Synergistic effect of biogenic Fe3+ coupled to S° oxidation on simultaneous bioleaching of Cu, Co, Zn and As from hazardous Pyrite Ash Waste

Pyrite ash, a waste by-product formed during roasting of pyrite ores, is a good source of valuable metals. The waste is associated with several environmental issues due to its dumping in sea and/or land filling. Although several other management practices are available for its utilization, the waste still awaits and calls for an eco-friendly biotechnological application for metal recovery. In the present study, chemolithotrophic meso-acidophilic iron and sulphur oxidisers were evaluated for the first time towards simultaneous mutli-metal recovery from pyrite ash. XRD and XRF analysis indicated higher amount of Hematite (Fe2O3) in the sample. ICP-OES analysis indicated concentrations of Cu > Zn > Co > As that were considered for bioleaching. Optimization studies indicated Cu - 95%, Co - 97%, Zn - 78% and As - 60% recovery within 8 days at 10% pulp density, pH - 1.75, 10% (v/v) inoculum and 9 g/L Fe2+. The productivity of the bioleaching system was found to be Cu - 1696 ppm/d (12% dissolution/d), Co - 338 ppm/d (12.2% dissolution/d), Zn k 576 ppm/d (9.8% dissolution/d) and As - 75 ppm/d (7.5% dissolution/d). Synergistic actions for Fe2+ - S degrees oxidation by iron and sulphur oxidisers were identified as the key drivers for enhanced metal dissolution from pyrite ash sample. (C) 2016 Elsevier B.V. All rights reserved.