Electrodialysis apparatus and electrodialysis process

Abstract

The present invention relates to an electrodialysis apparatus and an electrodialysis process, the electrodialysis apparatus comprising at least one pair of bipolar membranes arranged adjacent to the positive electrode and the negative electrode, and alternating cation dialysis membranes and anion dialysis membranes, an acid chamber arranged between the bipolar membranes and the anion dialysis membranes and supplied with an acid chamber solution from an acid tank, a salt chamber arranged between the anion dialysis membranes and the cation dialysis membranes and supplied with a salt solution from a salt tank, a base chamber arranged between the cation dialysis membranes and the bipolar membranes and supplied with a base chamber solution from a base tank, and a pump member arranged in connection with the acid tank and the salt tank.

Description

[Technical Field]

[0001] The present invention relates to the production of lithium hydroxide, and more particularly to an electrodialysis apparatus and an electrodialysis process. [Background technology]

[0002] Recently, with the rapid growth of the IT and electric vehicle markets, the demand for lithium, a core raw material for secondary batteries, has increased significantly. The lithium market for secondary batteries is heavily concentrated in South Korea, China, and Japan, but South Korea relies entirely on imports and needs a stable supply and demand method. To this end, research on lithium production is being conducted, including the development of lithium extraction technologies from ore and brine. In South Korea, a demo plant for producing lithium carbonate and lithium hydroxide from ore is in operation. Several companies in South America and China produce large quantities of lithium, and research on lithium production is also underway in South Korea.

[0003] The existing lithium production process in South Korea involves extracting lithium from ore in the form of an aqueous lithium sulfate solution, and then producing it as an aqueous lithium hydroxide solution using electrodialysis. The resulting aqueous lithium hydroxide solution is then crystallized to produce lithium hydroxide monohydrate (LiOH-H2O). The electrodialysis process is a core step in converting the aqueous lithium sulfate solution to an aqueous lithium hydroxide solution and must be operated using a stable and efficient method. [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] The technical problem that this invention aims to solve is to provide an electrodialysis apparatus that maintains the pH of the added salt in order to operate in a stable and efficient manner.

[0005] Another technical problem that the present invention aims to solve is to provide an electrodialysis process that maintains the pH of the salt being introduced in order to operate in a stable and efficient manner. [Means for solving the problem]

[0006] An electrodialysis apparatus according to one embodiment of the present invention may include at least one pair of bipolar membranes arranged adjacent to the positive electrode and the negative electrode, and an acid chamber where cation dialysis membranes and anion dialysis membranes are arranged alternately, and which is located between the bipolar membranes and the anion dialysis membranes and supplied with an acid chamber reaction solution from an acid tank, a salt chamber located between the anion dialysis membranes and the cation dialysis membranes and supplied with a salt solution from a salt tank, a base chamber located between the cation dialysis membranes and the bipolar membranes and supplied with a base chamber reaction solution from a base tank, and a pump member located in connection with the acid tank and the salt tank.

[0007] In one embodiment, the pump member can supply the acidic solution in the acid tank to the saline chamber. In one embodiment, the pump member may be arranged to connect a solution supply unit located at the top of the acid tank and a solution input unit located at the top of the saline tank.

[0008] In one embodiment, a drive unit for operating the pump member may be included. In one embodiment, the drive unit may include a control unit that controls the operation of the pump member according to the pH of the saline chamber.

[0009] In one embodiment, the control unit can drive the pump member to supply an acidic solution from the acid tank to the salt tank when the pH of the salt chamber is 3.0 or higher. In one embodiment, the control unit can stop driving the pump member to prevent the supply of an acidic solution from the acid tank to the salt chamber when the pH of the salt chamber is 1.5 or lower. In one embodiment, a plurality of unit pairs can be arranged in a continuous manner.

[0010] An electrodialysis process in an electrodialysis apparatus comprising at least one pair of bipolar membranes arranged adjacent to a positive electrode and a negative electrode, and alternating arrangements of cation dialysis membranes and anion dialysis membranes, including an acid room arranged between the bipolar membranes and the anion dialysis membranes, a salt room arranged between the anion dialysis membranes and the cation dialysis membranes, and a base room arranged between the cation dialysis membranes and the bipolar membranes, wherein the electrodialysis process separates lithium ions by electrodialysis of a lithium ion-containing solution, and may include a step of supplying the acidic solution from the acid room to the salt room.

