Operation method of electrodialysis device for aqueous solution containing organic solvent using electrodialysis device which is provided with anion exchange membrane manufactured by crosslinking polymerization method

Abstract

This operation method of an electrodialysis device includes an electrodialysis step for electrodialyzing an aqueous solution that contains halide ions and a polar organic solvent using an electrodialysis device which is provided with an anion exchange membrane manufactured by a crosslinking polymerization method. The aqueous solution contains 200 mg / L or more of iodide ions. In the electrodialysis step, if an electrodialysis test using a desalination liquid that contains iodide ions and sulfate ions is performed, the anion exchange membrane includes an anion exchange membrane with which TI / TSO4 is 3.5 or more, where TI is the transmission rate (%) of iodide ions (I-) and TSO4 is the transmission rate (%) of sulfate ions (SO4 2-) in the concentrated liquid, at the time when the residual ratio of iodide ions in the desalination liquid is 5%.

Description

Method for operating an electrodialysis apparatus for an aqueous solution containing an organic solvent using an electrodialysis apparatus equipped with an anion exchange membrane produced by crosslinking polymerization

[0001] The present invention relates to a method for operating an electrodialysis apparatus and an electrodialysis apparatus.

[0002] Various techniques have been developed for electrodialysis of wastewater containing iodine. For example, the technique described in Patent Document 1 is known as one of these techniques. － In addition to iodine components such as sulfate ions (SO ４ ２－ ) may also be present. For example, the wastewater typically contains sulfate ions at a concentration of 1 g / L or more but less than the saturated solubility of sulfate, more typically about 20 to 50 g / L. Patent Document 1 describes a method for performing electrodialysis on a raw solution that contains iodine-containing inorganic anions and fluorine-containing inorganic anions and is contained in a desalination compartment, using a monovalent selective anion exchange membrane or the like (see, for example, Claim 1 and Examples of Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2021-079318

[0004] However, as a result of investigations by the present inventors, it was found that the electrodialysis method described in Patent Document 1 has room for improvement in terms of the selective permeability of halide ions to organic solvents. That is, since it is generally known that ion exchange membranes are damaged by organic solvents, conventional electrodialysis methods have employed a pretreatment method in which the organic solvent (organic matter) contained in the wastewater is burned and removed before electrodialysis, as described in Patent Document 1. For these reasons, no sufficient research has been conducted on techniques for performing electrodialysis using ion exchange membranes in organic solvent-containing solutions.

[0005] The present inventors have conducted extensive research into electrodialysis methods for organic solvent-containing solutions and have found that the selective permeability of halide ions to organic solvents can be improved by employing an anion exchange membrane that is relatively solvent-resistant and by appropriately controlling the density of the ion-permselective layer in the anion exchange membrane.

[0006] Based on this finding, we conducted extensive research and obtained the following results. We found that anion exchange membranes produced by a cross-linking polymerization method are less soluble in organic solvents and have solvent resistance than anion exchange membranes produced by a casting method. The casting method is a technique in which an ion exchange resin is dissolved or dispersed in a solvent to prepare a casting solution, which is then cast onto a substrate film and dried. The anion exchange membranes produced by the casting method were partially dissolved in organic solvents and could not be used for electrodialysis.

[0007] The density of the ion selective permeation layer is measured by a predetermined electrodialysis test. ４ ２－ ) versus the transmittance of iodide ions (I － ) transmittance ratio (T Ｉ / T ＳＯ４ It was found that stable evaluation can be achieved by using T Ｉ / T ＳＯ４ It has been found that the selective permeability of halide ions to polar organic solvents can be increased by using a highly selective anion exchange membrane having a specific value or more.

[0008] According to one aspect of the present invention, there are provided the following method for operating an electrodialysis apparatus and an electrodialysis apparatus.

[0009] 1. A method for operating an electrodialysis apparatus, comprising an electrodialysis step of electrodialyzing an aqueous solution containing halide ions and a polar organic solvent using an electrodialysis apparatus equipped with an anion exchange membrane manufactured by a crosslinking polymerization method, wherein the aqueous solution contains 200 mg / L or more of iodide ions, and in the electrodialysis step, the anion exchange membrane is used to perform an electrodialysis test using a desalted solution containing iodide ions and sulfate ions, and ... － ) transmittance (%) is T Ｉ , sulfate ions (SO ４ ２－ ) transmittance (%) is T ＳＯ４ When defined as Ｉ / T ＳＯ４ 2. A method for operating an electrodialysis apparatus according to item 1., wherein in the electrodialysis step, the polar organic solvent comprises an organic solvent having a relative dielectric constant of 5 or more at 25°C. 3. A method for operating an electrodialysis apparatus according to item 1. or 2., wherein the aqueous solution comprises 0.1 mass % to 50 mass % of the polar organic solvent. 4. A method for operating an electrodialysis apparatus according to any one of items 1. to 3., wherein in the electrodialysis step, the concentration of halide ions in the desalted solution at the end point, as measured by an absorbance method, is 0.5 g / L to 5 g / L. 5. A method for operating an electrodialysis apparatus according to any one of items 1. to 4., wherein the iodide ions are converted into iodine (I ２ ), iodic acid (HIO ３ ), periodic acid (HIO ４), and iodine compounds. 6. A method for operating an electrodialysis device according to any one of 1. to 5., wherein the anion exchange membrane comprises a base substrate containing polyolefin and an ion-permselective layer formed on one or both sides of the base substrate. 7. A method for operating an electrodialysis device according to any one of 1. to 6., wherein in the electrodialysis step, the anion exchange membrane comprises an anion exchange membrane whose rate of change in ion exchange capacity before and after immersion treatment in a polar organic solvent with a concentration of 50% by weight is within ±5%. 8. A method for operating an electrodialysis device according to any one of 1. to 7., wherein in the electrodialysis step, the anion exchange membrane comprises an anion exchange membrane whose rate of change in water content, measured by the Karl Fischer method, before and after immersion treatment in isopropyl alcohol with a concentration of 50% by weight is within ±20%. 9. An electrodialysis apparatus for electrodialyzing an aqueous solution containing halide ions and a polar organic solvent, comprising: a concentration compartment; a deionization compartment; and an anion exchange membrane and a cation exchange membrane produced by a cross-linking polymerization method, which separate the concentration compartment from the deionization compartment; wherein the aqueous solution contains 200 mg / L or more of iodide ions; and wherein the anion exchange membrane is capable of electrodialyzing an aqueous solution containing iodide ions and sulfate ions, and wherein, when an electrodialysis test is carried out using a deionized solution containing iodide ions and sulfate ions, the anion exchange membrane is capable of electrodialyzing an aqueous solution containing iodide ions (I － ) transmittance (%) is T Ｉ , sulfate ions (SO ４ ２－ ) transmittance (%) is T ＳＯ４ When defined as Ｉ / T ＳＯ４ An electrodialysis device comprising an anion exchange membrane having a ρ of 3.5 or more.

[0010] According to the present invention, there are provided an operating method for an electrodialysis apparatus having excellent selective permeability of halide ions to organic solvents, and an electrodialysis apparatus.

[0011] It is a cross-sectional view showing an example of the configuration of an electrodialysis device of the present embodiment. It is a diagram showing an example of the configuration of an iodine recovery system of the present embodiment. It is a flow chart showing an example of an iodine recovery process of the present embodiment.

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all drawings, similar components are designated by similar reference numerals, and descriptions thereof will be omitted where appropriate. Furthermore, the drawings are schematic diagrams and do not correspond to actual dimensional proportions.

[0013] An outline of the method of operating the electrodialysis apparatus of this embodiment will be described.

[0014] The method for operating the electrodialysis apparatus of this embodiment includes an electrodialysis step of electrodialyzing an aqueous solution containing halide ions and a polar organic solvent using an electrodialysis apparatus equipped with an anion exchange membrane produced by a cross-linking polymerization method.

[0015] In this embodiment, the use of an anion exchange membrane manufactured by cross-linking polymerization method improves solvent resistance compared to anion exchange membranes manufactured by the casting method. In preliminary experiments, it was found that anion exchange membranes manufactured by the casting method were dissolved in a dimethylacetamide solvent with a concentration of approximately 50%. Furthermore, it is preferable that an electrodialysis device equipped with an anion exchange membrane manufactured by the cross-linking polymerization method also be equipped with a cation exchange membrane manufactured by the cross-linking polymerization method. Furthermore, polar organic solvents are highly miscible with water and are expected to reduce membrane damage to ion exchange membranes compared to nonpolar organic solvents.

[0016] According to this embodiment, it is possible to realize a method for operating an electrodialysis apparatus that exhibits excellent selective permeability of halide ions into a polar organic solvent. In one specific embodiment, one or more halide ions can be selectively permeated into a concentrated solution while the polar organic solvent remains in the aqueous solution (desalted solution).

[0017] In this embodiment, the halide ions may be, but are not limited to, iodide ions, chloride ions, fluoride ions, bromide ions, and the like. These may be used alone or in combination of two or more. Electrodialysis of an aqueous solution (desalted solution) containing halide ions and a polar organic solvent means (i) permeating at least one halide ion into a concentrated solution and / or (ii) leaving at least one halide ion in the desalted solution. When two or more halide ions with different mobilities are used during electrodialysis, it is possible to allow the species with relatively high mobility to permeate into the concentrated solution and the species with relatively low mobility to remain in the desalted solution. The order of mobility is iodide ions, bromide ions, chloride ions, and fluoride ions.

[0018] In the first operating method, at least iodide ions can be selectively permeated into the concentrate from an aqueous solution (demineralized solution) containing one or more types of halide ions. In the second operating method, iodide ions and chloride ions can be selectively permeated into the concentrate from an aqueous solution (demineralized solution) containing multiple types of halide ions. In the third operating method, fluoride ions can be selectively retained in an aqueous solution (demineralized solution) containing one or more types of halide ions. The operating methods of the electrodialysis apparatus of this embodiment may be used alone or in combination to achieve two or more of their effects.

[0019] In one example of the method of operating the electrodialysis apparatus of the present embodiment, when an electrodialysis test is carried out using a desalted solution containing iodide ions and sulfate ions, the anion exchange membrane is such that, when the iodide ion residual rate in the desalted solution is 5%, the iodide ion (I － ) transmittance (%) is T Ｉ , sulfate ions (SO ４ ２－ ) transmittance (%) is T ＳＯ４ When defined as Ｉ / T ＳＯ４ The anion exchange membrane includes an anion exchange membrane having a selectivity of 3.5 or more (highly selective anion exchange membrane).

[0020] Although the detailed mechanism is unclear, it is presumed that increasing the density of the surface of the anion exchange membrane improves its durability against polar organic solvents and maintains the functionality of the ion-selective permeability layer, thereby increasing the selective permeability of halide ions in polar organic solvents.

[0021] The above T of the anion exchange membrane Ｉ / T ＳＯ４ The lower limit of the T of the anion exchange membrane is 3.5 or more, preferably 5.0 or more, and more preferably 8.0 or more. This makes it possible to increase the selective permeability of iodide ions even in an environment containing a polar organic solvent. Ｉ / T ＳＯ４ The upper limit of is not particularly limited, but may be 300 or less, 200 or less, or 50 or less.

