Mixed Potential Plays a Key Role in Leaching of Chalcopyrite: Experimental and Theoretical Analysis

Abstract

The mixed potential plays a key role in leaching of chalcopyrite. Therefore, the impact of Fe²⁺ and Fe³⁺ on chalcopyrite leaching was investigated in this work. Simultaneously, the chalcopyrite passive film was studied by applying cyclic voltammetry (CV), potentiodynamic, potentiostatic, and Tafel polarization. X-ray photoelectron spectroscopy (XPS) was used to analyze the products formed during the electrochemical treatment of chalcopyrite. Furthermore, the band theory was used to analyze the oxidation and reduction of chalcopyrite. High copper extraction percentage was obtained at a low mixed potential or ratio of Fe³⁺/Fe²⁺. The empty states of chalcopyrite overlapped with filled states of Fe²⁺; chalcopyrite captured electrons from Fe²⁺ and was reduced to chalcocite, which was very easily oxidized by Fe³⁺. The Fe dissolves preferentially from the chalcopyrite surface in the potential range from 475 to 700 mV and leave behind a S₂^2– and S_<i>n</i>^2– passive film. The chalcopyrite transpassive dissolution occurs above 700 mV