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

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 to 558 mg/L/h. Cu extractions were 86.63 to 46.51 and Zn extractions were 67.89 to 14.74% in 1st to 4th cycle respectively. The developed consortium exhibited 17 to 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.