Electrodeionization device for ultrapure water production

Abstract

The application discloses an electrodeionization device for ultrapure water preparation, and relates to the technical field of water treatment, which comprises a shell, an electrodeionization chamber, a cathode chamber, an anode chamber and a cation replacement module, a deionization module is arranged between the cation replacement module and the cathode chamber, a concentrated water chamber is arranged between the deionization module and the cation replacement module, the deionization module comprises a first cation exchange membrane, a de-cationic fresh water chamber, a first bipolar membrane, a de-anionic fresh water chamber and a first anion exchange membrane arranged in sequence, the cation replacement module comprises a second cation exchange membrane, a cation replacement chamber, a third cation exchange membrane, an ion supply chamber and a second anion exchange membrane arranged in sequence, and water to be treated flows through the cation replacement chamber, the de-anionic fresh water chamber and the de-cationic fresh water chamber in sequence, and the ion supply chamber is provided with a strong acid and strong base salt solution. The device has the advantages of high-efficiency removal of soluble acidic gas, reduction of the risk of concentrated water chamber fouling and improvement of the resistivity of produced water.

Description

Technical Field

[0001] This application relates to the field of water treatment technology, and in particular to an electro-deionization device for the preparation of ultrapure water. Background Technology

[0002] Electrodeionization (EDI) technology, as a highly efficient and environmentally friendly water treatment process, has important applications in various fields. This technology achieves deep desalination of water through ion exchange membranes and electric field drive. However, it still faces two key technical challenges in practical applications: First, existing devices are ineffective at removing dissolved acidic gases, especially carbon dioxide. Since dissolved acidic gases are dissolved in water in molecular form, they cannot be removed by removing anions or cations during EDI, resulting in permeate that cannot meet the requirements for high dissolved acidic gas content in some applications. Second, the concentrate chamber and electrode chamber are prone to precipitation and scaling due to the ion concentration effect, affecting the performance and lifespan of the membrane modules. Traditional solutions, such as adding degassing devices or adjusting operating parameters, often suffer from increased energy consumption, the introduction of new impurities, or reduced permeate efficiency. Especially when treating raw water containing weakly alkaline cations, conventional EDI devices struggle to simultaneously address both residual acidic gases and scaling, severely hindering the development of ultrapure water preparation processes. Therefore, existing technologies urgently need improvement to address these issues. Summary of the Invention

[0003] The purpose of this application is to provide an electro-deionization device for the preparation of ultrapure water, which has the advantages of efficiently removing dissolved acidic gases, reducing the risk of scaling in the concentrate chamber, and improving the resistivity of the product water.

[0004] To achieve the above objectives, this application adopts the following technical solution:

[0005] An electro-deionization device for ultrapure water preparation includes a housing and an electro-deionization chamber disposed within the housing. The electro-deionization chamber contains a cathode chamber and an anode chamber. At least one cation exchange module is disposed between the cathode chamber and the anode chamber. At least one deionization module is disposed between the cation exchange module and the cathode chamber. At least one concentrate chamber is disposed between the deionization module and the cation exchange module. The deionization module includes a first cation exchange membrane, a first bipolar membrane, and a first anion exchange membrane arranged sequentially from the cathode chamber side to the anode chamber side. A decation deionization chamber is disposed between the first cation exchange membrane and the first bipolar membrane, and a deionization chamber is disposed between the first bipolar membrane and the first anion exchange membrane. The cation exchange module includes a second cation exchange membrane, a third cation exchange membrane, and a second anion exchange membrane arranged sequentially from the cathode chamber side to the anode chamber side. A cation exchange chamber is disposed between the second cation exchange membrane and the third cation exchange membrane, and an ion supply chamber is disposed between the third cation exchange membrane and the second anion exchange membrane. The water to be treated flows sequentially through the cation exchange chamber, the deionization chamber, and the decationization chamber. The ion supply chamber contains a strong acid / strong base / salt solution.

[0006] In the above technical solution, raw water first enters the cation exchange chamber. Within this chamber, formed by the second and third cation exchange membranes, weakly basic cations are replaced by strongly basic cations. The water then flows to the anion removal desalination chamber, where an alkaline environment is created by hydroxide ions generated by the first bipolar membrane. This environment promotes the dissociation of acidic gases such as carbon dioxide into anions, which then pass through the anion exchange membrane into the concentrate chamber. Subsequently, the water flows into the cation removal desalination chamber, where cation migration occurs, and the cations enter the concentrate chamber or the cathode chamber. The water produced by the cation removal desalination chamber is ultrapure water. The ion supply chamber continuously releases sodium or potassium ions, replenishing the replacement chamber with the necessary cations through the third cation exchange membrane. Through this technical solution, this application effectively reduces the residual concentration of acidic gases such as carbon dioxide in the product water, while simultaneously inhibiting the formation of calcium and magnesium carbonate precipitates in the concentrate and cathode chambers. The replaced sodium and potassium ions form highly soluble salts with the acid radicals, preventing scaling on the membrane surface and resin clogging.

[0007] Furthermore, this application proposes that the number of cation exchange modules and the number of deionization modules be multiple, with the deionization modules and cation exchange modules arranged alternately. This technical solution can increase the number of cation exchange modules and deionization modules, thereby increasing the water treatment capacity of the electro-deionization device.

[0008] Furthermore, this application also proposes that the deionization module and the cation replacement module correspond one-to-one, and the deionization module and the corresponding cation replacement module are arranged adjacent to each other and form a set of purification components. In the set of purification components, the deionization module is located on the side closer to the cathode chamber relative to the cation replacement module, and the cation replacement chamber, the deionized anion desalination chamber and the deionized cation desalination chamber are connected in sequence.

[0009] The above technical solution decomposes the treatment process into standardized units through modular design. Water completes three-stage purification within a single unit, shortening the migration path and reducing concentration gradient differences during ion exchange. The independent operation mechanism of each unit avoids ion interference between different modules, ensuring that weakly basic cations are fully removed during the replacement stage, reducing the risk of precipitation in subsequent treatments, and simplifying system maintenance and expansion operations. Using multiple units in parallel can increase the overall water treatment capacity of the electro-deionization device.

