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

Abstract

Provided is an electrodialysis system that can prevent scale from hardness components and silica and can effectively perform deionization treatment in the treatment of a treated liquid having a pH of 3 or less or 12 or more. An electrodialysis system includes an electrodialysis device having at least an anode, a cathode, a first bipolar membrane, an ion exchange membrane, and a second bipolar membrane, the first bipolar membrane, the ion exchange membrane, and the second bipolar membrane being arranged in this order from the anode side between the anode and the cathode; and a pH measurement unit that measures the pH of a treated liquid obtained after the treated liquid passes through the electrodialysis device, the electrodialysis treatment by the electrodialysis device being ended when the pH of the treated liquid measured by the pH measurement unit reaches a given value.

Description

Technical Field

[0001] This invention relates to an electrodialysis system, an electrodialysis method, a waste liquid treatment system, and a waste liquid treatment method. Background Technology

[0002] Ion exchangers are used for various applications; for example, they are used as ion removal materials in pure water production plants. Cation exchangers adsorb cationic components, and when their adsorption capacity decreases, it is restored by regenerating the cation exchanger with acid. During regeneration, an excess of acid is typically used, exceeding the exchange capacity of the cation exchanger, resulting in excess acid in the regeneration waste liquid. Similarly, anion exchangers adsorb anionic components, and when their adsorption performance decreases, it is restored by regenerating the anion exchanger with alkali. Again, during the regeneration of anion exchangers, an excess of alkali is used, exceeding the exchange capacity of the anion exchanger, resulting in excess alkali in the regeneration waste liquid.

[0003] These recycled waste liquids are usually neutralized after mixing for treatment, but due to the excessive addition of acid or alkali, further acid or alkali is needed for neutralization, which raises the issues of increased chemical usage and increased salt concentration in the waste liquid.

[0004] Therefore, a method was proposed to recover acids and alkalis by electrolyzing these recycled waste liquids through electrodialysis.

[0005] For example, Patent Document 1 proposes the following method: after mixing the regeneration waste liquids of the cation exchange tower and the anion exchange tower, the acid and alkali are recovered using an electrodialysis device equipped with a bipolar membrane, and the recovered acid and alkali are then used for the regeneration of the resin tower.

[0006] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 9-122643 Summary of the Invention The technical problem that the invention aims to solve In the method described in Patent Document 1, an ion exchange membrane is used to separate Na from the regeneration waste liquid. + and Cl - They were then supplied with H2O, which was produced by the splitting of water through a bipolar membrane. + and OH - This produces acids or bases, namely NaOH and HCl. At this point, if the reaction continues... + and Cl - The separation process is problematic because the ion concentration in the supply solution gradually decreases, making it difficult for current to flow, thus requiring a relatively long time for separation.

[0007] In addition, this method has the following problem: the Ca in the acidic regeneration waste liquid...2+ Mg 2+ Scale forms as OH⁻ is supplied to the cation exchange membrane, creating an alkaline environment. Alternatively, H⁻ can be supplied to the alkaline regeneration wastewater. + This leads to a decrease in pH, which in turn generates silica scale.

[0008] Furthermore, in cases where only one of the waste acid or waste alkali needs to be reused, i.e., only one of the waste acid or waste alkali has a use, if the Na in the waste liquid is removed... + and Cl - Electrolysis of these two substances produces NaOH and HCl, and one of them will be discarded, thus increasing the cost of disposal.

[0009] The purpose of this invention is to provide an electrodialysis system, an electrodialysis method, a waste liquid treatment system, and a waste liquid treatment method that can prevent the formation of scale from hardness components and silica, and can effectively perform deionization treatment.

[0010] Technical solutions for solving technical problems The inventors conducted in-depth research on the above-mentioned technical problems and found that by ending electrodialysis at the moment when the pH of the treatment solution reaches a given value, the above-mentioned technical problems can be solved, thus completing the present invention.

[0011] The present invention includes the following methods.

[0012] [1] An electrodialysis system for treating a liquid with a pH below 3 or a pH above 12, wherein the electrodialysis system comprises: An electrodialysis apparatus comprising at least an anode, a cathode, a first bipolar membrane, an ion exchange membrane, and a second bipolar membrane, wherein the first bipolar membrane, the ion exchange membrane, and the second bipolar membrane are sequentially disposed between the anode and the cathode, starting from the anode side; and The pH measuring unit measures the pH of the treated solution obtained after the treated solution passes through the electrodialysis device. When the pH value of the treated solution, as measured by the pH measuring unit, reaches a given value, the electrodialysis treatment performed by the electrodialysis apparatus is terminated.

[0013] [2] According to the electrodialysis system described in [1], the liquid to be treated is a liquid with a pH of less than 3, and the ion exchange membrane of the electrodialysis device is an anion exchange membrane.

[0014] [3] According to the electrodialysis system described in [1], the liquid to be treated is a liquid with a pH of 12 or higher, and the ion exchange membrane of the electrodialysis device is a cation exchange membrane.

[0015] [4] According to the electrodialysis system described in [1], the ion exchange membrane of the electrodialysis device is an anion exchange membrane, and a cation exchange membrane is provided between the anion exchange membrane and the second bipolar membrane.

[0016] [5] According to the electrodialysis system described in [2], the electrodialysis apparatus is equipped with: The anode chamber, defined by the aforementioned anode and the aforementioned first bipolar film; and The cathode chamber is defined by the aforementioned cathode and the aforementioned second bipolar film. The above-mentioned electrodialysis device includes: An acid recovery chamber, located between the anode chamber and the cathode chamber, is demarcated by the first bipolar membrane and the anion exchange membrane. Water is supplied to the chamber and treated by electrodialysis to generate a recovered acid solution. The deionization chamber, defined by the aforementioned anion exchange membrane and the second bipolar membrane, is supplied with an acid feed solution as the treated liquid, which is then treated by electrodialysis to generate deionized water. The unit group consisting of the above-mentioned acid recovery chamber and the above-mentioned deionization chamber may be configured with one or more repeated configurations.

[0017] [6] According to the electrodialysis system described in [3], the electrodialysis apparatus is equipped with: The anode chamber, defined by the aforementioned anode and the aforementioned first bipolar film; and The cathode chamber is defined by the aforementioned cathode and the aforementioned second bipolar film. The aforementioned electrodialysis apparatus comprises: a deionization chamber, located between the anode chamber and the cathode chamber, defined by the first bipolar membrane and the cation exchange membrane, wherein an alkaline feed solution is supplied as the treated liquid and deionized water is generated through electrodialysis; and The alkali recovery chamber, defined by the aforementioned cation exchange membrane and the second bipolar membrane, is supplied with water and treated by electrodialysis to generate a recovered alkali solution. The unit group consisting of the above-mentioned deionization chamber and the above-mentioned alkali recovery chamber may be configured with one or more repeated configurations.

[0018] [7] According to the electrodialysis system described in [4], the electrodialysis apparatus is equipped with: The anode chamber, defined by the aforementioned anode and the aforementioned first bipolar film; and The cathode chamber is defined by the aforementioned cathode and the aforementioned second bipolar film. The aforementioned electrodialysis system includes: an alkali recovery chamber located between the anode chamber and the cathode chamber, defined by the cation exchange membrane and the second bipolar membrane, wherein water is supplied and the alkali solution is generated through electrodialysis treatment; An acid recovery chamber, defined by the aforementioned anion exchange membrane and the aforementioned first bipolar membrane, is supplied with water and treated by electrodialysis to generate a recovered acid solution; and The deionization chamber, defined by the aforementioned cation exchange membrane and anion exchange membrane, is supplied with the solution to be treated and deionized water is generated through electrodialysis. The unit group consisting of the above-mentioned acid recovery chamber, the above-mentioned deionization chamber and the above-mentioned alkali recovery chamber may be configured with one or more repeated configurations.

[0019] [8] According to the electrodialysis system described in [2] or [4], wherein the pH of the solution being treated is less than 1, When the pH of the above-mentioned treatment solution reaches a range of 1 or higher and 3 or lower, the electrodialysis treatment performed by the above-mentioned electrodialysis device is terminated.

[0020] [9] According to the electrodialysis system described in [3] or [4], wherein the pH of the solution being treated is 12 or higher. The electrodialysis treatment performed by the above-mentioned electrodialysis device shall be terminated before the pH of the above-mentioned treatment solution reaches a range of less than 9.

