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CHALCOPYRITE BIOLEACHNG BY MODERATELY THERMOPHILIC ACIDOPHILIC ARCHAEA ACDIDIPLASMA SP. MBA-1

А. Г. Булаев, Khusain Valiev, Aliya Bugubayaeva, Azamat Zhikeev Vitalyi, В. С. Меламуд

Abstract

Bioleaching of sulfide minerals has been successfully applied worldwide for obtaining copper for decades. This technology provides about 5% of world copper production and is used as an alternative for pyrometallurgical processing of copper ores. Despite widespread of biohydrometallurgical technologies, there are a number of issues in this area, which impede the development and commercialization of bioleaching. For example, chalcopyrite (CuFeS2), the most abundant copper sulfide mineral, is refractory to biooxidation. An increase in chalcopyrite bioleaching rate with increasing temperature has been demonstrated in numerous works. Thus, it is reasonable to study chalcopyrite bioleaching at different temperatures using different microorganisms. Archaea of the genus Acidiplasma are moderately thermophilic iron- and sulfur oxidizing acidophilic microorganisms, which often predominate in microbial populations performing bioleaching processes, which have temperature optimum 45?55°C and are able to grow at temperatures up to 65°C. Among moderately thermophilic microorganisms predominant in biohydrometallurgical processes, representatives of the genus Acidiplasma are resistant to the highest temperatures. Thus, these archaea may have high potential for chalcopyrite bioleaching as their properties may allow performing bioleaching at higher temperatures than that is usually used in practice and chalcopyrite bioleaching using Acidiplasma archaea should be studied in detail. The goal of the present work was to study chalcopyrite bioleaching by the strain of the genus Acidiplasma under different conditions to evaluate possibility of its bioleaching at high temperature. Pure and mixed cultures of moderately thermophilic acidophilic microorganisms, including strains Acidithiobacillus caldus MBC-1, Sulfobacillus thermosulfidooxidans VKMV 1269T, and Acidiplasma sp. MBA-1 previously isolated from samples of ores and pulps of biooxidation reactors were used. The experiments were carried out in flasks with 100 mL of mineral nutrient medium supplemented with 0.02% yeast extract and 1 g of chalcopyrite on a rotary shaker for 20 days. Bioleaching was performed at 45, 55, and 60°?. Pure culture of the strain Acidiplasma sp. MBA-1 actively leached copper from chalcopyrite under different conditions; at 45°? it leached chalcopyrite more active than mixed culture of three strains. The increase in the temperature slightly increased copper bioleaching rate and it was maximal at 60°C. Increase in temperature up to 60°C led to the decrease in iron biooxidation rate. In the same time, inhibition of iron oxidation did not lead to the inhibition of copper leaching. Thus, the results obtained demonstrated that representatives of the genus Acidiplasma may be promising microorganisms to perform bioleaching of chalcopyrite containing ores and concentrates in a wide range of conditions as they tolerant to elevated temperature and low pH values.

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DOI resolver: doi.org/10.5593/sgem2020/1.1/s04.095

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