[0011] In one embodiment, the step of supplying the acidic solution from the acid chamber to the salt chamber can be performed by supplying it from an acid tank that supplies the acid chamber reaction solution to the acid chamber. In one embodiment, the step of supplying the acidic solution from the acid chamber to the salt chamber can be performed when the pH of the salt chamber is 3 or higher, in which case the acidic solution from the acid chamber can be supplied to the salt chamber.

[0012] In one embodiment, the step of supplying the acidic solution from the acid chamber to the saline chamber does not need to be performed if the pH of the saline chamber becomes 1.5 or less. In one embodiment, in the step of supplying the acidic solution from the acid chamber to the saline chamber, the acidic solution may be an acidic solution that circulates in the acid chamber. [Effects of the Invention]

[0013] An electrodialysis apparatus according to one embodiment of the present invention includes a pump member arranged to connect the acid chamber and the saline chamber, thereby enabling the stable and efficient operation of the apparatus and efficiently maintaining the pH of the salt being introduced.

[0014] In another embodiment of the present invention, the electrodialysis process includes a step of supplying the acidic solution from the acid chamber to the saline chamber, thereby efficiently maintaining the pH of the salt being introduced in order to operate in a stable and efficient manner. [Brief explanation of the drawing]

[0015] [Figure 1] Shows an electrodialysis device according to an embodiment of the present invention. [Figure 2] It is a drawing that simplifies the inside of the stack according to an embodiment of the present invention. [Figure 3] Shows the pH change and current change of salt according to the operation of the acid dosing pump. [Figure 4] Shows the amount of pH change over time in the salt tank of the demo plant. [Figure 5] Shows the amount of pH change over time after the acid dosing pump is provided. [Figure 6] Shows the amount of pH change over time after the acid dosing pump is provided.

Mode for Carrying Out the Invention

[0016] Terms such as first, second, and third are used to describe various parts, components, regions, layers, and / or sections, but are not limited thereto. These terms are used only to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Therefore, the first part, component, region, layer, or section described below may be referred to as the second part, component, region, layer, or section without departing from the scope of the present invention.

[0017] The technical terms used herein are merely for referring to specific embodiments and are not intended to limit the present invention. The singular forms used herein include plural forms as well, unless the context clearly indicates the contrary meaning. The meaning of "including" used in the specification does not exclude the presence or addition of other characteristics, regions, integers, steps, operations, elements, and / or components while embodying specific characteristics, regions, integers, steps, operations, elements, and / or components.

[0018] When we say that one part is "on top of" another part, it means that it is either directly above the other part, or that another part may be in between them. In contrast, when we say that one part is "directly above" another part, there is no other part in between them.

[0019] Furthermore, unless otherwise specified, percentages in this specification refer to percentages by weight.

[0020] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as those generally understood by a person of ordinary skill in the art to which this invention pertains. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with the relevant technical literature and the present disclosures, and are not interpreted in their ideal or highly formal sense unless otherwise defined.

[0021] Embodiments of the present invention will be described in detail below. However, these are presented as examples only, and the present invention is not limited thereto, but is defined solely within the scope of the claims described below.

[0022] An electrodialysis apparatus according to one embodiment of the present invention may include a pair of units arranged in a repeating stack between a positive electrode and a negative electrode connected to a rectifier. The pair of units may be configured to sequentially arrange a bipolar membrane, an anion dialysis membrane, and a cation dialysis membrane. More specifically, the pair of units may be configured to sequentially arrange a bipolar membrane, a spacer gasket, an anion dialysis membrane, a spacer gasket, a cation dialysis membrane, and a spacer gasket.

[0023] The unit pairs in the above configuration can be positioned adjacent to each other in sequence. Of the two adjacent unit pairs, the spacer gasket located downstream of the cation dialysis membrane of the unit pair located further forward can be positioned adjacent to the bipolar membrane of the unit pair located downstream.

[0024] In one embodiment, the electrodialysis apparatus may include at least one pair of bipolar membranes positioned adjacent to the positive and negative electrodes, and alternating cation dialysis membranes and anion dialysis membranes, an acid chamber positioned between the bipolar membranes and the anion dialysis membranes to which an acid chamber reaction solution is supplied from an acid tank, a salt chamber positioned between the anion dialysis membranes and the cation dialysis membranes to which a salt solution is supplied from a salt tank, and a base chamber positioned between the cation dialysis membranes and the bipolar membranes to which a base chamber reaction solution is supplied from a base tank.

