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

Abstract

The present invention provides an electrodialysis device capable of preventing the formation of scale on an ion exchange membrane surface and performing stable acid recovery at low cost, 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 in this order, 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, and in which water is supplied to the acid recovery chamber, an acidic solution is supplied to the desalting chamber, and waste acid is supplied to the waste acid chamber to perform electrodialysis treatment.

Description

[Technical field]

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

[0002] Conventionally, ion exchangers have been used for various purposes, for example, in pure water production systems. In general, pure water production systems have 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 cationic components in the water to be treated in the cation exchanger-packed device, remove carbon dioxide gas in the decarbonation device, and remove anionic 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, so that it becomes necessary to regenerate the saturated ion exchangers. In order to completely regenerate a saturated ion exchanger, it is necessary to use a large amount of acid solution or alkaline solution as a regenerating solution. In addition, the acid solution or alkaline solution used for regeneration is treated as waste liquid (regeneration waste liquid) and is subjected to neutralization or other treatment. Since a large amount of acid or alkali is used in the neutralization treatment of this waste liquid, there are problems such as a large amount of chemicals being used and an increase in the salt concentration in the waste liquid. Therefore, from the viewpoints of reducing the amount of chemicals used and the processing costs, as well as reducing the environmental load, there is a demand for the recovery of waste liquid (regeneration waste liquid).

[0004] In the recovery of the above-mentioned regenerated 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.) in the high-concentration waste acid and waste alkaline solution. One method for removing ions is electrodialysis, and a method has been proposed in which regenerated wastewater is treated by electrodialysis to recover acid and alkali.

[0005] For example, Patent Document 1 describes a treatment method in which regeneration wastewater generated in a process of 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. The treatment method describes the addition of a membrane fouling inhibitor to the regeneration wastewater, which has a calcium precipitation suppression effect and prevents calcium from adhering to membranes and causing scaling. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 11-566 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the method described in Patent Document 1 requires the addition of an anti-membrane fouling agent to the regeneration wastewater, which increases the amount of chemicals used and increases costs. Meanwhile, various factories, particularly semiconductor factories, discharge large amounts of waste acid liquid used in cleaning processes such as SPM cleaning (sulfuric acid-hydrogen peroxide mixture cleaning). In many cases, this waste acid liquid is neutralized, treated, and then discharged, and there is a demand for finding other uses for this waste acid liquid.

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

[0009] As a result of intensive 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] A catalytic converter 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 are 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 compartment 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; a cathode chamber defined by the second bipolar membrane and the cathode; An electrodialysis apparatus in which water is supplied to the acid recovery chamber, an acidic solution is supplied to the deionization chamber, and waste acid is supplied to the waste acid chamber to perform electrodialysis treatment. [2] The electrodialysis apparatus according to [1], wherein the waste acid is waste acid discharged from a semiconductor factory. [3] The electrodialysis apparatus according to [1] or [2], wherein the acidic solution is a regeneration wastewater 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] Having a pH measuring means for measuring the pH of the waste acid, The electrodialysis apparatus according to [1] or [2], wherein the pH of the waste acid measured by the pH measuring means is less than 2 throughout the entire electrodialysis period. [6] An acidic solution storage tank for storing the acidic 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 that circulates 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 acidic solution, and a pH measuring means for measuring the pH of the water or the acidic solution; a control device that controls the operation of the acid solution circulating device and receives values ​​measured by at least one of the current measuring device, the conductivity measuring means, and the pH measuring means; The electrodialysis apparatus according to [1] or [2], wherein the control device circulates the acidic solution using the acidic solution circulation device during electrodialysis treatment, and when at least one value selected from a slope of a current value, a current, a conductivity, and a pH falls within a predetermined range, the control device replaces the circulating acidic solution with the acidic solution outside the circulation system or discharges the circulating acidic solution outside the circulation system at a predetermined ratio or more. [7] A nanofiltration device that separates the acidic solution into a permeate and a concentrate using a nanofiltration membrane; The electrodialysis apparatus according to [1] or [2], further comprising a line for supplying the permeate to the desalting compartment. [8] An electrodialysis method for treating an acidic solution containing hardness components, comprising: The catalytic converter 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 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 compartment 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; Using an electrodialysis apparatus having a cathode chamber defined by the second bipolar membrane and the cathode, Supplying water to the acid recovery chamber; Supplying the acidic solution to the desalting compartment; A method for electrodialysis comprising supplying waste acid to the waste acid chamber and carrying out electrodialysis. [9] A cation exchange device packed with a cation exchanger; a regenerated liquid storage tank for storing a regenerated liquid of the cation exchanger; and an electrodialysis device for treating a regenerated waste liquid discharged from the cation exchange device to which the regenerated liquid has been supplied, 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 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 compartment 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; 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 acidic solution to the desalting compartment; A means for supplying waste acid to the waste acid chamber; A waste liquid treatment device comprising:

