Electrodialysis device, electrodialysis method, wastewater treatment device, and wastewater treatment method

Abstract

Provided is an electrodialysis device capable of preventing formation of scaling on an ion exchange membrane surface and performing stable acid recovery without increasing costs. This electrodialysis device comprises at least an anode, a cathode, a first bipolar membrane, an anion exchange membrane, a cation exchange membrane, and a second bipolar membrane in the stated order, and further comprises: an anode chamber demarcated by the anode and the first bipolar membrane; an acid recovery chamber demarcated by the first bipolar membrane and the anion exchange membrane; a desalination chamber demarcated by the anion exchange membrane and the cation exchange membrane; a waste acid chamber demarcated by the cation exchange membrane and the second bipolar membrane; and a cathode chamber demarcated by the second bipolar membrane and the cathode. Water is supplied to the acid recovery chamber, an acidic solution is supplied to the desalination chamber, and waste acid is supplied to the waste acid chamber to perform electrodialysis treatment.

Description

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

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

[0002] Ion exchangers have been used in a variety of applications, including in pure water production systems. Generally, pure water production systems include a cation exchanger-packed device, a decarbonation device, and an anion exchanger-packed device, and raw water is passed through these devices in order to remove cation components from the water to be treated in the cation exchanger-packed device, carbon dioxide gas in the decarbonation device, and anion components in the anion exchanger-packed device, thereby producing pure water.

[0003] However, after a certain period of use, cation exchangers and anion exchangers become saturated and are no longer able to exchange ions. Therefore, saturated ion exchangers must be regenerated. To fully regenerate saturated ion exchangers, large amounts of acid or alkaline solution must be used as regeneration liquids. Furthermore, the acid or alkaline solution used for regeneration is treated as waste liquid (regeneration waste liquid) and subjected to neutralization or other treatments. The neutralization process for this waste liquid also requires large amounts of acid or alkaline, resulting in issues such as increased chemical consumption and increased salt concentration in the waste liquid. Therefore, there is a need to recover the waste liquid (regeneration waste liquid) from the perspectives of reducing chemical consumption, reducing processing costs, and mitigating environmental impact.

[0004] In the recovery of the above-mentioned regeneration waste liquid, it is necessary to remove trace amounts of impurities, such as cations (potassium, sodium, calcium, magnesium, ammonium ions, etc.) or anions (chloride ions, sulfate ions, nitrate ions, etc.), which are present in highly concentrated waste acid and waste alkaline solutions. Electrodialysis is one method for removing ions, and a method has been proposed in which the regeneration waste liquid is treated by electrodialysis to recover the acid and alkali.

[0005] For example, Patent Document 1 describes a treatment method in which regeneration wastewater generated in a process for regenerating an ion exchange resin with hydrochloric acid and sodium hydroxide is passed through an electrodialysis device to separate it into hydrochloric acid and sodium hydroxide, and the regeneration wastewater is added with a membrane fouling inhibitor that has an effect of inhibiting calcium deposition and prevents calcium from adhering to membranes and causing scaling.

[0006] Japanese Patent Application Publication No. 11-566

[0007] However, the method described in Patent Document 1 requires the addition of a membrane fouling inhibitor to the regenerated waste liquid, which increases the amount of chemicals used and raises costs.On the other hand, in various factories, particularly semiconductor factories, a large amount of waste acid liquid is discharged after being used in cleaning processes such as SPM cleaning (sulfuric acid-hydrogen peroxide mixture cleaning), and in many cases, the waste acid liquid is neutralized, treated, and then released, and there is a demand for the development of other uses for such waste acid liquid.

[0008] An object of the present invention is to provide an electrodialysis apparatus and an electrodialysis method which can prevent scale formation on the ion exchange membrane surface of the electrodialysis apparatus and enable stable acid recovery at low cost, as well as a waste liquid treatment apparatus equipped with the electrodialysis apparatus, and a waste liquid treatment method using the electrodialysis apparatus.

[0009] As a result of extensive research into the above-mentioned problems, the present inventors have found that acid can be efficiently recovered from waste liquid by electrodialysis using an electrodialysis device having a specific structure, and have thus completed the present invention.

