Exploration of different adsorption performance and mechanisms of core-shell Fe3O4@Ce-Zr oxide composites for Cr(VI) and Sb(III)

Abstract

Removal of toxic Cr(VI) and Sb(III) from wastewater is crucial owing to their potential hazard to the environment and human health. In this work, a novel magnetic composite, core-shell Fe3O4@Ce-Zr binary oxide (Mag@Ce-Zr), was synthesized by a simple and eco-friendly co-precipitation method to remove Cr(VI) and Sb(III). The synthetic Mag@Ce-Zr composites exhibited superior magnetic separation (saturation magnetization value was 43.8 emu/g), great maximum adsorption capacities toward Cr(VI) and Sb(III) (66.7 mg/g for Cr(VI) and 365.2 mg/g for Sb(III)) and remarkable regeneration and reusability property. The adsorption mechanisms of negatively charged Cr(VI) oxyanions involved electrostatic attraction and the formation of Ce/Zr-O-Cr complexes. However, Sb(III) was adsorbed mainly through surface complexation with abundant hydroxyl groups to form Ce/Zr-O-Sb complexes. More importantly, based on X-ray photoelectron spectroscopy analysis, partial Cr(VI) and Sb(III) were converted to less toxic Cr(III) and Sb(V) by the core Fe(II) and shell Ce(IV) of Mag@Ce-Zr through electron transfer during adsorption process. Results revealed that the Mag@Ce-Zr composites displayed greater potential in the removal of Sb(III) from wastewater owing to its higher affinity with antimony species.