Cation exchange membrane, ion exchange membrane unit, and electrodialysis device

Abstract

To provide a cation exchange membrane which is highly selective to specific cations, particularly ammonium ions, and which also has high energy efficiency during dialysis. A cation exchange membrane having a cation exchange layer containing a metal cyano complex and a binder resin.

Description

TECHNICAL FIELD

[0001] The present application relates to a cation exchange membrane, an ion exchange membrane unit and an electrodialysis device using the same, and a manufacturing method of a cation exchange membrane. BACKGROUND

[0002] Among technologies for concentrating and separating ions in wastewater, there are distillation, ion exchange, adsorption, reverse osmosis (RO) membrane, forward osmosis (FO) membrane, brine concentration (BC), electrodialysis (ED), Donnan dialysis, and the like. Among these, distillation can handle a wide range of salt concentrations and water qualities, and is excellent in resistance to contamination, but requires a large amount of energy, and is particularly unsuitable for treatment of dilute solutions. In ion exchange and adsorption, various ion exchangers and adsorbents have been developed (see, for example, Patent Documents 1 and 2), but a regeneration process of the ion exchange material and the adsorbent is required (see Patent Documents 3 and 4), and thus it is difficult to operate continuously, and equipment and reagents for regenerating the ion exchange material and the adsorbent are required, and thus it is not suitable for continuous treatment. In the RO membrane method, ions are concentrated by applying a pressure of more than the osmotic pressure to the wastewater to remove water, and thus the power cost becomes high when concentrating from a dilute solution. Also, for wastewater containing a membrane contamination substance, the frequency of cleaning and replacement of the membrane increases. In addition, due to the pressure limit of the membrane, it is difficult to achieve concentration of a high salt concentration. In the FO membrane method, as with the RO membrane method, water is removed to concentrate ions. By using a driving force solute (DS), it is possible to concentrate ions without applying pressure and without using electricity, but in addition to this, it has the same problems as the RO membrane. In the brine concentration (BC) method, by connecting FO membrane modules in multiple stages in series, it is possible to achieve concentration of a higher salt concentration than the RO membrane, but on the other hand, since a part of the concentrated solution is returned, a larger membrane area is required than in the RO membrane method. The Donnan dialysis method uses a DS to concentrate and separate ions as with the FO membrane method, and thus does not require electricity, but requires separation of the DS from the target ions. As described above, each technology has advantages and disadvantages, but since impurities and various ions are present in actual treatment water, in addition to ion exchange, all of them have the following problems: scaling is generated due to these ions, and the energy efficiency of concentration of the target ions decreases.

[0003] The ED method is a technique for ion concentration and desalination using an ion exchange membrane. In the case of concentration, ions are migrated to concentrate, and thus the ED method is particularly effective for separating and concentrating specific trace ions that are contaminants of the membrane. Although a large amount of power is required for high-concentration salt treatment, the ED method, like the BC method, can achieve high-concentration treatment. However, in the case of the ED method, ions other than the target ions are also concentrated at the same time. In this case, if divalent cations such as calcium ions are concentrated, scaling is generated in the membrane, on the surface of the membrane, or in the solution flow path, which leads to membrane damage and a decrease in system efficiency (see Non-Patent Literature 1). In addition, if there are cations of the same valence as the target ions, for example, monovalent ions such as Na ions and K ions exist when ammonium ions are the target, the concentration of these ions consumes power, and thus there is a problem of a decrease in energy efficiency of the separation and concentration of the target ions. Therefore, it is desirable to develop an ion exchange membrane that selectively allows specific target ions such as ammonium ions to pass through.

[0004] Among cations, separation and concentration of ammonium ions in particular are attracting attention for the following reasons. At present, a large amount of energy is consumed for harmless treatment of nitrogen compounds in exhaust gas and wastewater. However, there are cases where nitrogen compounds are released without treatment and cases where treatment is insufficient, which have a large impact on the environment. Therefore, a technology for resource ammoniation of nitrogen compounds in wastewater is required, which achieves harmless and resourceful treatment of these harmful nitrogen compounds from human activities (Clean Earth). Therefore, in view of nitrogen compounds in wastewater, a technology for converting these nitrogen compounds into ammonia (including ammonium ions) and concentrating them, thereby making them into a form that can be utilized as a valuable substance (resource ammonia), has been developed. In this technology, a technology for separating and concentrating ammonium ions present in wastewater in an energy-saving manner is attracting attention.

[0005] Prior Art Documents Patent Documents Patent Literature 1: International Publication WO2015 / 186819 Pamphlet Patent Literature 2: Japanese Patent Application Publication No. 2012-250904 Patent Literature 3: Japanese Patent Application Publication No. 2019-34273 Patent Literature 4: International Publication WO2020 / 080302 Pamphlet Non-Patent Literature Non-Patent Literature 1: "Ion Exchange Membrane Selective Permeability to Ions", Asahi Research Report 64 (2014), pp. 21-25 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION An object of the present application is to provide a cation exchange membrane which is highly selective to specific cations, particularly ammonium ions, and which is also highly energy efficient during dialysis.

[0007] Means for solving the problem The inventors of the present application began to study ion exchange membranes which are highly selective to specific ions, and advanced the study of ion exchange membranes which are highly selective to permeation of ammonium ions as a specific target ion. In the course of advancing the study, it was unexpectedly found that a membrane produced by mixing particles of a metal cyano complex known as an adsorbent material for ammonium ions, cesium ions (Patent Documents 1 and 2), and a binder becomes a cation exchange membrane which is highly selective to permeation of ammonium ions. An adsorbent material adsorbs a target ion and retains the target ion in the adsorbent, and thus is mainly used for batch processing. On the other hand, an ion exchange membrane migrates a target ion selectively and continuously in the membrane by means of driving forces such as electric power and diffusion force. In addition, an adsorbent is used in a particulate form, whereas an ion exchange membrane needs to be produced in a thin film form to be able to exert its function. For this reason, it has never been considered to produce a cation exchange membrane using a metal cyano complex as an adsorbent in the past. The present application was thus completed.

[0008] That is, the present application is determined by the matters shown below.

[0009] (1) A cation exchange membrane having a cation exchange layer containing a metal cyano complex and a binder resin.

[0010] (2) The cation exchange membrane according to the above (1), wherein the mass ratio of the metal cyano complex : the binder resin is 0.2 : 1 to 5 : 1.

[0011] (3) The cation exchange membrane according to the above (1) or (2), which has a membrane resistance of 0.2 to 15 Ωcm 2 .

[0012] (4) The cation exchange membrane according to any one of the above (1) to (3), wherein the binder resin is a resin having no ion exchange capacity and / or a resin having a low ion exchange capacity.

[0013] (5) The cation exchange membrane according to the above (4), wherein the ion exchange capacity of the resin having a low ion exchange capacity is 0.001 to 0.2 meq / g.

[0014] (6) The cation exchange membrane according to any one of the above (1) to (5), wherein the cation exchange layer containing the metal cyano complex and the binder resin has, on one side or both sides, another cation exchange layer which does not contain the metal cyano complex.

[0015] (7) An ion exchange membrane unit in which a cation exchange membrane is disposed opposite to the cation exchange membrane according to any one of (1) to (6).

[0016] (8) An electrodialysis device which is an electrodialysis device provided with an anode, a cathode, a cation exchange membrane, and an anion exchange membrane, wherein the cation exchange membrane is the cation exchange membrane according to any one of (1) to (6).

[0017] (9) A method for producing a cation exchange membrane, wherein metal cyano complex particles, a binder resin, and a solvent are mixed, the metal cyano complex particles are dispersed in the mixed solution, the mixed solution is coated or cast, and the solvent is removed.

[0018] (10) A method for producing a cation exchange membrane, wherein, on a cation exchange layer in which metal cyano complex particles, a binder resin, and a solvent are mixed, the metal cyano complex particles are dispersed in the mixed solution, the mixed solution is coated or cast, and the solvent is removed, a liquid in which a resin for forming another cation exchange layer not containing a metal cyano complex and a solvent are mixed is coated and the solvent is removed, or another cation exchange membrane not containing a metal cyano complex is bonded.

