Causes of inhibition of bioleaching by Cu are also thermodynamic

Abstract

BACKGROUND: Cu is an indispensable natural resource for society, as its use is widespread and essential for many technologies. Consequently, worldwide production is around 18×106 tn year−1, and close to 25% is produced by bioleaching. Bioleaching enables Cu extraction from minerals in atmospheric conditions by virtue of the catalytic activity of microorganisms. Microbial catalysis is mainly based on Fe3+ production as a leaching agent, a process known as Fe2+ bio-oxidation. However, bio-oxidation is inhibited by Cu2+ which limits the use of bioleaching with Cu mineral ores. RESULTS: This paper, for the first time, examines the effect of Cu2+ on continuous Fe2+ bio-oxidation using a packed bed bioreactor with supported cells. Bio-oxidation was possible in the presence of 20 g L−1 Cu2+, with a less than 25% reduction in rate. About 15% of this drop in rate is due to biological inhibition and the rest to a reduction in oxygen solubility because of salting-out. The biotic effect is reversed when Cu2+ is removed from the input, and the salting-out effect can be overcome by improving aeration conditions. CONCLUSION: These results, apart from having important ramifications for designing Cu ore bioleaching facilities, contribute to a more versatile and competitive idea of this clean technology.