[0010] Furthermore, this application also proposes that the electro-deionization chamber is provided with at least one isolation module, the side of the isolation module near the cathode chamber is a deionization module and a first concentrate chamber is provided between the two, the side of the isolation module near the anode chamber is a cation exchange module and a second concentrate chamber is provided between the two, the isolation module includes a fourth cation exchange membrane and a third anion exchange membrane arranged sequentially and spaced apart from the cathode chamber side to the anode chamber side, an isolation chamber is provided between the fourth cation exchange membrane and the third anion exchange membrane, the isolation chamber contains a strong acid and strong base salt solution, and the anions in the strong acid and strong base salt solution are nitrate ions and / or chloride ions.

[0011] In the above technical solution, driven by an electric field, anions in the deionized water chamber enter the first concentrated water chamber through the third anion exchange membrane, while weakly basic cations in the cation exchange chamber enter the second concentrated water chamber through the fourth cation exchange membrane. The sodium nitrate or potassium chloride solution filled in the isolation chamber allows nitrate or chloride ions to migrate to the second concentrated water chamber through the third anion exchange membrane. Because the salts formed by nitrate or chloride ions and weakly basic cations have extremely high solubility, the formation of calcium carbonate or calcium sulfate precipitates in the second concentrated water chamber can be effectively avoided. Simultaneously, sodium or potassium ions in the isolation chamber migrate to the first concentrated water chamber through the fourth cation exchange membrane, forming easily soluble salts with the anions in the first concentrated water chamber, further reducing the risk of precipitation in the first concentrated water chamber.

[0012] Furthermore, this application also proposes a supply chamber for supplying strong acid and strong base salt solutions to the ion supply chamber and the isolation chamber, the supply chamber being connected to the ion supply chamber and the isolation chamber, and the supply chamber having an addition port.

[0013] Through the above technical solution, this application achieves centralized supply and dynamic balance of salt solution in the ion supply chamber and the isolation chamber, solves the problem of concentration decay caused by inconvenience in salt solution replenishment in traditional technology, ensures the long-term stability of cation exchange efficiency and isolation function, and reduces the risk of operational errors caused by frequent feeding.

[0014] Furthermore, this application proposes that at least two cation exchange modules are arranged adjacently to form a first exchange module group; the side of the first exchange module group closest to the cathode chamber is arranged adjacent to the deionization module and a third concentrate chamber is provided between them; a fourth concentrate chamber is provided between two adjacent cation exchange modules in the first exchange module group; the cation exchange chamber adjacent to the third concentrate chamber in the first exchange module group is the first cation exchange chamber, and the cation exchange chamber adjacent to the fourth concentrate chamber is the second cation exchange chamber; in the first exchange module group, the water to be treated first flows through the second cation exchange chamber and then flows into the first cation exchange chamber; the anions in the strong acid and strong base salt solution are nitrate ions and / or chloride ions.

[0015] By using the above technical solution, two deionization modules are connected in parallel to form a first replacement module group, and the water to be treated first flows through the second cation replacement chamber and then into the first cation replacement chamber. This not only increases the cation replacement effect, but also reduces the risk of precipitation in the third and fourth concentrate chambers.

[0016] Furthermore, this application also proposes that there be multiple cation exchange modules, with the cation exchange chambers of the multiple cation exchange modules connected in sequence; there be multiple deion modules, with the deionization desalination chambers of the multiple deion modules connected in sequence; and the deionization desalination chambers of the multiple deion modules connected in sequence. The water to be treated flows sequentially through the multiple cation exchange chambers, the multiple deionization desalination chambers, and the multiple deionization desalination chambers.

[0017] Through the above technical solutions, this application can achieve full replacement of weakly alkaline cations, reducing the risk of precipitation due to combination with acid radicals in subsequent treatment; the multi-stage deionization desalination chamber removes acidic gases in stages under alkaline conditions, improving the removal efficiency of pollutants such as carbon dioxide; the series structure optimizes the water flow path, avoiding the structural complexity of the concentrate chamber caused by parallel connection of multiple modules, and reducing the possibility of scaling.

[0018] Furthermore, this application also proposes that the liquid flow directions of the cation exchange chamber and the concentrate chamber on both sides of the second cation exchange membrane are opposite, and a second bipolar membrane is provided near the liquid outlet of the cation exchange chamber of the second cation exchange membrane. The liquid outlet of the cation exchange chamber and the liquid inlet of the concentrate chamber are separated by the second bipolar membrane. The side of the second bipolar membrane that generates hydroxide ions faces the cation exchange chamber, and the side of the second bipolar membrane that generates hydrogen ions faces the concentrate chamber.

[0019] Specifically, when the liquid flows through the inlet of the concentrate chamber, hydrogen ions released by the second bipolar membrane enter the concentrate chamber, increasing the hydrogen ion concentration and lowering the pH value. This inhibits the dissociation of acid radicals, thereby reducing the risk of precipitation caused by the combination of weakly basic cations and acid radicals, ensuring the membrane flux and ion exchange efficiency of the electro-deionization device during long-term operation. The second bipolar membrane is positioned near the outlet of the cation exchange chamber. When the solution that has undergone cation exchange in the cation exchange chamber flows out through the outlet, a large amount of the weakly basic cations have been replaced, resulting in a significant decrease in their content. Even if hydroxide ions released by the second bipolar membrane enter this area, they are unlikely to cause precipitation. Furthermore, the hydroxide ions released by the second bipolar membrane can increase the alkalinity of the liquid flowing out of the cation exchange chamber. After flowing out of this area, the liquid enters the anion deionization chamber, where the hydroxide ions released by the second bipolar membrane help dissociate the acidic gases into anions within the anion deionization chamber.

[0020] Furthermore, this application also proposes that the cathode chamber is arranged adjacent to the deionization desalination chamber, and the anode chamber is arranged adjacent to the ion supply chamber; the liquid in the anode chamber flows into the cathode chamber.

[0021] In the above technical solution, the cathode chamber and the deionized water chamber are arranged adjacent to each other, ensuring that the cations entering the cathode chamber are all cations flowing out of the cation exchange chamber, resulting in a low content of weakly alkaline cations that are less likely to precipitate in the cathode chamber. Similarly, the anode chamber and the ion supply chamber are arranged adjacent to each other, ensuring that the anions entering the anode chamber are all acid radicals from the ion supply chamber. By using suitable acid radicals, such as sulfate or nitrate ions, instead of chloride ions, the generation of toxic chlorine gas in the anode chamber can be avoided. In this technical solution, the acidic solution in the anode chamber flows into the cathode chamber under the drive of an electric field, mixing with the alkaline solution in the cathode chamber. The hydrogen ions generated in the anode chamber neutralize the hydroxide ions generated in the cathode chamber, reducing the alkalinity in the cathode chamber and thus lowering the risk of precipitation in the cathode chamber.