[0019] Further, the present application is determined by the matters shown below.

[0020] (i) A cation exchange membrane having a cation exchange layer containing a metal cyano complex and a binder resin.

[0021] (ii) The cation exchange membrane according to (ii) above, wherein another cation exchange layer is provided on one side or both sides of the cation exchange layer containing a metal cyano complex and a binder resin.

[0022] (iii) The cation exchange membrane according to (i) or (ii) above, wherein the binder resin is a resin having no ion exchange ability and / or a resin having low ion exchange ability.

[0023] (iv) An ion exchange membrane unit in which a cation exchange membrane according to (i) or (ii) above is disposed opposite to an anion exchange membrane.

[0024] (v) An electrodialysis device which is an electrodialysis device provided with an anode, a cathode, a cation exchange membrane, and an anion exchange membrane, wherein the cation exchange membrane is the cation exchange membrane according to (i) or (ii) above.

[0025] Effects of the Invention The cation exchange membrane of the present application is excellent in selective permeability to specific cations, particularly ammonium ions. The ion exchange membrane unit of the present application is used in an apparatus such as electrodialysis, and can selectively concentrate specific cations, particularly ammonium ions. The electrodialysis apparatus of the present application can selectively concentrate specific cations, particularly ammonium ions. The cation exchange membrane, ion exchange membrane unit, and electrodialysis apparatus of the present application can improve energy efficiency at the time of dialysis. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 Figure 1 A schematic diagram showing an example of using the ion exchange membrane unit of the present application.

[0027] Figure 2 Figure 2 A scanning electron microscope (SEM) image of the pulverized metal cyano complex used in Example 1.

[0028] Figure 3 Figure 3 A scanning electron microscope (SEM) image of the pulverized metal cyano complex used in Example 2.

[0029] Figure 4 Figure 4 A scanning electron microscope (SEM) image of the film produced in Example 2.

[0030] Figure 5 Figure 5 A scanning electron microscope (SEM) image of the film produced in Example 3.

[0031] Figure 6 Figure 6 A scanning electron microscope (SEM) image of the film produced in Example 4.

[0032] Figure 7 Figure 7 A diagram showing a measuring apparatus and measuring conditions for measuring the resistance of the film used in the examples and comparative examples.

[0033] Figure 8 Figure 8 A diagram showing an electrodialysis test apparatus used in the examples and comparative examples.

[0034] Figure 9 Figure 9 A diagram showing the electrodialysis test results of Example 1.

[0035] Figure 10 Figure 10 A diagram showing the electrodialysis test results of Example 2.

[0036] ​​​​​​​​​​​​​​​​​​​​​Figure 11 ] Figure 11 A graph showing the results of the electrodialysis test in Example 3.

[0037] [ Figure 12 ] Figure 12 A graph showing the results of the electrodialysis test in Example 4.

[0038] [ Figure 13 ] Figure 13 A graph showing the results of the electrodialysis test in Example 5.

[0039] [ Figure 14 ] Figure 14 A graph showing the results of the electrodialysis test in Example 9.

[0040] [ Figure 15 ] Figure 15 A graph showing the results of the electrodialysis test for the comparative example. Detailed Implementation

[0041] The cation exchange membrane of the present invention is a cation exchange membrane having a cation exchange layer comprising a metal cyano complex (which has cation exchange capacity) and a binder resin. The metal cyano complex used in the present invention is not particularly limited; for example, it refers to a complex whose composition consists of A... x M[M'(CN)6] y The substance represented by ·zH2O. Here, the metal atom M is preferably one or more metal atoms selected from the group consisting of vanadium, chromium, manganese, iron, ruthenium, cobalt, rhodium, nickel, palladium, platinum, copper, silver, zinc, lanthanum, europium, gadolinium, lutetium, barium, strontium, and calcium; more preferably, one or more metal atoms selected from the group consisting of vanadium, chromium, manganese, iron, ruthenium, cobalt, nickel, copper, and zinc; and particularly preferably, one or more metal atoms selected from the group consisting of manganese, iron, cobalt, nickel, copper, and zinc. The metal atom M' is preferably one or more metal atoms selected from the group consisting of vanadium, chromium, molybdenum, tungsten, manganese, iron, ruthenium, cobalt, nickel, platinum, and copper; more preferably, one or more metal atoms selected from the group consisting of manganese, iron, ruthenium, cobalt, and platinum; and even more preferably, one or more metal atoms selected from the group consisting of iron and cobalt. A is a cation with a valence of 1 or more, preferably one or more cations selected from the group consisting of hydrogen, ammonium, alkali metals and alkaline earth metals, more preferably one or more cations selected from the group consisting of hydrogen, lithium, sodium, potassium, rubidium and cesium.

[0042] In addition, in the case where M and M' are identified, it is called an M-M' cyanometallate. For example, in the case where M = copper and M' = iron, it is called a copper-iron cyanometallate. X is preferably 0 to 3, more preferably 0 to 2.5, and further preferably 0 to 2. y is preferably 0.1 to 1.5, more preferably 0.4 to 1.3, and further preferably 0.5 to 1. z is preferably 0 to 6, more preferably 0.5 to 5.5, and further preferably 1 to 5. The crystal structure of the metal cyanometallate is usually a face-centered cubic structure, but is not necessarily limited thereto. For example, in the case where M = copper and M' = iron, it is a hexagonal structure. 0.67 Zn[Fe(CN)6] 0.67 zH2O. In addition, the cyanide group coordinated with M' is usually 6, but can be substituted with a nitro group or the like in part thereof, as long as it is within 4 to 8. The method of synthesizing the metal cyanometallate is not particularly limited, and a method capable of uniformly achieving the target composition is preferred. In addition, from the aspect of processing, the surface of the complex can be modified with various materials. As a specific method, for example, the method described in Japanese Patent Application Publication No. 2006-256954, Japanese Patent Application Publication No. 2013-173077, and the like can be used, and a nanoparticle having a large specific surface area is ideal. In addition, from the aspect of practical use, uniformity of the particles is ideal, and thus the uniform nanoparticle manufacturing method described in Japanese Patent Application Publication No. 2013-173077 and the like is suitable. The metal cyanometallate is provided in the form of a powder, a slurry dispersed in water, or the like, but the form thereof is not limited. As described later, it is important that the metal cyanometallate is uniformly mixed with the binder resin, and thus the form of the metal cyanometallate is also desired to be selected in combination with the binder. The metal cyanometallate described in Japanese Patent No. 5035767, Japanese Patent Application Publication No. 2008 / 081923, and the like can control the dispersibility in various solvents by adding metal ions, ferrocyanide ions, or organic molecules to the surface of the particles thereof. In the case where a binder dispersed in water is used, it is desired to improve the dispersibility of the metal cyanometallate in water, and in the case where a binder dispersed or dissolved in an organic solvent is used, it is desired to improve the dispersibility of the metal cyanometallate in the organic solvent.

[0043] As the binder resin in the present application, there is no particular limitation as long as it can fix the metal cyano complex particles to form a layer or film containing the metal cyano complex particles. As the binder resin in the present application, a resin in which the metal cyano complex particles are uniformly dispersed in the resin, i.e., a resin in which the complex particles are uniformly dispersed rather than unevenly distributed in the resin, is preferred. From the viewpoint of ease of mixing with the metal cyano complex particles, a resin having plasticity, particularly a resin having thermoplasticity, is preferred. In addition, from the same viewpoint as ease of mixing with the metal cyano complex particles, a resin dispersed in water or a resin dispersed or dissolved in an organic solvent, preferably a resin capable of being dissolved in a general-purpose organic solvent, can be used. In the present application, the binder resin having plasticity refers to a resin having a property of deforming by application of an external force and not returning to the original state even if the force is removed (in the case of having a support to be described later, it refers to a resin having the property together with the support), and includes: a polymer having plasticity at ordinary temperature; and a polymer having thermoplasticity that softens by heating, becomes easy to mold, and becomes hard again if cooled.