[10] A step of supplying a regenerating liquid for the cation exchanger to a cation exchange device packed with the cation exchanger; and subjecting the regenerated wastewater discharged from the cation exchange device to electrodialysis treatment. The electrodialysis treatment step includes: The catalytic converter 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 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 compartment 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; Using an electrodialysis apparatus having a cathode chamber defined by the second bipolar membrane and the cathode, Supplying water to the acid recovery chamber; Supplying the regeneration waste liquid to the desalting chamber; A waste liquid treatment method comprising supplying waste acid to the waste acid chamber and subjecting it to electrodialysis treatment. Effect of the Invention

[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 the formation of scale on the surface of an ion exchange membrane and perform stable acid recovery at low cost. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic configuration diagram showing an example of an electrodialysis device according to an embodiment of the present invention. [Diagram 2] FIG. 4 is a schematic configuration diagram showing another example of an electrodialysis device according to an embodiment of the present invention. [Diagram 3] FIG. 1 is a schematic block diagram showing an example of a waste liquid treatment apparatus for treating ion exchanger regeneration waste liquid according to an embodiment of the present invention. [Figure 4] FIG. 2 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. [Diagram 5] FIG. 2 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. [Figure 6] FIG. 3 is a graph showing the relationship between the electrical conductivity and pH value and the operation time in the waste liquid treatment of an example using the electrodialysis apparatus shown in FIG. 2. [Figure 7] FIG. 3 is a diagram showing the relationship between the current value and the operation time in the waste liquid treatment of an example using the electrodialysis apparatus shown in FIG. 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] According to an embodiment of the present invention, by performing electrodialysis of an acidic solution using an electrodialysis device having a specific structure, it is possible to prevent scale formation without using chemicals, reduce costs, and perform stable acid recovery. The electrodialysis device according to an embodiment of the present invention has 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 has 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. In such an electrodialysis device, water is supplied to the acid recovery chamber, an acidic solution is supplied to the desalting chamber, and waste acid is supplied to the waste acid chamber to perform electrodialysis. Na in the acidic solution supplied to the desalting chamber + Cationic components such as Cl move into the waste acid chamber. - is transferred to the acid recovery chamber, where H + As a result, HCl can be recovered from the acid recovery chamber. In addition, the Ca in the acidic solution supplied to the desalting chamber 2+ ,Mg 2+ The hardness components move to the waste acid chamber, and by controlling the pH of the waste acid (by adding or discharging the waste acid if it is circulated), the formation of scale can be prevented without adding chemicals. In addition, efficient electrodialysis can be performed by determining the timing of the end point of the electrodialysis process based on the pH and conductivity of the liquid treated in each chamber and the current value of the electrodialysis device. If the values ​​stabilize after a certain amount of operation time of the electrodialysis device, the electrodialysis can be terminated at that stable state. In addition, the waste acid supplied to the waste acid chamber can be waste acid discharged from various factories, and waste acid discharged after neutralization can be effectively utilized. For example, acid solutions used in the manufacturing process of a factory can be used, specifically waste sulfuric acid generated in the SPM (sulfuric acid-hydrogen peroxide mixture cleaning) cleaning process and SOM (sulfuric acid and ozone mixture) cleaning process in the semiconductor manufacturing process. By using such waste sulfuric acid, there is no need to prepare new chemicals to prevent scale buildup in the electrodialysis device, and chemical costs and the overall amount of chemicals used can be reduced.

[0014] Preferred embodiments of the present invention will now be described with reference to the drawings, but the present invention is not limited to these embodiments and the configurations shown in the drawings. FIG 1 shows an example of an electrodialysis device according to an embodiment of the present invention. In FIG 1, the electrodialysis device 100 has 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 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 desalting 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 contains the anode 1 and is provided with an acid recovery chamber 22 adjacent to the anode chamber 20 via the first BPM 3. The cathode chamber 34 contains the cathode 17 and is provided with a waste acid chamber 26 adjacent to the cathode chamber 34 via the 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 Fig. 1 is a three-chamber type 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 device 100 are arranged in the order from the anode 1 side as follows: anode-anode chamber-(acid recovery chamber-demineralization chamber-spent acid chamber)n-cathode chamber-cathode. Here, the minimum repeating unit consisting of "acid recovery chamber-demineralization chamber-spent acid chamber" in the parentheses is taken as the basic structure (i.e., cell set), and n (n is an integer of 1 or more) is the number of repeated stacks of cell sets. Note that in Fig. 1, n=1, and in Fig. 2 described later, n=2. The number of repeated stacking of cell sets, n, can usually be set in the range of 1-500, and is preferably in the range of 1-200.