[0021]

[10] An electrodialysis system according to any one of [1] to [7], wherein the liquid being treated is the regeneration waste liquid of an ion exchange device.

[0022]

[11] An electrodialysis system according to any one of [5] to [7], wherein the above-mentioned recovered acid or the above-mentioned recovered alkali is used in a water treatment system different from the water treatment system that discharges the above-mentioned treated liquid.

[0023]

[12] A waste liquid treatment system comprising: an ion exchange device filled with an ion exchanger; A regenerated liquid supply device that supplies the regenerated liquid of the ion exchanger to the aforementioned ion exchange device; and An electrodialysis system that treats the regeneration waste liquid discharged from the aforementioned ion exchange unit. The aforementioned regenerated wastewater has a pH below 3 or a pH above 12. The above-mentioned electrodialysis system has the following features: An electrodialysis apparatus comprising at least an anode, a cathode, a first bipolar membrane, an ion exchange membrane, and a second bipolar membrane, wherein the first bipolar membrane, the ion exchange membrane, and the second bipolar membrane are sequentially arranged between the anode and the cathode, starting from the anode side; and The pH measuring unit measures the pH of the treated liquid obtained after the above-mentioned regenerated waste liquid passes through the above-mentioned electrodialysis device. When the pH value of the treated solution, as measured by the pH measuring unit, reaches a given value, the electrodialysis treatment performed by the electrodialysis apparatus is terminated.

[0024]

[13] An electrodialysis method for treating a liquid with a pH below 3 or a pH above 12. In the above-mentioned electrodialysis methods, Electrodialysis is performed using an electrodialysis apparatus, which has at least an anode, a cathode, a first bipolar membrane, an ion exchange membrane, and a second bipolar membrane. The first bipolar membrane, the ion exchange membrane, and the second bipolar membrane are arranged sequentially between the anode and the cathode, starting from the anode side. The pH of the treated solution obtained after the above-mentioned treated solution has passed through the above-mentioned electrodialysis device was measured; When the pH value of the above-mentioned treatment solution reaches a given value, the electrodialysis treatment performed by the above-mentioned electrodialysis device is terminated.

[0025]

[14] A waste liquid treatment method, comprising: The regenerant supply process supplies the regenerant of the ion exchanger to an ion exchange apparatus filled with the ion exchanger; and The electrodialysis process treats the regenerated waste liquid discharged from the aforementioned ion exchange unit. The above-mentioned regenerated wastewater has a pH below 3 or a pH above 12. The above-mentioned electrodialysis process includes the following steps: The aforementioned regenerated waste liquid is introduced into an electrodialysis apparatus for electrodialysis treatment. The electrodialysis apparatus includes at least an anode, a cathode, a first bipolar membrane, an ion exchange membrane, and a second bipolar membrane. The first bipolar membrane, the ion exchange membrane, and the second bipolar membrane are sequentially arranged between the anode and the cathode, starting from the anode side. The pH of the treated liquid obtained after the above-mentioned regenerated waste liquid passes through the above-mentioned electrodialysis device was measured. When the pH value of the above-mentioned treatment solution reaches a given value during the pH measurement process, the electrodialysis treatment performed by the above-mentioned electrodialysis apparatus is terminated.

[0026] Invention Effects According to the present invention, an electrodialysis system, an electrodialysis method, a waste liquid treatment system, and a waste liquid treatment method can be provided, which can prevent the formation of scale from hardness components and silica, and can also effectively perform deionization treatment. Attached Figure Description

[0027] Figure 1 This is a schematic structural diagram illustrating the electrodialysis apparatus used in the electrodialysis system according to embodiments of the present invention.

[0028] Figure 2This is a schematic structural diagram illustrating the electrodialysis apparatus used in an electrodialysis system according to other embodiments of the present invention.

[0029] Figure 3 This is a schematic structural diagram illustrating the electrodialysis apparatus used in an electrodialysis system according to other embodiments of the present invention.

[0030] Figure 4 This is a schematic structural diagram illustrating the electrodialysis apparatus used in an electrodialysis system according to other embodiments of the present invention.

[0031] Figure 5 This is a schematic diagram illustrating a wastewater treatment system for the regeneration wastewater of a cation exchanger according to other embodiments of the present invention.

[0032] Figure 6 This is a schematic diagram illustrating a wastewater treatment system for the regeneration wastewater of anion exchangers according to other embodiments of the present invention.

[0033] Figure 7 This is a graph showing the relationship between the operating time of the electrodialysis device in Example 1 and the pH of the treatment solution.

[0034] Figure 8 This is a graph showing the relationship between the operating time and current of the electrodialysis device in Example 1.

[0035] Figure 9 This is a graph showing the relationship between the operating time of the electrodialysis device in Example 2 and the pH of the treatment solution.

[0036] Figure 10 This is a graph showing the relationship between the operating time and current of the electrodialysis device in Example 2. Detailed Implementation

[0037] According to an embodiment of the present invention, in the electrodialysis of a treated liquid with a pH below 3 or a pH above 12, a specific electrodialysis apparatus is used to terminate the electrodialysis when the pH of the treated liquid reaches a given value, thereby preventing scale formation and achieving effective deionization. In this electrodialysis, an electrodialysis apparatus is used, which has at least an anode, a cathode, a first bipolar membrane, an ion exchange membrane, and a second bipolar membrane. The first bipolar membrane, the ion exchange membrane, and the second bipolar membrane are sequentially arranged between the anode and the cathode, starting from the anode side.

[0038] In the case of the treated liquid, such as caustic soda regeneration waste liquid, the OH- present in the treated liquid can be removed. - and with OH - Equivalent Na +It is separated and recovered as NaOH. In the case of the treated liquid, such as acidic waste liquid containing hydrochloric acid, it is possible to remove H₂ present in the treated liquid during electrodialysis. + and H + Equivalent Cl - It is separated and recovered as HCl.

[0039] Furthermore, by minimizing the separation of components that exist as neutral salts when considered as compounds—such as SO4— 2- Other anions and their equivalent amounts of Na⁺; other cations such as Ca²⁺ and Mg²⁺ and their equivalent amounts of Cl⁺ - This helps prevent the formation of scale from hardness components like silica.

[0040] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings, but the present invention is not limited to these embodiments and the structure of the drawings.

[0041] (Electrodialysis system and electrodialysis method) like Figure 1 As shown, the electrodialysis apparatus 100 used in the electrodialysis system / method according to embodiments of the present invention includes at least an anode 1, a cathode 11, a bipolar membrane 3 (hereinafter also referred to as "BPM") (BPM3), an ion exchange membrane 5, and a bipolar membrane 9 (BPM9), wherein BPM3, ion exchange membrane 5, and BPM9 are arranged sequentially from the anode 1 side between the anode 1 and the cathode 11. The electrodialysis apparatus 100 includes: an anode chamber 20 defined by the anode 1 and BPM3; an acid recovery chamber 22 defined by the BPM3 and ion exchange membrane 5; a deionization chamber 24 defined by the ion exchange membrane 5 and BPM9; and a cathode chamber 34 defined by the bipolar membrane 9 and the cathode 11.

[0042] Here, bipolar membranes 3 and 9 are membranes that integrate cation exchange membranes and anion exchange membranes, typically having a structure in which the cation exchange membrane and anion exchange membrane overlap. Furthermore, the bipolar membranes are configured such that the interface between the overlapping cation exchange membrane and anion exchange membrane is optimal for water dissociation reactions, facilitating these reactions. For this purpose, substances with catalytic activity for water dissociation (e.g., heavy metal ions, tertiary amines, etc.) are typically introduced into the interface formed by overlapping the separate ion exchange membranes. Additionally, the bipolar membranes are configured with the anion exchange membrane side as the anode side and the cation exchange membrane side as the cathode side.

[0043] In addition, bipolar membranes 3 and 9 can be any membrane that is effective in water dissociation, not just membranes for sale as products, as long as they are structures formed by overlapping cation exchange membranes and anion exchange membranes.

[0044] The material of the ion exchange membrane 5 used in the electrodialysis apparatus 100 of the electrodialysis system according to the embodiments of the present invention is not particularly limited. Known materials can be used appropriately, and a membrane that is effective in separating the target ions can be selected. For example, a homogeneous membrane formed by coating a paste containing styrene and divinylbenzene with polyvinyl chloride, heating it, and then introducing the exchange groups can be provided; a heterogeneous membrane formed by molding ion exchange resin powder using a suitable film-forming adhesive, such as polyethylene, polystyrene, phenolic resin, synthetic rubber, etc.

