In Situ Electrochemical Investigation of Acidic Pressure Oxidation of Pyrite at 160–240°C

In situ electrochemical studies on the oxidation behavior of pyrite in 0.1 M H2SO4 solution in the temperature range of 160 to 240 degrees C were performed by measurements of electrochemical impedance spectroscopy (EIS), linear polarization, potentiodynamic polarization and potentiostatic polarization. Results showed that with the increase of temperature, the anodic current density increased, while the corrosion potential (E-corr), polarization resistance, charge transfer resistance (R-ct) and pore resistance (R-pore) decreased. The change of these electrochemical parameters indicated that the increase of temperature promoted the dissolution of pyrite by accelerating the electrochemical step and weakening of the porous passive film. EIS studies with different applied potentials at 240 degrees C revealed that both Rct and Rpore decreased with increasing applied potential. As the potential increased to 400 mV, the time constant relating to the porous passive film disappeared. These changes demonstrated that sulfur yield was dependent on the potential, and the sulfur yield approached zero at 400 mV at the temperature of 240 degrees C. The values of Ea indicated that pyrite oxidation kinetics were limited by the rate of electrochemical reaction.