[0010] The present invention includes the following aspects: [1] An electrodialysis apparatus comprising at least an anode, a cathode, a first bipolar membrane, an anion exchange membrane, a cation exchange membrane, and a second bipolar membrane, wherein the first bipolar membrane, the anion exchange membrane, the cation exchange membrane, and the second bipolar membrane are arranged in this order from the anode side between the anode and the cathode, and wherein the electrodialysis apparatus comprises an anode chamber defined by the anode and the first bipolar membrane, an acid recovery chamber defined by the first bipolar membrane and the anion exchange membrane, a deionization chamber defined by the anion exchange membrane and the cation exchange membrane, a spent acid chamber defined by the cation exchange membrane and the second bipolar membrane, and a cathode chamber defined by the second bipolar membrane and the cathode, wherein water is supplied to the acid recovery chamber, an acidic solution is supplied to the deionization chamber, and spent acid is supplied to the spent acid chamber to perform electrodialysis. [2] The electrodialysis apparatus according to [1], wherein the waste acid is a waste acid discharged from a semiconductor factory. [3] The electrodialysis apparatus according to [1] or [2], wherein the acidic solution is a regeneration waste liquid of a cation exchanger. [4] The electrodialysis apparatus according to [1] or [2], wherein the waste acid is an aqueous sulfuric acid solution, and the sulfuric acid concentration of the waste acid is in the range of 1 to 20 mass%. [5] The electrodialysis apparatus according to [1] or [2], further comprising a pH measurement means for measuring the pH of the waste acid, wherein the pH of the waste acid measured by the pH measurement means is less than 2 throughout the entire electrodialysis period.[6] The electrodialysis apparatus according to [1] or [2], comprising: an acid solution storage tank for storing the acid solution to be supplied to the deionization compartments; an acid solution circulation path for circulating the treated acid solution discharged from the deionization compartments back to the acid solution storage tank; an acid solution circulation device for circulating the acid solution through the acid solution storage tank and the acid solution circulation path; at least one of a current measuring device for measuring the current value between the anode and the cathode during electrodialysis treatment, a conductivity measuring means for measuring the conductivity of the water or the acid solution, and a pH measuring means for measuring the pH of the water or the acid solution; and a control device for controlling the operation of the acid solution circulating device and receiving values ​​measured by at least one of the current measuring device, the conductivity measuring means, and the pH measuring means, wherein the control device circulates the acid solution using the acid solution circulating device during electrodialysis treatment, and, when a value of at least one selected from a slope of the current value, the current, the conductivity, and the pH falls within a predetermined range, replaces the circulating acid solution with the acid solution outside the circulation system at a predetermined ratio or discharges the circulating acid solution outside the circulation system. [7] The electrodialysis apparatus according to [1] or [2], further comprising: a nanofiltration device that separates the acidic solution into a permeate and a concentrate using a nanofiltration membrane; and a line for supplying the permeate to the deionization compartment. [8] An electrodialysis method for treating an acidic solution containing hardness components, comprising an electrodialysis apparatus having at least an anode, a cathode, a first bipolar membrane, an anion exchange membrane, a cation exchange membrane, and a second bipolar membrane, wherein the first bipolar membrane, the anion exchange membrane, the cation exchange membrane, and the second bipolar membrane are arranged in this order from the anode side between the anode and the cathode, an anode chamber defined by the anode and the first bipolar membrane, an acid recovery chamber defined by the first bipolar membrane and the anion exchange membrane, a deionization chamber defined by the anion exchange membrane and the cation exchange membrane, a waste acid chamber defined by the cation exchange membrane and the second bipolar membrane, and a cathode chamber defined by the second bipolar membrane and the cathode, the method comprising: supplying water to the acid recovery chamber; and supplying the acidic solution to the deionization chamber. The electrodialysis method comprises supplying waste acid to the waste acid chamber and carrying out electrodialysis treatment.[9] A cation exchange device filled with a cation exchanger; a regenerated liquid storage tank for storing a regenerated liquid of the cation exchanger; and an electrodialysis device for treating regenerated waste liquid discharged from the cation exchange device to which the regenerated liquid has been supplied, wherein the electrodialysis device has at least an anode, a cathode, a first bipolar membrane, an anion exchange membrane, a cation exchange membrane, and a second bipolar membrane, and the first bipolar membrane, the anion exchange membrane, the cation exchange membrane, and the second bipolar membrane are arranged in this order from the anode side between the anode and the cathode, and the electrodialysis device comprises an anode chamber defined by the anode and the first bipolar membrane, an acid recovery chamber defined by the first bipolar membrane and the anion exchange membrane, a deionization chamber defined by the anion exchange membrane and the cation exchange membrane, and a waste acid chamber defined by the cation exchange membrane and the second bipolar membrane. a cathode chamber defined by the second bipolar membrane and the cathode; a means for supplying water to the acid recovery chamber; a means for supplying an acid solution to the deionization chamber; and a means for supplying waste acid to the waste acid chamber.

[10] A method for electrodialyzing a waste regenerated solution discharged from a cation exchanger, the method comprising: supplying a regenerated solution of the cation exchanger to a cation exchanger filled in the cation exchanger; and subjecting the regenerated waste solution discharged from the cation exchanger to electrodialysis, the electrodialysis comprising: an anode, a cathode, a first bipolar membrane, an anion exchange membrane, a cation exchange membrane, and a second bipolar membrane, the first bipolar membrane, the anion exchange membrane, the cation exchange membrane, and the second bipolar membrane being arranged in this order from the anode side between the anode and the cathode; an anode chamber defined by the anode and the first bipolar membrane; an acid recovery chamber defined by the first bipolar membrane and the anion exchange membrane; a deionization chamber defined by the anion exchange membrane and the cation exchange membrane; and a waste acid chamber defined by the cation exchange membrane and the second bipolar membrane. A waste liquid treatment method using an electrodialysis apparatus having a cathode chamber defined by the second bipolar membrane and the cathode, comprising: supplying water to the acid recovery chamber; supplying the regenerated waste liquid to the demineralization chamber; and supplying waste acid to the waste acid chamber, and performing electrodialysis treatment.

[0011] According to the present invention, it is possible to provide an electrodialysis apparatus and an electrodialysis method, as well as a waste liquid treatment apparatus and a waste liquid treatment method, which can prevent scale formation on the surface of an ion exchange membrane and perform stable acid recovery at low cost.

[0012] FIG. 1 is a schematic configuration diagram showing an example of an electrodialysis device according to an embodiment of the present invention. FIG. 2 is a schematic configuration diagram showing another example of an electrodialysis device according to an embodiment of the present invention. FIG. 3 is a schematic block diagram showing an example of a waste liquid treatment device for treating ion exchanger regeneration waste liquid according to an embodiment of the present invention. FIG. 4 is a schematic block diagram showing another example of a waste liquid treatment device for treating ion exchanger regeneration waste liquid according to an embodiment of the present invention. FIG. 5 is a schematic block diagram showing another example of a waste liquid treatment device for treating ion exchanger regeneration waste liquid according to an embodiment of the present invention. FIG. 6 is a diagram showing the relationship between conductivity and pH values ​​and operating time in waste liquid treatment of an example using the electrodialysis device shown in FIG. 2. FIG. 7 is a diagram showing the relationship between current value and operating time in waste liquid treatment of an example using the electrodialysis device shown in FIG.

[0013] According to an embodiment of the present invention, electrodialysis of an acidic solution using an electrodialysis device having a specific structure can prevent scale formation without the use of chemicals, reduce costs, and achieve stable acid recovery. The electrodialysis device according to this embodiment of the present invention includes at least an anode, a cathode, a first bipolar membrane, an anion exchange membrane, a cation exchange membrane, and a second bipolar membrane, in this order, and includes an anode chamber defined by the anode and the first bipolar membrane, an acid recovery chamber defined by the first bipolar membrane and the anion exchange membrane, a deionization chamber defined by the anion exchange membrane and the cation exchange membrane, a spent acid chamber defined by the cation exchange membrane and the second bipolar membrane, and a cathode chamber defined by the second bipolar membrane and the cathode. In this electrodialysis device, water is supplied to the acid recovery chamber, an acidic solution is supplied to the deionization chamber, and spent acid is supplied to the spent acid chamber to perform electrodialysis. The Na in the acidic solution supplied to the deionization chamber is then removed. ＋ Cationic components such as Cl move into the spent acid chamber. － is transferred to the acid recovery chamber, and at that time, H ＋As a result, HCl can be recovered from the acid recovery compartment. ２＋ , Mg ２＋ The hardness components in the waste acid are transferred to the waste acid chamber, and by controlling the pH of the waste acid (or adding or discharging the waste acid if the waste acid is recycled), scaling can be prevented without the addition of chemicals. Furthermore, efficient electrodialysis can be achieved by determining the endpoint of the electrodialysis process based on the pH and conductivity of the solution treated in each chamber and the current value of the electrodialysis device. If the values ​​stabilize after a certain amount of operating time, electrodialysis can be terminated at that stable state. Furthermore, waste acid solutions discharged from various factories can be used as the waste acid supplied to the waste acid chamber, allowing for the effective use of waste acid solutions that have been neutralized and then discharged. For example, acid solutions used in manufacturing processes in factories can be used. Specifically, waste sulfuric acid generated in the SPM (sulfuric acid-hydrogen peroxide mixture cleaning) cleaning process and the SOM (sulfuric acid and ozone mixture) cleaning process in semiconductor manufacturing can be used. Using such waste sulfuric acid eliminates the need to prepare new chemicals to combat scaling in the electrodialysis device, thereby reducing chemical costs and overall chemical usage.

