supplied to the concentrate chambers 22 and 24, electrode chamber feed water is supplied to the cathode chamber 25, and outlet water from the cathode chamber 25 is supplied to the anode chamber 21. The electrode chamber feed water may be supplied to the anode chamber 21 independently of the cathode chamber 25. The anode chamber 21, concentrate chambers 22 and 24, and cathode chamber 25 are each filled with an ion exchanger that does not support a catalyst. The ion exchanger may be either an anion exchanger or a cation exchanger, or both. When both anion exchanger and cation exchanger are used, the ion exchanger may be packed in a mixed bed configuration in which an anion exchanger and a cation exchanger are mixed and packed, or in a multi-layer bed configuration in which an anion exchanger layer and a cation exchanger layer are packed separately. As described below, in order to improve the boron removal performance in the treatment chamber 23, at least a portion of the ion exchanger packed in the concentrate chambers 22 and 24 must be a cation exchanger.

[0020] Although the concentration chambers 22, 24 may be filled with only cation exchangers, when the water to be treated or the water supplied to the concentration chambers 22, 24 contains, for example, 0.05 to 0.1 mg / L of hardness components such as calcium or magnesium, an increase in the applied voltage in the water treatment device 10 and a deterioration in the quality of the treated water are likely to occur, and therefore it is preferable to fill the concentration chambers 22, 24 with a mixture of anion exchangers and cation exchangers. When anion exchange resins (AER) and cation exchange resins (CER) are used as the anion exchangers and cation exchangers, respectively, and the mixture of the anion exchange resins and the cation exchange resins is filled in the entire concentration chambers 22, 24, the apparent volume of the anion exchange resin is A and the apparent volume of the cation exchange resin is C, the mixing ratio A:C of these ion exchange resins is preferably between 20:80 and 60:40, and more preferably between 20:80 and 50:50. Even after the anion exchange resin and the cation exchange resin are mixed and filled into the concentration chambers 22, 24, the filled ion exchange resin can be removed from the concentration chambers 22, 24, separated into the anion exchange resin and the cation exchange resin, and the apparent volume of each can be measured to determine the mixing ratio A:C of the anion exchange resin and the cation exchange resin.

[0021] In order to suppress an increase in the applied voltage due to the placement of the cation exchange resin in the concentration chambers 22 and 24, it is preferable to place a reverse osmosis membrane device in the upstream stage of the water treatment device as described below, so that the concentration of hardness components in the water to be treated supplied to the treatment chamber 23 is 0.1 mg / L or less. The concentration of hardness components is defined as the amount of calcium and magnesium mixed with calcium carbonate (CaCO ３ ) and is expressed by the following formula (1).

[0022] Hardness [mg / L] = (Calcium content [mg / L] × 2.5) + (Magnesium content [mg / L × 4.1]) (1)

[0023] Next, the removal of oxidant components and ionic components in the water treatment device 10 shown in FIG. 1 will be described. Hereinafter, the oxidant component will be assumed to be hydrogen peroxide. However, oxidant components other than hydrogen peroxide can also be removed in a similar manner. When water to be treated containing hydrogen peroxide and / or ionic components is passed through the treatment chamber 23 with the concentration chamber feedwater supplied to the concentration chambers 22 and 24 and the electrode chamber feedwater supplied to the cathode chamber 25, the hydrogen peroxide in the water to be treated is decomposed into water and oxygen by a catalytic reaction with the platinum group metal catalyst supported on the ion exchanger in the treatment chamber 23. As a result, treated water from which hydrogen peroxide has been removed flows out of the treatment chamber 23. Furthermore, the water treatment device 10 is structurally similar to a typical EDI device in which the desalination chamber is filled with an ion exchanger supported on a platinum group metal catalyst, and the desalination chamber serves as the treatment chamber 23. Therefore, the ionic components in the water to be treated are adsorbed by the ion exchanger in the treatment chamber 23, and treated water from which the ionic components have been removed flows out of the treatment chamber 23. When the ion components and hydrogen peroxide are removed in this manner, the potential difference generated at the interface between the different ion exchange materials by the applied current in the treatment chamber 23 simultaneously causes the dissociation reaction of water shown in formula (2), resulting in the formation of hydrogen ions (H ＋ ) and hydroxide ions (OH － ) is generated.

[0024] H ２ O → H ＋ + OH － (2)

[0025] The interface between different ion exchange materials is, for example, the interface between an anion exchange membrane and a cation exchanger, the interface between a cation exchange membrane and an anion exchanger, or the interface between a cation exchanger and anion exchanger. The hydrogen ions and hydroxide ions thus generated exchange ions that were previously adsorbed on the ion exchanger in the treatment chamber 23, causing them to be desorbed from the ion exchanger. Among the desorbed ion components, anions migrate through the anion exchange membrane 32 to the first concentrating chamber 22 closer to the anode 11 and are discharged from the first concentrating chamber 22 as concentrated water. Meanwhile, cations migrate through the cation exchange membrane 33 to the second concentrating chamber 24 closer to the cathode 12 and are discharged from the second concentrating chamber 24 as concentrated water. Consequently, the ion components in the water to be treated supplied to the treatment chamber 23 migrate to the first concentrating chamber 22 and the second concentrating chamber 24 and are discharged. At the same time, the ion exchanger in the treatment chamber 23 is regenerated by the hydrogen ions or hydroxide ions. Electrode water is discharged from each of the anode chamber 21 and the cathode chamber 25. The DC voltage may be applied continuously or intermittently while the water to be treated is being passed through.

