Study On Bacterial Leaching Of Yinshan Low Grade Complex Sulfide Ores

Bio-hydrometallurgy is an useful method for recovery of metals from minerals, which is based on the interactions between microorganisms and minerals. Because of its low energy consumption, environmentally friendly and lower investment, bioleaching has revealed huge potential in dealing with low-grade ores, and low-grade mine tailing and residues. Owing to higher leaching rate of mixed culture, bioleaching by mixed bacterial has become the mainstream of bioleaching research.The grade of Yinshan low grade complex sulfide ores is 0.3%, and the primary copper sulfide ores accounts for 87.59%of total copper content. According to the synergistic reaction of the ferrous oxidizing bacteria and the sulfur oxidizing bacteria, and the growing conditions were taken into account, four groups of mixed bacteria were used in this experiment, (1)30℃leaching system, At.ferrooxidans F1 and A.thiooxidans AO1 (2) 35℃leaching system, At.ferrooxidans F1, A.thiooxidans AO1 and L. ferriphilum YSK (3) 40℃leaching system,L. ferriphilum YSK and At. caldus s1 (4) 45℃leaching system,Sb. thermosulfidooxidans YN22 and At. caldus s1. The optimal mixed culture for leaching were studied at the very beginning. Then, the univariate and orthogonal tests in shake flasks were performed to optimize the leaching conditions, such as pH, rotational speed and pulp density. The results showed that the recovery rate of copper could reach to 76.3%when optimized conditions were applied. And the optimized conditions,combination of Sb. thermosulfidooxidans YN22 and At.caldus s1, initial pH of 1.7, and rotational speed of 190 r/min and pulp density of 15%(w/v) were obtained.Heap leaching is a common way to process the low grade complex sulphide ores. Since lots of heat was accumulated from the inner of the heap and the temperature was uneven during the bioleaching reaction, so it is necessary to investigate the effect of increasing temperature on the bioleaching behavior of low grade complex sulphid ores.The combination of the five bioleaching strains used in the former four mixed culture were used to investigate the optimal initial pH for leaching experiment. In this research,an increasing temperature treatment(the initial temperature of 30℃, and the final temperature 45℃at the interval of 5℃) bioleaching experiments were performed in flask. Temperature is elevated when the copper leaching rate is steady. The results showed that the optimal initial pH is 2.0. And in the experiment of the effect of increasing temperature on the bioleaching of Yinshan low grade complex sulphide ores, after 20 days the leaching rate of copper is only 14.17%when the temperature is 30℃,then the temperature was elevated to 35癈,the leaching rate was elevated to 21.17%when leaching for 10 days, again raising the temperature to 40℃, the leaching rate was increased to 31.59 after 12 days'leaching. When we raised leaching temperature to 45℃, and after 5 days of leaching reaction, the leaching rate of copper reach to 43.42%.