[0014] Preferred embodiments of the present invention will be described below with reference to the drawings. However, the present invention is not limited to these embodiments and the configurations shown in the drawings. FIG. 1 shows an example of an electrodialysis apparatus according to one embodiment of the present invention. In FIG. 1, the electrodialysis apparatus 100 includes at least an anode 1, a cathode 17, a first bipolar membrane (hereinafter also referred to as "first BPM") 3, an anion exchange membrane (hereinafter also referred to as "AEM") 5, a cation exchange membrane (hereinafter also referred to as "CEM") 7, and a second bipolar membrane 9 (hereinafter also referred to as "second BPM"). Between the anode 1 and the cathode 17, the first BPM 3, the AEM 5, the CEM 7, and the second BPM 9 are arranged in this order from the anode 1 side. This configuration has an anode chamber 20 defined by the anode 1 and the first BPM 3, an acid recovery chamber 22 defined by the first BPM 3 and the AEM 5, a demineralization chamber 24 defined by the AEM 5 and the CEM 7, a spent acid chamber 26 defined by the CEM 7 and the second BPM 9, and a cathode chamber 34 defined by the second BPM 9 and the cathode 17.

[0015] The anode chamber 20 accommodates the anode 1 and is provided with an acid recovery chamber 22 adjacent to the anode chamber 20 via a first BPM 3. The cathode chamber 34 accommodates the cathode 17 and is provided with a spent acid chamber 26 adjacent to the cathode chamber 34 via a second BPM 9.

[0016] In the above configuration, the anode chamber 20 and the acid recovery chamber 22 are separated by the first BPM 3, and the acid recovery chamber 22 and the deionization chamber 24 are separated by the AEM 5. The deionization chamber 24 and the spent acid chamber 26 are separated by the CEM 7, and the spent acid chamber 26 and the cathode chamber 34 are separated by the second BPM 9. That is, the electrodialysis apparatus 100 shown in Figure 1 is a three-compartment electrodialysis apparatus in which the first BPM 3, the AEM 5, the CEM 7, and the second BPM 9 are arranged in this order from the anode 1 side, and which mainly consists of three chambers: the acid recovery chamber 22, the deionization chamber 24, and the spent acid chamber 26.

[0017] Here, the chambers constituting the electrodialysis apparatus 100 are arranged in the following order from the anode 1 side: anode - anode chamber - (acid recovery chamber - deionization chamber - spent acid chamber) n - cathode chamber - cathode. Here, the smallest repeating unit consisting of "acid recovery chamber - deionization chamber - spent acid chamber" in the parentheses is defined as the basic structure (i.e., cell set), and n (n is an integer of 1 or more) is the number of repeated cell sets. Note that FIG. 1 shows a structure where n = 1, and FIG. 2, described later, shows a structure where n = 2. The number of repeated cell sets can usually be set in the range of n = 1 to 500, and preferably in the range of 1 to 200.

[0018] The membranes constituting the electrodialysis device 100 are arranged in the following order from the anode side: anode-BPM (AEM-CEM-BPM) n-cathode. Here, n (n is an integer of 1 or more) is the number of repeated stacks of cell sets. Note that Figure 1 shows a configuration where n=1, and Figure 2 (described later) shows a configuration where n=2.

[0019] In the electrodialysis apparatus 100 according to the embodiment of the present invention shown in Figure 1, pure water is supplied to the acid recovery chamber 22, an acidic solution is supplied to the desalting chamber 24, and waste acid is supplied to the waste acid chamber 26, and electrodialysis treatment is performed. The pure water supplied to the acid recovery chamber 22 passes through the acid recovery chamber 22 and is discharged as recovered acid solution. The acidic solution supplied to the desalting chamber 24 passes through the desalting chamber 24 and is discharged as desalted water. The waste acid supplied to the waste acid chamber 26 passes through the waste acid chamber 26 and is discharged as treatment waste acid. The pure water supplied to the acid recovery chamber 22 may be high-purity water with few impurities enough to enable the desired electrodialysis, and water of a purity equal to or higher than that of water treated by a reverse osmosis membrane is preferred.

[0020] The bipolar membranes 3 and 9 are membranes in which a cation exchange membrane and an anion exchange membrane are integrated, and typically have a structure in which a cation exchange membrane and an anion exchange membrane are stacked. The bipolar membranes are configured so that the interface between the stacked cation exchange membrane and anion exchange membrane is optimized for the water dissociation reaction, facilitating the water dissociation reaction. For this purpose, a substance with a catalytic effect for water dissociation (e.g., heavy metal ions or tertiary amines) is generally introduced into the interface between the stacked separate ion exchange membranes. The bipolar membranes are arranged with the anion exchange membrane side facing the anode and the cation exchange membrane side facing the cathode.

[0021] The bipolar membranes 3 and 9 may be any membrane effective for water dissociation, and may not only be commercially available products, but may also be any membrane having a structure in which a cation exchange membrane and an anion exchange membrane are stacked.

[0022] The materials for the ion exchange membranes 5 and 7 used in the embodiment of the present invention are not particularly limited, and any known material may be used as long as it is effective for separating salts. Examples of such materials include a homogeneous membrane formed by coating a paste containing styrene and divinylbenzene with polyvinyl chloride, heating the coated paste, and then introducing exchange groups, and a heterogeneous membrane formed by molding an ion exchange resin powder with a suitable film-forming binder, such as polyethylene, polystyrene, phenolic resin, or synthetic rubber.

[0023] Electrodes used in the electrochemical industry, such as for water electrolysis, can be used for the anode 1 and the cathode 17, and such electrodes can be used without any restrictions. Examples of electrodes that can be used for the anode 1 and the cathode 17 include nickel electrodes, platinum-plated titanium electrodes, and stainless steel electrodes. The anode chamber and the cathode chamber are each filled with an electrode solution. Examples of the electrode solution include a sodium hydroxide solution, a sodium sulfate solution, and pure water.

