Sequential bioreduction–bioleaching and bioreduction–chemical leaching hybrid tests for enhanced copper recovery from a concentrator ball mill reject sample.

Dumping of poor but metal containing industrial waste is associated with several environmental issues. Exposure of these wastes to the natural environment offers serious concerns for the mineral processing industries to utilize them for metal recovery and check environmental pollution. In the present study, a novel sequential bioreduction–bioleaching and bioreduction–chemical leaching route as a hybrid process is compared and discussed for the enhanced recovery of copper from an industrial concentrator plant ball milling unit rejected sample. A mixed consortium of metal reducing bacteria (DMRB) initially adapted to high Fe(III) concentrations was found to cause mineralogical/matrix alteration (possibly silicate weathering) including Fe(III) bioreduction in the sample and dissolute 29.73% copper during the first 35 days under facultative anaerobic conditions. Sequential leaching of the bioreduced waste sample (generated from the first step) using a mixed meso-acidophilic bacterial consortium predominantly Acidithiobacillus ferrooxidans showed additional 28.72% copper dissolution within 2 days using 1 gL − 1 Fe(II). On the other hand, a comparative chemical leaching of the same bioreduced sample using 0.5 M H 2 SO 4 yielded additional 32.17% copper within 4 days of leaching and indicated better performance than the bioleaching tests. [ABSTRACT FROM AUTHOR]