A novel biphasic leaching approach for the recovery of Cu and Zn from polymetallic bulk concentrate

• Consortium gave highest IOR of 3909 mg/L/h at no metallic stress in column reactor.
• It showed 51 times higher IOR compared to wild type consortium in metallic stress.
• Bioregenerated ferric iron yielded 52.2 and 2.6 g/L Zn and Cu, respectively.
• CYANEX® 301 used first time for metal recovery from PBC leachate.
• First biphasic process for PBC and recovery of metals.

In scale-up biphasic leaching process of polymetallic concentrate, the ferric bioregeneration cycles were performed in 15.0 L down flow packed bed reactor; whereas the chemical leaching cycles were done using the biogenerated ferric in an indigenously designed 10.0 L stirred tank reactor. The consortium took 25 cycles for proper biofilm formation. It showed highest iron oxidation rate (IOR) of 3908.21 mg/L/h at 25th cycle under no polymetallic stress. Even under stressed conditions, it was 2650–558 mg/L/h. Cu extractions were 86.63–46.51 and Zn extractions were 67.89–14.74% in 1st–4th cycle, respectively. The developed consortium exhibited 17–51 times higher IOR compared to original wild type consortium. Extraction isotherm for zinc with 30% Cyanex® 301 indicated that a total of two stages are required for its complete extraction using the phase ratio of 2:1 at equilibrium pH 1.5, leaving behind Fe(II) in the raffinate.

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