JPS60166330A - Treatment for imparting selectivity to cation exchange membrane - Google Patents

Abstract

PURPOSE:To improve the selective ion permeability and durability of a cation exchange membrane, by swelling a cation exchange membrane with a mixture of an organic material and water, and contacting the membrane with a polymeric substance having anion exchange group, thereby forming a thin layer to the surface of the membrane. CONSTITUTION:(A) A polymer having anion exchange group such as quaternary ammonium group, primary-tertiary amino group, etc. is used as the selectivity- improving agent. The compound A is dissolved or dispersed in the mixture of water and (B) an organic material having a molecular weight of <=500, free from cation exchange group nor anion exchange group, and having a water-solubility of >=0.1% at the treating temperature, e.g. dimethylformaldehyde, ethanol, etc. Separately, a cation exchange membrane is impregnated with the mixture of water and the compound B, and is made to contact with the above solution or dispersion. A layer which does not cause the increase in the electrical resistance of the cation exchange membrane can be formed on the surface of the membrane. The amount of the compound A dissolved or dispersed is preferably 0.1- 50g per 1l of the treating liquid.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a treatment method for improving the ion selective permeability of a cation exchange membrane. In detail, a permeation ion selective treatment method for a cation exchange membrane for electrodialyzing an electrolyte solution containing two or more cations with different charges and selectively electrodialyzing cations with a small ionic charge. Regarding.

Conventionally, when concentrating seawater using the ion exchange membrane method for manufacturing food tombs, cation exchange membranes were used to remove sodium ions (
It is desirable to pass calcium ions (Ca) and magnesium ions (c) more selectively than calcium ions (Ca) and magnesium ions (c) from the two viewpoints of preventing gypsum scale precipitation in the concentrate and improving the current efficiency of the target cations. ing. Various methods have been proposed to provide such selectivity, but in particular,
The method of bringing a polymer having an ion-exchange group into contact with a cation-exchange membrane to form a thin layer on the membrane surface, as in 44155-44155, is preferred because it is easy to operate. However, with this method, although the electrical resistance of the membrane does not substantially increase, the selective permeation performance and durability between monovalent cations and divalent cations are insufficient, and as in recent years, the concentration of concentrated liquid has been reduced. If the system is operated at high elevations, problems such as gypsum depositing on the concentration side of the anion exchange membrane are likely to occur.

The present inventors further improved the selective permselectivity of -valent ions,
Moreover, it has sufficient durability, and as a result of examining methods that do not increase the electrical resistance of the cation exchange membrane,
During the above-mentioned selection process, the inventors discovered that by bringing the cation exchange membrane swollen with a mixture of organic matter and water into contact with a polymer substance having an anion exchange group, the selectivity could be greatly improved, and the present invention was achieved. reached.

The present invention involves bringing a cation exchange membrane into contact with a selective treatment agent, which is a molecular substance having an anion exchange group, to form a thin layer on the membrane surface that does not increase the air supply resistance of the cation exchange membrane. A selective treatment method for a cation exchange membrane, characterized in that the cation exchange membrane during treatment is impregnated with at least one organic substance and water in addition to a selective treatment agent. be.

Examples of polymeric substances having anion exchange groups that can be used in the present invention include polymers having molecular weights of 500 or more and linear polymers having cation exchange groups, as shown in Japanese Patent Publication No. 46-2360A. Examples include insoluble polymers having anion exchange groups such as JL solute and those shown in Japanese Patent Publication No. 53-44155-1. Specifically, for example, a quaternary ammonium group such as a copolymer of styrene and divinylbenzene that is chloromethylated and then aminated,
A pyridine group such as poly-vinylpyridine, a quaternary pyridinium group such as a quaternized version thereof, a primary, secondary or tertiary amino group such as a condensate of guanylurea and formalin, an imino group such as polyethyleneimine. Examples include polymers with groups. In this case, the anion exchange group is preferably a quaternary ammonium salt, which may be used alone or in combination with a primary to tertiary amine group, etc.
In addition, the exchange capacity is 0.5 v (dry, preferably on ILI). Also, when using an insoluble polymer, the degree of cross-linking is at most 10% (the molar ratio of the cross-linking agent is 2-functional monomer equivalent). ) and the particle size is 100μ or less.

