An integrated bioprocess for simultaneous iron oxidation and precipitation in hydrometallurgical leach solution

This study developed an integrated bioprocess comprising a continuous stirred tank reactor (CSTR) and a gravity settler for precipitative removal of Fe(III) from hydrometallurgical processing at ambient temperature. CSTR was fed with the raffinate solution (pH 1.4) from Zijinshan copper heap bioleaching plant containing nutrients and trace elements. In the CSTR, Fe(II) was biologically oxidized and pH was controlled by using KOH and CaCO3. The solution redox potential and pH was maintained at 580-600 mV (vs Ag/AgCl) and 2.5-3.0, respectively. The oxidation rate of Fe(II) was 1.0 g/L.h. The sludge in the gravity settler was recycled to CSTR as jarosite seeds and carrier material for microbial cells. Iron and sulfate removal efficiencies were 52 and 21%, and 86 and 32% at pH 2.6 and 3.0, respectively. The precipitate was characterized by X-ray diffraction (XRD) and elemental analysis, indicating the formation of mainly jarosite in the gravity settler.