BEHAVIOR OF ANTIMONY(III) DURING COPPER ELECTROWINNING IN CHLORIDE SOLUTIONS

Contamination of cathodic copper by Sb during electrowinning in chlori de solutions is a surface phenomenon. A digitized scanning electron mi croscopy (SEM) micrograph indicates that the Sb is concentrated on the surface of the cathode. Energy-dispersive X-ray (EDX) analysis reveal s that the Sb-containing layer is a complex salt of Cu, Sb, Cl, and O. Electrochemical measurements show that the adsorption of Sb or Cu spe cies decreases with the increase of acidity of the solution when the s olution contains antimony chloride or cuprous chloride. The adsorption increases with the increase of the acidity when the solution contains both Sb and Cu. The discharge of cuprous ions in the adsorbed complex salt releases antimonious ions and then forms a new layer Of the comp lex salt with cuprous ions from the solution. This newly formed comple x salt is readsorbed on the surface of the cathode. Thus, Sb concentra tes on the surface of the cathode instead of being evenly distributed throughout the copper product. This suggested mechanism also explains the fact that the presence of Sb in the electrolyte enhances the elect rodeposition of Cu.