Removal of Mn(II) from Aqueous Solutions Using Manganese-Coated Sand Samples

Two different manganese-coated samples, that is, manganese-coated sand (MCS1) (laboratory preparation) and a Birm sample (Birm, a commercial product; MCS2), were employed to assess their removal efficiencies for Mn(II) from aqueous solutions over a wide pH range (i.e., pH 5.0 to 10.5). The study was performed in both the absence and presence of sodium hypochlorite. The pH dependence data obtained through batch tests showed that the removal of Mn(II) by these solids significantly increased with increasing solution pH from 5.0 to 10.0. Moreover, the removal efficiency was more favored in the presence of sodium hypochlorite (4.0 mg·L−1). This suggested that the presence of NaClO caused the oxidation of Mn(II) to Mn(IV); hence, the formation of MnO2 at the surface of the manganese-coated samples further enhanced the removal efficiency of the solids. Moreover, the removal of Mn(II) was also performed under dynamic conditions in column experiments. The data from the column experiments also showed that the presence of NaClO significantly enhanced the removal capacity of MCS1, that is, from (10.93 to 20.21) mg·g−1, but only slightly increased that for MCS2, that is, from (59.34 to 65.44) mg·g−1 in the absence and presence of sodium hypochlorite, respectively.