[0022] In the electrodialysis step, the aqueous solution may contain water together with the polar organic solvent. The lower limit of the content of the polar organic solvent contained in the aqueous solution is, for example, 0.1 mass% or more, preferably 0.5 mass% or more, and more preferably 1.0 mass% or more. On the other hand, the upper limit of the content of the polar organic solvent is, for example, 50 mass% or less, preferably 40 mass% or less, and more preferably 30 mass% or less. In this case, the solvent other than the polar organic solvent may be water in part or in whole. From the viewpoint of solubility in water, the number of carbon atoms of the polar organic solvent is preferably 3 or less.

[0023] The polar organic solvent is not particularly limited as long as it has a relative dielectric constant of 5 or more at 25°C, but examples thereof include alcohol-based solvents, amide-based solvents, ketone-based solvents, glycol-based solvents, nitrile-based solvents, sulfoxide-based solvents, and the like. These may be used alone or in combination of two or more. Examples of alcohol-based solvents include methyl alcohol, ethyl alcohol, isopropyl alcohol, and normal propyl alcohol. Examples of amide-based solvents include dimethylformamide, diethylformamide, dimethylacetamide, and N-methyl-2-pyrrolidone. Examples of ketone-based solvents include formic acid, acetic acid, propionic acid, oxalic acid, malonic acid, succinic acid, maleic acid, fumaric acid, adipic acid, formaldehyde, acetaldehyde, and propionaldehyde. Examples of glycol-based solvents include ethylene glycol and diethylene glycol. Examples of nitrile-based solvents include acetonitrile. Examples of sulfoxide-based solvents include dimethyl sulfoxide.

[0024] Examples of low dielectric organic solvents having a relative dielectric constant of 30 or less at 25° C. include alcohol solvents having 2 to 3 carbon atoms, such as isopropanol (IPA).

[0025] Examples of highly dielectric organic solvents having a relative dielectric constant of more than 30 at 25° C. include amide solvents having 1 to 3 carbon atoms, such as dimethylacetamide (DMAc) and dimethylformamide (DMF).

[0026] In the electrodialysis step, the polar organic solvent may contain the above polar organic solvent having a relative dielectric constant of more than 30 at 25°C and / or the above low-dielectric organic solvent having a relative dielectric constant of 30 or less at 25°C.

[0027] The method of operating the electrodialysis apparatus of this embodiment can employ the following modifications. Each modification may be employed in combination with one or more of the other modifications, provided that the effect of the invention is not impaired.

[0028] In another embodiment, the method for operating the electrodialysis apparatus includes the step of electrodialyzing the anion exchange membrane, the anion exchange membrane having a thickness swelling ratio of 104% or less, as measured according to the following procedure: (Measurement Procedure) The anion exchange membrane is immersed in a 50% by mass aqueous dimethylacetamide solution at a temperature of 40° C. for 1 hour, and the thickness of the anion exchange membrane is measured before and after the treatment. ０ , the thickness after treatment is D ５０ The obtained D ０ , D ５０ The thickness expansion rate of the ion exchange membrane is calculated using the formula: (D ５０ / D ０ ) × 100.

[0029] In another embodiment, the method of operating an electrodialysis apparatus is modified such that, in the electrodialysis step described above, the electrodialysis apparatus comprises a cation exchange membrane produced by a cross-linking polymerization method, the cation exchange membrane having a thickness swelling ratio of 104% or less as measured according to the above-described measurement procedure.

[0030] According to the findings of the inventors, it has been found that the swelling property of an anion exchange membrane in an organic solvent can be stably evaluated by using the rate of change in membrane thickness (thickness swelling ratio) before and after immersion in a 50% by mass aqueous dimethylacetamide solution as an indicator, and that the selective permeability of halide ions in polar organic solvents can be increased by setting the thickness swelling ratio to the above-mentioned upper limit or less.

[0031] Although the detailed mechanism is unclear, it is presumed that the anion exchange membrane, which is difficult to swell in polar organic solvents, maintains the function of the ion permselective layer, thereby increasing the permselectivity of halide ions in polar organic solvents.

[0032] The upper limit of the thickness swelling ratio of the anion exchange membrane is 104% or less, preferably 103% or less, and more preferably 102% or less. This allows stable electrodialysis in an environment containing a polar organic solvent. The lower limit of the thickness swelling ratio of the anion exchange membrane is not particularly limited, but is, for example, 96% or more, preferably 98% or more, and more preferably 99% or more.

[0033] The upper limit of the thickness swelling ratio of the cation exchange membrane is, for example, 104% or less, preferably 103% or less, and more preferably 102% or less. This allows stable electrodialysis in an environment containing a polar organic solvent. The lower limit of the thickness swelling ratio of the cation exchange membrane is not particularly limited, but is, for example, 96% or more, preferably 98% or more, and more preferably 99% or more.

[0034] Here, according to the findings of the inventors, it has been found that by appropriately controlling the content of components that are easily soluble in polar solvents and by appropriately controlling polymerization conditions such as suppressing the remaining unreacted components during production by a cross-linking polymerization method, it is possible to set the thickness swelling ratio of the anion exchange membrane or cation exchange membrane within the desired numerical range.

[0035] According to the findings of the present inventors, the SO measured under the following predetermined conditions ４ Although the mechanism is not clear, it has been found that by using the index as an indicator, the degree of density in the surface dense layer (ion-selective permeable layer) of the anion exchange membrane can be stably evaluated. ４ By appropriately controlling the index, the above T Ｉ / T ＳＯ４ It becomes possible to set the value in a desired range.

[0036] In another variant, it is preferred to use an anion exchange membrane with monovalent selectivity.

[0037] In another modified example, in the electrodialysis step, the anion exchange membrane may include an anion exchange membrane whose ion exchange capacity changes by within ±5% before and after immersion treatment in a polar organic solvent having a concentration of 50% by mass.

[0038] In another modified example, in the electrodialysis step, the anion exchange membrane may include an anion exchange membrane whose water content, as measured by the Karl Fischer method, changes by ±20% or less before and after an immersion treatment in 50% by mass of isopropyl alcohol.

[0039] The electrodialysis apparatus of this embodiment is an electrodialysis apparatus that separates an aqueous solution containing halide ions and a polar organic solvent into a concentrated solution containing halide ions and a desalted solution containing a polar organic solvent, and is equipped with a concentration compartment, a desalting compartment, and an anion exchange membrane and a cation exchange membrane that separate the concentration compartment from the desalting compartment. ４ ２－ ) versus the transmittance of iodide ions (I － ) transmittance ratio (T Ｉ / T ＳＯ４ The electrodialysis device may further comprise an anion exchange membrane that satisfies the above "thickness swelling ratio" and / or a cation exchange membrane that satisfies the above "thickness swelling ratio."

[0040] The anion exchange membrane of the present embodiment is an anion exchange membrane used for electrodialysis in a polar organic solvent, specifically, an anion exchange membrane used for electrodialysis of an aqueous solution containing halide ions and a polar organic solvent. An anion exchange membrane that can be used in a polar organic solvent environment is an anion exchange membrane that can be used for electrodialysis of an aqueous solution containing halide ions and a polar organic solvent. ４ ２－ ) versus the transmittance of iodide ions (I － ) transmittance ratio (T Ｉ / T ＳＯ４ ) and / or is configured to satisfy the above-mentioned "thickness swelling ratio."

[0041] In this specification, the SO in the anion exchange membrane ４ The index can be measured in accordance with the following seawater concentration test. <Seawater concentration test> A small electrodialysis device (current-carrying membrane area 100 cm) was used. ２ ) with a membrane resistance of 1.5 Ω cm ２ 2.5Ω・cm or more ２The following cation exchange membranes are used as a pair, and the monovalent selective surface of the anion exchange membrane to be evaluated is assembled so that it faces the deionization compartment. The operating conditions are as follows: seawater at 25°C flows through the deionization compartment at a flow rate of 6 cm / sec, the concentration compartment is filled with a 3.5 mol / L NaCl aqueous solution, and the current density is 3 A / dm ２ Electrodialysis was performed for 5 hours or more (until the concentration in the concentration compartment stopped changing) to measure the amount of chloride ions (Cl － ) concentration (N) and sulfate ions (SO ４ ２－ ) concentration (10 －３ The obtained sulfate ion concentration is measured using the above SO ４ Let it be an index.

[0042] Here, the selectivity of monovalent anions and divalent anions permeating the membrane in a monovalent selective anion exchange membrane is as follows: － On the other hand, SO is used as a divalent anion. ４ ２－ The selective permeability coefficient (P Ｃｌ ＳＯ４ This is because monovalent selective anion exchange membranes are mainly used for concentrating seawater in the salt manufacturing industry, and in this application, the permselectivity coefficient (P Ｃｌ ＳＯ４ ) by using a small membrane, － Therefore, even in the case of recovering iodine, if an anion exchange membrane with monovalent selectivity is used to avoid the concentration of sulfate ions, it is preferable to use an anion exchange membrane with monovalent selectivity. － and SO ４ ２－ However, according to the investigations of the present inventors, in the case of iodine recovery, it is common to use a material whose physical property value is as small as possible in the selective permeability defined in relation to the coefficient of selective permeability (P Ｃｌ ＳＯ４ ) is used, the iodide ions and SO ４ ２－ The permeation behavior of the Cl － and SO ４ ２－It was discovered that there was an unexpected difference between the permeation of iodide ions and that iodide ions could not be concentrated at a sufficiently high permeation rate. Further research revealed that the "SO ４ When the "index" was used as an indicator of iodide ion permeability, it was unexpectedly found to correlate well with the amount of iodide ion permeated, despite the fact that iodide ions are monovalent anions.

[0043] In this embodiment, for example, by appropriately selecting the type and amount of each component contained in the monovalent ion selective anion exchange membrane, the method for preparing the monovalent ion selective permeation layer, etc., the above SO ４ As will be described in detail later, for example, the SO 2 index can be controlled by appropriately controlling the density of the surface dense layer of the anion exchange membrane. ４ This is one factor for setting the index to a desired numerical range.

[0044] Here, the monovalent selective anion exchange membranes have been used to selectively permeate monovalent anions from a treatment liquid containing a mixture of monovalent anions and polyvalent anions, and therefore, membranes with as high a monovalent selectivity as possible have been used. ４ When measuring the index, the transmittance is as small as possible. Specifically, 3.0 × 10 －３ In most cases, values ​​below N were used.

[0045] In this situation, as described above, the present invention ４ The index is 3.0 x 10 －３ N or more 50.0×10 －３ It is preferable to use a monovalent selective anion exchange membrane having a SO 2 concentration of 0.01% or less. ４ The lower limit of the index is, for example, 3.0 x 10 －３ N or more, preferably 5.0 × 10 －３ N or more, more preferably 6.0 × 10 －３N or more. This increases the efficiency of concentrating iodide ions during electrodialysis. －３ By setting the concentration of iodide ions at 0.05 N or more, it is possible to suppress the decrease in the concentration efficiency of iodide ions even when electrodialysis is repeated. The reason for this is not entirely clear, but it is thought to be due to the interaction between iodide ions and the ion permeation channels in the membrane. On the other hand, the SO 2 concentration in the monovalent selective anion exchange membrane is ４ The upper limit of the index is, for example, 50.0 x 10 －３ or less, preferably 30.0 × 10 －３ N or less, more preferably 20.0 × 10 －３ This makes it possible to suppress the concentration of divalent ions such as sulfate ions to a low level. In other words, the recovery ratio of iodide ions to multivalent ions such as divalent ions can be increased.

