Bioleaching of Coal Gangue and Residual Coal by Ochrobactrum sp. - B2: Enhancing Silica Extraction and Mitigating Toxicity in Coal Tailings

Coal tailings are typical by-products of coal preparation plants, primarily consisting of coal gangue and bio toxic residual coal. The rational utilization of coal gangue and treatment of residual coal pose significant environmental challenges. In this study, five strains with silicon activation capabilities were isolated from coal tailings, and a strain named Ochrobactrum sp. B2 was selected and purified. Using nitrosoguanidine (NTG) mutagenesis, a strain B2-M with stronger adaptability to coal tailings was obtained. Based on its metabolic characteristics, the conditions for biological leaching were optimized, resulting in an available silicon concentration in the leachate reaching 320.54 mg/L. Through direct and indirect leaching experiments, the adhesion and synergistic leaching mechanisms between bacteria and coal tailings were investigated. Kinetic results indicated that the biological leaching process follows chemical reaction control. FT-IR and GC-MS analyses demonstrated that the B2-M strain could disrupt and decompose the residual coal in coal tailings, converting it into utilizable small molecule organics and thus enhancing the leaching efficiency of available silicon from coal gangue. The combined capabilities of the B2-M strain for decomposing residual coal and leaching available silicon reduced the toxicity of polycyclic aromatic hydrocarbons in coal tailings, significantly improving the green utilization efficiency of coal tailings.