[0018] The membranes constituting the electrodialysis device 100 are arranged in the order from the anode side as follows: anode-BPM (AEM-CEM-BPM) n-cathode. Here again, n (n is an integer of 1 or more) is the number of repeated stacks of cell sets. Note that in Fig. 1, n=1, and in Fig. 2, which will be described later, n=2.

[0019] In an electrodialysis apparatus 100 according to an embodiment of the present invention shown in Fig. 1, pure water is supplied to the acid recovery chamber 22, an acid 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 liquid. The acid 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 treated waste acid. The pure water supplied to the acid recovery chamber 22 may be high-purity water with few impurities to the extent that the desired electrodialysis can be performed, and water having a purity equal to or higher than that of reverse osmosis membrane treated water is preferable.

[0020] 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. In addition, the bipolar membrane has a structure in which the interface between the stacked cation exchange membrane and anion exchange membrane is optimized for the water dissociation reaction, and is configured so that the water dissociation reaction can easily proceed. For this purpose, a substance having 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. In addition, the bipolar membrane is arranged with the anion exchange membrane side facing the anode side and the cation exchange membrane side facing the cathode side.

[0021] Moreover, 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 laminated.

[0022] The material of the ion exchange membranes 5 and 7 used in the embodiment of the present invention is not particularly limited, and any known material may be used as appropriate, provided that a membrane effective for separating salts is selected. For example, a homogeneous membrane is formed by coating a paste containing styrene and divinylbenzene with polyvinyl chloride, heating the paste, and then introducing an exchange group thereinto, or a heterogeneous membrane is 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 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, such as a sodium hydroxide solution, a sodium sulfate solution, or pure water.

[0024] Next, another example of an electrodialysis device according to an embodiment of the present invention is shown in Fig. 2. In the electrodialysis device 200 shown in Fig. 2, an anode 1, a cathode 17, a BPM3 (corresponding to the first BPM in Fig. 1), an AEM5 (corresponding to the AEM5 in Fig. 1), a CEM7 (corresponding to the CEM7 in Fig. 1), a BPM11 (corresponding to the second BPM9 in Fig. 1), an AEM13, a CEM15, and a BPM9 (corresponding to the second BPM9 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 BPM3, an acid recovery chamber 22 defined by the BPM3 and AEM5, a deionization chamber 24 defined by the AEM5 and CEM7, a spent acid chamber 26 defined by the CEM7 and BPM11, an acid recovery chamber 28 defined by the BPM11 and AEM13, a deionization chamber 30 defined by the AEM13 and CEM15, a spent acid chamber 32 defined by the CEM15 and BPM9, and a cathode chamber 34 defined by the BPM9 and the cathode 17. Note that FIG. 2 shows the configuration of cell set n=2 in FIG. 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 small number of impurities to the extent that the desired electrodialysis can be performed, and water of a purity equal to or higher than that of reverse osmosis membrane treated water is preferable.

[0026] An acidic solution to be treated is supplied in parallel to each deionization chamber (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 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 from a waste acid storage tank to each waste acid chamber (for example, a circulation line from the waste acid storage tank to the waste acid chamber 26 to the waste acid storage tank, and a circulation line from the waste acid storage tank to the waste acid chamber 32 to the waste acid storage tank). In this case, it is preferable that the pH of the solution in the waste acid chamber is less than 2, and more preferably 1 or less. For example, an acid solution used in a manufacturing process in a factory can be used as the waste acid. 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 the semiconductor manufacturing process can be used. By using such waste sulfuric acid, it is no longer necessary to prepare new chemicals for anti-scaling measures in the electrodialysis device, and the cost of chemicals and the total amount of chemicals used can be reduced. The sulfuric acid concentration of the waste sulfuric acid is preferably in the range of 1 to 20% by mass, more preferably in the range of 1 to 10% by mass. By making the sulfuric acid concentration 1% by mass or more, an increase in pH can be effectively suppressed, and by making it 20% by mass or less, deterioration of components can be prevented. 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 ) The waste acid may be supplied in a single pass or in a circulated manner. During the electrodialysis operation, it is preferable to adjust the waste acid concentration or the amount of liquid passed so that the pH of the waste acid in the waste acid chamber is less than 2 (preferably ≦pH1) throughout the entire operation period. By keeping the pH of the waste acid in the waste acid chamber less than 2, it is possible to avoid the formation of scale during the electrodialysis operation, prevent the membrane from being damaged, and enable stable operation. In addition, when circulating the waste acid, it is preferable to intermittently add and discharge the waste acid. This not only makes it possible to keep the pH of the waste acid in the waste acid chamber less than 2, but also makes it possible to discharge impurities (such as hardness components) accumulated in the waste acid to the outside of the system, thereby preventing an excessive increase in the impurity concentration.