[0046] Here, the monovalent selective anion exchange membrane is a membrane that selectively exchanges monovalent anions such as SO ４ ２－ Cl is preferred over divalent ions such as － Generally, the anion exchange membrane is an anion exchange membrane that selectively allows the permeation of monovalent ions, such as SO ４ ２－ and Cl － The selective permeability coefficient (P Ｃｌ ＳＯ４ ) is 0.01 to 1.0, but even among them, the SO ４ Since it is easy to obtain a monovalent selective anion exchange membrane used in the anion exchange membrane 7 that satisfies the specified value of the index, the selective permeability coefficient (P Ｃｌ ＳＯ４ ) is preferably 0.06 to 0.90, particularly preferably 0.11 to 0.37.

[0047] Such monovalent anion selectivity can be imparted by forming a monovalent ion permselective layer on at least one surface of the anion exchange membrane. The specific configuration of the monovalent ion permselective layer is not particularly limited, but it is preferably at least one layer selected from the group consisting of a dense surface layer, an electrically neutral layer, and an oppositely charged layer. The "dense surface layer" refers to a surface portion of the anion exchange membrane having a dense structure (e.g., a layer with a high degree of cross-linking or a layer with a high fixed ion concentration on the surface portion), the "electrically neutral layer" refers to a thin electrically neutral layer containing no anion exchange groups formed on the surface of the anion exchange membrane, and the "oppositely charged layer" refers to a thin layer with cation exchange groups formed on the surface of the anion exchange membrane.

[0048] The monovalent selective anion exchange membrane may be, for example, a base anion exchange membrane having the SO 2 -containing anion exchange membrane on one or both sides thereof. ４ The index is 3.0 x 10 －３ N or more 50.0×10 －３ The monovalent ion selective permeable layer may be at least one layer selected from the group consisting of a dense surface layer, an electrically neutral layer, and an oppositely charged layer. ４ A dense surface layer is preferred because it is easy to obtain an anion exchange membrane with a high index, and a dense surface layer formed of a highly crosslinked resin layer using a divalent amine compound is particularly preferred. As the base anion exchange membrane, one in which a quaternary ammonium group, which is a strongly basic anion exchange group, is introduced into the basic skeleton of a styrene-divinylbenzene copolymer is preferably used because it has a strong structure and is easy to form a monovalent ion permselective layer.

[0049] These, SO ４A monovalent selective anion exchange membrane having an index that satisfies the above numerical range can be produced as follows: That is, a divalent amine compound is brought into contact with one or both membrane surfaces of a raw membrane for introducing anion exchange groups, which is obtained by polymerizing a polymerizable composition containing a styrene-based aromatic polymerizable monomer having a halogenoalkyl group and a crosslinkable polymerizable monomer such as divinylbenzene, to form SO on the membrane surface. ４ The index is 3.0 x 10 －３ N or more 50.0×10 －３ This method involves forming a surface dense layer that is more highly crosslinked than the interior with an amount of formation that is less than N, and then contacting the remaining halogenoalkyl groups in the membrane with trialkylamine to convert them into quaternary ammonium groups. According to this method, in the raw membrane for introducing anion exchange groups, a certain proportion of the halogenoalkyl groups present in the membrane surface portion on one side is consumed for crosslinking by contact with a divalent amine compound. Therefore, the membrane surface portion becomes a dense structure due to crosslinking, and SO ４ ２－ The permeability of ions and the like decreases, and selectivity for monovalent anions is exhibited.

[0050] In this method, any known styrene-based aromatic polymerizable monomer having a halogenoalkyl group can be used without limitation. The alkyl group preferably has 1 to 8 carbon atoms, and examples of the halogen atom substituted thereon include chlorine, bromine, and iodine. Examples of such a halogenoalkyl group include a chloromethyl group, a bromomethyl group, an iodomethyl group, a chloroethyl group, a bromoethyl group, an iodoethyl group, a chloropropyl group, a bromopropyl group, an iodopropyl group, a chlorobutyl group, a bromobutyl group, an iodobutyl group, a chloropentyl group, a bromopentyl group, an iodopentyl group, a chlorohexyl group, a bromohexyl group, and an iodohexyl group. Specific examples of aromatic polymerizable monomers having such a halogenoalkyl group include chloromethylstyrene, bromomethylstyrene, iodomethylstyrene, chloroethylstyrene, bromoethylstyrene, iodoethylstyrene, chloropropylstyrene, bromopropylstyrene, iodopropylstyrene, chlorobutylstyrene, bromobutylstyrene, iodobutylstyrene, chloropentylstyrene, bromopentylstyrene, iodopentylstyrene, chlorohexylstyrene, bromohexylstyrene, and iodohexylstyrene. Of these, it is particularly preferable to use chloromethylstyrene, bromomethylstyrene, iodomethylstyrene, chloroethylstyrene, bromoethylstyrene, iodoethylstyrene, chloropropylstyrene, bromopropylstyrene, iodopropylstyrene, chlorobutylstyrene, bromobutylstyrene, and iodobutylstyrene.

[0051] The base membrane for introducing anion exchange groups obtained by polymerizing the polymerizable composition contains halogenoalkyl groups derived from the aromatic polymerizable monomer having the halogenoalkyl group. These halogenoalkyl groups are converted into anion exchange groups, i.e., quaternary ammonium groups, as described below. Such quaternary ammonium groups are strongly basic and are excellent anion exchange groups. However, if the presence of other anion exchange groups is desired, the polymerizable composition may contain, in addition to the aromatic polymerizable monomer having the halogenoalkyl group, a polymerizable monomer having another anion exchange group or a polymerizable monomer having a functional group capable of introducing other anion exchange groups. Such anion exchange groups other than quaternary ammonium groups are not particularly limited as long as they are functional groups capable of becoming positively charged in aqueous solution, and examples thereof include primary, secondary, and tertiary amino groups, pyridyl groups, imidazole groups, and quaternary pyridinium groups. In the polymerizable composition, the amount of these polymerizable monomers having other anion exchange groups or polymerizable monomers having functional groups into which other anion exchange groups can be introduced is not particularly limited, but is preferably 100 parts by mass or less, and more preferably 50 parts by mass or less, per 100 parts by mass of the aromatic polymerizable monomer having a halogenoalkyl group.

[0052] Furthermore, in addition to the polymerizable monomer for introducing anion exchange groups into the anion exchange membrane, the polymerizable composition may contain a polymerizable monomer that is not directly involved in the introduction of such an anion exchange membrane, in an amount of 150 parts by mass or less per 100 parts by mass of the aromatic polymerizable monomer having a halogenoalkyl group. Examples of such polymerizable monomers that are not directly involved in the introduction of anion exchange membranes include styrene, acrylonitrile, methylstyrene, ethylvinylbenzene, acrolein, methylvinylketone, and vinylbiphenyl.

[0053] In the polymerizable composition, the amount of the polymerizable monomer that is not directly involved in the introduction of these anion exchange membranes is not particularly limited, but is preferably 400 parts by mass or less, and more preferably 150 parts by mass or less, per 100 parts by mass of the aromatic polymerizable monomer having a halogenoalkyl group.

[0054] A crosslinkable polymerizable monomer is used in the polymerizable composition to increase the density of the resulting anion exchange membrane and thereby enhance its strength. As such a crosslinkable polymerizable monomer, any monomer known in the art for producing ion exchange membranes can be used without any particular limitation. Specific examples include m-, p-, or o-divinylbenzene, divinylbiphenyl, divinylsulfone, butadiene, chloroprene, isoprene, trivinylbenzene, divinylnaphthalene, diallylamine, triallylamine, divinylpyridine, and polyfunctional vinylbenzyl compounds having three or more vinylbenzyl groups, as disclosed in, for example, JP-A-62-205153.

[0055] If these crosslinkable polymerizable monomers are blended in too much relative to the styrene-based aromatic polymerizable monomer having a halogenoalkyl group, the ion exchange capacity of the anion exchange membrane will decrease and the degree of crosslinking will become too high, increasing the membrane resistance and potentially reducing the iodine concentration efficiency. Conversely, if the blending ratio of the crosslinkable polymerizable monomer is too low, not only will the strength of the membrane decrease, but the density of the highly crosslinked resin layer provided on the membrane surface will not increase, potentially preventing sufficient monovalent selectivity from being obtained. For these reasons, it is preferable to blend 2 to 20 parts by mass, preferably 3 to 15 parts by mass, of the crosslinkable polymerizable monomer relative to 100 parts by mass of the polymerizable monomer component consisting of the aromatic polymerizable monomer having a halogenoalkyl group and the other polymerizable monomers used in combination as necessary as described above.

[0056] A polymerization initiator is usually blended into the polymerizable composition. Any conventionally known polymerization initiator can be used without any particular limitation, and may be appropriately selected taking into consideration the substrate to be used, molding conditions, etc. Specific examples include p-menthane hydroperoxide, diisopropylbenzene hydroperoxide, α,α'-bis(tert-butylperoxy-m-isopropyl)benzene, di-tert-butyl peroxide, tert-butyl hydroperoxide, di-tert-amyl peroxide, tert-butylcumyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane ... ) Hexyne-3, cumene hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, 2,5-dimethyl-2,5-dihydroperoxyhexane, 2,5-dimethyl-2,5-dihydroperoxyhexyne-3, benzoyl peroxide, methyl ethyl ketone peroxide, methyl isobutyl ketone peroxide, cyclohexane peroxide, methylcyclohexane peroxide, isobutyl peroxide, 2,4-dichlorobenzoyl peroxide, o-methylbenzoyl peroxide peroxide, bis-3,5,5-trimethylhexanoyl peroxide, lauroyl peroxide, p-chlorobenzoyl peroxide, 1,1-di-tert-butylperoxy-trimethylcyclohexane, 1,1-di-tert-butylperoxycyclohexane, 2,2-di-(tert-butylperoxy)-butane, 4,4-di-tert-butylperoxyvaleric acid-n-butyl ester, 2,4,4-trimethylpentylperoxy-phenoxyacetate, α-cumylperoxyneodene Preferred are tert-butylperoxybenzoate, tert-butylperoxyneodecanoate, tert-butylperoxypivalate, tert-butylperoxy-2-ethylhexanoate, tert-butylperoxyisobutyrate, di-tert-butylperoxyhexahydroterephthalate, di-tert-butylperoxyazelate, tert-butylperoxy-3,5,5-trimethylhexanoate, tert-butylperoxyacetate, and tert-butylperoxybenzoate.These may be added to the monomer paste alone or in combination of two or more. The amount of the polymerization initiator used is usually preferably 0.1 to 30 parts by mass, more preferably 1 to 10 parts by mass, per 100 parts by mass of the polymerizable monomer component.

