FUNDAMENTAL-STUDIES ON CHLORINE BEHAVIOR AS RELATED TO ZINC ELECTROWINNING FROM AQUEOUS CHLORIDE ELECTROLYTES

Measurements were made on the transport and equilibrium properties of dissolved chlorine in aqueous HC1, HCl-ZnCl2, HCl-MgCl2, and water. These measurements included solubility, absorption rates during bubbling, stripping rates during nitrogen bubbling, and cathodic reduction rates. The solubility of chlorine was found to be affected by speciation into aqueous Cl2, HC1O, and C13 -. With increasing HCl concentration, the solubility of chlorine decreased to a minimum at 0.2 mol dm-3, followed by a slow and linear increase. Metal chloride salts depressed the chlorine solubility approximately in proportion to concentration. Mass transfer of aqueous chlorine was found to support a current of about 100 A m-2 from a chlorine-saturated ZnCl2-HCl solution under typical zinc electrowinning conditions. Comparisons with published zinc electrowinning papers indicate that air sparging would eliminate dissolved chlorine sufficiently to remove the need for diaphragm cell separation of dissolved chlorine, insofar as current inefficiencies due to cathodic chlorine reduction are concerned. © 1990 The Minerals, Metals & Material Society.