JP7634370B2 - Hydrogen peroxide removal method and device, and pure water production device - Google Patents

Description

The present invention relates to a method and device for removing hydrogen peroxide from water during wastewater treatment and the production of pure water and ultrapure water, and to a pure water production system.

Hydrogen peroxide has been widely used as an oxidizing agent together with chemicals such as acids and alkalis in the cleaning and surface treatment of electronic components. Because hydrogen peroxide has oxidizing power, it is necessary to properly manage and remove hydrogen peroxide so that it does not flow into equipment with low oxidation resistance, such as ion exchange resin devices that make up water treatment systems. In general, deterioration caused by oxidizing agents causes irreparable and fatal damage to water treatment equipment. In particular, it is known that the ion exchange resin in an electrodeionization device (EDI) is easily deteriorated in the presence of oxidizing agents. For example, it is known that when hydrogen peroxide is contained in the water to be treated in an ultrapure water production system, part of the ion exchange resin contained in the ultrapure water production system is oxidized and decomposed, causing the elution of organic matter.

Hydrogen peroxide also has strong sterilizing power due to its oxidizing power, so when wastewater containing hydrogen peroxide is discharged from a pure water system to an external wastewater system, it is necessary to remove the hydrogen peroxide before discharging it, as this may affect the biological treatment equipment included in the wastewater treatment system. In addition, pure water and ultrapure water production systems sometimes use ultraviolet oxidation equipment aimed at breaking down total organic carbon (TOC) components, and it is known that the treated water after ultraviolet oxidation contains trace amounts of hydrogen peroxide.

Conventional methods for reducing hydrogen peroxide in water to be treated include adding a reducing agent, contacting the water with activated carbon, and contacting the water with a metal-supported resin. In the method of adding a reducing agent, a reducing agent such as sodium sulfite, sodium hydrogen sulfite, or sodium thiosulfate is added to the water to be treated that contains hydrogen peroxide. Since the reaction rate between the reducing agent and hydrogen peroxide is very high, this method can reliably decompose and remove hydrogen peroxide. However, it is difficult to control the amount of reducing agent added, and in order to reliably remove hydrogen peroxide, an excessive amount of reducing agent must be added, and the reducing agent increases the amount of ions in the liquid, which can lead to a deterioration in water quality.

In the method of contacting the water with activated carbon, a packed tower of activated carbon is usually installed and the water to be treated is passed through it, but because the reaction rate is slow, the space velocity of the water passing through cannot be increased, and this poses the problem of the equipment becoming larger. In addition, there is a concern that the activated carbon itself may be oxidized as the hydrogen peroxide decomposes, causing the particles to collapse.

As a method of contacting with a metal-supported resin, for example, a method of contacting the water to be treated containing hydrogen peroxide with a catalytic resin in which a palladium or platinum catalyst is supported on an ion exchange resin has been proposed (Patent Document 1). In this method, hydrogen peroxide is decomposed by the reaction shown in the following formula.
2H ₂ O ₂ → 2H ₂ O+O ₂

Although not related to the decomposition and removal of hydrogen peroxide, Patent Document 2 discloses that, in relation to the ion exchanger filled in the concentration chamber of an electric regenerative deionization device, the concentration chamber is filled with the ion exchanger so that the volume of the ion exchanger removed from the concentration chamber after the desalination process in the desalination chamber is 103% to 125% of the volume of the concentration chamber.

JP 2007-185587 A JP 2016-129863 A

The method of decomposing and removing hydrogen peroxide using catalytic resins, which are ion exchange resins carrying catalysts such as palladium or platinum, has a higher decomposition rate of hydrogen peroxide than the method of contacting hydrogen peroxide with activated carbon, but it is desirable to further improve the decomposition rate. In addition, it is known that the decomposition rate of hydrogen peroxide decreases over time in the method using catalytic resins, and it is desirable to be able to decompose hydrogen peroxide stably over a long period of time.

The present invention aims to provide a hydrogen peroxide removal method and device that can quickly and stably treat a wide range of hydrogen peroxide concentrations in the water being treated over a long period of time, as well as a pure water production system equipped with said device. Another aim of the present invention is to provide a hydrogen peroxide removal method and device that can also be applied to wastewater treatment.

The hydrogen peroxide removal method of the present invention is a method for removing hydrogen peroxide contained in water to be treated, and includes a step of passing the water to be treated through a hydrogen peroxide removal chamber that is provided between an anode and a cathode and filled with an ion exchanger while applying a DC voltage between the anode and the cathode, at least a part of the ion exchanger filled in the hydrogen peroxide removal chamber is an ion exchanger that supports a metal catalyst having hydrogen peroxide decomposition ability, and the filling rate, which is the value obtained by dividing the bulk volume , including voids between the ion exchanger particles, in a free state of the ion exchanger removed from the hydrogen peroxide removal chamber after the water passing step by the volume of the hydrogen peroxide removal chamber, is 95% or more and 125% or less.

The hydrogen peroxide removal apparatus of the present invention is a hydrogen peroxide removal apparatus that removes hydrogen peroxide contained in water to be treated, and has an anode and a cathode, and a hydrogen peroxide removal chamber provided between the anode and the cathode and filled with an ion exchanger, at least a part of the ion exchanger filled in the hydrogen peroxide removal chamber is an ion exchanger supporting a metal catalyst having hydrogen peroxide decomposition ability, a DC voltage is applied between the anode and the cathode, and the filling rate, which is the value obtained by dividing the bulk volume, including voids between the ion exchanger particles, in a free state of the ion exchanger when the DC voltage is applied between the anode and the cathode to pass the water to be treated through the hydrogen peroxide removal chamber and then removed from the hydrogen peroxide removal chamber, is 95% or more and 125% or less.

The pure water production system of the present invention has a hydrogen peroxide removal device based on the present invention and an ultraviolet oxidation device provided upstream of the hydrogen peroxide removal device.

In the present invention, an ion exchanger carrying a metal catalyst having hydrogen peroxide decomposition ability is filled in the hydrogen peroxide removal chamber arranged between the anode and the cathode, and a direct current voltage is applied between the anode and the cathode while the water to be treated is passed through the hydrogen peroxide removal chamber. By configuring in this way, according to the present invention, the decomposition of hydrogen peroxide and the electrical regeneration of the ion exchanger proceed in parallel, and the hydrogen peroxide decomposition and removal performance can be maintained at a high level for a long period of time. Furthermore, the present invention is characterized in that the filling rate, which is the value obtained by dividing the volume of the ion exchanger in a free state taken out from the hydrogen peroxide removal chamber after passing the water to be treated through the hydrogen peroxide removal chamber by the volume of the hydrogen peroxide removal chamber by applying a direct current voltage between the anode and the cathode, is 95% or more and 125% or less. By filling the hydrogen peroxide removal chamber with the ion exchanger to achieve such a filling rate, the effective electrical resistance of the hydrogen peroxide removal chamber can be reduced while smoothly passing the water to be treated through the hydrogen peroxide removal chamber, and the value of the direct current voltage applied to the hydrogen peroxide removal device can be reduced. By reducing the applied DC voltage, the present invention makes it possible to reduce the power consumption per unit flow rate of treated water supplied to the hydrogen peroxide removal chamber.

The above-mentioned filling rate of the ion exchanger filled in the hydrogen peroxide removal chamber is measured after applying a DC voltage between the anode and cathode and passing the water to be treated through the hydrogen peroxide removal chamber. In this state, the ion exchanger contains sufficient water and has a mixture of regenerated and salt ions. For example, the volume of the ion exchanger, which is an ion exchange resin, varies depending on the water content and whether the ion form is regenerated or salt, and the volume of the ion exchanger is maximum when it swells with sufficient water and has the regenerated ion form. Therefore, the hydrogen peroxide removal chamber is filled with ion exchangers that have a relatively small water content and/or have a salt ion form, and then a DC voltage is applied and the water to be treated is passed through the ion exchanger to increase its volume, thereby filling the hydrogen peroxide removal chamber with ion exchangers so that the filling rate exceeds 100%.

In the present invention, 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. Among these, platinum group metal catalysts are more preferably used because of their high catalytic activity for decomposing hydrogen peroxide. A platinum group metal catalyst is a catalyst containing one or more metals selected from ruthenium, rhodium, palladium, osmium, iridium, and platinum. A platinum group metal catalyst may contain any one of these metal elements alone or may be a combination of two or more of these. Among these, platinum, palladium, and platinum/palladium alloys have high catalytic activity and are preferably used as platinum group metal catalysts.

The present invention is more advantageous when removing hydrogen peroxide from treated water containing carbonic acid components that are a load on the anion exchanger by using an anion exchanger carrying a platinum group metal catalyst as a metal catalyst. When the hydrogen peroxide removal chamber is partitioned by an anion exchange membrane on the anode side, the anion components, i.e., carbonic acid components, adsorbed from the treated water to the anion exchanger in the hydrogen peroxide removal chamber are desorbed from the anion exchanger by electrical regeneration and discharged in the form of anions from the hydrogen peroxide removal chamber via the anion exchange membrane on the anode side. In other words, the present invention not only produces treated water from which hydrogen peroxide has been removed, but also improves the quality of the treated water.

In addition, in the present invention, the regeneration state of the ion exchanger carrying the platinum group metal catalyst can be maintained by continuously applying a DC voltage, so that it is possible to operate the device by setting the space velocity (SV) to 100 h ⁻¹ or more. The space velocity SV is a unit that indicates how many times the volume of the ion exchanger carrying the platinum group metal catalyst filled in the hydrogen peroxide removal chamber is treated per unit time. Specifically, the SV value can be calculated by dividing the flow rate (L/h) of the water to be treated by the volume (L) of the ion exchanger carrying the platinum group metal catalyst. Being able to operate at a SV value that is twice or three times the normal value is advantageous because it makes it possible to reduce the amount of catalyst, which is expensive because it carries a precious metal, to 1/2 or 1/3 in order to treat the same amount of water to be treated.

In the hydrogen peroxide removal device of the present invention, a desalting chamber filled with an ion exchanger may be provided adjacent to the cathode or anode side of the hydrogen peroxide removal chamber via an intermediate ion exchange membrane, and treated water treated by the hydrogen peroxide removal chamber may be passed through the desalting chamber. This configuration allows hydrogen peroxide to be removed from the water to be treated and desalted at the same time. By using the treated water discharged from the desalting chamber, it becomes possible to produce highly pure water and ultrapure water.

According to the present invention, it becomes possible to stably remove hydrogen peroxide over a long period of time from water to be treated that contains a wide range of hydrogen peroxide concentrations. As a result, it becomes possible to stably operate the entire water treatment facility to which water to be treated that contains hydrogen peroxide is supplied, for example.

