The Generation and Treatment of Acid Rock Drainage

摘要

This review of the chemistry of acid rock drainage (ARD) concentrates on what the author thinks are important but not obvious geochemical principles in the generation and treatment of ARD. In ARD generation, the role Fe(Ⅲ) plays in the oxidation of sulfides, the generation of further acidity, and the release of minor constituents of concern (COCs) is explained. In ARD treatment, three geochemical principles are described. Of most importance, is the concept of mineral acidity and the prominent role iron and aluminum play in the treatment of ARD. Second in importance is the role oxidation and reduction play in the sequence of treatment steps and in the difficulty of removing minor constituents such as arsenic and selenium. Finally, how complex ion formation can frustrate the removal of some metals such as aluminum and zinc is explained. For the removal of trace COCs in ARD, the role of adsorption and co-precipitation onto the oxyhydroxide precipitates is important to the achievement of environmental guidelines.