Electrodialysis system, electrodialysis method, waste liquid treatment system, and waste liquid treatment method

Abstract

Provided is an electrodialysis system that can prevent the generation of scale derived from hardness components and silica and can efficiently perform deionization treatment in the treatment of a liquid to be treated having a pH of 3 or less or 12 or more. The electrodialysis system includes at least an anode, a cathode, a first bipolar membrane, an ion exchange membrane, and a second bipolar membrane, and an electrodialysis device in which the first bipolar membrane, the ion exchange membrane, and the second bipolar membrane are arranged in this order from the anode side between the anode and the cathode, and pH measurement means for measuring the pH of the treated liquid obtained after the liquid to be treated passes through the electrodialysis device. When the pH value of the treated liquid measured by the pH measurement means reaches a predetermined value, the electrodialysis treatment by the electrodialysis device is terminated.

Description

Technical Field

[0001] The present invention relates to an electrodialysis system, an electrodialysis method, a waste liquid treatment system, and a waste liquid treatment method.

Background Art

[0002] Ion exchangers are used in various applications, and as an example, they are used as ion removal materials in pure water production devices. Cation exchangers adsorb cation components, and when the adsorption capacity decreases, the adsorption capacity is restored by regenerating the cation exchanger with an acid. During regeneration, usually more acid than the exchange capacity of the cation exchanger is used, so excess acid is present in the regeneration waste liquid. Also, anion exchangers adsorb anion components, and when the adsorption performance decreases, the adsorption capacity is restored by regenerating the anion exchanger with an alkali. During the regeneration of the anion exchanger, more alkali than the exchange capacity of the anion exchanger is used for regeneration, so excess alkali is present in the regeneration waste liquid.

[0003] These regeneration waste liquids are usually mixed and then neutralized and treated. However, since excess acid or alkali is added, more acid or alkali is required for neutralization, resulting in an increase in the amount of chemicals used and an increase in the salt concentration in the waste liquid.

[0004] Therefore, a method has been proposed in which these regeneration waste liquids are electrolyzed by electrodialysis to recover acid and alkali.

[0005] For example, Patent Document 1 proposes a method in which after mixing the regeneration waste liquids of a cation exchange tower and an anion exchange tower, acid and alkali are recovered by an electrodialysis device equipped with bipolar membranes, and the recovered acid and alkali are reused for the regeneration of resin towers.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] In the method described in Patent Document 1, Na in the regeneration waste liquid + and Cl - are separated using an ion exchange membrane, and H obtained by decomposing water with a bipolar membrane is supplied to each of them + and OH - to produce an acid or an alkali as NaOH and HCl. At this time, if the separation of Na + and Cl - is continued, the ion concentration in the supply liquid decreases, making it difficult for an electric current to flow, and there is a problem that it takes a long time for separation.

[0008] Also, in this method, Ca in the acidic regeneration waste liquid 2+ and Mg 2+ permeate through the cation exchange membrane, and when OH - is supplied thereto, it becomes alkaline and scale is generated, or when H + is supplied to the alkaline regeneration waste liquid and the pH decreases, silica scale is generated.

[0009] Furthermore, when only one of the waste acid or the waste alkali can be reused, that is, when there is only one use for the waste acid or the waste alkali, if both Na + and Cl - in the waste liquid are electrolyzed to produce both NaOH and HCl, one of them will be discarded, resulting in an increase in the cost of disposal.

[0010] An object of the present invention is to provide an electrodialysis system, an electrodialysis method, a waste liquid treatment system, and a waste liquid treatment method that can prevent the generation of scale derived from hardness components and silica and can efficiently perform deionization treatment.

Means for Solving the Problems

[0011] As a result of intensive studies on the above problems, the inventors of the present invention have found that the above problems can be solved by terminating the electrodialysis when the pH of the treatment liquid reaches a predetermined value in the electrodialysis, and have completed the present invention.

[0012] The present invention includes the following aspects. [1] An electrodialysis system used for treating a liquid to be treated having a pH of 3 or less or a pH of 12 or more, having at least an anode, a cathode, a first bipolar membrane, an ion exchange membrane, and a second bipolar membrane, and an electrodialysis device in which the first bipolar membrane, the ion exchange membrane, and the second bipolar membrane are arranged in this order from the anode side between the anode and the cathode, pH measuring means for measuring the pH of the treatment liquid obtained after the liquid to be treated passes through the electrodialysis device, An electrodialysis system that terminates the electrodialysis treatment by the electrodialysis device when the value of the pH of the treatment liquid measured by the pH measuring means reaches a predetermined value. [2] The electrodialysis system according to [1], wherein the liquid to be treated is a liquid having a pH of 3 or less, and the ion exchange membrane of the electrodialysis device is an anion exchange membrane. [3] The electrodialysis system according to [1], wherein the liquid to be treated is a liquid having a pH of 12 or more, and the ion exchange membrane of the electrodialysis device is a cation exchange membrane. [4] The electrodialysis system according to [1], wherein the ion exchange membrane of the electrodialysis device is an anion exchange membrane, and a cation exchange membrane is provided between the anion exchange membrane and the second bipolar membrane. [5] In the electrodialysis device, an anode chamber defined by the anode and the first bipolar membrane, a cathode chamber defined by the cathode and the second bipolar membrane are arranged, an acid recovery chamber defined by the first bipolar membrane and the anion exchange membrane between the anode chamber and the cathode chamber, to which water is supplied to generate a recovered acid solution by electrodialysis treatment, An anion exchange membrane and the second bipolar membrane define a deionized water generation chamber where an acid supply solution is supplied as the liquid to be treated and deionized water is generated by electrodialysis treatment. The cell set composed of the acid recovery chamber and the deionized water generation chamber is arranged singly or repeatedly arranged two or more times. The electrodialysis system according to [2]. [6] In the electrodialysis device, An anode chamber defined by the anode and the first bipolar membrane, A cathode chamber defined by the cathode and the second bipolar membrane is arranged. Between the anode chamber and the cathode chamber, a deionized water generation chamber defined by the first bipolar membrane and the cation exchange membrane, where an alkali supply solution is supplied as the liquid to be treated and deionized water is generated by electrodialysis treatment. An alkali recovery chamber defined by the cation exchange membrane and the second bipolar membrane, where water is supplied and a recovered alkali solution is generated by electrodialysis treatment. The cell set composed of the deionized water generation chamber and the alkali recovery chamber is arranged singly or repeatedly arranged two or more times. The electrodialysis system according to [3]. [7] In the electrodialysis device, An anode chamber defined by the anode and the first bipolar membrane, A cathode chamber defined by the cathode and the second bipolar membrane is arranged. Between the anode chamber and the cathode chamber, an alkali recovery chamber defined by the cation exchange membrane and the second bipolar membrane, where water is supplied and a recovered alkali solution is generated by electrodialysis treatment. An acid recovery chamber defined by the anion exchange membrane and the first bipolar membrane, where water is supplied and a recovered acid solution is generated by electrodialysis treatment. A deionized water generation chamber defined by the cation exchange membrane and the anion exchange membrane, where the liquid to be treated is supplied and deionized water is generated by electrodialysis treatment. The cell set composed of the acid recovery chamber, the deionized water generation chamber, and the alkali recovery chamber is arranged singly or repeatedly arranged two or more times. The electrodialysis system according to [4]. [8] The pH of the liquid to be treated is less than 1, when the pH of the treatment liquid reaches the range of 1 or more and 3 or less, the electrodialysis treatment by the electrodialysis device is terminated, The electrodialysis system according to [2] or [4]. [9] The pH of the liquid to be treated is 12 or more, before the pH of the treatment liquid reaches the range of less than 9, the electrodialysis treatment by the electrodialysis device is terminated, The electrodialysis system according to [3] or [4].

[10] The liquid to be treated is the regeneration waste liquid of the ion exchange device, The electrodialysis system according to any one of [1] to [7].

[11] The recovered acid liquid or the recovered alkaline liquid is used in a water treatment system different from the water treatment system that discharges the liquid to be treated, The electrodialysis system according to any one of [5] to [7].

