Study of manganese removal in the process of mine water remediation

In this work a comparative study of manganese removal from pre-treated acid mine drainage is described. Manganese removal by three ways was realized. At the first method sodium hydroxide was added to raise pH of processed AMD to the 9.5 to promote the abiotic oxidation of soluble divalent species to insoluble form of manganese. Potassium permanganate was used at pH near neutrality for elimination of manganese from AMD by oxidative precipitation in the second process. A third method, as electrowinning, was applied, finalized to the anodic Mn recovery under MnO2 form. The results showed that the three methods are effective and manganese were removed from acid mine drainage for values that comply with environmental requirements. However, when sodium hydroxide was used as reagent, coprecipitation of manganese and magnesium present in AMD was observed. In the second experiment enhanced selectivity of the process and purity of obtained precipitates were achieved. In the process of electrowinning - over 95% of Mn removal under MnO2 form, with a high degree of purity (about 99%) was attained.