[0044] As the binder resin in the present application, a resin having no ion exchange capacity or a resin having a low ion exchange capacity lower than that of conventional ion exchange membranes is preferable. In the present application, the resin having a low ion exchange capacity means a resin having an ion exchange group, but having an ion exchange capacity smaller than that of conventional ion exchange membranes. As the ion exchange group, for example, cation exchange groups (anion groups) such as -CF2SO3H, -SO3H, -CF2COOH, -COOH, -PO3H2, -Phenolic OH, -C(CF3)3OH, -CF2SO2NHR, anion exchange groups (cation groups) such as -N(CH3)3OH, -N(CH2OH)(CH3)2OH, -S(CH3)2OH, -P(CH3)3OH, -NH2, -NH, Aniline (NH2), anion groups and cation groups described later, and the like are exemplified. As the ion exchange capacity when having a low ion exchange capacity, 0.001 to 0.2 meq / g is preferable, 0.005 to 0.1 meq / g is more preferable, 0.01 to 0.05 meq / g is further preferable, and 0.01 to 0.02 meq / g is particularly preferable. As the binder resin having no ion exchange capacity, specifically, for example, polyethylene, polypropylene, polyether sulfone, polyvinylidene fluoride, polyacrylonitrile, cellulose triacetate, polyvinyl alcohol, and the like are exemplified. In addition, as the binder resin in the present application, a polyolefin can be used. The polyolefin means a polymer of a compound having a double bond in the molecule. Specifically, polymers of aliphatic olefins such as the aforementioned polyethylene and polypropylene, polybutene, polybutadiene, polymers of aromatic olefins such as polystyrene, poly-a-methylstyrene, polydivinylbenzene, polymers of oxygen-containing olefins such as polymethyl methacrylate, polyvinyl acetate, the aforementioned polyvinyl alcohol, polymers of nitrogen-containing olefins such as the aforementioned polyacrylonitrile, poly-N-methylpyrrolidone, polymers of halogen-containing olefins such as polyvinyl chloride, polyvinylidene chloride, the aforementioned polyvinylidene fluoride, polytetrafluoroethylene, and the like are exemplified. These polyolefins can be used alone or in combination. In addition, a copolymer or graft copolymer of two or more of the aforementioned olefins can be used. In addition, polyether ketone, polyether ether ketone, polyphenylene, polyphenyl ether, modified polyphenyl ether, polyphenylene sulfide, polyether imide, and the like are exemplified. In the present application, one kind of binder resin can be used, or two or more kinds of binder resins can be used. In the case where a resin having a cation exchange capacity is used as the binder resin in the present application, if the binder resin portion allows other cations to permeate together with specific cations such as ammonium ions, the effect of the present application that the selective permeability of ammonium ions is excellent can be reduced, and in the case where a resin having an anion exchange capacity is used as the binder resin in the present application, anions can also permeate.Therefore, in the binder resin of the present application, in the case where a resin having an ion exchange group is used, it is preferable that the ion exchange capacity be within the range of the above-described ion exchange capacity, regardless of the case where a cation exchange group is present or the case where an anion exchange group is present.

[0045] In the binder resin of the present application, in the case where a resin having an ion exchange group is used, an ion exchange group of a cationic group or an anion group can be introduced to a nonionic polymer or the like which does not have an ion exchange group, or a cationic polymer or an anion polymer can be mixed in a nonionic polymer or the like which does not have an ion exchange group. The cationic polymer refers to a polymer having a cationic group (positive charge group) in the molecular chain, and the cationic group can be present in any of the main chain, side chain, and terminal. As the cationic group in the cationic polymer, the same as the aforementioned cationic group and in addition to these, an ammonium group, an iminium group, a sulfonium group, a phosphonium group, and the like can be exemplified. In addition, a polymer having a functional group such as an amino group, an imino group, which can be converted into an ammonium group, an iminium group in water, is also included in the cationic polymer in the present application. Among them, from the viewpoint of industrial availability, an ammonium group is preferable. As the ammonium group, any of a primary ammonium group (ammonium group), a secondary ammonium group (alkylammonium group, etc.), a tertiary ammonium group (dialkylammonium group, etc.), a quaternary ammonium group (trialkylammonium group, etc.) can be used, and a quaternary ammonium group (trialkylammonium group, etc.) is more preferable. The cationic polymer can contain only one kind of cationic group, or can contain a plurality of kinds of cationic groups. In addition, the counter anion of the cationic group is not particularly limited, and a halide ion, a hydroxide ion, a phosphate ion, a carboxylate ion, and the like can be exemplified. Among them, from the aspect of ease of handling, a halide ion is preferable, and a chloride ion is more preferable. The cationic polymer can contain only one kind of counter anion, or can contain a plurality of kinds of counter anions. The cationic polymer used in the present application can be a polymer composed of only a structural unit having a cationic group, or can be a polymer composed of both a structural unit having a cationic group and a structural unit not having a cationic group. In addition, these polymers can have cross-linkability. The cationic polymer can be composed of only one kind of polymer, or can include a plurality of kinds of polymers. In addition, it can also be a mixture of a polymer having these cationic groups and a polymer not having a cationic group.

[0046] The anionic polymer is a polymer having an anionic group (negative charge group) in the molecular chain. The anionic group can be included in any of the main chain, side chain, and terminal end. As the anionic group in the anionic polymer, the same as and other than the aforementioned anionic group, sulfonate group, carboxylate group, phosphonate group, and the like can be exemplified. In addition, a polymer having a functional group such as a sulfonic acid group, a carboxyl group, and a phosphonic acid group, which can be converted into a sulfonate group, a carboxylate group, and a phosphonate group in water, is also included in the anionic polymer in the present application. Among them, from the viewpoint of a large ion dissociation constant, a sulfonate group is preferable. The anionic polymer can contain only one anionic group, or can contain a plurality of anionic groups. In addition, the counter anion of the anionic group is not particularly limited, and a hydrogen ion, an alkali metal ion, and the like can be exemplified. Among them, from the viewpoint of less corrosion of the equipment, an alkali metal ion is preferable. The anionic polymer can contain only one counter cation, or can contain a plurality of counter cations. The anionic polymer used in the present application can be a polymer composed of only a structural unit containing an anionic group, or can be a polymer composed of both a structural unit containing an anionic group and a structural unit not containing an anionic group. In addition, these polymers can have cross-linkability. The anionic polymer can be composed of only one polymer, or can include a plurality of polymers. In addition, it can also be a mixture of a polymer containing these anionic groups and a polymer not containing an anionic group.

[0047] In addition, in order to improve the dispersibility of the metal cyano complex in the binder resin, the cation exchange layer (hereinafter, also referred to as "the cation exchange layer in the present application") in the present application, which contains the metal cyano complex and the binder resin, can contain a third component other than the binder resin. In the present application, even if the permeation of ions other than the target ions occurs, the dispersibility of the metal cyano complex is preferentially improved, and the addition of the third component to the binder resin is not hindered. The third component is different from the direct surface treatment of the metal cyano complex particles themselves, and is a component mixed with the binder resin. As the third component, for example, the aforementioned nonionic polymer, cationic polymer, anionic polymer, and the like can be exemplified.