[12] An ion exchange device filled with an ion exchanger, A regeneration liquid supply device that supplies a regeneration liquid of the ion exchanger to the ion exchange device, An electrodialysis system that treats the regeneration waste liquid discharged from the ion exchange device, having, the regeneration waste liquid has a pH of 3 or less or a pH of 12 or more, the electrodialysis system is, at least having an anode, a cathode, a first bipolar membrane, an ion exchange membrane, and a second bipolar membrane, and the first bipolar membrane, the ion exchange membrane, and the second bipolar membrane are arranged in this order from the anode side between the anode and the cathode An electrodialysis device, pH measurement means for measuring the pH of the treatment liquid obtained after the regeneration waste liquid passes through the electrodialysis device, having, When the pH value of the treatment liquid measured by the pH measurement means reaches a predetermined value, the electrodialysis treatment by the electrodialysis device is terminated, A waste liquid treatment system.

[13] An electrodialysis method used for treating a liquid to be treated having a pH of 3 or less or a pH of 12 or more, An electrodialysis treatment is performed using an electrodialysis apparatus having at least an anode, a cathode, a first bipolar membrane, an ion exchange membrane, and a second bipolar membrane, wherein the first bipolar membrane, the ion exchange membrane, and the second bipolar membrane are arranged in this order from the anode side between the anode and the cathode. The pH of the treated liquid obtained after the liquid to be treated passes through the electrodialysis apparatus is measured. An electrodialysis method in which the electrodialysis treatment by the electrodialysis apparatus is terminated when the measured pH value of the treated liquid reaches a predetermined value.

[14] A regeneration liquid supply step of supplying a regeneration liquid of the ion exchanger to an ion exchange apparatus filled with an ion exchanger; An electrodialysis step of treating the regeneration waste liquid discharged from the ion exchange apparatus, and the regeneration waste liquid has a pH of 3 or less or 12 or more, The electrodialysis step is An electrodialysis treatment step of passing the regeneration waste liquid through an electrodialysis apparatus having at least an anode, a cathode, a first bipolar membrane, an ion exchange membrane, and a second bipolar membrane, wherein the first bipolar membrane, the ion exchange membrane, and the second bipolar membrane are arranged in this order from the anode side between the anode and the cathode; A step of measuring the pH of the treated liquid obtained after the regeneration waste liquid passes through the electrodialysis apparatus, and A waste liquid treatment method in which the electrodialysis treatment by the electrodialysis apparatus is terminated when the pH value of the treated liquid measured in the step of measuring the pH reaches a predetermined value.

Advantages of the Invention

[0013] According to the present invention, it is possible to provide an electrodialysis system, an electrodialysis method, a waste liquid treatment system, and a waste liquid treatment method that can prevent the generation of scale derived from hardness components and silica and can efficiently perform deionization treatment.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Mode for Carrying Out the Invention

[0015] According to an embodiment of the present invention, in the electrodialysis of a liquid to be treated having a pH of 3 or less or a pH of 12 or more, a specific electrodialysis apparatus is used, and by terminating the electrodialysis when the pH of the liquid to be treated reaches a predetermined value, it is possible to prevent scale formation and achieve efficient deionization. In this electrodialysis, an electrodialysis apparatus is used that has at least an anode, a cathode, a first bipolar membrane, an ion exchange membrane, and a second bipolar membrane, with the first bipolar membrane, the ion exchange membrane, and the second bipolar membrane being arranged between the anode and the cathode in this order from the anode side. When the liquid to be treated is, for example, a caustic soda regeneration waste liquid, the OH present in the liquid to be treated is - and the equivalent amount of Na + When the liquid to be treated is, for example, an acidic wastewater of hydrochloric acid, the H + and an equivalent amount of Cl - can be separated and recovered as HCl. Also, SO4 2- Other anions and equivalent amounts of Na + Ya, Ca 2+ and Mg 2+ Other cations and equivalent amounts of Cl - By minimizing separation of components that exist as neutral salts when considered as compounds, such as the above, it is possible to prevent the generation of scale derived from hardness components and silica.

[0016] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to these embodiments and the configurations shown in the drawings. (Electrodialysis system and electrodialysis method) As shown in FIG. 1, the electrodialysis device 100 used in the electrodialysis system / method according to the embodiment of the present invention includes an anode 1, a cathode 11, a bipolar membrane 3 (hereinafter, the "bipolar membrane" is also referred to as "BPM") (BPM3), an ion exchange membrane 5, and a bipolar membrane 9 (BPM9). Between the anode 1 and the cathode 11, the BPM3, the ion exchange membrane 5, and the BPM9 are arranged in this order from the anode 1 side. This electrodialysis device 100 has an anode chamber 20 defined by the anode 1 and the BPM3, an acid recovery chamber 22 defined by the BPM3 and the ion exchange membrane 5, a deionized chamber 24 defined by the ion exchange membrane 5 and the BPM9, and a cathode chamber 34 defined by the bipolar membrane 9 and the cathode 11.

[0017] Here, the bipolar membranes 3 and 9 are membranes in which a cation exchange membrane and an anion exchange membrane are integrated, and usually have a structure in which a cation exchange membrane and an anion exchange membrane are stacked. Further, the bipolar membrane has a structure in which the interface where the cation exchange membrane and the anion exchange membrane are stacked is optimized for the dissociation reaction of water, and is configured such that the dissociation reaction of water easily proceeds. For this purpose, generally, a substance having a catalytic action for water dissociation (for example, heavy metal ions, tertiary amines, etc.) is introduced into the interface where separate ion exchange membranes are stacked. Also, the bipolar membrane is arranged with the anion exchange membrane side on the anode side and the cation exchange membrane side on the cathode side.

[0018] Also, the bipolar membranes 3 and 9 only need to be membranes effective for water dissociation, and it is sufficient that they have a structure in which a cation exchange membrane and an anion exchange membrane are stacked, not limited to those sold as products.

[0019] The material of the ion exchange membrane 5 used in the electrodialysis device 100 of the electrodialysis system according to the embodiment of the present invention is not particularly limited, and known ones can be appropriately used, and a membrane effective for separating target ions may be selected. For example, a homogeneous membrane obtained by coating a paste containing styrene and divinylbenzene with polyvinyl chloride and then heating it, and then introducing an exchange group, or a heterogeneous membrane formed by molding powder of an ion exchange resin using a binder having appropriate film-forming properties such as polyethylene, polystyrene, phenol resin, synthetic rubber, etc. can be mentioned.

[0020] For the anode 1 and the cathode 11, electrodes used in the electrochemical industry such as water electrolysis can be used, and such electrodes can be used without any restrictions. Examples of the electrodes that can be used for the anode 1 and the cathode 11 include a nickel electrode, a titanium-platinum plated electrode, and a stainless steel electrode. The anode chamber 20 and the cathode chamber 34 are each filled with an electrode solution. Examples of the electrode solution include a sodium hydroxide solution, a sodium sulfate solution, and pure water.

[0021] Here, the anode chamber 20 houses the anode 1, and an acid recovery chamber 22 adjacent to the anode chamber 20 is provided via the BPM 3. Further, the cathode chamber 34 houses the cathode 11, and a deionization chamber 24 adjacent to the cathode chamber 34 is provided via the BPM 9.

[0022] In the above configuration, the anode chamber 20 and the acid recovery chamber 22 are partitioned by the BPM 3, and the acid recovery chamber 22 and the deionization chamber 24 are partitioned by the ion exchange membrane 5. Further, the deionization chamber 24 and the cathode chamber 34 are partitioned by the BPM 9. That is, the electrodialysis apparatus 100 shown in FIG. 1 is a two-chamber type electrodialysis apparatus mainly composed of two chambers, the acid recovery chamber 22 and the deionization chamber 24, in which the BPM 3, the ion exchange membrane 5, and the BPM 9 are arranged in order from the anode 1 side.

[0023] Note that an anion exchange membrane (hereinafter sometimes referred to as "AEM") is used as the ion exchange membrane 5. The following describes the case where an anion exchange membrane is used as the ion exchange membrane 5.

[0024] Here, when each chamber constituting the electrodialysis apparatus 100 is represented in order from the anode 1 side, it is anode - anode chamber - (acid recovery chamber - deionization chamber)n - cathode chamber - cathode. Here, the smallest repeating unit composed of the "acid recovery chamber - deionization chamber" in the parentheses is defined as the basic configuration (that is, the cell set), and n (n is an integer of 1 or more) is the number of repeated laminations of the cell sets. Note that FIG. 1 shows a configuration where n = 1. The number of repeated laminations of the cell set can usually be set in the range of n = 1 to 500, preferably in the range of 1 to 200.