[0024] Next, another example of an electrodialysis apparatus according to an embodiment of the present invention is shown in Fig. 2. In the electrodialysis apparatus 200 shown in Fig. 2, an anode 1, a cathode 17, a BPM 3 (corresponding to the first BPM in Fig. 1), an AEM 5 (corresponding to the AEM 5 in Fig. 1), a CEM 7 (corresponding to the CEM 7 in Fig. 1), a BPM 11 (corresponding to the second BPM 9 in Fig. 1), an AEM 13, a CEM 15, and a BPM 9 (corresponding to the second BPM 9 in Fig. 1) are arranged in this order from the anode 1 side. This configuration has an anode chamber 20 defined by the anode 1 and BPM 3, an acid recovery chamber 22 defined by the BPM 3 and AEM 5, a deionization chamber 24 defined by the AEM 5 and CEM 7, a spent acid chamber 26 defined by the CEM 7 and BPM 11, an acid recovery chamber 28 defined by the BPM 11 and AEM 13, a deionization chamber 30 defined by the AEM 13 and CEM 15, a spent acid chamber 32 defined by the CEM 15 and BPM 9, and a cathode chamber 34 defined by the BPM 9 and the cathode 17. Note that Figure 2 shows the configuration of cell set n=2 in Figure 1.

[0025] Pure water is supplied in parallel to each acid recovery chamber from a pure water tank (for example, a circulation line from the pure water tank to the acid recovery chamber 22 to the pure water tank, and a circulation line from the pure water tank to the acid recovery chamber 28 to the pure water tank). This pure water may be water of high purity with a low level of impurities to the extent that it can be electrodialyzed as desired, and water of a purity equal to or higher than that of water treated by a reverse osmosis membrane is preferred.

[0026] The acidic solution to be treated is supplied to each deionization chamber in parallel (for example, a circulation line from the regeneration waste liquid storage tank to the deionization chamber 24 to the regeneration waste liquid storage tank, and a circulation line from the regeneration waste liquid storage tank to the deionization chamber 30 to the regeneration waste liquid storage tank). A cation exchanger regeneration waste liquid may be supplied as the acidic solution. For example, the regeneration waste liquid obtained by regenerating a cation exchanger packed tower using hydrochloric acid contains NaCl, KCl, CaCl, etc., which are produced by the ion exchange reaction. ２ , MgCl ２ The acid for regenerating the cation exchanger is not limited to hydrochloric acid, and other strong acids (inorganic acids) such as sulfuric acid and nitric acid can also be used.

[0027] Waste acid is supplied in parallel to each waste acid chamber from a waste acid storage tank (e.g., a circulation line from the waste acid storage tank to the waste acid chamber 26 and then to the waste acid storage tank, and a circulation line from the waste acid storage tank to the waste acid chamber 32 and then to the waste acid storage tank). In this case, the pH of the solution in the waste acid chamber is preferably less than 2, more preferably 1 or less. Examples of waste acid include acid solutions used in factory manufacturing processes. Specifically, waste sulfuric acid generated in the SPM (sulfuric acid-hydrogen peroxide mixture cleaning) cleaning process and the SOM (sulfuric acid and ozone mixture) cleaning process in semiconductor manufacturing processes can be used. Using such waste sulfuric acid eliminates the need to prepare new chemicals to prevent scale buildup in the electrodialysis equipment, thereby reducing chemical costs and overall chemical usage. The sulfuric acid concentration of the waste sulfuric acid is preferably in the range of 1 to 20% by mass, more preferably 1 to 10% by mass. A sulfuric acid concentration of 1% by mass or higher effectively suppresses pH rise, while a sulfuric acid concentration of 20% by mass or lower prevents component deterioration. The hardness of the waste acid is preferably less than 1 ppm. This hardness is determined by dividing the total amount of calcium and magnesium by the amount of calcium carbonate (CaCO ３ ) is calculated as the pH of the spent acid in the spent acid chamber. The spent acid may be supplied in one pass or circulated. During electrodialysis operation, it is preferable to adjust the concentration of the spent acid or the amount of liquid passed through so that the pH of the spent acid in the spent acid chamber is less than 2 (preferably ≦pH 1) throughout the entire operation period. By keeping the pH of the spent acid in the spent acid chamber less than 2, it is possible to avoid the formation of scale during electrodialysis operation, prevent membrane damage, and ensure stable operation. When circulating the spent acid, it is preferable to add and discharge the spent acid intermittently. This not only makes it possible to keep the pH of the spent acid in the spent acid chamber less than 2, but also to discharge impurities (such as hardness components) accumulated in the spent acid to the outside of the system, thereby preventing an excessive increase in the impurity concentration.

[0028] The movement of ions during electrodialysis in the electrodialysis apparatus shown in Figure 1 will be described below. Although hydrochloric acid is used as an example of the acid for regenerating the cation exchanger, similar behavior will be observed even when an acid other than hydrochloric acid is used.

[0029] H is generated by a water dissociation reaction at the interface where the cation exchange membrane and the anion exchange membrane of the bipolar membrane (first and second BPM3, 9) are overlapped. ２ O is H ＋ and OH － In each electrode chamber, as shown in FIG. 1, the anode chamber 20 contains the OH dissociated by the first BPM 3. － is supplied to the cathode chamber 34, and H dissociated by the second BPM 9 is supplied to the cathode chamber 34. ＋ Therefore, when the same electrode solution is used in the anode chamber 20 and the cathode chamber 34, for example, by circulating the electrode solution between the anode chamber 20 and the cathode chamber 34, the supplied H ＋ and OH － can be balanced.

[0030] In the acid recovery chamber 22, as shown in FIG. 1, H dissociated from the first BPM 3 on the anode side is ＋ is supplied, and Cl is supplied from the desalination chamber 24. － As a result, H ＋ and Cl － combine to produce hydrochloric acid (HCl), which is discharged outside.

[0031] In the desalination compartment 24, as shown in FIG. － passes through the AEM 5 on the anode side and moves to the acid recovery chamber 22, and Na ＋ , K. ＋ , Ca ２＋ , Mg ２＋ The acidic solution is then passed through the CEM 7 on the cathode side and transferred to the waste acid chamber 26. As a result, demineralized water is produced from the acidic solution. The cation exchanger regeneration waste liquid (liquid to be treated) supplied as the acidic solution is electrodialyzed and then discharged outside the chamber as demineralized water.