[0045] The anode 1 and cathode 11 can be electrodes used in electrochemical industries such as water electrolysis, and such electrodes can be used without any restrictions. Examples of electrodes that can be used for the anode 1 and cathode 11 include nickel electrodes, titanium-based platinum-plated electrodes, and stainless steel electrodes.

[0046] The anode chamber 20 and the cathode chamber 34 are each filled with an electrode solution. Examples of electrode solutions include sodium hydroxide solution, sodium sulfate solution, and pure water.

[0047] Here, the anode chamber 20 houses the anode 1, and an acid recovery chamber 22 is provided adjacent to the anode chamber 20 via a BPM3. In addition, the cathode chamber 34 houses the cathode 11, and a deionization chamber 24 is provided adjacent to the cathode chamber 34 via a BPM9.

[0048] In the above structure, the anode chamber 20 and the acid recovery chamber 22 are separated by a BPM3, and the acid recovery chamber 22 and the deionization chamber 24 are separated by an ion exchange membrane 5. Furthermore, the deionization chamber 24 and the cathode chamber 34 are separated by a BPM9. That is, Figure 1 The electrodialysis apparatus 100 shown is a two-chamber electrodialysis apparatus, wherein BPM3, ion exchange membrane 5 and BPM9 are arranged sequentially from the anode 1 side, and the apparatus is mainly composed of two chambers: acid recovery chamber 22 and deionization chamber 24.

[0049] It should be noted that an anion exchange membrane (hereinafter sometimes referred to as "AEM") is used as ion exchange membrane 5. The following explains the use of an anion exchange membrane as ion exchange membrane 5.

[0050] Here, if we represent the chambers constituting the electrodialysis apparatus 100 sequentially from the anode 1 side, it becomes anode-anode chamber-(acid recovery chamber-deionization chamber) n-cathode chamber-cathode. Here, the smallest repeating unit composed of "acid recovery chamber-deionization chamber" within the parentheses is taken as the basic structure (i.e., a unit group), and n (n is an integer greater than or equal to 1) is the number of repeating layers in the unit group. It should be noted that in... Figure 1 The structure represents n=1.

[0051] The number of repetitions in a unit group can usually be set to the range of n = 1 to 500, preferably the range of 1 to 200.

[0052] If we represent the membranes constituting the electrodialysis apparatus 100 sequentially from the anode side, it becomes anode-(BPM-AEM)n-BPM-cathode. Here, n (where n is an integer greater than or equal to 1) is also the number of repeated layers in the unit group. It should be noted that in Figure 1 The structure for n=1 is shown in the figure.

[0053] exist Figure 1 In the electrodialysis apparatus 100 used in the illustrated embodiment of the present invention, water (e.g., pure water) is supplied to the acid recovery chamber 22, and treated water (acid supply solution) is supplied to the deionization chamber 24 for electrodialysis treatment. The water supplied to the acid recovery chamber 22 passes through the acid recovery chamber 22 and is discharged as recovered acid solution. The treated water supplied to the deionization chamber 24 passes through the deionization chamber 24 and is discharged as deionized water.

[0054] like Figure 2 As shown, the electrodialysis apparatus 200 used in the electrodialysis system / method according to embodiments of the present invention has at least an anode 1, a cathode 11, a BPM3, an ion exchange membrane 5, and a BPM9. Between the anode 1 and the cathode 11, the BPM3, ion exchange membrane 5, and BPM9 are arranged sequentially from the anode 1 side. The electrodialysis apparatus 200 includes: an anode chamber 20 defined by the anode 1 and the BPM3; a deionization chamber 30 defined by the BPM3 and the ion exchange membrane 5; an alkali recovery chamber 32 defined by the ion exchange membrane 5 and the BPM9; and a cathode chamber 34 defined by the BPM9 and the cathode 11.

[0055] Here, the anode chamber 20 houses the anode 1, and a deionization chamber 30 is provided adjacent to the anode chamber 20 via a BPM3. In addition, the cathode chamber 34 houses the cathode 11, and an alkali recovery chamber 32 is provided adjacent to the cathode chamber 34 via a BPM9.

[0056] In the above structure, the anode chamber 20 and the deionization chamber 30 are separated by a BPM3, and the deionization chamber 30 and the alkali recovery chamber 32 are separated by an ion exchange membrane 5. Furthermore, the alkali recovery chamber 32 and the cathode chamber 34 are separated by a BPM9. That is, Figure 2 The electrodialysis apparatus 200 shown is a two-chamber electrodialysis apparatus, wherein BPM3, ion exchange membrane 5 and BPM9 are arranged sequentially from the anode 1 side, and it is mainly composed of two chambers: deionization chamber 30 and alkali recovery chamber 32.

[0057] It should be noted that a cation exchange membrane (hereinafter also referred to as "CEM") is used as ion exchange membrane 5. The following explains the use of a cation exchange membrane as ion exchange membrane 5.

[0058] Here, if we represent the chambers constituting the electrodialysis apparatus 200 sequentially from the anode side, it becomes: anode-anode chamber-(deionization chamber-alkali recovery chamber)n-cathode chamber-cathode. Here, the smallest repeating unit within the brackets "deionization chamber-alkali recovery chamber" is taken as the basic structure (i.e., a unit group), and n (where n is an integer greater than or equal to 1) is the number of repeating layers in the unit group. It should be noted that in... Figure 2 The structure represents n=1.

[0059] If we represent the membranes constituting the electrodialysis device 200 sequentially from the anode side, it becomes anode-BPM-(CEM-BPM)n-cathode. Here, n (where n is an integer greater than or equal to 1) is also the number of repeated layers in the unit group. It should be noted that in Figure 2 The structure for n=1 is shown in the figure.

[0060] exist Figure 2 In the structure shown, the number of repeated layers of the unit group can usually be set to the range of n = 1 to 500, preferably the range of 1 to 200.

[0061] exist Figure 2 In the electrodialysis apparatus 200 used in the illustrated embodiment of the present invention, water to be treated (alkali supply solution) is supplied to the deionization chamber 30, and water (e.g., pure water) is supplied to the alkali recovery chamber 32 for electrodialysis treatment. The alkali supply solution supplied to the deionization chamber 30 is discharged as deionized water through the deionization chamber 30. The water supplied to the alkali recovery chamber 32 is discharged as recovered alkali solution through the alkali recovery chamber 32.

[0062] like Figure 3 As shown, the electrodialysis apparatus 300 used in the electrodialysis system / method according to the embodiments of the present invention has at least an anode 1, a cathode 11, a BPM3, an AEM5, a CEM7, and a BPM9. Between the anode 1 and the cathode 11, the BPM3, AEM5, CEM7, and BPM9 are arranged sequentially from the anode 1 side.

[0063] The electrodialysis apparatus 300 includes: an anode chamber 20 defined by anode 1 and BPM3; an acid recovery chamber 22 defined by BPM3 and AEM5; a deionization chamber 24 defined by AEM5 and CEM7; an alkali recovery chamber 32 defined by CEM7 and BPM9; and a cathode chamber 34 defined by BPM9 and cathode 11.

[0064] Here, the anode chamber 20 houses the anode 1 and is provided with an acid recovery chamber 22 adjacent to the anode chamber 20 via a BPM3. In addition, the cathode chamber 34 houses the cathode 11 and is provided with an alkali recovery chamber 32 adjacent to the cathode chamber 34 via a BPM9.

[0065] In the above structure, the anode chamber 20 and the acid recovery chamber 22 are separated by BPM3, the acid recovery chamber 22 and the deionization chamber 24 are separated by AEM5, and the deionization chamber 24 and the alkali recovery chamber 32 are separated by CEM7. Furthermore, the alkali recovery chamber 32 and the cathode chamber 34 are separated by BPM9. That is, Figure 3 The electrodialysis apparatus shown is a three-chamber electrodialysis apparatus, in which BPM3, AEM5, CEM7 and BPM9 are arranged sequentially from the anode 1 side, and the acid recovery chamber 22, deionization chamber 24 and alkali recovery chamber 32 are the main components.

[0066] Here, if we represent the chambers constituting the electrodialysis apparatus 300 sequentially from the anode side, it becomes: anode-anode chamber-(acid recovery chamber-deionization chamber-alkali recovery chamber)n-cathode chamber-cathode. Here, the smallest repeating unit within the brackets "acid recovery chamber-deionization chamber-alkali recovery chamber" is taken as the basic structure (i.e., a unit group), and n (where n is an integer greater than or equal to 1) is the number of repeating layers in the unit group. It should be noted that in... Figure 3 The structure represents n=1.