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

[0029] H is generated by a water dissociation reaction at the interface between the cation exchange membrane and the anion exchange membrane of the bipolar membrane (first and second BPM3, 9). 2 O is H + and OH - As shown in FIG. 1, in the anode chamber 20, the first BPM3 dissociated OH - is supplied to the cathode chamber 34, and H dissociated by the second BPM 9 is supplied to the cathode chamber 35. + Therefore, when the same electrode solution is used in the anode chamber 20 and the cathode chamber 34, for example, the electrode solution is circulated between the anode chamber 20 and the cathode chamber 34 to reduce the amount of 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 removed from desalination chamber 24. - moves through the AEM5. As a result, H + and Cl - These combine to produce hydrochloric acid (HCl), which is discharged outside.

[0031] In the desalting chamber 24, as shown in FIG. - permeates through the AEM5 on the anode side and moves to the acid recovery chamber 22, and Na + , K + , Ca 2+ , Mg 2+ etc. permeate the CEM 7 on the cathode side and move to the waste acid chamber 26. As a result, desalted water is produced from the acidic solution. The cation exchanger regeneration waste liquid (liquid to be treated) supplied as the acidic solution in this way is discharged outside the chamber as desalted water after electrodialysis.

[0032] In the waste acid chamber 26, as shown in FIG. + , K +, Ca 2+ , Mg 2+ These pass through the anode side CEM7 and move from the desalting chamber 24, and OH - is supplied from the cathode side BPM 9. The supplied waste acid is electrodialyzed and then discharged outside the chamber as treated waste acid.

[0033] Although not shown in the drawings, a method can be suitably employed for the anode chamber 20 and the cathode chamber 34, in which an electrode solution reservoir tank is provided and the electrode solution is circulated by a pump between the electrode solution reservoir tank and the anode chamber 20 and 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 waste liquid treatment apparatus for treating ion exchanger regeneration waste liquid according to an embodiment of the present invention, pumps, valves, etc. are not shown. The various liquids (electrolyte, acid solution (ion exchanger regeneration waste liquid), pure water, and waste acid) can be supplied to the electrodialysis device by pumping them through the lines (flow paths) leading to each chamber (anode chamber, acid recovery chamber, desalting chamber, waste acid chamber, and cathode chamber).

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

[0036] As shown in FIG. 3, a regeneration waste liquid storage tank is installed downstream of the cation exchanger packed tower, and the acid solution passed through the cation exchanger packed tower for regenerating the cation exchanger is stored in this regeneration waste liquid storage tank as a cation exchanger regeneration waste liquid. The cation exchanger regenerated waste liquid is preferably a cation exchanger regenerated waste liquid used for producing pure water in semiconductor factories. The cation exchanger regenerated waste liquid used for producing pure water in semiconductor factories contains few organic components and has a low risk of organic contamination, so that the electrodialysis device can be operated stably by suppressing scale formation.

