Electrochemical behaviour of massive chalcopyrite electrodes bioleached by moderately thermophilic microorganisms at 48 °c

A mixed culture of moderately thermophilic microorganisms was used to bioleach chalcopyrite at 48 °C, and it showed good performance in copper extraction. The electrochemical response of massive chalcopyrite electrodes bioleached for various periods up to 20 days was studied using cyclic voltametry. The results showed that as bioleaching progressed, the anodic and cathodic current signals decreased and the anodic peak moved gradually from low potential to high potential. Furthermore, the oxidation peak of chalcopyrite disappeared at a late stage of bioleaching, while the oxidation peak of intermediate species (Cu x S (1 < × < 2)) existed throughout the whole bioleaching process. The results of SEM/EDX analysis of the electrodes indicate that at the end of bioleaching, the surface of chalcopyrite was covered with extracellular polymeric substances (EPS) and jarosite, indicating that these are the major components of a passivation layer that blocks continuous copper extraction.