Passive treatment of acidic mine drainage by using limestone and calcite as the neutralizing agents (Bukit Besi, Terengganu)

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Date
2019-07
Authors
Nur Amirah Nabilah Bt Ali Khan
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Acidic mine drainage (AMD) has been a major concern faced by any operating mining sites worldwide. The main problems associated with the AMD is that it has a low value of pH or acidic and the heavy metals contained together with the AMD. This research focuses on increasing the pH of the AMD which is known to be dangerously low, as low as pH two and also to reduce the heavy metals content in the AMD by using limestone and calcite, serving as the neutralizing agents to achieve the objectives of this research. The AMD sample were taken in Bukit Besi, Terengganu and an actual AMD water sample was taken to be treated. The passive treatment of AMD sample was conducted, and water quality parameters were investigated which include pH, dissolved oxygen (DO) and electrical conductivity (EC), alkalinity analysis and heavy metals analysis. Chemical composition of both neutralizing agents was determined by using XRF analysis and the CaO percentage obtained for limestone and calcite are 54.31% and 55.82% respectively. The treatment of AMD sample shows that the sample treated with smaller particle size, (0 – 3) cm neutralizing agents reached optimum pH on day 3 while sample treated with bigger particle size, (5 – 7) cm neutralizing agents reached optimum pH on day 6. The iron and aluminium concentration start to reduce when the pH reached the suitable pH for iron and aluminium to precipitate which are pH 3.5 and pH 5 respectively. The durability test on both neutralizing agents displays that it is capable in treating the AMD sample even if it is recycled from previous treatment. This experimental work shows that the smaller particle size, (0 – 3) cm of both neutralizing agents are more effective than the bigger particle size, (5 – 7) cm. However, calcite perform better in treating the AMD sample compared to limestone.
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