[0057] The polymerizable composition may also contain a matrix resin as a viscosity modifier. The incorporation of such a matrix resin can improve the coatability of the polymerizable composition and prevent sagging and other problems when applied to a substrate. Examples of such matrix resins include saturated aliphatic hydrocarbon polymers such as polyvinyl chloride, chlorinated polyvinyl chloride, ethylene-vinyl chloride copolymers, vinyl chloride elastomers, chlorinated polyethylene, chlorosulfonated polyethylene, ethylene-propylene copolymers, and polybutylene; styrene polymers such as styrene-butadiene copolymers; and copolymers of these with styrene monomers such as vinyltoluene, vinylxylene, chlorostyrene, chloromethylstyrene, α-methylstyrene, α-halogenated styrene, and α,β,β'-trihalogenated styrene; monoolefins such as ethylene and butylene; and conjugated diolefins such as butadiene and isoprene. Also suitable for use are styrene-butadiene rubber or hydrogenated rubber thereof, nitrile rubber or hydrogenated nitrile rubber thereof, pyridine rubber or hydrogenated rubber thereof, and styrene-based thermoplastic elastomers. Here, the term "styrene-based thermoplastic elastomer" refers to polystyrene polymer, styrene and polybutadiene, polyisoprene, vinyl polyisoprene, ethylene-butylene alternating copolymer, and ethylene-propylene alternating copolymer. Examples include polystyrene-hydrogenated polybutadiene-polystyrene copolymer, polystyrene-(polyethylene / butylene rubber)-polystyrene copolymer, polystyrene-hydrogenated polyisoprene rubber-polystyrene copolymer, polystyrene-(polyethylene / propylene rubber)-polystyrene copolymer, polystyrene-polyethylene-(polyethylene / propylene rubber)-polystyrene copolymer, and polystyrene-vinyl polyisoprene-polystyrene copolymer. The molecular weight of such matrix resins is not particularly limited, but is preferably in the range of 1,000 to 1,000,000, and more preferably 50,000 to 500,000.The matrix resin is blended into the polymerizable composition in an amount that ensures an appropriate viscosity, depending on the molecular weight. For example, the amount is preferably 1 to 50 parts by mass, and more preferably 3 to 15 parts by mass, per 100 parts by mass of the polymerizable monomer component.

[0058] In addition to the various components described above, the polymerizable composition may contain, if necessary, a plasticizer such as dioctyl phthalate, dibutyl phthalate, tributyl phosphate, styrene oxide, or an alcohol ester of a fatty acid or an aromatic acid, an organic solvent, or the like.

[0059] It is also preferable to add a compound having one or more epoxy groups, such as styrene oxide or diethylene glycol diglycidyl ether, to the polymerizable composition so as to capture halogen gas or hydrogen halide gas generated by thermal decomposition of the styrene-based aromatic polymerizable monomer having a halogenoalkyl group.

[0060] The polymerizable composition comprising the above components is filled into the voids of a substrate serving as a reinforcing material and then polymerized to obtain a base membrane for introducing anion exchange groups. Any known substrate for ion exchange membranes may be used as the substrate. Generally, a support material with a porosity of 20 to 90%, more preferably 40 to 80%, and even more preferably 45 to 55% is used. Examples include woven fabrics, nonwoven fabrics, porous films, and net-like materials formed from polyvinyl chloride, polyolefins, and the like. Among these, polyolefins such as polypropylene and polyethylene are preferred in terms of affinity with ion exchange resins and chemical resistance, with polyethylene being particularly preferred. Furthermore, the use of a porous film as the substrate shape is preferred because it enhances the efficiency of iodine concentration after imparting monovalent selectivity. The thickness of the substrate is generally selected within the range of 50 to 300 μm, with 70 to 250 μm being preferred from the viewpoints of membrane resistance and strength retention.

[0061] The method for filling the substrate with the polymerizable composition is not particularly limited. For example, the polymerizable composition may be applied or sprayed onto the substrate, or the substrate may be immersed in the polymerizable composition. When the polymerizable composition is in a paste form, application is preferred. The application of the polymerizable composition to the substrate can be carried out by known means such as a roll coater, a flow coater, a knife coater, a comma coater, spraying, or dipping.

[0062] After the polymerizable composition is introduced into the substrate as described above, the substrates are laminated together with a release material having releasability so as to prevent the substrates from adhering to each other, and then wound up on a roller, and heated to carry out polymerization.

[0063] The release material used should have heat resistance sufficient to withstand polymerization and be easily peeled off after polymerization. Examples include polyolefins such as polypropylene, poly-1-butene, poly-4-methyl-1-pentene, or random or block copolymers of α-olefins such as ethylene, propylene, 1-butene, and 4-methyl-1-pentene; ethylene-vinyl compound copolymers such as ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, and ethylene-vinyl chloride copolymer; polyvinyl compounds such as polymethyl acrylate and polymethyl methacrylate; polyamides such as nylon 6, nylon 6-6, nylon 6-10, nylon 11, and nylon 12; thermoplastic polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polycarbonate; polyphenylene oxide; biodegradable resins such as polylactic acid; and mixtures thereof. These films may be biaxially stretched. In other words, an appropriate film can be selected from the above films depending on the type of monomer component in the polymerizable composition and used as the release material. In particular, polyester films such as polyethylene terephthalate (PET) are most suitable in terms of heat resistance and releasability.

[0064] The pressure during polymerization may be either normal pressure or pressure, and is generally about 0.1 to 1.0 MPa. The polymerization temperature may be any temperature lower than the melting point of the substrate, and is generally in the range of 40 to 130°C. That is, by carrying out polymerization by heating within this temperature range, a portion of the substrate dissolves in the polymerizable composition, and polymerization is carried out in this state. As a result, the bonding strength between the ion exchange resin and the substrate can be increased, and the membrane strength and concentration efficiency can be further improved. The polymerization time varies depending on the polymerization temperature, etc., but is generally about 3 to 20 hours.

[0065] After applying the polymerizable composition to the substrate as described above, the composition is heated to polymerize, thereby obtaining a base membrane for introducing anion exchange groups, which is made of a membranous polymer. To obtain a monovalent selective anion exchange membrane of the present invention, after obtaining the base membrane for introducing anion exchange groups in this manner, a monovalent ion permselective layer made of a highly cross-linked resin layer is formed on the membrane surface before the anion exchange groups are introduced. This is carried out, for example, by contacting one side of the membrane surface for introducing anion exchange groups with a divalent amine compound. That is, if the monovalent anion selective layer is formed only on one side of the base membrane for introducing anion exchange groups, the other membrane surface is covered with a film or the like, and the membrane surface on the side not covered with the film is contacted with a divalent amine compound, thereby forming a highly cross-linked resin layer on the membrane surface, rather than the interior.

[0066] The amino group of the divalent amine compound reacts with the halogenoalkyl group contained in the base membrane for introducing anion exchange groups, resulting in the elimination of hydrogen chloride and the formation of a C-N bond. In the divalent amine compound, this reacts with two halogenoalkyl groups to form a crosslinked structure. The denser this crosslinked structure is, the higher the membrane resistance becomes, while the monovalent anion selectivity becomes higher, resulting in the SO ４The index becomes smaller. In addition, the crosslinking reaction by the divalent amine compound proceeds from the membrane surface toward the inside, and the deeper the crosslinking depth, the higher the monovalent anion selectivity but the greater the membrane resistance. Examples of secondary amine compounds include dimethylamine, diethylamine, dipropylamine, dibutylamine, and diethanolamine. In terms of the balance between resistance and monovalent anion selectivity, the shorter the substituent, the better, and dimethylamine is preferred.

[0067] When contacting the anion-exchange-group-introduced base membrane with a secondary amine compound solution to crosslink the halogenoalkyl groups on the surface of the base membrane, if the divalent amine compound diffuses too slowly into the anion-exchange-group-introduced base membrane in an aqueous solution or if the solubility is poor, a portion of the water may be replaced with an organic solvent to adjust the diffusion rate and improve solubility. In this case, hydrophilic solvents such as methanol, ethanol, 1-propanol, 2-propanol, and acetone can be used as the organic solvent to replace water. The content of the organic solvent is preferably within 30% by mass, particularly 5 to 15% by mass, relative to the water.

[0068] The SO ４ The index is 3.0 x 10 －３ N or more 50.0×10 －３ In order to obtain an anion exchange membrane having a surface density of N or less, the conditions for contacting and reacting the secondary amine compound are particularly important. For example, the concentration at which the secondary amine compound is dissolved is preferably 0.01 mol / L to 2 mol / L, and particularly preferably 0.03 mol / L to 1 mol / L. If the concentration is too low, the crosslinking reactivity of the halogenoalkyl group with the divalent amine compound decreases, resulting in a decrease in monovalent ion selectivity and an increase in SO ４ On the other hand, if the concentration is too high, the anion exchange group introduction base membrane will diffuse more into the interior of the membrane, the cross-linking depth will be too deep, and the SO ４ The index becomes less than the predetermined value.

[0069] The reaction temperature during contact with the divalent amine compound is 20 to 50°C, and the reaction time is 1 to 24 hours. If the reaction temperature is below 20°C and / or the reaction time is less than 1 hour, the crosslinking reaction of the halogenoalkyl group cannot be sufficiently carried out, and the SO ４ If the reaction temperature exceeds 50°C and / or the reaction time exceeds 24 hours, the anion exchange group introduction raw membrane will diffuse into the interior of the membrane, the crosslinking depth will be too deep, and the SO ４ After the raw membrane for introducing anion exchange groups is reacted with the secondary amine compound, washing may be carried out to remove excess secondary amine compound that has not been subjected to the reaction.

[0070] The reaction between the divalent amine compound and a halogenoalkyl group as described above may terminate at the reaction between the divalent amine and one halogenoalkyl group, failing to result in crosslinking between the two halogenoalkyl groups. In such cases, it is preferable to perform a treatment step with an alkaline aqueous solution (alkaline aqueous solution treatment step) after the contact step with the divalent amine compound. Although the details of the reaction are not fully understood, it is presumed that the alkaline compound neutralizes the hydrogen chloride produced when the divalent amine compound reacts with one halogenoalkyl group, thereby promoting the reaction with the second halogenoalkyl group. Known alkaline aqueous solutions, such as aqueous sodium hydroxide, aqueous potassium hydroxide, aqueous barium hydroxide, and aqueous ammonia, can be used. Strongly basic aqueous sodium hydroxide or aqueous potassium hydroxide solutions are preferred because they enable more efficient treatment. The alkaline aqueous solution may have a pH of 8 to 14 at 25°C, but a pH of 10 to 14 at 25°C is preferred because it enables more efficient treatment. The treatment temperature is preferably 50 to 70°C, more preferably 55 to 65°C. If the temperature is less than 50°C, the treatment takes a long time, resulting in low productivity. If the temperature is more than 70°C, the treatment becomes too harsh, and there is a possibility that the amino compound that has reacted once may be liberated. The treatment time with the alkaline aqueous solution in this step may be 4 to 24 hours, preferably 6 to 12 hours, and more preferably 6 to 10 hours. If the temperature is less than 4 hours, the treatment may be insufficient. If the temperature is more than 24 hours, the treatment becomes too harsh, resulting in an increase in electrical resistance.