[0037] As shown in Figure 3, an electrodialysis device is installed in communication with a regeneration waste liquid storage tank. The cation exchanger regeneration waste liquid (acidic solution) supplied to this electrodialysis device is supplied to the desalting compartment of the electrodialysis device as shown in the above-mentioned Figure 1. The regeneration waste liquid (desalted water) treated in the desalting compartment of the electrodialysis device is returned to the regeneration waste liquid storage tank again and is circulated. Such a circulation treatment can be performed by a circulation device that supplies the regenerated waste liquid (acidic solution) from a regenerated waste liquid storage tank to a desalting compartment of the electrodialysis device, and then circulates it from the desalting compartment back to the regenerated waste liquid storage tank. The regenerated waste liquid can be sent by a pump. This circulation device can be configured to discharge the regenerated waste liquid (desalted water) that has been circulated from the regenerated waste liquid storage tank to the outside of the system when the electrodialysis is terminated by the endpoint determination described below. The desalted water can be discharged to, for example, an existing wastewater recovery facility or wastewater treatment facility. In addition, this circulation device can be configured to supply new regenerated waste liquid to the regenerated waste liquid storage tank after or at the same time that the regenerated waste liquid (desalted water) that has been circulated is discharged from the regenerated waste liquid storage tank, thereby replacing the regenerated waste liquid. In addition, the circulation device may be configured to discharge a part of the regenerated waste liquid that has been circulated (a predetermined ratio or more) and supply new regenerated waste liquid to the regenerated waste liquid storage tank by the amount of the discharged part. In other words, the circulation device may be configured to replace a part of the regenerated waste liquid that has been circulated (a predetermined ratio or more) with new regenerated waste liquid. The discharge of the recycled waste liquid can be controlled by opening and closing a control valve provided in a discharge line connected to the regenerated waste liquid storage tank. The supply of new regenerated waste liquid to the regenerated waste liquid storage tank can be controlled by opening and closing a control valve provided in a supply line connected to the regenerated waste liquid storage tank.

[0038] As shown in Fig. 3, a pure water tank is arranged in communication with the electrodialysis device. This pure water tank stores pure water (any water with high purity and few impurities is acceptable, and water with a purity higher than that of reverse osmosis membrane treated water is preferred). As shown in Fig. 1 as described above, the pure water is supplied to the acid recovery chamber of the electrodialysis device. The treated pure water (recovered acid solution) after passing through the electrodialysis device is returned to the pure water tank again and subjected to circulation treatment. When the electrodialysis ends according to the end point determination described later, the circulated treated pure water (recovered acid solution) is transferred from the pure water tank to the acid solution tank, and fresh pure water is supplied to the pure water tank instead of the transferred recovered acid solution. The acid solution in the acid solution tank may be adjusted in concentration by supplementing acid solution from outside the system as needed and mixing it with the recovered acid solution transferred from the pure water tank, in addition to the recovered acid solution transferred from the pure water tank, or the pure water tank and the acid solution tank may share one tank. The acid concentration of the acid solution in the acid solution tank is not particularly limited, but for efficient regeneration of the ion exchanger, 1 to 10% by mass is preferred, and 1 to 5% by mass is more preferred.

[0039] As shown in Fig. 3, a waste acid storage tank is arranged in communication with the electrodialysis device. The waste acid storage tank stores waste acid (<pH 2, preferably ≤pH 1). The waste acid supplied to this electrodialysis device is supplied to the waste acid chamber of the electrodialysis device as shown in Fig. 1 as described above. The treated waste acid (treated waste acid) after passing through the electrodialysis device is returned to the waste acid storage tank again and subjected to circulation treatment. During the electrodialysis process, it is preferable to monitor the pH of the liquid in the waste acid storage tank and appropriately discharge the circulated treated waste acid out of the system and add new waste acid so that the pH is less than 2 (preferably ≤pH 1) (that is, it is preferable to replace a part of the circulated treated waste acid with new waste acid). When the electrodialysis ends according to the end point determination described later, the circulated treated waste acid (treated waste acid) may be discharged from the waste acid storage tank out of the system and replaced with new waste acid. As the discharge destination of the treated waste acid, for example, it can be merged into existing wastewater treatment facilities or wastewater recovery facilities.

[0040] The amount of each liquid circulated does not have to be the same, and any amount of water can be set according to 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 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 more than the amount of circulating regenerated waste liquid, a recovered acid liquid with a lower concentration can be obtained). However, reducing the amount of waste acid will result in a higher concentration of the hardness component Ca. 2+ ,Mg 2+ Caution is required as this can result in the concentration of

[0041] The electrodialysis device may be operated intermittently for each regeneration treatment of the ion exchanger, or may be operated continuously by providing a regeneration waste liquid storage tank as shown in Figure 3. When operating continuously, the timing of the end point of the electrodialysis treatment of the regeneration waste liquid (start of discharge of treated regeneration waste liquid) should be made to overlap with the timing of the next regeneration of the cation exchanger (start of supply of new regeneration waste liquid). Compared to intermittent operation, continuous operation can be achieved by making the electrodialysis device smaller and reducing the supply flow rate of the regeneration waste liquid to adjust the timing. This makes it possible to reduce the size of the electrodialysis device, shorten the start-up time, and stabilize the quality of the treated water.