[0025] Specifically, a lithium salt aqueous solution is introduced into the salt chamber, an acid chamber solution is introduced into the acid chamber, and a base chamber solution is introduced into the base chamber to perform bipolar electrodialysis.

[0026] At this time, when a voltage is applied to the bipolar electrodialysis machine and current flows, an acid solution may be formed in the acid chamber, an aqueous lithium hydroxide solution may be formed in the base chamber, and a desalinated solution containing residual lithium salt that could not move through the membrane with the introduced lithium salt solution may be formed in the saline chamber.

[0027] Specifically, the formation process of the acid solution and the lithium hydroxide aqueous solution is as follows.

[0028] First, the acid chamber reaction solution introduced into the acid chamber is hydrolyzed on the surface of the bipolar membrane in the acid chamber, decomposing into hydrogen ions and hydroxide ions. At this time, the decomposed hydroxide ions move to the positive electrode cell, and the decomposed hydrogen ions move between the bipolar membrane and the anion dialysis membrane. Meanwhile, the anions of the lithium salt aqueous solution introduced between the anion dialysis membrane and the cation dialysis membrane pass through the anion dialysis membrane and move between the bipolar membrane and the anion dialysis membrane. Then, the hydrogen ions and anions are concentrated between the first bipolar membrane and the anion dialysis membrane to form an acid solution.

[0029] Next, the process by which the lithium hydroxide aqueous solution is formed is as follows: The base chamber reaction solution introduced into the base chamber is hydrolyzed in the water splitting catalyst layer of the bipolar membrane in the base chamber, and decomposed into hydrogen ions and hydroxide ions. At this time, the decomposed hydrogen ions move to the negative electrode cell, and the decomposed hydroxide ions move between the cation dialysis membrane and the bipolar membrane. Meanwhile, the lithium ions of the lithium salt aqueous solution introduced between the anion dialysis membrane and the cation dialysis membrane move through the cation dialysis membrane to the base chamber into which it is introduced. Then, the hydroxide ions and lithium ions are concentrated in the base chamber to form the lithium hydroxide aqueous solution.

[0030] More specifically, the acid group is converted to acid by meeting with hydrogen hydrolyzed in the bipolar membrane on the positive electrode cell side, and the lithium ions moving to the negative electrode through the cation dialysis membrane combine with the hydroxyl group (OH) generated in the bipolar membrane. - It meets with ) and is converted into an aqueous solution of lithium hydroxide (LiOH).

[0031] According to one embodiment, the overall reaction equation is as follows:

[0032] Li2SO4(aq)⇔2Li + (base chamber) + SO4 2- (acid chamber) H2O⇔H + (acid chamber) + OH - (base chamber) Li2SO4(aq)+2H2O⇔2LiOH(aq, base chamber)+H2SO4(aq, acid chamber)

[0033] At this time, the high-concentration lithium salt aqueous solution introduced into the base chamber can be broken down, with lithium ions and acid groups escaping, and a low-concentration lithium salt aqueous solution with some remaining can be generated and discharged outside the electrodialysis machine.

[0034] In one embodiment, the lithium salt may be, for example, a sulfate (Li2SO4), and the acid may be sulfuric acid (H2SO4). On the other hand, the acid chamber effluent solution may be a low-concentration acid or water such as deionized water, and the base chamber effluent solution may be a low-concentration lithium hydroxide aqueous solution or water such as deionized water.

[0035] In one embodiment, the lithium salt aqueous solution formed in the base chamber can be used to perform the same electrodialysis as the previous unit pair by introducing the lithium salt aqueous solution formed in a unit pair located adjacent to the next unit pair into the unit pair located adjacent to the next unit pair. Thus, the electrodialysis apparatus according to one embodiment can be operated by arranging a plurality of unit pairs in a continuous manner.

[0036] In one embodiment, the lithium hydroxide-containing base solution formed and discharged in the base chamber of the electrodialysis apparatus flows into the base tank, the acidic solution formed and discharged in the acid chamber flows into the acid tank, and the desalination solution formed and discharged in the saline chamber flows into the salt tank. Thus, the acid tank, salt tank, and base tank can be components through which the solutions introduced into and discharged from the acid chamber, saline chamber, and base chamber, and the discharged solutions, respectively, circulate.

