JPWO2018164143A1 - Electrodialysis and reverse electrodialysis - Google Patents

Abstract

In an electrodialysis apparatus in which an ion exchange membrane is disposed in a space between a cathode and an anode, and further, a desalination chamber and a concentration chamber are formed by the ion exchange membrane, the ion exchange membrane is one of a porous substrate. Is an asymmetric ion exchange membrane having an ion exchange resin layer formed on the surface thereof, wherein the asymmetric ion exchange membrane is provided such that the surface on which the ion exchange resin layer is formed is on the desalination chamber side. An electrodialysis device capable of performing electrodialysis stably with a high desalination capacity, and a reverse electrodialysis device capable of performing a reverse electrodialysis stably with a high output by using the electrodialysis device characterized by the above. provide.

Description

  The present invention relates to an electrodialysis device and a reverse electrodialysis device, and more particularly, to an electrodialysis device and a reverse electrodialysis device using an asymmetric ion exchange membrane.

  Ion exchange membranes such as anion exchange membranes and cation exchange membranes are used for electrodialysis and reverse electrodialysis. In electrodialysis, an anion exchange membrane and a cation exchange membrane are alternately arranged to form a desalination chamber and a concentration chamber. When, for example, seawater is supplied to each chamber to supply an electric current, demineralized water and concentrated saline can be produced. Electrodialysis includes salt production from seawater, desalination in the food sector such as soy sauce and oligosaccharides, desalination and concentration of leachate from final disposal sites, desalination and concentration of process wastewater, recovery of aluminum sash acid washing acid wastewater, alkali This technology is used for collecting waste liquid.

  In reverse electrodialysis, similarly to electrodialysis, an anion exchange membrane and a cation exchange membrane are alternately arranged, and a lean chamber and a rich chamber are formed. This is a technique in which the energy of the concentration difference is converted into electric power by an ion exchange membrane by supplying an electrolyte solution. Reverse electrodialysis can be used, for example, for power generation using freshwater collected from a river and seawater collected from the sea. It is also possible to use seawater and concentrated seawater having a higher concentration than seawater discharged from a seawater desalination facility by distillation or reverse osmosis.

  Various improvements have been attempted to increase the efficiency of electrodialysis and reverse electrodialysis. For example, Patent Literature 1 discloses an asymmetric ion exchange membrane in which a predetermined nonwoven fabric sheet is used and an ion exchange resin layer is provided on one surface of the nonwoven fabric sheet. The asymmetric ion exchange membrane of Patent Document 1 is excellent in strength, dimensional and shape stability, and the like. Furthermore, since the ion exchange resin is firmly fixed to the nonwoven fabric sheet and the thickness of the ion exchange resin layer on the surface of the nonwoven fabric sheet is thin and uniform, there is no variation in membrane characteristics, and reduction in membrane resistance is realized. .

JP 2012-40508 A

  As described above, the asymmetric ion exchange membrane disclosed in Patent Document 1 is very useful in itself. However, when mass-producing an electrodialysis apparatus using such an ion exchange membrane, some of the treatment efficiency (desalting capacity) is required. However, there is a problem that a device lower than the design value is generated.

Therefore, an object of the present invention is to provide an electrodialysis apparatus and a reverse electrodialysis apparatus capable of performing electrodialysis or reverse electrodialysis stably with high efficiency.
The present inventors have conducted intensive studies on the characteristics of the asymmetric ion exchange membrane.As a result, when the asymmetric ion exchange membrane is sandwiched between electrolyte solutions having different electrical conductivities, depending on the orientation in the thickness direction of the membrane, That is, the inventors discovered that there is a difference in electric resistance depending on whether the surface on which the ion exchange resin layer is formed is in contact with an electrolyte solution having a high electric conductivity or an electrolyte solution having a low electric conductivity. This has led to the present invention.

  According to the present invention, an ion exchange membrane is disposed in a space between a cathode and an anode, and further, in an electrodialysis apparatus in which a desalting chamber and a concentration chamber are formed by the ion exchange membrane, the ion exchange membrane is An asymmetric ion exchange membrane in which an ion exchange resin layer is formed on one surface of a porous substrate, wherein the surface on which the ion exchange resin layer is formed is on the desalting chamber side. An electrodialysis device characterized by being installed as described above.

In the electrodialysis device of the present invention,
(1) the porous substrate is a nonwoven fabric;
(2) Cation exchange membranes and anion exchange membranes are alternately arranged in the space between the cathode plate and the anode plate, and the cation exchange membrane on the anode plate side and the cation exchange membrane on the cathode plate side A desalination chamber is formed between the cation exchange membrane on the anode plate side and the anion exchange membrane on the cathode plate side, and a concentration chamber is formed,
(3) All ion exchange membranes forming the desalting chamber and the concentrating chamber are asymmetrical ion exchange membranes and are installed such that the surface on which the ion exchange resin layer is formed is on the desalting chamber side. is being done,
Is preferred.

  According to the present invention, the electrodialysis apparatus is used to supply an electrolyte solution to a desalination chamber, and to supply the concentrated solution with an electrolyte solution having a higher concentration than the electrolyte solution supplied to the desalination chamber. A dialysis method is also provided. In the electrodialysis method of the present invention, it is preferable that the electrolyte solution supplied to the desalting chamber has an electric conductivity (25 ° C.) of 0.05 to 100 mS / cm.

  Further, according to the present invention, in the reverse electrodialysis apparatus wherein an ion exchange membrane is disposed in a space between the negative electrode and the positive electrode, and further, a lean chamber and a rich chamber are formed by the ion exchange membrane, Is an asymmetric ion-exchange membrane having an ion-exchange resin layer formed on one surface of a porous substrate, and the asymmetric ion-exchange membrane has a surface on which the ion-exchange resin layer is formed and a lean chamber side. A reverse electrodialysis device is provided, wherein

In the reverse electrodialysis device of the present invention,
(1) the porous substrate is a nonwoven fabric;
(2) Cation exchange membranes and anion exchange membranes are alternately arranged in the space between the negative electrode plate and the positive electrode plate, and between the anion exchange membrane on the positive electrode plate side and the cation exchange membrane on the negative electrode plate side. A lean chamber is formed, and a rich chamber is formed between the cation exchange membrane on the positive electrode plate side and the anion exchange membrane on the negative electrode plate side,
(3) All the ion exchange membranes forming the lean chamber and the rich chamber are asymmetric ion exchange membranes, and are installed such that the surface on which the ion exchange resin layer is formed is on the lean chamber side. That
Is preferred.

  According to the present invention, the reverse electrodialysis apparatus is used to supply an electrolyte solution to a lean chamber, and to supply the rich chamber with an electrolyte solution having a higher concentration than the electrolyte solution supplied to the lean chamber. A dialysis method is provided. In the reverse electrodialysis method of the present invention, it is preferable that the electrolyte solution supplied to the lean chamber has an electric conductivity (25 ° C.) of 0.005 to 1 mS / cm.

  In the electrodialysis apparatus of the present invention, the asymmetric ion exchange membrane is installed so that the ion exchange resin layer side faces the desalting chamber. Thereby, the electrodialysis apparatus of the present invention can exhibit the processing efficiency (desalting capacity) when a constant current is applied to the maximum and stably.

  Similarly, in the reverse electrodialysis apparatus of the present invention, the asymmetric ion exchange membrane is installed so that the ion exchange resin layer side faces the lean chamber. Thus, when the reverse electrodialysis device of the present invention is used for power generation, the maximum power generation efficiency (maximum output) can be stably exhibited.

