JPH09151260A - Hydrogen ion selective permeable membrane and electrodialysis method - Google Patents

Abstract

(57) Abstract: To obtain a hydrogen ion selective permeable membrane which is inexpensive and has excellent chemical resistance. A diaphragm for an electrodialysis method for selectively permeating hydrogen ions from an aqueous solution containing hydrogen ions on the anode side to the cathode side, which is composed of particles of a cation exchange resin and a binder polymer. Hydrogen ion selective permeable membrane having an anion exchanger layer formed on at least one surface of the heterogeneous cation exchange membrane.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrogen ion selective permeation membrane for selectively permeating hydrogen ions from an aqueous solution containing hydrogen ions on the anode side to the cathode side, and an electrodialysis method using the membrane.

[0002]

2. Description of the Related Art The membrane separation technique by electrodialysis has been used for seawater concentration and desalination, but has recently been applied to other processes. One of these is the concentrated recovery of acid from acid-containing solutions, a process that is becoming more important from a pollution and economic standpoint.
For example, sulfuric acid-containing solution from non-ferrous metal ore or metal pickling step, hydrochloric acid-containing solution from extraction step or pickling step, hydrofluoric acid-containing solution from tantalum or lead processing step, solvent extraction etching step Hydrochloric acid or sulfuric acid or nitric acid containing solution, chromic acid containing solution from plating process,
Concentrated recovery of acid from various acid-containing solutions such as acid-containing solution from the ion exchange resin regeneration step and sulfuric acid recovery solution from wood saccharification solution.

In these acid recovery processes, in order to efficiently recover the acid, a hydrogen ion selective permeable membrane that selectively permeates hydrogen ions and excludes metal ions is essential. As a method for imparting such a selectivity to hydrogen ions to a membrane, in JP-A-5-228344, excellent hydrogen ion selective permeation is achieved by allowing a specific anion exchange material to exist on the surface of a cation exchange membrane. It is illustrated that the property can be realized.

[0004]

However, the cation-exchange membrane of styrene-divinylbenzene copolymer type, which has been conventionally used as a cation-exchange membrane constituting a hydrogen ion selective permeable membrane, is not suitable for polymerization and sulfone formation during membrane formation. Since it involves complicated and sensitive steps such as cost reduction, it is costly, and it is difficult to control heat generation and dimensional change generated at that time, resulting in a low yield and an expensive price. Further, the styrene-divinylbenzene-based film has poor chemical resistance, particularly oxidation resistance to nitric acid and the like. Therefore, a hydrogen ion selective permeable membrane using a cation-exchange membrane of styrene-divinylbenzene copolymer system is also expensive and does not have high chemical resistance.

[0005]

The present invention provides a heterogeneous cation exchanger layer composed of cation exchange resin particles and a binder polymer, and an anion exchanger layer laminated on at least one surface thereof. A hydrogen ion selective permeable membrane comprising a multi-layer membrane of

The present invention is also an electrodialysis method of selectively permeating hydrogen ions from an aqueous solution containing hydrogen ions on the anode side to the cathode side through the membrane, wherein the membrane is a cation exchange resin particle and a binder. Provided is an electrodialysis method which is a hydrogen ion selective permeable membrane comprising a multi-layer membrane comprising a heterogeneous cation exchanger layer composed of a polymer and an anion exchanger layer laminated on at least one surface thereof.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The hydrogen ion selective permeable membrane of the present invention can be produced by a method of joining a heterogeneous cation exchanger layer and an anion exchanger layer. For example, a method of casting a polymer solution for forming an anion exchanger layer on the surface of a heterogeneous cation exchanger layer, drying and laminating the same, a heterogeneous cation exchanger layer and an anion exchanger layer formed in advance. The method of thermocompression bonding is preferably used.

The hydrogen ion selective permeable membrane of the present invention is a woven fabric,
It can also be reinforced with a knitted fabric, nonwoven fabric, porous body or the like. Further, the shape of the hydrogen ion selective permeable membrane can be not only a flat membrane shape but also a bag shape, a hollow fiber shape, a hollow tubular shape and the like.

The heterogeneous cation exchanger layer is composed of particles of cation exchange resin and a binder polymer.
The proportion of the cation exchange resin particles and the binder polymer mixed is preferably 40 to 75% by weight of the cation exchange resin with respect to the total amount of the cation exchange resin and the binder polymer. When the amount of the ion exchange resin is less than 40% by weight, the electric resistance remarkably increases, which is not preferable. When the amount of the cation exchange resin exceeds 75% by weight, the mechanical strength of the heterogeneous cation exchanger may be remarkably lowered and molding may not be possible, which is not preferable.