[0037] In one embodiment, partitions are provided within the acid tank, the saline tank, and the base tank to allow a portion of the solution flowing into each tank to be discharged to the outside, while the remainder is mixed with additionally added water such as deionized water or a salt solution and circulated to the electrodialysis apparatus.

[0038] In one embodiment, the electrodialysis apparatus may include a pump member connected to and positioned in relation to an acid tank and a base tank. The pump member may be a member that supplies the acidic solution from the acid chamber to the saline chamber. Specifically, the pump member may supply the acidic solution provided from the acid chamber to the acid tank to the saline tank, and the acidic solution may be supplied from the saline tank to the saline chamber.

[0039] Specifically, the brine allows Li + ions and SO4 2- ions to move through the cation-exchange membrane and the anion-exchange membrane, respectively. In the bipolar membrane, water is decomposed into H + and OH - ions, which then move to the positive electrode and the negative electrode, respectively. At this time, the pH of the brine introduced diffuses and moves in the acid chamber and the base chamber, respectively, and the amounts of H + and OH - ions can be maintained in good balance.

[0040] At this time, depending on the state of the membrane, the direction of cation or anion movement may change. In one embodiment, when pinholes form in the membrane, a physical flow of the solution through the pinholes occurs, which causes a problem in that the pH of the brine chamber cannot be maintained constant.

[0041] In one embodiment according to the present invention, the pH of the brine can be maintained at 2 to 3.0, specifically 2 to 2.5. Specifically, by maintaining the pH of the brine at 2 to 2.5, when there is a pH change, it is possible to prevent a change in the current applied to the membrane and pursue the stabilization of the process operation, prevent a decrease in the performance of the ion-exchange membrane, and when the desalted liquid is reused, there is an advantage that it can operate stably in the upstream process.

[0042] In one embodiment, the pH of the brine can be maintained by the pump member. Specifically, the pump member can be controlled so that the pH of the brine in the brine chamber is uniformly maintained by supplying the acidic solution in the acid tank to the brine chamber.

[0043] In one embodiment, the pump member can be arranged by connecting a solution supply part arranged at the upper part of the acid tank and a solution input part arranged at the upper part of the brine tank. By arranging the pump member at the upper parts of the acid tank and the brine tank, there is an advantage that the accurate amount of the acidic solution can be supplied to the brine tank.

[0044] In one embodiment, the electrodialysis apparatus may include a drive unit for operating the pump member. The drive unit is electrically connected to the pump member and can control the operation of the pump member. For example, if an opening / closing structure is located within the pump member, the drive unit can assist in opening or closing the opening / closing structure.

[0045] In one embodiment, the drive unit may include a control unit that controls the operation of the pump member according to the pH of the saline chamber. Specifically, the pump member is a member for maintaining the pH of the saline chamber at 2 to 3, and when the pH of the saline chamber is 3 or higher, it may be controlled to supply an acidic solution from the acid tank to lower the pH of the saline in the saline chamber. Specifically, when the pH of the saline chamber is 3 or higher, the pump member can transmit the acidic solution from the acid tank to the saline tank so that the pH of the saline chamber is controlled to be lower than 3.

[0046] In one embodiment, the control unit can stop the operation of the pump member when the pH of the saline chamber is 1.5 or less, thereby preventing the supply of acidic solution from the acid tank to the saline chamber. In this way, the control unit can continuously control the pH of the saline chamber to be maintained within a predetermined range, for example, between 2 and 3.

[0047] In one embodiment, the pump member may further include a sensor unit for measuring the pH of the saline solution near the point of contact with the saline solution tank. The sensor unit is positioned in the pump member near the point of contact with the saline solution tank, more specifically near the solution inlet, and can measure the pH of the saline solution circulating in the saline solution tank. Specifically, the sensor unit can measure the pH of the saline solution and activate the pump member if the pH of the saline solution is 3 or higher, and interrupt the operation of the pump member if the pH of the saline solution is 2 or lower.

[0048] In another embodiment of the present invention, a bipolar electrodialysis process is performed in an electrodialysis apparatus comprising at least one pair of bipolar membranes arranged adjacent to a positive electrode and a negative electrode, and alternating arrangements of cation dialysis membranes and anion dialysis membranes, and including an acid room arranged between the bipolar membranes and the anion dialysis membranes, a salt room arranged between the anion dialysis membranes and the cation dialysis membranes, and a base room arranged between the cation dialysis membranes and the bipolar membranes, wherein a lithium ion-containing solution is electrodialyzed to separate lithium ions, and the process may include a step of supplying the acidic solution from the acid room to the salt room.

