Electrochemical oxidation of pyrrhotute in aqueous solution

The anodic surface oxidation of natural pyrrhotite in 0.3 mol/L KCI and HCI solution (pH 4.0) and 0.1 mol/L Na2B4O7 solution (pH 9.18) respectively was investigated by using cyclic voltammetry, Tafel plot, and chronoamperometry. In 0.3 mol/L KCI and HCO solution (pH 4.0), at potential less than 0.5 V(vs SHE), the production of anodic oxidation on pyrrhotite surface can not maintain a stable phase to form a passive film. In 0.1 mol/L Na2B4O7 solution (pH 9.18), when the electrode potential increases to more than 0.5 V (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 (J(0)) is 5.34 mu A/cm(2), which is also the exchange current density of the oxidation reaction on pyrrhotite electrode surface in 0.1 mol/L Na2B4O7 solution (pH 9.18). The electrochemical dynamics equation of the oxidation was determined.