After dissolving or suspending a polymer having such anion exchange groups (hereinafter referred to as a treatment agent) in water, an aqueous salt solution, or a mixture of an organic substance and water (or an aqueous salt solution), a cation exchange membrane is formed. A selective treatment of the cation exchange membrane is carried out by catalyzing it. At the time of this contact, it is important that the cation exchange membrane be in a swollen state with at least the mixture of organic matter and water. This has the advantage that selectivity even better than previously known selectivity can be obtained and/or the durability of the selectivity can be improved. Examples of organic substances that impregnate the membrane with water include: ■ Organic solvents that are polar and compatible with water such as dimethyl formaldehyde and dimethyl sulfoxide; ■ Alcohols such as ethanol and benzyl alcohol; ■ Dioxa/ban ethers; ■ Examples include esters such as phthalate esters, and aldehydes such as dithyl aldehyde. That is, the organic substance is preferably one that dissolves at least 1% in water K 2 O at the treatment temperature and has no cation exchange group or anion exchange group and has a molecular weight of 500 or less. Furthermore, when the membrane is impregnated, the amount of the organic substance is 1% or more and 20% or less, more preferably 10% under the treatment conditions.
It is preferable to control the organic substance and impregnation ratio so that the film elongates as follows. There are several methods for impregnating the membrane with a mixture of organic matter and water during the selectivity treatment, including the following.

■ After dissolving or suspending the treatment agent in a mixture of organic matter and water (or salt water), at least a cation exchange membrane impregnated with water (or salt water) or a mixture of water (or salt water) and organic matter. How to touch one side.

■ After dissolving or suspending the treatment agent in water (or salt water),
A method in which at least one side of a cation exchange membrane impregnated with an organic substance or a mixture of an organic substance and water (or salt water) is brought into contact.

In this case, if an organic material having good compatibility with °C water is selected, it is preferable not to select method (2). In addition, when a water-compatible adhesive v organic substance is selected, it is preferable to carry out the method as in (2).

The processing agent concentration in the processing solution is 0.1150 per liter.
It is preferable that the second processing agent is dissolved or suspended. Also, when processing a new cation exchange membrane, the temperature should be 10 to 150℃.
It is preferable to contact the treatment liquid for several minutes to several hours. At this time, electricity may be applied for acceleration. Further, after the treatment, if the treatment agent is a polymer or linear polymer with a molecular weight of 500 or more, it may be further reacted on the surface to cause crosslinking between the matrix and the treatment agent to make it insolubilized. Further, after performing these selective treatments, it is desirable to remove organic substances in the membrane by means such as extraction, equilibrate it with water or salt water, and then use it for electrodialysis.

Although the mechanism of the effect of the treatment of the present invention is not clear, it is believed that the formation of a cation exchange membrane using a mixture of organic matter and water is effective. determined.

Furthermore, in conventional treatments, substantially good specific permselectivity cannot be obtained unless the treatment is carried out at a temperature exceeding at least 70°C, unless a specially cross-linked treatment agent is used; The disadvantage is that the specific permselectivity tends to decrease relatively quickly.

However, if the treatment was carried out at too high a sieve temperature, the permeate concentration and am efficiency would be reduced by +'Y. A decrease in the degree of immersion in aS and a decrease in current efficiency are fatal defects, especially in the salt production process, and are problems that lead to increased costs.

On the other hand, in the case of non-explosion), sufficiently excellent specific permselectivity can be obtained even if the treatment is performed at a temperature close to room temperature or by treatment using a non-crosslinked treatment agent, and the effect However, according to MEJI4, these ion exchange membranes can easily have specific permselectivity. In addition, in terms of workability and energy savings in processing operations, this product can be said to be significantly lower than 11CM. These points are particularly excellent features of the present invention, and provide extremely advantageous conditions for the operation of electrodialysis.

Next, detailed examples of the present invention will be shown, but the present invention is not limited to these examples.

Explanations of symbols used in the examples and measurement methods are as follows.

(IIR; Electrical resistance value per ctIt of ion exchange resin membrane (Ω-all) Measurement method: After fully equilibrating the ion exchange resin membrane in 0.5N saline solution, alternating current in 0.5N saline solution Measurement was carried out for 1000 cycles at a temperature of 25°C.

(2) Fki; shows the specific permselectivity of magnesium ions to Na ions of the io/spalytic a+ lipid film.