[0026] The feed water passed through the concentration chambers 22, 24 and the electrode chambers (i.e., the anode chamber 21 and the cathode chamber 25) is not particularly limited; independent feed waters may be used, or the same feed water may be branched and used. Furthermore, the feed water may be the water to be treated or the treated water discharged from the treatment chamber 23, or a separate system of feed water not containing oxidizing components such as hydrogen peroxide may be passed. From the viewpoint of suppressing deterioration of the ion exchange resin, it is preferable that the oxidizing agent concentration in the feed water passed through the concentration chambers 22, 24 and the electrode chambers is suppressed. In the figure, the flow direction of the feed water in the electrode chambers and concentration chambers 22, 24 is countercurrent to the flow direction of the water to be treated in the treatment chamber 23; however, water may be passed in a countercurrent manner between adjacent chambers.

[0027] In the configuration shown in FIG. 1 , a basic configuration consisting of [concentration compartment (C) 22 | anion exchange membrane (AEM) 32 | treatment compartment (H) 23 | cation exchange membrane (CEM) 33 | concentration compartment (C) 24] is disposed between the anode 11 and the cathode 12. This basic configuration is called a cell set. In practice, as in the case of a typical EDI device, multiple such cell sets can be arranged in parallel between the anode 11 and the cathode 12, and the multiple cell sets can be electrically connected in series between the electrodes to increase treatment capacity. In the example shown in FIG. 1 , N cell sets are arranged in parallel. In this case, adjacent cell sets can share adjacent concentration compartments. Therefore, the configuration of a water treatment device based on the present invention can be configured as [anode chamber | CEM | C | X | X | ... | X | AEM | cathode chamber], where X represents the repeating unit consisting of [AEM | H | CEM | C]. In such a series structure, for the treatment chamber 23 closest to the anode chamber 21, the anode chamber 21 itself can function as the concentration chamber 22 without an independent concentration chamber 22 interposed between the anode chamber 21 and the treatment chamber 23. Similarly, for the treatment chamber 23 closest to the cathode chamber 25, the cathode chamber 25 itself can function as the concentration chamber 24 without an independent concentration chamber 24 interposed between the cathode chamber 25 and the treatment chamber 23.

[0028] [First Embodiment] FIG. 2 shows a water treatment device 10 according to a first embodiment. The water treatment device 10 shown in FIG. 2 differs from the configuration shown in FIG. 1 in that the anode chamber 21 is filled with a cation exchange resin (CER), the cathode chamber 25 is filled with an anion exchange resin (AER), the concentration chambers 22 and 24 are filled with a mixed bed of anion exchange resin and cation exchange resin, and the treatment chamber 23 is filled with an anion exchange resin (Pd-AER) carrying a palladium catalyst as a platinum group metal catalyst. In the figure, the mixing and filling of two types of ion exchange resins is indicated by connecting the symbols representing the two types of ion exchange resins with an addition sign "+." As an example, the mixing of an anion exchange resin (AER) and a cation exchange resin (CER) in a mixed bed is represented as "AER + CER." Hereinafter, an anion exchange resin carrying a palladium catalyst is referred to as a catalyst-supported anion exchange resin (Pd-AER). Furthermore, when simply referred to as a cation exchange resin (CER) and an anion exchange resin (AER), they refer to a cation exchange resin and an anion exchange resin, respectively, that do not support a catalyst.

[0029] Here, we will explain how the water treatment device 10 of the first embodiment can efficiently remove boron components from the water to be treated. FIG. 3 is a diagram illustrating leakage of boron components from the treatment chamber 23. Here, it is assumed that the treatment chambers 23 and the concentration chambers 24 are alternately arranged between the anode 11 and the cathode 12, the treatment chambers 23 are filled with a catalyst-supported anion exchange resin (Pd-AER), and the concentration chambers 24 are filled with a single bed of anion exchange resin (AER). The boron components in the water to be treated are captured by the anion exchange resin as boron-containing anions in the treatment chamber 23 on the right side of the figure, and move to the concentration chamber 24 on the anode 11 side via the anion exchange membrane 32. The boron components are converted into boric acid (H ３ BO ３ ), boric acid dissociates in water as shown in equation (3).

[0030] H ３ BO ３ + H ２ O → H ＋ + B(OH) ４ － (3)

[0031] Therefore, the anion containing boron present in water is B(OH) ４ － As a result of the anions containing boron moving to the concentration compartment 24, the anions containing boron are captured by the anion exchange resin in the concentration compartment 24. Then, due to the electric field caused by the applied DC voltage, the anions containing boron move to the vicinity of the cation exchange membrane 33 in the concentration compartment 24, but since they are anions, they cannot move through the cation exchange membrane 33. Therefore, in the concentration compartment 24, the anions containing boron are concentrated near the cation exchange membrane 33 located on the anode 11 side. In addition, due to the applied DC voltage, hydrogen ions (H ＋ ) migrates to the treatment chamber 23. As a result, the pH of the region near the cation exchange membrane 33 in the concentration chamber 24 decreases. This region is where anions containing boron are concentrated, but hydrogen ions cause the anions to produce water and, for example, boric acid, forming a layer of water containing a high concentration of boric acid near the cation exchange membrane 33 in the concentration chamber 24. Since boric acid, a neutral molecule, can move through the cation exchange membrane 33, it migrates from the concentration chamber 24 through the cation exchange membrane 33 by concentration diffusion to the treatment chamber 23 where the concentration is lower. Ultimately, boron components removed from the water to be treated in a certain treatment chamber 23 will dissolve again in the water to be treated in a treatment chamber 23 located closer to the anode 11 than the treatment chamber 23, resulting in leakage of the boron components into the treated water discharged from the treatment chamber 23.