[0049] In one embodiment, the step of supplying the acidic solution from the acid chamber to the salt chamber may be performed by supplying it from an acid tank that supplies the acid chamber reaction solution to the acid chamber. Specifically, the acidic solution from the acid chamber may be supplied from the acid tank to the salt tank, and the acidic solution may be supplied from the salt tank to the salt chamber.

[0050] In one embodiment, the step of supplying the acidic solution from the acid chamber to the salt chamber may be omitted if the pH of the salt chamber is 3 or higher. In another embodiment, the step of supplying the acidic solution from the acid chamber to the salt chamber may be omitted if the pH of the salt chamber is 1.5 or lower. In this way, when the pH of the salt chamber becomes high, the acidic solution can be used to control the concentration of the salt chamber by maintaining the pH of the salt chamber uniformly within a predetermined range.

[0051] In one embodiment, the acidic solution may be an acidic solution circulating in the acid chamber. Specifically, the acidic solution may be supplied to the salt chamber by a pump member connected to the acid tank and the salt tank, and the explanation relating thereto is the same as that given above, to the extent that it does not contradict the previous explanation. [Examples]

[0052] To illustrate the present invention in more detail, embodiments of the present invention are described below. The embodiments described below are merely one example of the present invention, and the present invention is not limited to these embodiments.

[0053] <Example of experiment> Figure 1 shows an electrodialysis machine according to one embodiment of the present invention.

[0054] Referring to Figure 1, in the electrodialysis apparatus of the present invention, saline solution is introduced into a pump component (Salt Tank) connected to the No. 1 press. DI water is introduced into the base tank and acid tank from the No. 3 press side using a countercurrent. The introduced solution is circulated to the upper stack, and ions move within the stack through an ion exchange membrane.

[0055] Figure 2 is a simplified diagram of the inside of a stack according to one embodiment of the present invention.

[0056] Referring to Figure 2, the salt solution enters the stack, and Li passes through the cation and anion membranes. + Ions and SO4 2- Ions are transferred. In a bipolar membrane, water is broken down and H + and OH - Ions move to the positive and negative electrodes, respectively. LiOH is produced in the base chamber, and a sulfuric acid solution is formed in the acid chamber.

[0057] At this time, the pH of the salt introduced into the electrodialysis process in the conventional lithium process is adjusted by the diffusion of H by adjusting the concentrations of base and acid. + and OH -The balance of these quantities is controlled. This involves adjusting the amounts of base DIW (Base DI water) and acid DIW (Acid DI water) added to control the concentrations of base and acid in the process. When the process is running normally, pH control is easy, but it becomes impossible when pinholes or pores are created in the cation membrane due to burning.

[0058] In contrast, the present invention includes a pump member that connects the acid chamber and the saline chamber, thereby supplying the acidic solution to the saline chamber.

[0059] Figure 3 shows the pH and current changes of the salt as the acid dosing pump operates.

[0060] Referring to Figure 3, it can be confirmed that when the acid dosing pump, specifically the pump component of the present invention, is in operation, the current decreases over time and the pH of the salt increases over time.

[0061] Figure 4 shows the change in pH over time in the salt tank of the demonstration plant.

[0062] Figure 4 shows the change in pH over time in an electrodialysis apparatus without the pump component of the present invention. Specifically, Figure 4 shows the PDS data for pH in the salt tank of a conventional demo plant. More specifically, the data in Figure 4 is automatically measured every minute and represents 40 days of data.

[0063] When operating a conventional demo plant, specifically when using Astom's anionic membrane, it can be confirmed that the pH is maintained at a constant level of 1.5. However, it can be confirmed that the pH does not increase beyond approximately 25,000 minutes. This indicates that, due to the prolonged operation of the electrodialysis machine, certain problems occur in the cation membrane, such as the formation of pinholes or pores due to burning, making pH control difficult.

[0064] Figures 5 and 6 show the change in pH over time in an electrodialysis apparatus equipped with a pump component.

[0065] Figure 5 shows the change in pH of the salt over time in the electrodialysis apparatus of the present invention equipped with a pump component. Referring to Figure 5, it can be confirmed that, unlike the conventional demo plant in Figure 4, the pH is maintained at approximately 1.5.