However, N: Specified concentration of the relevant ion in the concentration chamber C: Specified concentration of the relevant ion in the dilution chamber Measurement force method: Silver-silver chloride electrodes are installed at both ends of the electrodialysis tank, and the concentration is measured from the anode side between the two electrodes. Each valid letter has 11 letters and 4 letters.
cm x 4 an ordinary anion exchange resin membrane, anion exchange resin membrane of the present invention, ordinary anion exchange resin membrane,
The electrodialysis cell is divided into five chambers: an anode chamber, a dilution chamber, a concentration chamber, a dilution chamber, and a cathode chamber by arranging ordinary cation exchange resin membranes.

The dilution chamber contains 0.3632 normal chlorine ions and 0 sulfate ions.
．． A mixed salt aqueous solution of 0.0368 normal, sodium ion normal, and calcium ion 0.0130 normal is added at a rate of 5 cm per second.
The concentration chamber was filled with the same mixed salt aqueous solution, and the anode and cathode chambers were filled with 0.4N saline solution, respectively, at a current density of 3.5N in a constant temperature bath at 25°C. 'Electrodialysis is carried out as 5A/-. After obtaining trace 11 for 4 hours, analyze the newly overflowing concentrated liquid and calculate the F average from the obtained concentrated liquid analysis value and the composition of the diluted liquid.

A large specific permselectivity of monovalent ions means a small FAN, and therefore, reducing F'A9 increases the specific permselectivity of monovalent ions.

Although the specific permselectivity of multivalent ions other than magnesium ions differs in absolute value, it is roughly proportional to the specific permselectivity of magnesium ions, so in the examples of this application, FAs are used to represent the specific permselectivity of multivalent ions. And so.

(3) Elongation: Based on the elongation without addition of organic matter during treatment, the percentage elongation is calculated.

Example 1/Comparative Example 1 99.5 parts of N-vinyl-2-methylimidazole, 0.5 part of divinylbenzene (purity 56%), 0.4 part of azobisisobutyronitrile and 400 parts of n-hexane 1. Melt at 60°C in a nitrogen-substituted angle.

Polymerize by heating for 20 hours. The obtained polymer was mixed with hexane,
After washing with tutanol, grind to 3 microns or less. This was mixed with a 20% by weight methyl chloride/n-hexane solution at 40°C.
After quaternization for 10 hours, filtration and drying were performed to obtain a selective treatment agent.

The following two types of treatment solutions were prepared using this selective treatment agent.

■ Processing liquid fil; 400mfit times 0.5N-
Kendaku in Na(j solution).

(2) Add dimethyl 7-talate to the treatment solution (1) according to the concentration of 19 & 7.

On the other hand, as a cation exchange side oil film, sulfonation of a styrene/vinylbenzene co-polymerized Asahi Kasei Asigrex produced from 1B was used with -101, and 9s'c,z was added to the above-mentioned treatment solution of Type 2a.

Soaked for an hour. After the treatment, the membrane was brought into contact with a large amount of salt water to remove organic matter in the membrane, and the physical properties and elongation upon treatment were measured by the method described above as follows.

Example 2/Comparative Example 2 A mixed solution of 1 part of α,α'-dichloromethaxylene, 3 parts of water, 0.25 parts of dimethylamine, and 0.1 part of caustic soda was added in a pressure-resistant container (nitrogen atmosphere, stirring). below) at 100℃
The quaternization reaction and polymerization are carried out for 60 minutes. The resulting viscous liquid is dropped into acetone to form a precipitate.

Filter this precipitate.

A processing agent was obtained by drying. The following two types of treatment solutions were prepared using this treatment agent.

(1) Treatment liquid (3): Dissolved in 1000 times the weight of water. (2) Treatment liquid (4); Benzyl alcohol was added to treatment liquid (3) to a concentration of 2%.

On the other hand, in a monomer mixture consisting of 23 parts of divinylbenzene (M degree 56%) * 77 parts of styrene, 40 parts of heptal dibutyl, and 0.2 parts of penzoyl oxide, a polypropylene product that had been previously irradiated with an electron beam was added. After soaking the plain woven fabric, it was sandwiched between two polyester sheets to prevent air from entering, and heated and polymerized to obtain a cation exchange membrane matrix. This cation exchange membrane matrix is sulfonated by circulating anhydrous sulfuric acid-dioxane adduct saturated dichloroethane solution at 5°C for 40 hours, and after removing the solution, an alkali-methanol solution is supplied at room temperature to replace the sulfonic acid groups of the membrane with Na type. death,
Further, equilibration was carried out with salt water to obtain a cation exchange side lipid membrane. This cation exchange side oil film was immersed in the treatment solution (3) and treatment solution (4) K and treated at 90° C. for 20 hours. After the treatment, the membrane was brought into contact with a large amount of salt water to remove organic matter in the membrane, and the physical properties and elongation during treatment were measured as follows.

