Influence of ore grade and mineral medium on chalcopyrite bioleaching with mixed microbial consortia

Abstract

In the present work, key parameters in copper bioleaching from chalcopyrite have been investigated at long-term operation. In detail, the type of mixed microbial consortium (origin and adaptation); the composition of two mineral media (the growth medium and the modified 9K medium); its buffer capacity by the buffers HCl/KCl and Na2HPO4/KH2PO4; and the influence of different ore grades in relation with the potential alkalinity associated have been investigated. For the first time, a mixed microbial consortium, obtained from a gas-phase biotrickling filter treating high loads of H2S, was employed revealing significant copper extraction by biological leaching. Results reveal that a single adaptation step of this biomass improved both kinetics and process efficiency, nearly doubling the amount of copper obtained compared with the non-adapted consortium. Nevertheless, the growth medium also influences the efficiency of the bioleaching process, enhancing copper extraction at higher sulfate concentration. The ore containing the metal is also a determining factor, obtaining same copper extraction for biotic and abiotic in one case, and enhancing up to 50 times from the abiotic in the other. Thus, this becomes a relevant limitation for the applicability of bioleaching for some ores, mainly due to the composition of the matrix.