[0066] Figure 6 shows the result of adjusting the y-axis scale of Figure 5. Specifically, it represents a case where the pump component starts operating at pH 1.6 and stops operating at pH 1.5. After setting up and running the process, a sawtooth-shaped graph was observed between pH 1.5 and 1.6. This confirmed the advantage that the process for maintaining the pH of the salt can also be automated.

[0067] Thus, the electrodialysis apparatus of the present invention includes a pump component that supplies the acidic solution from the acid chamber to the saline chamber. By adjusting the pH of the saline chamber with the pump component, the pH of the salt can be kept constant without the addition of additional raw materials or additional processes. Furthermore, it has the advantage of maintaining a uniform pH of the salt even if cracks occur in the cation membrane during the electrodialysis process which is carried out over a long period of time.

[0068] The present invention is not limited to the embodiments described above, and can be manufactured in a variety of different forms. Those with ordinary skill in the art to which the invention pertains should understand that it can be implemented in other specific forms without altering the technical idea or essential features of the invention. Therefore, it should be understood that the embodiments described above are illustrative and not limiting in all respects.

Claims

1. At least one pair of bipolar membranes are positioned adjacent to the positive and negative electrodes, and cation dialysis membranes and anion dialysis membranes are arranged alternately. An acid chamber is positioned between the bipolar membrane and the anion dialysis membrane, and is supplied with an acid chamber solution from an acid tank; A salt solution chamber is located between the anion dialysis membrane and the cation dialysis membrane, and is supplied with saline solution from a salt tank; A base chamber, which is arranged in the cation dialysis membrane and the bipolar membrane and supplied with base chamber solution from a base tank; and An electrodialysis apparatus including a pump member connected to the acid tank and the salt tank.

2. The electrodialysis apparatus according to claim 1, wherein the pump member supplies the acidic solution in the acid tank to the saline chamber.

3. The electrodialysis apparatus according to claim 1, wherein the pump member is arranged to connect a solution supply unit located at the top of the acid tank and a solution input unit located at the top of the saline tank.

4. The electrodialysis apparatus according to claim 1, further comprising a drive unit for operating the pump member.

5. The electrodialysis apparatus according to claim 4, wherein the drive unit includes a control unit that controls the operation of the pump member according to the pH of the saline chamber.

6. The control unit, when the pH of the saline chamber is 3.0 or higher, The electrodialysis apparatus according to claim 5, wherein the pump member is driven to supply an acidic solution from the acid tank to the salt tank.

7. The control unit, when the pH of the saline chamber is 1.5 or less, The electrodialysis apparatus according to claim 6, wherein the drive of the pump member is stopped to prevent the supply of an acidic solution from the acid tank to the saline chamber.

8. The electrodialysis apparatus according to claim 1, wherein multiple unit pairs are arranged in a continuous manner.

9. An electrodialysis apparatus comprising at least one pair of bipolar membranes arranged adjacent to the positive electrode and the negative electrode, and alternating arrangements of cationic dialysis membranes and anionic dialysis membranes, including an acid room arranged between the bipolar membranes and the anionic dialysis membranes, a salt room arranged between the anionic dialysis membranes and the cationic dialysis membranes, and a base room arranged between the cationic dialysis membranes and the bipolar membranes, wherein a bipolar electrodialysis process separates lithium ions by electrodialysis of a lithium ion-containing solution, An electrodialysis process comprising the step of supplying the acidic solution from the acid chamber to the saline chamber.

10. The electrodialysis process according to claim 8, wherein the step of supplying the acidic solution from the acid chamber to the saline chamber is supplied from an acid tank that supplies the acid chamber reaction solution to the acid chamber.

11. The electrodialysis process according to claim 8, wherein the step of supplying the acidic solution from the acid chamber to the saline chamber is performed such that when the pH of the saline chamber is 3 or higher, the acidic solution from the acid chamber is supplied to the saline chamber.

12. The electrodialysis process according to claim 8, wherein the step of supplying the acidic solution from the acid chamber to the saline chamber is a step in which the acidic solution is not supplied to the saline chamber if the pH of the saline chamber becomes 1.5 or less.

13. In the step of supplying the acidic solution from the acid chamber to the salt chamber, The electrodialysis process according to claim 8, wherein the acidic solution is an acidic solution circulating in the acid chamber.

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