1 is a schematic diagram showing a hydrogen peroxide removal device according to a first embodiment of the present invention. FIG. FIG. 2 is a schematic diagram showing a specific example of a hydrogen peroxide removal device. 3 is a schematic diagram showing an example of the flow of water in the hydrogen peroxide removal device shown in FIG. 2. FIG. 2 is a schematic diagram showing another specific example of a hydrogen peroxide removal device. FIG. 2 is a schematic diagram showing another specific example of a hydrogen peroxide removal device. FIG. 2 is a schematic diagram showing another specific example of a hydrogen peroxide removal device. FIG. 2 is a schematic diagram showing another specific example of a hydrogen peroxide removal device. FIG. 2 is a schematic diagram showing another specific example of a hydrogen peroxide removal device. FIG. 4 is a schematic diagram showing a hydrogen peroxide removal device according to a second embodiment of the present invention. FIG. 2 is a schematic diagram showing another specific example of a hydrogen peroxide removal device. FIG. 2 is a schematic diagram showing another specific example of a hydrogen peroxide removal device. FIG. 2 is a schematic diagram showing another specific example of a hydrogen peroxide removal device. FIG. 2 is a schematic diagram showing another specific example of a hydrogen peroxide removal device. FIG. 11 is a schematic diagram showing a hydrogen peroxide removal device according to a third embodiment of the present invention. FIG. 2 is a schematic diagram showing a specific example of a hydrogen peroxide removal device. FIG. 16 is a schematic diagram illustrating the operation of the hydrogen peroxide removal device shown in FIG. 15 . FIG. 2 is a schematic diagram showing another specific example of a hydrogen peroxide removal device. FIG. 2 is a schematic diagram showing another specific example of a hydrogen peroxide removal device. FIG. 2 is a schematic diagram showing another specific example of a hydrogen peroxide removal device. FIG. 2 is a schematic diagram showing another specific example of a hydrogen peroxide removal device. FIG. 2 is a schematic diagram showing another specific example of a hydrogen peroxide removal device. FIG. 13 is a schematic diagram showing a hydrogen peroxide removal device according to a fourth embodiment of the present invention. FIG. 2 is a schematic diagram showing another specific example of a hydrogen peroxide removal device. FIG. 2 is a schematic diagram showing another specific example of a hydrogen peroxide removal device. FIG. 2 is a schematic diagram showing another specific example of a hydrogen peroxide removal device. FIG. 2 is a schematic diagram showing another specific example of a hydrogen peroxide removal device. FIG. 1 is a schematic diagram showing an example of the configuration of a conventional water purifying apparatus. 1 is a schematic diagram showing an example of the configuration of a pure water producing apparatus based on the present invention. FIG. 1 is a schematic diagram showing an example of the configuration of an ultrapure water production apparatus. FIG. 2 is a schematic diagram showing another example of the configuration of an ultrapure water production apparatus. FIG. 2 is a schematic diagram showing another example of the configuration of an ultrapure water production apparatus. FIG. 2 is a schematic diagram showing another example of the configuration of an ultrapure water production apparatus. FIG. 11 is a schematic diagram showing a main part of a hydrogen peroxide removal device according to a second embodiment. FIG. 11 is a schematic diagram showing a main part of a hydrogen peroxide removal device according to a third embodiment. 1 is a graph showing the results of Example 5.

Next, the present invention will be described with reference to the drawings. However, the present invention is not limited to the embodiment shown in the drawings.

[First embodiment]
FIG. 1 shows the configuration of a hydrogen peroxide removal device according to a first embodiment of the present invention. The hydrogen peroxide removal device according to the present invention includes at least one hydrogen peroxide removal chamber 23 between an anode chamber 21 equipped with an anode 11 and a cathode chamber 25 equipped with a cathode 12, and the hydrogen peroxide removal 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 anode 12 side. The hydrogen peroxide removal chamber 23 is filled with an ion exchanger carrying a metal catalyst having hydrogen peroxide decomposition ability. In the example shown in FIG. 1, the first ion exchange membrane located on the anode 11 side is an anion exchange membrane 32, and the second ion exchange membrane located on the cathode 12 side is a cation exchange membrane 33, and the hydrogen peroxide removal chamber 23 is filled with an ion exchanger (IER) carrying a platinum group metal catalyst. In the figure, the ion exchanger carrying a platinum group metal catalyst is indicated as "Cat. IER". 1 , an anode 11 and a cathode 12 face each other, and an anode chamber 21, a first concentrating chamber 22, a hydrogen peroxide removal chamber 23, a second concentrating 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 first concentrating chamber 22 are separated by a cation exchange membrane 31, the first concentrating chamber 22 and the hydrogen peroxide removal chamber 23 are separated by an anion exchange membrane 32, the hydrogen peroxide removal chamber 23 and the second concentrating chamber 24 are separated by a cation exchange membrane 33, and the second concentrating chamber 24 and the cathode chamber 25 are separated by an anion exchange membrane 34. The anode chamber 21, the first concentrating chamber 22, the second concentrating chamber 24, and the cathode chamber 25 are each filled with an ion exchanger that does not support a platinum group metal catalyst. Here, the ion exchanger may be either an anion exchanger or a cation exchanger, or both of them. When both an anion exchanger and a 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-layered bed configuration in which an anion exchanger layer and a cation exchanger layer are packed separately.

Next, the operation of the hydrogen peroxide removal apparatus shown in Fig. 1 will be described. When hydrogen peroxide is removed from water to be treated that contains hydrogen peroxide, feed water is passed through the anode chamber 21, the first concentrating chamber 22, the second concentrating chamber 24, and the cathode chamber 25, respectively, and the water to be treated is passed through the hydrogen peroxide removal chamber 23 in a state in which a DC voltage is applied between the anode 11 and the cathode 12. When the water to be treated that contains hydrogen peroxide is passed through the hydrogen peroxide removal chamber 23, 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 hydrogen peroxide removal chamber 23, and as a result, treated water from which hydrogen peroxide has been removed flows out from the hydrogen peroxide removal chamber 23. At this time, in the hydrogen peroxide removal chamber 23, a dissociation reaction of water (H ₂ O→H ⁺ +OH ⁻ ) occurs simultaneously due to a potential difference generated at the interface between different ion exchange materials by the applied current, and hydrogen ions (H ⁺ ) and hydroxide ions (OH ⁻ ) are generated. 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 an anion exchanger. The hydrogen ions and hydroxide ions thus generated exchange the ionic components previously adsorbed on the ion exchanger in the hydrogen peroxide removal chamber 23, and are desorbed from the ion exchanger. Among the desorbed ionic components, anions move through the anion exchange membrane 32 to the first concentrating chamber 22 closer to the anode 11, and are discharged from this first concentrating chamber 22 as concentrated water. On the other hand, the 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. Ultimately, the ionic components in the water to be treated supplied to the hydrogen peroxide removal chamber 23 migrate to the first concentrating chamber 22 and the second concentrating chamber 24 and are discharged, and at the same time, the ion exchanger in the hydrogen peroxide removal chamber 23 is regenerated. Electrode water is discharged from the anode chamber 21 and the cathode chamber 25, respectively. The application of the DC voltage may be continuous or intermittent while the water to be treated is passing through.

There are no particular limitations on the supply water passed through the concentration chambers 22, 24 and the electrode chambers (i.e., the anode chamber 21 and the cathode chamber 25), and independent supply water can be used for each, or the same supply water can be branched and used. Furthermore, the water to be treated or the treated water discharged from the hydrogen peroxide removal chamber 23 can be passed as the supply water, or a supply water from a separate system that does not contain hydrogen peroxide can be passed. In the figure, the flow of the supply water and the water to be treated in the electrode chambers, the concentration chambers 22, 24, and the hydrogen peroxide removal chamber 23 is parallel to each other, but the water may be passed in a countercurrent manner between adjacent chambers.

In the configuration shown in FIG. 1, a basic configuration consisting of [concentration chamber (C) 22 | anion exchange membrane (AEM) 32 | hydrogen peroxide removal chamber (H) 23 | cation exchange membrane (CEM) 33 | concentration chamber (C) 24] is arranged between the anode 11 and the cathode 12. This basic configuration is called a cell set. In practice, a plurality of such cell sets ("N sets" in FIG. 1) are arranged in parallel between the electrodes, and the plurality of cell sets are electrically connected in series with one end serving as the anode 11 and the other end serving as the cathode 12, thereby increasing the processing capacity. In this case, adjacent concentration chambers can be shared between adjacent cell sets, so that the configuration of the hydrogen peroxide removal 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, the anode chamber 21 itself can function as the concentration chamber 22 for the hydrogen peroxide removal chamber 23 closest to the anode chamber 21, without an independent concentration chamber 22 between the anode chamber 21 and the chamber 21. Similarly, the cathode chamber 25 itself can function as the concentration chamber 24 for the hydrogen peroxide removal chamber 23 closest to the cathode chamber 25, without an independent concentration chamber 24 between the cathode chamber 25 and the chamber 25.

In the hydrogen peroxide removal device according to the present invention, as described above, a direct current voltage is applied between the anode 11 and the cathode 12 to electrically regenerate the ion exchanger in the hydrogen peroxide removal chamber 23, for example, granular ion exchange resin, while removing and desalination hydrogen peroxide. In order to reduce the voltage applied between the anode 11 and the cathode 12, it is effective to pack the ion exchanger densely in the hydrogen peroxide removal chamber 23 within a range in which water flow is not hindered. It is also known that the particle size of ion exchangers, particularly ion exchange resins, changes depending on their water content and ion form. When the ion form is the regenerated form, that is, when hydroxide ions are adsorbed to the ion exchange group in the case of an anion exchanger, or when hydrogen ions are adsorbed to the ion exchange group in the case of a cation exchanger, the particle size becomes larger than when the ion form is other than the regenerated form (for example, when chloride ions or sodium ions are adsorbed), that is, when the ion exchanger is in the salt form. Also, the particle size becomes larger when the water content of the ion exchanger is large. Ion exchangers, particularly ion exchange resins, are elastic and deform when pressure is applied, and return to their original shape when pressure is removed. Assuming that hydrogen peroxide removal chamber 23 does not deform, it is preferable to fill hydrogen peroxide removal chamber 23 with ion exchangers in a small particle size state, and then expand the ion exchangers by passing water through or by electrical regeneration so that the ion exchangers are densely packed in hydrogen peroxide removal chamber 23. However, if the ion exchangers are too densely packed in hydrogen peroxide removal chamber 23, this is undesirable as it inhibits water from passing through hydrogen peroxide removal chamber 23.

Therefore, in the hydrogen peroxide removal device according to the present invention, a DC voltage is applied between the anode 11 and the cathode 12 to pass the water to be treated through the hydrogen peroxide removal chamber 23, and then the filling rate, which is the value obtained by dividing the volume of the ion exchanger in a free state that is removed from the hydrogen peroxide removal chamber 23 by the volume of the hydrogen peroxide removal chamber 23, is set to be 95% or more and 125% or less. The filling rate is preferably 102% or more and 125% or less. Here, the volume of the ion exchanger in a free state refers to the apparent volume including the voids between the particles when the ion exchanger is not restrained by the hydrogen peroxide removal chamber 23. As described below, in the hydrogen peroxide removal device according to the present invention, in addition to the ion exchanger carrying a metal catalyst, the hydrogen peroxide removal chamber 23 may be filled with an ion exchanger that does not carry a metal catalyst. Since the effect of the present invention is believed to be due to the degree of physical adhesion between the ion exchangers, the filling rate in the case where an ion exchanger carrying a metal catalyst and an ion exchanger not carrying a metal catalyst coexist is determined based on the total free-state volume of the ion exchangers removed from the hydrogen peroxide removal chamber 23. Various hydrogen peroxide removal devices based on the present invention will be described below, and in all of them, the filling rate of the ion exchanger in the hydrogen peroxide removal chamber 23 is 95% or more and 125% or less.