  As described above, the electrodialysis apparatus and the reverse electrodialysis apparatus of the present invention may be abbreviated as (reverse) electrodialysis apparatus hereinafter. Although the reason why the efficiency of｝ is extremely high and the variation among the devices is effectively suppressed is not clear, the present inventors presume as follows. That is, until now, the direction of the asymmetric ion exchange membrane has not been considered, and in the case of electrodialysis, the surface of the asymmetric ion exchange membrane on the side of the ion exchange resin layer faces the desalting chamber, or the surface of the porous substrate side faces It turned out to be suitable for the desalination room. When the surface on the porous substrate side faces the desalting chamber, a low-concentration electrolyte solution enters the gaps between the porous substrates. Since the porous substrate itself does not have ion conductivity, the region into which the low-concentration electrolyte solution has penetrated becomes a high-resistance region. Thus, when electrodialysis is performed with a low-concentration electrolyte solution in a porous substrate, compared to the case where a homogeneous (symmetric) ion exchange membrane is used or the case where the porous substrate layer faces the concentration chamber, Thus, the electric resistance of the electrodialysis device increases. Moreover, in an electrodialysis apparatus, usually, a plurality of ion exchange membranes are used to provide a plurality of desalination chambers / concentration chambers. Therefore, the asymmetric ion exchange apparatus arranged with the porous substrate side facing the desalination chamber is used. The greater the number of films, the greater the electrical resistance and the lower the processing efficiency of the entire device. In addition, when the number of asymmetric ion exchange membranes whose porous substrate side faces the desalting chamber varies, the processing efficiency of each apparatus also varies, and performance varies.

  However, in the electrodialysis apparatus of the present invention, since the asymmetric ion exchange membrane is installed such that the ion exchange resin layer side is the desalting chamber side and the porous substrate side is the concentration chamber side, the high electric resistance of the ion exchange membrane is high. Is avoided, and variations in the processing efficiency of each device are suppressed.

  The relationship between the direction and the efficiency of such an asymmetric ion exchange membrane is considered to be the same in the case of a reverse electrodialysis device. That is, in a reverse electrodialysis device, usually, a plurality of ion exchange membranes are used to form a plurality of diluted chambers. When the dense chamber is provided, the power generation efficiency of the entire apparatus becomes lower as the number of asymmetric ion exchange membranes arranged with the porous substrate side facing the lean chamber increases. Further, if the number of asymmetric ion exchange membranes whose porous substrates face the lean chamber is different, the power generation efficiency of each device will also be different. However, in the reverse electrodialysis apparatus of the present invention, since the asymmetric ion exchange membrane is installed so that the ion exchange resin layer side is the lean chamber side and the porous substrate side is the rich chamber side, the high electrical resistance of the ion exchange membrane is high. Is avoided, and variations in power generation efficiency for each device are also suppressed. In addition, such an effect becomes more remarkable in a reverse electrodialysis apparatus. This is because, in order to increase the power generation output, the electrolyte concentration in the lean chamber of the reverse electrodialysis device is generally lower than the electrolyte concentration in the desalination room of the electrodialysis device.

It is a schematic diagram for explaining the principle of electrodialysis. FIG. 2 is a schematic exploded view for explaining the structure of the electrodialysis device of the present invention. It is the schematic for demonstrating the principle of reverse electrodialysis.

  The present invention relates to an electrodialysis device and a reverse electrodialysis device. The (reverse) electrodialysis device of the present invention uses an asymmetric ion exchange membrane.

<Asymmetric ion exchange membrane>
An asymmetric ion exchange membrane has a structure in which one surface of a porous substrate is impregnated with an ion exchange resin to form an ion exchange resin layer on one surface of the porous substrate, an anion exchange membrane or It is a cation exchange membrane. The other surface of the asymmetric ion exchange membrane is in a state where the porous substrate is exposed. In the (reverse) electrodialysis apparatus of the present invention, a known asymmetric ion exchange membrane can be used without any limitation.

As the porous substrate, known porous films, nets, knits, woven fabrics, nonwoven fabrics, and the like can be used. Specifically, porous films, nets, knits, woven fabrics, and nonwoven fabrics made of resins such as polyethylene, polypropylene, polyvinyl chloride, polyvinyl alcohol, polyvinylidene chloride, and styrene-divinylbenzene copolymer can be used. .
From the viewpoint of maximizing the effects of the present invention, a nonwoven fabric is preferred. In the nonwoven fabric, since the fibers are tightly entangled, the ion exchange resin layer can be firmly adhered, and the nonwoven fabric is inexpensive. Further, since the nonwoven fabric has a high porosity, the amount of the low-concentration electrolyte solution penetrating into the nonwoven fabric increases, and the effect of increasing the electric resistance of the nonwoven fabric due to the difference in the disposition direction of the asymmetric ion exchange membrane appears.

The porosity of the porous substrate can be measured by a permeability measured by a permeability test according to JIS L1913, and is preferably in a range of 1.0 to 1000 cm ³ / cm ² · sec, and particularly preferably 5.0 to 1000 cm ³ / cm ² · sec. It is preferably in the range of 500 cm ³ / cm ² · sec. If the air permeability is too large, the strength of the obtained ion exchange membrane decreases, and if it is too small, the resistance of the ion exchange membrane increases.

  As the nonwoven fabric, a nonwoven fabric formed of fibers having a fiber diameter of 1 to 30 μm, particularly 3 to 20 μm is preferable. If the fiber diameter is too large, the smoothness of the surface of the nonwoven fabric is impaired, and the anchor effect cannot be sufficiently exhibited, and the ion exchange resin layer may not be held firmly. If the fiber diameter is too small, the strength of the nonwoven fabric may decrease.

The basis weight of the nonwoven fabric, from the viewpoint of impregnating an appropriate amount of ion exchange resin to the nonwoven fabric, preferably ^{1~100g / m 2, 5~50g / m} 2 is particularly preferred. The thickness of the nonwoven fabric is preferably from 5 to 200 μm, particularly preferably from 10 to 100 μm.

  The nonwoven fabric may have a single-layer structure or a laminated structure.

  The ion exchange resin layer formed on the porous substrate described above is formed of an ion exchange resin that can be dissolved in an organic solvent and formed by coating. For example, a polymer obtained by polymerizing a monomer having an ethylenically unsaturated double bond such as vinyl, styrene, or acrylic, or polysulfone, polyphenylene sulfide, polyether ketone, polyether ether ketone, or polyether Polymers containing an aromatic ring in the main chain, such as imide, polyphenylene oxide, polyether sulfone, and polybenzimidazole, as well as polystyrene-poly (ethylene-butylene) -polystyrene triblock copolymer, polystyrene-poly (ethylene-propylene) ) -Ion-exchange groups that allow a hydrocarbon-based resin such as a styrene-based elastomer such as a polystyrene triblock copolymer or a polystyrene-polyisoprene block copolymer or a hydrogenated product thereof to exhibit an ion-exchange ability. , Katio Exchange groups or anion exchange groups are those having the introduced structures.

  An ion exchange group is a functional group that can be negatively or positively charged in an aqueous solution.In the case of a cation exchange group, examples thereof include a sulfonic acid group, a carboxylic acid group, and a phosphonic acid group. The sulfonic acid group which is a group is preferred. In the case of an anion exchange group, a primary to tertiary amino group, a quaternary ammonium group, a pyridyl group, an imidazole group, a quaternary pyridinium group and the like are mentioned. And quaternary pyridinium groups are preferred.

