Synthesis of mesoporous magnetic γ-Fe₂O₃ and its application to Cr(VI) removal from contaminated water

In this study, mesoporous magnetic iron-oxide (γ-Fe₂O₃) was synthesized as an adsorbent for Cr(VI) removal. For material synthesis, mesoporous silica (KIT-6) was used as a hard template and to drive iron precursor into KIT-6, a 'greener', affinity based impregnation method was employed, which involved using a nonpolar solvent (xylene) and led to recycling of the solvent. The results of Cr(VI) removal experiments showed that the synthesized mesoporous γ-Fe₂O₃ has a Cr(VI) adsorption capacity comparable with 10 nm nonporous γ-Fe₂O₃ but simultaneously has a much faster separation than 10 nm nonporous γ-Fe₂O₃ in the presence of an external magnetic field under the same experimental conditions. Cr(VI) adsorption capacity onto the mesoporous γ-Fe₂O₃ increased with decreasing solution pH and could be readily regenerated. Therefore, mesoporous γ-Fe₂O₃ presents a reusable adsorbent for a fast, convenient, and highly efficient removal of Cr(VI) from contaminated water.