RU2554927C1 - Method of processing anion-exchange membrane ma-40 in hydrogen peroxide solution - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: in the method a dry anion-exchange membrane is exposed at room temperature in a 1-50% water solution of hydrogen peroxide for 1-14 days.

EFFECT: facilitation of the transfer of anions, containing compounds of hexavalent chromium, through the processed in such a way membrane under an influence of electric current, increase of the membrane service term with the preservation of its mechanical strength.

1 ex

Description

Usage: anion-exchange membrane brand MA-40, previously chemically treated in a solution of hydrogen peroxide, can be used in galvanic production in membrane electrolyzers designed to purify the wash water of trapping baths from chromate, dichromate and polychromatic ions by membrane electrolysis.

The invention relates to a method for the chemical treatment of an anion-exchange membrane of the MA-40 brand in a solution of hydrogen peroxide in order to facilitate migration (ion transfer by passing an electric current) through an anion-treated membrane containing hexavalent chromium compounds (chromate, dichromate and polychromatic anions) when the use of the treated membrane in membrane electrolyzers designed to purify the wash water of the capture baths from chromate, dichromate and polychromatic ions by membrane electrolysis .

The proposed method allows you to modify the anion-exchange membrane MA-40 by the chemical method so that migration through the treated membrane of anions containing hexavalent chromium compounds (chromate, dichromate and polychromatic anions) when passing an electric current is not accompanied by an increase in voltage across the electrolyzer of more than 12-16 V at a current density on the membrane of 2-4 A / DM ² .

The aim of the invention is to develop a method for modifying the MA-40 membrane, which facilitates the migration through the membrane of anions containing hexavalent chromium compounds (chromate, dichromate and polychromatic anions).

As an object of application of the invention taken anion-exchange membrane brand MA-40.

The inventive ion-exchange membranes are known from the prior art, their properties and processing methods of industrial ion-exchange membranes in order to increase their chemical resistance, selectivity, electrical conductivity, mechanical strength, etc. [1-4].

When using the MA-40 membrane to purify wash water from hexavalent chromium compounds by membrane electrolysis, the cleaning process stops because hexavalent chromium compounds oxidize the anion exchange resin to form poorly soluble polymer compounds that have low electrical conductivity and prevent the migration of hexavalent chromium compounds through the membrane.

To solve this problem, [5] proposed a method for treating the MA-40 anion-exchange membrane in a solution containing potassium or ammonium persulfate 50-70 g / l and sulfuric acid 50-70 g / l, which is the closest prototype.

The method proposed in [5] has a drawback, since a strong oxidizing agent and a strongly acidic medium are used, which can reduce the mechanical strength of a reinforcing fabric of organic material (kapron) and, as a result, reduce the life of the membrane as a whole.

The disadvantage of the prototype [5] is eliminated by using a weaker oxidizing agent — hydrogen peroxide solution — for processing the MA-40 membrane.

The absence of the addition of a strong mineral acid (sulfuric acid) severely limits the oxidizing properties of the hydrogen peroxide solution, which avoids the possible deterioration of the mechanical properties of the reinforcing fabric.

The use of a weaker oxidizing agent - a hydrogen peroxide solution - for treating the membrane requires more time to achieve the desired result - changing the chemical properties of the membrane, which facilitate the migration of anions containing hexavalent chromium compounds (chromate, dichromate and polychromat anions) through the membrane when passing electric current .

The method of processing the MA-40 membrane in a solution of hydrogen peroxide is as follows. A dry membrane is treated by immersion in a 1-50% aqueous solution of hydrogen peroxide, the process is carried out without heating. The solution is adjusted by adding the appropriate amount of hydrogen peroxide solution. Processing time from 1 to 14 days. The end of the treatment - the color of the membrane should be white or white-yellow. After processing, the membrane is washed with a large amount of cold tap water and stored under a layer of water.

Modification of the MA-40 anion-exchange membrane in a solution of hydrogen peroxide leads to the possibility of its long-term use in membrane electrolyzers designed to extract chromate and dichromate ions from the wash water of trapping baths.

The following is an example of the chemical treatment of the MA-40 anion exchange membrane in a hydrogen peroxide solution.

Example 1

The MA-40 dry anion exchange membrane is completely immersed, for example, in a 10% or 30% aqueous hydrogen peroxide solution at room temperature and left in this solution for 14 and 7 days, respectively. After this time, the color of the membrane should be white or white-yellow, which indicates the end of the chemical treatment. After that, the membrane is washed with a large amount of cold tap water and stored under a layer of water.

Information sources

1. Mazanko A.F., Kamaryan G.M., Romashin O.P. Industrial membrane electrolysis. - M .: Chemistry, 1989, p. 240.

2. Theoretical foundations and water conditioning technology. / Kulsky L.A. - 4th ed., Revised. and add. - Kiev: Science. Dumka, 1983, - p. 528.

3. A quick reference to chemistry. /Under. ed. O.D. Kurylenko. - 4th ed., Rev. and add. - Kiev: Naukova Dumka, 1974, - p. 991.

4. Zabolotsky V.I., Nikonenko V.V. The transfer of ions in the membranes. - M .: Nauka, 1996 .-- 392 p.

5. Turaev D.Yu. Method for modification of anion exchange membrane MA-40. Patent RU 2303835 C2 Russia. Declared 09/26/05. Published on July 27, 2007 Bull. No. 21.

Claims (1)

1. The method of chemical treatment of the anion-exchange membrane MA-40, designed to facilitate the transfer through it under the action of an electric current of anions containing hexavalent chromium compounds (chromate, dichromate and polychromatic anions), characterized in that the dry anion-exchange membrane MA-40 can withstand room temperature in a 1-50% aqueous solution of hydrogen peroxide for 1-14 days.