  Specific examples of the cation exchange resin include sulfonic acid-based monomers such as α-halogenated vinyl sulfonic acid, styrene sulfonic acid, and vinyl sulfonic acid, and carboxylic acid-based monomers such as methacrylic acid, acrylic acid, and maleic anhydride. Examples include polymers obtained by polymerizing monomers, phosphonic acid monomers such as vinyl phosphoric acid, and salts or esters thereof. Further, there may be mentioned the above-mentioned polymers having an aromatic ring in the main chain and polymers in which a cation exchange group such as a sulfonic acid group is introduced into a styrene-based elastomer. From the viewpoint that the amount of the cation exchange group is easily controlled and the moldability from an organic solvent is excellent, a polymer having a cation exchange group introduced into a polymer containing an aromatic ring in the main chain is more preferable.

  Examples of specific anion exchange resins include amine monomers such as vinylbenzyltrimethylamine and vinylbenzyltriethylamine, nitrogen-containing heterocyclic monomers such as vinylpyridine and vinylimidazole, and salts or esters thereof. Examples of the polymer include a polymer obtained by polymerization. These can be used after amination or methylation before and after polymerization of the monomer. Further, a halogenoalkyl group such as a chloromethyl group or a bromobutyl group is introduced into a polymer or a styrene-based elastomer containing an aromatic ring in the main chain, and then the quaternary amination of the halogenoalkyl group to form an anion exchange group. The introduced polymer may be mentioned. From the viewpoint that the amount of anion exchange group is easily controlled and the moldability from an organic solvent is excellent, a polymer containing an aromatic ring in the main chain or a polymer in which an anion exchange group is introduced into a styrene-based elastomer is more preferable.

These ion exchange resins may have a crosslinked structure as long as a solution dissolved in an organic solvent can be prepared, and examples thereof include divinylbenzene, divinylsulfone, butadiene, chloroprene, divinylbiphenyl, and trivinylbenzene. And may be crosslinked with a polyfunctional monomer represented by a divinyl compound such as divinylnaphthalene, diallylamine and divinylpyridine.
It may be a copolymer obtained by copolymerizing other monomers, for example, styrene, acrylonitrile, methylstyrene, acrolein, methylvinylketone, vinylbiphenyl and the like.

  Alternatively, a crosslinked structure can be introduced by forming these ion-exchange resin layers on a porous base material, and thereafter, for example, by thermally crosslinking sulfonic acid groups.

  The ion exchange resin as described above has an ion exchange capacity of 0.5 to 3.0 meq / g, particularly preferably 0.1 to 3.0 meq / g, from the viewpoint of reducing membrane resistance, preventing dissolution in an electrolyte solution, and suppressing swelling. It is preferably in the range of 8 to 2.0 meq / g. Therefore, it is preferable that a cation exchange group or an anion exchange group is introduced so as to have such an ion exchange capacity.

<Production of asymmetric ion exchange membrane>
The asymmetric ion-exchange membrane is manufactured by forming an ion-exchange resin layer on the surface of the porous substrate by the coating method.

  For forming the ion exchange resin layer by the coating method, the above-mentioned organic solvent solution of the ion exchange resin is used. Alternatively, an organic solvent solution of the ion exchange resin precursor can be used. The ion exchange resin precursor is a polymer having a functional group capable of introducing an ion exchange group.

  Examples of the polymer having a functional group for introducing a cation exchange group include those obtained by polymerizing monomers such as styrene, vinyl toluene, vinyl xylene, α-methyl styrene, vinyl naphthalene, and α-halogenated styrenes. Can be mentioned. Styrene such as polystyrene-poly (ethylene-butylene) -polystyrene triblock copolymer, polystyrene-poly (ethylene-propylene) -polystyrene triblock copolymer, polystyrene-polyisoprene block copolymer and hydrogenated products thereof. A system elastomer is also mentioned as a polymer having a functional group capable of introducing a cation exchange group.

  Examples of the polymer having a functional group for introducing an anion exchange group include those obtained by polymerizing monomers such as styrene, vinyltoluene, chloromethylstyrene, vinylpyridine, vinylimidazole, α-methylstyrene, and vinylnaphthalene. Can be mentioned. Further, polymers containing an aromatic ring in the main chain thereof such as polysulfone, polyphenylene sulfide, polyether ketone, polyether ether ketone, polyether imide, polyphenylene oxide, polyether sulfone, and polybenzimidazole, and further, polystyrene-poly ( Styrene-based elastomers such as ethylene-butylene) -polystyrene triblock copolymer, polystyrene-poly (ethylene-propylene) -polystyrene triblock copolymer, polystyrene-polyisoprene block copolymer and hydrogenated products thereof are also anion-exchange groups. As a polymer having a functional group capable of introducing a polymer.

  Of course, as long as these ion exchange resin precursors can be dissolved in an organic solvent, a crosslinked structure may be introduced by copolymerizing a polyfunctional monomer such as the above-mentioned divinyl compound. If necessary, another monomer may be copolymerized.

  When an organic solvent solution of such an ion exchange resin precursor is used, an ion exchange group introducing agent is usually contained in such a solution, and the ion exchange group is introduced in parallel with the formation of the resin layer. You. Examples of the ion-exchange group-introducing agent include polyalkylbenzenesulfonic acid (for example, 1,3,5-trimethylbenzene-2-sulfonic acid, 1,2,4,5-tetramethylbenzene-3-sulfonic acid, 2,3,4,5-pentamethylbenzene-6-sulfonic acid, etc.), N, N, N ', N'-tetramethyl-1,6-hexanediamine, N, N, N', N'-tetra Methyl-1,6-octanediamine, N, N, N ′, N′-tetraethyl-1,6-hexanediamine and the like. Alternatively, an ion exchange group may be introduced by preparing a resin layer of the ion exchange resin precursor and then treating the resin layer with the above ion exchange group introduction agent.

  The organic solvent used for preparing the organic solvent solution of the ion exchange resin or the ion exchange resin precursor is not particularly limited as long as it can dissolve the above-mentioned polymer. From the viewpoint of easy removal by drying, ethylene chloride, chloroform, tetrahydrofuran, dimethylformamide, N-methylpyrrolidone, methyl alcohol, butyl acetate, ethyl acetate, toluene, methyl ethyl ketone, etc. were used alone or in combination of two or more. It is preferably used in a mixed state.

  The amount of the organic solvent used should be in a range suitable for application by means described below. For example, the viscosity (25 ° C.) of the organic solvent solution is 0.5 to 80 dPa · s, particularly 1.0 to 60 dPa · s. It is preferable to use the organic solvent in an amount that falls within the range of If the viscosity is too high, the permeation is slow when applied or superimposed on the porous substrate, and it takes time to obtain sufficient adhesiveness. If the viscosity is too low, the resin solution tends to excessively penetrate into the nonwoven fabric, and the ion exchange resin layer on the surface cannot be formed.

The formation of the ion-exchange resin layer on the porous substrate can also be formed by directly applying the organic solvent solution of the ion-exchange resin or the ion-exchange resin precursor prepared as described above on the porous substrate. The following method is preferable in that an asymmetric structure can be stably obtained.
First, a release film is prepared, and the organic solvent solution for film formation prepared above is applied on the release film to form a coating layer of the organic solvent solution. Next, this coating layer is transferred to the surface on one side of the porous substrate to form an ion exchange resin layer.

