Abstract
Bioleaching of the bulk copper–nickel sulfide concentrate was proposed as a method to remove nickel from it and to obtain a concentrate containing copper as chalcopyrite. This approach is based on the different refractoriness of sulfide minerals in ferric sulfate solutions and oxidation by acidophilic microorganisms. The bulk concentrate contained 10.8% copper in the form of chalcopyrite (CuFeS2) and 7.2% nickel that occurred in pentlandite ((Ni,Fe)9S8) and violarite (FeNi2S4). Three microbial communities grown at 35, 40, and 50 °C were used for bioleaching. The microbial community at 40 °C was the most diverse in the genus and species composition. At all temperatures of the process, the key roles in bioleaching belonged to mixotrophic and heterotrophic acidophiles. The highest levels of nickel leaching of 97.2 and 96.3% were observed in the case of communities growing at 40 and 50 °C, respectively. At the same time, the bioleach residue, which could be characterized as a marketable high-grade copper (chalcopyrite) concentrate, was obtained only at 40 °C. This solid contained 15.6% copper and 0.54% nickel. Thus, the biobeneficiation of bulk sulfide concentrates can be a promising field of biohydrometallurgy.
Highlights
The beneficiation of bulk concentrates of nonferrous metals, such as copper–nickel and copper–zinc sulfide concentrates, is aimed at obtaining high-grade selective concentrates, which are of current importance for the metallurgical industry [1]
In this study, bioprocessing of the bulk copper–nickel concentrate with different thermoacidophilic microbial communities was compared at three different temperatures: 35, 40, and 50 ◦ C
At a lower temperature (35 ◦ C), relatively high content of nickel remained in the bioleach residue
Summary
The beneficiation of bulk concentrates of nonferrous metals, such as copper–nickel and copper–zinc sulfide concentrates, is aimed at obtaining high-grade selective concentrates, which are of current importance for the metallurgical industry [1]. To achieve selective metal leaching, environmentally sound cost-effective and easyto-use technologies are required. These technologies include biohydrometallurgical approaches (bioleaching/biooxidation) that are applied at industrial mining and metallurgical enterprises worldwide for the recovery of metals from sulfidic raw materials [3,4,5,6]. These bio-approaches are based on the activity of communities of acidophilic chemolithotrophic microorganisms that oxidize ferrous iron, elemental sulfur (S0 ), reduced inorganic sulfur compounds (RISCs), and sulfide minerals [7]. Biohydrometallurgy allows the processing of low-grade raw materials, products, and metallurgical wastes, with reduced emissions and discharges of toxic substances to air [6,10]
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