New insights on the role of lattice-substituted silver in catalytic oxidation of chalcopyrite

Abstract

The present study investigates, for the first time, the effect of Ag doping on chalcopyrite oxidation. Oxidation kinetics were studied by comparing the electrochemical oxidation of synthetic pure and Ag-doped (8 ppm Ag) chalcopyrite in sulfuric acid solutions without and with Fe3+. Results showed that Ag doping increased the chalcopyrite oxidation rate by 56% (0.62 × 10−6 to 0.97 × 10−6 A/cm2) and 177% (0.97 × 10−6 to 2.69 × 10−6 A/cm2) in sulfuric acid solutions without and with Fe3+, respectively. Anodic polarization tests displayed three peaks corresponding to different active-passive behaviors during chalcopyrite oxidation. The first peak between the open circuit potential to 0.65 V was associated with Ag: it presented a peak current density of 10 × 10−6 and 80 × 10−6 A/cm2 for pure and Ag-doped chalcopyrite, respectively. Electrochemical impedance spectroscopy demonstrated that charge transfer resistance and passive layer resistance decreased when Ag was present in the chalcopyrite lattice.