The use of low grade limestone in acid mine drainage treatment

Abstract

In this study, low grade limestone (LGL) was used in treating acid mine drainage (AMD). Based on X-ray fluorescence (XRF) result, the content of calcium carbonate mineral in limestone used was around 80% that can be considered as LGL. The pH of AMD samples increased after treated with all parameter weights of LGL at every five minutes of interval times. The parameters weights of LGL used in the experiments were 1.0, 2.0, 3.0, 4.0, 5.0 and 6.0 g. For every parameter weight of LGL, the interval times used were 0, 5, 15, 20, 25 and 30 minutes. The highest of pH value obtained was 6.44 ± 0.00 by using 6.0 g of LGL at interval time 30 minutes. The suitable pH value chosen was 6.11 ± 0.00 by using 5.0 g of LGL at interval time 20 minutes because the parameter had complied with Standards A and B of Environmental Quality Act 1974 with less cost compared to other parameters. Heavy metals content such as arsenic, cadmium, chromium, iron, manganese and zinc had decreased after reaction with all LGL weights. The content of arsenic in AMD samples after reaction with all LGL weights had complied with both standards’ requirement except with 1.0 g of LGL. The percentage of removal heavy metals by using all parameter weights of LGL such as arsenic, cadmium, chromium, iron, manganese and zinc were around 98.8 to 99.8%, 53.8 to 88.5%, 94.7 to 96.5%, 99.6 to 100%, 34.6 to 38.9% and 27.0 to 90.1%, respectively.