JPS58156305A - Method for enhancing selective permeability of cation exchange membrane - Google Patents

Abstract

PURPOSE:To increase the selectivity of a cation exchange resin, by carrying out pretreatment wherein an electrodialysis cation membrane is exposed to a temp. higher than a temp. in use in the presence of a selectivity enhancer. CONSTITUTION:Prior to carrying out the electrodialysis of an electrolyte solution containing two or more cations with different valencies by using a cation exchange resin, the cation exchange resin is treated with a selectivity enhancer (e.g., amines, quaternary ammonium salt, heterocyclic amine, phosphonium salt, sulfonium salt, amine salt of a metal such as Co, Ni or Fe, cyano, amine complex or a chelate compound of Co, Ni, Mg or Ca) at a temp. higher than, usually, 5-30 deg.C higher than a temp. for several min - several hr to obtain enhancement effect in selective capacity and the durability thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for treating a cation exchange membrane. Specifically, the present invention relates to a selective treatment method of a cation exchange membrane for electrodialyzing an electrolyte solution containing two or more types of cations having different electric charges and selectively electrodialyzing cations having a lower electric charge.

Conventionally, in the production of salt by condensation of seawater using the ion exchange membrane method, cation exchange membranes have been used to
Liumium(Na) can be combined with other cations such as magnesium(Mo) and Na(C).
It is desired to produce 1&salt with high purity by selectively passing 1 through 1 with χ・1.Therefore, it is desired to produce 1&salt with high purity. Selective permselectivity of ions (hereinafter referred to simply as a method of creating a charged functional group, i.e., an anion-exchange III group) An electrically neutral thin layer on the surface of the Rolo cation-exchange membrane, i.e., a thin layer without ion-exchange groups (■) A method of forming a highly cross-linked layer on the surface of the cation exchange membrane; (■) A method of increasing the fixed ion concentration at least in the surface layer of the I1M! ion exchange membrane; (■) The above Any 2 of (I) to (W)
There are methods that use the above methods in combination. These are also classified as (a) a method of adsorbing a polymer substance, such as a polymer with a molecular weight of 100 to 19, preferably 500 or more, to the surface of a cation exchange membrane, and a method of crosslinking these by post-treatment. (b) A method of providing an anion exchange group through chemical bonding or a layer of nonionic atomic groups to the matrix constituting the cation/ion exchange membrane, (
e) Methods of chemically changing the surface layer of the cation exchange membrane can be divided into methods.

In this specification, a cation exchange membrane imparted with selective permeability in any of the methods exemplified above is referred to as a selective membrane. In addition, selective treatment means that the surface of the cation exchange membrane is coated with water for the purpose of imparting selective permeability. ! - means depositing a substance in an amount of 100 or more. Similarly, the selective treatment agent is a general term for agents used for selective treatment.

Therefore, not only the case where the culm is physically attached, but also the case where the culm is lightened and then crosslinked or modified by chemical means is included in the above definition.

The selectivity treatment of the present invention can be applied not only to cation exchange membranes that are not imparted with selectivity, but also to selective membranes; This has the advantage that it is possible to obtain selectivity that is even better than that known in the past, and that the durability of the selectivity is improved. Conventionally, as a method for obtaining a selective membrane, for example, in Japanese Patent Publication No. 4G-23607, a cation exchange membrane is treated with a water-soluble substance containing cations and has a molecular weight of 100 or more, or the method is to treat a cation exchange membrane with a water-soluble substance containing cations and have a molecular weight of 100 or more, or to apply it to a dialysate in electrodialysis. A method of adding such substances was published in the Japanese Patent Publication No. 47-38
In No. 01, a thin layer of a linear polymer electrolyte having an anion exchange group and a reactive functional group that can be easily crosslinked is adhered to the surface of a cation exchange membrane, and then a crosslinking treatment is performed. Japanese Patent Publication No. 53-44155 describes a method of fixing a cation exchange membrane as a thin layer that has a three-dimensional structure and does not substantially increase the electrical resistance of the cation exchange membrane. A method of treating a cation exchange membrane with a suspension of microparticles of crosslinked polymers has been proposed. The present invention can be effectively applied to selective membranes obtained by these methods.

