Application of bipolar electrodialysis to the recovery of acids双极膜电渗析回收酸.pdf

DESALINATION ELSEVIER Desalination 169 (2004) 11-20 /lecate/desai Application of bipolar electrodialysis to the recovery of acids and bases from water solutions J. Wi~niewski, G. Wigniewska*, T. Winnicki Institute ofEnvironment Protection Engineering, Wroclaw Universityof Technology, Wyb. Wyspiacbkiego27, 50-370 WroeIaw,Poland Tel. +48 (71) 320-3225; Fax +48 (71) 328-2980; email:gwisniewska@iios.pwr.wroe.pl Received 3 December 2002; accepted 15 October 2003 Abstract The studies of acid purification and base purification via bipolar electrodiaiysis are presented. The process of acid recovery involved spent solutions of acid (HC1 or H2SO4) and iron salt obtained in the course of conventional electrodialysis. Bipolar electrodialysis yielded an acid solution concentrated 51-fold (in the case of hydrochloric acid) and 63-fold (in the case of sulphuric acid) as compared to the feeding solution for conventional electrodialysis. The solution of the recovered acid was only slightly contaminated with iron salt (0.12 and 0.13%). The process of base purification yielded an NaOH solution concentrated nine-fold as compared to the feeding solution for the bipolar electrodialysis process. The contamination of the recovered base varied from 1.75 to 2.50%, Keywords: Bipolar electrodialysis; Acid recovery; Base recovery 1. Introduction anion-exchange layer facing the anode and the Unlike monopolar electrodialysis, the