[0032] One way to prevent such leakage of boron components is to prevent a region of low pH from forming near the cation exchange membrane 33 in the concentration chamber 24. To achieve this, it is effective to quickly move the hydrogen ions that have migrated to the concentration chamber 24 via the cation exchange membrane 33 toward the cathode 12 within the concentration chamber 24. Therefore, in the water treatment device 10 of this embodiment, a cation exchange resin is provided in the concentration chamber 24. If it is acceptable for boron components to be contained in the electrode water discharged from the anode chamber 21, it is not necessary to fill the concentration chamber 22 adjacent to the anode chamber 21 (i.e., a concentration chamber that does not have a treatment chamber 23 between it and the anode chamber 21) with a cation exchange resin. Furthermore, if the treatment chamber 23 has a region that is particularly susceptible to adsorbing boron components, it is considered sufficient to provide the cation exchange resin only in the region of the concentration chamber 24 that faces the region of the treatment chamber 23 that is particularly susceptible to adsorbing boron components, across the anion exchange membrane 32.

[0033] In the water treatment device 10 of the first embodiment, the configuration of the treatment chamber 23 is not limited to that shown in FIG. 2 . For example, the catalyst-supported anion exchange resin (Pd-AER) may be filled in only a portion of the treatment chamber 23, with the remaining portion being filled with an ion exchange resin not supporting a catalyst. Alternatively, the catalyst-supported anion exchange resin (Pd-AER) filled in the treatment chamber 23 may be filled in a mixed bed with an ion exchange resin not supporting a catalyst. FIGS. 4A to 4D each illustrate another example of the arrangement of the ion exchange resin in the treatment chamber 23, depicting only the treatment chamber 23 and the anion exchange membrane 32 and cation exchange membrane 33 on both sides of the treatment chamber 23. In the example shown in FIG. 4A , the treatment chamber 23 is filled with a mixture of the catalyst-supported anion exchange resin (Pd-AER) and the anion exchange resin (AER). Instead of the anion exchange resin (AER), a cation exchange resin (CER) may be mixed with a catalyst-supported anion exchange resin (Pd-AER) and filled into the treatment chamber 23. Fig. 4B shows an example in which a cation exchange resin (CER) is mixed with a catalyst-supported anion exchange resin (Pd-AER) and filled into the treatment chamber 23. By mixing a catalyst-free ion exchange resin with a catalyst-supported anion exchange resin (Pd-AER), the amount of expensive platinum group metal catalyst used can be reduced, resulting in cost savings.

[0034] In the example shown in Figure 4C, the treatment chamber 23 is filled with a multi-layered bed configuration in which layers of catalyst-supported anion exchange resin (Pd-AER) and layers of anion exchange resin are alternately arranged, with the catalyst-supported anion exchange resin layer being upstream along the water flow. When such a treatment chamber 23 is used, oxidizing components such as hydrogen peroxide are decomposed and removed near the inlet of the water to be treated in the treatment chamber 23, and anions are desalted throughout the treatment chamber 23, while the catalyst-supported anion exchange resin and the anion exchange resin are simultaneously regenerated. Because oxidizing agents such as hydrogen peroxide may deteriorate ion exchange resins, when a catalyst-supported anion exchange resin (Pd-AER) layer is provided in a portion of the treatment chamber 23, it is preferable to provide the catalyst-supported anion exchange resin (Pd-AER) layer in the region of the treatment chamber 23 that serves as the inlet for the water to be treated.

[0035] When a layer or region filled with an anion exchange resin not supporting a metal catalyst is provided in the treatment chamber 23, the layer of anion exchange resin is preferably a layer containing a mixture of large and small particle diameter anion exchange resins to enhance the removal rate of boron, a weak acid component. In this specification, with regard to the particle diameter of ion exchange resins, a small particle diameter is defined as a particle diameter of 0.1 mm or more and 0.4 mm or less, and a large particle diameter is defined as a particle diameter exceeding 0.4 mm. A layer containing a mixture of large and small particle diameter ion exchange resins is referred to as a mixed particle diameter layer, and a large particle diameter layer consisting of large particle diameter ion exchange resins is referred to as a large particle diameter layer. Unless otherwise specified, the ion exchange resin layer described in this specification is referred to as a mixed particle diameter layer. Furthermore, since the particle diameter of bead-like or granular ion exchange resins is typically 1 mm or less, a large particle diameter ion exchange resin having a particle diameter of more than 0.4 mm and 1 mm or less may be used. Although the particle size of the ion exchange resin can be measured using a sieve, the value in the catalog of the ion exchange resin manufacturer may be used as the particle size in this embodiment. In the figure, the mixed particle size layer obtained by mixing a large particle size anion exchange resin and a small particle size anion exchange resin is represented by "L-S mixed AER."

[0036] Here, we will explain the mixing ratio of large-particle size ion exchange resin to small-particle size ion exchange resin in the mixed particle size layer. Because ion exchange resins are bead-shaped or granular, whether large or small, their apparent volumes, including the voids between particles, can be measured. Therefore, assuming that the apparent volume of the large-particle size ion exchange resin before mixing is L and the apparent volume of the small-particle size ion exchange resin is S, the mixing ratio L:S is preferably between 1:3 and 10:1, and more preferably between 1:1 and 5:1. Since a too high ratio of large-particle size ion exchange resin results in insufficient removal performance for weak acid components such as boron, a ratio of L:S = 10:1 or less is considered necessary to further enhance the removal rate of boron components. On the other hand, a too high ratio of small-particle size ion exchange resin may result in an increase in the water flow differential pressure. Even after the large particle size ion exchange resin and the small particle size ion exchange resin are mixed to form the mixed particle size layer, the mixing ratio of the large particle size ion exchange resin to the small particle size ion exchange resin can be determined. For example, the mixed particle size layer is removed from the treatment chamber 23, and classified using a sieve to separate the ion exchange resin having a particle size of 0.1 mm to 0.4 mm from the ion exchange resin having a particle size exceeding 0.4 mm, and the apparent volume of each is measured, thereby determining the mixing ratio L:S.