In the present invention, prior to electrodialyzing an electrolyte solution containing two or more cations with different electric charges using a cation exchange membrane, the cation exchange membrane is subjected to cation exchange at a temperature higher than the temperature during electrodialysis. This is a method for improving the performance of selectively electrodialyzing cations with a small electric charge, which is characterized by subjecting a membrane to a selective treatment.

Further, the selective treatment agent used in the present invention is preferably a water-soluble substance having a functional group that becomes a cation in the electrolyte solution to be dialyzed and has a large molecular weight, and its structure and concentration are not particularly limited. For example, laurylamine, lauryltrimethylammonium chloride, triethanolamine monostearate, stearamideethyldiethylamine, 2-hebutadecenylhydroxyethylimidazoline, cetylpyridinium chloride, stearamidemethylpyridinium chloride, polyvinylpyridine,
4 such as polyvinylimidazole, polyethylene polyamine, polyethylene imine, poly-4-vinylpyridine, polyvinylbenzyltrimethylammonium, or
3@sulfurium salts such as phosphonium salts, Go, Ni, FE, etc. as metals, NH□ as ligands,
CN, N)1. C1-1,,CH NH! 4- or 6-coordination complex salts of positively charged transition metals such as Ll-lybrene athramine, tetraeprenepentamine, amino acids, and positively charged 5-coordinate compounds of ions, Co as a metal. , Ni, Mg
, Ca, etc. as a chelating agent (such as Naa occH), etc., but polyamines are preferable. The processing method is not particularly limited, but generally o, ooi to 1 g
A solution having a concentration of /Q is brought into contact with a cation exchange membrane.

In the present invention, the most important requirement is the temperature during the selection process. That is, it is essential that the temperature be higher than the temperature during electrodialysis, and the larger the temperature difference between the @ degree and the m degree during electrodialysis, the better the permselectivity will be. It must be kept within a range that does not cause deterioration of the ion exchange membrane used. Usually, the temperature is 5 to
Generally, the temperature is 30°C higher. As a means for this purpose, the solution containing the selective treatment agent is kept at a temperature higher than the temperature during electrodialysis and brought into contact with the cation exchange membrane, or the solution containing the selective treatment agent is kept at a temperature equal to or lower than the temperature during electrodialysis. After bringing it into contact with the solution containing 〇-〇-, the temperature may be raised to a higher temperature than during electrodialysis. In short, it is important to raise the temperature of the cation exchange membrane, on which the selective treatment agent is attached, for a certain period of time to a temperature higher than the temperature during electrodialysis. As another embodiment, it is also effective to heat the cation exchange membrane to which the selective treatment agent has been attached at a temperature higher than that during electrodialysis again to a temperature higher than that during electrodialysis.

Although the mechanism of the effect of such treatment is not clear,
The present inventors presume that the difference in expansion and contraction depending on the temperature of the ion exchange membrane acts effectively.

Further, the treatment time of the present invention varies depending on the type of cation exchange membrane used, the treatment temperature, the type of selective treatment agent, etc., but is usually preferably several hours to more than ten hours.

By using a cation exchange membrane treated according to the method of the present invention, it is possible to selectively electrodialyze cations with a small electric charge from an electrolyte solution containing two or more types of cations with different electric charges. It can be widely used for selective concentration and dilution of ions using ion exchange membranes.

Next, examples will be shown to specifically explain the present invention.
The present invention is not limited to these examples.

In addition, in the following examples, seawater concentration was performed by electrodialysis method,
The selective permselectivity between cations is determined by the value of the simple pure salt ratio ((C12-C
a-Mg)Nx 100/CJ (N)).

In electrodialysis, seawater is flowed at a flow rate of Gcm/sec into a dilution chamber in which 20 pairs of anionic and cationic ion exchange membranes are arranged.
A current is passed at a current density of 6 m2. The effective area of the membrane is 2
It is dm2. The liquid concentrated in each of the other compartments by electrodialysis was analyzed after its composition reached equilibrium to determine the simple pure salt percentage.

Example 1 The ion exchange membrane has already been used with new membranes Neo Hibuta CIM (Tokuyama Soda product name) and A-10KS (Tokuyama Soda product name).
A membrane that had been used to concentrate seawater for a year was used. Selective processing agents are
Dicyandiamide and formalin polycondensate were used.

