Promotional effect of Mn(II)/KFeO applying onto Se(IV) removal.

Promotional effect of Mn(II)/KFeO [Fe(VI)] applying onto Se(IV) removal was determined for the first time, with description of reaction mechanisms. Four different combinations of water treatment agents [KFeO alone, KFeO with Al(III) ions, KFeO with Fe(III) ions, and KFeO with Mn(II) ions] were used for Se removal in spiked deionized water, and KFeO in combination with Mn(II) ions showed great removal efficiency. Over 90% of Se(IV) (200 μg/L) was removed within 2 min by using 1 mg/L of KFeO and 9 mg/L of Mn(II) ions (pH 7.0, 23 °C). XPS analysis identified that in the reaction process, Se(0) formed on the settlement. It was speculated that Se(IV) was oxidized to Se(VI) by KFeO, and the Se(VI) species was reduced to insoluble Se(0) by γ-FeO-Mn(II) nanocomplex. Insoluble Se(0) adsorbed on the surface of Fe-Mn particle and coprecipitated, thus removed from aqueous solution. As solution pH varied from 4.0 to 8.0, Se(IV) removal ratio ranged from 89% to 98% in the system. Co-existing ions such as Na, Ca and SO had no intense effect on Se removal, while PO and humic acid (HA) inhibited Se removal in Mn(II)/KFeO system. Mn(II)/KFeO was an effective and convenient way for Se(IV) removal from polluted water.