[0048] In the cation exchange layer of the present application containing the metal cyano complex and the binder resin, the metal cyano complex particles are dispersed in the binder resin to form the cation exchange layer. The cation exchange layer of the present application is not particularly limited as long as it is a layer in which the metal cyano complex particles are fixed by the binder resin. For example, it can be a layer in which the entire or a part of the surface of the metal cyano complex particles is embedded in the binder resin to fix the metal cyano complex particles, or it can be a layer in which the metal cyano complex particles are fixed by filling the binder resin between the metal cyano complex particles. The cation exchange layer of the present application can be composed only of the metal cyano complex and the binder resin, or it can contain components other than the metal cyano complex and the binder resin. In addition, the cation exchange membrane of the present application can be composed only of the cation exchange layer containing the metal cyano complex and the binder resin, or it can contain, in addition to the cation exchange layer containing the metal cyano complex and the binder resin, for example, other cation exchange layers, a support, and the like, which will be described later. In the case where the cation exchange membrane of the present application is composed only of the cation exchange layer containing the metal cyano complex and the binder resin, the cation exchange layer containing the metal cyano complex and the binder resin is in the form of a film, and the cation exchange membrane of the present application is a cation exchange membrane containing the metal cyano complex and the binder resin. The cation exchange layer or the cation exchange membrane containing the metal cyano complex and the binder resin has excellent selective permeability to ammonium ions.

[0049] The ratio of the contents of the metal cyano complex and the binder resin in the cation exchange layer of the present application containing the metal cyano complex and the binder resin is not particularly limited, and the metal cyano complex : binder resin is preferably 0.2 : 1 to 5 : 1, more preferably 0.5 : 1 to 3 : 1, still more preferably 0.75 : 1 to 2 : 1, and further more preferably 0.9 : 1 to 1.8 : 1, in terms of mass ratio. That is, the proportion of the mass of the metal cyano complex with respect to the mass of the binder resin is preferably 0.2 or more and 5 or less, more preferably 0.5 or more and 3 or less, still more preferably 0.75 or more and 2 or less, and further more preferably 0.9 or more and 1.8 or less. In the case where the content of the metal cyano complex is less than the lower limit value of the preferable mass ratio range, the membrane resistance becomes high, and in addition, the selective permeability to monovalent cations, particularly ammonium ions, can decrease. On the other hand, in the case where the content of the metal cyano complex is greater than the upper limit value of the preferable mass ratio range, the mechanical strength of the membrane can decrease, or the selective permeability to ammonium ions, particularly, can decrease.

[0050] The particle size of the metal cyano complex particles contained in the cation exchange layer in the present application is not particularly limited, and the crystallite size, which is evaluated using the Scherrer formula from the line width of the X-ray pattern using X-ray structural diffraction, is preferably 2 μm or less, and more preferably 0.005 to 0.5 μm. The metal cyano complex sometimes exists in the cation exchange layer as a primary particle of the crystallite size, a primary particle in which a plurality of crystalline particles are combined, or a secondary particle in which primary particles are aggregated by intermolecular forces or the like, and in the case of existing as a primary particle in the cation exchange layer, the primary particle size is preferably 5 μm or less, and more preferably 2 μm or less, and in the case of existing as a secondary particle, the secondary particle size is preferably 5 μm or less, and more preferably 2 μm or less. In addition, it is preferable that the primary particle size in the cation exchange layer be 0.005 to 1.0 μm, and the secondary particle size be 0.1 to 5 μm. The primary particle size and the secondary particle size in the cation exchange layer can be found by observation based on a scanning electron microscope (SEM). As the shape of the primary particle and the secondary particle, there are amorphous, roughly elliptical, roughly spherical, and the like, and therefore, here, the length of a straight line connecting two points on the outer edge of a particle when the length of the straight line becomes the largest from the SEM image is referred to as the primary particle size or the secondary particle size. Here, the above-mentioned preferable range means that 90% or more, and more preferably 95% or more of the number of the metal cyano complex particles in the cation exchange layer is within the range. For example, 5 μm or less means that 90% or more, and more preferably 95% or more of the number of the metal cyano complex particles is 5 μm or less. When the primary particle size or the secondary particle size exceeds 5 μm, the passage region of the cation becomes narrow, the membrane resistance can become large, and in addition, unevenness can be formed on the surface of the membrane, and from this point, the mechanical strength decreases, and the like. Furthermore, in the case where the primary particle size or the secondary particle size is greater than 5 μm, the amount of the binder resin adhered to the particles becomes sparse, and one or a plurality of gaps in which neither the particles nor the resin exist can be generated, and the cation can also short pass in the gap.

[0051] The thickness of the cation exchange layer containing the metal cyano complex and the binder resin in the present application is not particularly limited, and is preferably 5 to 300 μm, and more preferably 10 to 100 μm. If the thickness of the aforementioned cation exchange layer is too thin, the mechanical strength can decrease, and if it is too thick, the resistance can become high. In addition, in the case of the aforementioned cation exchange layer of the cation exchange membrane of the present application or the cation exchange membrane of the present application consisting only of the cation exchange layer containing the metal cyano complex and the binder resin, the membrane resistance representing the resistance is preferably 0.2 to 15 Ωcm 2 , more preferably 0.3 to 10 Ωcm 2 , or further preferably 0.5 to 5 Ωcm 2 .

[0052] In the cation exchange layer containing the metal cyano complex and the binder resin, a specific cation selectively migrates within the particles of the metal cyano complex and permeates outside the layer thereof, thereby being concentrated by separation, and thus the particles of the metal cyano complex are desired to be dispersed rather than unevenly distributed within the layer. In the state of uniform dispersion, as described above, in the cation exchange layer containing the metal cyano complex particles in a prescribed mass ratio with respect to the binder resin, in other words, in the cation exchange layer containing the metal cyano complex particles in a prescribed content ratio, adjacent particles are in contact with each other, and via the contact sites thereof, cations can pass through from within the layer while migrating within the particles like a string of beads. This point becomes a condition for the existence of the particles different from the case where target ions are adsorbed to the particles in a liquid. The content ratio within the cation exchange layer needs to be a certain degree, but in the case where the content ratio is excessively high in the whole of the layer or a part of the layer, as in the case where the primary particle diameter or the secondary particle diameter of the metal cyano complex exceeds a prescribed size as described above, the binder resin adhered to the particles becomes sparse, and one or more gaps can be generated. If cations other than the target to be concentrated and separated pass through in a short-circuiting manner from the gaps generated in the cation exchange layer in such a manner, an obstacle to the separation and recovery of the target cations can be caused. In addition, if anions pass through from the gaps in the opposite direction to the cations, a decrease in energy efficiency such as current efficiency can be caused. Furthermore, a decrease in mechanical strength of the cation exchange layer is also feared. Thus, it is sometimes necessary to provide another cation exchange layer described below on the cation exchange layer containing the metal cyano complex and the binder resin.

[0053] The cation exchange membrane of the present application can have other cation exchange layers on one side or both sides of the cation exchange layer containing the metal cyano complex and the binder resin. Hereinafter, the so-called other cation exchange layer refers to a cation exchange layer that is not the cation exchange layer containing the metal cyano complex and the binder resin. As the other cation exchange layer, it is preferable that it be a cation exchange layer that does not contain the metal cyano complex, and it is further preferable that it be a cation exchange layer having an ion exchange capacity of cations of more than 0.2 meq / g. In addition, as the other cation exchange layer, it is preferable that it not contain the metal cyano complex and the binder resin. Here, the so-called not containing the metal cyano complex and the binder resin does not exclude the inclusion of a trace amount of the metal cyano complex or the binder resin to the extent that it does not hinder the function of the other cation exchange layer in the present application. In the cation exchange layer containing the metal cyano complex and the binder resin, cations and / or anions can pass through and migrate from the gaps formed as described above, making it difficult to achieve the separation and recovery of the target cations, or the current efficiency decreases. The anions in this case move in the opposite direction to the cations in the cation exchange layer in the present application. Therefore, by forming the other cation exchange layer, it is possible to prevent the permeation of the cations and the anions in the gaps, making it easy to perform the separation and recovery of the target cations, and preventing the decrease in the current efficiency. In addition, by forming the other cation exchange layer, it is possible to improve the mechanical strength of the ion exchange membrane. As the material of the other cation exchange layer, there is no particular limitation, and any material that can be used as a cation exchange membrane can be used, and it is preferable that it be a material having high adhesion to the binder resin, and it is further preferable that it be a material having low membrane resistance and high mechanical strength. As the material constituting the other cation exchange layer, for example, sulfonated polyether sulfone, polyvinyl alcohol copolymer, and the like can be given. As the polyvinyl alcohol copolymer, PVA-b-PSS, PVA-b-VBTAC, and the like described in WO 2016 / 133170 can be given. In addition, for example, the anionic polymer described above in the cation exchange layer containing the metal cyano complex and the binder resin can be given. In addition, a resin that does not have ion exchange ability can be used by being mixed with a resin having ion exchange ability, such as polyether sulfone and sulfonated polyether sulfone. A resin that does not have ion exchange ability can also be used by using a resin in which a base material that does not have ion exchange ability is provided with ion exchange ability. As the resin that does not have ion exchange ability, for example, the nonionic polymer in the cation exchange layer containing the metal cyano complex and the binder resin can be used, and as the ion exchange group for providing it with ion exchange ability, the ion exchange group (anionic group) described above can be used as well. As the other cation exchange layer in the present application, a cation exchange layer formed of an anionic polymer can be given.