  The release film is such that it does not adhere to the finally formed ion exchange resin layer, does not dissolve in the organic solvent in the coating layer, and can be easily peeled off at last. The thickness is not limited, but generally, a polyester film such as polyethylene terephthalate is preferably used.

  The application of the organic solvent solution onto the release film can be performed by a known means, for example, by doctor blade coating, knife coating, roll coating, bar coating, or the like.

  After the coating layer is formed and before it is completely dried, the porous substrate is superimposed on the surface of the coating layer and held. The superposition may be appropriately performed under pressure in order to promote the penetration of the organic solvent solution into the porous substrate. Pressing can be performed by a roller press or the like, and the pressing pressure is generally set to a range that does not excessively compress the coating layer.

  After the porous substrates are overlapped as described above and the coating layer is made to permeate the porous substrate, the coating layer is dried to remove the organic solvent and solidify the coating layer. When an organic solvent solution of an ion exchange resin is used, an ion exchange resin layer is thereby formed. Drying can be performed by heat drying at a temperature at which the porous substrate or the like does not melt and form a film, reduced pressure drying, blast drying, or the like.

When an organic solvent solution of an ion exchange resin precursor containing an ion exchange group introducing agent is used, the introduction of ion exchange groups is completed by the above-mentioned heating and drying. When the coating layer is formed using an organic solvent solution of an ion-exchange resin precursor containing no ion-exchange group-introducing agent, the layer obtained by drying is a layer of the ion-exchange resin precursor. It is necessary to carry out a process for introducing an exchange group.
The ion exchange group is introduced by a method known per se. For example, in the case of producing a cation exchange membrane, it is performed by a treatment such as sulfonation, phosphonium conversion, or hydrolysis. When an anion exchange membrane is produced, it is carried out by a treatment such as amination or alkylation. That is, the solution of the treating agent for performing the above treatment is brought into contact with the coating layer of the ion-exchange resin precursor obtained by drying to carry out an exchange group introduction reaction, and then, by performing washing and drying, ion exchange is performed. A resin layer can be formed.

Further, after forming an ion-exchange resin layer or an ion-exchange resin precursor layer on a porous substrate by the above-described method, a crosslinked structure can be introduced if necessary. The crosslinked structure can be introduced by a method known per se. For example, in the case of a cation exchange membrane, it can be introduced by thermal crosslinking between sulfonic acid groups. In the case of an anion exchange membrane, a method in which a diamine compound such as N, N, N ', N'-tetramethyl-1,6-hexanediamine is allowed to act on an ion exchange resin precursor layer containing a chloromethyl group is exemplified. You.
The introduction of the crosslinked structure can also be performed after the release film below is released.

  After forming the ion-exchange resin layer as described above, the release film is peeled off, whereby a target asymmetric ion-exchange membrane can be obtained.

Although the asymmetric ion exchange membrane obtained as described above varies depending on the properties of the porous substrate and the ion exchange resin used, the ion exchange capacity is usually 0.1 to 2.0 meq / g-dry membrane. , Preferably 0.2 to 1.5 meq / g-dry film.
The transport number is usually 0.9 to 0.99, preferably 0.93 to 0.98, and the membrane resistance is usually 0.1 to 3.0 Ω · cm ² , preferably 0.1 to 3.0 Ω · cm ² . ² to 2.0 Ω · cm ² , and the burst strength is usually 50 to 1000 kPa, preferably 100 to 800 kPa.

  The ion exchange resin penetrates into the inside (void) of a porous substrate such as a nonwoven fabric. Although it is difficult to strictly define the thickness, it is preferable from the viewpoint of the adhesion between the ion-exchange resin layer and the porous base material that the thickness is in the range of 1 to 10 μm, particularly 2 to 5 μm. . The thickness of the ion exchange resin layer (the thickness of the resin layer existing above the surface of the porous substrate) is in the range of 1 to 50 μm, particularly 2 to 10 μm from the viewpoint of the balance between ion selectivity and resistance. Preferably, there is.

<Electrodialysis>
An electrodialysis apparatus according to the present invention using the above-described asymmetric ion exchange membrane will be described. The principle of electrodialysis will be described with reference to FIG. In the electrodialysis apparatus 1 of the present invention, the cation exchange membrane C and the anion exchange membrane A are alternately arranged in the space between the cathode 10 and the anode 11, and an ion exchange chamber is provided between these ion exchange membranes. Are formed. The ion exchange chamber includes a desalination chamber 13 and a concentration chamber 15. The desalting chamber 13 includes a cation exchange membrane C and an anion exchange membrane A located on the anode 11 side with respect to the cation exchange membrane C. The concentration chamber 15 includes an anion exchange membrane A and a cation exchange membrane C located on the anode 11 side with respect to the anion exchange membrane A. Therefore, it has a structure in which a plurality of desalination chambers 13 and concentration chambers 15 are alternately arranged.

  In this specification, the ion exchange chamber and the electrode chamber are present between the endmost ion exchange chamber (desalting chamber 13 and concentration chamber 15) and the electrodes (cathode 10 and anode 11). The ion exchange membrane is called an electrode diaphragm 17.

In the electrodialysis apparatus having such a structure, for example, a voltage is applied between the anode 11 and the cathode 10 to circulate and supply the treatment solution 19 containing a salt such as NaCl to the desalting chamber 13 and to the concentration chamber 15. When the electrolyte solution 21 is supplied while being circulated and energized, the cations (Na ^{+ in} FIG. 1) in the processing solution 19 pass through the cation exchange membrane C to the concentration chamber 15 adjacent to the cathode 10 side. Transition. On the other hand, anions (Cl ^{− in} FIG. 1) in the processing solution pass through the anion exchange membrane A and move to the concentration chamber 15 adjacent to the anode 11 side. In this manner, desalting is performed from the processing solution circulated and supplied to the desalting chamber 13, and a low-concentration electrolyte solution is recovered as a desalted product, while being circulated to the concentration chamber 15. The salt concentration in the supplied electrolyte solution gradually increases, and finally, the high-concentration electrolyte solution is recovered as a concentrated product.

  The electrodialysis apparatus of the present invention for performing electrodialysis as described above may have a known structure, and as shown in FIG. 2, a large number of gasket spacers 30 are arranged in an overlapping manner. A cation exchange membrane C and an anion exchange membrane A are alternately sandwiched between the gasket spacers 30 so as to have a structure shown in FIG. In FIG. 2, the gasket spacer net is omitted. In the electrodialysis apparatus having such an arrangement, the space in each gasket spacer 30 (the space surrounded by the gasket frame 31) is the above-described ion exchange chamber (desalting chamber 13 or concentrating chamber 15).

  The gasket frame 31 of each gasket spacer has communication holes 33, 33 for flowing a treatment liquid supplied to the desalting chamber 13 and a desalted product (low-concentration electrolyte solution) discharged from the desalting chamber 13, Communication holes 35, 35 for flowing the electrolyte solution supplied to the concentration chamber 15 and the concentrated product (high-concentration electrolyte solution) discharged from the concentration chamber 15 are formed.

