Attachment of Fe3O4 nanoparticles on UiO-66: A stable composite for efficient sorption and reduction of selenite from water

In the present work, Fe3O4 nanoparticles were attached to the surface of UiO-66, a zirconium-based metal–organic framework material and the composite material formed was used to remove selenite (Se(IV)) in water. The Fe3O4/UiO-66 composite were assembled by a facile two-stage strategy. Benefiting from the ultra-high specific surface area of UiO-66, the Fe3O4/UiO-66 also had a large specific surface area, which made it easier to expose the active sites of Fe3O4 on the surface of UiO-66. The XPS and Mössbauer spectroscopy analysis indicated that there was charge transfer between Fe3O4 and UiO-66 in the Fe3O4/UiO-66, which made the Fe3O4 on the surface of UiO-66 had enhanced reductive activity. The mechanism of Fe3O4/UiO-66 to removed Se(IV) from the solution was further investigated by Zeta potential, FT-IR, SEM, TEM, and XPS spectra. The results indicated that the Fe3O4 nanoparticles on the surface of UiO-66 not only interacted with selenite through electrostatic action and inner-sphere complex but could also reduce a large amount of selenite to the insoluble Se0. The combination of these three actions finally strengthened the removal of selenite. This study cloud promote the practical application of MOF-based composites in removing heavy metal ions.