[0025] When representing each membrane constituting the electrodialysis device 100 in order from the anode side, it becomes anode-(BPM - AEM)n - BPM - cathode. Here, n (n is an integer of 1 or more) is the number of repeated laminations of the cell set. Note that FIG. 1 shows a configuration with n = 1.

[0026] In the electrodialysis device 100 used in the embodiment of the present invention shown in FIG. 1, water (for example, pure water) is supplied to the acid recovery chamber 22, and the water to be treated (acid supply liquid) is supplied to the deionization chamber 24, and electrodialysis treatment is performed. The water supplied to the acid recovery chamber 22 passes through the acid recovery chamber 22 and is discharged as recovered acid liquid. The water to be treated supplied to the deionization chamber 24 passes through the deionization chamber 24 and is discharged as deionized water.

[0027] As shown in FIG. 2, the electrodialysis device 200 used in the electrodialysis system / method according to the embodiment of the present invention includes at least an anode 1, a cathode 11, a BPM 3, an ion exchange membrane 5, and a BPM 9, and the BPM 3, the ion exchange membrane 5, and the BPM 9 are arranged in order from the anode 1 side between the anode 1 and the cathode 11. This electrodialysis device 200 has an anode chamber 20 defined by the anode 1 and the BPM 3, a deionization chamber 30 defined by the BPM 3 and the ion exchange membrane 5, an alkali recovery chamber 32 defined by the ion exchange membrane 5 and the BPM 9, and a cathode chamber 34 defined by the BPM 9 and the cathode 11.

[0028] Here, the anode chamber 20 houses the anode 1, and a deionization chamber 30 adjacent to the anode chamber 20 is provided via the BPM 3. Also, the cathode chamber 34 houses the cathode 11, and an alkali recovery chamber 32 adjacent to the cathode chamber 34 is provided via the BPM 9.

[0029] In the above configuration, the anode chamber 20 and the deionization chamber 30 are separated by BPM3, and the deionization chamber 30 and the alkali recovery chamber 32 are separated by the ion exchange membrane 5. Also, the alkali recovery chamber 32 and the cathode chamber 34 are separated by BPM9. That is, the electrodialysis apparatus 200 shown in Fig. 2 is a two-chamber type electrodialysis apparatus mainly composed of two chambers, the deionization chamber 30 and the alkali recovery chamber 32, in which BPM3, the ion exchange membrane 5, and BPM9 are arranged in order from the anode 1 side.

[0030] Note that as the ion exchange membrane 5, a cation exchange membrane (hereinafter also referred to as "CEM") is used. The following describes the case where a cation exchange membrane is used as the ion exchange membrane 5.

[0031] Here, when representing each chamber constituting the electrodialysis apparatus 200 in order from the anode side, it becomes anode - anode chamber - (deionization chamber - alkali recovery chamber)n - cathode chamber - cathode. Here, the smallest repeating unit composed of "deionization chamber - alkali recovery chamber" within the parentheses is defined as the basic configuration (i.e., cell set), and n (n is an integer of 1 or more) is the number of repeated laminations of the cell set. Note that Fig. 2 shows a configuration where n = 1.

[0032] When representing each membrane constituting the electrodialysis apparatus 200 in order from the anode side, it becomes anode - BPM - (CEM - BPM)n - cathode. Here too, n (n is an integer of 1 or more) is the number of repeated laminations of the cell set. Note that Fig. 2 shows a configuration where n = 1. Also in the configuration shown in Fig. 2, the number of repeated laminations of the cell set can usually be set in the range of n = 1 to 500, preferably in the range of 1 to 200.

[0033] In the electrodialysis apparatus 200 used in the embodiment of the present invention shown in Fig. 2, the water to be treated (alkali supply liquid) is supplied to the deionization chamber 30, water (for example, pure water) is supplied to the alkali recovery chamber 32, and electrodialysis treatment is performed. The alkali supply liquid supplied to the deionization chamber 30 passes through the deionization chamber 30 and is discharged as deionized water. The water supplied to the alkali recovery chamber 32 passes through the alkali recovery chamber 32 and is discharged as a recovered alkali liquid.

[0034] As shown in FIG. 3, the electrodialysis apparatus 300 used in the electrodialysis system / method according to an embodiment of the present invention has at least an anode 1, a cathode 11, a BPM 3, an AEM 5, a CEM 7, and a BPM 9, and the BPM 3, AEM 5, CEM 7, and BPM 9 are arranged in this order from the anode 1 side between the anode 1 and the cathode 11.

[0035] This electrodialysis apparatus 300 has an anode chamber 20 defined by the anode 1 and the BPM 3, an acid recovery chamber 22 defined by the BPM 3 and the AEM 5, a deionized chamber 24 defined by the AEM 5 and the CEM 7, an alkali recovery chamber 32 defined by the CEM 7 and the BPM 9, and a cathode chamber 34 defined by the BPM 9 and the cathode 11.

[0036] Here, the anode chamber 20 houses the anode 1, and the acid recovery chamber 22 adjacent to the anode chamber 20 is provided via the BPM 3. Further, the cathode chamber 34 houses the cathode 11, and the alkali recovery chamber 32 adjacent to the cathode chamber 34 is provided via the BPM 9.

[0037] In the above configuration, the anode chamber 20 and the acid recovery chamber 22 are partitioned by the BPM 3, the acid recovery chamber 22 and the deionized chamber 24 are partitioned by the AEM 5, the deionized chamber 24 and the alkali recovery chamber 32 are partitioned by the CEM 7. Also, the alkali recovery chamber 32 and the cathode chamber 34 are partitioned by the BPM 9. That is, the electrodialysis apparatus shown in FIG. 3 is a three-chamber type electrodialysis apparatus mainly composed of three chambers, namely, the acid recovery chamber 22, the deionized chamber 24, and the alkali recovery chamber 32, in which the BPM 3, AEM 5, CEM 7, and BPM 9 are arranged in this order from the anode 1 side.

[0038] Here, when each chamber constituting the electrodialysis apparatus 300 is represented in order from the anode side, it is anode - anode chamber - (acid recovery chamber - deionized chamber - alkali recovery chamber)n - cathode chamber - cathode. Here, the minimum repeating unit composed of "acid recovery chamber - deionized chamber - alkali recovery chamber" within the parentheses is defined as the basic configuration (i.e., cell set), and n (n is an integer of 1 or more) is the number of repeated laminations of the cell set. Note that FIG. 3 shows a configuration where n = 1. Even in the configuration shown in FIG. 3, the number of repeated laminations of the cell sets can usually be set in the range of n = 1 to 500, preferably in the range of 1 to 200.

[0039] When representing each membrane constituting the electrodialysis apparatus 300 in order from the anode side, it becomes anode - BPM - (AEM - CEM - BPM)n - cathode. Here, n (n is an integer of 1 or more) is the number of repeated laminations of the cell sets. Note that FIG. 3 shows a configuration where n = 1.

[0040] In the electrodialysis apparatus 300 used in the embodiment of the present invention shown in FIG. 3, raw water (acid supply liquid) is supplied to the deionization chamber 24, water (for example, pure water) is supplied to the acid recovery chamber 22 and the alkali recovery chamber 32, and electrodialysis treatment is performed. The raw water supplied to the deionization chamber 24 passes through the deionization chamber 24 and is discharged as deionized water. The water supplied to the acid recovery chamber 22 passes through the acid recovery chamber 22 and is discharged as a recovered acid solution. The water supplied to the alkali recovery chamber 32 passes through the alkali recovery chamber 32 and is discharged as a recovered alkali solution.

[0041] As shown in FIG. 4, the electrodialysis apparatus 400 used in the electrodialysis system / method according to the embodiment of the present invention includes at least an anode 1, a cathode 11, a BPM 3, an AEM 5, a CEM 7, and a BPM 9, and the BPM 3, AEM 5, CEM 7, and BPM 9 are arranged in order from the side of the anode 1 between the anode 1 and the cathode 11.

