A Study on The Electrochemical Oxidation Mechanism of Pyrite in NaCl Solutions with Different pH Values

The study on the surface oxidation mechanism of pyrite has always been a research hot topic in the field of environmental pollution control in mining areas and the flotation process of pyrite. In this article, by using some electrochemical testing techniques such as the open circuit potential measurement, electrochemical impedance spectroscopy, polarization curve method, and cyclic voltammetry, we have researched the effect of pH values of various solutions on the electrochemical oxidative dissolution behavior of pyrite in the sodium chloride solution system. The experimental results show that with the increase of pH values of solutions, the passive film resistance of pyrite surface increases, while the charge transfer resistance decreases, resulting in the minimum value of total resistance at the pH value of 7 for the NaCl solution. The anodic polarization slope, cathodic polarization slope, and corrosion electric current density are all increased at first and then decreased with the increase of pH values of solutions, leading to their maximum values at the pH value of 7 for the NaCl solution. These indicate that when the pH value of NaCl solution is 7, the oxidative dissolution process of pyrite is promotedas the dissolution rate of pyrite is the highest. With the increase of pH values of solutions, the passive film formed on the pyrite surface becomes thicker and denser. The passive films on the pyrite surface formed in the acidic solutions are mainly composed of elemental sulfur, while those formed in the alkaline solutions are mainly composed of iron hydroxides.