  Further, the gasket frame 31 of the gasket spacer having the space serving as the desalting chamber 13 is provided with a flow distribution part 37 connecting the communication hole 33 and the space serving as the desalting chamber 13. Similarly, in the gasket frame 31 of the gasket spacer having the space to be the concentrating chamber 15, a flow distribution portion 39 that connects the communication hole 35 and the space to be the concentrating chamber 15 is formed. That is, the liquid is supplied from these communication holes 33, 35 to the desalting chamber 13 or the concentration chamber 15 via the distribution parts 37, 39, and further, the liquid supplied to the desalination chamber 13 or the concentration chamber 15 is supplied to the distribution part. It is configured to be discharged to the communication hole 33 or 35 via 37 or 39.

  In the electrodialysis apparatus having the above-described structure, an ion exchange membrane is sandwiched between the gasket spacers 30, and the gasket spacers 30 effectively prevent contact between adjacent ion exchange membranes. In addition, openings 33 'and 35' are formed in the ion exchange membrane sandwiched between the gasket spacers 30 so as to allow the liquid to flow through the communication holes 33 and 35, respectively. reference). That is, by supplying electricity while circulating the treatment liquid and the electrolyte solution through the communication holes 33 and 35, desalting is performed in the desalting chamber 13 and the salt concentration of the liquid flowing in the concentrating chamber 15 gradually increases. It will go.

  As described above, as a result of intensive studies by the present inventors, in electrodialysis, the installation direction of the cation exchange membrane C and the anion exchange membrane A, which are asymmetric ion exchange membranes, greatly affects the processing efficiency. New knowledge was obtained. Therefore, in the present invention, as shown in FIG. 1, the asymmetric ion exchange membrane to be used is installed such that the surface on which the ion exchange resin layer 40 is formed is located on the desalination chamber 13 side. , The processing efficiency is fully exhibited.

  In the electrodialysis apparatus of the present invention, it is preferable to use at least four or more ion exchange membranes including the electrode diaphragm, and it is particularly preferable to use ten or more ion exchange membranes for the following reasons. In a large-scale electrodialysis apparatus using a large number of ion exchange membranes, the processing capacity can be increased, and further, the fluctuation of the processing efficiency due to the orientation of the asymmetric ion exchange membrane is remarkable.

  As the ion exchange membrane, only an asymmetric ion exchange membrane may be used, or an asymmetric ion exchange membrane and a symmetric ion exchange membrane may be used together. A known symmetric ion exchange membrane may be used. It is preferable that 50% or more of the ion exchange membranes forming the desalting chamber 13 and the concentration chamber 15 are asymmetric ion exchange membranes, and it is particularly preferable that all of them are asymmetric ion exchange membranes for the following reasons. The electrodialysis device can maximize the processing efficiency, and when the devices are mass-produced, the variation in the processing efficiency of each device can be effectively suppressed.

  The electrodialysis apparatus of the present invention having such a structure supplies and uses an electrolyte solution containing a halide such as sodium or lithium. The solvent of the electrolyte solution is generally water, and may contain an organic solvent. The electrolyte solution also includes a processing solution to be desalted. For example, when the electrodialysis apparatus of the present invention is used for salt production, seawater may be supplied to the desalting chamber and the concentrating chamber. Further, in the case of utilizing for desalting in the food field such as oligosaccharides and soy sauce, a treatment solution may be supplied to a desalting chamber and an electrolyte solution different from the treatment solution may be supplied to a concentration chamber.

  From the viewpoint that the effects of the present invention are maximized, it is preferable to supply the electrolyte solution to the desalting chamber, and to supply the concentrated solution with a higher concentration of the electrolyte solution than the electrolyte solution supplied to the desalting chamber. . The electrolyte solution supplied to the desalting chamber preferably has an electric conductivity (25 ° C.) of 0.05 to 100 mS / cm, and has an electric conductivity (25 ° C.) of 0.1 to 50 mS / cm. And more preferably those having an electric conductivity (25 ° C.) of 0.2 to 10 mS / cm. When the concentration of the electrolyte solution supplied to the desalting chamber is low, the effect of the present invention is remarkably exhibited. On the other hand, when the electrolyte solution in the desalting chamber is too thin, the solution resistance becomes extremely high, and it becomes difficult to conduct electricity. That's why. Usually, these desalting chamber electrolyte solutions are desalted to 0.1 to 10.0 mS / cm by electrodialysis. As the high-concentration electrolyte solution to be supplied to the concentration chamber, one having an electric conductivity of 1 to 1000 mS / cm (25 ° C) is preferable, and one having an electric conductivity of 2 to 500 mS / cm (25 ° C) is particularly preferable. preferable. The electric conductivity is measured by a method based on JIS K 0130: 2008.

  The concentration of the electrolyte solution is appropriately determined so that the electric conductivity falls within the above range.

<Reverse electrodialysis>
The reverse electrodialysis apparatus of the present invention using the above-described asymmetric ion exchange membrane will be described with reference to FIG. In the reverse electrodialysis apparatus 50 of the present invention, as in the case of the electrodialysis apparatus, the cation exchange membrane C and the anion exchange membrane A are alternately arranged between the negative electrode 51 and the positive electrode 53. Thereby, in the reverse electrodialysis apparatus 50 of the present invention, the lean chamber 55 and the rich chamber 57 are formed. Specifically, the lean chamber 55 includes a cation exchange membrane C and an anion exchange membrane A located on the positive electrode side of the cation exchange membrane C. The rich chamber 57 includes an anion exchange membrane A and a cation exchange membrane C located on the positive electrode side with respect to the anion exchange membrane A. As a result, the plurality of lean chambers 55 and the rich chambers 57 are arranged alternately.

In the reverse electrodialysis apparatus of the present invention having such a structure, a low-concentration electrolyte solution 59 (for example, river water or sewage treatment water) is supplied to the lean chamber 55, and a high-concentration electrolyte solution 61 (for example, to the thick chamber 57). When seawater is supplied and the negative electrode 51 and the positive electrode 53 are connected via the electric device 63, a membrane potential is generated between the lean chamber 55 and the rich chamber 57, and a current flows using the membrane potential as a driving force to generate power. be able to. At this time, the cations (Na ^{+ in} FIG. 3) in the rich chamber 57 provided between the negative electrode 51 and the positive electrode 53 move to the lean chamber 55 through the cation exchange membrane C, and the anions (Cl in FIG. 3). ^- ) Moves to the other adjacent lean chamber 55 after passing through the anion exchange membrane A.

  The reverse electrodialysis apparatus of the present invention can have a known structure as long as such a principle is followed. For example, a device having the same structure as the filter press type electrodialysis device shown in FIG. 2 can be used as a reverse electrodialysis device. That is, a chamber corresponding to the desalination chamber is a lean chamber, a chamber corresponding to the enrichment chamber is a rich chamber, and a positive electrode (anode in FIG. 2) and a negative electrode (a cathode in FIG. 2) are connected to electric equipment and the like to each chamber. Electricity can be generated by passing the liquid.

  In the reverse electrodialysis apparatus of the present invention, similarly to the electrodialysis apparatus, it is important that the asymmetric ion exchange membrane to be used is installed such that the surface on which the ion exchange resin layer is formed is on the lean chamber side. .

  In the reverse electrodialysis apparatus of the present invention, it is preferable to use at least four or more ion exchange membranes including the electrode diaphragm, and it is particularly preferable to use ten or more ion exchange membranes for the following reasons. In a large reverse electrodialysis apparatus using a large number of ion exchange membranes, a larger output can be obtained, and furthermore, fluctuations in power generation efficiency due to the orientation of the asymmetric ion exchange membranes are remarkable.