[0022] An electro-deionization device for ultrapure water preparation includes a housing and an electro-deionization chamber disposed within the housing. The electro-deionization chamber contains a cathode chamber and an anode chamber. At least one cation exchange module is disposed between the cathode chamber and the anode chamber. At least one deionization module is disposed between the cation exchange module and the cathode chamber. At least one concentrate chamber is disposed between the deionization module and the cation exchange module. The deionization module includes a first cation exchange membrane, a first bipolar membrane, and a first anion exchange membrane arranged sequentially and spaced apart from the cathode chamber side to the anode chamber side. A deionization desalination chamber is disposed between the first cation exchange membrane and the first bipolar membrane, and a deionization desalination chamber is disposed between the first bipolar membrane and the first anion exchange membrane. The cation exchange module includes a second cation exchange membrane and a third cation exchange membrane arranged sequentially and spaced apart from the cathode chamber side to the anode chamber side. A cation exchange chamber is disposed between the second cation exchange membrane and the third cation exchange membrane. Water to be treated flows sequentially through the cation exchange chamber, the deionization desalination chamber, and the deionization desalination chamber. A strong acid / strong base salt solution is disposed opposite the cation exchange chamber and located on the other side of the third cation exchange membrane.

[0023] Through the above technical solution, this application effectively reduces the residual concentration of acidic gases such as carbon dioxide in the product water, while inhibiting the formation of calcium and magnesium carbonate precipitates in the concentrate and cathode chambers. The replaced sodium and potassium ions form highly soluble salts with the acid radicals, preventing scaling on the membrane surface and resin clogging. The alkaline environment regulated by the bipolar membrane promotes the complete dissociation of acidic gases, improving the adsorption efficiency of the anion exchange membrane for carbonate ions, ultimately achieving dual optimization of pollutant removal and stable system operation in the ultrapure water preparation process. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of this application. Figure 1 ;

[0025] Figure 2 This is a schematic diagram of the structure of this application. Figure 2 ;

[0026] Figure 3 This is a schematic diagram of the structure of Embodiment 2 of this application;

[0027] Figure 4 This is a schematic diagram of the structure of Embodiment 3 of this application;

[0028] Figure 5 This is a schematic diagram of the structure of embodiment 3 of this application. Figure 2 ;

[0029] Figure 6 This is a schematic diagram of the structure of Embodiment 4 of this application;

[0030] Figure 7 This is a schematic diagram of the structure of Embodiment 5 of this application;

[0031] Figure 8 Schematic diagram of embodiment 6 of this application Figure 1 ;

[0032] Figure 9 Schematic diagram of embodiment 6 of this application Figure 2 .

[0033] In the diagram: Cathode chamber 1, Anode chamber 2, Deionization module 3, First cation exchange membrane 31, First bipolar membrane 32, First anion exchange membrane 33, Deionized water desalination chamber 34, Deionized water desalination chamber 35, Cation replacement module 4, First replacement module group 40, Second cation exchange membrane 41, Third cation exchange membrane 42, Second anion exchange membrane 43, Cation replacement chamber 44, First cation replacement chamber 441, Second cation replacement chamber 442, Ion supply chamber 45, Concentrate chamber 5, First concentrate chamber 51, Second concentrate chamber 52, Third concentrate chamber 53, Fourth concentrate chamber 54, Second bipolar membrane 6, Isolation module 7, Fourth cation exchange membrane 71, Third anion exchange membrane 72, Isolation chamber 73, Purification component 8. Detailed Implementation

[0034] The present application will now be further described with reference to the accompanying drawings and specific embodiments.

[0035] Example 1:

[0036] like Figure 1As shown, an electro-deionization device for ultrapure water preparation includes a shell and an internal electro-deionization chamber, within which a cathode chamber 1 and an anode chamber 2 are disposed. At least one cation exchange module 4 is disposed between the cathode chamber 1 and the anode chamber 2. A deionization module 3 is disposed between the cation exchange module 4 and the cathode chamber 1. At least one concentrate chamber 5 is disposed between the deionization module 3 and the cation exchange module 4. The deionization module 3 consists of a first cation exchange membrane 31, a first bipolar membrane 32, and a first anion exchange membrane 33 arranged sequentially and at intervals from the cathode chamber 1 side to the anode chamber 2 side, forming a decation-deionized desalination chamber 34 and a deionized desalination chamber 35. The side of the bipolar membrane that generates hydroxide ions faces the deionized desalination chamber 35, and the side that generates hydrogen ions faces the decation-deionized desalination chamber 34. The cation exchange module 4 comprises a second cation exchange membrane 41, a third cation exchange membrane 42, and a second anion exchange membrane 43 arranged sequentially from the cathode chamber 1 to the anode chamber 2. A cation exchange chamber 44 is formed between the second cation exchange membrane 41 and the third cation exchange membrane 42, and an ion supply chamber 45 is formed between the third cation exchange membrane 42 and the second anion exchange membrane 43. The water to be treated flows sequentially through the cation exchange chamber 44, the anion-removing desalination chamber 35, and the cation-removing desalination chamber 34. The ion supply chamber 45 stores strong acid and strong base salt solutions. An anode plate is installed in the anode chamber 2, and a cathode plate is installed in the cathode chamber 1. The liquids in the concentrate chamber 5, anode chamber 2, and cathode chamber 1 can be directly supplied to the raw water to be treated, and discharged as wastewater after passing through the concentrate chamber 5, anode chamber 2, or cathode chamber 1. The ion types listed in the figure are for reference only and do not include all ions.

[0037] The cation exchange module 4 refers to an ion exchange space constructed through a cation exchange membrane, specifically a chamber filled with sodium or potassium cation exchange resin. This ion exchange reaction replaces calcium and magnesium ions in the raw water with sodium and potassium ions. The bipolar membrane in the deionization module 3 is a composite membrane with water dissociation capabilities, specifically a composite structure of anion and cation exchange layers. It decomposes water molecules to produce hydroxide and hydrogen ions through an electric field. The concentrate chamber 5 refers to an ion enrichment channel located between the modules. The ion supply chamber 45 is a chamber storing a high-concentration salt solution, maintaining the efficiency of the exchange reaction by continuously supplying sodium or potassium ions.

