Removal of Heavy Metals from Acid Mine Drainage by Adsorption and Coagulation using Fly Ash = Removal of Heavy Metals from Acid Mine Drainage by Adsorption and Coagulation using Fly Ash

다국어 초록 (Multilingual Abstract)

Acid mine drainage (AMD) has emerged as one of the greatest environmental threats facing mining industry owing to its characteristic low pH, high acidity and elevated concentrations of metals and sulphate content. This study evaluates the efficiency of fly ash as a low cost material to remove heavy metals (Cu, Fe, Mn and Pb) from AMD. The effects of varying contact time, dosage and pH on adsorption were investigated using synthetically prepared AMD. The experiments was conducted in series of batches for adsorption using a mechanical shaker with 50mL AMD at various dosages of fly ash (0.1 - 0.8g/L) and coagulation using a standard jar tester of 1000mL AMD with chemical coagulant dosages (0.5 - 10g/L). Tests were also conducted with 50mL AMD without fly to evaluate the treatment efficiency of fly ash to chemicals. All tests were performed in duplicate for consistency and accuracy. The chemical composition of fly ash was characterized by X-ray fluorescence (XRF) and the result shows the fly ash is rich in calcium (CaO 54.9%). Leaching test of the fly ash was conducted using KLST and TCLP method to compare the results and evaluate the behavior of leaching ash in replenishing acidic media at low pH such as acid mine drainage. pH plays a significant role in heavy metal uptake in this study with increased in pH value the removal rate increased. The optimum dosage for Adsorption was found to be 0.4g/L with 60 min optimum contact time and coagulation 6mg/L with reduced metal concentrations much less than regulation standards for Cu, Fe, Mn and Pb. From all tests conducted fly ash proves more efficient with over 96% removal even at low dosages. The effectiveness of the treatment process will depend on the quality of the fly ash and the AMD. Therefore the use of fly ash for treatment of mine wastewater would represent a new market opportunity for this waste product. Recycling of fly ash will conserve the natural raw materials and abridge the disposal cost. It will also create new revenues and business opportunities while protecting the environment. Most significantly, the two waste products acid mine drainage and fly Ash could be neutralized and when reacted together to produce much cleaner water broadly compared to post process water derived from Lime treated AMD and sulfates removal rates were in the range of 90% in both experiments. Fly ash is more economical, sustainable.