[0037] In the treatment chamber 23 shown in FIG. 4C , adsorption and removal of weak acid components, such as boron components, from the water being treated is primarily performed in a mixed particle size layer (L-S mixed AER) containing a mixture of large and small particle size anion exchange resins. The weak acid components adsorbed to the anion exchange resin in the mixed particle size layer pass through the anion exchange membrane 32 as anions and migrate to the concentrating chamber 22 on the anode 11 side. In the concentrating chamber 22, it is preferable that the anion concentration of the water flowing through the portion of the anion exchange membrane 32 facing the mixed particle size layer in the treatment chamber 23 is low. As described above, if a catalyst-supported anion exchange resin layer is provided on the inlet side of the treatment chamber 23, the mixed particle size layer will be located near the outlet. For these reasons, it is preferable that the flow of outlet water in the treatment chamber 23 and the flow of concentrating chamber feed water supplied to the concentrating chamber 22 are countercurrent to each other.

[0038] In the example shown in Figure 4D, a layer of catalyst-supported anion exchange resin, a layer of cation exchange resin, and a layer of anion exchange resin are packed in treatment chamber 23 in this order from the upstream side along the water flow in a multi-layer bed configuration. In this example, to promote the water dissociation reaction on the cathode 12 side of the anion exchange resin, an anion exchange membrane 37 is disposed at the interface between cation exchange membrane 33 and the anion exchange resin in treatment chamber 23. The anion exchange membrane 37 is not necessarily provided. In treatment chamber 23 shown in Figure 4D, removal of oxidizing agents such as hydrogen peroxide and desalination treatment of both anions and cations containing weak acid components are performed, and at the same time, regeneration of each ion exchange resin is performed.

[0039] [Second Embodiment] In an EDI device, the deionization chamber itself can be divided into two sub-deionization chambers by an ion exchange membrane, and water to be treated can be supplied to these two sub-deionization chambers in series. Similarly, in a water treatment device based on the present invention, the treatment chamber itself can be divided into two sub-treatment chambers by an ion exchange membrane, with water to be treated being supplied to one sub-treatment chamber and water flowing out from one sub-treatment chamber being supplied to the other sub-treatment chamber. Deionized water can be obtained as treated water from the other sub-treatment chamber. In this case, it is preferable to fill the sub-treatment chamber to which the water to be treated is first supplied with a catalyst-supported anion exchange resin (Pd-AER), and to supply water from which oxidizing components such as hydrogen peroxide have been decomposed and removed by the catalyst-supported anion exchange resin to the other sub-treatment chamber. A water treatment device 10 according to a second embodiment of the present invention, shown in FIG. 5, has the treatment chamber 23 of the water treatment device 10 shown in FIG. 2 with an intermediate anion exchange membrane 36, which divides the treatment chamber 23 into two sub-treatment chambers 26 and 27. The small treatment chamber located closer to the anode 11 across the anion exchange membrane 36 is the first small treatment chamber 26, and the small treatment chamber located closer to the cathode 12 is the second small treatment chamber 27. The water to be treated is supplied to the first small treatment chamber 26, and the outlet water from the first small treatment chamber 26 is supplied to the second small treatment chamber 27. The outlet water from the second small treatment chamber 27 is treated water (deionized water) from the water treatment device 10.

[0040] In the water treatment device 10 shown in FIG. 5 , the flow direction in the first sub-treatment chamber 26 and the flow direction in the second sub-treatment chamber 27 are opposite to each other, i.e., countercurrent. The flow direction in the concentrating chamber 22 on the anode 11 side is the same as the flow direction in the adjacent first sub-treatment chamber 26, and the two are in a parallel flow relationship. The flow direction in the second sub-treatment chamber 27, which is the outlet side of the treatment chamber, is in a countercurrent relationship with the flow direction in the adjacent concentrating chamber 24. The first sub-treatment chamber 26 is filled with a catalyst-supported anion exchange resin (Pd-AER) as a large particle layer. The second sub-treatment chamber 27 is filled with a cation exchange resin on its inlet side and an anion exchange resin on its outlet side as a large particle layer. The layer made of large particle anion exchange resin is represented in the figure as "L-AER." The cation exchange resin is usually provided as a large particle layer, but may also be a mixed particle layer. An anion exchange membrane 37 is provided at the interface where the cation exchange membrane 33 and the anion exchange resin in the second sub-treatment chamber 27 come into contact. The anion exchange membrane 37 may be omitted, and the anion exchange resin in the second sub-treatment chamber 27 may be in direct contact with the cation exchange membrane 33. In the water treatment device 10 shown in Figure 5, at least a portion of the ion exchange resin filled in the concentrating chambers 22, 24 is a cation exchange resin, thereby preventing boron components from leaking into the treated water discharged from the second sub-treatment chamber 27.

[0041] FIG. 6 shows another example of the configuration of a water treatment device according to the second embodiment. The water treatment device 10 shown in FIG. 6 is similar to the water treatment device 10 shown in FIG. 5 , except that the large particle size layer of anion exchange resin packed in the second small treatment chamber 27 is replaced with a mixed particle size layer of anion exchange resin (L-S mixed AER). In the second embodiment, in which the treatment chamber is partitioned into two small treatment chambers by an intermediate ion exchange membrane, the preferred mixing ratio of the large particle size ion exchange resin to the small particle size ion exchange resin in the mixed particle size layer is the same as that described in the first embodiment. In the water treatment device 10 shown in FIG. 6 , the water to be treated passes through the mixed particle size layer of anion exchange resin, enabling efficient removal of weak acid components such as boron.

