Redox Behavior of Chalcopyrite

Abstract

Electrochemistry of chalcopyrite was investigated using cyclic voltammetry technique at four different pH values. The voltammetry experiments were performed at different anodic switching potentials and scan rates to elucidate the state of reversibility and the kinetics of the electrochemical reactions. The results revealed that oxidation-reduction reactions at chalcopyrite surface were not fully reversible due to irreversible coverage of the surface by iron-hydroxides and/or diffusion of metal ions into solution. The most complicated electrochemical behavior was observed in neutral solution. Most of the elemental sulfur was reduced to H2S/HSform at strongly reducing environment. The difference in the kinetics of the anodic and the cathodic reactions was considered as the main reason for this kind of irreversibility. However, the reactions at alkaline pH values were quite clear and have higher degree of reversibility. This was presumably due to stability of the elemental sulfur in the scanning range applied. Most of the elemental sulfur formed during anodic oxidation was involved in reformation of chalcopyrite surface since its reduction potential to HS- form in alkaline solutions is very low and out of the scanning range applied in this study