Figure 2 shows an example of the configuration shown in Figure 1, in which the anode chamber 21 is filled with a cation exchange resin (CER), the concentration chambers 22 and 24 and the cathode chamber 25 are filled with anion exchange resin (AER), and the hydrogen peroxide removal chamber 23 is filled with anion exchange resin (Cat. AER) carrying a platinum group metal catalyst.

Figure 3 shows an example of the hydrogen peroxide removal device shown in Figure 2, in which treated water from which hydrogen peroxide has been removed in the hydrogen peroxide removal chamber 23 is used as the supply water to the anode chamber 21, the first concentration chamber 22, the second concentration chamber 24, and the cathode chamber 25. A portion of the treated water obtained from the hydrogen peroxide removal chamber 23 is passed through the first concentration chamber 22 and the second concentration chamber 24, and discharged as concentrated water. In addition, a portion of the treated water is passed through the cathode chamber 25, and the discharged electrode water is further passed through the anode chamber 21. By using the treated water from which hydrogen peroxide has been removed as the supply water to be passed through the concentration chambers and the electrode chambers, the risk of oxidative deterioration of the ion exchangers contained in the concentration chambers and the electrode chambers is reduced.

In the hydrogen peroxide removal device of the first embodiment, in addition to the anion exchanger (Cat. AER) carrying a platinum group metal catalyst, an ion exchanger not carrying a metal catalyst can be filled in the hydrogen peroxide removal chamber 23. Such an example will be described below. When filling the hydrogen peroxide removal chamber 23 with an ion exchanger not carrying a metal catalyst, it is preferable to determine the arrangement of each ion exchanger so that the ion exchanger carrying a metal catalyst is placed in contact with the inlet of the water to be treated in the hydrogen peroxide removal chamber 23 so that the ion exchanger is not deteriorated by hydrogen peroxide. In the following description, an anion exchange resin carrying a platinum group metal catalyst is also called a catalyst-carrying anion exchange resin (Cat. AER). When simply referring to an anion exchange resin (AER) and a cation exchange resin (CER), they refer to an anion exchange resin not carrying a metal catalyst and a cation exchange resin, respectively.

In the hydrogen peroxide removal device shown in FIG. 4, the hydrogen peroxide removal chamber 23 is filled with a mixture of a catalyst-supported anion exchange resin (Cat. AER) and an anion exchange resin (AER). Note that a cation exchange resin (CER) may be filled in place of the anion exchange resin (AER). In this configuration, the amount of expensive platinum group metal catalyst used can be reduced compared to when only a catalyst-supported anion exchange resin (Cat. AER) is filled in the hydrogen peroxide removal chamber 23, thereby reducing costs.

In the hydrogen peroxide removal device shown in FIG. 5, a layer of catalyst-supported anion exchange resin (Cat. AER) and a layer of anion exchange resin (AER) are filled in the hydrogen peroxide removal chamber 23 in a multi-layered bed configuration in which these layers are alternately arranged so that the layer of catalyst-supported anion exchange resin (Cat. AER) is upstream along the water flow. In this hydrogen peroxide removal device, hydrogen peroxide is decomposed and removed near the inlet of the water to be treated in the hydrogen peroxide removal chamber 23, and desalination of anions is performed throughout the hydrogen peroxide removal chamber 23.

The hydrogen peroxide removal device shown in FIG. 6 is the same as the hydrogen peroxide removal device shown in FIG. 5, except that the hydrogen peroxide removal chamber 23 is filled with cation exchange resin (CER) instead of anion exchange resin (AER). Therefore, in the hydrogen peroxide removal chamber 23, a layer of catalyst-supported anion exchange resin (Cat. AER) and a layer of cation exchange resin (CER) are filled in a multi-layered bed configuration, with the layer of catalyst-supported anion exchange resin (Cat. AER) being upstream along the water flow. In this hydrogen peroxide removal device, hydrogen peroxide is decomposed and removed near the inlet of the water to be treated in the hydrogen peroxide removal chamber 23, and desalination of anions and cations is performed overall.

In the hydrogen peroxide removal device shown in FIG. 7, a layer of catalyst-supported anion exchange resin (Cat. AER), a layer of cation exchange resin (CER), and a layer of anion exchange resin (AER) are packed in the hydrogen peroxide removal chamber 23 in this order from the upstream side along the water flow in a multi-layered bed configuration. In the hydrogen peroxide removal chamber 23 of this hydrogen peroxide removal device, hydrogen peroxide is removed and both anions and cations are desalted, and at the same time, the respective ion exchange resins are regenerated.

In the hydrogen peroxide removal device described with reference to Figures 5 to 7, by making the hydrogen peroxide removal chamber 23 into a multi-layered bed configuration, the amount of expensive platinum group metal catalyst used can be reduced compared to when only catalyst-supported anion exchange resin (Cat. AER) is filled in the hydrogen peroxide removal chamber 23, thereby reducing costs.

As mentioned above, the anode chamber can function as a concentration chamber without providing a concentration chamber adjacent to the anode chamber, and similarly, the cathode chamber can function as a concentration chamber without providing a concentration chamber adjacent to the cathode chamber. In the hydrogen peroxide removal device shown in FIG. 8, the anode 11, the anode chamber 26, the anion exchange membrane 32, the hydrogen peroxide removal chamber 23, the cation exchange membrane 33, the cathode chamber 27, and the cathode 12 are arranged in this order. Both the anode chamber 26 and the cathode chamber 27 function as concentration chambers. The anode chamber 26 is filled with an anion exchange resin (AER) or a cation exchange resin (CER), the hydrogen peroxide removal chamber 23 is filled with a catalyst-supported anion exchange resin (Cat. AER), and the cathode chamber 27 is filled with an anion exchange resin (AER) or a cation exchange resin (CER). This hydrogen peroxide removal device is the same as the hydrogen peroxide removal device shown in FIG. 2, except that the anode chamber 26 and the cathode chamber 27 each have the functions of the concentration chambers 22 and 24, and instead, the concentration chambers 22 and 24 are not provided. Therefore, the hydrogen peroxide removal device shown in FIG. 8 operates in the same way as the hydrogen peroxide removal device shown in FIG. 2.

Second Embodiment
Next, a hydrogen peroxide removal device according to a second embodiment of the present invention will be described. In the hydrogen peroxide removal device according to the first embodiment, a desalination chamber is provided adjacent to the hydrogen peroxide removal chamber 23 on the cathode or anode side of the hydrogen peroxide removal chamber 23 between the anode 11 and the cathode 12 via an intermediate ion exchange membrane, and treated water obtained by passing the water to be treated through the hydrogen peroxide removal chamber is passed through the desalination chamber. The desalination chamber is filled with an ion exchanger. With this configuration, removal of hydrogen peroxide from the water to be treated and desalination can be performed simultaneously, making it possible to produce pure water and ultrapure water of high purity. The intermediate ion exchange membrane may be an anion exchange membrane or a cation exchange membrane, or may be a composite membrane such as a bipolar membrane.

Figure 9 shows a hydrogen peroxide device of the second embodiment. The illustrated hydrogen peroxide removal device has an intermediate ion exchange membrane 36 instead of the second ion exchange membrane of the hydrogen peroxide removal device shown in Figure 1. A desalination chamber 28 filled with an ion exchanger is provided on the cathode 12 side of the intermediate ion exchange membrane 36, and a second ion exchange membrane is disposed between the desalination chamber 28 and the cathode chamber 25, and treated water treated in the hydrogen peroxide removal chamber 23 is passed through the desalination chamber 28. The filling rate of the ion exchanger in the hydrogen peroxide removal chamber 23 is 95% or more and 125% or less, as in the first embodiment. In the diagram, the anode 11, anode chamber 21, cation exchange membrane 31, first concentration chamber 22, anion exchange membrane 32, hydrogen peroxide removal chamber 23, intermediate ion exchange membrane 36, desalting chamber 28, cation exchange membrane 33, second concentration chamber 24, anion exchange membrane 34, cathode chamber 25, and cathode 12 are arranged in this order.

Figure 10 shows one specific example of the hydrogen peroxide removal device of the second embodiment. The hydrogen peroxide removal device shown in Figure 10 is the hydrogen peroxide removal device shown in Figure 2, in which a desalting chamber 28 is arranged between the hydrogen peroxide removal chamber 23 and the second concentration chamber 24. The hydrogen peroxide removal chamber 23 and the desalting chamber 28 are separated by a cation exchange membrane 35, which is an intermediate ion exchange membrane, and the desalting chamber 28 and the second concentration chamber 24 are separated by a cation exchange membrane 33, which is a second ion exchange membrane. The water to be treated is supplied to the hydrogen peroxide removal chamber 23, where hydrogen peroxide is decomposed and removed, and then passed through the desalting chamber 28. The desalting chamber 28 discharges treated water from which hydrogen peroxide has been removed and desalted. In the hydrogen peroxide removal device shown in FIG. 10, the anion exchange membrane 32 to the second concentration chamber 24 are defined as a repeating unit X, and multiple sets of repeating units X can be provided in series between the first concentration chamber 22 adjacent to the anode chamber 21 and the anion exchange membrane 34 in contact with the cathode chamber 25.

The hydrogen peroxide removal device shown in FIG. 11 differs from the hydrogen peroxide removal device shown in FIG. 10 in that the desalting chamber 28 is filled with anion exchange resin and cation exchange resin in a mixed bed (MB) form. In FIG. 11, the intermediate ion exchange membrane that separates the hydrogen peroxide removal chamber 23 and the desalting chamber 28 is composed of anion exchange membrane 37.

The hydrogen peroxide removal device shown in FIG. 12 differs from the hydrogen peroxide removal device shown in FIG. 10 in that it uses an anion exchange membrane 37 as an intermediate ion exchange membrane separating the hydrogen peroxide removal chamber 23 and the deionization chamber 28, and in that the deionization chamber 28 is filled with a multi-layered bed configuration in which layers of cation exchange resin (CER) and layers of anion exchange resin (AER) are alternately arranged in this order along the water flow direction. The deionization chamber 28 and the concentration chamber 24 on the cathode 12 side are separated by a cation exchange membrane 33.

The hydrogen peroxide removal device shown in FIG. 13 is the hydrogen peroxide removal device shown in FIG. 12, except that an auxiliary hydrogen peroxide removal chamber 29 is placed between the concentration chamber 24 and the cathode chamber 25 on the cathode 12 side. This hydrogen peroxide removal chamber 29 is also filled with an anion exchanger (Cat. AER) carrying a platinum group metal catalyst so that the filling rate is 95% or more and 125% or less, and the water to be treated is supplied to it. The water discharged from the hydrogen peroxide removal chamber 29 is merged with the water discharged from the hydrogen peroxide removal chamber 23 and supplied to the deionization chamber 28. The concentration chamber 24 and the hydrogen peroxide removal chamber 29 are adjacent to each other with an anion exchange membrane 34 in between, and the hydrogen peroxide removal chamber 29 and the cathode chamber 25 are adjacent to each other with an anion exchange membrane 38 in between. The hydrogen peroxide removal device shown in FIG. 13 has multiple hydrogen peroxide removal chambers 23 and 29, so that hydrogen peroxide can be removed more efficiently.