[0038] Specifically, raw water first enters the cation exchange chamber 44, where weakly alkaline cations are replaced by strongly alkaline cations, formed by the second cation exchange membrane 41 and the third cation exchange membrane 42. The replaced water flows to the anion removal desalination chamber 35, where an alkaline environment is created by hydroxide ions generated by the first bipolar membrane 32. This causes acidic gases such as carbon dioxide to dissociate into anions, which then pass through the anion exchange membrane into the concentrate chamber 5. The water then flows into the cation removal desalination chamber 34, where cations migrate and enter either the concentrate chamber 5 or the cathode chamber 1. The water produced by the cation removal desalination chamber 34 is ultrapure water. Meanwhile, the ion supply chamber 45 continuously releases sodium or potassium ions, which replenish the cations required for replacement in the cation exchange chamber 44 through the third cation exchange membrane 42.

[0039] Compared to existing technologies, traditional devices rely on a single ion exchange process, resulting in both acidic gas residue and scaling. This solution eliminates the source of weakly alkaline cations through pre-replacement and combines this with a bipolar membrane to create an alkaline environment that alters the form of acidic gases, achieving synergistic removal of both pollutants. Compared to adding degassing equipment or chemical scale inhibitors, this solution eliminates the need for external devices or additives, completing the pollutant transformation and retention within the system, ensuring both the purity of the produced water and avoiding the risk of secondary pollution.

[0040] Through the above technical solution, this application effectively reduces the residual concentration of acidic gases such as carbon dioxide in the product water, while inhibiting the formation of calcium and magnesium carbonate precipitates in the concentrate chamber 5 and the cathode chamber. The replaced sodium and potassium ions form highly soluble salts with the acid radicals, preventing scaling on the membrane surface and resin blockage.

[0041] This application further proposes that the cathode chamber 1 is arranged adjacent to the deionized water chamber 34, and the anode chamber 2 is arranged adjacent to the ion supply chamber 45.

[0042] In the above technical solution, the cathode chamber 1 and the deionized freshwater chamber 34 are arranged adjacent to each other, so that the cations entering the cathode chamber 1 are all cations flowing out of the cation replacement chamber 44, and the content of weakly alkaline cations is low, making it difficult for them to precipitate in the cathode chamber 1; the anode chamber 2 and the ion supply chamber 45 are arranged adjacent to each other, so that the anions entering the anode chamber 2 from the ion supply chamber 45 are all acid radical ions from the ion supply chamber 45. By using appropriate acid radical ions, such as sulfate ions or nitrate ions, instead of chloride ions, the generation of toxic chlorine gas in the anode chamber 2 can be avoided.

[0043] like Figure 2As shown, this application further proposes that the liquids in the cation exchange chamber 44 and the concentrate chamber 5 flow in opposite directions on both sides of the second cation exchange membrane 41. A second bipolar membrane 6 is provided on the second cation exchange membrane 41 near the outlet end of the cation exchange chamber 44. The outlet end of the cation exchange chamber 44 and the inlet end of the concentrate chamber 5 are separated by the second bipolar membrane 6. The side of the second bipolar membrane 6 that generates hydroxide ions faces the cation exchange chamber 44, and the side that generates hydrogen ions faces the concentrate chamber 5.

[0044] The reverse flow design refers to the opposite flow directions of the liquids in the cation exchange chamber 44 and the concentrate chamber 5. The second bipolar membrane 6 is an ion exchange membrane composed of anion exchange layers and cation exchange layers. Under the action of a DC electric field, it dissociates water molecules into hydrogen ions and hydroxide ions. The hydroxide ion release side faces the cation exchange chamber 44, and the hydrogen ion release side faces the concentrate chamber 5.

[0045] Specifically, when the liquid flows through the inlet of the concentrate chamber 5, hydrogen ions released by the second bipolar membrane 6 enter the concentrate chamber 5, increasing the hydrogen ion concentration and decreasing the pH value of the concentrate chamber 5. This inhibits the dissociation of acid radicals, thereby reducing the risk of precipitation caused by the combination of weakly basic cations and acid radicals, ensuring the membrane flux and ion exchange efficiency of the electro-deionization device during long-term operation. The second bipolar membrane 6 is located near the outlet of the cation exchange chamber 44. When the solution that has completed cation exchange in the cation exchange chamber 44 flows out through the outlet, a large amount of weakly basic cations have been replaced, and the content has decreased significantly. Even if the hydroxide ions released by the second bipolar membrane 6 enter this area, it is not easy for the liquid to precipitate. Furthermore, the hydroxide ions released by the second bipolar membrane 6 can also increase the alkalinity of the liquid flowing out of the cation exchange chamber 44. After flowing out of this area, the liquid enters the deionization desalination chamber 35. The hydroxide ions released by the second bipolar membrane 6 help dissociate the acidic gas in the deionization desalination chamber 35 into anions.

[0046] This application further proposes that the cations in the strong acid-strong base salt solution are sodium ions and / or potassium ions; and the anions in the strong acid-strong base salt solution are nitrate ions and / or sulfate ions and / or chloride ions.

[0047] Sodium or potassium ions refer to strongly alkaline metal cations, which can be achieved using soluble salts such as sodium nitrate or potassium sulfate. The compounds they form with acid anions have high solubility in aqueous solutions, preventing precipitation caused by ion concentration in the concentrate chamber 5. Nitrate, sulfate, or chloride ions refer to strongly acidic anions, which can also be achieved using salts such as sodium nitrate, potassium sulfate, or sodium chloride, avoiding the formation of sparingly soluble salts by combining with weakly alkaline cations. Sodium or potassium ions can be used simultaneously or individually. Nitrate, sulfate, and chloride ions can be used simultaneously or individually.

[0048] Preferably, the anion in the strong acid-strong base salt solution is nitrate ion. Nitrate ions can combine with weakly basic cations to form easily soluble salts, and they remain stable after entering the anode chamber, without producing toxic gases at the anode.

[0049] This application further proposes a supply chamber for supplying strong acid and strong base salt solutions to the ion supply chamber 45. The supply chamber is connected to the ion supply chamber 45 and has an addition port.

[0050] The supply chamber is a sealed container independent of the electro-deionization chamber. It can be made of corrosion-resistant polypropylene or PVDF material and forms a closed loop with the ion supply chamber 45 via a pipeline, used for storing and circulating the salt solution. The addition port is an openable interface located at the top of the supply chamber, which can be a flange connection or a threaded seal structure, used to replenish the salt solution or salt into the supply chamber. Its function is to simplify the salt solution replenishment operation and ensure the stability of the salt concentration during system operation. The ion supply chamber 45 in this application only supplies anions and cations to both sides, without introducing other impurity ions. During long-term operation, the ion concentration of the solution within the ion supply chamber 45 will only decrease.

