Separation of cobalt(II) from nickel(II) by a hybrid liquid membrane–electrodialysis process using anion exchange carriers

Abstract

Cobalt and nickel are widely used in various branches of industry, are usually present together in industrial and waste solutions and have similar physical and chemical properties; therefore, the separation of the metals is an important practical problem. A hybrid process based on the bulk liquid membrane is proposed as a novel method for the selective separation of cobalt(II) from nickel(II). The process includes the transport of cobalt(II) anionic chlorocomplexes from 3 to 6mol/L HCl solutions through the liquid membranes containing tri-n-octylamine or trialkylbenzylammonium chloride in 1,2-dichloroethane during galvanostatic electrodialysis. A possibility of cobalt(II) transfer into dilute solutions of sulfuric, hydrochloric, nitric and perchloric acids accompanied by an effective separation from nickel(II) is demonstrated. Effects of the main electrodialysis parameters as well as of the composition of the liquid membranes, feed and strip aqueous solutions on the rate and selectivity of the cobalt(II) transport are studied, and optimum conditions are determined. It is shown that the rate of cobalt(II) transport increases with the increase in current density, hydrochloric acid and cobalt(II) initial concentration in the feed solution. The selectivity of the metal separation increases as the cobalt(II) or nickel(II) concentration in the initial mixture increases.