M. Hosseini Nasab - Mining Department, University of Sistan and Baluchestan, Zahedan, Iran
M. Noaparast - School of Mining Engineering, College of Engineering, University of Tehran, Tehran, Iran
H. Abdollahi - School of Mining Engineering, College of Engineering, University of Tehran, Tehran, Iran

In this research work, the bio-leaching of Co and Ni from an iron-rich laterite ore is assessed using the acidophilic heterotrophic (Delftia acidovorans)and autotrophic (Acidithiobacillus ferrooxidans) bacteria. The metabolic products of the acidophilic bacteria play an important role in bio-leaching. The results obtained from the indirect bio-leaching indicate the highest nickel recoveries of up to ۸۳.۶۵% and ۸۰.۱۸%, respectively, by the supernatants of Acidithiobacillus ferrooxidans and Delftia acidovorans, both measured at ۹۰ °C for ۳ h with a stirring speed of ۳۷۰ rpm and S/L of ۰.۱, while the corresponding cobalt recovery rates have reached ۸۶.۹۳% and ۸۳.۹۴%, respectively. The iron dissolution rates in these conditions for the two studied bacteria are ۶۴.۳۴% and ۵۴.۴۱%, respectively. The nickel and cobalt extractions by the indirect bio-leaching of Delftia acidovorans are, respectively, ۲۹.۸۴% and ۲۳.۷۵% higher than those for the direct bio-leaching, performed at ۳۰ °C and ۱۵۰ rpm of an incubator shaker for ۳۰ days. For the indirect bio-leaching, the chemical control has a larger influence on the dissolution rate of the iron-rich laterite compared to the diffusion control. The activation energies of nickel and cobalt in the chemical control model are ۴۰.۰۷ and ۳۹.۰۸ kJ/mol, respectively.

laterite, acidophilic bacteria, supernatant, Kinetics, chemical control