Electrodialytic Extraction of Zinc(II) by Liquid Membranes Based on Di(2-ethylhexyl)phosphoric Acid

A new process of extraction of zinc(II) ions with the use of liquid membranes under the conditions of galvanostatic electrodialysis with metal electrodeposition in the catholyte is presented. Liquid membranes represent solutions of di(2-ethylhexyl)phosphoric acid with addition of tri-n-octylamine in 1,2-dichloroethane. The effect of the electrodialysis current density and the composition of aqueous solutions and organic membranes on the rates of extraction, transmembrane transfer of metal ions, and electrodeposition of metal is studied. Fine-crystalline cathodic deposits of zinc are obtained from solutions of hydrochloric, sulfuric, perchloric, and acetic acids. It is shown that in the process under study, the virtually complete (>99.9%) extraction of zinc(II) ions by liquid membranes from their original solution containing 0.01 M ZnSO4 is achieved after 1-2.5 h of electrodialysis. The maximum degree of metal re-extraction is 98% and the degree of electrodeposition is 78%. It is shown that the shape of chronopotentiograms can serve as a criterion of completeness of zinc(II) extraction from the original solution.