[0042] FIG. 7 shows another example of the configuration of the water treatment device according to the second embodiment. The water treatment device 10 shown in FIG. 7 differs from the water treatment device 10 shown in FIG. 5 in that the catalyst-supported anion exchange resin packed in the first sub-treatment chamber 26 is a mixed particle size layer. In the figure, the mixed particle size layer of the catalyst-supported anion exchange resin is designated "L-S mixed Pd-AER." The catalyst-supported anion exchange resin is an anion exchange resin with a platinum group metal catalyst supported on its surface, and therefore also has anion exchange capacity. Therefore, by packing the first sub-treatment chamber 26 with the catalyst-supported anion exchange resin as a mixed particle size layer, it is possible to efficiently adsorb and remove weak acid components such as boric acid in the first sub-treatment chamber 26.

[0043] The hydrogen peroxide concentration in the water to be treated supplied to the water treatment device 10 of each of the above-described embodiments is, for example, 30 to 100 μg / L, and the boron concentration in the water to be treated is, for example, 10 to 100 μg / L. When such water to be treated is supplied to the water treatment device 10 and hydrogen peroxide and boron components are removed, as will be apparent from the examples described below, the hydrogen peroxide concentration in the treated water obtained from the water treatment device 10 can be set to 5 μg / L or less, and the boron removal rate, calculated as boron atoms, can be set to 99.0% or more, or even 99.5% or more.

[0044] The water treatment device 10 of each of the above-described embodiments can be incorporated into various water treatment systems, such as a pure water production system for producing pure water or ultrapure water. In the pure water production system shown in FIG. 8A , reverse osmosis membrane devices 41 and 42 are arranged in two series stages, with permeate from the upstream reverse osmosis membrane device 41 being supplied to the downstream reverse osmosis membrane device 42. The permeate from the downstream reverse osmosis membrane device 42 is supplied to an ultraviolet oxidation device 43, and the outlet water from the ultraviolet oxidation device 43 is supplied to the water treatment device 10 as the water to be treated. Pure water or ultrapure water is discharged from the water treatment device 10 as treated water. The pure water production system shown in FIG. 8B is the pure water production system shown in FIG. 8A , but with a water treatment device 15 provided between the downstream reverse osmosis membrane device 42 and the ultraviolet oxidation device 43, with the permeate from the downstream reverse osmosis membrane device 42 being supplied to the ultraviolet oxidation device 43 via the water treatment device 15. The water treatment device 15 provided upstream of the ultraviolet oxidation device 43 may be the same as the water treatment device 10 described above, in which the treatment chamber 23 is filled with an ion exchanger at least partially supported with a catalyst capable of decomposing oxidants. Alternatively, it may be a general EDI device without a catalyst capable of decomposing oxidants. The pure water production system shown in FIG. 8C is the pure water production system shown in FIG. 8A , except that a decarbonation device 45 is provided at the inlet of the ultraviolet oxidation device 43 to remove carbonate components from the permeated water of the downstream reverse osmosis membrane device 42. The decarbonation device 45 may be, for example, a decarbonation tower, a degassing membrane, or a decarbonation membrane. Here, the decarbonation device 45 is provided between the reverse osmosis membrane device 42 and the ultraviolet oxidation device 43. However, the decarbonation device 45 may also be provided upstream of the reverse osmosis membrane device 41. When the decarbonation device 45 is provided upstream of the reverse osmosis membrane device 41, the decarbonation device 45 may add an alkaline component to the water supplied to the reverse osmosis membrane device 41.

[0045] Next, the present invention will be described in more detail with reference to Examples, Reference Examples and Comparative Examples.

[0046] In the examples and comparative examples, a pure water production system was assembled and used, as shown in FIG. 8A , which included reverse osmosis membrane devices 41 and 42, an ultraviolet oxidation device 43, and a water treatment device 10, all arranged in two series. An ultraviolet oxidation device (FOV type) manufactured by Funatec Corporation was used as the ultraviolet oxidation device. It is known that the hydrogen peroxide concentration in treated water from ultraviolet oxidation devices used in typical pure water production systems is in the range of 10 to 100 μg / L. FIG. 9 shows the configuration of the main parts of the water treatment device 10 used in Example 1, FIG. 10 shows the configuration of the main parts of the water treatment device 10 used in Example 2, and FIG. 11 shows the configuration of the main parts of the water treatment device 10 used in Comparative Example 1. In each of the water treatment devices 10, the concentration chambers 22 and 24, the first sub-treatment chamber 26, and the second sub-treatment chamber 27 each used a frame-shaped cell with an opening measuring 150 mm x 300 mm and a thickness of 10 mm. The cells in each chamber were filled with ion exchange resin, and these cells were stacked in the thickness direction with an ion exchange membrane sandwiched between them to form the water treatment device 10. When the water treatment device 10 was operated, the flow rate of the water to be treated supplied to the first small treatment chamber 26 was set to 500 L / h, the flow rate of the feed water supplied to each of the concentration chambers 22 and 24 was set to 50 L / h, and the current density of the direct current applied between the anode 11 and the cathode 12 was set to 1.1 A / dm ２ It was decided.

