Bioleaching of Nickel-Containing Metallurgical Slag by Chemolithotrophic Microorganisms at Different Temperatures

The process of bioleaching of metallurgical slag containing nickel and copper was studied at 40, 45, and 50°C. The microbial communities grown at 40 and 45°C that included Leptospirillum ferriphilum and Sulfobacillus thermosulfidooxidans bacteria were used in the experiments. The microbial community, which was cultivated at 50°C, included the representatives of S. thermosulfidooxidans and Acidiplasma sp. It was demonstrated that dissolution of the solid phase, oxidation of ferrous iron by microorganisms were the largest at 45°C. At the same time, the majority of copper (95.5–100%) and nickel (92.3–100%) passed into the solution at the first day of bioleaching. The study of the kinetics of chemical leaching of non-ferrous metals over 4 h demonstrated that in the presence of 5 g/L Fe3+, the extraction of nickel and copper was 93.0 and 94.3%, respectively, while in the absence of Fe3+, 75.0% of nickel and 77.8% of copper passed into the solution.