Anodic electrochemistry of chalcopyrite

Abstract

The anodic behaviour of chalcopyrite in 1 M H2SO4 and 1 M HCl was studied by linear sweep voltammetry and potentiostatic electrolysis. Voltammograms with a fresh surface showed a small prewave, attributed to a surface oxidation process, followed by a region of active dissolution characterized by a steeply rising anodic current. At still higher potentials the behaviour differed in the two electrolytes, but, contrary to a previous report, there was no evidence of a photosensitive limiting current. Anodic characteristics of chalcopyrite specimens from different sources, including synthetic material, were similar. The anode reaction was found to involve 6·7±0·3 F per mole of chalcopyrite, from which it was calculated that 86% of the sulphide sulphur was oxidized to the elemental form (some of which was plastic sulphur) and 14% to sulphate. The surfaces of oxidized electrodes were examined and photographed after varying periods of potentiostatic electrolysis. Chalcopyrite dissolution occurred at localized sites, the number of which depended strongly on potential. Current-voltage and potentiostatic current-time curves were interpreted in terms of the kinetics of nucleation, growth and overlap of these discrete corrosion centres.