LAUSR

Abstract Indirect bioleaching of Co and Ni from iron rich laterite ore was studied, using spent media produced by four fungal and bacterial species including Pseudomonas putida, Pseudomonas koreensis, Aspergillus niger and Penicillium bilaji. HPLC analysis showed that the main carboxylic acids in spent media were gluconic, citric and oxalic acids. Gluconic acid (with 10.8–14.4 g/l) was the predominant metabolite in spent media of Aspergillus niger and Pseudomonas species, whereas citric acid (with 6.2 g/l) was the main metabolite for Penicillium bilaji. Bioleaching kinetics was assessed at 45, 75 and 90 °C. Results indicated that the highest recovery rate of Ni and Co obtained from spent medium of Pseudomonas putida were 90.6 and 71.98%, achieved at 90 °C after 3 h. The corresponding activation energy for Ni and Co solubilization using spent medium of Pseudomonas putida were 41.82 and 43.91 kJ/mol, indicating that solubilization rate of Ni and Co from iron rich laterite ore is governed by a chemically controlled reaction mechanism.