[0054] The thickness of the other cation exchange layer is not particularly limited, and is preferably 1 to 100 μm, more preferably 2 to 50 μm. If the thickness of the other cation exchange layer is too thin, the mechanical strength can decrease, and if the thickness is too thick, the membrane resistance can be too high. The ratio of the thickness of the cation exchange layer containing the metal cyano complex and the binder resin to the thickness of the other cation exchange layer (in the case where the other cation exchange layer is present on both sides, the sum of the thicknesses of both sides. The same applies hereinafter.) is preferably 1 : 0.1 to 1 : 100, more preferably 1 : 0.3 to 1 : 50, and further preferably 1 : 0.5 to 1 : 10. That is, when the thickness of the cation exchange layer containing the metal cyano complex and the binder resin is set to 1, the ratio of the thickness of the other cation exchange layer is preferably 0.1 or more and 100 or less, more preferably 0.3 or more and 50 or less, and further preferably 0.5 or more and 10 or less.

[0055] The thickness of the cation exchange membrane provided with the other cation exchange layer on one side or both sides of the cation exchange layer containing the metal cyano complex and the binder resin is not particularly limited, and is preferably 10 to 400 μm, more preferably 20 to 200 μm, and further preferably 25 to 120 μm. In addition, the membrane resistance of the cation exchange membrane provided with the other cation exchange layer is preferably 0.5 to 10 Ωcm 2 , 0.7 to 5 Ωcm 2 .

[0056] The cation exchange membrane of the present application can have a support. By having a support, the mechanical strength is improved. The support can be present in the cation exchange layer containing the metal cyano complex and the binder resin, and in the case where the other cation exchange layer is present, the support can be present in the other cation exchange layer, or on one side or both sides of the cation exchange membrane of the present application. The support is not particularly limited as long as it has an opening, and for example, a net, a nonwoven fabric, a woven fabric, various porous membranes, and the like can be mentioned.

[0057] The method for producing the ion exchange membrane of the present application is not particularly limited, and for example, a method in which metal cyano complex particles, a binder resin, and a solvent are mixed, the metal cyano complex particles are sufficiently dispersed in the mixed solution, the mixed solution is coated, cast, or the like, and the solvent is removed to produce a film shape can be mentioned. As the method for forming the other cation exchange layer, a method in which a resin for forming the other cation exchange layer is mixed with a solvent, coated on the cation exchange layer containing the metal cyano complex and the binder resin, and the solvent is removed, a method in which a cation exchange membrane for forming the other cation exchange layer is bonded to the cation exchange layer containing the metal cyano complex and the binder resin, or the like can be mentioned. In the case of the metal cyano complex particles used in the production of the cation exchange membrane of the present application, the crystallite size obtained by evaluating the line width of the X-ray pattern using the Scherrer formula by X-ray structure diffraction is preferably 2 μm or less, and preferably 0.005 to 0.5 μm. The metal cyano complex particles used sometimes exist as primary particles of the crystallite size, primary particles in which a plurality of crystal sub-particles are combined, or secondary particles in which primary particles are aggregated by intermolecular forces or the like. In the case of existing as primary particles, the primary particle diameter is preferably 5 μm or less, and more preferably 2 μm or less. In the case of existing as secondary particles, the secondary particle diameter is preferably 5 μm or less, and more preferably 2 μm or less. In addition, the primary particle diameter of the metal cyano complex particles used is preferably 0.005 to 1.0 μm, and the secondary particle diameter is preferably 0.1 to 5 μm. The primary particle diameter and the secondary particle diameter can be found by a scanning electron microscope by the same method as in the above

[0021] section. It is preferable to uniformly disperse the metal cyano complex particles in the binder resin in a manner in which the primary particle diameter and the secondary particle diameter of the metal cyano complex particles in the produced cation exchange layer become the particle diameters in the above preferable range of the cation exchange layer. In the case of using a support, for example, the mixed solution in which the metal cyano complex particles, the binder resin, and the solvent are mixed can be coated on a support such as a net, a non-woven fabric, a woven fabric, a porous membrane, or the like, the mixed solution can be impregnated in the support, or the support can be dipped in the mixed solution, and then the solvent is removed, whereby a cation exchange membrane having a support can be produced. As the solvent, there is no particular limitation, and a substance in which the binder resin is easily dispersed or dissolved and the metal cyano complex particles are easily dispersed is preferable. As the solvent, for example, solvents such as hydrocarbons such as benzene, xylene, toluene, hexane, alcohols such as methanol, ethanol, isopropanol, ketones such as acetone, methyl isopropyl ketone, cyclohexane, ethers such as dioxane, tetrahydrofuran, esters such as ethyl acetate, butyl acetate, nitrogen-containing compounds such as isopropylamine, diethanolamine, N-methylformamide, N,N-dimethylformamide, dimethyl sulfoxide, or the like can be used, and at least one or more of these can be appropriately selected and used.

[0058] As for the ion exchange membrane unit of the present application, the anion exchange membrane is disposed opposite to the cation exchange membrane of the present application. The anion exchange membrane in the ion exchange membrane unit of the present application is not particularly limited as long as it is a membrane selectively permeable to anions. Figure 1 Among them, as a use example of the ion exchange membrane unit of the present application, an example in which the ion exchange membrane unit of the present application is stacked to form a stack for an electrodialysis device is shown. In the case where another cation exchange layer is provided on one side, it is preferable to make the cation exchange layer containing a metal cyano complex and a binder resin face the anode side. In the case where another anion exchange layer is provided on one side, it is preferable to make the anion exchange layer containing a metal cyano complex and a binder resin face the cathode side. Figure 1 In the electrodialysis device of the present application, a dilution side solution is flown to the anode side of the cation exchange membrane of the present application, and a concentration side solution is flown to the cathode side. A solution containing various ions is introduced to the dilution side, and during the passage of the introduced solution between the anion exchange membrane and the cation exchange membrane of the present application, as a specific cation in the solution, for example, an ammonium ion selectively permeates the cation exchange membrane of the present application to move to the concentration side. In this way, the ammonium ion is concentrated on the concentration side. In the dilution side solution, various ions can be present, and by the selectivity of the cation exchange membrane of the present application, it is possible to selectively concentrate a specific cation. As the various cations present in the dilution side solution, there is no particular limitation, and for example, alkali metal ions, alkaline earth metal ions, other 1- to 3-valent cations, for example, ammonium ions, sodium ions, potassium ions, lithium ions, calcium ions, magnesium ions, hydrogen ions, and heavy metal ions such as silver ions, copper, zinc, mercury, and the like can be mentioned. As the various anions present in the dilution side solution, there is no particular limitation, and for example, hydroxide ions, chloride ions, bromide ions, fluoride ions, iodide ions, carbonate ions, nitrate ions, sulfate ions, phosphate ions, and the like can be mentioned. As the solution introduced to the concentration side, there is no particular limitation, and for example, raw water as a concentration target, water in which a specific ion in the raw water is concentrated, or water, and the like can be mentioned, and can also contain the above various ions contained in the dilution side solution. As the water, tap water, industrial water, pure water, and the like can be used. In the case where the dilution side solution is introduced to the concentration side, the concentration side solution can be introduced to the dilution side. Figure 1 In the electrodialysis device of the present application, the description of the gasket provided between the ion exchange membranes and having a mesh, the power source for supplying electric power to the anode and the cathode, the piping for supplying solutions to the dilution side and the concentration side, the pump, and the like is omitted. These can be used, for example, devices generally used in an electrodialysis device.

