Removal of chromium(VI) from aqueous solutions using a novel hybrid liquid membrane—electrodialysis process

Abstract

Chromium(VI) is one of the most toxic metals, and the removal of this metal ion from effluents and waste waters is a problem of great significance. A novel hybrid process of electrodialysis and liquid membrane extraction is proposed for chromium(VI) removal from aqueous solutions. Transport through bulk liquid membranes was found to be effective for chromium(VI) anions removal from chloride acidic solutions during galvanostatic electrodialysis. Solutions of tri-n-octylamine with admixtures of di(2-ethylhexyl) phosphoric acid in 1,2-dichloroethane were used as the liquid membranes. Effects of current density, chromium(VI) and hydrochloric acid concentration in the feed solution, carrier and admixture concentration in the liquid membrane were studied, and optimal conditions were determined. It is demonstrated that a practically complete removal of chromium(VI) from the feed solution is achieved during 1.0–4.0h of electrodialysis. A maximal stripping degree of ∼90% is obtained under the optimal conditions. A possibility of effective single-stage removal of chromium(VI) into dilute solutions of hydrochloric, sulphuric, perchloric, phosphoric acids and water is demonstrated.