[0071] Next, a step (quaternary ammonium group introduction step) is carried out in which quaternary ammonium groups are introduced using a tertiary amine compound to the residual halogenoalkyl groups in the raw membrane after the alkaline aqueous solution treatment step. Examples of tertiary amine compounds include trimethylamine, triethylamine, N,N-dimethylpropylamine, and N-ethyl-N-methylbutylamine. From the viewpoint of resistance, trimethylamine is preferred. By contacting the membrane with an aqueous solution of a tertiary amine compound and introducing quaternary ammonium groups, the residual halogenoalkyl groups present in the membrane from the surface to the interior are substituted without affecting the monovalent anion selective layer consisting of a highly crosslinked resin layer. This method may be performed in accordance with conventional methods for introducing quaternary ammonium groups in the production of anion exchange membranes.

[0072] By the above method, SO ４ The index is 3.0 x 10 －３ N or more 50.0×10 －３ Furthermore, in order to exhibit appropriate permeability to iodide ions, the monovalent selective anion exchange membrane used in the present invention preferably has an anion exchange capacity in the range of 0.5 to 4.0 meq / g-dry membrane, particularly 0.8 to 3.0 meq / g-dry membrane, a water content in the range of 10 to 40%, preferably 25 to 35%, and an electrical resistance of 1.2 Ω cm ２ 3.0Ω・cm or more ２ Preferably 1.7 Ω cm or less ２ 2.5Ω・cm or more ２ or less, more preferably 1.8 Ω cm ２ 2.4Ω・cm or more ２ The thickness is preferably in the following range. The thickness is adjusted to be in the range of 50 to 320 μm, particularly 70 to 280 μm. That is, in order to obtain such physical properties, the composition of the polymerizable composition (amount or type of monomer component and crosslinking agent), the thickness of the substrate, and the crosslinking reaction conditions by the divalent amine compound are appropriately set. In addition, the concentration of chloride ions (Cl ) in a seawater concentration test is － The permeation rate is usually 3.2 mol / L or more, preferably 3.5 mol / L or more.

[0073] The configuration of the method for operating the electrodialysis apparatus of this embodiment will be described in detail below.

[0074] In this embodiment, the halide ion may be, but is not limited to, an iodide ion, a chloride ion, a fluoride ion, a bromide ion, or the like. Among these, the iodide ion (I － In the following example, the case where iodide ions are used will be described.

[0075] Fig. 1 is a cross-sectional view schematically showing an example of the configuration of an electrodialysis apparatus 1. Fig. 2 is a diagram schematically showing an example of the configuration of an iodine recovery system 100. Fig. 3 is a flow chart showing an example of an iodine recovery process.

[0076] An example of a method for recovering iodine using the method for operating an electrodialysis apparatus according to the present embodiment includes an electrodialysis step in which an aqueous solution (waste liquid 10) containing iodide ions and a polar organic solvent is separated into an iodine-containing concentrate (concentrate 20) and a desalted solution (desalted solution 30) using the electrodialysis apparatus 1 shown in FIG.

[0077] The iodine recovery system 100 shown in FIG. 2 is only required to include at least a facility for supplying the waste liquid 10 to the electrodialysis apparatus 1, and further includes a facility for treating the concentrated solution 20 and / or the desalted solution 30 produced in the electrodialysis apparatus 1.

[0078] The waste liquid 10 (raw liquid) is not particularly limited as long as it is a liquid containing at least an iodine component including an iodide salt and a polar organic solvent, but examples thereof include waste liquid discharged from the manufacturing process of a product containing an iodine component, waste liquid discharged when a product containing an iodine component is disposed of, waste liquid discharged from a synthesis process using an iodine component as a reaction catalyst, and waste liquid from a cleaning solution used to clean manufacturing equipment that uses an iodine component.

[0079] Specific examples of raw materials for the waste liquid 10 include waste liquids, waste powders, and waste solids from the manufacturing process, manufacturing equipment, or waste products of any of the iodine-containing products, such as polarizing films, contrast agents, disinfectants, and radiation-related materials, or waste liquids or waste solids containing iodine catalysts (organic iodine compounds or inorganic iodine compounds) used in chemical synthesis, such as the synthesis of pharmaceuticals, including antibiotics and antiviral agents. These may be used alone or in combination of two or more.

[0080] The iodine component is, for example, iodide ion (I － ) is sufficient, and iodine (I ２ ), iodic acid (HIO ３ ), periodic acid (HIO ４ The term "iodine waste" is defined as including wastewater that has been subjected to reduction treatment of one or more selected from the group consisting of iodine compounds, iodides (including inorganic iodine compounds and organic iodine compounds), and iodides (including inorganic iodine compounds and organic iodine compounds). Among the iodine components, wastewater derived from the raw materials and the like typically contains iodide ions at a concentration of 3% or more, preferably about 3% to 30%. Furthermore, these wastewaters typically contain sulfate ions at a concentration of 1 g / L or more but not exceeding the saturated solubility of sulfate, more typically about 20 to 50 g / L. Furthermore, solids containing iodine components typically contain elemental iodine at a concentration of about 30% to 99.8% by mass.

[0081] The waste liquid 10 may be used as is, but if necessary, may be subjected to chemical or physical pretreatment such as pH adjustment, dilution, decomposition and removal of organic matter.

[0082] As shown in Fig. 1, electrodialysis device 1 has concentrating compartment 2, deionization compartment 3, an ion exchange membrane separating concentrating compartment 2 from deionization compartment 3, anode 4, cathode 5, and power supply 6. Electrodialysis device 1 is not limited to the configuration shown in Fig. 1 and may have any known device configuration.

[0083] An electrode solution is supplied from an electrode solution tank (not shown) to the electrode chamber (anode chamber) containing the anode 4 and the electrode chamber (cathode chamber) containing the cathode 5. The anode chamber and the cathode chamber are arranged on either side of an electrodialysis cell composed of a concentration compartment 2 and a deionization compartment 3. When a current is applied to the anode 4 and the cathode 5 using a power source 6, electrodialysis begins in the electrodialysis cell. Any known electrode solution can be used, such as an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution, an aqueous sodium hydrogen sulfate solution, or an aqueous potassium sulfate solution. However, when bipolar electrodialysis or the like is performed after electrodialysis, the electrode solution used in the electrodialysis device 1 is preferably one that does not contain sulfate.

[0084] In the electrodialysis tank, the concentration compartments 2 and the deionization compartments 3 are alternately arranged, each separated by an ion exchange membrane (either anion exchange membrane 7 or cation exchange membrane 8). The electrodialysis device 1 may have at least the deionization compartments 3, anion exchange membrane 7, concentration compartments 2, cation exchange membrane 8, and deionization compartments 3 arranged in this order. To enhance processing capacity, the electrodialysis device 1 may have one or more, preferably two or more, concentration compartments 2. The concentration compartments 2 may contain an electrolyte before electrodialysis. The electrolyte may contain, for example, an inorganic salt aqueous solution having electrical conductivity. For example, ion-exchanged water may be used when the electrodialysis device 1 is first used, and the previous concentrate may be used when the device is subsequently restarted after being stopped. In addition to these electrolytes, aqueous sodium chloride solutions, potassium iodide solutions, sodium iodide solutions, etc. may also be used. However, it is preferable that the electrolyte does not contain sulfate.

[0085] A specific example of the electrodialysis apparatus 1 used for the above-described electrodialysis has a plurality of gasket spacers (also called chamber frames) stacked between a pair of electrodes, anion exchange membranes 7 or cation exchange membranes 8 sandwiched between adjacent chamber frames, and the anion exchange membranes 7 and cation exchange membranes 8 are arranged so that, as a rule, they are alternately positioned overall, and each gasket forms an ion exchange chamber (current-carrying section) partitioned by the anion exchange membranes 7 and the cation exchange membranes 8. The ion exchange chambers are structured such that the deionization chambers 3 are chambers in which the cation exchange membrane 8 is positioned on the cathode 5 side and the anion exchange membrane 7 is positioned on the anode 4 side, and the concentration chambers 2 are chambers in which the anion exchange membrane 7 is positioned on the cathode 5 side and the cation exchange membrane 8 is positioned on the anode 4 side, and the deionization chambers 3 and the concentration chambers 2 are arranged alternately. That is, when current is applied while circulating the treatment liquid (electrolyte liquid) through the deionization compartment 3, the cations in the treatment liquid supplied to the deionization compartment 3 pass through the cation exchange membrane 8 and migrate to the concentrating compartment 2 on the adjacent cathode 5 side, and the anions in the treatment liquid pass through the anion exchange membrane and migrate to the concentrating compartment 2 on the adjacent anode 4 side. In this way, when the treatment liquid is circulated through the deionization compartment 3 and at the same time a salt water solution is circulated through the concentrating compartment 2, the treatment liquid is desalted and a concentrated liquid 20 with an increased salt concentration is obtained. A filter press is preferably used as a method for fixing the stack of these ion exchange compartments between the electrodes, but this is not a limitation.

[0086] In this embodiment, at least one or all of the anion exchange membranes 7 included in the electrodialysis device 1 are capable of absorbing the above-mentioned "sulfate ions (SO ４ ２－ ) versus the transmittance of iodide ions (I － ) transmittance ratio (T Ｉ / T ＳＯ４ ) and / or an anion exchange membrane that satisfies the above-mentioned "thickness swelling ratio."

[0087] When the anion exchange membrane 7 includes an anion exchange membrane other than the above-described anion exchange membrane, a known anion exchange membrane may be used as the other anion exchange membrane. For example, a monovalent ion permselective anion exchange membrane, a fully permeable anion exchange membrane, or a high-strength alkali-resistant anion exchange membrane may be used, and a monovalent ion permselective anion exchange membrane is preferred.

[0088] The cation exchange membrane 8 is not particularly limited, and a strongly acidic cation exchange membrane, a high-strength alkali-resistant cation exchange membrane, or the like can be used. A low-swelling cation exchange membrane may also be used. The cation exchange membrane 8 may also be a monovalent ion-selective cation exchange membrane, and more specifically, a cation exchange membrane in which sulfonic acid groups, which are strongly acidic cation exchange groups, are introduced into a basic skeleton of styrene-divinylbenzene can be used. Commercially available cation exchange membranes that can be used include Neosepta (registered trademark) CSE and Neosepta (registered trademark) CMB manufactured by Astom Corporation.

[0089] An example of the operation of the electrodialysis device 1 during electrodialysis is as follows. When a direct current is applied between the anode 4 and the cathode 5 using the power supply 6, iodide ions (I － ) passes through anion exchange membrane 7 and moves to concentration compartment 2, and cations in deionization compartment 3 on the other side (including at least one of monovalent cations such as alkali metal ions and divalent cations such as alkaline earth metal ions) pass through cation exchange membrane 8 and move to the same concentration compartment 2. In this concentration compartment 2, iodide salts such as potassium iodide (KI) are produced. A concentrate 20 containing iodide salts (iodine-containing concentrate) is obtained from concentration compartment 2. A deionized solution 30 is obtained from deionization compartment 3.

[0090] Here, an example of a process flow up to the electrodialysis step in the iodine recovery method will be described with reference to FIGS. 1 and 2.

[0091] First, waste liquid 10 is stored in waste liquid tank 11 via line 12 (piping).