[0059] In the cation exchange membrane and the electrodialysis apparatus of the present application, in the case where the other cation exchange layer is provided on one side, by arranging the cation exchange layer containing the metal cyano complex and the binder resin toward the anode side, i.e., arranging the other cation exchange layer toward the cathode side, it is possible to further improve the effect of preventing the migration of anions from the cathode side to the anode side, and it is possible to improve the current efficiency. On the contrary, if the cation exchange layer containing the metal cyano complex and the binder resin is arranged toward the cathode side, i.e., the other cation exchange layer is arranged toward the anode side, when the specific cation is an ammonium ion, cations other than the ammonium ion are also distributed at a high concentration into the other cation exchange layer, and thus the selectivity of the ammonium ion can decrease, and the blocking property of anions can decrease as compared with the case where the other cation exchange layer is arranged toward the cathode side. The above describes the case where the other cation exchange layer is provided on one side or both sides of the cation exchange layer containing the metal cyano complex and the binder resin, and in the case where the other cation exchange layer is provided, it is possible to apply not only to the cation exchange layer containing the metal cyano complex and the binder resin, but also to the cation exchange layer containing the inorganic cation exchanger and the binder resin. In this case, the other cation exchange layer means a cation exchange layer other than the cation exchange layer containing the inorganic cation exchanger and the binder resin. As the inorganic ion exchanger, there is no particular limitation, and for example, antimony pentoxide, zirconium phosphate, polyantimony acid, crystalline antimony acid, and the like can be mentioned. However, as the inorganic cation exchanger in the cation exchange membrane of the present application having the other cation exchange layer on one side or both sides of the cation exchange layer containing the inorganic ion exchanger and the binder resin, zeolite is excluded, which is difficult to be directly used for ion exchange purposes, and the particles after pulverization are likely to aggregate. In the cation exchange membrane of the present application having the other cation exchange layer on one side or both sides of the cation exchange layer containing the inorganic cation exchanger and the binder resin, the binder resin and other components in the cation exchange layer containing the inorganic cation exchanger and the binder resin, the raw materials in the cation exchange membrane, and the manufacturing method and manufacturing conditions, and the like are the same as those described in the cation exchange membrane having the cation exchange layer containing the metal cyano complex and the binder resin.

[0060] Example Hereinafter, examples of the present application will be described specifically, but the technical scope of the present application is not limited to these examples.

[0061] The polymer, the adsorbent material, and the ion exchange membrane used in the examples and the comparative examples were prepared as follows.

[0062] 1. Polyether sulfone (SUMIKAEXCEL PES (grade: 5900P), manufactured by Sumitomo Chemical Co., Ltd., hereinafter referred to as PES.) 2. Sulfonated polyether sulfone (EW0710, made by Shokubai Kogyo Co., Ltd., hereinafter referred to as SPES.) 3. Metal cyano complex K2Cu3[Fe(CN)6]2 (hereinafter, also referred to as KCuHCF). 4. Metal cyano complex K2Zn3[Fe(CN)6]2 (hereinafter, also referred to as KZnHCF). 5. Standard cation exchange membrane Neosepta (registered trademark) CSE (made by Asahi Glass Co., Ltd.) (Preparation of KCuHCF) A raw material solution A prepared by dissolving copper sulfate 5 hydrate 97 g in 555 mL of water, and a raw material solution B prepared by dissolving potassium ferrocyanide trihydrate 110 g in 555 mL of water were mixed, thereby obtaining a KCuHCF slurry containing KCuHCF 100 g (assuming tetrahydrate). Next, using decantation and centrifugal separation, potassium sulfate as a by-product was removed, thereby obtaining a KCuHCF slurry of which cleaning was completed. Further, potassium ferrocyanide trihydrate 41 g was added, and shaking was performed for 3 days, thereby obtaining a KCuHCF slurry of which surface treatment was completed.

[0063] (Preparation of KZnHCF) A raw material solution C prepared by dissolving zinc salt 0.38 mole in 537 mL of water, and a raw material solution D prepared by dissolving potassium ferrocyanide trihydrate 0.26 mole in 551 mL of water were mixed, thereby obtaining a KZnHCF slurry containing KZnHCF 100 g (assuming tetrahydrate). Next, using decantation and centrifugal separation, potassium sulfate as a by-product was removed, thereby obtaining a KZnHCF slurry of which cleaning was completed. Further, potassium ferrocyanide trihydrate 41 g was added, and shaking was performed for 3 days, thereby obtaining a KZnHCF slurry of which surface treatment was completed.

[0064] [Example 1] A KCuHCF slurry of which cleaning was completed was dried, and 2 g of the dried KCuHCF was put in a mortar, and was ground and pulverized using a pestle for 4000 times. Figure 2An image obtained by observing the crushed KCuHCF particles with a scanning electron microscope (SEM) (KEYENCE, VE-8800) is shown. The crushed KCuHCF particles form secondary particles, and the secondary particle diameter thereof was calculated from the SEM image in the same manner as in the paragraph

[0021] , and was found to be 0.2 μm or less. PES was added to N,N-dimethylacetamide (DMAc) so that the concentration of PES would be 20 mass%, and was dissolved by heating to 60°C in an oil bath while stirring with a magnetic stirrer. The crushed KCuHCF particles were added to the previously prepared DMAc solution of PES so that the mass ratio of KCuHCF : PES would be 1 : 1, and were mixed with a magnetic stirrer for 1 hour to disperse them in the DMAc solution of PES. Then, the solution was degassed in an ultrasonic bath for 10 minutes. The solution obtained in the above manner was applied to a glass plate using a film applicator (Cortec Corporation, KT-3405) with the set height of the applicator set to 0.3 mm, and was formed into a film shape. Then, the DMAc was evaporated by drying on a hot plate at 60°C for 1 hour, and a film containing KCuHCF (hereinafter, also referred to as a KCuHCF film) was obtained. The obtained film was immersed in ion-exchange water and was peeled off from the glass plate. The secondary particle diameter of the KCuHCF particles in the KCuHCF film was also substantially the same as the secondary particle diameter after crushing.

[0065] [Example 2] The washed KZnHCF slurry was dried, and 2 g of the dried KZnHCF was put into a mortar and was crushed by grinding with a pestle for 4000 times. Figure 3 An image obtained by observing the crushed KZnHCF particles with a scanning electron microscope (SEM) is shown. The crushed KZnHCF particles form secondary particles, and the secondary particle diameter thereof was measured in the same manner as in Example 1, and was found to be in the range of 0.5 to 1.0 μm. The metal cyano complex was replaced from KCuHCF to KZnHCF, and otherwise, the same operation as in Example 1 was performed, and a film containing KZnHCF (hereinafter, also referred to as a KZnHCF film) was obtained. The secondary particle diameter of the KZnHCF particles in the KZnHCF film was also substantially the same as the secondary particle diameter after crushing. The obtained film was immersed in ion-exchange water and was peeled off from the glass plate. Figure 4 The results of observing the cross section and the film surface of the produced film with a scanning electron microscope are shown. Figure 4 (a) is the observation result of the cross section, Figure 4 (b) is the observation result of the film surface.