[0047] Example 1 The water treatment device 10 shown in FIG. 9 used in Example 1 was the water treatment device 10 shown in FIG. 5 , with the anion exchange membrane 37 removed. The concentration chambers 22, 24 were filled with anion exchange resin and cation exchange resin in a mixing ratio A:C of 1:1. The permeate from the second-stage reverse osmosis membrane device 42 contained 110 μg / L of boron and 21 μg / L of TOC (total organic carbon). The water that passed through the ultraviolet oxidation device 43, i.e., the water to be treated, contained 110 μg / L of boron, 13 μg / L of TOC, and 90 μg / L of hydrogen peroxide. This treated water was treated using the water treatment device 10 shown in FIG. 9 , and the boron, TOC, and hydrogen peroxide concentrations of the treated water were measured. The boron removal rate, calculated as boron atoms, was 99.54%. The hydrogen peroxide concentration was less than 1.0 μg / L, and the TOC concentration was 3.6 μg / L.

[0048] Example 2 The water treatment device 10 shown in FIG. 10 used in Example 2 was the water treatment device 10 shown in FIG. 6 , with the anion exchange membrane 37 removed. The concentration chambers 22 and 24 were filled with anion exchange resin and cation exchange resin at a mixing ratio A:C of 1:1. The mixed particle size layer of anion exchange resin provided on the treated water outlet side of the second sub-treatment chamber 27 was filled with a mixture of large and small particle size anion exchange resins at a mixing ratio L:S of 1:1. The particle size of the large particle size anion exchange resin was 0.6 to 0.7 mm, and the particle size of the small particle size anion exchange resin was 0.3 mm. The permeate from the second-stage reverse osmosis membrane device 42 contained 100 μg / L of boron and 16 μg / L of TOC. The water that passed through the ultraviolet oxidation device 43, i.e., the water to be treated, had a boron concentration of 100 μg / L, a TOC concentration of 8 μg / L, and a hydrogen peroxide concentration of 63 μg / L. When the quality of the treated water was measured in the same manner as in Example 1, the boron removal rate was 99.70%, the hydrogen peroxide concentration was less than 1.0 μg / L, and the TOC concentration was 2.5 μg / L.

[0049] Comparative Example 1 The water treatment device 10 shown in FIG. 11 used in Comparative Example 1 was the same as the water treatment device 10 of Example 1 shown in FIG. 9 , except that the concentration chambers 22, 24 were filled with only anion exchange resin. The permeate from the second-stage reverse osmosis membrane device 42 contained 91 μg / L of boron and 20 μg / L of TOC. The water that passed through the ultraviolet oxidation device 43, i.e., the water to be treated, had a boron concentration of 91 μg / L, a TOC concentration of 12 μg / L, and a hydrogen peroxide concentration of 45 μg / L. When the quality of the treated water was measured in the same manner as in Example 1, the boron removal rate was 98.57%, the hydrogen peroxide concentration was less than 1.0 μg / L, and the TOC concentration was 7.5 μg / L.

[0050] The results of Examples 1 and 2 and Comparative Example 1 are summarized in Table 1. In Table 1, "TOC Removal Rate" indicates the TOC removal rate in the water treatment device 10. Table 1 shows that Comparative Example 1, in which the concentration chambers 22 and 24 were filled with only anion exchange resin, achieved a boron removal rate of 98.57%, whereas Examples 1 and 2, in which the concentration chambers 22 and 24 were filled with a mixture of anion exchange resin and cation exchange resin, achieved a boron removal rate of over 99.5%. A further 1% improvement in the removal rate, which is in the 98% range, means that the residual boron concentration after treatment is further reduced by more than half, assuming the same boron concentration before treatment, which is a significant effect. Regarding the layer of anion exchange resin filled on the outlet side of the second sub-treatment chamber 27, the boron removal rate was higher when the layer was a mixed particle size layer than when it was a large particle size layer. Furthermore, the TOC removal rate was higher in Examples 1 and 2 than in Comparative Example 1, which is also thought to be the effect of filling the concentration compartments 22 and 24 with a mixture of anion exchange resin and cation exchange resin.

[0051]

[0052] In each of the above-described embodiments, hydrogen peroxide is decomposed and removed by filling the treatment chamber 23 with an anion exchange resin supporting a palladium catalyst, i.e., a catalyst-supported anion exchange resin (Pd-AER). Therefore, in the reference example, desorption of palladium from the catalyst-supported anion exchange resin is examined.

[0053] (Reference Examples 1 and 2) A water treatment device similar to that shown in FIG. 2 was assembled in Reference Examples 1 and 2, except that the concentration compartments 22 and 24 were filled only with anion exchange resin. FIG. 12 shows the configuration of the main components of the water treatment device 10 used in Reference Examples 1 and 2. For assembly, frame-shaped cells with 100 mm x 100 mm square openings and a thickness of 10 mm were used for each of the concentration compartments 22 and 24 and the treatment compartment 23. Each cell in each compartment was filled with ion exchange resin, and these cells were stacked in the thickness direction with an ion exchange membrane sandwiched between them to form the water treatment device 10. An ion adsorbent was then placed in the line of treated water discharged from the treatment compartment 23 of the water treatment device 10. The ion adsorbent has ion removal or ion adsorption functions and is composed of, for example, an ion adsorption membrane, a monolithic organic porous ion exchanger, or an ion exchange resin. The ion adsorbent has functional groups that adsorb ions, such as cation exchange groups, anion exchange groups, or chelating groups. In particular, the ion adsorbent is preferably a monolithic organic porous ion exchanger, and one example is that described in International Publication No. 2019 / 221186. By providing the ion adsorbent in the treated water line and allowing it to adsorb palladium, the amount of metal catalyst (specifically palladium) desorbed from the catalyst-supported anion exchange resin can be measured.