[0067] exist Figure 3 In the structure shown, the number of repeated layers of the unit group can usually be set to the range of n = 1 to 500, preferably the range of 1 to 200.

[0068] If we represent the membranes constituting the electrodialysis apparatus 300 sequentially from the anode side, it becomes anode-BPM-(AEM-CEM-BPM)n-cathode. Here, n (where n is an integer greater than or equal to 1) is also the number of repeated layers in the unit group. It should be noted that in Figure 3 The structure for n=1 is shown in the figure.

[0069] exist Figure 3 In the electrodialysis apparatus 300 used in the illustrated embodiment of the present invention, treated water (acid supply solution) is supplied to the deionization chamber 24, and water (e.g., pure water) is supplied to the acid recovery chamber 22 and the alkali recovery chamber 32 for electrodialysis treatment. The treated water supplied to the deionization chamber 24 passes through the deionization chamber 24 and is discharged as deionized water. The water supplied to the acid recovery chamber 22 passes through the acid recovery chamber 22 and is discharged as recovered acid solution. The water supplied to the alkali recovery chamber 32 passes through the alkali recovery chamber 32 and is discharged as recovered alkali solution.

[0070] like Figure 4 As shown, the electrodialysis apparatus 400 used in the electrodialysis system / method according to the embodiments of the present invention has at least an anode 1, a cathode 11, a BPM3, an AEM5, a CEM7, and a BPM9. Between the anode 1 and the cathode 11, the BPM3, AEM5, CEM7, and BPM9 are arranged sequentially from the anode 1 side.

[0071] The electrodialysis apparatus 400 includes: an anode chamber 20 defined by anode 1 and BPM3; an acid recovery chamber 22 defined by BPM3 and AEM5; a deionization chamber 30 defined by AEM5 and CEM7; an alkali recovery chamber 32 defined by CEM7 and BPM9; and a cathode chamber 34 defined by BPM9 and cathode 11.

[0072] Here, the anode chamber 20 houses the anode 1 and is provided with an acid recovery chamber 22 adjacent to the anode chamber 20 via a BPM3. In addition, the cathode chamber 34 houses the cathode 11 and is provided with an alkali recovery chamber 32 adjacent to the cathode chamber 34 via a BPM9.

[0073] In the above structure, the anode chamber 20 and the acid recovery chamber 22 are separated by BPM3, the acid recovery chamber 22 and the deionization chamber 30 are separated by AEM5, and the deionization chamber 30 and the alkali recovery chamber 32 are separated by CEM7. Furthermore, the alkali recovery chamber 32 and the cathode chamber 34 are separated by BPM9. That is, Figure 4 The electrodialysis apparatus shown is a three-chamber electrodialysis apparatus, in which BPM3, AEM5, CEM7 and BPM9 are arranged sequentially from the anode 1 side, and the acid recovery chamber 22, deionization chamber 30 and alkali recovery chamber 32 are the main components.

[0074] Here, if we represent the chambers constituting the electrodialysis apparatus 400 sequentially from the anode side, it becomes: anode-anode chamber-(acid recovery chamber-deionization chamber-alkali recovery chamber)n-cathode chamber-cathode. Here, the smallest repeating unit within the brackets "acid recovery chamber-deionization chamber-alkali recovery chamber" is taken as the basic structure (i.e., a unit group), and n (where n is an integer greater than or equal to 1) is the number of repeating layers in the unit group. It should be noted that in... Figure 4 The structure represents n=1.

[0075] exist Figure 4 In the structure shown, the number of repeated layers of the unit group can usually be set to the range of n = 1 to 500, preferably the range of 1 to 200.

[0076] If we represent the membranes constituting the electrodialysis device 400 sequentially from the anode side, it becomes anode-BPM-(AEM-CEM-BPM)n-cathode. Here, n (where n is an integer greater than or equal to 1) is also the number of repeated layers in the unit group. It should be noted that in Figure 4 The structure for n=1 is shown in the figure.

[0077] exist Figure 4In the electrodialysis apparatus 400 used in the illustrated embodiment of the present invention, treated water (alkali supply solution) is supplied to the deionization chamber 30, and water (e.g., pure water) is supplied to the acid recovery chamber 22 and the alkali recovery chamber 32 for electrodialysis treatment. The treated water supplied to the deionization chamber 30 passes through the deionization chamber 30 and is discharged as deionized water. The water supplied to the acid recovery chamber 22 passes through the acid recovery chamber 22 and is discharged as recovered acid solution. The water supplied to the alkali recovery chamber 32 passes through the alkali recovery chamber 32 and is discharged as recovered alkali solution.

[0078] In such Figure 3 and Figure 4 In the case of a three-chamber electrodialysis device as shown, anion exchange membranes and cation exchange membranes are alternately arranged with bipolar membranes. Furthermore, in Figure 1 and Figure 2 In the two-chamber electrodialysis apparatus shown, anion exchange membranes and bipolar membranes are alternately arranged when recovering acidic treated water, such as hydrochloric acid regeneration waste liquid of cation exchange resin; and when recovering alkaline treated water, such as caustic soda regeneration waste liquid of anion exchange resin, cation exchange membranes and bipolar membranes are alternately arranged.

[0079] There are no restrictions on the flow rate or capacity of the water supplied to the acid recovery chamber and the alkali recovery chamber, but a lower flow rate and capacity will result in a higher concentration of the recovered alkali solution. Furthermore, by adjusting the liquid volume and capacity, the concentration can be adjusted according to the intended use of the recovered acid or alkali solution.

[0080] Three-chamber electrodialysis units can recover both acids and alkalis, but they are more complex than two-chamber electrodialysis units. Therefore, when only the recovery of either acid or alkali is required, a two-chamber electrodialysis unit is preferred.

[0081] The waste liquid from the regeneration of ion exchange resin can be stored in a supply tank as the treated liquid and can be supplied to the electrodialysis unit using pumps or other units.

[0082] The feed solution, which is supplied to the electrodialysis unit as the treated liquid, is typically circulated during electrodialysis treatment. The treated liquid (deionized water) after electrodialysis treatment is completed is discharged to any location. At the outlet of the deionization chamber of the electrodialysis unit, which supplies the feed solution, a pH measuring unit is provided to measure the pH of the treated liquid (deionized water). The endpoint of electrodialysis can be determined based on the pH value measured by this pH measuring unit.

[0083] (Waste liquid treatment system and waste liquid treatment method) Next, the waste liquid treatment system and waste liquid treatment method for treating the regeneration waste liquid of ion exchangers according to embodiments of the present invention will be described.

[0084] Figure 5An example of a wastewater treatment system for treating the regeneration wastewater of cation exchangers (cation exchange resins).

[0085] The wastewater treatment system 500 according to an embodiment of the present invention includes: a cation exchange device 102 filled with cation exchangers; a regeneration liquid storage tank 104 storing a solution (regeneration liquid) for regenerating the cation exchangers; and a regeneration waste liquid storage tank 106 storing the regeneration waste liquid of the cation exchangers. A regeneration liquid inlet pipeline L1 for introducing the regeneration liquid into the cation exchange device 102 is provided in the regeneration liquid storage tank 104. Furthermore, the wastewater treatment system 500 includes a first water storage tank 108, a second water storage tank 110, an electrode solution storage tank 112, and an electrodialysis device 300. The regeneration liquid can be supplied to the cation exchange device using a pump or similar means.

[0086] The wastewater treatment system 500 utilizes a cation exchanger 102 to treat groundwater, industrial water, and other treated liquids through ion exchange, thereby producing cation-exchanged water. Once a given flow rate is reached, the flow of treated liquid into the cation exchanger 102 is stopped, and the regenerated liquid stored in the regenerated liquid storage tank 104 is introduced into the cation exchanger 102 through pipeline L1. The regenerated liquid that has passed through the cation exchanger 102 is stored as regeneration waste liquid in the regeneration waste liquid storage tank 106. After regeneration, the cation exchanger 102 is re-introduced with treated liquid for ion exchange treatment to produce cation-exchanged water. Pretreatment devices such as membrane treatment devices, activated carbon filters, and coagulation sedimentation devices can be installed upstream of the cation exchanger 102, while post-treatment devices such as an electro-deionization (EDI) system and a degassing device can be installed downstream.