[0042] This electrodialysis apparatus 400 has an anode chamber 20 defined by the anode 1 and the BPM 3, an acid recovery chamber 22 defined by the BPM 3 and the AEM 5, a deionization chamber 30 defined by the AEM 5 and the CEM 7, an alkali recovery chamber 32 defined by the CEM 7 and the BPM 9, and a cathode chamber 34 defined by the BPM 9 and the cathode 11.

[0043] Here, the anode chamber 20 houses the anode 1, and the acid recovery chamber 22 adjacent to the anode chamber 20 is provided via the BPM 3. Further, the cathode chamber 34 houses the cathode 11, and the alkali recovery chamber 32 adjacent to the cathode chamber 34 is provided via the BMP 9.

[0044] In the above configuration, the anode chamber 20 and the acid recovery chamber 22 are partitioned by BPM3, the acid recovery chamber 22 and the deionization chamber 30 are partitioned by AEM5, and the deionization chamber 30 and the alkali recovery chamber 32 are partitioned by CEM7. Also, the alkali recovery chamber 32 and the cathode chamber 34 are partitioned by BPM9. That is, the electrodialysis device shown in Fig. 4 is a three-chamber type electrodialysis device mainly composed of three chambers: the acid recovery chamber 22, the deionization chamber 30, and the alkali recovery chamber 32, in which BPM3, AEM5, CEM7, and BPM9 are arranged in order from the anode 1 side.

[0045] Here, when representing each chamber constituting the electrodialysis device 400 in order from the anode side, it becomes anode - anode chamber - (acid recovery chamber - deionization chamber - alkali recovery chamber)n - cathode chamber - cathode. Here, the smallest repeating unit composed of "acid recovery chamber - deionization chamber - alkali recovery chamber" within the parentheses is defined as the basic configuration (i.e., cell set), and n (n is an integer of 1 or more) is the number of repeated laminations of the cell set. Note that Fig. 4 shows a configuration with n = 1. Also in the configuration shown in Fig. 4, the number of repeated laminations of the cell set can usually be set in the range of n = 1 to 500, preferably in the range of 1 to 200.

[0046] When representing each membrane constituting the electrodialysis device 400 in order from the anode side, it becomes anode - BPM - (AEM - CEM - BPM)n - cathode. Here too, n (n is an integer of 1 or more) is the number of repeated laminations of the cell set. Note that Fig. 4 shows a configuration with n = 1.

[0047] In the electrodialysis device 400 used in the embodiment of the present invention shown in Fig. 4, the water to be treated (alkali supply liquid) is supplied to the deionization chamber 30, water (for example, pure water) is supplied to the acid recovery chamber 22 and the alkali recovery chamber 32, and electrodialysis treatment is performed. The water to be treated supplied to the deionization chamber 30 passes through the deionization chamber 30 and is discharged as deionized water. The water supplied to the acid recovery chamber 22 passes through the acid recovery chamber 22 and is discharged as recovered acid solution. The water supplied to the alkali recovery chamber 32 passes through the alkali recovery chamber 32 and is discharged as recovered alkali solution.

[0048] In the case of a three-chamber electrodialysis apparatus as shown in FIGS. 3 and 4, two types of ion exchange membranes, an anion exchange membrane and a cation exchange membrane, and bipolar membranes are alternately arranged. Further, in a two-chamber electrodialysis apparatus as shown in FIGS. 1 and 2, when recovering acidic water to be treated, for example, hydrochloric acid regeneration waste liquid of a cation exchange resin, anion exchange membranes and bipolar membranes are alternately arranged, and when recovering alkaline water to be treated, for example, caustic soda regeneration waste liquid of an anion exchange resin, cation exchange membranes and bipolar membranes are alternately arranged.

[0049] Here, there is no limit to the flow rate and volume of the supply water to the acid recovery chamber and the recovered alkali chamber, but the lower the flow rate and volume, the higher the concentration of the recovered alkali liquid can be. And by adjusting the liquid volume and volume, the concentration can be adjusted according to the reuse application of the recovered acid liquid or the recovered alkali liquid.

[0050] The three-chamber electrodialysis apparatus can recover both acid and alkali, but the apparatus becomes more complicated compared to the two-chamber electrodialysis apparatus. Therefore, when only one of acid and alkali needs to be recovered, it is preferable to adopt a two-chamber electrodialysis apparatus.

[0051] The regeneration waste liquid of the ion exchange resin can be stored in a supply liquid tank as a liquid to be treated, and can be supplied to the electrodialysis apparatus by means such as a pump. The supply liquid supplied to the electrodialysis apparatus as the liquid to be treated is usually circulated and treated during the electrodialysis treatment, and the treated liquid (deionized water) after the end of the electrodialysis treatment is drained to an arbitrary place. At the outlet of the deionization chamber of the electrodialysis apparatus to which the supply liquid is supplied, pH measuring means for measuring the pH of the treated liquid (deionized water) can be provided, and the end point of electrodialysis can be determined based on the pH value measured by this pH measuring means.

[0052] (Waste liquid treatment system and waste liquid treatment method) Next, a waste liquid treatment system and a waste liquid treatment method for treating the regeneration waste liquid of an ion exchanger according to an embodiment of the present invention will be described. FIG. 5 shows an example of a waste liquid treatment system for treating the regeneration waste liquid of a cation exchanger (cation exchange resin). The waste liquid treatment system 500 according to an embodiment of the present invention includes a cation exchange device 102 filled with a cation exchanger, a regeneration liquid storage tank 104 for storing a solution (regeneration liquid) for regenerating the cation exchanger, and a regeneration waste liquid storage tank 106 for storing the regeneration waste liquid of the cation exchanger. A regeneration liquid passage line L1 for passing the regeneration liquid to the cation exchange device 102 is provided in the regeneration liquid storage tank 104. And the waste liquid treatment system 500 includes a first water storage tank 108, a second water storage tank 110, an electrode liquid storage tank 112, and an electrodialysis device 300. The regeneration liquid can be supplied to the cation exchange device using means such as a pump. The waste liquid treatment system 500 performs ion exchange treatment on a liquid to be treated such as groundwater or industrial water with the cation exchange device 102 to produce cation-exchanged water. When a predetermined water flow rate is reached, the passage of the liquid to be treated to the cation exchange device 102 is stopped, and the regeneration liquid stored in the regeneration liquid storage tank 104 is passed through the line L1 to the cation exchange device 102. The regeneration liquid that has passed through the cation exchange device 102 is stored in the regeneration waste liquid storage tank 106 as regeneration waste liquid. The cation exchange device 102 after regeneration is passed through with the liquid to be treated again to perform ion exchange treatment to produce cation-exchanged water. A pretreatment device such as a membrane treatment device, an activated carbon filtration device, or a coagulation sedimentation device may be installed in the front stage of the cation exchange device 102, and a post-treatment device such as EDI (Electro DeIonization) or a degassing device may be installed in the rear stage.

[0053] Here, the electrodialysis device 300 in the waste liquid treatment system 500 shown in FIG. 5 can use the electrodialysis device 300 shown in FIG. 3. And the waste liquid treatment system 500 having the above configuration includes an acid liquid circulation mechanism in which the first water storage tank 108 communicates with the acid recovery chamber (acid recovery chamber 22 in FIG. 3), an alkali liquid circulation mechanism in which the second water storage tank 110 communicates with the alkali recovery chamber (alkali recovery chamber 32 in FIG. 3), a deionized water circulation mechanism in which the regenerated waste liquid storage tank 106 communicates with the deionization chamber (deionization chamber 24 in FIG. 3), an electrode liquid circulation mechanism in which the electrode liquid storage tank 112 communicates with the anode chamber (anode chamber 20 in FIG. 3) and the cathode chamber (cathode chamber 34 in FIG. 3), a recovered acid liquid feeding mechanism that branches from the acid liquid circulation mechanism and communicates with the regenerated liquid storage tank 104, a recovered alkali liquid feeding mechanism that branches from the alkali liquid circulation mechanism and feeds the recovered alkali liquid out of the system, and a pH sensor 36 (pH measuring means) that measures the pH of the treatment liquid obtained after the regenerated waste liquid of the cation exchanger passes through the deionization chamber of the electrodialysis device 300. When the pH value measured by the pH measuring means reaches a predetermined value, the electrodialysis treatment is terminated, the recovered acid liquid is fed to the regenerated liquid storage tank 104 through the recovered acid liquid feeding mechanism, and the recovered alkali liquid is fed to the place where the recovered alkali liquid outside the system is used through the recovered alkali liquid feeding mechanism. Further, the recovered acid liquid feeding mechanism may be a mechanism for feeding the liquid out of the system, and the recovered acid liquid may be fed to a place where the recovered acid liquid outside the system is used (for example, the regenerated liquid storage tank of the anion exchange device as the place where the regenerated acid liquid is used).

