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CN-121985990-A - Method for operating electrodialysis device having hydrocarbon anion-exchange membrane having ion-selective permeation characteristics

CN121985990ACN 121985990 ACN121985990 ACN 121985990ACN-121985990-A

Abstract

The method for operating an electrodialysis device includes a step of electrodialysis an iodide-containing solution containing an iodide salt and a solvent using an electrodialysis device, wherein the electrodialysis device includes an anion exchange membrane having a monovalent ion permselective layer, the anion exchange membrane acquires a current-voltage curve representing a relationship between a direct current and a voltage according to a direct current resistance measurement method, a minimum value appears in a secondary differential value curve obtained by differentiating the current-voltage curve twice, and in the electrodialysis step, when an effective area (dm 2 ) of the anion exchange membrane is d and a value of a direct current (A) corresponding to the minimum value appearing in the secondary differential value curve is a1, a current density (A/dm 2 ) is set to a1/d or more.

Inventors

  • Haseki Masahiko
  • NAKAMURA KAORU
  • DOI SHOICHI

Assignees

  • 株式会社合同资源

Dates

Publication Date
20260505
Application Date
20240930
Priority Date
20231006

Claims (8)

  1. 1. A method for operating an electrodialysis device, wherein, The method for operating an electrodialysis device includes a step of electrodialysis an iodide-containing solution containing an iodide salt and a solvent using the electrodialysis device, The electrodialysis device comprises an anion exchange membrane having a monovalent ion selective permeability layer, wherein the anion exchange membrane acquires a current-voltage curve representing the relationship between a direct current and a voltage according to a direct current resistance measurement method, and a minimum value appears in a secondary differential value curve obtained by subjecting the current-voltage curve to secondary differentiation, In the electrodialysis step, when d is the effective area of the anion-exchange membrane and a1 is the value of a direct current corresponding to the minimum value appearing in the secondary differential value curve, the current density is set to a1/d or more, the unit of the effective area is dm 2 , the unit of the direct current is A, and the unit of the current density is A/dm 2 .
  2. 2. A method of operating an electrodialysis unit as claimed in claim 1, wherein, The lower limit of a1/d is 0.5A/dm 2 or more.
  3. 3. A method of operating an electrodialysis unit as claimed in claim 1 or 2, wherein, The upper limit of a1/d is 10A/dm 2 or less.
  4. 4. A method of operating an electrodialysis unit as claimed in claim 1 or 2, wherein, When the value of the direct current corresponding to the maximum value appearing in the quadratic differential value curve obtained by quadratic differentiating the current-voltage curve is set to a2 and a2> a1, The current density in the electrodialysis step is set to be a2/d or less, the unit of direct current is A, and the unit of current density is A/dm 2 .
  5. 5. A method of operating an electrodialysis unit as claimed in claim 4, wherein, A2/d-a1/d is 0.5A/dm 2 or more and 10A/dm 2 or less.
  6. 6. A method of operating an electrodialysis unit as claimed in claim 1 or 2, wherein, The anion exchange membrane has an SO 4 index of 3.0X10 -3 N or more and 50.0X10 -3 N or less as measured by the seawater concentration test described below, Seawater concentration test: Using a small electrodialysis apparatus for measuring SO 4 2- concentration in a concentrated solution obtained by conducting electrodialysis at a current density of 3A/dm 2 until the concentration change in the concentration chamber disappears as the SO 4 index, wherein the concentration of the concentrated solution obtained by conducting electrodialysis at a current density of 3A/dm 2 is 1.5. OMEGA. Cm 2 or more and 2.5 Ω Cation exchange membranes of cm 2 or less were used as counter membranes, anion exchange membranes to be evaluated were assembled so that monovalent selective surfaces faced toward the desalting chambers, and the current-carrying membrane area of the small electrodialysis device was 100cm 2 .
  7. 7. A method of operating an electrodialysis unit as claimed in claim 1 or 2, wherein, The anion exchange membrane comprises a copolymer of styrene divinylbenzene having quaternary ammonium groups.
  8. 8. An anion exchange membrane having a monovalent ion permselective layer for use only in electrodialysis of an iodide-containing solution comprising an iodide salt and a solvent, wherein, When a current-voltage curve representing the relationship between the direct current and the voltage of the anion exchange membrane measured by a direct current resistance measurement method is obtained, a minimum value appears in a quadratic differential value curve obtained by quadratic differentiating the current-voltage curve.