For selective treatment, mix the selective treatment agent in water to 1100 pp, mix 5I2, and place it in an electrodialysis dilution chamber at 6 cm.
Pump circulation was carried out for 1 hour at a flow rate of /sec. Thereafter, the electrodialysis described above was performed. For selection, the treatment temperature, electrodialysis temperature, and simple pure salt rate are shown in Table 1.1 In the table, membranes used for 1 year refer to membranes that have been repeatedly selectively treated for 1 year of continuous use and selected after 1 year. This is the value at the time of conversion processing. The same applies to Tables 2 and 3. Note that No. 1 to No. 4 are comparative examples.

Table 1 9-Example 2 Selectivity treatment was carried out in the same manner as in Example 1 at 20°C for 6 seconds,
Electrodialysis was performed at 20°C for 5 hours (No, 1), then the same selection treatment as above was performed at 35°C for 2 hours, and then electrodialysis was performed at 20°C (NO, 2). The results are shown in Table 2.

Note that No. 001 is a comparative example.

10- Example 3 No. 17 of Example 1 and No. 1 and No. 2 of Example 2
The treated product was subjected to electrodialysis, and the changes in simple pure salt percentage over time are shown in Table 3. Note that No. 1 of Example 2 is a comparative example.

Table 3 The ion exchange membranes used were Neocepta CI+-457 (1i Yamasoda product name) and AFS-4T <a Sansoda product name). Moreover, polyethyleneimine was used as the selective treatment agent.

In the selective treatment, the selective treatment agent was added to water to a concentration of 150 ppm, mixed in 5Q, and then placed in an electrodialysis dilution chamber for 60 minutes.
The pump was circulated for 2 hours at a flow rate of cm2/sec. Thereafter, the selective treatment temperature, electrodialysis temperature, and simple pure salt rate at which electrodialysis was performed using the above-mentioned apparatus are shown in Table 4. Furthermore, NO, 1,
No. 2 is a comparative example.

Table 4 Example 5 Cation exchange membrane Neocepta CH-45T (manufactured by Tokuyama Soda Co., Ltd.) and anion exchange membrane Neoceptor AFS-4T (t!i
(manufactured by Sansoda Co., Ltd.) was used.

The selection treatment is carried out in accordance with (1), (2), and (3) below, and an aqueous solution containing a selective treatment agent is placed in an electrodialysis dilution chamber at 6 cm at 5°C.
The pump was circulated for 2 hours at a flow rate of % sec. After that, electrodialysis was performed using the above device. Table 5 shows the selective treatment temperature, electrodialysis temperature, and simple pure salt rate.

(1) Poly-4-vinylpyridine obtained by treating poly-4-vinylpyridine with a molecular weight of about 2000 with methyl iodide is dissolved in water to give a total of 4 green areas'i 1 +1100 pp.

(2) Dissolve polyvinylpencil 1-limeric ammonium with a molecular weight of about 1000 in water to make 5ooppll.
Dissolve in water to a concentration of 00 ppm.

13- Example 6 Neo Sebuta G H-45T (1! Yamashiro Ryosha Co., Ltd.) N, N'-
The sample was immersed in an aqueous solution of 500 ppm of di(vinylbenzyl)-N, N, N', N'-tetramethyl 1,6 hexenediammonium dichloride at 25° C. for 3 hours for 1 i.

Then, 11,000p of ammonium persulfate was added into the solution.
After 3 hours, it was taken out and washed with water to obtain a selective membrane. Using the selective membrane thus obtained and anion exchange membrane Neosepta AFS-4T (manufactured by Tokuyama Soda Co., Ltd.),
4- When seawater was electrodialyzed at 20°C, the simple pure salt rate was 95.5%.Subsequently, the selectivity treatment of the present invention was performed.

In the selection treatment, 5Q was prepared by adding polyethyleneimine as a selection treatment agent to water to a concentration of 50 ppn+, and the mixture was pumped and circulated in an electrodialysis dilution chamber at a flow rate of 6 cm 2 /sec for 2 hours. Table 6 shows the selective treatment temperature, electrodialysis temperature, and simple conversion rate. That is, the comparative example is a case where the selective treatment temperature and the electrodialysis temperature are the same.

15-

Claims (1)

[Claims] 1) A cation exchange membrane used for electrodialysis, which is characterized in that, prior to use, the cation exchange membrane is exposed to a concentration higher than the operating temperature in the presence of a selective treatment agent. Selective processing method