[0054] As the pH measuring means, a pH sensor 36 can be provided at the outlet of the deionization chamber of the electrodialysis device 300, and this electrodialysis device is provided with a DC power supply (not shown) for supplying electricity to the electrodialysis device. These pH sensor 36 and DC power supply are connected to a control device (not shown) such as a personal computer, and the control device can control the current from the DC power supply applied to the cathode and anode of the electrodialysis device 300 based on the pH data of the treatment liquid transmitted from the pH sensor 36.

[0055] FIG. 6 shows an example of a waste liquid treatment system for treating the regeneration waste liquid of an anion exchanger (anion exchange resin). The waste liquid treatment system 600 according to an embodiment of the present invention is the same as the waste liquid treatment system of FIG. 5 except for the following points, and includes an anion exchange device 103 instead of the cation exchange device 102 in FIG. 5, and includes an electrodialysis device 400 instead of the electrodialysis device 300. The waste liquid treatment system 600 according to an embodiment of the present invention includes an anion exchange device 103 filled with an anion exchanger, a regeneration liquid storage tank 104 for storing a solution (regeneration liquid) for regenerating the anion exchanger, and a regeneration waste liquid storage tank 106 for storing the regeneration waste liquid of the anion exchanger. A regeneration liquid flow line L1 for flowing the regeneration liquid to the anion exchange device 103 is provided in the regeneration liquid storage tank 104. And the waste liquid treatment system 600 includes a first water storage tank 108, a second water storage tank 110, an electrode liquid storage tank 112, and an electrodialysis device 400.

[0056] The waste liquid treatment system 600 performs ion exchange treatment on a liquid to be treated such as groundwater or industrial water with the anion exchange device 103 to produce anion-exchanged water. When a predetermined water flow rate is reached, the flow of the liquid to be treated to the anion exchange device 103 is stopped, and the regeneration liquid stored in the regeneration liquid storage tank 104 is flowed through the line L1 to the anion exchange device 103. The regeneration liquid that has passed through the anion exchange device 103 is stored in the regeneration waste liquid storage tank 106 as regeneration waste liquid. The anion exchange device 103 after regeneration is again passed through the liquid to be treated to perform ion exchange treatment to produce anion-exchanged water. A pretreatment device such as a membrane treatment device, an activated carbon filtration device, or a coagulation sedimentation device may be installed in the front stage of the anion exchange device 103, and a post-treatment device such as EDI (Electro DeIonization) or a deaeration device may be installed in the rear stage.

[0057] Here, as the electrodialysis device 400 in the waste liquid treatment system 500 shown in FIG. 6, the electrodialysis device 400 shown in FIG. 4 can be used. And the waste liquid treatment system 600 having the above configuration includes an acid liquid circulation mechanism in which the first water storage tank 108 communicates with the acid recovery chamber (acid recovery chamber 22 in FIG. 4), an alkali liquid circulation mechanism in which the second water storage tank 110 communicates with the alkali recovery chamber (alkali recovery chamber 32 in FIG. 4), a deionized water circulation mechanism in which the regenerated waste liquid storage tank 106 communicates with the deionization chamber (deionization chamber 30 in FIG. 4), an electrode liquid circulation mechanism in which the electrode liquid storage tank 112 communicates with the anode chamber (anode chamber 20 in FIG. 4) and the cathode chamber (cathode chamber 34 in FIG. 4), a recovered alkali liquid feeding mechanism branched from the alkali liquid circulation mechanism and communicating with the regenerated liquid storage tank 104, a recovered acid liquid feeding mechanism branched from the acid circulation mechanism and feeding the recovered acid liquid out of the system, and pH measuring means (pH sensor 36) for measuring the pH of the treatment liquid obtained after the regenerated waste liquid of the anion exchanger passes through the deionization chamber of the electrodialysis device 400. When the pH value measured by the pH measuring means reaches a predetermined value, the electrodialysis treatment is terminated, the recovered alkali liquid is fed to the regenerated liquid storage tank 104 through the recovered alkali liquid feeding mechanism, and the recovered acid liquid is fed to the place where the recovered acid liquid outside the system is used through the recovered acid liquid feeding mechanism. The recovered alkali liquid feeding mechanism may be a mechanism for feeding the liquid out of the system, and the recovered alkali liquid may be fed to a place where the recovered alkali liquid outside the system is used (for example, the regenerated liquid storage tank of the cation exchange device as the place where the regenerated alkali liquid is used).

[0058] As the pH measuring means, a pH sensor 36 can be provided at the outlet of the deionization chamber of the electrodialysis device 400. The electrodialysis device is provided with a DC power supply (not shown) for supplying electricity to the electrodialysis device. The pH sensor 36 and the DC power supply are connected to a control device (not shown) such as a personal computer. The control device can control the current from the DC power supply applied to the cathode and anode of the electrodialysis device 400 based on the pH data of the treatment liquid transmitted from the pH sensor 36.

[0059] (Management of the End Point of Electrodialysis Based on pH) In this way, by controlling the end point of electrodialysis based on the pH of the treatment liquid, it is possible to prevent the scale components from mixing into the recovered acid liquid and the recovered alkaline liquid, and to obtain a liquid quality suitable as the regeneration liquid for the ion exchange device.

[0060] For example, in the method of observing and determining the pH change, a pH meter may be installed at the outlet of the deionization chamber, in the regeneration waste liquid storage tank, in the first water storage tank or in the second water storage tank, and the measured value may be transmitted to the control device at predetermined intervals. When the pH reaches a predetermined value (range) or when the inclination of the change is within a predetermined range, the electrodialysis is terminated. For example, regarding the tendency of the pH change, the water in the first water storage tank gradually decreases in pH from near neutral due to the influence of the generation of the acid liquid as described above, and stabilizes at a low value after a certain period of time. The water in the second water storage tank gradually increases in pH from near neutral due to the influence of the generation of the alkaline liquid as described above, and stabilizes at a high value after a certain period of time. Also, when the liquid in the regeneration waste liquid storage tank is the cation exchanger regeneration waste liquid, due to the influence of the ions in the cation exchanger regeneration waste liquid moving to the chamber adjacent to the deionization chamber, the pH of the cation exchanger regeneration waste liquid gradually increases from the acidic side, and stabilizes on the neutral side or the alkaline side from the initial value after a certain period of time. On the other hand, when the liquid in the regeneration waste liquid storage tank is the anion exchanger regeneration waste liquid, due to the influence of the ions in the anion exchanger regeneration waste liquid moving to the chamber adjacent to the deionization chamber, the pH of the anion exchanger regeneration waste liquid gradually decreases from the alkaline side, and stabilizes on the neutral side or the acidic side from the initial value after a certain period of time.

[0061] When subjecting an acid supply liquid (pH ≦ 3, preferably pH < 1) to electrodialysis treatment in a three-chamber electrodialysis device (see Fig. 3), when the acid supply liquid is subjected to electrodialysis, first, H + , which is an ion that is easy to move, moves from the acid supply liquid through the cation exchange membrane to the recovered alkaline liquid, and Cl - moves through the anion exchange membrane to the recovered acid liquid. Next, among the ions existing in the form of dissociation of neutral salts such as NaCl and CaCl2 in the acid supply liquid, the cations Na + and Ca 2+ move to the recovered alkaline liquid, and the anion Cl -moves to the recovered acid solution. This is a phenomenon that occurs because the molar conductivity of H + is greater than that of other cations such as Na + and Ca 2+ . The movement of ions occurs while the ions in each solution maintain electrical neutrality. When the movement of H + from the acid supply solution to the recovered alkali solution is almost complete (the pH of the treated solution from the deionization chamber is preferably about 1 to 3, more preferably 2 to 2.5), the electrodialysis treatment is terminated. As a result, the movement of hardness components such as Ca 2+ and Mg 2+ to the recovered alkali solution side can be suppressed, and the formation of scale derived from hardness components in the alkali recovery chamber can be prevented. By setting the end point of electrodialysis to the point when the pH of the treated solution (deionized water) from the deionization chamber becomes 1 or more, the separation of acid and alkali proceeds sufficiently, and by setting it to 3 or less, the movement of hardness components to the recovered alkali solution can be suppressed, and the risk of scale precipitation on the alkali recovery chamber side can be reduced.

