KR-20260064712-A - Method of operating an electrodialysis device equipped with a hydrocarbon-based anion exchange membrane having ion-selective permeability characteristics

KR20260064712AKR 20260064712 AKR20260064712 AKR 20260064712AKR-20260064712-A

Abstract

A method of operating an electrodialysis device comprises a process of electrodialyzing an iodide-containing solution containing an iodide salt and a solvent using an electrodialysis device, wherein the electrodialysis device acquires an IV curve representing the relationship between DC current and voltage according to a DC resistance measurement method, and has an anion exchange membrane having a monovalent ion selective permeable layer in which a minimum appears in a second derivative value curve obtained by taking a second derivative of the IV curve, and in the process of electrodialysis, when the effective area (dm²) of the anion exchange membrane is d and the value of the DC current (A) corresponding to the minimum appearing in the second derivative value curve is a1, the current density (A/dm²) is set to be greater than or equal to a1/d.

Inventors

바바, 마사히코
나카무라, 유키
도이, 쇼이치

Assignees

가부시키가이샤 고도 시겐

Dates

Publication Date: 20260507
Application Date: 20240930
Priority Date: 20231006

Claims (8)

The method includes a process of electrodialyzing an iodide-containing solution containing an iodide salt and a solvent using an electrodialysis device, and The above electrodialysis device is equipped with an anion exchange membrane having a monovalent ion selective permeable layer, wherein an IV curve representing the relationship between DC current and voltage is obtained by a DC resistance measurement method, and a minimum appears in the second derivative value curve obtained by taking the second derivative of the IV curve. A method of operating an electrodialysis device in the above electrodialysis process, wherein the effective area (dm²) of the anion exchange membrane is denoted as d, and the value of the direct current (A) corresponding to the minimum appearing on the second derivative curve is denoted as a1, and the current density (A/dm²) is set to be greater than or equal to a1/d.
In paragraph 1, A method of operating an electrodialysis device in which the lower limit of a1/d is 0.5 A/d m² or more.
In paragraph 1 or 2, A method of operating an electrodialysis device in which the upper limit of a1/d is 10A/d㎡ or less.
In paragraph 1 or 2, When a2 is the value of the DC current (A) corresponding to the maximum appearing on the second derivative curve obtained by taking the second derivative of the above IV curve (where a2 > a1), A method of operating an electrodialysis device, wherein the current density (A/dm²) during the above electrodialysis process is set to a2/d or less.
In paragraph 4, A method of operating an electrodialysis device in which a2/d-a1/d is 0.5 A/d㎡ or more and 10 A/d㎡ or less.
In paragraph 1 or 2, A method of operating an electrodialysis device in which the SO4 index in the anion exchange membrane, measured according to the following seawater concentration test, is 3.0× 10⁻³ N or higher and 50.0× 10⁻³ N or lower. Seawater Concentration Test A small electrodialysis device (conducting membrane area 100 cm²) is used in which a pair of cation exchange membranes with a membrane resistance of 1.5 Ω· cm² or more and 2.5 Ω· cm² or less are assembled such that the anion exchange membrane to be evaluated has a monovalent selective surface facing the desalination chamber. Seawater at 25°C is flowed into the desalination chamber at a flow rate of 6 cm/sec, and a 3.5 mol/L NaCl aqueous solution is filled into the concentration chamber. Electrodialysis is performed at a current density of 3 A/ d m² until there is no change in concentration in the concentration chamber, and the concentration of SO₄²⁻ in the concentrate obtained is measured as the SO₄²⁻ index.
In paragraph 1 or 2, A method of operating an electrodialysis device, wherein the anion exchange membrane comprises a copolymer of styrene-divinylbenzene having a quaternary ammonium group.
An anion exchange membrane having a monovalent ion-selective permeable layer, used exclusively for electrodialysis of an iodide-containing solution containing an iodide salt and a solvent, and When an IV curve representing the relationship between the DC current and voltage of the anion exchange membrane in question is acquired using the DC resistance measurement method, a local minimum appears in the second derivative curve obtained by taking the second derivative of the IV curve. Anion exchange membrane.

