Electrochemical studies on dissolution and passivation behavior of low temperature bioleaching of chalcopyrite by Acidithiobacillus ferrivorans YL15

Abstract

Bioleaching has been widely applied to recover metals from sulfide minerals at medium or high temperatures, however, little is known about the bioleaching at low temperature. Electrochemical analysis techniques such as cyclic voltammetry (CV), potentiodynamic polarization curve and electrochemical impedance spectroscopy (EIS), combined with surface detection methods such as scanning electron microscopy (SEM), applied to study the electrochemical behavior of chalcopyrite during bioleaching at 6 °C. Chalcopyrite bioleaching experiments demonstrated that the maximum cell density could achieve 5.3 × 108 cells/mL. Copper extraction by Acidithiobacillus ferrivorans could reach 1.92 g/L, which is better than the 0.67 g/L of sterile experiment. CV tests found that as the leaching time passed, the anodic and cathodic current signals decreased and the anodic peak moved gradually from low potential to high potential. The increase of corrosion potential and the decrease of corrosion current in potentiodynamic polarization proved the passivation on the surface of the chalcopyrite. EIS results showed that ion exchange resistance increased from 306.1 Ω to 1913.0 Ω, which is larger than the passivation film impedance originated from elemental sulfur and polysulfide on the mineral surface. It suggested that the impedance of chalcopyrite electrode at low temperature is mainly due to ion exchange impedance but not passivation layer, which is different from the bioleaching at normal or high temperature.