[0092] The waste liquid 10 in the waste liquid tank 11 may be subjected to the above-mentioned chemical pretreatment or physical pretreatment. When the waste liquid 10 contains a boron component, a pH adjustment step may be carried out before the electrodialysis step to adjust the pH of the waste liquid 10 to 9.5 or less, preferably 8 or less, more preferably less than 7. When the pH of the waste liquid 10 is adjusted to 9.5 or less, boric acid (H ３ BO ３ Since most of the boron and iodine components in the wastewater 10 are present as molecules without being dissociated, even when electrodialysis is performed, the boric acid hardly moves and is discharged as it is into the desalted liquid 30. This allows efficient separation of the boron component and the iodine component in the wastewater 10.

[0093] When the waste liquid 10 is acidic (pH less than 7), it is preferable to adjust the pH of the waste liquid 10 to 3 or more. Since free iodine may be generated, which may deteriorate the ion exchange membrane and reduce the efficiency of electrodialysis, this can suppress the generation of free iodine due to the air oxidation of iodide ions and prevent the deterioration of the ion exchange membrane due to free iodine.

[0094] The lower limit of the temperature of the waste liquid 10 in the waste liquid tank 11 may be set to, for example, 25° C. or higher, preferably 30° C. or higher, and more preferably 35° C. or higher. The efficiency of electrodialysis can be improved by increasing the temperature of the waste liquid 10 supplied to the desalting compartment 3 in the electrodialysis apparatus 1. If there are restrictions on the apparatus itself, the upper limit of the temperature of the waste liquid 10 in the waste liquid tank 11 should be as high as possible within the range of the upper limit temperature that the apparatus can tolerate. If the electrodialysis apparatus 1 is equipped with PVC piping, the upper limit may be set to, for example, 40° C. or lower.

[0095] Subsequently, the waste liquid 10 in the waste liquid tank 11 is supplied to the desalting compartment 3 of the electrodialysis device 1 via line 13. A voltage is applied to the anode 4 and the cathode 5 to perform electrodialysis (electrodialysis step). In the electrodialysis step, the concentration of iodide ions (halide ions) in the desalted liquid at the end point as determined by absorbance method may be, for example, 0.5 g / L or more and 5 g / L or less.

[0096] The desalted liquid 30 produced in the desalting compartment 3 by electrodialysis is recovered via line 31. On the other hand, the concentrated liquid 20 produced in the concentrating compartment 2 by electrodialysis is recovered via line 22.

[0097] At this time, at least a portion of the desalted solution 30 may be supplied to the waste solution tank 11 via a line 32 branched from the line 31, and a mixed desalted solution obtained by mixing the desalted solution 30 and the waste solution 10 may be supplied again to the desalting compartment 3. In other words, the waste solution 10 supplied to the desalting compartment 3 may contain the desalted solution 30. By repeatedly performing electrodialysis in this manner, the iodide ion concentration in the desalted solution 30 can be reduced to a desired value.

[0098] Alternatively, at least a portion of the concentrate 20 may be supplied to the concentrate tank 21 via a line 23 branched from the line 22, and the concentrate 20 in the concentrate tank 21 may be supplied again to the concentrating compartment 2 via a line 24. By repeatedly performing electrodialysis in this manner, the iodide ion concentration in the concentrate 20 can be concentrated to a desired value.

[0099] In addition, when two or more electrodialysis devices are provided, a first concentrate produced in a first electrodialysis device may be supplied to a desalting compartment of a second electrodialysis device, and a second desalted solution produced in the desalting compartment of the second electrodialysis device may be mixed with the first concentrate and supplied again to the desalting compartment of the second electrodialysis device.

[0100] Alternatively, an electrodialysis apparatus 1 equipped with a continuous circulation type electrodialysis facility may be used. Such an electrodialysis apparatus 1 can be continuously operated by continuously supplying the waste liquid 10 or a mixed desalted solution to the desalted solution 30 while continuously discharging the desalted solution 30.

[0101] Next, an example of a process flow of the regeneration step in the iodine recovery method will be described with reference to FIG.

[0102] Subsequently, in the iodine recovery method, after the electrodialysis step, the obtained iodine-containing concentrated solution (concentrated solution 20) is used to extract iodine (I ２ The method may include a regeneration step of producing one or more selected from the group consisting of iodine, iodide salt, and hydroiodic acid. The iodine, iodide salt, and hydroiodic acid regenerated (recycled) by the above-mentioned iodine recovery method may each be in the form of an aqueous solution, and the iodine and iodide salt may be in the form of powder (including granules).

[0103] The iodine recovery method can recover hydroiodic acid using the obtained concentrated solution 20. For example, the iodine recovery method may include a step (bipolar electrodialysis step) of separating an iodine-containing concentrated solution (concentrated solution 20) into hydroiodic acid and an aqueous hydroxide salt solution by bipolar membrane electrodialysis, as shown in Fig. 3. Here, the bipolar membrane electrodialysis method is a method in which, between an anode and a cathode, bipolar membranes that generate hydrogen ions and hydroxide ions, in addition to cation exchange membranes and / or anion exchange membranes, are arranged in this order, and a treatment solution is supplied to each chamber partitioned by the membranes and an electric current is applied to obtain an acid and an alkali from a neutral salt.

[0104] Specifically, the concentrated solution 20 (e.g., KI concentrated solution) discharged from the electrodialysis device 1 is introduced into the bipolar membrane electrodialysis device. If necessary, the concentrated solution 20 may be acidified by adjusting the pH to less than 7. When a direct current is applied to the bipolar membrane electrodialysis device, the iodide salt in the concentrated solution 20 is electrolyzed, and an aqueous solution of hydroiodic acid (HI solution) and an aqueous solution of hydroxide (e.g., KOH) are discharged. The HI solution is then purified by distillation to obtain hydroiodic acid.

[0105] In addition, the iodine recovery method uses the obtained concentrated solution 20 to recover iodine (I ２ As shown in FIG. 3, when the concentrated solution 20 containing iodide ions is oxidized, iodine (I ２ ) is obtained.

[0106] In the iodine recovery method, iodide salts can be recovered using the obtained concentrated solution 20. As shown in FIG. 3, iodide salts can be obtained by neutralizing the hydroiodic acid obtained above. In addition, iodine (I ２) is reduced and neutralized to obtain an iodide salt. In the iodine recovery method, the oxidation, neutralization, and reduction methods are not particularly limited, and known means can be used. Examples of iodide salts include alkali metal iodide salts and alkaline earth metal iodide salts. Specific examples of iodide salts include potassium iodide, sodium iodide, calcium iodide, magnesium iodide, and cesium iodide. These may be used alone or in combination of two or more.

[0107] On the other hand, the iodine recovery method uses the obtained desalted liquid 30 to extract iodine (I ２ As shown in Fig. 3, the method for recovering iodine may include a step of passing the obtained desalted solution 30 through a strong basic anion exchange resin to adsorb iodide ions remaining in the desalted solution 30 onto the strong basic anion exchange resin, and recovering iodine from the strong basic anion exchange resin.

[0108] Specifically, the desalted solution 30 discharged from the electrodialysis device 1 is passed through a strongly basic ion exchange resin, and iodide ions are adsorbed onto the strongly basic anion exchange resin. At this time, the pH of the desalted solution 30 when passed through the strongly basic anion exchange resin is adjusted to less than 7, preferably between 3 and 7, as in the electrodialysis described above. This prevents borate ions formed by dissociation of boric acid from being adsorbed onto the strongly basic anion exchange resin, and allows selective separation of iodide ions. Thereafter, iodine (I) is removed from the strongly basic anion exchange resin by a known means. ２ ) can be recovered.

[0109] Furthermore, when the waste liquid 10 contains a boron component, boron (B) can be recovered from the resulting desalted liquid 30 containing the boron component.

[0110] The iodine recovery method may include a boron recovery step in which the pH of the desalted solution 30 containing a boron component is adjusted to, for example, 7 or more, preferably 8 or more, more preferably 11 or more, and then a boron-containing concentrate (boric acid concentrate) is separated and recovered from the desalted solution 30 using another electrodialysis device. When the boron-containing concentrate is acidified and crystallized, boric acid (H ３ BO ３) can be recovered.

[0111] Alternatively, the desalted solution 30 containing boron components and having a pH of 7 or higher, or the desalted solution 30 obtained when passing through the strongly basic anion exchange resin, may be passed through a boron-selective chelating resin to adsorb boric acid ions. Thereafter, boric acid can be recovered from the boron-selective chelating resin by known means.