[0042] Methods for determining the timing of the end point of the electrodialysis treatment include operating it for a preset period of time, observing and determining the change in the current value flowing between the anode and cathode, observing and determining the change in conductivity of the pure water supplied to the acid recovery chamber or the regenerated waste liquid (demineralized water) treated in the desalting chamber (possible when pure water or regenerated waste liquid is circulated), and observing and determining the change 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 desalting 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 preset time, the time can be set arbitrarily, for example, so as to coincide with the regeneration of the ion exchanger.

[0044] In the method of observing and determining the change in the current value, a current measuring device is connected in series with the electrodialysis device and the power supply device, and the current value is transmitted to the control device at a predetermined cycle. When the electrodialysis is started, the current value gradually increases, then starts to decrease at a certain point, and then stabilizes at a relatively low value. The electrodialysis is terminated when the current value reaches a relatively low and stable state, i.e., when the current value has continued within a predetermined range for a predetermined period of time. Whether or not the current value has continued within the predetermined range for a predetermined period of time can be determined, for example, by whether or not the slope of the change in the current value is within a predetermined range.

[0045] In the method of observing and determining the change in conductivity, a conductivity meter (conductivity measuring means) is installed at the outlet of each chamber, in the regeneration waste liquid storage tank, or in the pure water tank, and values ​​are transmitted to the control device at a predetermined cycle. Electrodialysis is terminated when the conductivity reaches a predetermined value (range) or when the gradient of the change is within a predetermined range. For example, the tendency of the change in conductivity is that the conductivity of the pure water in the pure water tank gradually increases due to the effect of hydrochloric acid generation as described above, and stabilizes at a high value after a certain amount of time has passed. Also, the conductivity of the cation exchanger regeneration waste liquid in the regeneration waste liquid storage tank gradually decreases due to the effect of ions moving to the chamber adjacent to the desalting chamber as described above, and stabilizes at a low value after a certain amount of time has passed.

[0046] In the method of observing and determining the change in pH, a pH meter (pH measuring means) may be 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 may be transmitted to the control device at a predetermined cycle. When the pH reaches a predetermined value (range) or when the gradient of the change is within a predetermined range, the electrodialysis is terminated. For example, the tendency of pH change is that the pH of the pure water in the pure water tank gradually drops from near neutral due to the effect of hydrochloric acid being generated as described above, and stabilizes at a low value after a certain period of time. Also, the pH of the cation exchanger regeneration waste liquid in the regeneration waste liquid storage tank gradually rises from the acidic side due to the effect of ions moving to the chamber adjacent to the desalting chamber as described above, and stabilizes at the neutral side from the initial value after a certain period of time. The waste acid in the waste acid storage tank increases gradually due to the effect of ions moving from the adjacent desalting chamber and OH from the bipolar membrane as described above. -As a result of the supply of water, the pH gradually rises from the acidic side.

[0047] 4 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, etc. are not shown. The apparatus shown in Fig. 4 has a configuration in which a nanofiltration membrane (NF) is placed between the cation exchanger packed tower and the regenerated waste liquid storage tank of the apparatus shown in Fig. 3. With this configuration, the cation exchanger regenerated waste liquid that has permeated the NF is supplied to the regenerated waste liquid storage tank.

[0048] NF is Mg 2+ Or Ca 2+ It does not allow divalent ions such as Cl - OrNa + This has the added effect of preventing the accumulation of hardness components and the formation of scale on the membrane surface in the downstream electrodialysis device.

[0049] 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, etc. are not shown. In the apparatus shown in Fig. 5, the desalted water (treated regeneration waste liquid) discharged from the electrodialysis device is not circulated to the regeneration waste liquid storage tank, but is discharged directly to the outside of the system, as compared to the configuration in Fig. 3. Also, in comparison to the configuration in Fig. 3, the recovered acid liquid discharged from the electrodialysis device is not circulated to the pure water tank, but is transferred directly to the acid liquid tank. Also, in comparison to the configuration in Fig. 3, the treated waste acid discharged from the electrodialysis device is not circulated to the waste acid storage tank, but is discharged directly to the outside of the system.

[0050] By adopting the device configuration shown in Fig. 5, it becomes unnecessary to replace the solutions in each tank at the end point of electrodialysis. The regeneration waste liquid is supplied for each regeneration treatment of the cation exchanger, and pure water and waste acid are supplied to the electrodialysis device during the electrodialysis operation in amounts equal to the discharge amounts of the respective liquids. Further, since it is not necessary to monitor the pH of the waste acid (<pH 2, preferably ≤pH 1), the operation can be simplified. Furthermore, each tank of the pure water tank and the waste acid storage tank does not necessarily need to be installed by making the supply flow rate and the discharge flow rate of each solution the same.

