Effect of chemical environment on copper tailings reinforced by microbially induced carbonate precipitation

The accumulation of large amounts of tailings produced in the beneficiation process of ores is one of the main challenges for mining industry related to their retention in tailings ponds and the potential hazard of tailings dams' failure. To enhance stability of tailings dams, microbially induced carbonate precipitation (MICP) has emerged as a novel technique for tailings treatment. However, the intricate chemical environment within tailings ponds affects the growth of microorganisms and can adversely impact the efficiency and effectiveness of MICP. This study investigates for the first time the factors that influence the growth of Sporosarcina pasteurii in a copper tailings pond characterized by weak acidity and the presence of copper ions. The adverse effects of the chemical environment in copper tailings ponds on MICP are investigated through mechanical tests and microscopic analyses on four groups of MICP-reinforced copper tailings. The results revealed that copper ions inhibited the growth of bacteria, while pH had an insignificant effect on bacteria. Hence, copper ions are identified as the main factor that weakens the reinforcing effect of MICP on copper tailings. Even though the weakly acidic environment has been shown to have a minor impact on the performance of MICP-reinforced copper tailings, maintaining the acid resistance of the reinforced tailings is crucial for ensuring long-term reinforcement effectiveness. It was also found that increasing the concentration of the bacterial solution and applying it in multiple injections, while controlling the pH of the cementation solution, could enhance the survival rate and activity of bacteria and improve the carbonate sedimentation environment. This would strengthen the reinforcing effect of MICP. The results demonstrated that MICP has promising potential for tailings treatment, but it is essential to address the adverse effects of the chemical environment in tailings ponds. The findings from this study provide valuable reference data for subsequent field experiments and engineering practices and facilitate the application of bio-mineralization in tailings ponds.