[0051] Specifically, the supply chamber forms a circulation loop with the ion supply chamber 45 via a connecting pipe. The salt solution continuously flows into the ion supply chamber 45 under gravity or pump drive, maintaining its internal salt concentration. When the salt solution concentration decreases due to ion migration or water dilution, the operator directly injects a high-concentration salt solution into the supply chamber through the addition port to compensate for the loss. Because the supply chamber is connected to both functional chambers, the newly added salt solution can be quickly and evenly distributed through circulation, avoiding localized excessively high or low concentrations. For example, during system operation, sodium ions in the ion supply chamber 45 will be gradually consumed by the displacement reaction; at this time, adding sodium nitrate solution through the addition port can simultaneously restore the salt concentration in both chambers.

[0052] This solution uses a single supply chamber for unified supply, combined with a circulating interconnection design, which not only reduces the frequency of manual intervention, but also achieves automatic balancing of salt concentration through dynamic circulation, significantly improving the continuity of system operation.

[0053] Through the above technical solution, this application achieves centralized supply and dynamic balance of salt solution in ion supply chamber 45, solves the problem of concentration decay caused by inconvenience in salt solution replenishment in traditional technology, ensures the long-term stability of cation exchange efficiency and isolation function, and reduces the risk of operational errors caused by frequent feeding.

[0054] This application further proposes that the liquid in the anode chamber 2 flows into the cathode chamber 1.

[0055] The anode chamber 2 is located near the anode side of the electrodeionization chamber. It is filled with anolyte and undergoes an oxidation reaction under an electric field, producing hydrogen ions and an acidic environment. This is achieved by connecting an anode electrode to the positive terminal of a DC power supply. The acidic environment helps maintain the electric field strength required for ion migration. The cathode chamber 1 is located near the cathode side of the electrodeionization chamber. It is filled with catholyte and undergoes a reduction reaction under an electric field, producing hydroxide ions and an alkaline environment. This is achieved by connecting a cathode electrode to the negative terminal of a DC power supply. The alkaline environment promotes the dissociation and adsorption of weakly acidic substances. Solution flow refers to the interconnected liquid pathway between the anode chamber 2 and the cathode chamber 1 via pipes or flow-guiding structures. This can be achieved by gravity flow or pumping to drive the solution from the anode chamber 2 to the cathode chamber 1, enabling dynamic circulation of the solution between the chambers and preventing excessively high local ion concentrations.

[0056] Specifically, the acidic solution in anode chamber 2 flows into cathode chamber 1 under the drive of an electric field, where it mixes with the alkaline solution in cathode chamber 1. The hydrogen ions generated in anode chamber 2 neutralize the hydroxide ions generated in cathode chamber 1, reducing the risk of precipitation in cathode chamber 1.

[0057] Example 2:

[0058] Based on Example 1, such as Figure 3 As shown, there are multiple cation exchange modules 4 and multiple deionization modules 3, with the deionization modules 3 and cation exchange modules 4 arranged alternately. This alternating arrangement means that multiple cation exchange modules 4 and deionization modules 3 are arranged alternately, which can be achieved by setting up concentrate chambers 5 between adjacent modules. This technical solution can increase the number of cation exchange modules 4 and deionization modules 3, thereby increasing the water treatment capacity of the electro-deionization device.

[0059] This embodiment further proposes a one-to-one correspondence between the deion module 3 and the cation replacement module 4. The deion module 3 and the corresponding cation replacement module 4 are arranged adjacent to each other and form a set of purification components 8. In the set of purification components 8, the deion module 3 is located on the side closer to the cathode chamber 1 relative to the cation replacement module 4, and the cation replacement chamber 44, the deionized freshwater chamber 35 and the deionized freshwater chamber 34 are connected in sequence.

[0060] The purification component refers to an independent processing unit consisting of a deionization module 3 and a corresponding cation exchange module 4, with each component forming a complete ion exchange and separation path. Sequential connection means that the cation exchange chamber 44, the anion-deionized desalination chamber 35, and the cation-deionized desalination chamber 34 are connected in series via pipelines, allowing water to flow through each processing unit in a fixed order.

[0061] Specifically, the water to be treated first enters the cation exchange chamber 44 to complete the replacement of weakly alkaline cations, then enters the anion removal desalination chamber 35 to remove the original impurity anions and the anions dissociated from acidic gases in the water, and finally removes the residual impurity cations in the cation removal desalination chamber 34.

[0062] This solution utilizes a modular design to break down the treatment process into standardized units. Water undergoes three stages of purification within a single unit, shortening the migration path and reducing concentration gradient differences during ion exchange. The independent operation of each unit avoids ion interference between different modules, ensuring that weakly basic cations are fully removed during the replacement phase, reducing the risk of precipitation in subsequent treatments, and simplifying system maintenance and expansion operations. Using multiple units in parallel can increase the overall water treatment capacity of the electro-deionization unit.

[0063] Example 3:

[0064] Based on Example 1 or 2, such as Figure 4 and Figure 5 As shown, this application further proposes that at least one isolation module 7 is provided in the electro-deionization chamber. The side of the isolation module 7 near the cathode chamber 1 is the deionization module 3 and a first concentrate chamber 51 is provided between the two. The side of the isolation module 7 near the anode chamber 2 is the cation exchange module 4 and a second concentrate chamber 52 is provided between the two. The isolation module 7 includes a fourth cation exchange membrane 71 and a third anion exchange membrane 72 arranged sequentially and spaced apart from the cathode chamber 1 side to the anode chamber 2 side. An isolation chamber 73 is provided between the fourth cation exchange membrane 71 and the third anion exchange membrane 72. The isolation chamber 73 contains a strong acid and strong base salt solution, and the anions in the strong acid and strong base salt solution are nitrate ions and / or chloride ions.

[0065] Among them, the isolation module 7 refers to the independent chamber structure constructed by the fourth cation exchange membrane 71 and the third anion exchange membrane 72.