[Third embodiment]
In the hydrogen peroxide removal device of the first embodiment, the hydroxide ions used to regenerate the ion exchanger in the hydrogen peroxide removal chamber 23 are generated by a dissociation reaction of water that occurs at the contact point between the anion exchange resin and the cation exchange membrane, or at the contact point between the anion exchange resin and the cation exchange resin. Since the contact area between the ion exchange resin and the ion exchange membrane and the contact area between the ion exchange resins are small, the amount of hydroxide ions generated to regenerate the ion exchanger in the hydrogen peroxide removal chamber 23 is also small. If a large amount of hydroxide ions can be supplied to the hydrogen peroxide removal chamber 23, combined with the effect of setting the filling rate of the ion exchanger in the hydrogen peroxide removal chamber 23 to 95% or more and 125%, the regeneration efficiency of the ion exchanger can be further improved and the effective electrical resistance of the hydrogen peroxide removal chamber 23 can be further reduced. Therefore, in the hydrogen peroxide removal device of the third embodiment, a cation exchange membrane and an anion exchange membrane are arranged between the hydrogen peroxide removal chamber 23 and the cathode 12, with the cation exchange membrane on the cathode 12 side and the anion exchange membrane on the hydrogen peroxide removal chamber 23 side. With this configuration, when a direct current voltage is applied between the anode 11 and the cathode 12, a dissociation reaction of water proceeds at the interface between the cation exchange membrane and the anion exchange membrane due to the potential difference caused by the current, and hydroxide ions (OH ⁻ ) are supplied from the anion exchange membrane to the hydrogen peroxide removal chamber. As a result, the electrical resistance between the anode 11 and the cathode 12 becomes smaller, making it possible to pass a large current through the hydrogen peroxide removal chamber at a low voltage, and promoting the regeneration of the ion exchanger in the hydrogen peroxide removal chamber 23. When the cation exchange membrane and the anion exchange membrane are overlapped, they may simply be overlapped, or a bipolar membrane may be configured by arranging a catalyst that promotes the dissociation reaction of water at the interface between the two.

Figure 14 shows the configuration of a hydrogen peroxide removal device of the third embodiment. This hydrogen peroxide removal device is the hydrogen peroxide removal device shown in Figure 1, in which an anion exchange membrane 81 is arranged on the hydrogen peroxide removal chamber 23 side surface of the cation exchange membrane 33 that separates the hydrogen peroxide removal chamber 23 and the second concentration chamber 24, and the anion exchange membrane 81 and the cation exchange membrane 33 are overlapped with each other. Specifically, in the hydrogen peroxide removal device shown in Figure 14, the anode 11 and the cathode 12 face each other, and the anode chamber 21, the first concentration chamber 22, the hydrogen peroxide removal chamber 23, the second concentration chamber 24, and the cathode chamber 25 are arranged in this order from the anode 11 side between the anode 11 and the cathode 12. The anode chamber 21 and the first concentration chamber 22 are separated by the cation exchange membrane 31, and the first concentration chamber 22 and the hydrogen peroxide removal chamber 23 are separated by the anion exchange membrane 32. The hydrogen peroxide removal chamber 23 and the second concentration chamber 24 are separated by an anion exchange membrane 81 and a cation exchange membrane 33 stacked on top of each other. The second concentration chamber 24 and the cathode chamber 25 are separated by an anion exchange membrane 34. The anode chamber 21, the first concentration chamber 22, the second concentration chamber 24, and the cathode chamber 25 are filled with an ion exchanger that does not support a platinum group metal catalyst, as in the hydrogen peroxide removal device shown in FIG. 1. In this embodiment, the filling rate of the ion exchanger in the hydrogen peroxide removal chamber 23 is 95% or more and 125% or less.

Next, the operation of the hydrogen peroxide removal apparatus shown in Fig. 14 will be described. When hydrogen peroxide is removed from water to be treated that contains hydrogen peroxide, as in the case of the apparatus shown in Fig. 1, feed water is passed through the anode chamber 21, the concentration chambers 22, 24, and the cathode chamber 25, respectively, and the water to be treated is passed through the hydrogen peroxide removal chamber 23 with a DC voltage applied between the anode 11 and the cathode 12. When the water to be treated that contains hydrogen peroxide is passed through the hydrogen peroxide removal chamber 23, 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 hydrogen peroxide removal chamber 23, and as a result, treated water from which hydrogen peroxide has been removed flows out from the hydrogen peroxide removal chamber 23. At this time, in the hydrogen peroxide removal chamber 23, a dissociation reaction of water (H ₂ O→H ⁺ +OH ⁻ ) occurs due to a potential difference generated at the interface between different ion exchange materials by the applied current, generating hydrogen ions (H ⁺ ) and hydroxide ions (OH ⁻ ). The hydrogen ions and hydroxide ions exchange the ionic components previously adsorbed on the ion exchanger in the hydrogen peroxide removal chamber 23, causing them to be desorbed from the ion exchanger. Among the desorbed ionic components, anions move through the anion exchange membrane 32 to the first concentration chamber 22 closer to the anode 11, and are discharged from the first concentration chamber 22 as concentrated water. At the same time, the ion exchanger in the hydrogen peroxide removal chamber 23 is also regenerated. Electrode water is discharged from the anode chamber 21 and the cathode chamber 25. The application of the DC voltage may be performed continuously or intermittently while the water to be treated is passing through the chamber.

In the hydrogen peroxide removal device shown in FIG. 14, the water dissociation reaction proceeds efficiently at the interface between the anion exchange membrane 81 and the cation exchange membrane 33, and a large amount of hydroxide ions are supplied to the hydrogen peroxide removal chamber 23 through the anion exchange membrane 81. By supplying a large amount of hydroxide ions, the effective electrical resistance of the hydrogen peroxide removal chamber 23 can be reduced, and the DC voltage applied between the anode 11 and the cathode 12 for electrical regeneration of the anion exchanger in the hydrogen peroxide removal chamber 23 can also be reduced.

In the configuration shown in FIG. 14, a repeating unit X is configured as a structure consisting of [anion exchange membrane (AEM) 32 | hydrogen peroxide removal chamber (H) 23 | anion exchange membrane (AEM) 81 | cation exchange membrane (CEM) 33 | concentration chamber (C) 24], and multiple sets of repeating units X can be provided in series between the concentration chamber 22 adjacent to the anode chamber 21 and the anion exchange membrane 34 that divides the cathode chamber 25. In such a series structure, the anode chamber 21 itself can function as the concentration chamber 22 for the hydrogen peroxide removal chamber 23 closest to the anode chamber 21 without interposing an independent concentration chamber 22 between the anode chamber 21 and the anode chamber 21. Similarly, the cathode chamber 25 itself can function as the concentration chamber 24 for the hydrogen peroxide removal chamber 23 closest to the cathode chamber 25 without interposing an independent concentration chamber 24 between the cathode chamber 25 and the anode chamber 25.

Figure 15 shows an example in which the anode chamber 21 is filled with a cation exchange resin (CER), the concentration chambers 22, 24 and the cathode chamber 25 are filled with an anion exchange resin (AER), and the hydrogen peroxide removal chamber 23 is filled with a catalyst-supported anion exchange resin (Cat. AER) in the configuration shown in Figure 14. In other words, the hydrogen peroxide removal device shown in Figure 15 is the device shown in Figure 2 in which an anion exchange membrane 81 is arranged on the surface of the hydrogen peroxide removal chamber 23 side of the cation exchange membrane 33 that separates the hydrogen peroxide removal chamber 23 and the concentration chamber 24, and the anion exchange membrane 81 and the cation exchange membrane 33 are overlapped with each other. When the TOC components in the water to be treated are decomposed and removed by the ultraviolet oxidation device, the water discharged from the ultraviolet oxidation device contains carbonic acid components and a small amount of hydrogen peroxide. When such water is treated as the water to be treated and hydrogen peroxide is decomposed and removed from the water to be treated, it is preferable to be able to remove the carbonic acid components as well as the hydrogen peroxide. In the apparatus shown in FIG. 15, hydroxide ions produced by the water dissociation reaction are supplied through the anion exchange membrane 81, so that the hydrogen peroxide removal chamber 23 becomes a basic environment, and the carbonic acid components in the water to be treated are adsorbed onto the anion exchanger as carbonate ions or bicarbonate ions, and then ion-exchanged by the hydroxide ions and move to the concentration chamber 22 through the anion exchange membrane 32. Regeneration of the anion exchanger by the hydroxide ions is also promoted. Therefore, in the hydrogen peroxide removal apparatus shown in FIG. 15, hydrogen peroxide in the water to be treated can be decomposed and removed, and carbonic acid components can also be removed from the water to be treated. In the hydrogen peroxide removal apparatus shown in FIG. 15, as in the apparatus shown in FIG. 3, the treated water after hydrogen peroxide removal in the hydrogen peroxide removal chamber 23 can be used as the supply water to the anode chamber 21, the first concentration chamber 22, the second concentration chamber 24, and the cathode chamber 25. Specifically, a portion of the treated water obtained from the hydrogen peroxide removal chamber 23 is passed through the concentration chambers 22 and 24, and each is discharged as concentrated water. Also, a portion of the treated water is passed through the cathode chamber 25, and the discharged electrode water is further passed through the anode chamber 21.

Figure 16 is a diagram specifically showing the operation of the hydrogen peroxide removal device shown in Figure 15, showing the hydrogen peroxide removal chamber 23 and its vicinity. As shown by the arrows, the flow of water is in the opposite direction between the hydrogen peroxide removal chamber 23 and the concentration chambers 22 and 24 on both sides of the hydrogen peroxide removal chamber 23. Here, the platinum group metal catalyst is made of palladium (Pd), and granular anion exchange resin (Pd AER) carrying the palladium catalyst is filled in the hydrogen peroxide removal chamber 23 as an anion exchanger. The concentration chambers 22 and 24 are filled with granular anion exchange resin not carrying a metal catalyst as an anion exchanger. As shown in the figure, when a direct current is applied between the anode 11 and the cathode 12, a dissociation reaction of water proceeds at the interface between the anion exchange membrane 81 and the cation exchange membrane 33 due to the potential difference generated by the current, generating hydrogen ions and hydroxide ions. The hydrogen ions move to the concentration chamber 24 through the cation exchange membrane 33, and the hydroxide ions move to the hydrogen peroxide removal chamber 23 through the anion exchange membrane 81. In the following description, granular anion exchange resin (Pd AER) carrying a palladium catalyst is also referred to as Pd-loaded anion exchange resin (Pd AER).

In the hydrogen peroxide removal device of the third embodiment, as in the device of the first embodiment, in addition to the anion exchanger (Cat. AER) carrying a platinum group metal catalyst, an ion exchanger not carrying a metal catalyst can be filled into the hydrogen peroxide removal chamber 23. Such an example will be described below.

The hydrogen peroxide removal device shown in FIG. 17 is the same as the device shown in FIG. 4, except that an anion exchange membrane 81 is placed on the hydrogen peroxide removal chamber 23 side of the cation exchange membrane 33 that separates the hydrogen peroxide removal chamber 23 from the concentration chamber 24, and the anion exchange membrane 81 and the cation exchange membrane 33 are overlapped. Even with this configuration, the amount of expensive platinum group metal catalyst used can be reduced, resulting in reduced costs.

