RU2303835C2 - Method for modifying anion-exchange membranes ma-40 - Google Patents

Abstract

FIELD: modifying electrodialysis plant membranes.

SUBSTANCE: proposed method for modifying anion-exchange membrane MA-40 involves treatment of the latter by dipping it in room-temperature aqueous solution of following composition, g/l: potassium or ammonium persulfate, 50 - 70; sulfuric acid, 50 - 70. Membrane treated in this way is used in membrane electrolyzer designed for extracting hexavalent chromium compounds (ion chromate and bichromate) from wash water filling intercepting bath.

EFFECT: improved exchange properties of membrane.

1 cl

Description

USAGE: in galvanic production for the extraction of chromate and dichromate ions from washing water, which enter there as a result of washing products with water after carrying out technological operations in baths containing solutions and electrolytes based on hexavalent chromium compounds: chromium plating, passivation, lightening, etching and etc. To prevent the entry of highly toxic hexavalent chromium compounds into wastewater and wash water, an electrolyzer is used (in which the cathode and cathode space are separated from the anode and the anode space using one or more ion-exchange (cationic and / or anion-exchange) membranes) installed directly into the non-flow washing bath (capture bath). With its help, while passing an electric current, hexavalent chromium compounds (chromate and dichromate ions) are removed from the wash water, migrating through the MA-40 modified anion exchange membrane into the anode space, where they accumulate.

SUMMARY OF THE INVENTION: methods are known from the prior art for processing (modifying) industrial ion-exchange membranes in order to improve their properties [1-2].

The modification method of the MA-40 anion exchange membrane is that a dry membrane is treated by immersion in an aqueous solution of the composition: potassium or ammonium persulfate 50-70 g / l and sulfuric acid 50-70 g / l, the process is carried out without heating. The adjustment of the solution is carried out mainly by adding the appropriate amount of potassium or ammonium persulfate. Processing time from 1 to 7 days. The end of the treatment - the color of the membrane should be white or slightly yellow. After processing, the membrane is washed with a large amount of cold tap water and stored under a layer of water.

The MA-40 membrane cannot be used in a membrane electrolyzer designed to extract chromate and dichromate ions from trapping baths, due to the strong adsorption and absorption of chromate and dichromate ions. An increase in the concentration of chromate and dichromate ions inside the membrane leads to their chemical interaction with the anion-exchange resin with the formation of gummy reaction products with high electrical resistance and blocking the passage of chromate and dichromate ions through the membrane.

Modification of the MA-40 anion exchange membrane in a solution containing persulfate anions leads to the possibility of its long-term, permanent use as an anion exchange membrane in membrane electrolyzers, in particular, in a two-chamber membrane electrolyzer designed to extract chromate and dichromate ions from wash water from capture baths. When the current density on the membrane is 0.04 A / cm ^{2, the} voltage on the electrolyzer is not more than 12-16 V. Using the modified MA-40 anion-exchange membrane allows you to get a solution containing hexavalent chromium compounds in a concentration of up to 50 g / l in terms of chromic anhydride. The resulting solution is used to adjust working, technological solutions and electrolytes.

The INVENTION relates to a method of modifying the MA-40 anion exchange membrane known in the art [3-5] in order to give it the necessary properties that facilitate the migration of chromate and dichromate ions.

The OBJECT of the INVENTION is to develop a method for processing an anion exchange membrane in order to give it the necessary properties that facilitate the migration of chromate and dichromate ions.

Processing the MA-40 membrane makes it possible to use it in a membrane electrolyzer to extract chromate and dichromate ions from the wash water from the capture bath (non-continuous wash bath). Processing leads to a significant decrease in the required voltage on the cell with increasing current density across the membrane.

Information sources

1. Applied electrochemistry. / Ed. Doctor of Technical Sciences, prof. A.P. Tomilova. - 3rd ed., Revised. - M .: Chemistry, 1984, 520 p.

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

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

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

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

Claims (1)

The method of modifying the anion-exchange membrane MA-40, characterized in that the anion-exchange membrane MA-40 is treated by immersion in an aqueous solution of the composition: potassium or ammonium persulfate 50-70 g / l and sulfuric acid 50-70 g / l, the process is carried out without heating, processing time from 1 to 7 days.