Bioleaching of Copper-Zinc Concentrate at Different Temperatures

The goal of this work was to study the process of bioleaching of arsenic-containing polymetallic concentrate containing 16.0% Cu, 5.3% Zn, and 1.7% As, under different conditions. The dependence of the leaching of non-ferrous metals on temperature (45 and 55°C) and the use of CO2 and molasses as carbon sources for the microbial population in bioreactors, as well as differences in the composition of microbial populations formed in different conditions were studied. Increasing temperatures led to increased leaching of both copper and zinc. However, at a higher temperature (55°C), the use of additional carbon sources significantly affected the extraction of metals, while at 45°C, the extraction of metals did not differ significantly between different experimental variants. A study of the microbial populations of bioreactors showed that both temperature changes and additional carbon sources influenced the microbial populations that formed during the bioleaching process. When using carbon dioxide at 45°C, the total number of microbial cells was 1.4 times higher than in other variants, and at 55°C, it was 8 times higher. Changes in the relationships between microorganisms in microbial populations were also observed. At 45°C, microbial populations were dominated by iron-oxidizing heterotrophic archaea of the genus Ferroplasma, heterotrophic archaea of the genus Cuniculiplasma, sulfur-oxidizing autotrophic bacteria of the genus Acidithiobacillus, and mixotrophic iron- and sulfur-oxidizing bacteria of the genus Sulfobacillus. At 55°C, the microbial populations were dominated by bacteria of the genus Sulfobacillus and iron-oxidizing bacteria of the genus Leptospirillum. The use of carbon dioxide led to predominance of bacteria of the genus Sulfobacillus: the proportion of 16S rRNA gene fragment sequences of this genus was 99.9%.