The hydrogen peroxide removal device shown in Fig. 18 is the device shown in Fig. 5, in which an anion exchange membrane 81 is placed on the hydrogen peroxide removal chamber 23 side of the cation exchange membrane 33 that separates the hydrogen peroxide removal chamber 23 and the concentration chamber 24, and the anion exchange membrane 81 and the cation exchange membrane 33 are overlapped with each other. In this hydrogen peroxide removal device, as in the case described with reference to Fig. 16, when a direct current is applied between the anode 11 and the cathode 12, a dissociation reaction of water proceeds at the interface between the anion exchange membrane 81 and the cation exchange membrane 33 due to the potential difference caused by the current, generating hydrogen ions and hydroxide ions. The hydroxide ions move from the anion exchange membrane 81 to both the layer of Pd-supported anion exchange resin (Pd AER) and the layer of anion exchange resin (AER) that does not support a metal catalyst. In this hydrogen peroxide removal device, hydrogen peroxide is decomposed and removed near the inlet of the water to be treated in the hydrogen peroxide removal chamber 23, and anions are desalted throughout the hydrogen peroxide removal chamber 23.

The hydrogen peroxide removal device shown in Figure 19 is the hydrogen peroxide removal device shown in Figure 18, in which the hydrogen peroxide removal chamber 23 is filled with a cation exchange resin (CER) instead of an anion exchange resin (AER). Therefore, in the hydrogen peroxide removal chamber 23, a layer of catalyst-supported anion exchange resin (Cat. AER) and a layer of cation exchange resin (CER) are filled in a multi-layered bed configuration so that the layer of catalyst-supported anion exchange resin (Cat. AER) is upstream along the water flow. In this multi-layered bed configuration, the anion exchange membrane 81 is not provided at the position where the cation exchange resin (CER) is formed, and the cation exchange resin (CER) and the cation exchange membrane 33 are in direct contact with each other. In this hydrogen peroxide removal device, when a direct current is applied between the anode 11 and the cathode 12, a potential difference caused by the current causes a water dissociation reaction to proceed at the interface between the anion exchange membrane 81 and the cation exchange membrane 33, generating hydrogen ions and hydroxide ions. The hydrogen ions move to the concentration chamber 24 via the cation exchange membrane 33, and the hydroxide ions move to the hydrogen peroxide removal chamber 23 via the anion exchange membrane 81. Water is also dissociated at the interface between the anion exchange membrane 32 and the cation exchange resin (CER) in the hydrogen peroxide removal chamber 23, generating hydrogen ions and hydroxide ions. The hydrogen ions diffuse through the cation exchange resin (CER) to regenerate the cation exchange resin (CER). Cations desorbed from the cation exchange resin (CER) in the hydrogen peroxide removal chamber 23 move to the concentration chamber 24 on the cathode 12 side through the cation exchange resin (CER) at a position not overlapping with the anion exchange membrane 81. Therefore, in the hydrogen peroxide removal device shown in FIG. 19, hydrogen peroxide is removed and both anions and cations are desalted in the hydrogen peroxide removal chamber 23, while at the same time regenerating both the catalyst-supported anion exchange resin (Cat. AER) and the cation exchange resin (CER).

The hydrogen peroxide removal device shown in FIG. 20 is the hydrogen peroxide removal device shown in FIG. 15, in which a layer of catalyst-supported anion exchange resin (Cat. AER), a layer of cation exchange resin (CER), and a layer of anion exchange resin (AER) are filled in the hydrogen peroxide removal chamber 23 in this order from the upstream side along the water flow in a multi-layered bed configuration. The anion exchange membrane 81, which overlaps with the cation exchange membrane 33, is only provided at the position where the layer of catalyst-supported anion exchange resin (Cat. AER) is formed. The cation exchange resin (CER) and the anion exchange resin (AER) are in direct contact with the cation exchange membrane 33. When a direct current is applied between the anode 11 and the cathode 12, the potential difference generated by the current causes a water dissociation reaction to proceed at the interface between the anion exchange membrane 81 and the cation exchange membrane 33, generating hydrogen ions and hydroxide ions. The hydroxide ions move from the anion exchange membrane 81 to the layer of the Pd-loaded anion exchange resin (Pd AER). At the same time, water dissociates at the interface between the anion exchange membrane 32 and the cation exchange resin (CER) in the hydrogen peroxide removal chamber 23, and at the interface between the anion exchange resin (AER) in the hydrogen peroxide removal chamber 23 and the cation exchange membrane 33, generating hydrogen ions and hydroxide ions. The hydrogen ions generated at the interface with the anion exchange membrane 32 diffuse within the cation exchange resin (CER) and regenerate the cation exchange resin (CER). The hydroxide ions generated at the interface with the cation exchange membrane 33 diffuse within the anion exchange resin (AER) and regenerate the anion exchange resin (AER). In the hydrogen peroxide removal chamber 23 of this hydrogen peroxide removal device, removal of hydrogen peroxide and desalination of both anions and cations are also performed, and at the same time, regeneration of each ion exchange resin is performed. In the hydrogen peroxide removal device shown in FIG. 20, the anion exchange membrane 81 that overlaps with the cation exchange membrane 33 may be provided not only at the position where the catalyst-supported anion exchange resin (Cat. AER) layer is formed, but also at the position where the anion exchange resin (AER) is formed.

In the hydrogen peroxide removal device described using Figures 18 to 20, by making the hydrogen peroxide removal chamber 23 into a multi-layered bed configuration, the amount of expensive platinum group metal catalyst used can be reduced compared to when only catalyst-supported anion exchange resin (Cat. AER) is filled in the hydrogen peroxide removal chamber 23, thereby reducing costs.

The hydrogen peroxide removal device shown in FIG. 21 is the hydrogen peroxide removal device shown in FIG. 8, except that an anion exchange membrane 81 is placed on the hydrogen peroxide removal chamber 23 side of the cation exchange membrane 33 that separates the hydrogen peroxide removal chamber 23 from the cathode chamber 27, and the anion exchange membrane 81 and the cation exchange membrane 33 are overlapped with each other. This hydrogen peroxide removal device is the same as the hydrogen peroxide removal device shown in FIG. 15, except that the anode chamber 26 and the cathode chamber 27 each have the functions of the concentration chambers 22 and 24, and instead, the concentration chambers 22 and 24 are not provided. Therefore, the hydrogen peroxide removal device shown in FIG. 21 operates in the same way as the hydrogen peroxide removal device shown in FIG. 15.

[Fourth embodiment]
Next, a hydrogen peroxide removal device according to a fourth embodiment of the present invention will be described. In the fourth hydrogen peroxide removal device, in order to increase the amount of hydroxide ions supplied to the hydrogen peroxide removal chamber 23 in the hydrogen peroxide removal device according to the second embodiment described above, a cation exchange membrane and an anion exchange membrane are arranged between the hydrogen peroxide removal chamber 23 and the cathode 12, with the cation exchange membrane on the cathode 12 side and the anion exchange membrane on the hydrogen peroxide removal chamber 23 side. In this case, the intermediate ion exchange membrane itself separating the hydrogen peroxide removal chamber 23 and the desalting chamber 28 may be an anion exchange membrane and a cation exchange membrane overlapped with each other, with the anion exchange membrane on the hydrogen peroxide removal chamber 23 side. Alternatively, when the desalting chamber 28 is filled with at least an anion exchange resin, the intermediate ion exchange membrane may be an anion exchange membrane, and the desalting chamber 28 may be partitioned by an anion exchange membrane and a cation exchange membrane overlapped with each other, with the anion exchange membrane on the cathode 12 side and the anion exchange membrane on the hydrogen peroxide removal chamber 23 side. In this embodiment as well, the filling rate of the ion exchanger in the hydrogen peroxide removal chamber 23 is 95% or more and 125% or less.

22 shows a hydrogen peroxide removal device in which an anion exchange membrane 82 and a cation exchange membrane 35 are arranged on the hydrogen peroxide removal chamber 23 side of the cation exchange membrane 35 provided as an intermediate ion exchange membrane in the hydrogen peroxide removal device shown in FIG. 10, so that the anion exchange membrane 82 and the cation exchange membrane 35 are mutually overlapped. In this case, the anion exchange membrane 82 and the cation exchange membrane 35 overlapped with each other correspond to the intermediate ion exchange membrane. The water to be treated is supplied to the hydrogen peroxide removal chamber 23, where hydrogen peroxide is decomposed and removed, and then the water is passed through the desalting chamber 28. The desalting chamber 28 discharges treated water from which hydrogen peroxide has been removed and desalted. In the hydrogen peroxide removal device shown in FIG. 22, the anion exchange membrane 32 to the second concentrating chamber 24 are set as a repeating unit X, and multiple sets of repeating units X can be provided in series between the first concentrating chamber 22 adjacent to the anode chamber 21 and the anion exchange membrane 34 in contact with the cathode chamber 25.

In the hydrogen peroxide removal device shown in FIG. 22, a water dissociation reaction occurs at the interface between the anion exchange membrane 82 and the cation exchange membrane 35 to generate hydrogen ions and hydroxide ions, and these hydroxide ions are supplied to the hydrogen peroxide removal chamber 23, lowering the effective electrical resistance of the hydrogen peroxide removal chamber 23. This also promotes regeneration of the anion exchange resin in the hydrogen peroxide removal chamber 23. This is advantageous for removing anion components, especially carbon dioxide components, along with removing hydrogen peroxide.

The hydrogen peroxide removal device shown in FIG. 23 is the hydrogen peroxide removal device shown in FIG. 11, except that a cation exchange membrane 83 is arranged on the desalting chamber 28 side of the anion exchange membrane 37 provided as an intermediate ion exchange membrane, so that the anion exchange membrane 37 and the cation exchange membrane 83 are overlapped with each other. In the hydrogen peroxide removal device shown in FIG. 23, the anion exchange membrane 37 and the cation exchange membrane 83 overlapped with each other correspond to the intermediate ion exchange membrane.

The hydrogen peroxide removal device shown in Fig. 24 is the same as the hydrogen peroxide removal device shown in Fig. 12, except that an anion exchange membrane 81 and a cation exchange membrane 33 are arranged on the deionization compartment 28 side of the cation exchange membrane 33 that separates the deionization compartment 28 and the concentration compartment 24, so that the anion exchange membrane 81 and the cation exchange membrane 33 are mutually overlapped. However, the anion exchange membrane 81 is provided only at the position in the deionization compartment 28 where the anion exchange resin (AER) is filled, and the cation exchange resin (CER) in the deionization compartment 28 is in direct contact with the cation exchange membrane 33. In this hydrogen peroxide removal device, when a direct current is applied between the anode 11 and the cathode 12, a dissociation reaction of water proceeds at the interface between the anion exchange membrane 81 and the cation exchange membrane 33 due to the potential difference generated by the current, generating hydrogen ions and hydroxide ions. The hydroxide ions diffuse through the anion exchange resin (AER) in the deionization compartment 28 and move to the hydrogen peroxide removal compartment 23 through the anion exchange membrane 37, which is an intermediate ion exchange membrane. In addition, a water dissociation reaction occurs at the interface between the anion exchange membrane 37 and the cation exchange resin (CER) in the deionization chamber 28, generating hydrogen ions and hydroxide ions, which diffuse through the cation exchange resin (CER). As the hydrogen ions diffuse, the region in the deionization chamber 28 filled with the cation exchange resin (CER) becomes an acidic environment, and the carbonate components in the water to be treated become free carbon dioxide (CO ₂ ). This free carbon dioxide reaches the region in the deionization chamber 28 filled with the anion exchange resin (AER), and since this region is in a basic environment, it is adsorbed by the anion exchange resin as carbonate ions or bicarbonate ions (hydrogen carbonate ions), and then moves through the anion exchange membrane 37, the hydrogen peroxide removal chamber 23, and the anion exchange membrane 32 to the concentration chamber 22.