[0112] Although the embodiments of the present invention have been described above, these are merely illustrative of the present invention, and various other configurations may be adopted. Furthermore, the present invention is not limited to the above-described embodiments, and modifications, improvements, etc., within the scope of achieving the object of the present invention, are included in the present invention. Examples of reference embodiments are described below. 1. A method for operating an electrodialysis device, comprising an electrodialysis step of electrodialyzing an aqueous solution containing halide ions and a polar organic solvent using an electrodialysis device equipped with an anion exchange membrane manufactured by a crosslinking polymerization method, wherein the aqueous solution contains 200 mg / L or more of iodide ions, and in the electrodialysis step, the anion exchange membrane comprises an anion exchange membrane having a thickness swelling ratio of 104% or less, as measured according to the following measurement procedure. (Measurement Procedure) The thickness of the anion exchange membrane is measured before and after treatment by immersing it in an aqueous dimethylacetamide solution having a concentration of 50% by mass at a liquid temperature of 40°C for 1 hour, and the thickness before treatment is measured as D. ０ , the thickness after treatment is D ５０ The obtained D ０ , D ５０ The thickness expansion rate of the ion exchange membrane is calculated using the formula: (D ５０ / D ０) × 100. 2. A method for operating an electrodialysis apparatus according to 1., wherein in the electrodialysis step, the electrodialysis apparatus is equipped with a cation exchange membrane manufactured by a crosslinking polymerization method, and the cation exchange membrane has a thickness swelling ratio of 104% or less as measured according to the measurement procedure. 3. A method for operating an electrodialysis apparatus, comprising an electrodialysis step of electrodialyzing an aqueous solution containing halide ions and a polar organic solvent using an electrodialysis apparatus equipped with an anion exchange membrane manufactured by a crosslinking polymerization method, wherein the aqueous solution contains 200 mg / L or more of iodide ions, and in the electrodialysis step, the anion exchange membrane is used to perform an electrodialysis test using a desalted solution containing iodide ions and sulfate ions, and the anion exchange membrane has a thickness swelling ratio of 104% or less in a concentrated solution when the iodide ion residual ratio in the desalted solution is 5%. － ) transmittance (%) is T Ｉ , sulfate ions (SO ４ ２－ ) transmittance (%) is T ＳＯ４ When defined as Ｉ / T ＳＯ４3. A method for operating an electrodialysis apparatus comprising an anion exchange membrane having a dielectric constant of 3.5 or more. 4. A method for operating an electrodialysis apparatus according to 3., wherein in the electrodialysis step, the polar organic solvent comprises a polar organic solvent having a dielectric constant of more than 30 at 25°C and / or a low dielectric organic solvent having a dielectric constant of 30 or less at 25°C. 5. A method for operating an electrodialysis apparatus comprising an electrodialysis step of electrodialyzing an aqueous solution containing halide ions and a polar organic solvent using an electrodialysis apparatus equipped with an anion exchange membrane produced by a crosslinking polymerization method, wherein the aqueous solution contains 200 mg / L or more of iodide ions, and in the electrodialysis step, the polar organic solvent comprises a polar organic solvent having a dielectric constant of 30 or less at 25°C. 6. A method for operating an electrodialysis apparatus according to any one of 1. to 5., wherein in the electrodialysis step, the concentration of halide ions in the desalted solution at the endpoint measured by an absorbance method is 0.5 g / L or more and 5 g / L or less. 7. The method for operating the electrodialysis apparatus according to any one of 1. to 6., wherein the aqueous solution contains 0.1 mass % to 50 mass % of the polar organic solvent. 8. The method for operating the electrodialysis apparatus according to any one of 1. to 7., wherein the halide ions are iodide ions (I － 9. The method for operating an electrodialysis apparatus according to item 8., further comprising the step of: － ) with iodine (I ２ ), iodic acid (HIO ３ ), periodic acid (HIO ４10. A method for operating an electrodialysis device according to any one of 1. to 9., wherein the anion exchange membrane comprises a base substrate containing polyolefin and an ion-permselective layer formed on one or both sides of the base substrate. 11. A method for operating an electrodialysis device according to any one of 1. to 10., wherein in the electrodialysis step, the anion exchange membrane comprises an anion exchange membrane whose rate of change in ion exchange capacity before and after immersion in a polar organic solvent with a concentration of 50% by mass is within ±5%. 12. A method for operating an electrodialysis device according to any one of 1. to 11., wherein the anion exchange membrane comprises an ion exchange membrane whose rate of change in ion exchange capacity before and after immersion in a polar organic solvent with a concentration of 50% by mass is within ±5%. 12. A method for operating an electrodialysis apparatus according to any one of the above, wherein in the electrodialysis step, the anion exchange membrane comprises an anion exchange membrane whose change in water content, as measured by the Karl Fischer method, is within ±20% before and after immersion in a polar organic solvent having a concentration of 50% by mass. 13. An electrodialysis apparatus for electrodialyzing an aqueous solution containing halide ions and a polar organic solvent, comprising: a concentration compartment; a deionization compartment; and an anion exchange membrane and a cation exchange membrane manufactured by a crosslinking polymerization method, which separate the concentration compartment from the deionization compartment, wherein the aqueous solution contains 200 mg / L or more of iodide ions, and the anion exchange membrane comprises an anion exchange membrane whose thickness swelling ratio, as measured according to the following measurement procedure, is 104% or less. (Measurement procedure) The thickness of the anion exchange membrane is measured before and after immersion in a 50% by mass aqueous dimethylacetamide solution at a liquid temperature of 40°C for 1 hour, and the thickness before the treatment is determined as D. ０ , the thickness after treatment is D ５０ The obtained D ０ , D ５０ The thickness expansion rate of the ion exchange membrane is calculated using the formula: (D ５０ / D ０ ) × 100.

[0113] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the descriptions of these examples.

[0114] <Production of anion exchange membrane> (Anion exchange membrane A) 91.2 parts by mass of chloromethylstyrene, 5.0 parts by mass of divinylbenzene, 3.8 parts by mass of ethylvinylbenzene, 4.0 parts by mass of di-tert-butyl peroxide as a radical polymerization initiator, and 4.0 parts by mass of styrene oxide as a hydrogen chloride gas scavenger were added to obtain a paste-like polymerizable composition. Next, the polymerizable composition described above was applied to a polyethylene biaxially stretched porous film (thickness 100 μm, porosity 46%, average pore diameter 0.13 μm) as a substrate, and the polymerizable composition was introduced into the substrate. Next, both sides of the substrate into which the polymerizable composition had been introduced were covered with a release material made of polyethylene terephthalate film and wound around a roller, and then polymerization was carried out. The polymerization temperature pattern was as follows: the temperature was raised from 20°C to 50°C over 30 minutes, held at 50°C for 20 minutes, then raised to 130°C over 80 minutes, and held at 130°C for 4 hours to produce a base membrane for introducing anion exchange groups. The release film was then peeled off from the base membrane for introducing anion exchange groups. Instead of completely removing the release material from both sides of the base membrane, the release material was left on one side. This base membrane for introducing anion exchange groups, covered only on one side with the release material, was immersed in a 0.05 mol / L dimethylamine aqueous solution for 5.5 hours at 34°C, and the chloromethyl groups on the surface not covered with the release material were crosslinked with dimethylamine. The resulting base membrane was then washed with a 1.0 mol / L hydrochloric acid aqueous solution and pure water. Next, after removing the release agent film covering one side, the raw membrane for introducing anion exchange groups was immersed in a 0.01 mol / L aqueous sodium hydroxide solution for 15 hours at 60°C, and a process of treating with an alkaline aqueous solution was carried out. Thereafter, the raw membrane after the alkaline aqueous solution treatment was washed using pure water. Next, a quaternization reaction was carried out at 30°C for 16 hours using an aqueous solution containing 5% by mass of trimethylamine and 25% by mass of acetone, and a process of introducing quaternary ammonium groups was carried out by substituting the chlorine of the remaining chloromethyl groups in the membrane with trimethylamine. Thereafter, the raw membrane after the introduction of quaternary ammonium groups was washed using a 1.0 mol / L aqueous hydrochloric acid solution and pure water, and a monovalent selective anion exchange membrane was obtained.

[0115] (Anion Exchange Membrane B) A mixture having the following formulation was prepared: 33.2 parts by mass of styrene, 16.8 parts by mass of divinylbenzene (purity 57%, remainder ethylvinylbenzene), 50.0 parts by mass of chloromethylstyrene, 25.0 parts by mass of acetyl tributyl citrate, 3.4 parts by mass of styrene oxide, 2.6 parts by mass of t-butylperoxy-2-ethylhexanoate (Perbutyl O, manufactured by NOF Corporation). To this mixture, 19.7 parts by mass of a hydrogenated styrene-butadiene triblock copolymer (trade name: Tuftec M1913, manufactured by Asahi Kasei Corporation) having a polystyrene content of 30% by mass was added, and the mixture was stirred at 40°C for 20 hours to obtain a uniform polymerizable composition. Next, the following high-density polyethylene monofilament woven fabric was prepared. High-density polyethylene monofilament woven fabric; Warp: 120 mesh - wire diameter 76 μm (33 denier) Weft: 120 mesh - wire diameter 76 μm (33 denier) Thickness: 132 μm Opening ratio: 41% The polymerizable composition obtained above was applied to the high-density polyethylene monofilament woven fabric, and both sides were covered with polyester film as a release agent, followed by polymerization for 5 hours at 70° C. The obtained membrane-like polymer was then subjected to an amination reaction using an aqueous solution of 5% by mass of trimethylamine and 25% by mass of acetone at 30° C. for 16 hours to obtain an anion exchange membrane.

[0116] (Anion Exchange Membrane C) A base membrane for introducing anion exchange groups was produced in the same manner as anion exchange membrane A. Next, the release film was peeled off from the base membrane for introducing anion exchange groups. However, at this time, the release material on both sides of the base membrane was not completely peeled off, but the release material was left on one side. This base membrane for introducing anion exchange groups, covered only on one side with the release material, was immersed in a 0.05 mol / L-dimethylamine aqueous solution for 10 hours at 34°C, and the chloromethyl groups on the surface not covered with the release material were crosslinked with dimethylamine. Thereafter, the obtained base membrane was washed using a 1.0 mol / L-hydrochloric acid aqueous solution and pure water. Next, after removing the release agent film covering one side, the base membrane for introducing anion exchange groups was immersed in a 0.01 mol / L-sodium hydroxide aqueous solution for 15 hours at 60°C, and a process of treating with an alkaline aqueous solution was carried out. Thereafter, the base membrane after alkaline aqueous solution treatment was washed using pure water. Next, a quaternization reaction was carried out for 16 hours at 30°C using an aqueous solution containing 5% by mass of trimethylamine and 25% by mass of acetone, and the chlorine of the remaining chloromethyl groups in the membrane was replaced with trimethylamine, thereby introducing quaternary ammonium groups. Thereafter, the raw membrane after the introduction of the quaternary ammonium groups was washed using a 1.0 mol / L aqueous hydrochloric acid solution and pure water to obtain a monovalent selective anion exchange membrane.

[0117] <Thickness Swelling Ratio> A 50% by mass aqueous solution of dimethylacetamide was placed in a glass container and heated in a water bath while stirring with a stirrer so that the temperature of the aqueous solution reached approximately 40°C. The ion exchange membrane was then placed in the container, and the temperature and stirring were continued until one hour had elapsed. The thickness (D ０ ), and the thickness of the ion exchange membrane after immersion in dimethylacetamide water immediately after removal (D ５０ ) was measured. ０ , D ５０ The thickness expansion rate of the ion exchange membrane is calculated using the formula: (D ５０ / D ０) × 100. The thickness expansion rate of the anion exchange membrane A was 101%. The thickness expansion rate of the anion exchange membrane B was 105%.

[0118] <Cl concentration test in seawater － and S.O. ４ Index > Small electrodialysis device (electric membrane area 100 cm ２ ) was treated with a monovalent selective cation exchange membrane CIMS (manufactured by Astom Corporation, membrane resistance 2.0 Ω cm ２ The anion exchange membrane was used in pairs, and the monovalent selective surface was mounted together with the sample anion exchange membrane so that it faced the deionization compartment. The operating conditions were as follows: seawater at 25°C was passed through the deionization compartment at a flow rate of 6 cm / sec, the concentration compartment was filled with a 3.5 mol / L NaCl aqueous solution, and the current density was 3 A / dm ２ Electrodialysis was performed for 5 hours or more (until the concentration in the concentration compartment stopped changing) to measure the amount of chloride ions (Cl － ) and sulfate ions (SO ４ ２－ The concentration of chloride ions (Cl) in the concentration compartment was measured. － ) concentration (N) and sulfate ions (SO ４ ２－ ) concentration (10 －３ The resulting chloride ions (Cl － ) concentration (N) and sulfate ions (SO ４ ２－ ) concentration, － Permeation rate and SO ４ The SO of anion exchange membrane A was used as an index. ４ The index is 9.3 x 10 －３ N. SO of anion exchange membrane B ４ The index is 82 x 10 －３ N. SO of anion exchange membrane C ４ The index is 5.2 x 10 －３ It was N.

