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A B S T R A C TThe removal of Mn 2+ and Fe 2+ 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 (Ca 2+ , Mg 2+ ) and alum addition on the removal of Mn 2+ and Fe 2+ was examined. The partial removal of Mn 2+ using aeration in single and dual metal system was 30.6% and 37.2%, respectively. The oxidant dose of 0.603 mg/L KMnO 4 was the minimum amount needed to reduce Mn 2+ below its maximum contaminant level. The presence of Fe 2+ improved the removal of Mn 2+ due to the autocatalytic effect of hydrous manganese-iron oxide, where its presence was confirmed by digital microscopy and EDX. The presence of Ca 2+ and Mg 2+ as well as the alum addition after oxidation has a negative effect on the removal of Mn 2+ . The removal mechanism of Mn 2+ and Fe 2+ was a combination of oxidation and adsorption or co-precipitation between the hydrous oxide and the dissolved metal ions.

The aim of this study is to investigate the conditions for the removal of manganese ions from synthetic groundwater by oxidation using KMnO(4) to keep the concentration below the allowed level (0.05 mg/L). The process includes low-level aeration and addition of KMnO(4) in a Jar test system with Mn(2 + ) concentration of 0.50 mg/L, similar to that of natural groundwater in Taiwan. Different parameters such us aeration-pH, oxidant dose, and stirring speed were studied. Aeration alone was not sufficient to remove Mn(2 + ) ions completely even when the pH was increased. When a stoichiometric amount of KMnO(4) (0.96 mg/L) was used, a complete Mn(2 + ) removal was achieved within 15 min at an optimum pH of 8.0. As the amount of KMnO(4) was doubled, lower removal efficiency was obtained because the oxidant also generated manganese ions. The removal of Mn(2 + ) ions could be completed at pH 9.0 using an oxidant dose of 0.48 mg/L because Mn(2 + ) could be sorbed onto the MnO(2) particles. Finally, The MnO(2) particles were characterized using scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX).

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