Preparation of Composite Materials with Slow-Release Biocides and Solidifying Agents for Remediation of Acid Pollution in Coal Gangue

The processes of coal mining and washing generate a substantial amount of coal gangue. During prolonged outdoor storage, this waste can lead to both direct and indirect environmental pollution, as well as geological hazards. Recent research has indicated that the redox processes of coal gangue are regulated by microorganisms. Techniques such as the application of biocides and the facilitation of microbial interactions have proven effective in controlling the acidic pollution of coal gangue in the short term. However, conventional doping methods that couple sulfate-reducing bacteria with biocides face challenges, including a short effective duration and poor stability. To address these issues, this study utilized corn straw biochar as a microbial attachment material and incorporated water-retaining agents as slow-release biocide carriers, resulting in the development of an environmentally friendly microbial remediation material. This study selected 0.6 g of biochar produced from the pyrolysis of corn straw at 700 °C to immobilize sulfate-reducing bacteria. Additionally, 0.6 g of polyacrylamide was used to prepare a slow-release bactericide with 100 mL of a sodium dodecyl sulfate solution at a concentration of 50 mg·L−1. The composite remediation material successfully raises the pH of weathered coal gangue leachate from 4.32 to 6.88. Its addition notably reduces the sulfate ion concentration in the weathered coal gangue, with sulfate content decreasing by 86.45%. Additionally, the composite material effectively lowers the salinity of the weathered coal gangue. The composite immobilizes heavy metal ions within the weathered coal gangue, achieving an approximate removal rate of 80% over 30 days. Following the introduction of the composite material, significant changes were observed in the dominant microbial communities and population abundances on the surface of the coal gangue. The composite demonstrated the ability to rapidly, sustainably, and effectively remediate the acidification pollution associated with coal gangue.