[0062] When the acid supply solution (pH ≤ 3, preferably pH < 1) is subjected to electrodialysis treatment in a two-chamber electrodialysis device (see Fig. 1), when the acid supply solution is electrodialyzed, Cl - moves from the acid supply solution to the recovered acid solution, and OH - is supplied to the acid supply solution and the pH increases. When the pH of the treated solution of the acid supply solution reaches about 1 to 3 as in the above case, most of the H + and an equivalent amount of Cl - in the acid supply solution have moved from the acid supply solution to the recovered acid solution, and by terminating the electrodialysis treatment at this point, the formation of scale derived from hardness components in the deionization chamber where the acid supply solution is supplied can be prevented.

[0063] Therefore, when the liquid to be treated supplied to the deionization chamber of the electrodialysis device is an acid supply solution, the end point of electrodialysis is preferably the point when the pH of the treated solution (deionized water) from the deionization chamber becomes 1 or more and 3 or less, more preferably 1.5 or more and 2.5 or less, and even more preferably 2 or more and 2.5 or less. The management of the endpoint of electrodialysis can be achieved by measuring the pH of the treated liquid from the deionization chamber. Since the acid supply liquid after electrolysis is roughly neutralized, the amount of neutralizing chemicals used can be reduced when further neutralizing the treated liquid. Also, the treated liquid can be used for cooling water of cooling facilities, miscellaneous water, etc., or returned to the front stage of the water treatment facility. In addition, in detecting the endpoint of electrodialysis, the pH measurement of the treated liquid from the deionization chamber and the pH measurement of the recovered acid liquid from the acid recovery chamber may be used in combination. For example, the point where the pH of the treated liquid from the deionization chamber is within a predetermined range and the pH of the recovered acid liquid becomes <0.5 can also be set as the endpoint.

[0064] When subjecting an alkali supply liquid (pH ≧ 12, preferably pH > 13) to electrodialysis treatment with a three-compartment electrodialysis device (see Fig. 4), when the alkali supply liquid is electrodialyzed, first, OH - permeates through the anion exchange membrane and moves, and the pH of the alkali supply liquid decreases. As the pH decreases, silica-derived scale is likely to form. Therefore, by ending the electrodialysis treatment at the point before silica scale precipitates, that is, when the pH of the treated liquid (deionized water) from the deionization chamber does not become too low (preferably 9 or more, more preferably 10 or more), the generation of silica scale can be prevented. Also, by setting the endpoint of this electrodialysis to the point when the pH of the treated liquid (deionized water) from the deionization chamber preferably reaches less than 12, more preferably 11.5 or less, the separation can proceed more sufficiently. In addition, in detecting the endpoint of electrodialysis, the pH measurement of the treated liquid from the deionization chamber and the pH measurement of the recovered alkali liquid from the alkali recovery chamber may be used in combination. For example, the point where the pH of the treated liquid from the deionization chamber is within a predetermined range and the pH of the recovered alkali liquid becomes > 13 can also be set as the endpoint.

[0065] When subjecting an alkali supply liquid (pH ≧ 12, preferably pH > 13) to electrodialysis treatment with a two-compartment electrodialysis device (see Fig. 2), when the alkali supply liquid is electrodialyzed, Na in the alkali supply liquid + permeates through the cation exchange membrane and moves, and H is added to the alkali supply liquid +Since it is supplied, the pH decreases. As the pH decreases, scale derived from silica is likely to form. Therefore, by ending electrodialysis at a point before silica scale precipitates, that is, when the pH of the treated liquid (deionized water) from the deionization chamber does not become too low (preferably 9 or higher, more preferably 10 or higher), generation of silica scale can be prevented in the same manner as when subjecting the alkali supply liquid to electrodialysis treatment in the above-described three-chamber electrodialysis device. Further, by setting the end point of this electrodialysis to the point when the pH of the treated liquid (deionized water) from the deionization chamber preferably reaches less than 12, more preferably 11.5 or less, separation can proceed more sufficiently. Also, similar to the case of subjecting the alkali supply liquid to electrodialysis treatment in the above-described three-chamber electrodialysis device, measurement of the pH of the treated liquid from the deionization chamber and measurement of the pH of the recovered alkali liquid from the alkali recovery chamber may be used in combination. For example, the end point can also be set at the point when the pH of the treated liquid from the deionization chamber becomes a value within a predetermined range and the pH of the recovered alkali liquid becomes >13.

[0066] Therefore, when the liquid to be treated supplied to the deionization chamber of the electrodialysis device is an alkali supply liquid, the end point of electrodialysis is preferably the point before the pH of the treated liquid (deionized water) from the deionization chamber reaches a range less than 9 after decreasing from a value of 12 or higher before treatment. Further, the end point of this electrodialysis is preferably the point when the pH of the treated liquid (deionized water) from the deionization chamber reaches less than 12 after decreasing from a value of 12 or higher (preferably pH > 13) before treatment, and more preferably the point when it reaches 11.5 or less.

[0067] (Acid recovery chamber 22 and alkali recovery chamber 32 of the electrodialysis device) In the acid recovery chamber 22 (the cell from which the recovered acid solution flows out) or the alkali recovery chamber 32 (the cell from which the recovered alkali solution flows out) of the above-described electrodialysis device, water is pressure-fed by a liquid-feeding means such as a pump, and is recovered as an acid solution from the acid recovery chamber 22 and as an alkali solution from the alkali recovery chamber 32, and can be reused as a regenerant for a resin tower, a neutralizing agent for waste liquid, etc. The reuse destinations of the recovered acid solution and alkali solution may be the same series of water treatment systems or different water treatment systems. When used in a different water treatment system, the recovered acid solution and alkali solution can be reused efficiently. The water supplied to the acid recovery chamber 22 and the alkali recovery chamber 32 is preferably pure water, but acidic or alkaline water suitable for reuse as a regenerant or a neutralizing agent for a resin tower can be used.

[0068] (Anode chamber 20 and cathode chamber 34 of the electrodialysis device) In the anode chamber 20 (the cell defined by the first bipolar membrane and the anode) and the cathode chamber 34 (the cell defined by the second bipolar membrane and the cathode) of the above-described electrodialysis device, an electrode solution is passed through. As the electrode solution, an aqueous solution of a metal hydroxide or a metal salt such as an aqueous NaOH solution or an aqueous Na2SO4 solution can be used.

[0069] (Separation of ions in the liquid to be treated by the electrodialysis device) In the above-described three-chamber electrodialysis device, H + or OH - originally present in the dissociation state in the supply liquid (acid supply liquid, alkali supply liquid) can be selectively separated from the supply liquid (liquid to be treated). Thereby, separation can be performed with high current efficiency, and the time required for separation can be shortened. Due to the nature of electrodialysis, usually, when separating ions up to those that become neutral salts when considered as compounds, such as Cl + and Ca 2+ which are present in an equivalent amount to Na - and SO4 2- and Cl - and Na + etc., the amount of ions in the supply liquid decreases, so it becomes difficult for current to flow, the current efficiency decreases, and the time required for separation becomes longer. Therefore, H + ​- It is desirable to preferentially separate and separate as much as possible from the supply liquid (liquid to be treated), and not to separate as much as possible the ions that will become other neutral salts.

[0070] In the above-described two-chamber electrodialysis apparatus, since ions equivalent to the ions that have permeated the ion exchange membrane are replenished to the supply liquid (liquid to be treated), the conductivity of the supply liquid does not decrease significantly and the current efficiency does not change, but the effect of suppressing scale can be obtained in the same manner as in the three-chamber recovery electrodialysis apparatus.

