The influence of applied potentials and temperature on the electrochemical response of chalcopyrite during bacterial leaching

Electrochemical techniques were conducted to clarify the role of solution potential and temperature under a variety of experimental conditions similar to those found during the mesophilic and thermophilic biooxidation of chalcopyrite (CuFeS2). Despite a large number of publications dealing with the bacterial leaching of CuFeS2, three central aspects remain unclear: How to dissolve preferentially copper from CuFeS2, the effect of temperature on the extent of CuFeS2 passivation, and the behavior of ferric ions on a polarized CuFeS2 surface. Anodic characteristics showed that CuFeS2 passivation was more severe in the potential range 0.45–0.65 V saturated calomel electrode at 25 °C. However, there was no evidence of CuFeS2 passivation at higher temperatures (45 and 65 °C). Cu was preferentially dissolved from CuFeS2 at lower potentials and high temperatures at a ratio copper to iron of about 3:2. Cathodic characteristics showed that the ferric ions inhibited the leaching process when the CuFeS2 surface was polarized at high potentials and low temperatures.