[0087] Here, Figure 5 The electrodialysis device 300 in the wastewater treatment system 500 shown can be used Figure 3 The electrodialysis device 300 shown is shown.

[0088] Furthermore, the waste liquid treatment system 500 having the above structure is a system that includes: an acid circulation mechanism connected to the first water storage tank 108 and the aforementioned acid recovery chamber. Figure 3 Acid recovery chamber 22); alkali circulation mechanism, which connects the second water storage tank 110 and the aforementioned alkali recovery chamber ( Figure 3 The alkali recovery chamber 32); the deionized water circulation mechanism, which connects the regenerated waste liquid storage tank 106 and the aforementioned deionization chamber ( Figure 3 The deionization chamber 24); the electrode liquid circulation mechanism, which is connected to the electrode liquid storage tank 112 and the aforementioned anode chamber ( Figure 3 The anode chamber 20) and the cathode chamber ( Figure 3The electrodialysis apparatus 300 includes a cathode chamber 34; an acid recovery delivery mechanism branching from the acid circulation mechanism and connected to the regenerated liquid storage tank 104; an alkali recovery delivery mechanism branching from the alkali circulation mechanism to deliver the recovered alkali to the outside of the system; and a pH sensor 36 (pH measurement unit) that measures the pH of the treated liquid obtained after the regenerated waste liquid of the cation exchanger passes through the deionization chamber of the electrodialysis apparatus 300. When the pH value measured by the pH measurement unit reaches a given value, the electrodialysis treatment ends, and the recovered acid is delivered to the regenerated liquid storage tank 104 via the acid recovery delivery mechanism. The recovered alkali is also delivered to the location outside the system where the recovered alkali is used via the alkali recovery delivery mechanism. Alternatively, the acid recovery delivery mechanism can deliver the recovered acid to the location outside the system where the recovered acid is used (e.g., the regenerated liquid storage tank of the anion exchange apparatus, which is the location where the regenerated acid is used).

[0089] As the pH measurement unit described above, a pH sensor 36 can be installed at the outlet of the deionization chamber of the electrodialysis apparatus 300, which is equipped with a DC power supply (not shown) that supplies power to the electrodialysis apparatus. These pH sensors 36 and the DC power supply are connected to a control device (not shown) such as a personal computer, which can control the current from the DC power supply applied to the cathode and anode of the electrodialysis apparatus 300 based on the pH data of the processed liquid sent from the pH sensors 36.

[0090] Figure 6 This describes an example of a wastewater treatment system for treating the regeneration wastewater of anion exchangers (anion exchange resins). The wastewater treatment system 600 according to embodiments of the present invention differs from the following aspects: Figure 5 The waste liquid treatment system is the same, replacing Figure 5 The cation exchange device 102 is equipped with an anion exchange device 103, and the electrodialysis device 400 is equipped instead of the electrodialysis device 300.

[0091] The waste liquid treatment system 600 according to an embodiment of the present invention includes: an anion exchange device 103 filled with anion exchanger; a regeneration liquid storage tank 104 storing a solution (regeneration liquid) for regenerating the anion exchanger; and a regeneration waste liquid storage tank 106 storing the regeneration waste liquid of the anion exchanger. A regeneration liquid inlet pipeline L1 for introducing the regeneration liquid into the anion exchange device 103 is provided in the regeneration liquid storage tank 104. Furthermore, the waste liquid treatment system 600 includes a first water storage tank 108, a second water storage tank 110, an electrode liquid storage tank 112, and an electrodialysis device 400.

[0092] The wastewater treatment system 600 utilizes anion exchange unit 103 to treat groundwater, industrial water, and other liquids by ion exchange, producing anion-exchanged water. Once a given flow rate is reached, the flow of the treated liquid into the anion exchange unit 103 is stopped, and the regenerated liquid stored in the regenerated liquid storage tank 104 is introduced into the anion exchange unit 103 through pipeline L1. The regenerated liquid that has passed through the anion exchange unit 103 is stored as regeneration waste liquid in the regeneration waste liquid storage tank 106. After regeneration, the anion exchange unit 103 is re-introduced with the treated liquid for ion exchange treatment to produce anion-exchanged water. Pretreatment devices such as membrane treatment devices, activated carbon filters, and coagulation and sedimentation devices can be installed upstream of the anion exchange unit 103, while post-treatment devices such as an electro-deionization (EDI) system and a degassing device can be installed downstream.

[0093] Here, Figure 6 The electrodialysis device 400 in the wastewater treatment system 500 shown can be used Figure 4 The electrodialysis device 400 shown is shown.

[0094] Furthermore, the waste liquid treatment system 600 having the above structure is a system that includes: an acid circulation mechanism connected to the first water storage tank 108 and the aforementioned acid recovery chamber. Figure 4 Acid recovery chamber 22); alkali circulation mechanism, which connects the second water storage tank 110 and the aforementioned alkali recovery chamber ( Figure 4 The alkali recovery chamber 32); the deionized water circulation mechanism, which connects the regenerated waste liquid storage tank 106 and the aforementioned deionization chamber ( Figure 4 The deionization chamber 30); the electrode liquid circulation mechanism, which is connected to the electrode liquid storage tank 112 and the aforementioned anode chamber ( Figure 4 The anode chamber 20) and the cathode chamber ( Figure 4 The electrodialysis apparatus 400 includes: a cathode chamber 34; a alkali solution delivery mechanism branching from the alkali solution circulation mechanism and connected to the regenerated solution storage tank 104; an acid solution delivery mechanism branching from the acid solution circulation mechanism to deliver the recovered acid solution outside the system; and a pH measuring unit (pH sensor 36) that measures the pH of the treated solution obtained after the regenerated waste liquid of the anion exchanger passes through the deion chamber of the electrodialysis apparatus 400. The electrodialysis process ends when the pH value measured by the pH measuring unit reaches a given value, and the recovered alkali solution is delivered to the regenerated solution storage tank 104 via the alkali solution delivery mechanism. The recovered acid solution is also delivered to a location outside the system for use of the recovered acid solution via the acid solution delivery mechanism. Alternatively, the alkali solution delivery mechanism can be a mechanism for delivering the recovered alkali solution outside the system, or it can deliver the recovered alkali solution to a location outside the system for use of the recovered alkali solution (e.g., the regenerated solution storage tank of the cation exchanger, which is a location for use of the regenerated alkali solution).

[0095] As the pH measurement unit described above, a pH sensor 36 can be installed at the outlet of the deionization chamber of the electrodialysis apparatus 400, which is equipped with a DC power supply (not shown) that supplies power to the electrodialysis apparatus. These pH sensors 36 and the DC power supply are connected to a control device (not shown) such as a personal computer, which can control the current from the DC power supply applied to the cathode and anode of the electrodialysis apparatus 400 based on the pH data of the processed liquid sent from the pH sensors 36.

[0096] (Endpoint management of pH-based electrodialysis) In this way, by managing the endpoint of electrodialysis based on the pH of the treatment solution, it is possible to prevent scale components from mixing into the recycled acid and alkali solutions, thus creating a liquid suitable for use as a regenerator in ion exchange devices.

[0097] For example, in methods for observing and determining pH changes, a pH meter can be installed at the deionization chamber outlet, in the regenerated waste liquid storage tank, in the first water tank, or in the second water tank, and the measured values ​​can be sent to the control device at given intervals. Electrodialysis is terminated when the pH reaches a given value (range) or when the slope of the change is within a given range. For example, regarding the tendency of pH changes, as mentioned above, the pH of the water in the first water tank gradually decreases from near neutral due to the influence of the generated acidic solution, and stabilizes at a low value after a certain period of time. As mentioned above, the pH of the water in the second water tank gradually increases from near neutral due to the influence of the generated alkaline solution, and stabilizes at a high value after a certain period of time. Furthermore, when the liquid in the regenerated waste liquid storage tank is cation exchanger regenerated waste liquid, the pH of the cation exchanger regenerated waste liquid gradually increases from the acidic side due to the influence of the ions in the cation exchanger regenerated waste liquid moving towards the chamber adjacent to the deionization chamber, and stabilizes at a value closer to the neutral or alkaline side than the initial value after a certain period of time. On the other hand, when the liquid in the storage tank is anion exchanger regeneration waste liquid, due to the influence of the ion class in the anion exchanger regeneration waste liquid moving towards the chamber adjacent to the deionization chamber, the pH of the anion exchanger regeneration waste liquid gradually decreases from the alkaline side, and after a certain period of time, it stabilizes at a value closer to the neutral or acidic side than the initial value.