[0032] In the waste acid chamber 26, as shown in FIG. ＋ , K. ＋ , Ca ２＋ , Mg ２＋ and the like pass through the CEM 7 on the anode side and move from the deionization chamber 24, － is supplied from the cathode side BPM 9. The supplied waste acid is subjected to electrodialysis and then discharged outside the chamber as treated waste acid.

[0033] Although not shown, a method can be suitably employed for the anode chamber 20 and the cathode chamber 34 by providing an electrode solution reservoir tank and circulating the electrode solution by a pump between the electrode solution reservoir tank, the anode chamber 20, and the cathode chamber 34. The electrode solution may be flowed to the anode chamber and the cathode chamber through parallel circulation lines (electrode chamber reservoir tank → anode chamber → electrode chamber reservoir tank, or electrode chamber reservoir tank → cathode chamber → electrode chamber reservoir tank), or through a single circulation line (electrode chamber reservoir tank → anode chamber → cathode chamber → electrode chamber reservoir tank, or electrode chamber reservoir tank → cathode chamber → anode chamber → electrode chamber reservoir tank).

[0034] 3 is a schematic block diagram showing an example of a wastewater treatment apparatus for treating ion exchanger regeneration wastewater according to an embodiment of the present invention. Pumps, valves, and the like are not shown. The various solutions (electrolyte, acid solution (ion exchanger regeneration wastewater), pure water, and waste acid) are supplied to the electrodialysis apparatus by pumping them through lines (flow paths) leading to the various chambers (anode chamber, acid recovery chamber, demineralization chamber, waste acid chamber, and cathode chamber).

[0035] In Fig. 3, a cation exchanger-packed column packed with a cation exchanger is installed downstream of an acid tank (regenerated liquid storage tank), which stores an acid used for regenerating the cation exchanger.

[0036] As shown in Figure 3, a regeneration waste liquid storage tank is installed downstream of the cation exchanger packed tower, and this regeneration waste liquid storage tank stores the acid solution passed through the cation exchanger packed tower to regenerate the cation exchanger as cation exchanger regeneration waste liquid. This cation exchanger regeneration waste liquid is preferably regeneration waste liquid from a cation exchanger used to produce pure water in semiconductor factories. Since the regeneration waste liquid from a cation exchanger used to produce pure water in semiconductor factories contains few organic components and has a low risk of organic contamination, suppressing scale can ensure stable operation of the electrodialysis apparatus.

[0037] As shown in FIG. 3, an electrodialysis device is installed in communication with a regeneration wastewater storage tank. The cation exchanger regeneration wastewater (acidic solution) supplied to this electrodialysis device is supplied to the desalting compartment of the electrodialysis device, as shown in FIG. 1 . The regeneration wastewater (desalinated water) treated in the desalting compartment of the electrodialysis device is returned to the regeneration wastewater storage tank for circulation. This circulation can be performed by a circulation device that supplies the regeneration wastewater (acidic solution) from the regeneration wastewater storage tank to the desalting compartment of the electrodialysis device and then circulates it from the desalting compartment back to the regeneration wastewater storage tank. The regeneration wastewater can be pumped. This circulation device can be configured to discharge the circulated regeneration wastewater (desalinated water) from the regeneration wastewater storage tank to the outside of the system when electrodialysis is terminated based on the endpoint determination described below. The desalinated water can be discharged to, for example, an existing wastewater recovery facility or wastewater treatment facility. Furthermore, this circulation device can be configured so that new regeneration waste liquid is supplied to the regeneration waste liquid storage tank after or simultaneously with the discharge of the recycled regeneration waste liquid (desalinated water) from the regeneration waste liquid storage tank, thereby replacing the recycled regeneration waste liquid. Furthermore, the circulation device may be configured so that a portion of the recycled regeneration waste liquid (a predetermined proportion or more) is discharged and new regeneration waste liquid is supplied to the regeneration waste liquid storage tank in the amount discharged. In other words, the circulation device may be configured so that a portion of the recycled regeneration waste liquid (a predetermined proportion or more) is replaced with new regeneration waste liquid. The discharge of the recycled regeneration waste liquid can be controlled by opening and closing a control valve provided in a discharge line connected to the regeneration waste liquid storage tank. The supply of new regeneration waste liquid to the regeneration waste liquid storage tank can be controlled by opening and closing a control valve provided in a supply line connected to the regeneration waste liquid storage tank.

[0038] As shown in FIG. 3 , a pure water tank is connected to the electrodialysis apparatus. This pure water tank stores pure water (high-purity water with few impurities, preferably water with a purity equal to or higher than that of reverse osmosis-treated water). As described above, as shown in FIG. 1 , pure water is supplied to the acid recovery chamber of the electrodialysis apparatus. The treated pure water (recovered acid solution) after passing through the electrodialysis apparatus is returned to the pure water tank and circulated. When electrodialysis is terminated based on the endpoint determination described below, the circulated pure water (recovered acid solution) is transferred from the pure water tank to the acid tank, and fresh pure water is supplied to the pure water tank in place of the transferred recovered acid solution. The acid solution in the acid tank may be not only the recovered acid solution transferred from the pure water tank, but also the acid solution from outside the system, which may be mixed with the recovered acid solution transferred from the pure water tank to adjust the concentration. Alternatively, the pure water tank and the acid tank may share a single tank. The acid concentration of the acid solution in the acid solution tank is not particularly limited, but in order to efficiently regenerate the ion exchanger, it is preferably 1 to 10% by mass, more preferably 1 to 5% by mass.

[0039] As shown in FIG. 3, a waste acid storage tank is arranged in communication with the electrodialysis apparatus. The waste acid (pH<2, preferably ≦pH1) is stored in the waste acid storage tank. The waste acid supplied to this electrodialysis apparatus is supplied to the waste acid chamber of the electrodialysis apparatus as shown in FIG. 1, as described above. The treated waste acid (treated waste acid) after passing through the electrodialysis apparatus is returned to the waste acid storage tank and recycled. During electrodialysis, the pH of the liquid in the waste acid storage tank is preferably monitored, and the recycled waste acid is preferably discharged from the system and new waste acid is added as needed to maintain the pH below 2 (preferably ≦pH1). (That is, it is preferable to replace a portion of the recycled waste acid with new waste acid.) When electrodialysis is terminated based on the endpoint determination described below, the recycled waste acid (treated waste acid) may be discharged from the waste acid storage tank to the system and replaced with new waste acid. The treated waste acid can be discharged, for example, to an existing wastewater treatment facility or wastewater recovery facility.

