Column leach study III: effects of sampling location, sampling methods, and chemical abatement treatments on the dissolution of metals in gold-copper mine tailings.
Metal dissolution from tailings collected at a gold-copper mine mill site was examined by researchers from the U.S. Bureau of Mines using column leaching procedures and on-site field monitoring wells. The 3-year laboratory study reviewed effects of column waste depths, dry cycles, waste sampling locations, and metal dissolution abatement techniques. Results of the laboratory testing indicated that the concentrations of metals in the leachate gradually decreased with each leaching and that metal release from unsaturated tailings was enhanced in most, but not all, samples. Sulphide-rich tailings produced leachates with a pH in the range of 2 to 4, sulphate concentrations as high as 40,000 mg/L, and copper concentrations in the range of 0.2 to 2,400 mg/L. The effects of abatement treatments using phosphate, lime, and sodium lauryl sulphate were also examined, but the treatments were demonstrated to be of only marginal value. The interaction between tailings and wood chips, and tailings and a compost-peat moss mixture was also studied.