Special Features of Electro-Membrane Recovery of Acids and Alkalis from the Water-Soluble Wastes of Nuclear Power Plants

The results of studying of the nitric acid and NaOH + KOH alkalis' mixture recovery from concentrated solutions in filter-press-type electrodialyzers with anion-exchange, cation-exchange, and bipolar membranes are presented. The necessity of the technological solutions preliminary purification from calcium and boron compounds was established, in order to obtain crystalline boric acid (H3BO3) and gypsum (CaSO4 center dot 2H(2)O). The possibility of obtaining, from purified concentrated salt solutions, acids and alkalis with a concentration of similar to 300-600 g/L suitable for reuse is shown. This can be provided only by the electrodialysis with anion- and cation-exchange membranes, while electrodialysis with bipolar membranes is complicated by noticeable contamination of both acidic and alkaline solutions with salts.

Automated summary

The results of studying the recovery of nitric acid and NaOH + KOH alkalis' mixture from concentrated solutions using filter-press-type electrodialyzers with anion-exchange, cation-exchange, and bipolar membranes are presented. It was found that the preliminary purification of the solutions from calcium and boron compounds is necessary to obtain crystalline boric acid and gypsum. The study demonstrates the possibility of obtaining purified acids and alkalis suitable for reuse from concentrated salt solutions. Electrodialysis with anion- and cation-exchange membranes is the most effective method, while electrodialysis with bipolar membranes leads to noticeable contamination of the solutions with salts.