Continuous and effective treatment of heavy metal in acid mine drainage based on reducing barrier system: A case study in North China

Abstract

The acid mine drainage (AMD) resulting from human mining activities has adversely affected across the worldwide. The heavy metals and acidity contained in AMD cause great harm to the ecological environment, which are difficult to remove at low cost and effectively. In this study, the acid regulation and heavy metal removal of AMD were investigated by using the reducing barrier system constructed with common industrial wastes of activated sludge and fly ash as the reaction medium. The optimized results indicate that more than 99% of Cu2+ and 100% of Zn2+ in the AMD are effectively removed, as well as a neutral pH of AMD is achieved. It was attributed to alkaline substances in the reducing barrier system regulate the pH of AMD effectively, while the reducing atmosphere created by the self-respiration of microorganisms in the system reduces SO42− to S2− and HS−, achieving the purpose of removing heavy metal ions by forming the precipitation of metal sulfides. Based on SEM-EDS, BET, FITR and Zeta potential characterizations, the removal mechanism of metal ions by the reducing barrier system were systematically elaborated. Moreover, the long-term effectiveness of the reducing barrier system is evaluated by several repeated simulated leaching experiments. This discovery achieves the purpose of “treating waste with waste” and provides an environmentally friendly, economic and long-term treatment method for local AMD.