[0040] The amount of each liquid when circulating does not have to be the same, and any amount of water can be set depending on the required concentration of the recovered acid liquid obtained from the acid recovery chamber. For example, compared to circulating the same amount of pure water and regenerated waste liquid, if the amount of circulating pure water is reduced to be less than the amount of circulating regenerated waste liquid, a recovered acid liquid with a higher concentration can be obtained (conversely, if the amount of circulating pure water is increased to be more than the amount of circulating regenerated waste liquid, a recovered acid liquid with a lower concentration can be obtained). However, if the amount of waste acid is reduced, the amount of hardness component Ca ２＋ , Mg ２＋ Caution is required as this can lead to the concentration of

[0041] The electrodialysis apparatus may be operated intermittently for each regeneration treatment of the ion exchanger, or may be operated continuously by providing a regeneration wastewater storage tank, as shown in Figure 3. In the case of continuous operation, the timing of the end point of the electrodialysis treatment of the regeneration wastewater (start of discharge of treated regeneration wastewater) should be set to coincide with the timing of the next regeneration of the cation exchanger (start of supply of new regeneration wastewater). Compared to intermittent operation, continuous operation can be achieved by reducing the size of the electrodialysis apparatus and reducing the supply flow rate of the regeneration wastewater to adjust the timing. This allows for a smaller electrodialysis apparatus, shorter start-up time, and more stable treated water quality.

[0042] Methods for determining the timing of the end point of the electrodialysis treatment include operating the system for a preset time period, observing changes in the current flowing between the anode and cathode, observing changes in the conductivity of the pure water supplied to the acid recovery chamber or the regenerated waste liquid (demineralized water) treated in the demineralization chamber (possible when pure water or regenerated waste liquid is circulated), and observing changes in pH of the pure water (recovered acid liquid) treated in the acid recovery chamber or the regenerated waste liquid (demineralized water) treated in the demineralization chamber, or the waste acid (treated waste acid) treated in the waste acid chamber (possible when each solution is circulated).

[0043] When the operation is performed for a predetermined time, the time may be set arbitrarily, for example, so as to coincide with the regeneration of the ion exchanger.

[0044] In the method of determining the current value by observing the change, a current measuring device is connected in series with the electrodialysis apparatus and power supply, and the current value is transmitted to the control device at predetermined intervals. When electrodialysis begins, the current value gradually increases, then starts to decrease at a certain point, and then stabilizes at a relatively low value. Electrodialysis is terminated when the current value stabilizes at this relatively low value, i.e., when the current value has remained within a predetermined range for a predetermined time. Whether the current has remained within the predetermined range for a predetermined time can be determined, for example, by whether the slope of the change in the current value is within a predetermined range.

[0045] To determine conductivity by observing changes, a conductivity meter (conductivity measuring means) is installed at the outlet of each chamber, in the regeneration wastewater storage tank, or in the pure water tank, and values ​​are transmitted to the control device at predetermined intervals. Electrodialysis is terminated when the conductivity reaches a predetermined value (range) or when the change in conductivity is within a predetermined range. For example, the conductivity of pure water in the pure water tank gradually increases due to the generation of hydrochloric acid, as described above, and stabilizes at a high value after a certain period of time. Furthermore, the conductivity of the cation exchanger regeneration wastewater in the regeneration wastewater storage tank gradually decreases due to the migration of ions to the chamber adjacent to the deionization chamber, as described above, and stabilizes at a low value after a certain period of time.

[0046] To determine the pH by observing its change, a pH meter (pH measurement means) is installed at the outlet of each chamber, in the regeneration waste liquid storage tank, in the pure water tank, or in the waste acid storage tank, and the value is transmitted to the control device at predetermined intervals. Electrodialysis is terminated when the pH reaches a predetermined value (range) or when the change slope is within a predetermined range. For example, the pH of the pure water in the pure water tank gradually decreases from near neutral due to the generation of hydrochloric acid, as described above, and stabilizes at a low value after a certain period of time. Furthermore, the pH of the cation exchanger regeneration waste liquid in the regeneration waste liquid storage tank gradually increases from the acidic side due to the movement of ions to the chamber adjacent to the desalination chamber, as described above, and stabilizes at a neutral side from the initial value after a certain period of time. The waste acid in the waste acid storage tank gradually decreases due to the movement of ions from the adjacent desalination chamber and the release of OH from the bipolar membrane, as described above. － Due to the effect of the supply of HCl, the pH gradually rises from the acidic side.

[0047] Fig. 4 is a schematic block diagram showing another example of a wastewater treatment apparatus for treating ion exchanger regeneration wastewater according to an embodiment of the present invention. Pumps, valves, etc. are not shown. The apparatus shown in Fig. 4 has a configuration in which a nanofiltration membrane (NF) is disposed between the cation exchanger packed column and the regeneration wastewater storage tank of the apparatus shown in Fig. 3. With this configuration, the cation exchanger regeneration wastewater that has permeated the NF is supplied to the regeneration wastewater storage tank.

[0048] NF is Mg ２＋ and Ca ２＋ It does not allow divalent ions such as Cl － and Na ＋ This allows monovalent ions such as ions to pass through. This provides an additional effect of preventing the accumulation of hardness components and the formation of scale on the membrane surface in the downstream electrodialysis device.

[0049] Figure 5 is a schematic block diagram showing another example of a waste liquid treatment apparatus for treating ion exchanger regeneration waste liquid according to an embodiment of the present invention. Pumps, valves, and the like are not shown. In the apparatus shown in Figure 5, unlike the configuration of Figure 3, the demineralized water (treated regeneration waste liquid) discharged from the electrodialysis apparatus is directly discharged to the outside of the system without being circulated to the regeneration waste liquid storage tank. Also, unlike the configuration of Figure 3, the recovered acid solution discharged from the electrodialysis apparatus is directly transferred to the acid solution tank without being circulated to the pure water tank. Also, unlike the configuration of Figure 3, the treatment waste acid discharged from the electrodialysis apparatus is directly discharged to the outside of the system without being circulated to the waste acid storage tank.

[0050] By using the apparatus configuration shown in Figure 5, it is not necessary to replace the solutions in each tank at the end of electrodialysis, and the regenerated waste liquid is supplied for each regeneration treatment of the cation exchanger. Pure water and waste acid are supplied to the electrodialysis apparatus during electrodialysis operation in the same amounts as the discharged amounts of each solution. Furthermore, since there is no need to monitor the pH of the waste acid (< pH 2, preferably ≦ pH 1), the operation can be simplified. Furthermore, by making the supply flow rate and discharge flow rate of each solution the same, the pure water tank and the waste acid storage tank do not necessarily need to be installed.