[0098] When using a three-chamber electrodialysis unit to perform electrodialysis treatment on an acid feed solution (pH≤3, preferably pH<1) (refer to...) Figure 3 If electrodialysis is performed on the acid feed solution, the most easily moving ions, namely H+, will be... + The acid feed solution moves through the cation exchange membrane to the recovered alkali solution, Cl... - It moves to the recovery acid solution through the anion exchange membrane. Then, among the ions present from the dissociation of neutral salts such as NaCl or CaCl2 in the acid supply solution, Na+, as a cation, [is released / ...+ Ca 2+ The Cl- ions move towards the recycled alkali solution. - It moves towards the recycled acid solution. This is due to H... + The molar conductivity is greater than that of Na + Ca 2+ This phenomenon is caused by other cations. Ion movement occurs while the ions in each liquid remain electrically neutral. In H... + The electrodialysis treatment ends approximately at the point when the transfer from the acid supply solution to the alkali recovery solution is nearly complete (the pH of the treatment solution from the deionization chamber is preferably around 1-3, more preferably 2-2.5). This, in particular, inhibits the formation of Ca2+. 2+ Mg 2+ This prevents hardness components from moving towards the alkali recovery solution side and avoids the formation of scale in the alkali recovery chamber. By setting the endpoint of electrodialysis to the moment when the pH of the treated solution (deionized water) from the deionization chamber becomes above 1, acid and alkali separation is fully achieved. By setting it to the moment when the pH becomes below 3, the movement of hardness components towards the alkali recovery solution can be suppressed, reducing the risk of scale precipitation on the alkali recovery chamber side.

[0099] When using a two-chamber electrodialysis unit to perform electrodialysis treatment on an acid feed solution (pH≤3, preferably pH<1) (refer to...) Figure 1 If the acid feed solution is subjected to electrodialysis, then Cl - The acid moves from the acid supply solution to the recycled acid solution, while OH... - It is supplied to the acid supply solution, thereby raising the pH. When the pH of the treated solution of the acid supply solution reaches approximately 1-3, similar to the situation described above, the H+ in the acid supply solution... + and equivalent amounts of Cl - Most of the acid moves from the acid supply solution to the recycled acid solution, at which point the electrodialysis process ends, thereby preventing the formation of scale from hardness components in the deionization chamber supplied with the acid supply solution.

[0100] Therefore, when the liquid to be treated supplied to the deionization chamber of the electrodialysis apparatus is an acid supply solution, the endpoint of electrodialysis is preferably when the pH of the treatment solution (deionized water) from the deionization chamber is 1 or higher and 3 or lower, more preferably when it is 1.5 or higher and 2.5 or lower, and even more preferably when it is 2 or higher and 2.5 or lower.

[0101] The endpoint management of electrodialysis can be achieved by measuring the pH of the treatment solution from the deionization chamber. The acid feed solution after electrolysis is coarsely neutralized, thus reducing the amount of neutralizing reagents used in further neutralization of the treatment solution. Furthermore, the treatment solution can be used as cooling water for cooling equipment, miscellaneous water, or returned to the upstream of the water treatment plant.

[0102] It should be noted that in the detection of the endpoint of electrodialysis, the pH of the treated solution from the deionization chamber and the pH of the recovered acid from the acid recovery chamber can be measured together. For example, the endpoint can also be defined as the point where the pH of the treated solution from the deionization chamber reaches a value within a given range and the pH of the recovered acid reaches <0.5.

[0103] When using a three-chamber electrodialysis unit to treat an alkaline feed solution (pH≥12, preferably pH>13) via electrodialysis (refer to...) Figure 4 If electrodialysis is performed on the alkaline supply solution, then firstly OH... - As the alkaline supply solution moves through the anion exchange membrane, its pH decreases. If the pH decreases, silica-derived scale is easily formed. Therefore, the electrodialysis process is terminated just before silica scale precipitates, i.e., when the pH of the treated solution (deionized water) from the deionization chamber does not become too low (preferably 9 or higher, more preferably 10 or higher), thereby preventing silica scale formation. Furthermore, by setting the endpoint of the electrodialysis at a pH that is preferably less than 12, more preferably less than 11.5, separation can be performed more thoroughly.

[0104] It should be noted that in the detection of the endpoint of electrodialysis, the pH of the treated solution from the deionization chamber and the pH of the recovered alkali solution from the alkali recovery chamber can be measured together. For example, the endpoint can also be defined as the point where the pH of the treated solution from the deionization chamber reaches a value within a given range and the pH of the recovered alkali solution reaches >13.

[0105] When using a two-chamber electrodialysis unit to treat the alkaline feed solution (pH≥12, preferably pH>13) via electrodialysis (refer to...) Figure 2 If the alkali supply solution is subjected to electrodialysis, the Na in the alkali supply solution will be... + It moves through the cation exchange membrane due to the supply of H+ to the alkaline supply solution. + Therefore, the pH decreases. If the pH decreases, scale originating from silica is easily formed. Therefore, electrodialysis should be stopped just before silica scale precipitates, that is, when the pH of the treatment solution (deionized water) from the deionization chamber does not become too low (preferably 9 or higher, more preferably 10 or higher). This prevents the formation of silica scale, similar to the case when electrodialysis is performed on the alkaline supply solution using the aforementioned three-chamber electrodialysis apparatus. Furthermore, by setting the endpoint of this electrodialysis at a pH that is preferably less than 12, more preferably less than 11.5, separation can be performed more thoroughly.

[0106] Alternatively, similar to the case where the alkaline supply solution is electrodialyzed using the aforementioned three-chamber electrodialysis apparatus, the pH of the treated solution from the deionization chamber and the pH of the recovered alkaline solution from the alkaline recovery chamber can be measured. For example, the endpoint can be set when the pH of the treated solution from the deionization chamber reaches a value within a given range and the pH of the recovered alkaline solution reaches >13.

[0107] Therefore, when the liquid to be treated supplied to the deionization chamber of the electrodialysis apparatus is an alkaline supply solution, the endpoint of electrodialysis is preferably when the pH of the treated liquid (deionized water) from the deionization chamber decreases from a value of 12 or higher before treatment, before reaching a value of less than 9. Further, the endpoint of electrodialysis is preferably when the pH of the treated liquid (deionized water) from the deionization chamber decreases from a value of 12 or higher (preferably pH > 13) before treatment, reaching a value of less than 12, and more preferably reaching a value of 11.5 or lower.

[0108] (Acid recovery chamber 22 and alkali recovery chamber 32 of the electrodialysis unit) In the aforementioned electrodialysis apparatus, water is pressurized by a pump or other delivery unit, and is recovered as acid from the acid recovery chamber 22 and as alkali from the alkali recovery chamber 32. This recovered water can then be reused as a regenerator for resin towers, a neutralizing agent for waste liquid, etc. The recovered acid and alkali can be reused in the same series of water treatment systems or in other water treatment systems. When used in other water treatment systems, the recovered acid and alkali can be effectively reused. The water supplied to the acid recovery chamber 22 and the alkali recovery chamber 32 is preferably pure water, but acidic or alkaline water suitable for reuse as a regenerator or neutralizing agent for resin towers can also be used.

[0109] (Anode chamber 20 and cathode chamber 34 of the electrodialysis unit) Electrode solutions are introduced into the anode chamber 20 (the unit defined by the first bipolar membrane and the anode) and the cathode chamber 34 (the unit defined by the second bipolar membrane and the cathode) of the aforementioned electrodialysis apparatus. The electrode solutions can be aqueous solutions of metal hydroxides or metal salts, such as NaOH aqueous solution or Na2SO4 aqueous solution.

[0110] (Using an electrodialysis device to separate ions from the liquid being treated) In the aforementioned three-chamber electrodialysis apparatus, H, which originally existed in a dissociated state in the supply solutions (acid supply solution, alkali supply solution), can be... + or OH - Selective separation from the feed solution (treated solution). This allows for separation with high current efficiency and reduces the separation time. In the properties of electrodialysis, generally, if Na... + Ca 2+and Cl in equivalent quantities - SO4 2- Cl - and Na in equivalent quantities + When ions that become neutral salts when considered as compounds are separated, the amount of ions in the feed solution decreases, making it difficult for current to flow, reducing current efficiency, and lengthening the separation time. Therefore, it is preferable to preferentially separate H+ that originally existed in a dissociated state in the feed solution. + or OH - The goal is to separate as much of the ions as possible from the supply solution (the solution being treated), while minimizing the separation of ions that become other neutral salts.

