Co-Bioleaching of Chalcopyrite and Silver-Bearing Bornite in a Mixed Moderately Thermophilic Culture

Chalcopyrite and bornite are two important copper minerals, and they often coexist. In this study, the co-bioleaching of chalcopyrite and silver-bearing bornite by mixed moderately thermophilic culture at 50 degrees C was investigated. The bioleaching results show that the extraction percentage of Cu for co-bioleaching of chalcopyrite (Ccp) and silver-bearing bornite (Bn) (Ccp/Bn = 3:1) was 94.6%. Compared to bioleaching of chalcopyrite or silver-bearing bornite alone, the Cu extraction percentage was greatly enhanced when they were bioleached together. The leaching residues were characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Silver-bearing bornite dissolved preferentially compared to chalcopyrite, due to galvanic interactions. Simultaneously, Ag+ was released from the silver-bearing bornite into solution. Ag2S formed on the surface because Cu and Fe in the chalcopyrite were replaced by Ag+, accelerating chalcopyrite dissolution and enrichment of Ag on the surface of the chalcopyrite.