[0051] 5 may be partially configured as shown in FIG. 3, for example, by circulating the recovered acid solution (treated pure water) and demineralized water (treated regenerated waste liquid) discharged from the electrodialysis apparatus, while discharging the waste acid directly without circulating it. Circulating the recovered acid solution (treated pure water) and demineralized water (treated regenerated waste liquid) is preferred because it allows for the miniaturization of the electrodialysis apparatus and ensures stable treated water quality.

[0052] When discharging the desalinated water (treated regenerated wastewater) without circulating it, the electrodialysis device can be operated intermittently for each ion exchanger regeneration treatment, or continuously, as in the case of circulating the desalinated water (treated regenerated wastewater). Continuous operation can be achieved by aligning the timing of the end point of the electrodialysis treatment with the timing of the ion exchanger regeneration (start of the supply of regenerated wastewater). Compared to intermittent operation, continuous operation can be achieved by downsizing the electrodialysis device and reducing the supply flow rate of the regenerated wastewater to adjust the timing. This allows for a smaller electrodialysis device, shorter start-up time, and more stable treated water quality.

[0053] 5 is changed to a configuration in which the recovered acid solution (treated pure water) is not circulated but is instead discharged, the timing of the end point of the electrodialysis treatment is the timing when the regenerated waste liquid runs out. When the configuration in FIG. 5 is changed to a configuration in which the recovered acid solution (treated pure water) is circulated to the pure water tank, the timing of the end point of the electrodialysis treatment can be determined not only by the timing when the regenerated waste liquid runs out but also by the conductivity, pH, operation time, and current value of the pure water tank.

[0054] In a modification of the configuration shown in FIG. 5 in which demineralized water (treated regenerated wastewater) is circulated and the recovered acid solution (treated pure water) is discharged directly without circulating, the timing of the end point of the electrodialysis treatment can be determined using the conductivity and pH of the regenerated wastewater storage tank, the operating time, and the current value.

[0055] By applying a wastewater recovery system equipped with an electrodialysis device according to an embodiment of the present invention to water treatment of acidic wastewater from pure water production, semiconductor manufacturing, etc., it is possible to prevent scale formation on the ion exchange membrane surface without adding chemicals for preventing scale, and stable acid recovery by the electrodialysis device can be performed at low cost. Furthermore, since scale formation on the ion exchange membrane surface can be prevented, damage to the membrane of the electrodialysis device can be prevented, enabling stable and efficient operation.

[0056] The present invention will be further described below with reference to examples, but the present invention is not limited to the following examples.

[0057] Example 1 In this example, electrodialysis treatment was carried out under the following conditions according to the embodiment of the present invention using the electrodialysis apparatus shown in Figure 2. In addition, a storage tank for the liquid supplied to each chamber was provided, and a circulation treatment was carried out. (Experimental conditions) Experimental equipment: Astom's bipolar membrane electrodialysis device (product name: Acilyzer EX3B) Water quality of feed liquid: See Table 1 Feed liquid to demineralization compartment: Regenerated waste liquid from a cation exchanger packed tower for producing pure water Feed liquid to spent acid compartment: Approximately 8% by mass sulfuric acid Feed liquid to acid recovery compartment: Pure water (water treated with reverse osmosis membrane) Electrode solution: 4% by mass NaOH Water temperature: 20 to 25°C (room temperature) Amount of feed liquid to demineralization compartment and circulation flow rate: 850 mL, 1.4 L / min Amount of feed liquid to spent acid compartment and circulation flow rate: 850 mL, 1.4 L / min Amount of feed liquid to acid recovery compartment and circulation flow rate: 850 mL, 1.4 L / min Voltage value: 10 V (constant) The pH in each supply solution tank was measured using a portable pH meter (product name: HM-40P) (glass electrode method) manufactured by DKK-TOA Corporation. The conductivity in each supply solution tank was measured using an electric conductivity meter (product name: AOL-10) manufactured by DKK-TOA Corporation. The ions in the solution were measured using an ion chromatograph (product name: Dionex Integration) (ion chromatography method) manufactured by Thermo Fisher Scientific K.K.

[0058] (Experimental Results) The transitions in conductivity and pH (changes in values ​​over time) of the regenerated waste liquid (demineralized water) supplied to the deionization compartment and treated, and the pure water (recovered acid liquid) supplied to the acid recovery compartment and treated are shown in Figure 6, and the transitions in current value of the electrodialysis device (changes in values ​​over time) are shown in Figure 7. The transitions in water quality of each feed liquid are shown in Table 1. As shown in Table 1, the NaCl in the deionization compartment was removed by electrodialysis. ＋ Cationic components such as Cl move into the waste acid chamber. － It can be seen that most of the Cl in the deionization compartment has been transferred to the acid recovery compartment. － It can be confirmed that the acid solution moves to the acid recovery chamber and HCl (recovered acid solution) is recovered from the acid recovery chamber.

[0059] 2 (Table 1), the conductivity of the pure water (recovered acid solution) treated in the acid recovery chamber increased and stabilized at a high value in about 90 minutes, and the pH started near neutral and became less than 1 after 40 minutes, as shown in Fig. 6. The conductivity of the regenerated waste water (demineralized water) treated in the demineralization chamber decreased and stabilized at a low value in about 90 minutes, and the pH started near 1 and stabilized at about 3.5 in about 100 minutes.

[0060] As shown in Figure 7, the value of the current flowing between the anode and cathode of the electrodialysis device rose significantly around 10 minutes after the start of electrodialysis, then began to decline around 30 minutes, and then stabilized at a low value around 110 minutes.

[0061] As described above, in this example, the electrical conductivity of the solution in the deionization compartment and the acid recovery compartment was stable approximately 110 minutes after the start of electrodialysis, and the current flowing between the anode and cathode of the electrodialysis device was stable at a low value. Furthermore, no decrease in current due to scale formation was observed during electrodialysis, and no scale material was visible on the ion exchange membrane surface after electrodialysis. From the above, it can be seen that the present invention can prevent scale formation and enable stable acid recovery from regenerated wastewater at low cost.

[0062]

[0063] (Reference Example 1) Electrodialysis was carried out in the same manner as in Example 1, except that sulfuric acid adjusted to pH 3 was supplied as the feed solution to the waste acid chamber. Compared to Example 1, a decrease in the current value was confirmed (the current peaked at less than 2 A, remained low overall, and finally reached almost 0 A in about 80 minutes). In addition, a deterioration in the quality of the treated water (Cl in the acid recovery chamber after 120 minutes from the start of electrodialysis) was confirmed. － Furthermore, when the inside of the electrodialysis device was checked 120 minutes after the start of electrodialysis, white scale was observed on the surface of the cation exchange membrane. This was due to Ca(OH) ２ and Mg(OH) ２ It is thought that components such as these precipitated.