[0071] (Regenerated waste liquid) In the present invention, H that originally existed in a dissociated state in the supply liquid (acid supply liquid, alkali supply liquid) to the electrodialysis apparatus + or OH - can be selectively separated, so it is not always necessary to mix the regeneration acid waste liquid (acid supply liquid) of the cation exchanger and the regeneration alkali waste liquid (alkali supply liquid) of the anion exchanger. If there is a place in another system in the factory where these regeneration acid waste liquids and regeneration alkali waste liquids can be reused, for example, only the regeneration acid waste liquid can be electrodialyzed and recovered, and the regeneration alkali waste liquid can be used for neutralization treatment in another system. Also, by treating the regeneration acid waste liquid and the regeneration alkali waste liquid separately without mixing them, H in a dissociated state contained in each waste liquid + and OH - can be ensured, so the amounts of acid and alkali that can be recovered by the present invention are larger than when the waste liquids are mixed. Thus, the present invention has the advantage that the regeneration waste liquid of the ion exchanger can be used without mixing it with the regeneration waste liquid of other ion exchangers.

[0072] (Treatment target of electrodialysis system / electrodialysis method) The liquid to be treated (liquid to be processed) in the electrodialysis system and electrodialysis method of the present invention is not particularly limited as long as it is either an acidic liquid (acid supply liquid) with a pH of 3 or less or an alkaline liquid (alkali supply liquid) with a pH of 12 or more, but it is preferably a regeneration waste liquid discharged during the regeneration treatment of an ion exchanger, and particularly preferably a regeneration waste liquid discharged during the regeneration treatment of an ion exchange resin used for groundwater treatment or industrial water treatment for pure water production in a semiconductor factory or the like. Further, when the liquid to be treated (liquid to be processed) is an acidic liquid (acid supply liquid), it is particularly preferable that its pH is less than 1 (pH < 1), and when it is an alkaline liquid (alkali supply liquid), it is particularly preferable that its pH is higher than 13 (pH > 13).

Example

[0073] (Example 1) The regeneration waste liquid of the cation exchange resin was supplied as an acid supply liquid to the three-compartment electrodialysis apparatus shown in Fig. 3 and subjected to electrodialysis treatment under the following conditions to obtain a regenerated acid (treated liquid). · Apparatus: Bipolar membrane electrodialysis apparatus manufactured by Asahi Kasei Corporation (Product name: Asiraizer EX3B) · Supply liquid: Regeneration waste liquid of a cation exchange resin tower for pure water production. The water quality is shown in the following table (Table 1). · Supply liquid volume and circulation flow rate: 850 ml, 1.4 L / min · Amount and circulation flow rate of the recovered acid liquid: 850 ml, 1.4 L / min · Amount and circulation flow rate of the recovered alkali liquid: 850 ml, 1.4 L / min · Voltage value: 10 V The pH of the treated liquid after the supply liquid passed through the electrodialysis apparatus was measured with a portable pH meter (Product name: HM-40P) manufactured by Toa DKK Corporation (glass electrode method). The ions in the supply liquid and the treated liquid were measured by an ion chromatograph (Product name: Dionex Integrion) manufactured by Thermo Fisher Scientific K.K. (ion chromatograph method). The water quality (pH and component concentration) of the supply liquid (regeneration waste liquid) is shown in Table 1.

[0074]

Table 1

[0075] Changes in the component concentration, pH value, and current value of the electro-dialyzed regenerated waste liquid (treated liquid) with respect to the operation time (dialysis time) of the electrodialysis device are shown in FIGS. 7 and 8. In addition, Table 2 shows the water quality (pH and component concentration) of the regenerated waste liquid (treated liquid) during electrodialysis. The regenerated waste liquid was supplied to the electrodialysis device to start electrodialysis, and the voltage at that time was set to 10V. From the start of operation (start of dialysis) until about 23 minutes, the Cl - concentration decreased significantly, but the cation concentration (H + excluding, Na + , Ca + , Mg + , K + total concentration T-Cation) decreased less than the decrease in the Cl - concentration. Originally, in order to maintain electrical neutrality, the slopes of the Cl - concentration and the cation concentration should be the same, but they are different in the section from the start of operation until about 23 minutes. From this, it can be seen that in this section, as cations, H + in HCl in the regenerated waste liquid moves, and the movement amount of Na + in NaCl is small. Therefore, the pH of the electro-dialyzed regenerated waste liquid (treated liquid) is increasing.

[0076] When 23 minutes have elapsed from the start of operation (start of dialysis), the Na + concentration and the Cl - concentration have decreased almost equivalently (Table 2). This is because the excess H + in the regenerated waste liquid has decreased due to electrodialysis, so the separation of NaCl is progressing. The H + of the regenerated waste liquid is almost neutralized and the pH has increased, exceeding 2 after 43 minutes (Table 2, FIG. 7).

[0077] On the one hand, as shown in Fig. 8, the current value gradually decreases from around 23 minutes. It is considered that the current value decreases as the ion concentration in the regenerated waste liquid decreases due to electrodialysis. From around 60 minutes, the current value decreases even more rapidly.

[0078] When the pH of the regenerated waste liquid supplied as the acid supply liquid reaches within the range of 1 to 3 after passing through the electrodialysis apparatus, in this example, for example, at a time point within the range of 8 to 43 minutes (pH 1.3 to 2.1) from the start of operation (start of dialysis), it can be seen that the acid can be recovered in a short time by stopping the electrodialysis.

[0079] During electrodialysis, no rapid decrease in the current value due to scale formation was observed, and no scale substance was visible even when visually observing the ion exchange membrane surface after electrodialysis.

[0080]

Table 2

[0081] (Example 2) The regenerated waste liquid of the anion exchange resin was supplied as an alkali supply liquid to the two-compartment electrodialysis apparatus shown in Fig. 2 and subjected to electrodialysis treatment under the following conditions to obtain a regenerated alkali (treated liquid). · Apparatus: Bipolar membrane electrodialysis apparatus manufactured by Asahi Kasei Corporation (Product name: Asiraizer EX3B) · Supply liquid: Regenerated waste liquid of an anion exchange resin tower for pure water production. The water quality is described in the following table (Table 3) · Supply liquid volume and circulation flow rate: 850 ml, 1.4 L / min · Amount of recovered alkali liquid and circulation flow rate: 850 ml, 1.4 L / min · Voltage value: 12 V The pH of the treated liquid after the supply liquid passed through the electrodialysis apparatus was measured with a portable pH meter (Product name: HM-40P (glass electrode method)) manufactured by Toa DKK Corporation. Ions in the feed solution and the treatment solution were measured by an ion chromatograph (product name: Dionex Integrion) manufactured by Thermo Fisher Scientific Inc. (ion chromatography method). Table 3 shows the water quality (pH and component concentrations) of the feed solution (regenerated waste solution).

[0082]

Table 3

[0083] Changes in the Na concentration, pH value, and current value of the regenerated waste solution (treatment solution) electrodialyzed with respect to the operation time (dialysis time) of the electrodialysis device are shown in Figs. 9 and 10. Table 4 shows the water quality (pH and component concentrations) of the regenerated waste solution (treatment solution) during electrodialysis. + The regenerated waste solution was supplied to the electrodialysis device to start dialysis, and the voltage at that time was set to 12V. Since the Na concentration is decreasing from the start of operation (start of dialysis), and H is supplied to the feed solution (regenerated waste solution), the pH is gradually decreasing. At around 31 minutes from the start of operation (start of dialysis), the pH is rapidly decreasing. This is due to the almost complete neutralization of OH in the feed solution (regenerated waste solution). After this, not only Na but also H mainly moves. Therefore, after this, the ion movement and separation do not proceed sufficiently. + +

[0084] - + + On the other hand, as shown in Fig. 10, the current value is almost constant after 21 minutes from the start of operation (start of dialysis).

[0085] It can be seen that in this example, the alkali can be recovered in a short time by stopping the electrodialysis at the time when the pH of the regenerated waste solution (pH ≧ 12) supplied as the alkali feed solution reaches 9 after passing through the electrodialysis device. For example, at the time of 21 minutes (pH 11.1) from the start of operation (start of dialysis).

[0086] ​​​​​​During electrodialysis, no rapid decrease in current value due to scale formation was observed, and no scale substance was visible even when visually observing the ion exchange membrane surface after electrodialysis.

