Possibilities for Co(III) dissolution from an oxidized ore through simultaneous bioleaching of pyrite

•Reductive leaching of cobalt (III) is possible by ferrous iron generated via bio-oxidation of pyrite.•Fe3+/Fe2+ cycling exists and is efficiently maintained when bacteria are present.•75% of cobalt could be recovered within 12 h by bioleaching ore/pyrite mixture at 5/1 ratio.•Less stoichiometric amount of ferrous iron is required when cobalt leaching is coupled to pyrite bioleaching.

Solubilisation of Co(III) from a heterogenite met in copper cobaltiferous oxide ore has been realized through reductive leaching using ferrous iron generated via bio-oxidation of pyrite. Biotic and abiotic experiments at various pulp densities and redox potentials have been performed and results compared. Cobalt leaching at elevated redox potential is possible, offering cost reduction benefits due to reduced consumption of ferrous iron. At elevated potential of 625 mV, however, the initial rate of cobalt leaching has been found as 115 mg/(g ore)⋅(24 h), lower than the rate of 865 mg/(g ore)⋅(24 h) registered at 505 mV. Less stochiometric amount of ferrous iron was required when cobalt leaching was coupled to pyrite bioleaching, with 75% of cobalt recovered for 12 h at the optimally found conditions. It could be inferred that the Fe3+–Fe2+ cycle exists and is efficiently maintained through bacterial presence in the studied system.