Efficient removal of antimony by a facile liquid-controlled strategy reinforced hematite-spinel (Fe2O3-MnFe2O4) composite: construction, simulation and practical evaluation

Abstract

Currently, aqueous antimony contamination has become a non-negligible issue due to its scale industrious production and potential health risk. Herein, we prepare a novel hematite-spinel (Fe2O3-MnFe2O4) adsorbent by a one-step hydrothermal method for aqueous antimony deep purification, in which interfacial Fe-Mn bidentate complex sites are determined as the reinforced one by X-ray absorption spectroscopy (XAS) analysis and density functional theory (DFT) simulation. Through facile alkaline control by NH3·H2O and Fe/Mn proportion adjustment, the intrinsic synthesis kinetics of materials are precisely regulated that MnFe2O4 nano-particles successfully in-situ form on the Fe2O3 surface, in which sufficient adsorption sites are guaranteed by the small size effect. The adsorption experiment further demonstrates that the composite material is effective in Sb(III) and Sb(V) elimination, in which the adsorption capacity reaches up to 42.7 (Sb(III)) and 32.4 mg·g−1 (Sb(V)) (initial concentration 5.0 mg·L−1). The Sb K edge Extended X-ray absorption fine structure (EXAFS) analysis shows that antimony molecules occur as two typical complexation forms on the MnFe2O4 interface, in which an edge-sharing with Fe-O octahedron (Fe-Fe-ES) and two corner-sharing with Fe-O octahedron and Mn-O tetrahedron (Fe-Mn-CS) are exhibited. Further DFT calculations indicate that the Fe-Mn-CS has the highest adsorption energy for Sb(III) (-3.31 eV) and Sb(V) (-5.12 eV), which is rationally interpreted by the compatible overlapping of Fe 3d and O 2p as well as interfacial electron redistribution in Mn atom. This work may represent a new strategy in structure design and provide an alternative perspective in adsorption mechanism illustration.