[0054] In Reference Example 1, ultrapure water was used as the water to be treated supplied to the treatment chamber 23 of the water treatment device 10, the flow rate of the water to be treated was 88 L / h, and the applied current density was 1.1 A / dm ２ The water treatment device 10 was operated under the same conditions as in Reference Example 1. The obtained treated water was passed through the ion adsorbent for 24 hours, and then the amount of palladium adsorbed on the ion adsorbent was measured. In Reference Example 2, the water treatment device 10 was operated in the same manner as in Reference Example 1, except that 5 mg / L of carbon dioxide was added to the ultrapure water used as the water to be treated, and the amount of palladium adsorbed on the ion adsorbent was measured.

[0055] (Reference Example 3) The same water treatment device 10 as used in Comparative Example 1 was assembled. However, the frame-shaped cells used for each of the concentration chambers 22, 24, the first sub-treatment chamber 26, and the second sub-treatment chamber 27 had a square opening of 100 mm x 100 mm and a thickness of 10 mm. Ultrapure water was used as the water to be treated, supplied to the treatment chamber 23 of the water treatment device 10, and the flow rate of the water to be treated was 50 L / h and the applied current density was 1.1 A / dm ２ The water treatment device 10 was operated as described above. The obtained treated water was passed through an ion adsorbent for 24 hours, and then the amount of palladium adsorbed on the ion adsorbent was measured.

[0056] FIG. 13 shows the amounts of palladium measured in Reference Examples 2 and 3 relative to the amount of palladium measured in Reference Example 1, which is set to 100%. The amount of palladium adsorbed by the ion adsorbent in Reference Example 2 increased by approximately 40% compared to Reference Example 1. This is thought to be due to the addition of carbonate to the water being treated. In contrast, in Reference Example 3, the amount of palladium adsorbed by the ion adsorbent was less than 10% of that in Reference Example 1. This indicates that a water treatment device preferably has a cation exchange resin and an anion exchange resin downstream of the catalyst-supported anion exchange resin (Pd-AER). Furthermore, it was also found that a means for removing carbonate from the water being treated is preferably provided upstream of the water treatment device 10.

[0057] After operating the water treatment device 10 used in Reference Example 1 for one month, ion exchange resins containing catalyst-supported ion exchange resins (Pd-AER) were recovered from the treatment chamber 23 and the concentration chambers 22 and 24, and the amount of palladium supported on the recovered ion exchange resins was examined. Figure 14 shows the amount of supported palladium relative to the amount of palladium supported on the ion exchange resin recovered from the treatment chamber 23, which is set to 100%. Figure 14 shows that palladium was also detected in the ion exchange resin recovered from the concentration chambers 22 and 24, where no catalyst-supported anion exchange resin should be present. From the perspective of preventing palladium from leaking outside the water treatment device 10, it is clear that filling the concentration chambers 22 and 24 with a mixture of ion exchange resins (mixed bed) is preferable to filling the anion exchange resin or cation exchange resin in a single layer.

[0058] (Reference Example 4) Since it was confirmed that palladium originating from the catalyst-supported anions filled in treatment chamber 23 migrates to concentration chambers 22, 24, Reference Example 4 used a water treatment device similar to water treatment device 10 in Comparative Example 1, except that treatment chamber 23 was filled with only anion exchange resin that did not support a metal catalyst. Concentration chambers 22, 24 were filled with only anion exchange resin. Hydrogen peroxide was added to the water supplied to concentration chambers 22, 24, and ultrapure water was used as the water to be treated in treatment chamber 23. The water treatment device was operated, and the hydrogen peroxide concentration in the concentrated water discharged from concentration chambers 22, 24 was measured.

[0059] (Reference Example 5) A water treatment device having the same configuration as that in Example 2 was assembled, and ultrapure water was used as the water to be treated as in Reference Example 4. Hydrogen peroxide was added to the water supplied to the concentration chambers 22 and 24, and the water treatment device was operated, and the hydrogen peroxide concentration in the concentrated water was measured.

[0060] FIG. 15 shows the results of measuring the hydrogen peroxide concentrations in the concentrated water in Reference Examples 4 and 5, expressed as relative values, with the hydrogen peroxide concentration in the concentrated water in Reference Example 4 taken as 100%. As shown in FIG. 15 , in Reference Example 5, in which the treatment chamber 23 adjacent to the concentrating chambers 22 and 24 was filled with a catalyst-supported anion exchange resin, the hydrogen peroxide concentration in the concentrated water was approximately half that of Reference Example 4, in which the treatment chamber 23 was filled with an anion exchange resin without a metal catalyst. This is thought to be because palladium desorbed from the catalyst-supported anion exchange resin in the treatment chamber 23 migrates to the concentrating chambers 22 and 24 due to the action of current and is adsorbed onto the ion exchange resin in the concentrating chambers 22 and 24, thereby decomposing and removing hydrogen peroxide in the concentrating chambers 22 and 24 as well. Palladium may also migrate to the electrode chambers, particularly the cathode chamber 25, through a similar process.

[0061] Generally, ion exchange resins are deteriorated by oxidizing agents such as hydrogen peroxide, but the above-mentioned Reference Example demonstrated that by filling treatment chamber 23 with a catalyst-supported anion exchange resin, palladium is also adsorbed onto the ion exchange resin in concentration chambers 22, 24 or the electrode chambers. Oxidizing agents such as hydrogen peroxide are decomposed in concentration chambers 22, 24 and the electrode chambers by the palladium adsorbed onto the ion exchange resin, so by filling treatment chamber 23 with a catalyst-supported anion exchange resin, it is possible to suppress deterioration of the ion exchange resin in concentration chambers 22, 24 and the electrode chambers.

