Simultaneous oxidation and immobilization of arsenite from water by nanosized magnetic mesoporous iron manganese bimetal oxides (Nanosized-MMIM): Synergistic effect and interface catalysis

Toxic arsenic species cycle in the geochemical process are strongly influenced by iron and manganese elements, thus understanding mutual transformation of multiple Fe/Mn redox states is essential to predict the redox transformation and sequestration of arsenic in natural environment. Herein, a nanosized magnetic mesoporous iron manganese bimetal oxides (Nanosized-MMIM) with highly well-ordered inner-connected structure and large surface area was fabricated, the obtained Nanosized-MMIM possessed higher content of surface-bound Fe(II) than Commercial Fe3O4 and Templated Fe3O4 due to the difference of standard redox potential of multiple Fe(II-III)-Mn(II-III) valence states and the synergistic effect of Fe-Mn bimetal oxides. This structural surface-bound Fe(II) was greatly associated to the OHads radicals that generated from the interface catalysis of materials via the Fenton-like pathway. The potential redox transformation of arsenic in liquid-solid two phase by using HPLC-ICP-MS and XPS investigation indicated that As(III) in water was mainly oxidized into As(V) by bulk solution OHfree radicals (30.39%) and surface-bound OHads radicals (69.16%), then the generated As(V) was subsequently adsorbed on the Nanosized-MMIM surface. This study could further improve the deeply understanding on the As(III) abiotic oxidation and sequestration in Fe-Mn co-existed natural environment such as minerals, soils and sediments.