Promotional effect of Mn(II)/K2FeO4 applying onto Se(IV) removal

Abstract

Promotional effect of Mn(II)/K2FeO4 [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 [K2FeO4 alone, K2FeO4 with Al(III) ions, K2FeO4 with Fe(III) ions, and K2FeO4 with Mn(II) ions] were used for Se removal in spiked deionized water, and K2FeO4 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 K2FeO4 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 K2FeO4, and the Se(VI) species was reduced to insoluble Se(0) by γ-Fe2O3-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+, Ca2+ and SO42− had no intense effect on Se removal, while PO43- and humic acid (HA) inhibited Se removal in Mn(II)/K2FeO4 system. Mn(II)/K2FeO4 was an effective and convenient way for Se(IV) removal from polluted water.