  As the ion exchange membrane, only an asymmetric ion exchange membrane may be used, or an asymmetric ion exchange membrane and a symmetric ion exchange membrane may be used together. A known symmetric ion exchange membrane may be used. It is preferable that 50% or more of the ion exchange membranes forming the lean chamber and the rich chamber are asymmetric ion exchange membranes, and it is particularly preferable that all of them are asymmetric ion exchange membranes for the following reasons. It is possible to realize the maximum power generation efficiency, and it is possible to effectively suppress variations in the power generation efficiency of each device when the devices are mass-produced.

The reverse electrodialysis apparatus of the present invention having such a structure may be supplied with a desired electrolyte solution to generate power. For example, an electrolyte solution such as river water or sewage treatment water may be supplied to the lean chamber 55. The concentrated chamber 57 may be supplied with an electrolytic solution, such as seawater or concentrated seawater, having a higher concentration than the electrolytic solution supplied to the diluted chamber. Preferably, an electrolyte solution having an electric conductivity of 0.005 to 1 mS / cm, particularly 0.01 to 0.8 mS / cm is supplied to the diluted chamber 55. Preferably, an electrolyte solution having an electric conductivity of 0.05 to 200 mS / cm, particularly 0.1 to 150 mS / cm is supplied to the rich chamber 57. Since the voltage of the reverse electrodialysis increases in proportion to the concentration ratio between the lean chamber and the rich chamber, a smaller concentration in the lean chamber is advantageous for increasing the output. On the other hand, it is common that the rich chamber is supplied with seawater, which is abundant and inexpensive, and about 2 to 3 times the concentrated seawater. Due to the limitation of the concentration of the rich chamber, the concentration of the lean chamber in reverse electrodialysis is generally set lower than the concentration of the dilution chamber in electrodialysis.
A low-concentration electrolyte solution tends to cause an increase in the resistance of the porous substrate when impregnated and retained in a porous substrate such as a nonwoven fabric, so the effect of the present invention is remarkable in reverse electrodialysis using a low-concentration electrolyte solution. Be demonstrated.

  The concentration of the electrolyte solution is appropriately determined so that the electric conductivity falls within the above range.

  The (reverse) electrodialysis apparatus of the present invention may be appropriately changed in design as long as the essence of the invention is not changed. For example, a symmetric ion exchange membrane is used as an electrode diaphragm that separates the electrode from the ion exchange chamber at the extreme end, from the viewpoint of strength and melting point, and from the viewpoint of considering the effect of the substance generated at the electrode on the membrane. Is also good. As the electrode diaphragm, one or more asymmetric or symmetric ion exchange membranes may be used.

  Hereinafter, embodiments of the present invention will be specifically described with reference to examples, but the present invention is not limited to the following examples as long as the gist is not exceeded. In addition, not all combinations of the features described in the embodiments are necessarily essential to the solution of the present invention.

  The characteristics of the ion exchange membranes in Examples and Comparative Examples were obtained by the following measurements.

(Electrical resistance measurement)
An ion-exchange membrane is sandwiched in a two-chamber cell having a platinum black electrode plate, and both sides of the ion-exchange membrane are filled with a 0.5 mol / l aqueous solution of sodium chloride. The resistance between them was measured. The difference between the inter-electrode resistance at this time and the inter-electrode resistance measured when no ion exchange membrane was installed was defined as the membrane resistance.
As the ion exchange membrane used for the above measurement, a membrane previously equilibrated in a 0.5 mol / l sodium chloride aqueous solution was used.

(Transport number measurement)
100 ml of 0.5 mol / L-potassium chloride aqueous solution was placed on the porous substrate side of a two-compartment acrylic cell separated by an asymmetric cation exchange membrane or an anion anion exchange membrane having an effective energization area of 4 cm ^2. 100 ml of a 0.1 mol / L aqueous solution of potassium chloride was applied to the ion exchange resin layer side of the exchange membrane, and the membrane potential was measured at a liquid temperature of 25 ° C. with a saturated calomel electrode through a salt bridge installed near the membrane surface. . Using the measured value of the membrane potential, the transport number was calculated and calculated from Equations 1 and 2.

Wherein, _{V M} is the membrane potential, _{t +} is a cation transport number, t _- transport number of the anion, R is the gas constant (8.314J / mol · K), T is the thermodynamic temperature, F is Faraday The constant, a _{± 1,} is the activity of a 0.1 mol / L-potassium chloride aqueous solution, and a _{± 2} is the activity of a 0.5 mol / L-potassium chloride aqueous solution.

(Measurement of ion exchange capacity)
The ion exchange membrane was immersed in a 1 mol / L-HCl aqueous solution for 10 hours or more.
Thereafter, in the case of a cation exchange membrane, the counter ion of the ion exchange group is replaced with sodium ion by a 1 mol / L-NaCl aqueous solution, and the liberated hydrogen ion is replaced with a potentiometric titrator (COMMITE) using an aqueous sodium hydroxide solution. -900, manufactured by Hiranuma Sangyo Co., Ltd.) (Amol). On the other hand, in the case of an anion exchange membrane, a counter ion is replaced with a nitrate ion with a 1 mol / L-NaNO ₃ aqueous solution, and the released chloride ion is replaced with a potentiometric titrator (COMMITE-900, (Amol). Next, the same ion exchange membrane was immersed in a 1 mol / L-NaCl aqueous solution for 4 hours or more, and then dried under reduced pressure at 60 ° C. for 5 hours, and the weight (Dg) at the time of drying was measured. Based on the above measured values, the ion exchange capacity of the ion exchange membrane was determined by the following equation.
Ion exchange capacity = A × 1000 / D [meq / g-dry mass]

(Burst strength measurement)
The burst strength of the ion-exchange membrane in a wet state was measured using a Mullen-type burst strength meter (manufactured by Toyo Seiki Seisaku-sho, Ltd.).

(Total thickness of ion exchange membrane, thickness of ion exchange resin layer and thickness of nonwoven fabric void layer)
The asymmetric ion exchange membrane was cut with a microtome (ESM-150S manufactured by Perma Sales Co., Ltd.) to form a measurement cross section. Next, the cross section of the membrane sample was observed with a 50 × objective lens using a color 3D laser microscope VK-8700 (manufactured by Keyence Corporation), and the ion-exchange resin layer (existing on the nonwoven fabric) thickness was observed from the observed image. And the thickness of the nonwoven fabric void layer (portion where no ion exchange resin is present) was measured.
The total thickness of the ion exchange membrane was measured using a micrometer MED-25PJ (manufactured by Mitutoyo Corporation). The thickness of the portion where the ion exchange resin bites into the nonwoven fabric is calculated by the following equation.
Biting thickness = (total thickness)-(ion exchange resin layer thickness)-(nonwoven fabric void layer thickness)

(Polymer solution viscosity)
The viscosity of the organic solvent solution (polymer solution) of the ion-exchange resin or the ion-exchange resin precursor was measured using a rotary cylindrical viscometer Visco Tester VT-04F (manufactured by Lion Corporation).

<Making of asymmetric cation exchange membrane>
Preparation of a polymer solution;
Polyphenylene oxide was dissolved in chloroform, and chlorosulfonic acid was added to the solution to react chlorosulfonic acid with the polyphenylene oxide. Subsequently, sodium hydroxide was added for neutralization, and the solvent was removed to obtain a sulfonated polyphenylene oxide (cation exchange resin) having an ion exchange capacity of 1.6 meq / g.
Next, the sulfonated polyphenylene oxide was dissolved in N, N-dimethylformamide to a concentration of 28% by mass to prepare a sulfonated polyphenylene oxide solution. The solution viscosity was 20 dPa · s.

