Hongfei Zhu* and Xuesong Zhao
Bioleaching has become increasingly important in commercial gold extraction because of its economic benefits. Thiobacillus thiooxidans (also known as Acidithiobacillus thiooxidans) is an important participant in synergic bioleaching processes. In this study, a novel strain was isolated from an underground coal mine, identified and named Thiobacillus thiooxidans CGMCC 10329. A consortium of microorganisms including T. ferrooxidans DSM14882, Leptospirillum ferrooxidans CCTCC AB207038 and T. thiooxidans CGMCC 10329 was used to leach four gold ores and four sulfur-containing coal samples; we then determined gold recovery rates and removal rates of elements. The content that may be harmful to the environment, such as sulfur and arsenic contained in the ores, was investigated. The synergic leaching results indicated that the maximum deprivation rates of carbon, sulfur and arsenic were respectively 59.91%, 67.21%, and almost 100%. Bioleaching pretreatment markedly improved the gold recovery rate by 10.7% to 20% in subsequent cyanidation, compared with traditional extraction operations. The average sulfur removal rate by synergic leaching of the four coal samples was 35.4%. This synergic leaching method, to some extent, broadens gold ore resources and benefits the environment by reducing the impact of coal burning.
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