Effect of carbonate on release and transport of toxic elements from coal
碳酸盐岩抑制煤中有害元素释放和迁移能力的研究

To provide the basis for prevention and treatment of acid mine drainage (AMD) for the karst region, we explored the mechanism of carbonate rock control of toxic elements (Fe, Mn, Cu, As etc.) in karst geological sites. Three different leaching columns composed of coal and carbonate were employed to determine how carbonate affects release and transport of toxic elements in coal. The results show that carbonate can effectively neutralize the acidity caused by the oxidation of pyrite and increase the pH value of the leachate. The total amounts of SO2-4 in the leachate from the three leaching columns were almost equivalent, suggesting that the ability of carbonate to immobilize S in coal is poor. Carbonate can effectively immobilize Fe, Cu and As, but its effect on Mn, Pb and Cd was relatively poor. It is concluded that carbonate can effectively control the formation and evolution of AMD, and it is an ideal reaction medium to prevent and treat AMD in carbonate rock areas.