Non-woven sheet;
Novatex x2442 manufactured by Freudenberg (weight 25 g / m ² , thickness 0.06 mm, air permeability 180 cm ³ / cm ² · sec), or PY120-19 manufactured by Awa Seishi Co., Ltd. (weight 14 g / m ² , thickness 0.02 mm, An air permeability of 82 cm ³ / cm ² · sec) was used.

Manufacture of ion exchange membranes;
The polymer solution prepared above was applied to a PET film using a bar coater so as to have a liquid thickness of 50 μm to form a coating layer (cast layer).
The PET film on which the coating layer is formed is dried at 50 ° C. for 5 minutes, and then the non-woven sheet is overlaid on the PET film and laminated with a roller to form an ion-exchange resin coating layer on one surface of the non-woven sheet. I let it.
Next, the coating layer was solidified by heating and drying at 60 ° C., and thereafter, the PET film was peeled off to obtain an asymmetric cation exchange membrane. The physical properties of the obtained cation exchange membrane are shown in Table 1.

<Making of asymmetric anion exchange membrane>
Preparation of a polymer solution;
100 g of a copolymer composed of segments of polystyrene (65% by mass) and hydrogenated segments of polyisoprene (35% by mass) were dissolved in 1000 g of chloroform, and 100 g of chloromethyl methyl ether and 10 g of tin chloride were added. The reaction was performed at 15 ° C. for 15 hours. Next, the precipitate was washed in methanol, washed, and dried to obtain a chloromethylated styrene-based block copolymer. Next, chloromethylated polystyrene having a molecular weight of 5000 was mixed with the above-mentioned chloromethylated styrene-based block copolymer so as to adjust the ratio of chloromethylated polystyrene to 40% by mass. The chloromethylated polymer mixture thus obtained was dissolved in tetrahydrofuran to form a 25% by mass solution, and N, N, N ', N'-tetramethyl-1,6-hexanediamine was added to the solution. In addition to 8% by mass, a polymer solution for forming an anion exchange membrane containing an anion exchange resin precursor and an anion exchange group-introducing agent was prepared. The viscosity of the polymer solution was 5 dPa · s.

Manufacture of ion exchange membranes;
The polymer solution prepared above was applied to a PET film using a bar coater so as to have a liquid thickness of 50 μm to form an application (cast) layer.
The PET film on which the coating layer is formed is dried at 30 ° C. for 0.5 minute, and then the same nonwoven fabric sheet used in the production of the asymmetric cation exchange membrane is laminated on the coating layer and roller-pressed to be laminated. As a result, an ion exchange resin coating layer was formed on one surface of the nonwoven fabric sheet.
Next, the coating layer was solidified by heating and drying at 40 ° C., and then the PET film was peeled off to obtain an asymmetric anion exchange membrane. Table 1 shows the physical properties of the obtained asymmetric anion exchange membrane.

<Example 1 of electrodialysis>
In the electrodialysis apparatus, a cation exchange membrane 1 and an anion exchange membrane 1 (see Table 1 for structure and performance) are alternately provided between a pair of a cathode (Ti-Pt coat) and an anode (Ti-Pt coat). Eleven, ten (the effective membrane areas of the cation exchange membrane and the anion exchange membrane are each 0.55 dm ² / sheet), and a filter press type electrodialysis device acylizer S3 type in which a concentration chamber and a desalination chamber are formed. (Made by Astom Co., Ltd.). The cation exchange membrane 1 and the anion exchange membrane 1 were all set so that the ion exchange resin layer surface faced the desalting chamber.
500 ml of a 0.5 mol / L sodium chloride aqueous solution (conductivity of 46.8 mS / cm) was put into the desalting chamber tank of this electrodialysis apparatus, while a 0.51 mol / L sodium chloride aqueous solution (47 (0.6 mS / cm), and a constant voltage operation (electrode voltage: 5 V) was performed at 25 ° C. while circulating each. As the electrode solution, a 0.5 mol / L aqueous solution of sodium sulfate was used.
While monitoring the value of the current flowing between both electrodes, electrodialysis was performed until the conductivity of the desalted solution became 2 mS / cm (about 0.01 mol / L). The required processing time (operating time) was measured, and the processing capacity (desalting capacity) was calculated from this and the amount of the desalted solution charged according to the following equation. The effective film area is 5.5 dm ² (0.55 dm ² × 10 pairs). Table 3 shows the results.

<Example 2 of electrodialysis>
1000 ml of a 0.02 mol / L aqueous sodium chloride solution (2.0 mS / cm) was put into the desalting chamber tank of the electrodialyzer, while a 0.1 mol / L sodium chloride aqueous solution (10.7 mS / cm) was placed in the concentration chamber tank. cm) Electrodialysis was carried out in the same manner as in Example 1 except that 500 ml was charged.
The treatment time until the conductivity of the desalted solution became 0.3 mS / cm (about 2.0 mmol / L) was measured, and the desalting capacity was calculated as in Example 1 for electrodialysis. The results are shown in Table 3.

<Example 3 of electrodialysis>
The measurement was performed in the same manner as in Example 1 of the electrodialysis except that the ion exchange membranes disposed in the electrodialysis apparatus were changed to the cation exchange membrane 2 and the anion exchange membrane 2 (for the structure and performance, see Table 1). 3 is shown.

<Example 4 of electrodialysis>
The measurement was performed in the same manner as in Example 2 of the electrodialysis except that the ion exchange membranes arranged in the electrodialysis apparatus were changed to the cation exchange membrane 2 and the anion exchange membrane 2 (for the structure and performance, see Table 1). 3 is shown.

<Comparative example 1 of electrodialysis>
The measurement was carried out in the same manner as in Example 1 for electrodialysis, except that the ion exchange resin layer surfaces of the cation exchange membrane 1 and the anion exchange membrane 1 were set to face the concentration chamber, and the results are shown in Table 3. Desalination capacity was reduced by 20%.

<Electrodialysis Comparative Example 2>
The measurement was carried out in the same manner as in Example 2 of electrodialysis, except that the ion exchange resin layer surfaces of the cation exchange membrane 1 and the anion exchange membrane 1 were set to face the concentration chamber, and the results are shown in Table 3. Desalination capacity was reduced by 40%.

<Electrodialysis Comparative Example 3>
The measurement was carried out in the same manner as in Example 3 of electrodialysis, except that the ion exchange resin layer surfaces of the cation exchange membrane 2 and the anion exchange membrane 2 were set to face the concentration chamber, and the results are shown in Table 3. Desalination capacity decreased by 11%.

<Electrodialysis Comparative Example 4>
The measurement was performed in the same manner as in Example 4 of electrodialysis, except that the ion exchange resin layer surfaces of the cation exchange membrane 2 and the anion exchange membrane 2 were set to face the concentration chamber, and the results are shown in Table 2. Desalination capacity was reduced by 36%.

