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 n 2– passive film. The chalcopyrite transpassive dissolution occurs above 700 mV.

Synthesis and stability of single-phase chalcopyrite – a potential reference material for key investigations in chemistry and metallurgical engineering

“…Subsequently, this should be compared to chalcopyrite which has been specifically doped with relevant trace elements such as silver, lead, indium or zinc. 18 …”

The Effects of Chloride on the High Temperature Pressure Oxidation of Chalcopyrite: Some Insights from Batch Tests—Part 2: Leach Residue Mineralogy

“…During low-temperature bioleaching of chalcopyrite, XANES and Raman spectroscopy suggested the formation of a "covellite-like" phase, although with crystallite size too small for XRD identification; there was no evidence for chalcocite formation even though the Eh was maintained at relatively low values of 350-480 mV [81]. The mixed potential provided by the Fe 2+ /Fe 3+ couple was also demonstrated by Yang et al [82] to facilitate chalcopyrite leaching via the formation of a chalcocite intermediate which it was claimed to be rapidly oxidised by Fe 3+ ions and hence not detected by XRD analysis or Raman spectroscopy. That chalcocite is not formed even in chloride-containing solutions at sufficiently high oxidation-reduction potential is consistent with various studies, e.g., [83]; Gao et al [84] noted that covellite is preferentially formed under oxidising conditions.…”