Comparison of Bio- and Ferric Leaching for Beneficiation of Bulk Copper-Nickel Sulfidic Concentrate

Abstract

Abstract Processing of sulfidic raw materials, including bulk concentrates of nonferrous metals, is a problem of current importance in metallurgy and waste recycling. In this study, leaching with a chemical ferric iron reagent was compared to two bio-approaches to process a bulk copper-nickel concentrate: (1) ferric leaching with a solution obtained by microbial oxidation and (2) stirred-tank bioleaching using an active acidophilic microbial community. The results of both the chemical and bio-processes indicated nickel dissolution, while copper was accumulated in leach residues. After short-term high-temperature leaching with the chemical or bio- solution (Fe3+, 10 g/L), the nickel content in solids decreased by 0.7 and 2.6%, respectively, while the copper content slightly increased (by 1.5–3.2%). Bioleaching at 40°C was characterized by a considerably higher efficacy of the process: nickel leaching reached 86.7%, and the copper content increased by ~5% in the bioleach residue. Based on these results, ferric leaching can be considered an inefficient method for selective nickel removal, while bioleaching may be a promising cost-effective approach characterized by relatively low environmental hazards to obtain a high-grade copper product. Moreover, ferric leaching with the bio-solution can improve the grade of monometallic sulfidic concentrates due to additional selective nickel extraction.