BIOLOGICAL LEACHING OF NON-FERROUS METALS FROM COPPER SLAG USING A STRAIN OF SILICATE-SOLUBILISING BACTERIA
Plamen Georgiev, Marina Nicolova, Irena Spasova
University of Mining and Geology “St. Ivan Rilski”, 1700 Sofia; E-mail: ps_georgiev@mgu.bg Corresponding author: ps_georgiev@mgu.bg

ABSTRACT. This study aims at the recovery of non-ferrous metals from pyrometallurgy copper slag enriched in diopside, fayalite, and protomangano-ferro-anthophyllite and containing 0.36 % copper, 1.93 % zinc, and 0.09 % cobalt by bioleaching with silicate-solubilising strain Bacillus megaterium CCM 3360. Two techniques of bioleaching were applied: (i) direct one-step bioleaching, where the bacterial strain was cultivated in an Ashby medium and the presence of copper slag; (ii) indirect bioleaching of copper slag with spent medium obtained after separation of the bacterial cells. The results revealed that 5 % pulp density was the optimal out of the tested pulp densities (5-10%), as 15 days was the optimal duration for the direct bioleaching and 3 days for the indirect technique. The formation of biofilm on the surface of copper slag particles was the primary mechanism of the leaching of non-ferrous metals, and their recovery was between 41.7-48.7%. Indirect leaching with bacterial metabolites played a secondary role in base metals leaching.
Keywords: copper slag, Bacillus, bioleaching, silicate bacteria

https://doi.org/10.58903/dw18920762

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