[0066] [Example 3] The same operation as in Example 2 was performed except that the mixing ratio (mass ratio) of KZnHCF to PES, i.e., KZnHCF:PES was 1.5:1, to obtain a film containing KZnHCF. Figure 5 The results obtained by observing the cross section and the film surface of the produced film with a scanning electron microscope are shown. Figure 5 (a) is the observation result of the cross section, Figure 5 (b) is the observation result of the film surface.

[0067] [Example 4] The same operation as in Example 2 was performed except that the mixing ratio (mass ratio) of KZnHCF to PES, i.e., KZnHCF:PES was 1.9:1, to obtain a film containing KZnHCF. Figure 6 The results obtained by observing the cross section and the film surface of the produced film with a scanning electron microscope are shown. Figure 6 (a) is the observation result of the cross section, Figure 6 (b) is the observation result of the film surface.

[0068] [Example 5] The same operation as in Example 2 was performed to prepare a solution in which the same pulverized KZnHCF particles as those used in Example 2 were dispersed in a DMAc solution of PES. The prepared solution was coated on a glass plate in the same manner as in Example 2 to be shaped into a film. Then, the film was dried on a hot plate at 60°C for 30 minutes to evaporate a part of DMAc. On the other hand, SPES was added to DMAc so as to have a concentration of 20 mass% and dissolved. The solution in which SPES was dissolved in DMAc was added dropwise to the KZnHCF-containing film dried before, and coated using a film applicator. After the coating, the glass plate was dried on a hot plate at 60°C for 1 hour or more to evaporate DMAc, to obtain a film including a cation exchange layer containing KZnHCF and a cation exchange layer based on SPES (hereinafter, also referred to as a composite film). The obtained composite film was immersed in ion exchange water and peeled from the glass plate.

[0069] [Example 6] The same operation as in Example 5 was performed except that the mixing ratio (mass ratio) of KZnHCF to PES, i.e., KZnHCF:PES was 1.5:1, to obtain a composite film.

[0070] [Example 7] The same operation as in Example 6 was performed to obtain a composite film. However, the cation exchange layer based on SPES was made thicker than in Example 6.

[0071] [Example 8] Except that the ratio (mass ratio) of KZnHCF to PES, i.e. KZnHCF:PES, was set to 2.0:1, the same procedure as in Example 5 was followed to obtain the composite membrane.

[0072] (Measurement of film thickness) The thickness of the obtained film was measured using a film thickness gauge (ABS digital blade thickness gauge, Mitutoyo Corporation).

[0073] (Measuring membrane resistance) Figure 7 The apparatus and conditions for measuring film resistance are shown. First, a current-carrying area of ​​0.949 cm² with a platinum electrode is used. 2 An aqueous solution of NH4Cl (0.5 mol / L) was added to the acrylic resin cell as the test solution. The solution resistance (R0) at 25°C was measured using an LCR meter at a frequency of 10 kHz. Then, the sample membrane was clamped between the two cells, and the resistance (R1) was measured in the same way. The membrane resistance (R) was calculated according to the following formula (1). m Divide the obtained film resistance by the film thickness, and then calculate the film resistivity K according to equation (2). m [Ωcm]. In equation (1), R1[Ωcm] 2 R0[Ωcm] is the measurement resistance measured when the sample membrane is sandwiched between two cells. 2 R is the solution resistance measured without clamping the sample film. m [Ωcm 2 [ ] represents the film resistance. In equation (2), K m [Ωcm] represents the film resistivity, and d[cm] represents the film thickness.

[0074] [Mathematical Expression 1] [Mathematical Expression 2] (Electrodialysis) exist Figure 8 The effective membrane area shown is 4.0 cm². 2 The measuring membrane was clamped in a 2.0cm × 2.0cm apparatus. Under a 25°C atmosphere, a mixed salt solution of 0.1M NH₄Cl, 0.1M NaCl, and 0.2M CaCl₂ was placed in two cells. Electrodialysis was performed for approximately 120 minutes at a constant current of 90mA between the Ag·AgCl electrodes using a DC stabilized power supply (PMC35-2A, Kikusui Electronics Co., Ltd.). Samples of the solution in the cells were taken at predetermined intervals. Then, ion chromatography was used to analyze the NH₄Cl in the sampled solution. 4+ Na+ and Ca 2+ The concentrations of these ions were quantified, and thus the changes in the concentrations of these ions over time were measured. From these values, the flux of each ion was calculated using the following equation. In Equation (3), J i [mol-m -2 -s -1 ] represents the permeation flux, V [m 3 ] represents the volume of the concentrated side solution, S [m 2 ] represents the effective membrane area, t [s] represents the time during which the current flows, and ΔC i / Δt [mol-m -3 -s -1 ] represents the initial concentration gradient. In addition, i represents NH4 + , Na + , or Ca 2+ . In Equations (4) and (5), P NH4 Na and P NH4 Ca represent the ion selectivity permeability coefficient [-]. In Equation (6), η [-] represents the current efficiency, z i [-] represents the valence of the cation, I [A] represents the current, and F [C-mol -1 ] represents the Faraday constant. Here, the effective membrane area refers to the membrane area through which ion permeation actually occurs.

[0075] [Equation 3] [Equation 4] [Equation 5] [Equation 6] (Measurement results of Example 1) The film thickness of the KCuHCF film obtained in Example 1 was 61 μm, and the film resistivity of the film was 1885 Ωcm, and the film resistance was 11.5 Ωcm 2 . Figure 9 The results of electrodialysis using this film are shown. This figure shows the changes in the ion concentrations of the concentrated side and the dilute side with respect to NH4 + , Na + , and Ca 2+ ions over time. By the applied direct current voltage, all of these three cations migrated from the dilute side to the concentrated side, and from the slope of the time-concentration curve, the permeation flux was calculated using Equation (3), and the ion selectivity coefficient was calculated from Equations (4) and (5). As a result, P NH4Na P NH4 Ca P + NH4+ + selectively permeates, and further indicates that NH4+ 2+ NH4+ + selectively permeates. Further, the current efficiency at this time is 0.82.

[0076] (Measurement results of Example 2) The KZnHCF film obtained in Example 2 had a film thickness of 36 μm, and the film resistivity of the film was 937 Ωcm, and the film resistance was 3.37 Ωcm 2 . Figure 10 The results of electrodialysis using this film are shown. The graph shows the changes in the ion concentrations of NH4+ + , Na+ + , and Ca+ 2+ ions on the concentrated side and the dilute side with time. By the direct current voltage applied, all of the three cations migrate from the dilute side to the concentrated side, and from the slope of the time-concentration curve, the permeation flux is calculated using Equation (3), and the ion selectivity coefficient is calculated from Equations (4) and (5). As a result, P NH4 Na P NH4 Ca P + NH4+ + selectively permeates, and further indicates that NH4+ 2+ NH4+ + selectively permeates. Further, the current efficiency at this time is 0.89.

[0077] (Measurement results of Example 3) The KZnHCF film obtained in Example 3 had a film thickness of 45 μm, and the film resistivity of the film was 416 Ωcm, and the film resistance was 1.86 Ωcm 2 . Figure 11 The results of electrodialysis using this film are shown. The graph shows the changes in the ion concentrations of NH4+ + , Na+ + , and Ca+ 2+ ions on the concentrated side and the dilute side with time. By the direct current voltage applied, all of the three cations migrate from the dilute side to the concentrated side, and from the slope of the time-concentration curve, the permeation flux is calculated using Equation (3), and the ion selectivity coefficient is calculated from Equations (4) and (5). As a result, P NH4 Na P NH4 Ca40.4. This indicates that NH4+ + 34.6 times as much as Na+ + selectively permeates, and further indicates that NH4+ 2+ 40.4 times as much as Ca+ + selectively permeates. Further, the current efficiency at this time was 0.88.