[0087]

Table 4

[0088] (Comparative Example 1) Electrodialysis was performed in the same manner as in Example 1 except that the operation time (dialysis time) was set to 100 minutes. As a result, the current value became almost zero, and white scale was confirmed on the cation exchange membrane surface. This is considered to be due to the precipitation of components such as Ca(OH)2 and Mg(OH)2.

[0089] (Comparative Example 2) Electrodialysis was performed in the same manner as in Example 2 except that the operation time (dialysis time) was set to 90 minutes. As a result, there was no significant change in the current value, but gel-like deposits were confirmed on the bipolar membrane surface. This is considered to be due to the precipitation of SiO2.

Explanation of Symbols

[0090] 1 Anode 3 First bipolar membrane 5 Anion exchange membrane 7 Cation exchange membrane 9 Second bipolar membrane 11 Cathode 20 Anode chamber 22 Acid recovery chamber 24, 30 Deionized chamber 32 Alkali recovery chamber 34 Cathode chamber 36 pH measurement means 100 Two-chamber acid recovery electrodialysis apparatus 102 Cation exchange apparatus 103 Anion exchange apparatus 104 Regenerated liquid storage tank 106 Regenerated waste liquid storage tank 108 First water storage tank 110 Second water storage tank 112 Electrolyte Reservoir 200 Two - chambered Alkali Recovery Electrodialysis Device 300 Three - chambered Acid Recovery Electrodialysis Device 400 Three - chambered Alkali Recovery Electrodialysis Device 500 Waste Liquid Treatment System for Regenerated Waste Liquid of Cation Exchanger 600 Waste Liquid Treatment System for Regenerated Waste Liquid of Anion Exchanger

Claims

1. An electrodialysis system for treating a liquid to be treated having a pH of 3 or less or 12 or more, comprising: at least an anode, a cathode, a first bipolar membrane, an ion exchange membrane, and a second bipolar membrane, wherein the first bipolar membrane, the ion exchange membrane, and the second bipolar membrane are arranged in this order from the anode side between the anode and the cathode; an electrodialysis device; pH measuring means for measuring the pH of the treated liquid obtained after the liquid to be treated passes through the electrodialysis device; An electrodialysis system that terminates the electrodialysis treatment by the electrodialysis device when the pH value of the treated liquid measured by the pH measuring means reaches a predetermined value.

2. The electrodialysis system according to claim 1, wherein the liquid to be treated has a pH of 3 or less, and the ion exchange membrane of the electrodialysis device is an anion exchange membrane.

3. The electrodialysis system according to claim 1, wherein the liquid to be treated has a pH of 12 or more, and the ion exchange membrane of the electrodialysis device is a cation exchange membrane.

4. The electrodialysis system according to claim 1, wherein the ion exchange membrane of the electrodialysis device is an anion exchange membrane, and a cation exchange membrane is provided between the anion exchange membrane and the second bipolar membrane.

5. In the electrodialysis device, an anode chamber defined by the anode and the first bipolar membrane; a cathode chamber defined by the cathode and the second bipolar membrane; are arranged, an acid recovery chamber defined by the first bipolar membrane and the anion exchange membrane between the anode chamber and the cathode chamber, to which water is supplied to generate a recovered acid solution by electrodialysis treatment; a deionization chamber defined by the anion exchange membrane and the second bipolar membrane, to which an acid supply solution is supplied as the liquid to be treated to generate deionized water by electrodialysis treatment; and The electrodialysis system according to claim 2, wherein one or two or more cell sets composed of the acid recovery chamber and the deionization chamber are arranged.

6. In the electrodialysis device, an anode chamber defined by the anode and the first bipolar membrane; a cathode chamber defined by the cathode and the second bipolar membrane; are arranged, a deionization chamber defined by the first bipolar membrane and the cation exchange membrane between the anode chamber and the cathode chamber, to which an alkali supply solution is supplied as the liquid to be treated to generate deionized water by electrodialysis treatment; An alkali recovery chamber defined by the cation exchange membrane and the second bipolar membrane, to which water is supplied to generate a recovered alkali solution by electrodialysis treatment. The electrodialysis system according to claim 3, wherein one or two or more cell sets composed of the deionized chamber and the alkali recovery chamber are arranged.

7. In the electrodialysis device, An anode chamber defined by the anode and the first bipolar membrane, A cathode chamber defined by the cathode and the second bipolar membrane are arranged, Between the anode chamber and the cathode chamber, an alkali recovery chamber defined by the cation exchange membrane and the second bipolar membrane, to which water is supplied to generate a recovered alkali solution by electrodialysis treatment, An acid recovery chamber defined by the anion exchange membrane and the first bipolar membrane, to which water is supplied to generate a recovered acid solution by electrodialysis treatment, A deionized chamber defined by the cation exchange membrane and the anion exchange membrane, to which the liquid to be treated is supplied to generate deionized water by electrodialysis treatment, is provided. The electrodialysis system according to claim 4, wherein one or two or more cell sets composed of the acid recovery chamber, the deionized chamber, and the alkali recovery chamber are arranged.

8. The pH of the liquid to be treated is less than 1, When the pH of the treated liquid reaches a range of 1 or more and 3 or less, the electrodialysis treatment by the electrodialysis device is terminated. The electrodialysis system according to claim 2 or 4.

9. The pH of the liquid to be treated is 12 or more, Before the pH of the treated liquid reaches a range of less than 9, the electrodialysis treatment by the electrodialysis device is terminated. The electrodialysis system according to claim 3 or 4.

10. The electrodialysis system according to any one of claims 1 to 7, wherein the liquid to be treated is a regeneration waste liquid of an ion exchange device.

11. The recovered acid solution is used in a water treatment system different from the water treatment system that discharges the liquid to be treated. The electrodialysis system according to claim 5 or 7.

12. The recovered alkali solution is used in a water treatment system different from the water treatment system that discharges the liquid to be treated. The electrodialysis system according to claim 6 or 7.

13. An ion exchange device filled with an ion exchanger, A regeneration liquid supply device that supplies a regeneration liquid for the ion exchanger to the ion exchange device, And an electrodialysis system that treats the regeneration waste liquid discharged from the ion exchange device. The regenerated waste liquid has a pH of 3 or less or a pH of 12 or more, The electrodialysis system has at least an anode, a cathode, a first bipolar membrane, an ion exchange membrane, and a second bipolar membrane, and an electrodialysis device in which the first bipolar membrane, the ion exchange membrane, and the second bipolar membrane are arranged in this order from the anode side between the anode and the cathode, pH measuring means for measuring the pH of the treatment liquid obtained after the regenerated waste liquid passes through the electrodialysis device, A waste liquid treatment system that ends the electrodialysis treatment by the electrodialysis device when the pH value of the treatment liquid measured by the pH measuring means reaches a predetermined value.

14. An electrodialysis method for treating a liquid to be treated having a pH of 3 or less or a pH of 12 or more, having at least an anode, a cathode, a first bipolar membrane, an ion exchange membrane, and a second bipolar membrane, and performing electrodialysis treatment using an electrodialysis device in which the first bipolar membrane, the ion exchange membrane, and the second bipolar membrane are arranged in this order from the anode side between the anode and the cathode, measuring the pH of the treatment liquid obtained after the liquid to be treated passes through the electrodialysis device, An electrodialysis method that ends the electrodialysis treatment by the electrodialysis device when the measured pH value of the treatment liquid reaches a predetermined value.

15. A regenerated liquid supply step of supplying a regenerated liquid of the ion exchanger to an ion exchange device filled with the ion exchanger, an electrodialysis step of treating the regenerated waste liquid discharged from the ion exchange device, The regenerated waste liquid has a pH of 3 or less or a pH of 12 or more, The electrodialysis step has at least an anode, a cathode, a first bipolar membrane, an ion exchange membrane, and a second bipolar membrane, and a step of passing the regenerated waste liquid through an electrodialysis device in which the first bipolar membrane, the ion exchange membrane, and the second bipolar membrane are arranged in this order from the anode side between the anode and the cathode and performing electrodialysis treatment, a step of measuring the pH of the treatment liquid obtained after the regenerated waste liquid passes through the electrodialysis device, A waste liquid treatment method that ends the electrodialysis treatment by the electrodialysis device when the pH value of the treatment liquid measured in the step of measuring the pH reaches a predetermined value.

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