Isolation of phosphorus-dissolving bacteria from Shaozhai mine and their solubilization of available phosphorus and available silica in coal gangue

A new way of resource utilization based on microbial technology is proposed for coal gangue, a solid waste in the process of coal mining. In this study, the coal gangue in Shaozhai mining area was selected as the research object, and firstly, a bacterial strain with available phosphorus solubilizing ability, Bacillus velezensis (referred to as Bacillus sp. XK2), was screened out from the gangue, and then experiments were carried out on solubilizing available phosphorus and available silicon in the gangue by using the Bacillus sp. XK2. Through one-way and orthogonal experiments, we explored the effects of factors such as medium pH, inoculum amount of bacterial solution, particle size of gangue, treatment time of gangue with Bacillus sp. XK2 on the solubilization of available phosphorus and available silicon in coal gangue by Bacillus sp. XK2, and determined the optimal conditions for the solubilization of effective phosphorus in the gangue by Bacillus sp. XK2: pH=8, inoculum amount of bacterial solution of 10.0 mL/50 mL of medium, gangue particle size of 0.25 – 0.50 mm, treatment time of 4 days. Under these conditions, the effective phosphorus content in the gangue reached 343.56 mg/kg, which was 41.49 times of the original gangue. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and high-performance liquid chromatography (HPLC) were used to analyze the solid-liquid phase products of the Bacillus sp. XK2 treatment, and the FTIR analysis showed that the gangue treated by the Bacillus sp. XK2 treatment contained Si—O—Si (473 cm⁻¹), Si—O—Al (537 cm⁻¹), Al—OH (908 cm⁻¹) and Si—O (1030 cm⁻¹) absorption peaks were weakened, indicating that the insoluble silica-aluminate was decomposed; XRD analysis showed that the diffraction peaks of phosphorus-containing minerals trilobaltic calcium phosphorite (CaHPO₄) and silica-containing minerals dol omite (KAl₂(AlSi₃O₁₀)(OH)₂) were weakened in gangue treated with Bacillus sp. XK2, indicating that Bacillus sp. XK2 promoted the decomposition of the above minerals to promote the development of coal gangue by dissolving them. In addition, HPLC analysis showed that the Bacillus sp.XK2 destroyed the silica-aluminate structure in the gangue by secreting organic acids such as propionic acid and succinic acid, which promoted the solubilization of phosphorus and silicon.