[0066] Specifically, the isolation module 7 physically isolates the operating environments of the deionization module 3 and the cation exchange module 4 through the synergistic effect of the fourth cation exchange membrane 71 and the third anion exchange membrane 72. Driven by an electric field, anions in the deionization desalination chamber 35 pass through the third anion exchange membrane 72 into the first concentrate chamber 51, while weakly basic cations in the cation exchange chamber 44 pass through the fourth cation exchange membrane 71 into the second concentrate chamber 52. The sodium nitrate or potassium chloride solution filled in the isolation chamber 73 allows nitrate or chloride ions to migrate to the second concentrate chamber 52 through the third anion exchange membrane 72. Since the salts formed by nitrate or chloride ions and weakly basic cations have extremely high solubility, the formation of calcium carbonate or calcium sulfate precipitates in the second concentrate chamber 52 can be effectively prevented. Simultaneously, sodium or potassium ions in the isolation chamber 73 migrate to the first concentrate chamber 51 through the fourth cation exchange membrane 71, forming easily soluble salts with the anions in the first concentrate chamber 51, further reducing the risk of precipitation in the first concentrate chamber 51.

[0067] This application further proposes that the supply chamber 73 be supplied with strong acid and strong base salt solutions.

[0068] The isolation chamber 73 in this application will only supply anions and cations to both sides, and will not allow other impurity ions to enter. During long-term operation, the ion concentration of the solution in the ion isolation chamber 73 will only decrease.

[0069] Specifically, the supply chamber forms a circulation loop with the isolation chamber 73 via a connecting pipe. The salt solution continuously flows into the isolation chamber 73 under gravity or pump drive, maintaining its internal salt concentration. When the salt solution concentration decreases due to ion migration or water dilution, the operator directly injects a high-concentration salt solution into the supply chamber through the addition port to compensate for the loss. Because the supply chamber is connected to both functional chambers, the newly added salt solution can be quickly and evenly distributed through circulation, avoiding localized excessively high or low concentrations. For example, during system operation, sodium ions in the ion supply chamber 45 may be gradually consumed by the displacement reaction, while nitrate ions in the isolation chamber 73 may decrease due to migration. In this case, replenishing with sodium nitrate solution through the addition port can simultaneously restore the salt concentration in both chambers.

[0070] Compared to existing technologies, traditional EDI systems typically require a separate storage tank for the isolation chamber 73, with each tank requiring separate replenishment of salt solution. This leads to complex maintenance and a tendency for uneven concentration. This solution, however, utilizes a single supply chamber for unified supply, combined with a circulating interconnection design. This not only reduces the frequency of manual intervention but also achieves automatic salt concentration balancing through dynamic circulation, significantly improving the continuity of system operation.

[0071] Through the above technical solution, this application achieves centralized supply and dynamic balance of salt solution in isolation chamber 73, solves the problem of concentration decay caused by inconvenience in salt solution replenishment in traditional technology, ensures the long-term stability of cation exchange efficiency and isolation function, and reduces the risk of operational errors caused by frequent feeding.

[0072] Example 4:

[0073] Based on Example 1, such as Figure 6 As shown, at least two cation exchange modules 4 are arranged adjacently to form a first exchange module group 40; the first exchange module group 40 is arranged adjacent to the deionization module 3 on the side near the cathode chamber 1, and a third concentrate chamber 53 is provided between them; a fourth concentrate chamber 54 is provided between two adjacent cation exchange modules 4 in the first exchange module group 40; the cation exchange chamber 44 adjacent to the third concentrate chamber 53 in the first exchange module group 40 is the first cation exchange chamber 441, and the cation exchange chamber 44 adjacent to the fourth concentrate chamber 54 is the second cation exchange chamber 442; in the first exchange module group 40, the water to be treated first flows through the second cation exchange chamber 442, and then flows into the first cation exchange chamber 441; the anions in the strong acid and strong base salt solution are nitrate ions and / or chloride ions.

[0074] Specifically, the water to be treated flows sequentially through the cation exchange chambers 44 of multiple cation exchange modules 4, where weakly alkaline cations are converted into strongly alkaline cations through multi-stage exchange. Subsequently, the water flows into the deionization chambers 35 and cation deionization chambers 34 of multiple deionization modules 3. The strong acid and strong base salt in the strong acid and strong base salt solution can be sodium nitrate, potassium nitrate, sodium chloride, or potassium chloride.

[0075] Through the above technical solution, the water to be treated first flows through the second cation exchange chamber 442. Under the drive of the electric field, the weakly basic cations in the second cation exchange chamber 442 migrate into the fourth concentrate chamber 54. The anions (nitrate ions or chloride ions) in the ion supply chamber 45 adjacent to the fourth concentrate chamber 54 also migrate into the fourth concentrate chamber 54. Since the salts formed by nitrate ions or chloride ions and weakly basic cations have extremely high solubility, the risk of precipitation in the fourth concentrate chamber 54 is reduced.

[0076] The water to be treated first flows through the second cation exchange chamber 442 and then into the first cation exchange chamber 441. Under the drive of the electric field, the cations in the first cation exchange chamber 441 migrate into the third concentrate chamber 53. Since the liquid entering the first cation exchange chamber 441 has already undergone one cation exchange in the second cation exchange chamber 442, the concentration of weakly alkaline cations in the liquid entering the first cation exchange chamber 441 is significantly reduced. The concentration of weakly alkaline cations entering the third concentrate chamber 53 from the first cation exchange chamber 441 is also significantly reduced. When the anions in the deionized deionized water chamber 35 in the deionization module 3 also enter the third concentrate chamber 53, the concentration of weakly alkaline cations in the third concentrate chamber 53 is low, and it is not easy to form a precipitate in the third concentrate chamber 53.

[0077] By using the above technical solution, the first replacement module group 40 is formed by connecting the three deionization modules in parallel, and the water to be treated first flows through the second cation replacement chamber 442 and then flows into the first cation replacement chamber 441. Under the premise of increasing the cation replacement effect, the risk of precipitation in the third concentrate chamber 53 and the fourth concentrate chamber 54 can also be reduced.

[0078] Example 5:

[0079] Based on Example 1, such as Figure 7 As shown, there are multiple cation exchange modules 4, and the cation exchange chambers 44 of the multiple cation exchange modules 4 are connected in sequence. There are multiple deion modules 3, and the deionization chambers 35 of the multiple deion modules 3 are connected in sequence. The deionization chambers 34 of the multiple deion modules 3 are connected in sequence. The water to be treated flows through the multiple cation exchange chambers 44, the multiple deionization chambers 35 and the multiple deionization chambers 34 in sequence.