[0111] In the above-mentioned two-chamber electrodialysis device, since the ions that have passed through the ion exchange membrane and the equivalent amount of ions are replenished to the supply liquid (the liquid being treated), the conductivity of the supply liquid will not decrease significantly and the current efficiency will not change. However, it can achieve the same scale inhibition effect as the three-chamber recovery electrodialysis device.

[0112] (Regenerated waste liquid) In this invention, H+, which originally existed in a dissociated state in the supply liquid (acid supply liquid, alkali supply liquid) to the electrodialysis device, can be selectively separated. + or OH - Therefore, it is not always necessary to mix the regenerated acid waste liquid (acid supply liquid) from the cation exchanger with the regenerated alkali waste liquid (alkali supply liquid) from the anion exchanger. If there are other systems within the plant where these regenerated acid and alkali waste liquids can be reused, designs can be implemented such as electrodialysis treatment and recovery of only the regenerated acid waste liquid, or neutralization treatment of the regenerated alkali waste liquid in other systems. Furthermore, by treating the regenerated acid and alkali waste liquids separately without mixing them, it is possible to ensure the concentration of dissociated H+ in each waste liquid. + and OH - Therefore, the amount of acid and alkali that can be recovered by the present invention is greater than when the waste liquid is mixed. Thus, the present invention has the advantage of being able to use the regeneration waste liquid of the ion exchanger without mixing it with the regeneration waste liquid of other ion exchangers.

[0113] (The objects treated by the electrodialysis system / electrodialysis method) The electrodialysis system and method of the present invention are not particularly limited in that the treated liquid is either an acidic liquid (acid supply liquid) with a pH of less than 3 or an alkaline liquid (alkali supply liquid) with a pH of more than 12. Preferably, it is the regeneration waste liquid discharged during the regeneration treatment of ion exchangers, and particularly preferably, it is the regeneration waste liquid discharged during the regeneration treatment of groundwater or industrial water used in the production of pure water in semiconductor plants and the like. Furthermore, when the treated liquid is acidic (acid supply liquid), it is particularly preferable that its pH is less than 1 (pH < 1), and when the treated liquid is alkaline (alkali supply liquid), it is particularly preferable that its pH is greater than 13 (pH > 13).

[0114] Example (Example 1) The regeneration waste liquid of the cation exchange resin is used as the acid supply solution to... Figure 3 The three-chamber electrodialysis apparatus shown is supplied with electrodialysis under the following conditions to obtain regenerated acid (treatment solution).

[0115] • Device: Bipolar membrane electrodialysis device manufactured by Astom (product name: Acilyzer EX3B) • Feed liquid: The quality of the regeneration waste liquid from the cation exchange resin tower for pure water production is recorded in the table below (Table 1).

[0116] • Supply volume and circulation flow rate: 850ml, 1.4L / min • Acid recovery volume and circulation flow rate: 850 ml, 1.4 L / min • Amount of alkali solution recovered and circulation flow rate: 850 ml, 1.4 L / min • Voltage value: 10V The pH of the treated solution after the feed solution passed through the electrodialysis device was determined using a portable pH meter (product name: HM-40P) manufactured by DKK-TOA Co., Ltd. (glass electrode method).

[0117] Ions in the supply and treatment solutions were determined using an ion chromatograph (product name: Dionex Integrion) manufactured by Thermo Fisher Scientific Co., Ltd.

[0118] The water quality (pH and component concentration) of the supply liquid (regenerated waste liquid) is shown in Table 1.

[0119] [Table 1] The changes in component concentration, pH value, and current value of the regenerated waste liquid (treated liquid) after electrodialysis relative to the operating time of the electrodialysis unit (dialysis time) are shown in the figure. Figure 7 , Figure 8 In addition, the water quality (pH and component concentration) of the regenerated waste liquid (treatment liquid) in electrodialysis is shown in Table 2.

[0120] Supply the regenerated waste liquid to the electrodialysis unit and begin electrodialysis, setting the voltage to 10V at this point. From the start of operation (dialysis start) until approximately 23 minutes later, Cl... - The concentration decreased significantly, but the cation concentration (after removing H+) remained high. + , that is Na + Ca + Mg + K + The total concentration of T-Cation relative to Cl - The decrease in concentration is relatively small. Originally, to maintain electroneutrality, Cl... - The slope of the concentration gradient should be the same as the slope of the cation concentration gradient, but they differ in the period from the start of operation to approximately 23 minutes. Therefore, it can be inferred that in this period, the H+ in the HCl of the regenerated waste liquid, as a cation, is... + Movement occurs, Na in NaCl + The amount of movement is small. Therefore, the pH of the regenerated waste liquid (treated liquid) after electrodialysis gradually increases.

[0121] If 23 minutes have elapsed since the start of operation (dialysis), then Na... + Concentration and Cl - The concentration decreased approximately by equivalent amounts (Table 2). This is because the excess H⁺ in the regenerated waste liquid was reduced through electrodialysis, thus facilitating the separation of NaCl. The H⁺ concentration in the regenerated waste liquid... + Almost neutralized, pH rose, exceeding 2 after 43 minutes (Table 2). Figure 7 ).

[0122] On the other hand, such as Figure 8 As shown, the current value gradually decreased from around 23 minutes. This is because the ion concentration in the regenerated waste liquid decreased due to electrodialysis, thus reducing the current value. From nearly 60 minutes onwards, the current value decreased even more sharply.

[0123] It is known that when the pH of the regenerated waste liquid supplied as acid supply reaches the range of 1 to 3 after passing through the electrodialysis device, in this embodiment, for example, the electrodialysis is stopped within the range of 8 to 43 minutes (pH 1.3 to 2.1) from the start of operation (dialysis start), thereby enabling the recovery of acid in a short time.

[0124] During electrodialysis, no sharp decrease in current value was observed due to scale formation, and scale material could not be visually observed on the ion exchange membrane surface after electrodialysis.

[0125] [Table 2] (Example 2) The regeneration waste liquid of the anion exchange resin is used as the alkali supply solution to... Figure 2 The two-chamber electrodialysis apparatus shown is supplied with electrodialysis treatment under the following conditions to obtain regenerated alkali (treatment solution).

[0126] • Device: Bipolar membrane electrodialysis device manufactured by Astom (product name: Acilyzer EX3B) • Feed liquid: The quality of the regeneration waste liquid from the anion exchange resin tower used for pure water production is recorded in the table below (Table 3).

[0127] • Supply volume and circulation flow rate: 850ml, 1.4L / min • Amount of alkali solution recovered and circulation flow rate: 850 ml, 1.4 L / min • Voltage value: 12V The pH of the treated solution after the feed solution passed through the electrodialysis device was determined using a portable pH meter (product name: HM-40P) manufactured by DKK-TOA Co., Ltd. (glass electrode method).

[0128] Ions in the supply and treatment solutions were determined using an ion chromatograph (product name: Dionex Integrion) manufactured by Thermo Fisher Scientific Co., Ltd.

[0129] The water quality (pH and component concentration) of the supply liquid (regenerated waste liquid) is shown in Table 3.

[0130] [Table 3] The Na+ in the regenerated waste liquid (treatment liquid) after electrodialysis + The changes in concentration, pH value, and current value relative to the operating time of the electrodialysis unit (dialysis time) are shown in the figure. Figure 9 , Figure 10 In addition, the water quality (pH and component concentration) of the regenerated waste liquid (treatment liquid) in electrodialysis is shown in Table 4.

[0131] Supply the regenerated waste liquid to the electrodialysis unit and begin dialysis, setting the voltage to 12V at this point. From the start of operation (dialysis commencement), Na... + The concentration decreased. This was due to the supply of H+ to the feed liquid (regenerated waste liquid). +Therefore, the pH gradually decreases.

[0132] From the start of operation (dialysis) for approximately 31 minutes, the pH drops sharply. This is due to the OH- ions in the feed solution (regenerated waste liquid). - Almost neutralized, and after that, not only Na + H + The movement of ions also begins to occur primarily. Therefore, the subsequent movement and separation of ions are not fully carried out.

[0133] On the other hand, such as Figure 10 As shown, the current value remained roughly constant from the start of operation (dialysis) until 21 minutes later.