Description

Method of operating an electrodialysis device equipped with a hydrocarbon-based anion exchange membrane having ion-selective permeability characteristics The present invention relates to a method of operating an electrodialysis device and an anion exchange membrane. Various developments have been made regarding technologies for recovering iodine from waste liquid. As a technology of this type, the technology described in Patent Document 1 is known, for example. In addition to iodine components such as iodide ions ( I- ), divalent ions such as sulfate ions (SO42- ) may also coexist in the waste liquid. For example, sulfate ions are typically contained in the waste liquid at a concentration of 1 g/L or more, which is below the saturation solubility of sulfates, and more generally at a concentration of about 20 to 50 g/L. Patent Document 1 describes a method of performing electrodialysis on a stock solution contained in a desalination chamber, which contains an inorganic anion having iodine and an inorganic anion having fluorine, using a monovalent selective anion exchange membrane, etc. (Claim 1 of Patent Document 1, examples, etc.). FIG. 1 is a cross-sectional view schematically illustrating an example of the configuration of an electrodialysis device of the present embodiment. FIG. 2 is a schematic diagram illustrating an example of the configuration of an iodine recovery system of the present embodiment. FIG. 3 is a flowchart illustrating an example of an iodine recovery process of the present embodiment. Figure 4 shows the IV curve of Comparative Example 1. Figure 5 shows the second derivative curve obtained by taking the second derivative of the IV curve of Comparative Example 1. Figure 6 shows the IV curve of Example 1. Figure 7 shows the second derivative curve obtained by taking the second derivative of the IV curve of Example 1. Figure 8 shows the IV curve of Example 2. FIG. 9 shows the second derivative curve obtained by taking the second derivative of the IV curve of Example 2. Figure 10 shows the IV curve of Example 3. FIG. 11 shows the second derivative curve obtained by taking the second derivative of the IV curve of Example 3. Figure 12 shows the IV curve of Comparative Example 2. FIG. 13 shows the second derivative curve obtained by taking the second derivative of the IV curve of Comparative Example 2. Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, in all drawings, like components are given like reference numerals, and descriptions are omitted as appropriate. Furthermore, the drawings are schematic diagrams and do not correspond to actual dimensional ratios. An overview of the operation method of the electrodialysis device of the present embodiment is described. The method of operating the electrodialysis device of the present embodiment is, The method includes a process of electrodialyzing an iodide-containing solution containing an iodide salt and a solvent using an electrodialysis device, and An electrodialysis device is equipped with an anion exchange membrane having a monovalent ion selective permeable layer, wherein an IV curve representing the relationship between DC current and voltage is obtained by the DC resistance measurement method, and a minimum appears in the second derivative value curve obtained by taking the second derivative of the IV curve. In the electrodialysis process, the effective area dm² of the anion exchange membrane is denoted as d, and the value of the direct current (A) corresponding to the minimum appearing on the second derivative curve is denoted as a1, and the current density (A/dm²) is set to be greater than or equal to a1/d. According to the findings of the inventors, a new current-voltage characteristic of an anion exchange membrane is that a local minimum appears in the second derivative curve obtained by taking the second derivative of the IV curve. Having a local minimum in the second derivative curve means that the first derivative curve exhibits a decreasing function, and the membrane resistance decreases with increasing current. In addition, the above current-voltage characteristics are exhibited in current-voltage measurement tests using an aqueous solution containing iodide salts, but although the detailed mechanism is unclear, it was also found through experiments that they are not exhibited when other halides, such as chloride salts or bromide salts, are used. When using an anion exchange membrane having current-voltage characteristics that appear when using such iodide salts, and when electrodialyzing an iodide-containing solution containing iodide salts, by setting the current density (A/dm²) during the electrodialysis process to a1/d or higher, it is possible to suppress the increase in membrane voltage even at relatively high current densities, thereby facilitating the movement of iodide ions and making it possible to increase the productivity (energy efficiency) of iodide ions