[0080] The series connection of the cation exchange module 4 refers to multiple cation exchange chambers 44 being connected end-to-end through pipelines, allowing the water to be treated to pass through each cation exchange chamber 44 sequentially, gradually replacing weakly alkaline cations with strongly alkaline cations through multi-stage replacement. The series connection of the anion removal desalination chambers 35 refers to multiple anion removal desalination chambers 35 being connected in sequence, using an alkaline environment to promote the dissociation of acidic gases into acid radicals. The series connection of the cation removal desalination chambers 34 refers to multiple cation removal desalination chambers 34 being connected in sequence, removing residual strongly alkaline cations through multi-stage filtration.

[0081] Specifically, the water to be treated first enters a series of cation exchange chambers 44. In each chamber, weakly basic cations are gradually replaced by strongly basic cations, resulting in a significant reduction in calcium and magnesium ion concentrations after multiple stages of exchange. The water then flows into a series of anion removal chambers 35. In the alkaline environment generated by the bipolar membrane, dissolved carbon dioxide is converted into carbonate ions and passes through anion exchange membranes into the concentrate chamber 5. This multi-stage treatment enhances the removal of anions and acidic gases. Finally, the water flows through a series of cation removal chambers 34, where sodium or potassium ions are further removed via multi-stage cation exchange membranes. The series structure extends the water flow path and increases the impurity removal efficiency.

[0082] Through the above technical solutions, this application can achieve full replacement of weakly alkaline cations, reducing the risk of precipitation by combining with acid radicals in subsequent treatment; the multi-stage deionization desalination chamber 35 removes acidic gases in stages under alkaline conditions, improving the removal efficiency of pollutants such as carbon dioxide; the series structure optimizes the water flow path, avoiding the structural complexity of the concentrate chamber 5 caused by the parallel connection of multiple modules, and reducing the possibility of scaling.

[0083] Understandably, in another embodiment, one cation exchange module corresponds to multiple deionization modules, and one deionization module corresponds to multiple cation exchange modules.

[0084] Example 6:

[0085] like Figure 8 and Figure 9As shown, an electro-deionization device for ultrapure water preparation includes a housing and an electro-deionization chamber disposed within the housing. The electro-deionization chamber contains a cathode chamber 1 and an anode chamber 2. At least one cation exchange module 4 is disposed between the cathode chamber 1 and the anode chamber 2. At least one deionization module 3 is disposed between the cation exchange module 4 and the cathode chamber 1. At least one concentrate chamber 5 is disposed between the deionization module 3 and the cation exchange module 4. The deionization module 3 includes a first cation exchange membrane 31, a first bipolar membrane 32, and a first anion exchange membrane 33, sequentially spaced from the cathode chamber 1 side to the anode chamber 2 side. A deionized desalination chamber 34 is disposed between the first cation exchange membrane 31 and the first bipolar membrane 32. A deionization desalination chamber 35 is provided between membrane 32 and the first anion exchange membrane 33. The side of the bipolar membrane that generates hydroxide ions faces the deionization desalination chamber 35, and the side that generates hydrogen ions faces the deionization desalination chamber 34. The cation exchange module 4 includes a second cation exchange membrane 41 and a third cation exchange membrane 42 arranged sequentially from the cathode chamber 1 to the anode chamber 2. A cation exchange chamber 44 is provided between the second cation exchange membrane 41 and the third cation exchange membrane 42. The water to be treated flows sequentially through the cation exchange chamber 44, the deionization desalination chamber 35, and the deionization desalination chamber 34. A strong acid and strong base salt solution is provided in the chamber opposite to the cation exchange chamber 44 and located on the other side of the third cation exchange membrane 42.

[0086] The chamber located opposite the cation exchange chamber 44 and on the other side of the third cation exchange membrane 42 is named the first chamber. The first chamber refers to either the anode chamber 2 or the concentrate chamber 5 which is adjacent to the third cation exchange membrane 42 and located on the side closer to the anode chamber 2.

[0087] Specifically, the raw water first enters the cation exchange chamber 44, where weakly basic cations are replaced by strongly basic cations, formed by the second cation exchange membrane 41 and the third cation exchange membrane 42. The replaced water flows to the anion removal desalination chamber 35, where an alkaline environment is created by the hydroxide ions generated by the first bipolar membrane 32. This environment promotes the dissociation of acidic gases such as carbon dioxide into anions, which then pass through the anion exchange membrane into the concentrate chamber 5. The water then flows into the cation removal desalination chamber 34, where cations migrate and enter either the concentrate chamber 5 or the cathode chamber 1. The water produced by the cation removal desalination chamber 34 is ultrapure water. The first chamber continuously releases sodium or potassium ions, which replenish the cation exchange chamber 44 with the necessary cations through the third cation exchange membrane 42. The liquid in the cathode chamber 1 can be directly supplied to the raw water to be treated, and is discharged as wastewater after passing through the concentrate chamber 5, anode chamber 2, or cathode chamber 1.

[0088] Through the above technical solution, this application effectively reduces the residual concentration of acidic gases such as carbon dioxide in the product water, while inhibiting the formation of calcium and magnesium carbonate precipitates in the concentrate chamber 5 and the cathode chamber. The replaced sodium and potassium ions form highly soluble salts with the acid radicals, preventing scaling on the membrane surface and resin clogging. The alkaline environment regulated by the bipolar membrane promotes the complete dissociation of acidic gases, improving the adsorption efficiency of the anion exchange membrane for carbonate ions, ultimately achieving dual optimization of pollutant removal and stable system operation in the ultrapure water preparation process.

[0089] This application further proposes a supply chamber for supplying a strong acid-base salt solution to the first chamber. The supply chamber is connected to the first chamber and has an inlet. The supply chamber needs to be equipped with an exhaust port to discharge other gases generated in the anode chamber 2.

[0090] Preferably, the anion in the strong acid-strong base salt solution is nitrate ion. Nitrate ions can combine with weakly basic cations to form easily soluble salts, and they remain stable after entering the anode chamber, without producing toxic gases at the anode.

[0091] This application further proposes that the liquids in the cation exchange chamber 44 and the concentrate chamber 5 flow in opposite directions on both sides of the second cation exchange membrane 41. A second bipolar membrane 6 is provided on the second cation exchange membrane 41 near the outlet end of the cation exchange chamber 44. The outlet end of the cation exchange chamber 44 and the inlet end of the concentrate chamber 5 are separated by the second bipolar membrane 6. The side of the second bipolar membrane 6 that generates hydroxide ions faces the cation exchange chamber 44, and the side that generates hydrogen ions faces the concentrate chamber 5.

