Evolution of Acid Mine Drainage Formation in Sulphidic Mine Tailings

摘要: Sulphidic mine tailings are among the largest mining wastes on Earth and prone to produce acid drainage (AMD). The formation of AMD is a sequence complex biogeochemical mineral dissolution processes. It can be classified in three main steps occurring from operational phase impoundment until final appearance after operations ceased: (1) During pH-Eh regime normally alkaline neutral reducing (water-saturated). Associated environmental problems include presence high sulphate concentrations due gypsum-anhydrite, and/or effluents enriched elements such as Mo As, which desorbed primary ferric hydroxides during flotation process. (2) Once mining-related has ceased, sulphide oxidation starts, resulting an acidic zone ferrous iron-rich plume below front, that re-oxidises once it surfaces, producing first visible sign AMD, i.e., precipitation ferrihydrite concomitant acidification. (3) Consumption (reactive) neutralization potential gangue minerals subsequent outflow acidic, heavy metal-rich leachates step evolution system. multi-colour efflorescent salts this stage.