Abstract: The anodic surface oxidation of natural pyrrhotite in 0.3mol/L KCl and HCl solution (pH 4.0) and 0.1mol/L Na₂B₄O₇ solution (pH 9.18) respectively was investigated by using cyclic voltammetry, Tafel plot, and chronoamperometry. In 0.3mol/L KCl and HCl solution (pH 4.0), at potential less than 0.5V(vs SHE), the production of anodic oxidation on pyrrhotite surface can not maintain a stable phase to form a passive film. In 0.1mol/L Na₂B₄O₇ solution (pH 9.18), when the electrode potential increases to more than 0.5V (vs SHE), part of S is oxidized to sulfate, making the passive film somewhat porous, but elemental S and metal oxidates Fe(OH)₃ still remain on the electrode surface, and the passive film can not be broken down totally. According to PARCalc Tafel analysis, the corresponding corrosion current density (J₀) is 5.34μA/cm2, which is also the exchange current density of the oxidation reaction on pyrrhotite electrode surface in 0.1mol/L Na₂B₄O₇ solution (pH 9.18). The electrochemical dynamics equation of the oxidation was determined.

Key words:  pyrrhotite; electrochemical oxidation; aqueous solution; electrochemistry