[0134] It is known that when the pH of the regenerated waste liquid (pH≥12) supplied as alkali supply solution decreases to 9 after passing through the electrodialysis device, in this embodiment, for example, electrodialysis is stopped 21 minutes after the start of operation (dialysis start) (pH11.1), thereby enabling the recovery of alkali in a short time.

[0135] During electrodialysis, no sharp decrease in current value was observed due to scale formation, and scale material could not be visually observed on the ion exchange membrane surface after electrodialysis.

[0136] [Table 4] (Comparative Example 1) The electrodialysis was performed in the same manner as in Example 1, except that the operating time (dialysis time) was 100 minutes. As a result, the current value was approximately zero, and white scale was observed on the cation exchange membrane surface. This was attributed to the precipitation of components such as Ca(OH)₂ and Mg(OH)₂.

[0137] (Comparative Example 2) The electrodialysis was performed in the same manner as in Example 2, with a running time (dialysis time) of 90 minutes. As a result, the current value did not change significantly, but a gel-like precipitate was observed on the bipolar membrane surface. This was attributed to the precipitation of SiO2.

[0138] Symbol Explanation 1: Anode 3: First bipolar membrane 5: Anion exchange membrane 7: Cation exchange membrane 9: Second bipolar membrane 11: Cathode 20: Anode Chamber 22: Acid Recovery Room 24, 30: Deionization chamber 32: Alkali Recovery Room 34: Cathode Chamber 36: pH Measurement Unit 100: Two-compartment acid recovery electrodialysis unit 102: Cation exchanger 103: Anion exchange device 104: Regenerated liquid storage tank 106: Regenerated waste liquid storage tank 108: First water storage tank 110: Second water storage tank 112: Electrode solution storage tank 200: Two-chamber alkali recovery electrodialysis unit 300: Three-chamber acid recovery electrodialysis unit 400: Three-chamber alkali recovery electrodialysis unit 500: Wastewater treatment system for cation exchanger regeneration wastewater 600: Wastewater treatment system for regenerated wastewater from anion exchangers.

Claims

1. An electrodialysis system, characterized in that, Used to treat solutions with a pH below 3 or a pH above 12. The electrodialysis system has the following features: An electrodialysis apparatus having at least an anode, a cathode, a first bipolar membrane, an ion exchange membrane, and a second bipolar membrane, wherein the first bipolar membrane, the ion exchange membrane, and the second bipolar membrane are sequentially arranged between the anode and the cathode, starting from the anode side; as well as The pH measuring unit measures the pH of the treated solution obtained after the treated solution passes through the electrodialysis device. When the pH value of the treated solution, as measured by the pH measuring unit, reaches a given value, the electrodialysis treatment performed by the electrodialysis device ends.

2. The electrodialysis system according to claim 1, wherein, The liquid being treated is a liquid with a pH below 3, and the ion exchange membrane of the electrodialysis device is an anion exchange membrane.

3. The electrodialysis system according to claim 1, wherein, The liquid being treated is a liquid with a pH above 12, and the ion exchange membrane of the electrodialysis device is a cation exchange membrane.

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

5. The electrodialysis system according to claim 2, wherein, The electrodialysis apparatus is equipped with: The anode chamber, defined by the anode and the first bipolar film; and The cathode chamber is defined by the cathode and the second bipolar film. The electrodialysis apparatus includes: An acid recovery chamber, located between the anode chamber and the cathode chamber, is demarcated by the first bipolar membrane and the anion exchange membrane. Water is supplied to the chamber and treated by electrodialysis to generate a recovered acid solution. as well as The deionization chamber, defined by the anion exchange membrane and the second bipolar membrane, is supplied with an acid feed solution as the treated liquid, which is then treated by electrodialysis to generate deionized water. The unit group consisting of the acid recovery chamber and the deionization chamber may be configured with one or more repeated configurations.

6. The electrodialysis system according to claim 3, wherein, The electrodialysis apparatus is equipped with: The anode chamber, defined by the anode and the first bipolar film; and The cathode chamber is defined by the cathode and the second bipolar film. The electrodialysis apparatus includes: A deionization chamber, defined by the first bipolar membrane and the cation exchange membrane, is located between the anode chamber and the cathode chamber. An alkaline feed solution is supplied as the treated liquid, and deionized water is generated through electrodialysis. The alkali recovery chamber, defined by the cation exchange membrane and the second bipolar membrane, is supplied with water and treated by electrodialysis to generate a recovered alkali solution. The unit group consisting of the deionization chamber and the alkali recovery chamber may be configured with one or more repeated configurations.

7. The electrodialysis system according to claim 4, wherein, The electrodialysis apparatus is equipped with: The anode chamber, defined by the anode and the first bipolar film; and The cathode chamber is defined by the cathode and the second bipolar film. The electrodialysis apparatus includes: An alkali recovery chamber, located between the anode chamber and the cathode chamber, is demarcated by the cation exchange membrane and the second bipolar membrane. Water is supplied to the chamber and treated by electrodialysis to generate a recovered alkali solution. The acid recovery chamber, defined by the anion exchange membrane and the first bipolar membrane, is supplied with water and treated by electrodialysis to generate a recovered acid solution. as well as The deionization chamber, defined by the cation exchange membrane and the anion exchange membrane, is supplied with the solution to be treated and deionized water is generated through electrodialysis. The unit group consisting of the acid recovery chamber, the deionization chamber, and the alkali recovery chamber may be configured with one or more repeated configurations.

8. The electrodialysis system according to claim 2 or 4, wherein, The pH of the liquid being treated is less than 1. When the pH of the treatment solution reaches a range of 1 or higher and 3 or lower, the electrodialysis treatment performed by the electrodialysis device is terminated.

9. The electrodialysis system according to claim 3 or 4, wherein, The pH of the liquid being treated is above 12. The electrodialysis treatment performed by the electrodialysis device is terminated before the pH of the treatment solution reaches a range of less than 9.

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

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

12. A waste liquid treatment system, characterized in that, have: An ion exchange device filled with ion exchanger; A regenerant supply device that supplies the regenerant of the ion exchanger to the ion exchange device; and An electrodialysis system that treats the regeneration waste liquid discharged from the ion exchange unit. The regenerated waste liquid has a pH below 3 or a pH above 12. The electrodialysis system has the following features: An electrodialysis apparatus having at least an anode, a cathode, a first bipolar membrane, an ion exchange membrane, and a second bipolar membrane, wherein the first bipolar membrane, the ion exchange membrane, and the second bipolar membrane are sequentially arranged between the anode and the cathode, starting from the anode side; as well as The pH measuring unit measures the pH of the treated liquid obtained after the regenerated waste liquid passes through the electrodialysis device. When the pH value of the treated solution, as measured by the pH measuring unit, reaches a given value, the electrodialysis treatment performed by the electrodialysis device ends.

13. An electrodialysis method, characterized in that, Used to treat solutions with a pH below 3 or a pH above 12. In the electrodialysis method, Electrodialysis is performed using an electrodialysis device, wherein the electrodialysis device has at least an anode, a cathode, a first bipolar membrane, an ion exchange membrane, and a second bipolar membrane, and the first bipolar membrane, the ion exchange membrane, and the second bipolar membrane are sequentially arranged between the anode and the cathode, starting from the anode side; The pH of the treated solution obtained after the treated solution passes through the electrodialysis device is measured; When the pH value of the treated solution reaches a given value, the electrodialysis treatment performed by the electrodialysis device is terminated.

14. A waste liquid treatment method, characterized in that, have: The regenerated liquid supply process includes supplying a regenerated liquid containing an ion exchanger to an ion exchange apparatus filled with the ion exchanger; and The electrodialysis process includes treating the regenerated waste liquid discharged from the ion exchange unit. The regenerated waste liquid has a pH below 3 or a pH above 12. The electrodialysis process includes the following steps: The regenerated waste liquid is introduced into an electrodialysis device for electrodialysis treatment. The electrodialysis device includes at least an anode, a cathode, a first bipolar membrane, an ion exchange membrane, and a second bipolar membrane. Between the anode and the cathode, the first bipolar membrane, the ion exchange membrane, and the second bipolar membrane are sequentially arranged from the anode side. The pH of the treated liquid obtained after the regenerated waste liquid passes through the electrodialysis device is measured. When the pH value of the treated solution measured in the pH measurement step reaches a given value, the electrodialysis treatment performed by the electrodialysis device ends.

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