The hydrogen peroxide removal device shown in FIG. 25 is the hydrogen peroxide removal device shown in FIG. 24, in which the hydrogen peroxide removal chamber 23 and the desalination chamber 28 are interchanged, with the anion exchange membrane 37, which is an intermediate ion exchange membrane, sandwiched between the anode 11 side and the hydrogen peroxide removal chamber 23 on the cathode 12 side. In the hydrogen peroxide removal chamber 23, a catalyst-supported anion exchange resin (Cat. AER) is disposed on the inlet side of the water to be treated, and a cation exchange resin (CER) is disposed on the outlet side. The hydrogen peroxide removal chamber 23 and the concentration chamber 24 on the cathode 12 side are partitioned by a cation exchange membrane 33, but at the position where the catalyst-supported anion exchange resin (Cat. AER) is provided, an anion exchange membrane 81 is superimposed on the anode side 11 of the cation exchange membrane 33, and the layer of the catalyst-supported anion exchange resin (Cat. AER) is in contact with the anion exchange membrane 81. The layer of cation exchange resin (CER) is in direct contact with the cation exchange membrane 33. The deionization chamber 28 is filled with anion exchange resin (AER). The water to be treated passes through the hydrogen peroxide removal chamber 23 and is then supplied to the deionization chamber 28, from which hydrogen peroxide is removed and desalted treated water is discharged. In this hydrogen peroxide removal device, when a direct current is applied between the anode 11 and the cathode 12, a potential difference caused by the current causes a dissociation reaction of water to proceed at the interface between the anion exchange membrane 81 and the cation exchange membrane 33, generating hydrogen ions and hydroxide ions. The hydroxide ions are supplied to the layer of Pd-supported anion exchange resin (AER) in the hydrogen peroxide removal chamber 23. The water dissociation reaction also proceeds at the interface between the anion exchange membrane 37, which is an intermediate ion exchange membrane, and the cation exchange resin (CER) in the hydrogen peroxide removal chamber 23, and the hydrogen ions generated at this time are supplied to the cation exchange resin (CER) in the hydrogen peroxide removal chamber 23.

The hydrogen peroxide removal device shown in FIG. 26 is the hydrogen peroxide removal device shown in FIG. 24, except that an auxiliary hydrogen peroxide removal chamber 29 is placed between the concentration chamber 24 and the cathode chamber 25 on the cathode 12 side. This hydrogen peroxide removal chamber 29 is also filled with an anion exchanger (Cat. AER) carrying a platinum group metal catalyst, and the water to be treated is supplied to it. The water discharged from the hydrogen peroxide removal chamber 29 is combined with the water discharged from the hydrogen peroxide removal chamber 23 and supplied to the deionization chamber 28. The concentration chamber 24 and the hydrogen peroxide removal chamber 29 are adjacent to each other with an anion exchange membrane 34 in between, and the hydrogen peroxide removal chamber 29 and the cathode chamber 25 are adjacent to each other with an anion exchange membrane 38 in between. The hydrogen peroxide removal device shown in FIG. 26 has multiple hydrogen peroxide removal chambers 23 and 29, so that hydrogen peroxide can be removed more efficiently.

The anion exchanger used in the hydrogen peroxide removal device according to the present invention is not particularly limited, regardless of whether it is used to support a metal catalyst or not, and is preferably a monolithic porous anion exchanger or an anion exchange resin. The anion exchange membrane is not particularly limited, but for example, a homogeneous anion exchange membrane or a heterogeneous anion exchange membrane is preferably used. The cation exchanger is not particularly limited, but for example, a monolithic porous cation exchanger or a cation exchange resin is preferably used. The cation exchange membrane is not particularly limited, but for example, a homogeneous cation exchange membrane or a heterogeneous cation exchange membrane is preferably used. In addition, the intermediate ion exchange membrane is not particularly limited, but for example, a homogeneous anion exchange membrane or a heterogeneous anion exchange membrane, a homogeneous cation exchange membrane or a heterogeneous cation exchange membrane, a bipolar membrane, etc. are preferably used.

The parent resin for the anion exchange resin or cation exchange resin is not particularly limited, but is preferably an organic polymer with a three-dimensional network structure. For example, examples of the parent organic polymer include styrene-divinylbenzene copolymers (styrene-based) and acrylic acid-divinylbenzene copolymers (acrylic-based).

Furthermore, the types of anion exchangers include weakly basic anion exchangers and strongly basic anion exchangers. The types of cation exchangers include weakly acidic cation exchangers and strongly acidic cation exchangers. The ion exchangers carrying a platinum group metal catalyst used in the present invention are those in which particles of a platinum group metal catalyst are carried on the above-mentioned cation exchangers and anion exchangers.

There are no particular limitations on the method of producing the ion exchanger carrying the platinum group metal catalyst used in the present invention, and the ion exchanger carrying the platinum group metal catalyst can be obtained by carrying platinum group metal particles on the ion exchanger by a known method. For example, there is a method in which the anion exchanger is immersed in an aqueous hydrochloric acid solution of palladium chloride, the chloropalladate anions are adsorbed on the anion exchanger by ion exchange, and then the anion exchanger is contacted with a reducing agent to carry palladium metal nanoparticles on the anion exchanger. Alternatively, there is a method in which the anion exchanger is packed in a column, an aqueous hydrochloric acid solution of palladium chloride is passed through the column to adsorb the chloropalladate anions on the anion exchanger by ion exchange, and then the reducing agent is passed through the column to carry palladium metal nanoparticles on the anion exchanger. There are no particular limitations on the reducing agent used in these methods, 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.

The water to be treated that is supplied to the hydrogen peroxide removal device according to the present invention is not particularly limited as long as it contains hydrogen peroxide, and the hydrogen peroxide concentration may be, for example, 1 μg/L or more, 5 μg/L or more, 10 μg/L or more, 100 μg/L or more, or 1000 μg/L or more. The water to be treated may also contain a carbonate component. Here, the carbonate component refers to H ₂ CO ₃ , HCO ₃ ^- , and CO ₃ ^2- . The carbonate component is generated, for example, when TOC components are decomposed and removed by an ultraviolet oxidation device. In this specification, the total amount of these carbonate components is referred to as "total carbonate," and the concentration is expressed as a CO ₂ equivalent concentration (as CO ₂ ). The total carbon dioxide concentration of the water to be treated is not particularly limited, but may be, for example, 0.01 mg/L (as _CO2 ) or more, 0.1 mg/L (as _CO2 ) or more, or 1.0 mg/L (as _CO2 ) or more. The conductivity of the water to be treated is also not particularly limited, but may be, for example, 0.1 μS/cm or more, or 1 μS/cm or more. The water to be treated may also contain salt components such as sodium. The concentration of sodium contained in the water to be treated is not particularly limited, but may be, for example, 1 μg/L or more, 10 μg/L or more, or 100 μg/L or more.

In the present invention, the space velocity of the water to be treated relative to the packed volume of the ion exchanger supporting a platinum group metal catalyst is not particularly limited as long as hydrogen peroxide can be removed, and examples of such a space velocity include 10 h ^-1 or more, 100 h ^-1 or more, and 200 h ^-1 or more. There is also no particular limitation on the removal rate of hydrogen peroxide removed from the water to be treated, and examples of such a space velocity include 60% or more, 80% or more, 90% or more, and 95% or more.

In the present invention, the thickness of the hydrogen peroxide removal chamber 23 is preferably 9 mm or more and 30 mm or less. Here, the thickness of the hydrogen peroxide removal chamber 23 refers to the size of the hydrogen peroxide removal chamber 23 along the voltage application direction when a DC voltage is applied between the anode 11 and the cathode 12, and the thickness direction of the hydrogen peroxide removal chamber 23 is generally perpendicular to the flow direction of the water to be treated in the hydrogen peroxide removal chamber 23. If the thickness of the hydrogen peroxide removal chamber 23 is too thin, the flow rate of the water to be treated that can be treated becomes too small. On the other hand, if the thickness of the hydrogen peroxide removal chamber 23 is too thick, the DC voltage to be applied between the anode 11 and the cathode 12 becomes excessively high, and the amount of hydroxide ions and hydrogen ions generated by dissociation of water is insufficient compared to the amount of the ion exchanger, so that electrical regeneration of the ion exchanger in the hydrogen peroxide removal chamber 23 is not performed sufficiently.

The hydrogen peroxide removal device according to the present invention can be incorporated, for example, into a pure water production system or an ultrapure water production system. Below, we will explain the pure water production system and the ultrapure water production system that incorporate the hydrogen peroxide removal device according to the present invention.

Figure 27 shows an example of the configuration of a pure water production system in the prior art. In this pure water production system, a raw water tank 41 for storing raw water, a first reverse osmosis membrane device 51, a second reverse osmosis membrane device 52, a reverse osmosis membrane treated water tank 42, an electric regenerative deionization device (EDI) 54, an EDI treated water tank 43, an ultraviolet oxidation device (UV) 55, a non-regenerative ion exchange resin (CP) 56, and a degassing membrane (MD) 58 are arranged in this order, and the raw water is treated in this order. As a result, pure water is finally produced. In this pure water production system, when the equipment in the latter stage is full of water, a circulation operation is performed within the system, but there is a risk that the ion exchanger in the electric regenerative deionization device 54 will be oxidized and deteriorated by hydrogen peroxide generated by the ultraviolet oxidation device 55. Therefore, when circulating within the system, it is necessary to circulate the produced pure water to the EDI treated water tank 43 and circulate the treated water of the electrical deionization device 54 to the reverse osmosis membrane treated water tank 42 so that the treated water of the ultraviolet oxidation device 55 is not circulated to the electrical deionization device 54. Such a pure water production system requires multiple lines and EDI treated water tanks for circulation, resulting in a complex configuration.

Figure 28 shows an example of the configuration of a pure water production system equipped with a hydrogen peroxide removal device based on the present invention. In the illustrated pure water production system 300, a raw water tank 41, a first reverse osmosis membrane device 51, a second reverse osmosis membrane device 52, a reverse osmosis membrane treated water tank 42, an ultraviolet oxidation device (UV) 55, a hydrogen peroxide removal device 100, an electric deionization device (EDI) 54, and a degassing membrane (MD) 58 are arranged in this order, and the raw water is treated in this order, resulting in the production of pure water. The hydrogen peroxide removal device 100 used here may be any hydrogen peroxide removal device based on the present invention, but it is preferable to use any of the hydrogen peroxide removal devices shown in Figures 1 to 26. In this pure water production system, when the downstream equipment to which the pure water is supplied becomes full, the produced pure water is circulated to the reverse osmosis membrane treated water tank 42. That is, by arranging the hydrogen peroxide removal device 100 after the ultraviolet oxidation device 55, it is possible to avoid the influence of hydrogen peroxide generated by the ultraviolet oxidation device 55 on the electrodeionization device 54. As is clear from the above description, the hydrogen peroxide removal device 100 itself has the same desalination performance as the electrodeionization device, and this configuration makes it possible to obtain pure water of high purity equivalent to that obtained when two electrodeionization devices are arranged in series. Depending on the desalination performance required for the pure water production system, the outlet water of the hydrogen peroxide removal device 100 may be directly supplied to the degassing membrane (MD) 58 without providing the electrodeionization device (EDI) 54. By providing a single system for circulating the treated water, the EDI treated water tank and the EDI treated water circulation line required in the system shown in FIG. 27 are no longer necessary, making it possible to provide a low-cost pure water production system.

