Recovery of Metals from Acid Mine Drainage

Acid Mine Drainage (AMD) poses a severe pollution problem attributed to current and past mining activities. Low pH, high concentrations of sulphates and various heavy metals makes AMD treatment a major concern because of possible deleterious effects of the effluent on the surroundings. Treatment methods to address AMD focus on neutralizing, stabilizing and removing problem pollutants through various physical, chemical and biological processes. This paper reports the results of studies conducted to develop and optimize the process of selective sequential precipitation (SSP) of selected metals (Fe, Cu, Al, Zn, Mn) to produce high recoveries of metals from AMD. Remediation options involve both chemical and biological strategies. At the SSP process abiotic system uses sodium hydroxide to raising pH with consequential precipitation of metal hydroxides. Biological system exploits hydrogen sulphide produced by sulphate-reducing bacteria in order to precipitate metals as sulphides at the various values of AMD pH. In the optimized SSP process the iron was removed from AMD as first to improve the selectivity of the operation.