[0051] In addition, a part of the configuration shown in Fig. 5 can be made as shown in Fig. 3. For example, it is also possible to adopt a configuration in which the recovered acid solution (treated pure water) and the desalted water (treated regeneration waste liquid) discharged from the electrodialysis device are circulated, and the treated waste acid is discharged as it is without circulation. In order to miniaturize the electrodialysis device and obtain stable treated water quality, it is preferable to circulate the recovered acid solution (treated pure water) and the desalted water (treated regeneration waste liquid).

[0052] The operation method of the electrodialysis device when discharging the desalted water (treated regeneration waste liquid) as it is without circulation may be intermittent operation for each regeneration treatment of the ion exchanger or continuous operation, similar to the case of circulating the desalted water (treated regeneration waste liquid). When continuous operation is adopted, the timing of the end point of the electrodialysis treatment may be made to overlap with the timing of the regeneration of the ion exchanger (start of supply of the regeneration waste liquid). Compared with the intermittent operation, the continuous operation can miniaturize the electrodialysis device, and the supply flow rate of the regeneration waste liquid can be reduced and the timing can be adjusted. Thereby, miniaturization of the electrodialysis device, shortening of the startup time, and stabilization of the treated water quality can be expected.

[0053] When the configuration shown in Fig. 5 is changed to a configuration in which the recovered acid solution (treated pure water) is discharged as it is without circulation, the timing of the end point of the electrodialysis treatment becomes the timing when the regeneration waste liquid runs out. When the configuration shown 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 using the conductivity, pH, operation time, and current value of the above-mentioned pure water tank in addition to the timing when the regeneration waste liquid runs out.

[0054] In the case where the configuration shown in FIG. 5 is modified to circulate the desalted water (treated regenerated waste liquid) and discharge the recovered acid liquid (treated pure water) directly without circulating it, the timing of the end point of the electrodialysis treatment can be determined using the conductivity and pH of the regenerated waste liquid storage tank described above, the operating time, and the current value.

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

[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) Supply water quality: See Table 1 - Liquid fed to the desalination chamber: Waste liquid from the regeneration of a cation exchanger packed tower for producing pure water Supply liquid to the spent acid chamber: Approximately 8% by weight sulfuric acid Supply liquid to the acid recovery chamber: Pure water (reverse osmosis treated water) ·Electrode solution: 4% by mass NaOH ·Water temperature: 20~25℃ (normal temperature) - Amount of liquid supplied to the desalination chamber and circulation flow rate: 850mL, 1.4L / min - Amount of liquid supplied to the waste acid chamber and circulation flow rate: 850mL, 1.4L / min Supply volume and circulation flow rate to the acid recovery chamber: 850mL, 1.4L / min Voltage value: 10V (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 electrical conductivity was measured in each supply liquid tank using an electrical conductivity meter (product name: AOL-10) manufactured by DKK-TOA Corporation. The ions in the liquid were measured using an ion chromatograph (product name: Dionex Integrion) manufactured by Thermo Fisher Scientific Inc. (ion chromatography method).

[0058] (Experimental Results) The changes in conductivity and pH (changes in values ​​over time) of the regenerated waste liquid (demineralized water) fed to the desalting chamber and treated, and the pure water (recovered acid liquid) fed to the acid recovery chamber and treated, are shown in Figure 6, and the changes in the current value of the electrodialysis device (changes in values ​​over time) are shown in Figure 7. The changes in the water quality of each feed liquid are shown in Table 1. As shown in Table 1, the Na in the desalting compartment was reduced by electrodialysis. + Cationic components such as Cl move into the waste acid chamber. - It can be seen that most of the Cl in the desalting compartment has been transferred to the acid recovery compartment after 120 minutes from the start of electrodialysis. - It can be confirmed that the acid was transferred to the acid recovery chamber and HCl (recovered acid liquid) was recovered from the acid recovery chamber.

[0059] In addition, due to the ion migration (Table 1) in the device shown in Fig. 2 described above, as shown in Fig. 6, the conductivity of the pure water (recovered acid liquid) treated in the acid recovery chamber increases and stabilizes at a high value in about 90 minutes, the pH starts near neutral, and after 40 minutes the pH becomes < 1. In addition, the conductivity of the regenerated waste liquid (desalinated water) treated in the desalting chamber decreases and stabilizes at a low value in about 90 minutes, the pH starts near 1, and stabilizes at about pH 3.5 in about 100 minutes.

