Electrochemical characteristic analysis for surface passivation layer of galena and chalcopyrite in acid corrosion

Abstract

The surface passivation layer of galena and chalcopyrite after sulfuric acid corrosion can enlarge the difference in their floatability. The floatability test shows that sulfuric acid corrosion strongly inhibits galena’s floatability but has no effect on chalcopyrite. Scanning electron microscope and energy dispersive spectrometer (SEM-EDS), X-ray photoelectron spectroscopy (XPS) and Eh-pH diagram analysis showed that the galena surface was oxidized to form a coarse passivation layer of PbSO4, while the chalcopyrite surface dissolved only a small amount of Fe2+ ions and formed a dense sulfide layer (Cu(1-x)Fe(1-y)S2). Open circuit potential (OCP), polarization curve, and electrochemical impedance spectroscopy (EIS) were used to investigate the electrochemical characteristics of the surface passivation layer on galena and chalcopyrite after sulfuric acid corrosion. The electrochemical analysis results showed that the electrostatic potential increased and the electrochemical activity decreased on the galena and chalcopyrite surface due to corrosion action; the current density of corroded galena was stable around 17.41 μA·cm−2 and the surface oxidation reaction can be further carried out, while the current density of corroded chalcopyrite was reduced from 17.91μA·cm−2 to 9.01 μA·cm−2, and the surface reaction was gradually inhibited; the double electric layer resistance (Rt) and the resistance (Rp) for the passivation layer of corroded galena both decreased significantly, and the passivation layer could be further generated from the surface to the interior, while the Rt and Rp of corroded chalcopyrite increased significantly and prevented the dissolution of internal components. The electrochemical analysis results were consistent with each other and confirmed by SEM-EDS and XPS conclusion. In addition, the corrosion-flotation process has been used to achieve high-efficiency separation of the galena-chalcopyrite mixture.