Mesophilic inoculation enhances primary and secondary copper sulfide bioleaching altering the microbial & mineralogical ore dynamics

Bioleaching involves a chemical-microbial-driven dynamic process of oxidation and dissolution, as well as formation of surface secondary phases that change the copper sulfide exposure/occlusion profiles. This dynamic process determines the kinetics of copper sulfides bioleaching. Former studies have shown the microbiological dynamics of bioleaching solutions, but few have focused attention at the ore surface, while most mineralogical studies have been done with pure copper sulfide species under controlled conditions. In this work we aim to unravel the link between the microbiology and the mineralogy during bioleaching, and to determine the effect of mesophilic inoculation of a mainly primary copper sulfide ore. State of art molecular microbial community analysis showed that microbial dynamics in the leaching solutions is not representative of the bioleaching process since it differs significantly from the one established at the ore surface. Moreover, a single mesophilic inoculation permanently alters the microbial dynamics, both in the leachate and the ore surface, generating a major and fast alteration of the primary copper sulfide minerals chalcopyrite (CuFeS2) and bornite (Cu5FeS4), as well as the transient formation of covellite (CuS), which was the unique secondary phase detected by advanced mineralogical analysis. Overall, mesophilic inoculation significantly enhanced copper recovery from a low-grade primary copper sulfide ore by means of alteration of the microbial and mineralogical dynamics.