[0078] (Measurement results of Example 4) The KZnHCF film obtained in Example 4 had a film thickness of 57 μm, and the film resistivity of the film was 93 Ωcm, and the film resistance was 0.53 Ωcm 2 . Figure 12 Results of electrodialysis using the film are shown. The graph shows the ion concentration on the dilution side and the concentration side of NH4+ + , Na+ + , and Ca+ 2+ ions with respect to time. By the direct current voltage applied, all of the three cations migrated from the dilution side to the concentration side, and from the slope of the time-concentration curve, the permeation flux was calculated using Equation (3), and the ion selectivity coefficient was calculated from Equations (4) and (5). As a result, P NH4 Na 4.2, P NH4 Ca 4.2. This indicates that NH4+ + 4.2 times as much as Na+ + selectively permeates, and further indicates that NH4+ 2+ 4.2 times as much as Ca+ + selectively permeates. Further, the current efficiency at this time was 0.52.

[0079] (Measurement results of Example 5) As for the composite film obtained in Example 5, the film thickness of the KZnHCF film was 49 μm, the film thickness of the SPES film was 24 μm, and the film resistivity of the entire film in which the two were combined was 272 Ωcm, and the film resistance was 1.99 Ωcm 2 . Figure 13 Results of electrodialysis using the film are shown. In Example 5, the composite film was disposed in such a manner that the SPES film faces the cathode side, and electrodialysis was performed. The graph shows the ion concentration on the dilution side and the concentration side of NH4+ + , Na+ + , and Ca+ 2+ ions with respect to time. By the direct current voltage applied, all of the three cations migrated from the dilution side to the concentration side, and from the slope of the time-concentration curve, the permeation flux was calculated using Equation (3), and the ion selectivity coefficient was calculated from Equations (4) and (5). As a result, P NH4 Na 9.0, P NH4Ca 26.3. This indicates that NH4+ + + selectively permeates, and in addition, the current efficiency at this time was 0.94. The current efficiency of the composite film obtained in Example 5 was higher than that of the film obtained in Example 2. In addition, the mechanical strength was also improved. 2+ 26.3 times as high as that of Ca2+ + selectively permeates. In addition, the current efficiency at this time was 0.94. The current efficiency of the composite film obtained in Example 5 was higher than that of the film obtained in Example 2. In addition, the mechanical strength was also improved.

[0080] (Measurement results of Example 6) As for the composite film obtained in Example 6, the film thickness of the KZnHCF film was 45 μm, the film thickness of the SPES film was 14 μm, and the film resistivity of the entire film in which both were combined was 550 Ωcm, and the film resistance was 3.05 Ωcm 2 . In Example 6, the composite film was disposed in such a manner that the SPES film faces the cathode side, and electrodialysis was performed. The ion selectivity coefficient was calculated in the same manner as in Example 5. As a result, P NH4 Na was 15.0, and P NH4 Ca was 31.2. In addition, the current efficiency at this time was 0.95.

[0081] (Measurement results of Example 7) As for the composite film obtained in Example 7, the film thickness of the KZnHCF film was 45 μm, the film thickness of the SPES film was 42.7 μm, and the film resistivity of the entire film in which both were combined was 348 Ωcm, and the film resistance was 3.06 Ωcm 2 . In Example 7, the composite film was disposed in such a manner that the SPES film faces the cathode side, and electrodialysis was performed. The ion selectivity coefficient was calculated in the same manner as in Example 5. As a result, P NH4 Na was 13.3, and P NH4 Ca was 25.8. In addition, the current efficiency at this time was 0.94.

[0082] (Measurement results of Example 8) As for the composite film obtained in Example 8, the film thickness of the KZnHCF film was 58 μm, the film thickness of the SPES film was 19 μm, and the film resistivity of the entire film in which both were combined was 197 Ωcm, and the film resistance was 1.52 Ωcm 2 . In Example 8, the composite film was disposed in such a manner that the SPES film faces the cathode side, and electrodialysis was performed. The ion selectivity coefficient was calculated in the same manner as in Example 5. As a result, P NH4 Na was 12.6, and P NH4 Ca ​was 0.97.

[0083] [Example 9] In Example 9, the composite film obtained in Example 5 was set in a manner that the SPES film faces the anode side, and electrodialysis was performed. The results are shown in Figure 14 Fig. 9. This figure shows the ion concentration of NH4 + , Na + and Ca 2+ ions on the concentrated side and the dilute side with time. By the applied direct current voltage, the three kinds of cations all migrate from the dilute side to the concentrated side, and from the slope of the time-concentration curve, the permeation flux was calculated using Equation (3), and the ion selectivity coefficient was calculated from Equations (4) and (5). As a result, P NH4 Na was 2.4, and P NH4 Ca was 3.3. This indicates that NH4 + selectively permeates 2.4 times as much as Na + , and that NH4 2+ selectively permeates 3.3 times as much as Ca + . In addition, the current efficiency at this time was 0.87.

[0084] [Comparative Example] As a comparative example, a standard cation exchange film CSE manufactured by Astom Co. was used, and electrodialysis was performed under the same conditions as the examples. The film thickness of this film was 160 μm, the film resistivity was 113 Ωcm, and the film resistance was 1.80 Ωcm 2 . Figure 15 The results of electrodialysis using this film are shown in Fig. 10. As a result, P NH4 Na was 1.81, and P NH4 Ca was 0.98. The current efficiency at this time was 0.97. This indicates that NH4 + selectively permeates 1.81 times as much as Na + . In this film, the value of P NH4 Ca becomes 1 or less, and thus Ca + selectively permeates 1.02 times as much as NH4 2+ .

[0085] In Examples 5 to 8, by providing another cation exchange layer not containing a metal cyano complex on one side of the cation exchange layer containing a metal cyano complex and a binder resin, it is possible to maintain NH4 + selectively permeates 2.4 times as much as Na 2+ and Ca +to improve the current efficiency while maintaining excellent permselectivity (permselectivity coefficient of more than 10).

[0086] Industrial applicability The cation exchange membrane of the present application has excellent permselectivity for ammonium ions, and thus can be used for various applications for concentrating ammonium ions, such as various water treatments of waste water and the like. In addition, the cation exchange membrane of the present application can be suitably used for electrodialysis devices, Donnan dialysis devices, and the like.

Claims

1. A cation exchange membrane having a cation exchange layer comprising a metal cyano complex and a binder resin.

2. The cation exchange membrane as described in claim 1, wherein, The mass ratio of metal cyano complex to binder resin is 0.2:1 to 5:

1.

3. The cation exchange membrane as described in claim 1 or 2, wherein the membrane resistance is 0.2~15 Ωcm. 2 .

4. The cation exchange membrane according to any one of claims 1 to 3, wherein, The adhesive resin is a resin that does not have ion exchange capacity and / or a resin with low ion exchange capacity.

5. The cation exchange membrane as described in claim 4, wherein, The ion exchange capacity of resins with low ion exchange capacity is 0.001~0.2 meq / g.

6. The cation exchange membrane according to any one of claims 1 to 5, wherein, One or both sides of the cation exchange layer containing a metal cyano complex and a binder resin have other cation exchange layers that do not contain the metal cyano complex.

7. Ion exchange membrane unit, wherein, The anion exchange membrane is configured opposite to the cation exchange membrane according to any one of claims 1 to 6.

8. An electrodialysis apparatus, which is an electrodialysis apparatus equipped with an anode, a cathode, a cation exchange membrane, and an anion exchange membrane, wherein, The cation exchange membrane is any one of claims 1 to 6.

9. A method for manufacturing a cation exchange membrane, wherein, Metal cyano complex particles, binder resin and solvent are mixed to disperse the metal cyano complex particles in the mixed solution, and the mixed solution is coated or cast and the solvent is removed.

10. A method for manufacturing a cation exchange membrane, wherein, On a cation exchange layer formed by mixing metal cyano complex particles, binder resin and solvent, dispersing the metal cyano complex particles in the mixed solution, coating or casting the mixed solution and removing the solvent, a liquid formed by mixing resin and solvent to form other cation exchange layers without metal cyano complexes is coated and the solvent is removed, or other cation exchange membranes without metal cyano complexes are bonded.

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