The Processing of Titanium Production Effluents in an Electrodialysis Cell with Monopolar and Bipolar Membranes

Abstract

Results of research on the processing of spent acid etching solution (SAES) produced during manufacturing of titanium products by their etching in hydrochloric acid are presented in this paper. The processing technology consists of neutralizing SAES with alkali, filtering, drying and calcining of titanium hydroxide precipitate, and also processing of filtrate by electrodialysis in a cell with ion-exchange membranes. Anion-, cation- and bipolar ion exchange membranes were used. It is shown that the processing of SAES formed during etching of titanium products makes it possible to purify effluents to remove NaCl in an electrodialysis cell with monopolar and bipolar membranes. Transfer of Na⁺ and Cl^– ions through the bipolar membrane MB-1 was observed. Thus, solutions generated in acid and alkali concentration chambers contain significant amounts of NaCl. It is obvious that the introduction of buffer chambers is necessary to obtain acid and alkali solutions free from NaCl when using bipolar membranes.