Effect of organic nutrients on bioleaching of low-grade copper concentrate at different temperatures

Abstract

The goal of the present work was to study the effect of different organic nutrients (yeast extract and molasses) on the biooxidation of copper concentrate containing chalcopyrite, tennantite, sphalerite, and pyrite in batch experiments at different temperatures (of 40 to 55°C). For the experiments, representatives of microbial groups predominant in biohydrometallurgical processes, bacterium of the genus Sulfobacillus, Acidithiobacillus caldus, and archaea of the genus Acidiplasma, were used. It was shown that both temperature and addition of organic nutrients in the medium affected the activity of the bioleaching. In the same time, the effect of organic nutrients was significant only at high temperatures (50 and 55°C). In all experiments, biooxidation rate decreased at the highest temperature, 55°C. Since among the strains used in the study, only A. caldus MBC-1 is autotroph, which is able to provide the population with organic nutrients and is not active at 55°C, at this temperature it was not able to maintain activity of other strains. Therefore at 55°C, biooxidation activity strongly depended on the presence of organic nutrients. Despite temperature and presence of organic nutrient affected activity of concentrate biooxidation that was revealed by the differences in pH, Eh values and iron ions concentrations in the medium, copper, zinc and arsenic extraction rates depended on these factors to a lesser extent.