Description

Method for operating electrodialysis device having hydrocarbon anion-exchange membrane having ion-selective permeation characteristics Technical Field The present invention relates to a method for operating an electrodialysis device and an anion exchange membrane. Background Various techniques for recovering iodine from waste liquid have been developed so far. As such a technique, for example, a technique described in patent document 1 is known. In the waste liquid, divalent ions such as sulfate ions (SO 42-) may coexist in addition to iodine components such as iodide ions (I -). For example, sulfate ions are contained in the waste liquid at a concentration of usually 1g/L or more and less than the saturation solubility of sulfate, and more usually about 20 to 50 g/L. Patent document 1 describes a method in which a stock solution containing an inorganic anion having iodine and an inorganic anion having fluorine and contained in a desalting chamber is subjected to electrodialysis using a monovalent selective anion exchange membrane or the like (claim 1, example, etc. of patent document 1). Prior art literature Patent literature Patent document 1 Japanese patent application laid-open No. 2021-079318. Disclosure of Invention Problems to be solved by the invention However, as a result of the study by the present inventors, there is room for improvement in the productivity of iodide ions in the electrodialysis method described in patent document 1. That is, it has been known that an IV curve (current-voltage curve) representing the current-voltage characteristics of an anion exchange membrane is substantially straight in the case of a direct current. Therefore, even if the current density is increased in the electrodialysis method, the membrane voltage applied to the anion exchange membrane is proportionally increased, and thus it is considered that the productivity of iodide ions cannot be improved. Means for solving the problems The present inventors have studied the current-voltage characteristics in an anion-exchange membrane, and as a result, have found that, by appropriately controlling the monovalent selectivity by changing the compactness of the monovalent anion permselective layer in the anion-exchange membrane, etc., the IV curve of the anion-exchange membrane shows a new current-voltage characteristic in which the membrane voltage does not increase proportionally even if the current density is increased in an aqueous solution containing an iodide salt. As a result of intensive studies based on this knowledge, it has been found that, as an index indicating the above-mentioned current-voltage characteristics, the use of "a1/d" using the effective area d of the anion-exchange membrane and the value a1 of the direct current corresponding to the minimum value appearing in the quadratic differential value curve obtained by quadratic differentiating the IV curve can suppress the increase in membrane voltage even under the condition of a relatively high current density by setting the current density (a/dm 2) in the electrodialysis step to be "a1/d" or more, and therefore, the movement of iodide ions becomes easy, and the productivity (energy efficiency) of iodide ions can be improved as compared with the case where the IV curve is a straight line. According to one aspect of the present invention, the following method of operating an electrodialysis device is provided. 1. A method for operating an electrodialysis device, wherein, The method for operating an electrodialysis device includes a step of electrodialysis an iodide-containing solution containing an iodide salt and a solvent using the electrodialysis device, The electrodialysis device comprises an anion exchange membrane having a monovalent ion selective permeability layer, wherein the anion exchange membrane acquires an IV curve representing the relationship between DC current and voltage according to a DC resistance measurement method, and a minimum value appears in a secondary differential value curve obtained by subjecting the IV curve to secondary differentiation, In the electrodialysis step, when d is the effective area (dm 2) of the anion-exchange membrane and a1 is the value of the direct current (A) corresponding to the minimum value appearing in the secondary differential value curve, a1/d or more is the current density (A/dm 2). 2. The method of operating an electrodialysis device according to claim 1, wherein, The lower limit of a1/d is 0.5A/dm 2 or more. 3. The method of operating an electrodialysis device according to 1 or 2, wherein, The upper limit of a1/d is 10A/dm 2 or less. 4. The method of operating an electrodialysis device according to any one of 1 to 3, When a value of a direct current (A) corresponding to a maximum value appearing in a quadratic differential value curve obtained by quadratic differentiating the IV curve is a2 (where a2> a 1), The current density (A/dm 2) in the electrodialysis step is set to a2/d or less. 5. The