Abstract:
Simultaneous multi-metal leaching from industrial pyrite ash is reported for the first time using a novel bioreactor system that allows natural diffusion of atmospheric O-2 and CO2 along with the required temperature maintenance. The waste containing economically important metals (Cu, Co, Zn &As) was leached using an adapted consortium of meso-acidophilic Fe2+ and S oxidising bacteria. The unique property of the sample supported adequate growth and activity of the acidophiles, thereby, driving the (bio) chemical reactions. Oxido-reductive potentials were seen to improve with time and the system's pH lowered as a result of active S oxidation. Increase in sulphur dosage (>1 g/L) and agitation speed (>150 rpm) did not bear any significant effect on metal dissolution. The consortium was able to leach 94.01% Cu (11.75% dissolution/d), 98.54% Co (12.3% dissolution/d), 75.95% Zn (9.49% dissolution/d) and 60.80% As (7.6% dissolution/d) at 150 rpm, 1 g/L sulphur, 30 degrees C in 8 days. (C) 2017 Elsevier B.V. All rights reserved.