Removal of Selected Heavy Metals in Acid Mine Drainage using Chemical Precipitation Method
Keywords:acid mine drainage, active treatment, absorbents
The major problem confronting Acid Mine Drainage (AMD) in the mining industry is the remediation method. Active treatment used large amount of chemicals and normally require high cost to operate. Treatment causes other environmental problems such as the production of sludge. While long duration mechanism took from passive treatment is a disadvantage for industry. Although passive treatment is less costly compared to active treatment, it usually takes months or years to treat the AMD from mining and only applied at abandoned mining site. In addition, passive treatment requires greater space during the treatment processes. Insufficient land use and unsuitable topography nowadays makes passive treatment hard to apply. Due to that reason, batch tests have been conducted to study on the diffusion of alkaline in different length and concentration of modified ceramic membrane. The optimal surface area and alkaline concentration were identified in order to develop semi-passive treatment experiment. Column experiment had been conducted to study on the efficiency of semi-passive treatment for neutralization of AMD. Results shows that chemical diffusion increased with increased of alkaline concentration and different surface area also influenced rate of diffusion. A total alkalinity for 20g is highest compared to 5g at 40250 mg/l and 23750 mg/l, respectively. Larger surface area makes alkaline particles easily spread. Therefore, ceramic membrane with 8cm gives the largest surface area compared to 2cm ceramic membrane. Results from sampling and analysis of treated effluent on a daily basis over 4 months period show the efficiencies of column experiment for increasing pH and alkalinity, removing of SO24- and selected heavy metals from effluent. As the time duration of semi-passive depends on the alkaline concentration in the column, thus it suffers limitations once the alkaline material is fully utilized. Column experiments showed a high percentage of heavy metals removal, with removal values of Cadmium, Ferum, Manganese and Zinc at 22.73%, 93.24%, 88.88% and 98.50%, respectively. Extensive research should be conducted thoroughly to obtain the optimum performance and characterization of semi-passive treatment for AMD by using different media as absorbents, such as polyurethane or activated carbon.