<Example 1 for reverse electrodialysis>
A cation exchange membrane 1 and an anion exchange membrane 1 (see Table 1 for structure and performance) were alternately provided between a pair of positive and negative electrodes composed of a silver-silver chloride electrode, respectively. The effective membrane area of the anion exchange membrane is 0.55 dm ² / sheet), and a filter press type reverse electrodialysis device (manufactured by Astom Co., Ltd., gasket thickness 0.2 mm) having a rich chamber and a lean chamber is provided. It was constructed. The cation exchange membrane 1 and the anion exchange membrane 1 were all set so that the ion exchange resin layer surface faced the lean chamber.
500 ml of a 0.5 mol / L aqueous solution of sodium chloride (46.8 mS / cm) was placed in a concentrated chamber tank of the reverse electrodialysis apparatus, and circulated at a linear velocity of 1.0 cm / sec on the membrane surface. On the other hand, 500 ml of a 0.002 mol / L aqueous solution of sodium chloride (0.25 mS / cm) was placed in the dilute chamber tank and circulated at a linear velocity of 1.0 cm / sec on the membrane surface. As the electrode solution, a 3.0 mol / L aqueous sodium chloride solution was used. The maximum output was obtained by drawing a current-voltage curve using a potentiostat built in the apparatus. The results are shown in Table 5. The liquid temperature during operation was set at about 25 ° C.

<Example 2 for reverse electrodialysis>
Reverse electrodialysis except that a 1.0 mol / L aqueous sodium chloride solution (85.8 mS / cm) was used in the rich chamber and a 0.005 mol / L aqueous sodium chloride solution (0.6 mS / cm) was used in the lean chamber. The measurement was performed under the same conditions as in Example 1, and the results are shown in Table 5.

<Example 3 of reverse electrodialysis>
The measurement was carried out in the same manner as in Example 1, except that the ion exchange membranes arranged in the reverse electrodialysis apparatus were changed to the cation exchange membrane 2 and the anion exchange membrane 2 (see Table 1 for the structure and performance). Are shown in Table 5.

<Example 4 of reverse electrodialysis>
The measurement was carried out in the same manner as in Example 2 of reverse electrodialysis, except that the ion exchange membrane arranged in the reverse electrodialysis apparatus was changed to the cation exchange membrane 2 and the anion exchange membrane 2 (for the structure and performance, see Table 1). Are shown in Table 5.

<Comparative Example 1 for reverse electrodialysis>
The measurement was performed in the same manner as in Example 1 of reverse electrodialysis, except that the ion exchange resin layer surfaces of the cation exchange membrane 1 and the anion exchange membrane 1 were set to face the rich chamber, and the results are shown in Table 5. The maximum output decreased by 50%.

<Comparative Example 2 for reverse electrodialysis>
The measurement was performed in the same manner as in Example 2 of reverse electrodialysis, except that the ion exchange resin layer surfaces of the cation exchange membrane 1 and the anion exchange membrane 1 were set to face the rich chamber, and the results are shown in Table 5. The maximum output decreased by 40%.

<Comparative Example 3 for reverse electrodialysis>
The measurement was carried out in the same manner as in Example 3 of reverse electrodialysis, except that the ion exchange resin layer surfaces of the cation exchange membrane 2 and the anion exchange membrane 2 were set to face the rich chamber, and the results are shown in Table 5. The maximum output decreased by 44%.

<Comparative Example 4 for reverse electrodialysis>
The measurement was carried out in the same manner as in Example 4 of reverse electrodialysis, except that the ion exchange resin layer surfaces of the cation exchange membrane 2 and the anion exchange membrane 2 were set to face the rich chamber, and the results are shown in Table 5. The maximum output decreased by 36%.

1 electrodialysis machine,
10 cathode,
11 anode,
13 desalination room,
15 Concentration room,
17 electrode diaphragm,
19 low concentration processing solution,
21 high concentration electrolyte solution,
30 gasket spacer,
31 gasket frame,
33, 33 'communication holes for processing liquids,
35, 35 'communicating holes for electrolyte solution,
37 a distribution section for the processing liquid,
39 distribution section for electrolyte solution,
40 ion exchange resin layer,
50 reverse electrodialysis machine,
51 negative electrode,
53 positive electrode,
55 sparse room,
57 Rich Room,
59 low concentration electrolyte solution,
61 high concentration electrolyte solution,
63 electrical equipment

Claims (12)

In an electrodialysis apparatus in which an ion exchange membrane is disposed in a space between a cathode and an anode, and further, a desalting chamber and a concentration chamber are formed by the ion exchange membrane,
The ion exchange membrane is an asymmetric ion exchange membrane in which an ion exchange resin layer is formed on one surface of a porous substrate,
An electrodialysis apparatus, wherein the asymmetric ion exchange membrane is installed such that the surface on which the ion exchange resin layer is formed is on the desalination chamber side.   The electrodialysis device according to claim 1, wherein the porous substrate is a nonwoven fabric.   Cation exchange membranes and anion exchange membranes are alternately arranged in the space between the cathode plate and the anode plate, and are separated between the anion exchange membrane on the anode plate side and the cation exchange membrane on the cathode plate side. 3. The electrodialysis apparatus according to claim 1, wherein a salt chamber is formed, and a concentration chamber is formed between the cation exchange membrane on the anode plate side and the anion exchange membrane on the cathode plate side.   All ion exchange membranes forming the desalting chamber and the concentration chamber are asymmetric ion exchange membranes, and are installed such that the surface on which the ion exchange resin layer is formed is located on the desalination chamber side. An electrodialysis device according to claim 3.   Electrodialysis for supplying an electrolytic solution to a desalting chamber and supplying an electrolytic solution having a higher concentration than the electrolytic solution supplied to the desalting chamber to the concentration chamber using the electrodialysis apparatus according to any one of claims 1 to 4. Method.   The electrodialysis method according to claim 5, wherein the electrolyte solution supplied to the desalting chamber has an electric conductivity (25 ° C) of 0.05 to 100 mS / cm. In a reverse electrodialysis apparatus in which an ion exchange membrane is disposed in a space between the negative electrode and the positive electrode, and further, a lean chamber and a rich chamber are formed by the ion exchange membrane,
The ion exchange membrane is an asymmetric ion exchange membrane in which an ion exchange resin layer is formed on one surface of a porous substrate,
A reverse electrodialysis apparatus, wherein the asymmetric ion exchange membrane is installed such that the surface on which the ion exchange resin layer is formed is on the lean chamber side.   The reverse electrodialysis device according to claim 7, wherein the porous substrate is a nonwoven fabric.   In the space between the negative electrode plate and the positive electrode plate, cation exchange membranes and anion exchange membranes are alternately arranged, and a thin film is provided between the anion exchange membrane on the positive electrode plate side and the cation exchange membrane on the negative electrode plate side. The reverse electrodialysis apparatus according to claim 7 or 8, wherein a chamber is formed, and a rich chamber is formed between the cation exchange membrane on the positive electrode plate side and the anion exchange membrane on the negative electrode plate side.   All ion exchange membranes forming the lean chamber and the rich chamber are asymmetric ion exchange membranes, and are installed such that the surface on which the ion exchange resin layer is formed is on the lean chamber side. Item 10. A reverse electrodialysis device according to item 9.   The reverse electrodialysis apparatus according to any one of claims 7 to 10, wherein an electrolyte solution is supplied to the lean chamber, and an electrolyte solution having a higher concentration than the electrolyte solution supplied to the lean chamber is supplied to the rich chamber. Reverse electrodialysis method.   The reverse electrodialysis method according to claim 11, wherein the electrolyte solution supplied to the lean chamber has an electric conductivity (25 ° C) of 0.005 to 1 mS / cm.