Removal of manganese(II) and iron(II) from synthetic groundwater using potassium permanganate

The removal of Mn2+ and Fe2+ from synthetic groundwater via oxidation using potassium permanganate was investigated. Batch jar tests were carried out under a constant pH of 8.0, where the effect of parameters such as the oxidant dose, presence of co-ions (Ca2+, Mg2+) and alum addition on the removal of Mn2+ and Fe2+ was examined. The partial removal of Mn2+ using aeration in single and dual metal system was 30.6% and 37.2%, respectively. The oxidant dose of 0.603 mg/L KMnO4 was the minimum amount needed to reduce Mn2+ below its maximum contaminant level. The presence of Fe2+ improved the removal of Mn2+ due to the autocatalytic effect of hydrous manganese-iron oxide, where its presence was confirmed by digital microscopy and EDX. The presence of Ca2+ and Mg2+ as well as the alum addition after oxidation has a negative effect on the removal of Mn2+. The removal mechanism of Mn2+ and Fe2+ was a combination of oxidation and adsorption or co-precipitation between the hydrous oxide and the dissolved metal ions.