Examples of the cation exchange resin include a styrene-divinylbenzene copolymer, a methacrylic acid-divinylbenzene copolymer, an acrylic acid-divinylbenzene copolymer, and the like. Those into which an acid group or a salt thereof is introduced can be used. From the viewpoint of electric resistance in an aqueous acid solution, a cation exchange resin having a sulfonic acid group or a salt thereof as a cation exchange group is preferably used.

The ion exchange capacity of the cation exchange resin is 1.
0-5.0 meq / g dry resin is preferred. If the ion exchange capacity is smaller than this, the electric resistance of the obtained heterogeneous cation exchanger will be high, and if it is larger than this, the mechanical strength of the heterogeneous cation exchanger layer may be remarkably reduced, which is preferable. Absent.

The maximum particle size of the cation exchange resin is 7
It is preferably less than 5 μm. Maximum particle size is 75 μm
The above cases are not preferable because the viscosity at the time of melt-molding the heterogeneous cation exchanger may be increased and the moldability may be lowered, and the resulting cation exchanger has large irregularities on its surface. Maximum particle size of cation exchange resin is 45μ
It is more preferable if it is less than m.

The binder polymer includes polyolefins such as polyethylene, polypropylene and polyisobutylene, polyhalogenated olefins such as polyvinyl chloride, polyvinylidene chloride and polyvinylidene fluoride, isoprene rubber, chloroprene rubber, butadiene rubber and styrene-butadiene rubber. , Synthetic rubber such as acrylonitrile-butadiene rubber and ethylene-propylene rubber, natural rubber, styrene thermoplastic elastomer, olefin thermoplastic elastomer and the like can be used. Of these, polyolefins and olefin-based thermoplastic elastomers have excellent chemical resistance and are preferably used.

The heterogeneous cation exchanger layer is preferably prepared by drying, pulverizing and classifying a cation exchange resin, kneading it with a binder polymer, and then subjecting it to hot melt molding such as extrusion molding and heat press molding.

The anion exchanger layer used in the present invention preferably has an ion exchange capacity of 0.5 to 4 meq / g dry resin. The anion exchanger layer preferably has a fixed ion concentration of 1 to 10 meq / gH ₂ O and a thickness of 0.1 to 150 μm. Fixed ion concentration is 1.0 meq /
If it is less than gH ₂ O, the cations other than hydrogen ions have a high permeability, and the selective permeability of hydrogen ions is low, resulting in 10 meq /
If it exceeds gH ₂ O, water splitting easily occurs, which is not preferable. Further, if the thickness of the anion exchanger layer is less than 0.1 μm, the selective permeability of hydrogen ions is lowered, and if it exceeds 150 μm, water splitting tends to occur, which is not preferable.

As the material of the anion exchanger layer, a copolymer of styrene or chloromethylstyrene and divinylbenzene into which an anion exchange group is introduced, vinyl pyridine type polymer, vinyl aniline type polymer, vinyl imidazole. Examples thereof include a polymer, an epoxy / amine polymer, and a fluoropolymer having an anion exchange group at the end of a side chain and a main chain made of a perfluoropolymer.

Among them, from the viewpoint of being excellent in mechanical strength, heat resistance, chemical resistance and thin film formability, the repeating unit has the general formula -X-Ar-Y- (where X and Y are the same as each other). The same or different electron-donating linking groups are represented, preferably -O-, -S-, an alkylene group having 1 to 13 carbon atoms or a single bond, and Ar is

[0018]

Embedded image

## EQU1 ## Here, R _{1 to} R ₅ are the same or different hydrocarbon groups having 1 to 8 carbon atoms, and a is 0 to
4, b + c is selected from 0 to 6, and d + e is selected from 0 to 6. )
It is preferable to use an anion-exchanger layer which is composed of an aromatic polymer having a and has an anion-exchange group introduced into its aromatic ring.

When the anion-exchanger layer is composed of a block copolymer comprising a segment having an ion-exchange group introduced therein and a segment having no ion-exchange group substantially introduced therein, the resulting hydrogen ion-selective permeable membrane is obtained. Is particularly preferable because it has high hydrogen ion selective permeability and excellent mechanical properties.

