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

The bioleaching process of metallurgical slag containing nickel and copper was investigated at temperatures of 40, 45, and 50°C. The experiments involved microbial communities cultivated at 40 and 45°C, which comprised the bacteria Leptospirillum ferriphilum and Sulfobacillus thermosulfidooxidans. The microbial community established at 50°C included representatives of S. thermosulfidooxidans and Acidiplasma sp. The findings indicate that the dissolution of the solid phase and the oxidation of ferrous iron by microorganisms reached their highest levels at 45°C. Under these conditions, the majority of copper (95.5–100%) and nickel (92.3–100%) released into solution within the first day of bioleaching. Kinetic studies of chemical leaching of non-ferrous metals during the initial four hours demonstrated that the presence of 5 g/l Fe resulted in the extraction of 93.0% nickel and 94.3% copper, whereas, in the absence of Fe, 75.0% of nickel and 77.8% of copper were extracted.