Abstract:The electrochemical oxidation behavior of pyrite in bioleaching system of Acidthiobacillus ferrooxidans was investigated by cyclic voltammetry (CV), polarization curve and electrochemical impedance spectroscopy (EIS). The results show that in the presence or absence of A. ferrooxidans, the oxidation reaction of pyrite is divided into two steps: the first reaction step involves the oxidation of pyrite to S, and the second reaction step is the oxidation of S to SO₄²⁻. The oxidation mechanism of pyrite is not changed in the presence of A. ferrooxidans, but the oxidation rate of pyrite is accelerated. With the extension of reaction time of A. ferrooxidan with pyrite, the polarization current density of pyrite increases and the breakdown potential at which the passive film dissolves decreases. The impedance in the presence of A. ferrooxidans is obviously lower than that in the absence of A. ferrooxidans, further indicating that microorganism accelerates the corrosion process of pyrite.

Key words: pyrite; bioleaching; A. ferrooxidans; electrochemistry