Examples of such block copolymers include polyphenylene oxide / polyether sulfone copolymer, polyphenylene sulfide / polyether sulfone copolymer, polyaryl ether sulfone / polyether sulfone copolymer, polyaryl ether arylate / Examples thereof include polyarylate copolymers and polyaryl ether sulfone / polythioether sulfone copolymers. For example,

[0022]

Embedded image

Is exemplified. However, m and n are 2 to 20
0, m / n is 100/1 to 1/10.

To carry out electrodialysis using the hydrogen ion selective permeable membrane of the present invention, for example, an electrodialysis tank in which a plurality of hydrogen ion selective permeable membranes of the present invention and anion exchange membranes are alternately arranged in pairs is constructed, It is preferable to operate so that the current density is equal to or lower than the limit current density. It is preferable to form an anion exchanger layer on one surface of the hydrogen ion selective permeable membrane and arrange it so that this surface faces the anode side. With such a device, it is possible to recover acid from, for example, an acid waste liquid containing heavy metals.

[0025]

EXAMPLES In the examples, the hydrogen ion selective permeability and the limiting current density were measured as follows.

(1) Selective Permeability of Hydrogen Ions A multi-layer membrane having an anion-exchange layer laminated on one surface of a cation-exchange layer and an anion-exchange membrane between the two electrodes is used as an anion-exchange membrane. The ion exchanger layers are alternately arranged so as to face the anode side to form an electrodialysis cell. A solution containing 0.5N HCl and 0.5N FeCl ₂ was supplied to the desalting chamber side of this electrodialysis tank, and 3N HCl was supplied to the concentrate side to obtain a current density of 3 A / dm ² . Perform electrodialysis. Based on the current efficiencies of iron ions and hydrogen ions that permeate the concentrating chamber, the hydrogen ion selective permeability is calculated according to the following formula.

[0027]

(Equation 1)

(2) Limit Current Density When electrodialysis is performed in a system similar to the measurement in the above (1), the current density is changed and the corresponding voltage value is measured. The current density and the voltage value are usually in a proportional relationship, and a straight line is obtained. However, since a bent point occurs on a straight line above a certain current density point, this point is defined as a limit current density.

Example 1 A cation exchange resin having a sulfone group introduced into a styrene / divinylbenzene copolymer (manufactured by Mitsubishi Chemical Corporation, trade name Diaion SK-1B, ion exchange capacity 4.4me).
(q / g dry resin) was dried with warm air at 60 ° C. for 24 hours and then pulverized with a rotor mill. The crushed particles were sieved with a stainless mesh to remove particles having a particle size of 45 μm or more. The obtained cation exchange resin particles having a particle size of less than 45 μm and an ethylene / octene-1 copolymer (trade name: Affinity SM1300, manufactured by Dow Chemical Co., Ltd.) as a binder polymer were mixed at an ion exchange resin / binder polymer mixing ratio of 70/30. (Weight ratio), and kneaded with a Labo Plastomill at 110 ° C. for 20 minutes. The resulting kneaded product is heated and melt-pressed at 160 ° C. by a flat plate press to a thickness of 5
It was shaped into a membrane of 00 μm to obtain a heterogeneous cation exchanger layer.

The anion exchanger layer was formed as follows. 0.36 mol of 4,4'-diphenol is reacted with 0.396 mol of dichlorodiphenylsulfone to synthesize 0.36 mol of an m = 10 precursor composed of aromatic polysulfone units.
6 mol, 0.324 mol of dichlorodiphenyl sulfone and 0.378 mol of sodium sulfide were reacted to obtain 220 g of an aromatic polysulfone / polythioether sulfone copolymer represented by Chemical formula 3.

[0031]

Embedded image

(However, m = n = 10. The intrinsic viscosity of this aromatic polysulfone / polythioether sulfone copolymer is 0.50.)

Next, 75 g of the copolymer was added to 1,1,2,2
-Dissolved in 1020 ml of tetrachloroethane, 400 g of chloromethyl methyl ether and 4.5 of anhydrous tin chloride
g was further added, and the mixture was heated to a temperature of 110 ° C. and the chloromethylation reaction was carried out for 4 hours. After the reaction was completed, the reaction product was precipitated using 5000 ml of methyl alcohol,
This was washed to obtain 85 g of a chloromethylated copolymer.
The introduction rate of chloromethyl groups in the obtained chloromethylated copolymer was about 1.9 per repeating unit, and the ion exchange capacity when all were reacted with trimethylamine was 2.2 m.
It was eq / g resin.