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

[0061] As described above, in this embodiment, the electrical conductivity of the liquid in the deionization compartment and the acid recovery compartment was stable at about 110 minutes after the start of electrodialysis, and the current flowing between the anode and cathode of the electrodialysis device was also stable at a low value. During the electrodialysis, no decrease in the current value due to scale formation was observed, and no scale material was visible on the ion exchange membrane surface after the electrodialysis. From the above, it is seen that according to the present invention, it is possible to prevent the formation of scale and to stably recover acid from regeneration waste liquid at low cost.

[0062] [Table 1]

[0063] (Reference example 1) Electrodialysis was carried out in the same manner as in Example 1, except that sulfuric acid adjusted to a pH of 3 was fed as the feed liquid to the waste acid compartment. Compared with Example 1, a decrease in the current value (peak current value was less than 2 A, generally low, and finally reached almost 0 A in about 80 minutes) was confirmed. In addition, a deterioration in the quality of the treated water (Cl in the acid recovery chamber 120 minutes after the start of electrodialysis) was confirmed. - Furthermore, 120 minutes after the start of electrodialysis, the inside of the electrodialysis device was checked and white scale was found on the surface of the cation exchange membrane. This was due to Ca(OH) 2 or Mg(OH) 2 It is believed that components such as these precipitated. [Explanation of symbols]

[0064] 1 Anode 3. First Bipolar Membrane (BPM) 5. First Anion Exchange Membrane (AEM) 7 First Cation Exchange Membrane (CEM) 9 Secondary Bipolar Membrane (BPM) 11 Secondary 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 Desalination Room 26 First Waste Acid Room 28 Second Acid Recovery Chamber 30 Second Desalination Room 32 Second Waste Acid Room 34 Cathode Chamber

Claims

1. The catalytic converter includes 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 are 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 compartment 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; a cathode chamber defined by the second bipolar membrane and the cathode; An electrodialysis apparatus in which water is supplied to the acid recovery chamber, an acidic solution is supplied to the deionization chamber, and waste acid is supplied to the waste acid chamber to perform electrodialysis treatment.

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

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

4. 3. The electrodialysis apparatus according to claim 1, 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. A pH measuring means for measuring the pH of the waste acid, 3. The electrodialysis apparatus according to claim 1, wherein the pH of the waste acid measured by the pH measuring means is less than 2 during the entire electrodialysis period.

6. 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 that circulates 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 acidic solution, and a pH measuring means for measuring the pH of the water or the acidic solution; a control device that controls the operation of the acid solution circulating device and receives values ​​measured by at least one of the current measuring device, the conductivity measuring means, and the pH measuring means; 3. The electrodialysis apparatus according to claim 1, wherein the control device circulates the acidic solution using the acidic solution circulating device during electrodialysis treatment, and when at least one value selected from a slope of a current value, a current, a conductivity, and a pH falls within a predetermined range, the control device replaces the circulating acidic solution with the acidic solution outside the circulation system or discharges the circulating acidic solution out of the circulation system at a predetermined ratio or more.

7. A nanofiltration device that separates the acidic solution into a permeate and a concentrate using a nanofiltration membrane; 3. The electrodialysis apparatus according to claim 1, further comprising a line for supplying the permeate to the deionization compartment.

8. An electrodialysis method for treating an acidic solution containing hardness components, comprising the steps of: The catalytic converter 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 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 compartment 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; using an electrodialysis apparatus having a cathode chamber defined by the second bipolar membrane and the cathode, Supplying water to the acid recovery chamber; Supplying the acidic solution to the desalting compartment; A method for electrodialysis comprising supplying waste acid to the waste acid chamber and carrying out electrodialysis.

9. A cation exchange device packed with a cation exchanger; a regenerated liquid storage tank for storing a regenerated liquid of the cation exchanger; and an electrodialysis device for treating a regenerated waste liquid discharged from the cation exchange device to which the regenerated liquid has been supplied, 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 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 compartment 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; 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 acidic solution to the desalting compartment; A means for supplying waste acid to the waste acid chamber; A waste liquid treatment device comprising:

10. supplying a regenerating solution for the cation exchanger to a cation exchanger device packed with the cation exchanger; and subjecting the regenerated wastewater discharged from the cation exchange device to electrodialysis treatment. The electrodialysis treatment step includes: The catalytic converter 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 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 compartment 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; using an electrodialysis apparatus having a cathode chamber defined by the second bipolar membrane and the cathode, Supplying water to the acid recovery chamber; Supplying the regeneration waste liquid to the desalting chamber; A waste liquid treatment method comprising supplying waste acid to the waste acid chamber and subjecting it to electrodialysis treatment.

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