[0064] 1 anode 3 first bipolar membrane (BPM) 5 first anion exchange membrane (AEM) 7 first cation exchange membrane (CEM) 9 second bipolar membrane (BPM) 11 second bipolar membrane (BPM) 13 second anion exchange membrane (AEM) 15 second cation exchange membrane (CEM) 17 cathode 20 anode chamber 22 first acid recovery chamber 24 first deionization chamber 26 first spent acid chamber 28 second acid recovery chamber 30 second deionization chamber 32 second spent acid chamber 34 cathode chamber

Claims

1. An electrodialysis apparatus comprising at least an anode, a cathode, a first bipolar membrane, an anion exchange membrane, a cation exchange membrane, and a second bipolar membrane, the first bipolar membrane, the anion exchange membrane, the cation exchange membrane, and the second bipolar membrane being arranged in this order from the anode side between the anode and the cathode, the apparatus comprising an anode chamber defined by the anode and the first bipolar membrane, an acid recovery chamber defined by the first bipolar membrane and the anion exchange membrane, a desalting chamber defined by the anion exchange membrane and the cation exchange membrane, a spent acid chamber defined by the cation exchange membrane and the second bipolar membrane, and a cathode chamber defined by the second bipolar membrane and the cathode, wherein water is supplied to the acid recovery chamber, an acidic solution is supplied to the desalting chamber, and spent acid is supplied to the spent acid chamber to perform electrodialysis treatment.

2. The electrodialysis apparatus according to claim 1, wherein the waste acid is waste acid discharged from a semiconductor factory.

3. The electrodialysis apparatus according to claim 1 or 2, wherein the acidic solution is a regeneration waste liquid of a cation exchanger.

4. The electrodialysis apparatus according to claim 1 or 2, wherein the waste acid is an aqueous sulfuric acid solution, and the sulfuric acid concentration of the waste acid is in the range of 1 to 20 mass %.

5. The electrodialysis apparatus according to claim 1 or 2, further comprising a pH measuring means for measuring a pH of said waste acid, wherein the pH of said waste acid measured by said pH measuring means is less than 2 during the entire electrodialysis period.

6. An electrodialysis apparatus according to claim 1 or 2, comprising: an acid solution storage tank for storing the acid solution to be supplied to the desalting compartment; an acid solution circulation path for circulating the treated acid solution discharged from the desalting compartment back to the acid solution storage tank; an acid solution circulating device for circulating the acid solution through the acid solution storage tank and the acid solution circulation path; at least one of a current measuring device for measuring a current value between the anode and the cathode during electrodialysis treatment, a conductivity measuring means for measuring the conductivity of the water or the acid solution, and a pH measuring means for measuring the pH of the water or the acid solution; and a control device for controlling the operation of the acid solution circulating device and receiving values ​​measured by at least one of the current measuring device, the conductivity measuring means, and the pH measuring means, wherein the control device circulates the acid solution using the acid solution circulating device during electrodialysis treatment, and when at least one value selected from a slope of the current value, the current, the conductivity, and the pH falls within a predetermined range, replaces the circulating acid solution with the acid solution outside the circulation system or discharges it out of the circulation system at a predetermined ratio or more.

7. The electrodialysis apparatus according to claim 1 or 2, further comprising: a nanofiltration device for separating the acidic solution into a permeate and a concentrate using a nanofiltration membrane; and a line for supplying the permeate to the desalting compartment.

8. An electrodialysis method for treating an acidic solution containing hardness components, comprising: an electrodialysis apparatus having at least an anode, a cathode, a first bipolar membrane, an anion exchange membrane, a cation exchange membrane, and a second bipolar membrane, the first bipolar membrane, the anion exchange membrane, the cation exchange membrane, and the second bipolar membrane being arranged in this order from the anode side between the anode and the cathode; an anode chamber defined by the anode and the first bipolar membrane; an acid recovery chamber defined by the first bipolar membrane and the anion exchange membrane; a desalting chamber defined by the anion exchange membrane and the cation exchange membrane; a waste acid chamber defined by the cation exchange membrane and the second bipolar membrane; and a cathode chamber defined by the second bipolar membrane and the cathode; A method for electrodialysis comprising supplying waste acid to the waste acid chamber and carrying out electrodialysis.

9. A cation exchange device filled with a cation exchanger; a regenerated liquid storage tank for storing a regenerated liquid of the cation exchanger; and an electrodialysis device for treating regenerated waste liquid discharged from the cation exchange device to which the regenerated liquid has been supplied, the electrodialysis device having at least an anode, a cathode, a first bipolar membrane, an anion exchange membrane, a cation exchange membrane, and a second bipolar membrane, the first bipolar membrane, the anion exchange membrane, the cation exchange membrane, and the second bipolar membrane being disposed in this order from the anode side between the anode and the cathode, the electrodialysis device comprising an anode chamber defined by the anode and the first bipolar membrane, an acid recovery chamber defined by the first bipolar membrane and the anion exchange membrane, a desalting chamber defined by the anion exchange membrane and the cation exchange membrane, and a waste acid chamber defined by the cation exchange membrane and the second bipolar membrane. a cathode chamber defined by the second bipolar membrane and the cathode; a means for supplying water to the acid recovery chamber; a means for supplying an acid solution to the deionization chamber; and a means for supplying waste acid to the waste acid chamber.

10. A method for electrodialysis comprising the steps of: supplying a regenerated liquid of a cation exchanger to a cation exchange device filled with a cation exchanger; and subjecting a regenerated waste liquid discharged from the cation exchange device to electrodialysis, the electrodialysis step comprising: a system including: an anode, a cathode, a first bipolar membrane, an anion exchange membrane, a cation exchange membrane, and a second bipolar membrane, the first bipolar membrane, the anion exchange membrane, the cation exchange membrane, and the second bipolar membrane being disposed in this order from the anode side between the anode and the cathode; an anode chamber defined by the anode and the first bipolar membrane; an acid recovery chamber defined by the first bipolar membrane and the anion exchange membrane; a desalting chamber defined by the anion exchange membrane and the cation exchange membrane; a waste acid chamber defined by the cation exchange membrane and the second bipolar membrane; A waste liquid treatment method comprising the steps of: supplying water to the acid recovery chamber; supplying the regenerated waste liquid to the deionization chamber; and supplying waste acid to the waste acid chamber, and performing electrodialysis treatment using an electrodialysis apparatus having a cathode chamber defined by the second bipolar membrane and the cathode.

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