[0062] In a typical pure water production system, hydrogen peroxide is present in the water exiting the ultraviolet oxidation device at a concentration of approximately 10 to 100 μg / L. Supplying water containing hydrogen peroxide in this concentration range to the concentrating chamber or electrode chamber of a typical EDI device is discouraged from the standpoint of preventing deterioration of the ion exchange resin. By using a water treatment device based on the present invention, the water exiting the ultraviolet oxidation device can be used as the supply water to the concentrating chamber or electrode chamber. Furthermore, the water treatment device 10 can be operated under conditions in which the hydrogen peroxide concentration in the concentrated water and electrode water discharged from the concentrating chambers 22 and 24 and the electrode chambers is 5 μg / L or higher.

[0063] 10, 15 Water treatment device 11 Anode 12 Cathode 21 Anode chamber 22, 24 Concentration chamber 23 Treatment chamber 25 Cathode chamber 26, 27 Small treatment chamber 31, 33 Cation exchange membrane (CEM) 32, 34, 36, 37 Anion exchange membrane (AEM) 41, 42 Reverse osmosis membrane device 43 Ultraviolet oxidation device

Claims

1. A water treatment device comprising: a treatment chamber separated by a pair of ion exchange membranes between an anode and a cathode, the pair being made up of a first ion exchange membrane disposed on the anode side and a second ion exchange membrane disposed on the cathode side, and containing a metal catalyst having an oxidant decomposition ability; and a pair of concentration chambers disposed adjacent to the treatment chamber via the first ion exchange membrane and the second ion exchange membrane, respectively, and filled with ion exchange resin, wherein at least a portion of the ion exchange resin filled in the concentration chamber is a cation exchange resin, and water to be treated is supplied to the treatment chamber, and oxidants and boron are removed from the water to be treated.

2. The water treatment device according to claim 1, wherein the catalyst capable of decomposing an oxidant is a metal catalyst capable of decomposing hydrogen peroxide.

3. The water treatment device according to claim 2, wherein the metal catalyst is a platinum group metal catalyst, and the treatment chamber is filled with an ion exchange resin carrying the platinum group metal catalyst.

4. The water treatment device according to claim 3, wherein the concentrating chamber is filled with a mixture of anion exchange resin and cation exchange resin.

5. The water treatment device according to claim 4, wherein the ion exchange resin supporting the platinum group metal catalyst is a catalyst-supported anion exchange resin that is an anion exchange resin supporting the platinum group metal catalyst, and a cation exchange resin and an anion exchange resin are packed in the treatment chamber downstream of the catalyst-supported anion exchange resin along the flow of water in the treatment chamber.

6. The water treatment device according to claim 4, wherein the ion exchange resin supporting the platinum group metal catalyst is a catalyst-supported anion exchange resin which is an anion exchange resin supporting the platinum group metal catalyst, the treatment chamber is provided with an intermediate ion exchange membrane located between the pair of ion exchange membranes and is partitioned into a first sub-treatment chamber and a second sub-treatment chamber by the intermediate ion exchange membrane, the first sub-treatment chamber and the second sub-treatment chamber are connected to each other so that the water to be treated is supplied to one of the first and second sub-treatment chambers and water flowing out of the one sub-treatment chamber flows into the other sub-treatment chamber, the one sub-treatment chamber is filled with the catalyst-supported anion exchange resin, and the other sub-treatment chamber is filled with a cation exchange resin and an anion exchange resin.

7. A water treatment device as described in claim 5 or 6, wherein a particle size of 0.1 mm or more and 0.4 mm or less is defined as a small particle size, and a particle size exceeding 0.4 mm is defined as a large particle size, and the anion exchange resin filled in the treatment chamber downstream of the catalyst-supported anion exchange resin along the flow of water in the treatment chamber is in a state where a large particle size anion exchange resin and a small particle size anion exchange resin are mixed.

8. A water treatment system comprising: an ultraviolet oxidation device; and a water treatment device according to any one of claims 1 to 6, wherein outlet water from the ultraviolet oxidation device is supplied to the treatment chamber as the water to be treated, and at least a portion of the water supplied to the concentration chamber is the outlet water from the ultraviolet oxidation device.

9. The water treatment system according to claim 8, further comprising a carbon dioxide removing means for removing carbon dioxide from the water to be treated, which is provided upstream of the water treatment device.

10. A water treatment method for removing oxidants and boron contained in water to be treated, comprising a treatment step of passing the water to be treated through a treatment chamber partitioned by a first ion exchange membrane on the side facing the anode and by a second ion exchange membrane on the side facing the cathode, and at least a portion of which is filled with a catalyst having oxidant decomposition ability, while applying a DC voltage between an anode and a cathode, wherein a pair of concentration chambers filled with ion exchange resin and disposed adjacent to the treatment chamber via the first ion exchange membrane and the second ion exchange membrane, respectively, are filled with at least a cation exchange resin.

11. The water treatment method according to claim 10, wherein the catalyst capable of decomposing an oxidant is a metal catalyst capable of decomposing hydrogen peroxide.

12. The water treatment method according to claim 11, wherein the metal catalyst is a platinum group metal catalyst, and the treatment chamber is filled with a catalyst-supported ion exchange resin which is an anion exchange resin supporting the platinum group metal catalyst.

13. The water treatment method according to claim 12, wherein the treatment process comprises a first step of passing the water to be treated through the catalyst-supported ion exchange resin, and a second step of passing the water to be treated that has been passed through the catalyst-supported ion exchange resin in the first step, subsequently through a layer made of a cation exchange resin and a layer made of anion exchange resin.

14. The water treatment method according to any one of claims 10 to 13, further comprising a step of removing carbon dioxide from the water to be treated prior to the treatment step.

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