28, at least a portion of the treated water from the degassing membrane (MD) 58 is circulated to the reverse osmosis treated water tank 42, but the treated water from the hydrogen peroxide removal device 100 or the electrical deionization device (EDI) 54 may also be circulated to the reverse osmosis treated water tank 42. In addition, water that bypasses the ultraviolet oxidation device 55 may be used as the supply water to be passed through the concentration chamber and electrode chamber of the hydrogen peroxide removal device 100, and this is preferable. By using water that bypasses the ultraviolet oxidation device 55, water with a low hydrogen peroxide concentration or no hydrogen peroxide is supplied to the concentration chamber and electrode chamber, so deterioration of the ion exchanger filled in the concentration chamber and electrode chamber can be suppressed.

In a pure water production system, a carbon dioxide removal means may be provided in front of the hydrogen peroxide removal device. When the amount of carbon dioxide components in the water being treated and supplied to the hydrogen peroxide removal device is reduced, it becomes possible to lower the voltage applied to the hydrogen peroxide removal device, thereby reducing power consumption. Carbon dioxide removal means may include a reverse osmosis (RO) device, the addition of a basic agent to the reverse osmosis device, and, although not shown in FIG. 28, a deaeration membrane (MD), a decarbonation tower, an anion exchange resin tower, etc.

Figure 29 shows an example of the configuration of an ultrapure water production system incorporating a hydrogen peroxide removal device according to the present invention. The illustrated ultrapure water production system 400 uses the pure water production system 300 shown in Figure 28 as a primary pure water system, and further arranges a subsystem to produce ultrapure water. In the subsystem, a pure water tank 45 is provided to store primary pure water from the primary pure water system, and an ultraviolet oxidation device (UV) 61, a non-regenerated ion exchange resin (CP) 63, a degassing membrane (MD) 65, and an ultrafiltration membrane (UF) 67 are arranged in this order at the outlet of the pure water tank 45, and the primary pure water is treated in this order to produce ultrapure water. A part of the produced ultrapure water is circulated to the pure water tank 45. A microfiltration membrane may be used instead of the ultrafiltration membrane (UF) 67. Also, the primary pure water system may be configured without providing an electric regenerative deionization device (EDI) 54.

The ultrapure water production system shown in FIG. 30 is a system in which the order of the ultraviolet oxidation device (UV) 55, hydrogen peroxide removal device 100, and electrical deionization device (EDI) 54 in the primary pure water system of the ultrapure water production system shown in FIG. 29 is changed to the order of electrical deionization device (EDI) 54, ultraviolet oxidation device (UV) 55, and hydrogen peroxide removal device 100. The ultrapure water production system shown in FIG. 31 is a system in which a boron removal device such as a boron-selective ion exchange resin (B IER) 57 or a boron-selective adsorbent is provided in the primary pure water system of the ultrapure water production system shown in FIG. 30, after the electrical deionization device (EDI) 54 and before the ultraviolet oxidation device (UV).

In the ultrapure water production system, the hydrogen peroxide removal device 100 according to the present invention can also be arranged in the subsystem. FIG. 32 shows the ultrapure water production system shown in FIG. 30, in which the hydrogen peroxide removal device 100 is removed from the primary pure water system so that the outlet water of the ultraviolet oxidation device (UV) 55 is directly supplied to the degassing membrane (MD) 58, and the hydrogen peroxide removal device 100 is provided in place of the non-regenerative ion exchange resin (CP) 63 in the subsystem. In the primary pure water system, the non-regenerative ion exchange resin (CP) 56 is provided in place of the hydrogen peroxide removal device 100. Since the hydrogen peroxide removal device 100 can be provided with desalination performance, even if the hydrogen peroxide removal device 100 is provided in place of the non-regenerative ion exchange resin (CP) 63 in the subsystem, the quality of the ultrapure water obtained as the outlet water of the ultrafiltration membrane (UF) 67 does not deteriorate. In the subsystem, the non-regenerative ion exchange resin (CP) 63 may be left as it is and the hydrogen peroxide removal device 100 may be provided. In this way, the non-regenerative ion exchange resin (CP) 63 can remove ionic components that could not be removed by the hydrogen peroxide removal device 100, and furthermore, it can remove hydrogen peroxide that cannot be removed by the non-regenerative ion exchange resin (CP) 63, thereby complementing each other's functions. When both the hydrogen peroxide removal device 100 and the non-regenerative ion exchange resin (CP) 63 are provided in series, water may be passed through the hydrogen peroxide removal device 100 first, or through the non-regenerative ion exchange resin (CP) 63 first.

Next, the present invention will be explained in more detail using examples.

[Example 1]
The hydrogen peroxide removal device shown in Figures 15 and 16 was assembled such that a plurality of hydrogen peroxide removal chambers 23 were arranged between the anode 11 and the cathode 12. A 1 cm thick frame having a 10 cm x 10 cm square opening was prepared, and two of these frames were stacked and filled with regenerated Pd-loaded anion exchange resin (Pd AER) to form a 2 cm thick hydrogen peroxide removal chamber 23. The hydrogen peroxide removal chamber 23 was partitioned on the anode 11 side by an anion exchange membrane 32, and on the cathode 12 side by a membrane in which an anion exchange membrane 81 and a cation exchange membrane 33 were mutually stacked so that the cation exchange membrane 33 was on the cathode 12 side. The electrode chambers (anode chamber 21 and cathode chamber 25) and concentration chambers 22 and 24 were each 1 cm thick by filling them with ion exchangers using the same frame. Water having a conductivity of 1.3 μS/cm, a hydrogen peroxide concentration of 97.5 μg/L, and a total carbonate concentration of 0.103 mg/L (as CO ₂ ) was supplied to the electrode chambers, concentration chambers 22, 24, and hydrogen peroxide removal chamber 23, and a DC voltage was applied between anode 11 and cathode 12 so as to give a current of 1.04 A. The flow rate of water to be treated into hydrogen peroxide removal chamber 23 was set to 88 L/h.

When the system stabilized approximately 1000 hours after water was passed through the hydrogen peroxide removal device and DC voltage was applied, the hydrogen peroxide concentration in the treated water discharged from the hydrogen peroxide removal chamber 23 was determined, and the hydrogen peroxide removal rate in the hydrogen peroxide removal device was calculated. At the same time, the resistivity of the water being treated and the value of the DC voltage being applied at that time were calculated, and the power consumption per unit flow rate of the water being treated was calculated based on the applied voltage and current value. The results are shown in Table 1. After these measurements were completed, the Pd-loaded anion exchange resin (Pd AER) was removed from the hydrogen peroxide removal chamber 23 and its volume in the free state was calculated, which was 95-100% of the volume of the hydrogen peroxide removal chamber 23.

[Example 2]
A hydrogen peroxide removal apparatus similar to that of Example 1 was assembled in which the hydrogen peroxide removal chamber 23 and the concentration chamber 24 located on the side of the cathode 12 are separated only by a cation exchange membrane 33. The hydrogen peroxide removal apparatus of Example 2 has the structure shown in Fig. 2. Fig. 33 shows the main parts of the hydrogen peroxide removal apparatus of Example 2. In the hydrogen peroxide removal apparatus of Example 2, only one frame used in Example 1 is used, so that the thickness of the hydrogen peroxide removal chamber 23 is 1 cm.

The same measurements as in Example 1 were performed using the same water as in Example 1, with the flow rate of the water to be treated into the hydrogen peroxide removal chamber 23 set to 56 L/h, and the current flowing between the anode 11 and the cathode 12 set to 0.66 A. The results are shown in Table 1. After the measurements were completed, the Pd-loaded anion exchange resin (Pd AER) was removed from the hydrogen peroxide removal chamber 23 and its volume in the free state was measured, which was 95 to 100% of the volume of the hydrogen peroxide removal chamber 23. In the hydrogen peroxide removal device of Example 2, a water dissociation reaction proceeds at the interface between the Pd-loaded anion exchange resin (Pd AER) and the cation exchange membrane 33, and the hydrogen ions generated at this time are released into the concentration chamber 24 adjacent to the hydrogen peroxide removal chamber 23 and react with the carbonic acid component contained in the water in the concentration chamber 24 to produce free carbonic acid. Since free carbon dioxide does not have a charge, it is not affected by the charge repulsion of the cation exchange membrane 33 and diffuses from the concentration chamber 24 into the hydrogen peroxide removal chamber 23 through the cation exchange membrane 33. Since this free carbon dioxide is not in an ionic form, it is difficult to be adsorbed by the Pd-loaded anion exchange resin (Pd AER) in the hydrogen peroxide removal chamber 23, and leaks into the treated water, causing a deterioration in water quality. In order for the carbonic acid component to be adsorbed by the Pd-loaded anion exchange resin (Pd AER), it must be converted into carbonate ions or bicarbonate ions. In contrast, in the hydrogen peroxide removal device of Example 1, the anion exchange membrane 81 is superimposed on the cation exchange membrane 33 through which the free carbon dioxide diffuses, so that the free carbon dioxide is reliably converted into carbonate ions or bicarbonate ions when passing through the anion exchange membrane 81 before being released into the hydrogen peroxide removal chamber 23, and therefore the water quality of the treated water is less likely to deteriorate.

[Example 3]
A hydrogen peroxide removal apparatus similar to that of Example 1 was assembled in which the hydrogen peroxide removal chamber 23 and the concentration chamber 24 located on the side of the cathode 12 are separated only by a cation exchange membrane 33. Figure 34 shows the main parts of the hydrogen peroxide removal apparatus of Example 3. In the hydrogen peroxide removal apparatus of Example 3, the thickness of the hydrogen peroxide removal chamber 23 is 2 cm, the same as in Example 1. The hydrogen peroxide removal apparatus of Example 3 also has the structure shown in Figure 2, and only the thickness of the hydrogen peroxide removal chamber 23 differs between Examples 2 and 3.

The same measurements as in Example 1 were performed using the same water as in Example 1, with the flow rate of the water to be treated into the hydrogen peroxide removal chamber 23 set to 88 L/h, and the current flowing between the anode 11 and the cathode 12 set to 1.04 A. The results are shown in Table 1. After the measurements were completed, the Pd-loaded anion exchange resin (Pd AER) was removed from the hydrogen peroxide removal chamber 23 and its volume in the free state was measured; it was 95-100% of the volume of the hydrogen peroxide removal chamber 23. In the hydrogen peroxide removal device of Example 3, the water dissociation reaction also proceeds at the interface between the Pd-loaded anion exchange resin (Pd AER) and the cation exchange membrane 33, and the hydrogen ions generated at this time diffuse into the concentration chamber 24 through the cation exchange membrane 33, producing free carbon dioxide.

