Influence of ferric iron on the electrochemical behavior of pyrite

The electrochemical behavior of a pyrite electrode in a sulfuric acid solution with different concentrations of ferric iron (Fe3+) was investigated using electrochemical techniques including measurements of open circuit potential, cyclic voltammetry, Tafel polarization curves and electrochemical impedance spectroscopy (EIS). The results show that the pyrite oxidation process takes place via a two-step reaction at the interface of the pyrite electrode and the electrolyte, and that a passivation film composed of elemental sulfur, polysulfides, and metal-deficient sulfide is formed during the process of the first-step reaction. Ferric iron plays an important role in the dissolution of pyrite by enhancing the direct oxidation. The Tafel polarization curves indicate that the polarization current of the pyrite electrode increases with an increase in Fe3+ concentration. It has also been shown that the higher concentration of Fe3+, the more easily the pyrite can be transformed into the passivation region. Moreover, the EIS response is found to be sensitive to changes in Fe3+ concentration.