Example 3/Comparative Example 3 The following two types of treatment liquids were prepared using polyethyleneimine as a selective treatment agent.

■ Processing solution (5; Processing agent 200 ppm concentration 0.1
Normalized Ca (Solution A) Treatment liquid (6); Kn-butanol is added to the treatment liquid (5) to a concentration of 5%.

A pre-treatment corner ion exchange resin membrane similar to that in Example (2) was immersed in the above two types of treatment solutions, and selective treatment was performed at 40° C. for 24 hours. After the treatment, the membrane was brought into contact with a large amount of salt water to remove organic matter in the membrane, and the physical properties and elongation upon treatment measured by the method described above were as follows.

Example 4 4-vinylpyridine was polymerized and quaternized to obtain a selective treatment agent.

On the other hand, cation exchange resin j! before the same selectivity treatment as in Example 2! Fy4 measurement Measurement direction:
nothing. The dilution chamber liquid contains the above selective treatment agent o, i% dioxane 5
% of the mixed salt aqueous solution added, and
Dialysis was performed for 10 hours at a flow of tA/dm. After treatment,
The treated membrane was removed from the dialysis tank and brought into contact with a large amount of salt water to remove organic matter from the membrane, and then measured. R211 was 2.1 Ω-1. Further, the elongation during treatment was 4% compared to Comparative Example 4, which will be described later.

Furthermore, the treated membrane was assembled in a pre-electrodialysis tank, and electricity was continued for 6 months under specific permselectivity measurement conditions. The Fgin measured during this period was initial (4th hour of energization) FMg = 0.06.

Final (after 6 months of 1 dL) FMp = 0.07.

Comparative Example 4 The same pre-treatment layer as in Example 4 was assembled in an electrodialysis tank, and a mixed salt water bath solution containing the same selective treatment agent as in Example 4 at 1% was passed through the dilution chamber. 10 at a current of IA/dm”
Power was on for an hour. Thereafter, the dilution chamber solution was replaced with a mixed salt water bath solution used for specific permselectivity, and the measured F-gin was 0.32.

Examples 5 to 8/Comparative Example 5 The same selective treatment agent as in Example 4 was dissolved in 500 times the amount of water,
Furthermore, a treatment solution of a mixed solution containing various organic substances shown in the table below was prepared. The same pre-selective treatment layer as in Example 1 was immersed in this treatment solution and treated at 60'C for 20 hours. After that, the membrane is brought into contact with a large amount of salt water to remove organic matter in the membrane.
The physical properties measured by the method described above and the elongation of the film during treatment were as follows.

(1-L Chokaidai) After measuring F of the above-mentioned treated membrane, electricity was continued under the specific permselectivity measurement conditions for another 6 months, and changes in FMg were observed. The FAN of the membrane (Comparative Example 5) increased in O and OS, and the increase in FQ+ of the membranes (Examples 5 to 8) treated with the treatment solution containing organic substances was within 0.01.

Example 9/Comparative Example 6 The following two types of treatment solutions were prepared using polydiallyldimethylammonium chloride as a selective treatment agent.

■ Processing liquid (7): Processing agent 0.5N N with a concentration of 0.5%
aα solution.

■ Treatment liquid (8): Benzyl ether is added to the treatment liquid (71) to a concentration of 2%.

A positive 1-one exchange resin membrane similar to that in Example 2 was immersed in the treatment solution of 28i above and treated at 80'C for 20 hours.

Thereafter, the membrane was encrusted with a large amount of salt water to remove organic matter in the membrane, and the physical properties measured by vkK and the elongation upon treatment were as follows.

Claims (1)

[Claims] (]) A method of bringing a cation exchange membrane into contact with a selective treatment agent, which is a polymer having an anion exchange group, to form a thin layer on the membrane surface that does not substantially increase the electrical resistance of the cation exchange membrane. 1. A selective treatment method using a cation exchange membrane, characterized in that during the treatment, the cation exchange membrane is impregnated with water other than a selective treatment agent, including a small amount of organic matter from the noodles.