Comparing Examples 1 to 3, the hydrogen peroxide removal rate was almost the same, and Example 1 had the highest resistivity of the treated water. In all of Examples 1 to 3, the DC voltage applied between the anode 11 and the cathode 12 was within a practical range. However, in Example 1, the applied voltage was 10.0 V, while in Example 2, the applied voltage was 14.6 V, which was about 1.5 times that of Example 1, despite the current value being smaller than that of Example 1. In Example 3, which had the same current value as Example 1, the applied voltage was 29.2 V, which was about three times that of Example 1. As the applied voltage increased, the power consumption per unit flow rate of the treated water was 0.11 W·h/L in Example 1, while it was 0.17 W·h/L in Example 2, which was about 1.5 times that of Example 1, and 0.33 W·h/L in Example 3, which was about three times that of Example 1. Thus, in Example 1, the applied voltage can be lowered and the power consumption per amount of treated water can be reduced because, in Example 1, the water dissociation reaction occurs over the entire surface of the interface between the anion exchange membrane 81 and the cation exchange membrane 33, so that a large amount of hydroxide ions used for electrical regeneration of the ion exchanger are supplied to the hydrogen peroxide removal chamber 23. In contrast, in Examples 2 and 3, the water dissociation reaction proceeds only in a relatively narrow area, that is, the point where the Pd-loaded anion exchange resin (Pd AER) and the cation exchange membrane 33 contact, so that the amount of hydroxide ions produced is small, resulting in an increase in the applied voltage. In addition, the resistivity of the treated water is high in Example 1 because the free carbonic acid diffusing from the concentration chamber 24 to the hydrogen peroxide removal chamber 23 is converted to carbonate ions or bicarbonate ions when diffusing through the anion exchange membrane 81, and then captured by the Pd-loaded anion exchange resin (Pd AER).

[Example 4]
The filling rate of the ion exchanger in the hydrogen peroxide removal chamber was examined. Here, the filling rate of the ion exchanger refers to the value obtained by dividing the volume of the ion exchanger in a free state that is removed from the hydrogen peroxide removal chamber after the water to be treated is passed through the hydrogen peroxide removal chamber by the volume of the hydrogen peroxide removal chamber, as described above. A hydrogen peroxide removal device having the same configuration as in Example 1 was used, and the hydrogen peroxide removal chamber 23 was filled with a salt-type Pd-supported anion exchange resin (Pd AER). The hydrogen peroxide removal devices of Example 4-1 and Example 4-2 were constructed by changing the filling amount at this time. Water having a conductivity of 1.3 μS/cm, a hydrogen peroxide concentration of 97.5 μg/L, and a total carbonate concentration of 0.103 mg/L (as CO ₂ ) was supplied to the electrode chambers, concentration chambers 22, 24, and hydrogen peroxide removal chamber 23, and a voltage was applied between anode 11 and cathode 12 so as to give a current of 1.04 A. The flow rate of water to be treated into hydrogen peroxide removal chamber 23 was set to 88 L/h.

For each of the hydrogen peroxide removal devices of Examples 4-1 and 4-2, the concentration of hydrogen peroxide contained in the treated water discharged from the hydrogen peroxide removal chamber 23 was determined when the system stabilized approximately 500 hours after water flow through the hydrogen peroxide removal device and application of DC voltage was started, and the hydrogen peroxide removal rate of this hydrogen peroxide removal device was determined. At the same time, the resistivity of the water to be treated and the value of the DC voltage applied at that time were determined. The results are shown in Table 2. After these measurements were completed, the Pd-supported anion exchange resin (Pd AER) was removed from the hydrogen peroxide removal chamber 23 and its volume in the free state was determined to determine the filling rate, which was 110-115% in Example 4-1 and 95-100% in Example 4-2.

Comparing Example 4-1 and Example 4-2, the hydrogen peroxide removal rate is almost the same, but there is a slight difference in the resistivity of the treated water. However, in Example 4-1, which has a high filling rate, the applied voltage is 6.5 V, while in Example 4-2, which has a low filling rate, the applied voltage is 29.2 V, which is about 4.5 times that of Example 4-1. Even compared to Example 1, the applied voltage could be lowered in Example 4-1, which has a higher filling rate. It was found that the applied voltage can be lowered by increasing the filling rate within a range that does not impede the flow of the water to be treated. In addition, it is believed that the resistivity of the treated water in Example 4-1 was slightly higher and more favorable because the voltage was lower and current flowed more easily.

[Example 5]
The relationship between the packing rate of the ion exchanger carrying a platinum group metal catalyst and the electrical resistance of the hydrogen peroxide removal chamber was investigated. In this case, a space of 53.1 ^cm3 with platinum plate electrodes on both sides was prepared to simulate the hydrogen peroxide removal chamber, and the space was filled with salt-form Pd-carrying anion exchange resin to correspond to the packing rate, and ultrapure water at a temperature of 25°C was passed through it. Then, an LCR meter was used to apply an AC voltage of 1 kHz and 1000 mV between the plate electrodes to measure the impedance between the plate electrodes, and this was evaluated as the electrical resistance when a DC voltage was applied when operating as a hydrogen peroxide removal device. The results are shown in Figure 35. As shown in Figure 35, when the packing rate was less than 0.95 (i.e., 95%), the electrical resistance became significantly large, and a lot of energy was required for the electrical regeneration of the ion exchanger in the hydrogen peroxide removal chamber 23. It has been found that the filling rate is preferably 0.95 to 1.25 (i.e., 95% to 125%), and more preferably 1.02 to 1.25 (i.e., 102% to 125%).

[Example 6]
As in Example 4, the filling rate of the ion exchanger in the hydrogen peroxide removal chamber was examined. A hydrogen peroxide removal device having the same configuration as in Example 3 shown in FIG. 34 was used, and the hydrogen peroxide removal chamber 23 was filled with a salt-type Pd-supported anion exchange resin (Pd AER). The hydrogen peroxide removal devices of Examples 6-1 and 6-2 were constructed by changing the filling amount. In Example 6-1, water with a conductivity of 1.2 μS/cm, a hydrogen peroxide concentration of 102 μg/L, and a total carbonate concentration of 0.104 mg/L (as CO ₂ ) was supplied to the electrode chamber, the concentration chambers 22 and 24, and the hydrogen peroxide removal chamber 23, and in Example 6-2, water with a conductivity of 1.3 μS/cm, a hydrogen peroxide concentration of 96.3 μg/L, and a total carbonate concentration of 0.103 mg/L (as CO ₂ ) was supplied to the electrode chamber, the concentration chambers 22 and 24, and the hydrogen peroxide removal chamber 23. In both Example 6-1 and Example 6-2, the flow rate of the water to be treated into the hydrogen peroxide removal chamber 23 was set to 88 L/h, and a voltage was applied between the anode 11 and the cathode 12 so that the current was 1.04 A.

For each of the hydrogen peroxide removal devices of Examples 6-1 and 6-2, the concentration of hydrogen peroxide contained in the treated water discharged from the hydrogen peroxide removal chamber 23 was determined when the system stabilized approximately 300 hours after the start of water flow and application of DC voltage to the hydrogen peroxide removal device, and the hydrogen peroxide removal rate of this hydrogen peroxide removal device was calculated. At the same time, the resistivity of the treated water, the value of the DC voltage applied at that time, and the power consumption per amount of treated water were determined. The results are shown in Table 3. After these measurements were completed, the Pd-supported anion exchange resin (Pd AER) was removed from the hydrogen peroxide removal chamber 23 and its volume in the free state was determined to determine the filling rate, which was 110-115% in Example 6-1 and 95-100% in Example 6-2.

Comparing Example 6-1 and Example 6-2, the hydrogen peroxide removal rate is almost the same, but there is a difference in the resistivity of the treated water. With regard to the applied voltage, Example 6-1, which has a high filling rate, had less than half the voltage of Example 6-2, which has a low filling rate, and as a result, the power consumption was lower. It is believed that the lower voltage, which made it easier for current to flow, resulted in the resistivity of the treated water in Example 6-1 being higher than in Example 6-2, resulting in a better value.

11 Anode 12 Cathode 21, 26 Anode chamber 22, 24 Concentration chamber 23, 29 Hydrogen peroxide removal chamber 25, 27 Cathode chamber 28 Deionization chamber 31, 33, 35, 83 Cation exchange membrane (CEM)
32, 34, 37, 38, 81, 82 Anion exchange membrane (AEM)
36 Intermediate ion exchange membrane 51, 52 Reverse osmosis membrane device 54 Electrodeionization device (EDI)
55, 61 Ultraviolet oxidation device (UV)
56, 63 Non-regenerative ion exchange resin (CP)
57 Boron-selective ion exchange resin (B IER)
58, 65 Degassing membrane (MD)
67 Ultrafiltration membrane (UF)
100 Hydrogen peroxide removal device 300 Pure water production device 400 Ultrapure water production device

Claims (11)

A method for removing hydrogen peroxide contained in water to be treated, comprising the steps of:
The method includes a step of passing the water to be treated through a hydrogen peroxide removal chamber filled with an ion exchanger and disposed between an anode and a cathode while applying a DC voltage between the anode and the cathode,
At least a portion of the ion exchanger packed in the hydrogen peroxide removal chamber is an ion exchanger carrying a metal catalyst having hydrogen peroxide decomposition ability,
a filling factor, which is the value obtained by dividing the bulk volume , including voids between particles, of the ion exchanger in a free state when removed from the hydrogen peroxide removal chamber after the water passing step by the volume of the hydrogen peroxide removal chamber, is 95% or more and 125% or less. The method of claim 1, wherein the filling rate is 102% or more and 125% or less. The method according to claim 1 or 2, wherein the metal catalyst is a platinum group metal catalyst, and the ion exchanger on which the metal catalyst is supported is an anion exchanger. The method according to any one of claims 1 to 3, wherein the hydrogen peroxide removal chamber is partitioned by an anion exchange membrane on the anode side and by an ion exchange membrane on the cathode side. A hydrogen peroxide removal device for removing hydrogen peroxide contained in water to be treated,
an anode and a cathode;
a hydrogen peroxide removal chamber provided between the anode and the cathode and filled with an ion exchanger;
having
At least a portion of the ion exchanger packed in the hydrogen peroxide removal chamber is an ion exchanger carrying a metal catalyst having hydrogen peroxide decomposition ability,
A DC voltage is applied between the anode and the cathode,
a filling rate, which is a value obtained by dividing the bulk volume, including voids between particles of the ion exchanger , in a free state when the ion exchanger is removed from the hydrogen peroxide removal chamber after a DC voltage is applied between the anode and the cathode to pass the water to be treated through the hydrogen peroxide removal chamber, by the volume of the hydrogen peroxide removal chamber, of 95% or more and 125% or less. The hydrogen peroxide removal device according to claim 5, wherein the filling rate is 102% or more and 125% or less. The hydrogen peroxide removal device according to claim 5 or 6, wherein the metal catalyst is a platinum group metal catalyst, and the ion exchanger on which the metal catalyst is supported is an anion exchanger. The hydrogen peroxide removal device according to any one of claims 5 to 7, wherein the hydrogen peroxide removal chamber is partitioned by an anion exchange membrane on the anode side and by an ion exchange membrane on the cathode side. A deionization chamber filled with an ion exchanger is provided on the cathode side or the anode side of the ion exchange membrane,
9. The hydrogen peroxide removal apparatus according to claim 8, wherein water treated in the hydrogen peroxide removal chamber is passed through the deionization chamber. The hydrogen peroxide removal device according to any one of claims 5 to 9, wherein the ion exchanger carrying the metal catalyst is disposed in contact with the inlet of the water to be treated in the hydrogen peroxide removal chamber. The hydrogen peroxide removal device according to any one of claims 5 to 10,
an ultraviolet oxidation device provided upstream of the hydrogen peroxide removal device;
A pure water production apparatus having the above structure.

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