[0092] Specifically, when the liquid flows through the inlet of the concentrate chamber 5, hydrogen ions released by the second bipolar membrane 6 enter the concentrate chamber 5, increasing the hydrogen ion concentration and decreasing the pH value of the concentrate chamber 5. This inhibits the dissociation of acid radicals, thereby reducing the risk of precipitation caused by the combination of weakly basic cations and acid radicals, ensuring the membrane flux and ion exchange efficiency of the electro-deionization device during long-term operation. The second bipolar membrane 6 is located near the outlet of the cation exchange chamber 44. When the solution that has completed cation exchange in the cation exchange chamber 44 flows out through the outlet, a large amount of weakly basic cations have been replaced, and the content has decreased significantly. Even if the hydroxide ions released by the second bipolar membrane 6 enter this area, it is not easy for the liquid to precipitate. Furthermore, the hydroxide ions released by the second bipolar membrane 6 can also increase the alkalinity of the liquid flowing out of the cation exchange chamber 44. After flowing out of this area, the liquid enters the deionization desalination chamber 35. The hydroxide ions released by the second bipolar membrane 6 help dissociate the acidic gas in the deionization desalination chamber 35 into anions.

Claims

1. An electro-deionization device for ultrapure water preparation, comprising a housing and an electro-deionization chamber disposed within the housing, the electro-deionization chamber comprising a cathode chamber and an anode chamber, characterized in that, At least one cation exchange module is provided between the cathode chamber and the anode chamber, at least one deionization module is provided between the cation exchange module and the cathode chamber, and at least one concentrate chamber is provided between the deionization module and the cation exchange module. The deionization module includes a first cation exchange membrane, a first bipolar membrane, and a first anion exchange membrane arranged sequentially from the cathode chamber side to the anode chamber side. A deionization desalination chamber is provided between the first cation exchange membrane and the first bipolar membrane, and a deionization desalination chamber is provided between the first bipolar membrane and the first anion exchange membrane. The cation exchange module includes a second cation exchange membrane, a third cation exchange membrane, and a second anion exchange membrane arranged sequentially from the cathode chamber side to the anode chamber side. A cation exchange chamber is provided between the second cation exchange membrane and the third cation exchange membrane, and an ion supply chamber is provided between the third cation exchange membrane and the second anion exchange membrane. The water to be treated flows sequentially through the cation exchange chamber, the deionization desalination chamber, and the deionization desalination chamber. The ion supply chamber contains a strong acid and strong base salt solution.

2. The electro-deionization device for ultrapure water preparation according to claim 1, characterized in that, The number of cation exchange modules is multiple, and the number of deion modules is multiple, with the deion modules and cation exchange modules arranged alternately.

3. The electro-deionization device for ultrapure water preparation according to claim 2, characterized in that, The deionization module and the cation replacement module are one-to-one. The deionization module and the corresponding cation replacement module are arranged adjacent to each other and form a set of purification components. In the set of purification components, the deionization module is located on the side closer to the cathode chamber relative to the cation replacement module, and the cation replacement chamber, the deionized anion freshwater chamber and the deionized cation freshwater chamber are connected in sequence.

4. The electro-deionization device for ultrapure water preparation according to claim 1, characterized in that, At least two cation exchange modules are arranged adjacently to form a first exchange module group; the side of the first exchange module group closest to the cathode chamber is adjacent to the deionization module and a third concentrate chamber is provided between them; a fourth concentrate chamber is provided between two adjacent cation exchange modules in the first exchange module group; the cation exchange chamber adjacent to the third concentrate chamber in the first exchange module group is the first cation exchange chamber, and the cation exchange chamber adjacent to the fourth concentrate chamber is the second cation exchange chamber; in the first exchange module group, the water to be treated first flows through the second cation exchange chamber and then flows into the first cation exchange chamber; the anions in the strong acid and strong base salt solution are nitrate ions and / or chloride ions.

5. The electro-deionization device for ultrapure water preparation according to claim 1, characterized in that, The number of cation exchange modules is multiple, and the cation exchange chambers of the multiple cation exchange modules are connected in sequence. The number of deion modules is multiple, and the deionization desalination chambers of the multiple deion modules are connected in sequence. The deionization desalination chambers of the multiple deion modules are connected in sequence. The water to be treated flows through the multiple cation exchange chambers, the multiple deionization desalination chambers and the multiple deionization desalination chambers in sequence.

6. The electro-deionization device for ultrapure water preparation according to claim 1, characterized in that, The liquid flows in opposite directions in the cation exchange chamber and the concentrate chamber on both sides of the second cation exchange membrane. A second bipolar membrane is provided near the outlet of the cation exchange chamber. The outlet of the cation exchange chamber and the inlet of the concentrate chamber are separated by the second bipolar membrane. The side of the second bipolar membrane that generates hydroxide ions faces the cation exchange chamber, and the side of the second bipolar membrane that generates hydrogen ions faces the concentrate chamber.

7. The electro-deionization device for ultrapure water preparation according to claim 1, characterized in that, The cathode chamber is located adjacent to the deionized water chamber, and the anode chamber is located adjacent to the ion supply chamber; the liquid in the anode chamber flows into the cathode chamber.

8. An electro-deionization device for ultrapure water preparation, comprising a housing and an electro-deionization chamber disposed within the housing, the electro-deionization chamber comprising a cathode chamber and an anode chamber, characterized in that, At least one cation exchange module is provided between the cathode chamber and the anode chamber, at least one deionization module is provided between the cation exchange module and the cathode chamber, and at least one concentrate chamber is provided between the deionization module and the cation exchange module. The deionization module includes a first cation exchange membrane, a first bipolar membrane, and a first anion exchange membrane arranged sequentially and spaced apart from the cathode chamber side to the anode chamber side. A deionization desalination chamber is provided between the first cation exchange membrane and the first bipolar membrane, and a deionization desalination chamber is provided between the first bipolar membrane and the first anion exchange membrane. The cation exchange module includes a second cation exchange membrane and a third cation exchange membrane arranged sequentially and spaced apart from the cathode chamber side to the anode chamber side. A cation exchange chamber is provided between the second cation exchange membrane and the third cation exchange membrane. The water to be treated flows sequentially through the cation exchange chamber, the deionization desalination chamber, and the deionization desalination chamber. A strong acid and strong base salt solution is provided in the chamber opposite to the cation exchange chamber and located on the other side of the third cation exchange membrane.

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