50 g of the chloromethylated copolymer thus obtained was dissolved in 300 ml of N, N-dimethylformamide to prepare a 15 wt% solution. While stirring under cooling, 108 ml of a 1N solution of trimethylamine in N, N-dimethylformamide was slowly added dropwise at a temperature of 0 ° C., and then 66 g of 2-methoxyethanol was added,
A solution A having an ion exchange capacity of 2.0 meq / g was obtained (hereinafter, this solution is referred to as an aminated polymer solution A).

The aminated polymer solution A was cast on the above heterogeneous cation exchanger layer and dried, and an anion exchanger layer having an ion exchange capacity of 2.0 meq / g was laminated in a thickness of 3 μm to select hydrogen ions. A permeable membrane was obtained. When the hydrogen ion selective permeability and the limiting current density of this membrane were measured, the selectivity was 140 and the limiting current density was 12 A / dm ² . The hydrogen ion selective permeable membrane was immersed in a 3N nitric acid solution at 60 ° C. for 5 days, and the weight loss rate was measured to be 2.5%.

Example 2 (Comparative) 14.8 parts by weight divinylbenzene, 16.9 parts by weight butyl acrylate, 53.0 parts by weight styrene monomer, 5.1 parts by weight nitrile rubber, 8.5 parts by weight. 90 ml of a monomer solution containing dioctyl phthalate as a plasticizer and 1.7 parts by weight of benzoyl peroxide as a polymerization initiator was impregnated into a 1 m square woven cloth made of polyvinyl chloride. Then, the impregnated woven fabric is sandwiched between both sides with a polyester film, and the monomer is polymerized by heating at a temperature of 60 ° C for 1.5 hours, and further heating to 70 ° C for 5 hours to give a styrene / divinylbenzene copolymer weight. A woven fabric impregnating and holding the coalescence was obtained. This woven cloth is concentrated sulfuric acid 1
The styrene / divinylbenzene copolymer impregnated in the woven fabric was sulfonated by immersion in 0 liter. As a result, a cation exchange membrane composed of a styrene / divinylbenzene copolymer reinforced with a woven fabric having a film thickness of 120 μm and an ion exchange capacity of 2.0 meq / g dry resin was obtained.

On the surface of the obtained cation exchange membrane, the same aminated polymer solution A as in Example 1 was cast and dried, and an anion exchanger layer having a thickness of 3 μm was laminated. When the hydrogen ion selective permeability and the limiting current density of this multilayer film were measured, the selectivity was 1
40, the limiting current density was 12 A / dm ² . The hydrogen ion selective permeable membrane was immersed in a 3N nitric acid solution at 60 ° C. for 5 days, and the weight loss rate was measured to be 25%.
The film of Example 1 had better chemical resistance than the film of Example 2.

[0038]

INDUSTRIAL APPLICABILITY The hydrogen ion selective permeable membrane of the present invention has excellent chemical resistance and can be advantageously applied to a deoxidation process such as concentrated recovery of a high-purity acid from a low-concentration waste acid solution or pH adjustment. In the hydrogen ion selective permeable membrane of the present invention, a cation exchange membrane can be obtained at a low cost by a relatively simple process without the steps of polymerization and reaction, and thus a cheap hydrogen ion selective permeable membrane can be obtained.

Claims (4)

[Claims] 1. A hydrogen ion comprising a multi-layered film comprising a heterogeneous cation exchange layer composed of cation exchange resin particles and a binder polymer, and an anion exchange layer laminated on at least one surface thereof. Selective permeable membrane. 2. The method according to claim 1, wherein the anion exchanger layer has an ion exchange capacity of 0.1.
5-4 meq / g dry resin, fixed ion concentration 1-10m
The hydrogen ion selective permeable membrane according to claim 1, having an eq / gH ₂ O and a film thickness of 0.1 to 150 μm. 3. An anion-exchanger layer is a segment substantially composed of an aromatic ring and a linking group, wherein the anion-exchange group-introduced segment and the anion-exchange group are substantially-introduced. The hydrogen ion-selective permeable membrane according to claim 1 or 2, which is composed of a block copolymer with a segment not present. 4. An electrodialysis method for selectively permeating hydrogen ions from an aqueous solution containing hydrogen ions on the anode side through a diaphragm, wherein the diaphragm comprises cation exchange resin particles and a binder polymer. An electrodialysis method which is a hydrogen ion selective permeable membrane comprising a multi-layer membrane comprising a heterogeneous cation exchanger layer and an anion exchanger layer laminated on at least one surface thereof.