Membrane Extraction of Chromium(VI) by Tri-n-Octylamine during Electrodialysis

Abstract

A new process for chromium(VI) removal from aqueous solutions is presented. The process includes the transport of chromium(VI) anionic complexes from chloride acidic solutions through bulk liquid membranes at galvanostatic electrodialysis. Solutions of tri-n-octylamine with admixtures of di(2-ethylhexyl)phosphoric acid in 1,2-dichloroethane have been used as the liquid membranes. Effects of current density, chromium(VI) and acid concentration in the feed solution, carrier and admixture concentration in the liquid membrane,  type of acid in the stripping solution are studied, and optimum conditions are determined. Practically complete removal of chromium(VI) from the feed solution containing 0.01 mol/L  K 2 Cr 2 O 7 is achieved during 1.0 − 4.0 hours of electrodialysis. Maximum stripping degree of ~ 90 % is obtained under optimum conditions. A possibility of effective single-stage removal of chromium(VI) into dilute solutions of hydrochloric, sulphuric, perchloric, phosphoric acids and water is demonstrated.