[0119] <Ion Exchange Capacity> (Immersion Treatment) A 300 mL glass container was charged with an aqueous organic solvent solution adjusted to a predetermined concentration, and the solution was heated in a water bath while stirring with a stirrer so that the temperature of the aqueous organic solvent solution reached 38°C to 40°C. The ion exchange membrane was then added, and the temperature and stirring were continued. After 1.5 hours, the ion exchange membrane was removed, and the organic solvent adhering to the surface was washed away with ion exchange water, and the following measurements were performed: Immersion temperature: 38 to 40°C Immersion time: 1.5 hours Amount of immersion solution: 200 mL Area of ​​ion exchange membrane: 25 cm ２ ・Bath ratio: 25cm ２ / 200mL

[0120] (Procedure for measuring ion exchange capacity) Ion exchange membrane (area: 25 cm ２ ) to 2 mol / L-NaNO ３ After immersion in the aqueous solution for 30 minutes and rinsing with water, the plate was immersed in a 2 mol / L NaCl aqueous solution for 1 hour, 1 hour, and 6 hours or more, with the solution being repeatedly renewed. ３ The sample was immersed in the aqueous solution for 1 hour, 1 hour, and 6 hours or more, with the solution being repeatedly renewed. ３ Aqueous solution (indicator: K ２ CrO ４ ) and the ion exchange capacity of the ion exchange membrane was measured before and after the immersion treatment. Furthermore, when the ion exchange capacity before the immersion treatment was X1 and the ion exchange capacity after the immersion treatment was X2, the change rate (%) of the ion exchange capacity before and after the immersion treatment was calculated from [(X2 / X1)-1] x 100. When a 50% by mass concentration of DMAc was used as the organic solvent aqueous solution for the immersion treatment, the change rate of the ion exchange capacity of the anion exchange membrane A before and after the immersion treatment was -1%, 0% in the case of a 50% by mass concentration of DMF, and -2% in the case of a 50% by mass concentration of IPA.

[0121] <Moisture Content> The weight of the ion exchange membrane was measured and used as the sample weight (g) before the immersion treatment. The immersion-treated ion exchange membrane (sample) was sandwiched between Kimtowels, a 1 kg weight was placed on it, and the sample was left to stand for 1 minute. After standing, the sample was cut, and the moisture content was measured by the Karl Fischer method to obtain the sample moisture content (μg). A CA-31 manufactured by Nittoseiko Corporation was used as the moisture content measuring device. Measurement was started 3 minutes after the sample was placed on the measuring device. The heating conditions for the measuring device were 180°C and 20 minutes. The above moisture content measurement was performed without placing a sample, and a blank value (μg) was obtained. Using the above measurement results, the moisture content (% by mass) of the ion exchange membrane after the immersion treatment was calculated based on "(sample moisture content - blank value) / sample weight before the immersion treatment". The moisture content of the ion exchange membrane before the immersion treatment was also calculated in a similar manner by using the ion exchange membrane before the immersion treatment as the sample. Furthermore, when the moisture content before the immersion treatment was Y1 and the moisture content after the immersion treatment was Y2, the change in moisture content (%) before and after the immersion treatment was calculated from [(Y2 / Y1)-1] x 100. When IPA with a concentration of 50% by mass was used as the organic solvent aqueous solution for the immersion treatment, the change in moisture content before and after the immersion treatment was −1% for anion exchange membrane A and more than −20% for anion exchange membrane B.

[0122] <Manufacturing of Electrodialysis Apparatus> The anion exchange membrane was placed in a tabletop test apparatus (Micro Acilyzer (registered trademark) S3, manufactured by Astom Corporation) to assemble an electrodialysis apparatus. Using the obtained electrodialysis apparatus, an electrodialysis test was performed on each of the anion exchange membranes A and B manufactured above. The procedure for assembling the electrodialysis apparatus will be specifically described below. First, an anion exchange membrane was punched out using a cutting die made for the tabletop test apparatus (hereinafter referred to as S3). Similarly, a polyolefin-based cation exchange membrane (the thickness expansion coefficient of which was 101%) was punched out. Twelve punched cation exchange membranes (hereinafter referred to as C membranes) ([1] to

[12] ) and ten punched anion exchange membranes (hereinafter referred to as A membranes) ([1] to

[10] ) were prepared. Using these, the following stacking order was used: anode frame, end gasket, C membrane [1], concentration compartment gasket, A membrane [1], deionization compartment gasket, C membrane [2], ..., C membrane

[10] , concentration compartment gasket, A membrane

[10] , deionization compartment gasket, C membrane

[11] , concentration compartment gasket, C membrane

[12] , end gasket, and cathode frame. Spacer mesh was fitted to the conductive parts of the concentration compartment gasket and cathode compartment gasket. The A membrane was attached with its selective surface facing the deionization compartment. Bolts were passed through the four corners of the frame and tightened to the specified torque to obtain a stack. This stack was inserted between the anode and cathode chambers and secured to the main body by tightening the bolts at the four corners. S3 has three built-in magnetic pumps, each connecting the deionized liquid tank to the deionization compartment connecting hole and the concentration compartment tank to the concentration compartment connecting hole, and returning the liquid to the original tank after passing through the stack. The third pump runs from the electrode solution tank through the cathode and anode chambers in series before returning to the tank. If necessary, the piping can be connected to a heat exchanger, or a cooler or heater can be installed in the tank to adjust the temperature. In this example, 1 mol / L NaOH was used as the electrode solution. The anode and cathode plates were titanium plates coated with platinum. These electrode plates were connected to a rectifier capable of supplying direct current.

[0123] (Evaluation of Electrodialysis) A stock solution containing at least iodide ions, sulfide ions, and a polar organic solvent was supplied to the desalting compartment of the electrodialysis device assembled above as the desalted solution. Pure water was used as the concentrate, and a 4% aqueous sodium hydroxide solution was used as the electrode solution. The content of each component in the desalted solution was measured at appropriate intervals from the start of electrodialysis until the residual iodide ion rate in the desalted solution reached 1%. A constant voltage of 10 V was applied. The relative dielectric constants of the polar organic solvents at 25°C were 19.9 for IPA, 37.8 for DMAc, and 36.7 for DMF, respectively.

[0124] In the electrodialysis of a desalted solution containing a polar organic solvent, the concentration of iodide ions (I) in the concentrated solution when the residual rate of iodide ions is 5% － ) transmittance (%) is T Ｉ , sulfate ions (SO ４ － ) transmittance (%) is T ＳＯ４ and iodide ions (I － ) transmittance ratio is T Ｉ / T ＳＯ４ At this time, T Ｉ is (100%-5%), SO ４ － was defined as (100% - "residual rate of sulfate ions in the desalted solution when the residual rate of iodide ions is 5%). 100% means the residual rate before electrodialysis. Ｉ and T ＳＯ４ Using the above "T Ｉ / T ＳＯ４ " was determined. For Example 3 and Comparative Example 2, electrodialysis evaluation was performed three times, and Table 2 shows the one with the highest IPA residual rate. It was confirmed that Comparative Example 2 had a larger difference between the maximum and minimum IPA residual rates and a larger variation in values ​​than Example 3. Iodide ions, chloride ions, and sulfate ions were quantified by ion chromatography. Sodium ions were quantified using an ICP optical emission spectrometer. Organic matter was quantified by measuring the total organic carbon concentration using a TOC meter and converting it to DMAc or IPA.

[0125]

[0126] The results of the above (electrodialysis evaluation) showed that Examples 1 and 2 had a higher residual rate of polar organic solvent than Comparative Example 1, Example 3 had a smaller variation in the residual rate of polar organic solvent than Comparative Example 2, and Example 4 had a higher residual rate of polar organic solvent than Comparative Example 2. From the above, it was found that the electrodialysis methods of each Example can operate the electrodialysis apparatus even in an environment where a polar organic solvent is contained in the desalted solution, and can increase the selective permeability of halide ions through the polar organic solvent. Furthermore, it was found that Examples 3 and 4, compared to Comparative Example 2, can selectively allow iodide ions to pass through while relatively leaving chloride ions among halide ions.

[0127] This application claims priority based on Japanese Patent Application No. 2023-177030, filed October 12, 2023, the disclosure of which is incorporated herein by reference in its entirety.

[0128] REFERENCE SIGNS LIST 1 Electrodialysis device 2 Concentration compartment 3 Demineralization compartment 4 Anode 5 Cathode 6 Power source 7 Anion exchange membrane 8 Cation exchange membrane 10 Waste liquid 11 Waste liquid tank 12, 13 Lines 20 Concentrated liquid 21 Concentrated liquid tank 22, 23, 24 Lines 30 Demineralized liquid 31, 32 Lines 100 Iodine recovery system

Claims

1. A method for operating an electrodialysis apparatus, comprising an electrodialysis step of electrodialyzing an aqueous solution containing halide ions and a polar organic solvent using an electrodialysis apparatus equipped with an anion exchange membrane manufactured by a crosslinking polymerization method, wherein the aqueous solution contains 200 mg / L or more of iodide ions, and in the electrodialysis step, the anion exchange membrane is capable of detecting a concentration of iodide ions (I ions) in a concentrated solution when the iodide ion residual rate in the desalted solution is 5% when an electrodialysis test is performed using a desalted solution containing iodide ions and sulfate ions. － ) transmittance (%) is T Ｉ , sulfate ion (SO ４ ２－ ) transmittance (%) is T ＳＯ４ When defined as above, T Ｉ / T ＳＯ４ A method for operating an electrodialysis apparatus comprising an anion exchange membrane having a β-adjustment coefficient of 3.5 or more.

2. A method for operating an electrodialysis apparatus according to claim 1, wherein in the electrodialysis step, the polar organic solvent comprises an organic solvent having a relative dielectric constant of 5 or more at 25°C.

3. A method for operating an electrodialysis apparatus according to claim 1 or 2, wherein the aqueous solution contains 0.1% by mass or more and 50% by mass or less of the polar organic solvent.

4. A method for operating an electrodialysis apparatus according to claim 1 or 2, wherein in the electrodialysis step, the concentration of halide ions in the desalted liquid at the end point determined by an absorbance method is 0.5 g / L or more and 5 g / L or less.

5. A method for operating an electrodialysis apparatus according to claim 1 or 2, comprising the steps of: ２ ), iodic acid (HIO ３ ), periodic acid (HIO ４ ), and iodine compounds, by reducing one or more of the compounds.

6. A method for operating an electrodialysis apparatus according to claim 1 or 2, wherein the anion exchange membrane comprises a base substrate containing a polyolefin and an ion-selective permeable layer formed on one or both sides of the base substrate.

7. A method for operating an electrodialysis apparatus according to claim 1 or 2, wherein in the electrodialysis step, the anion exchange membrane includes an anion exchange membrane whose ion exchange capacity changes within ±5% before and after an immersion treatment in a polar organic solvent having a concentration of 50% by mass.

8. A method for operating an electrodialysis apparatus according to claim 1 or 2, wherein in the electrodialysis step, the anion exchange membrane includes an anion exchange membrane whose water content, as measured by the Karl Fischer method, changes within ±20% before and after an immersion treatment in isopropyl alcohol having a concentration of 50% by mass.

9. An electrodialysis apparatus for electrodialyzing an aqueous solution containing halide ions and a polar organic solvent, comprising: a concentration compartment; a desalting compartment; and an anion exchange membrane and a cation exchange membrane produced by a cross-linking polymerization method, which separate the concentration compartment from the desalting compartment; wherein the aqueous solution contains 200 mg / L or more of iodide ions; and wherein the anion exchange membrane is capable of detecting iodide ions (I ions) in a concentrated solution at a residual rate of 5% in the desalting solution when an electrodialysis test is carried out using a desalting solution containing iodide ions and sulfate ions. － ) transmittance (%) is T Ｉ , sulfate ion (SO ４ ２－ ) transmittance (%) is T ＳＯ４ When defined as above, T Ｉ / T ＳＯ４ An electrodialysis apparatus comprising an anion exchange membrane having a solubility in anion exchange membrane of 3.5 or more.

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