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

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 SO₄^2- had no intense effect on Se removal, while PO₄^3- 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.