Interaction Mechanism of Re(VII) with Zirconium Dioxide Nanoparticles Archored onto Reduced Graphene Oxides

Zirconium oxide archored onto reduced graphene oxides (ZrO2@rGO) was fabricated via a hydrothermal method and used for Re(VII) removal from aqueous solutions. Scanning electron microscopy, Fourier transferred infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and X-ray photoelectron spectroscopy were used to characterize the as-prepared ZrO2@rGO. The results indicated that ZrO2 was successfully decorated on rGO. The maximum sorption capacity of ZrO2@rGO toward Re(VII) was 43.55 mg/g. ZrO2@rGO exhibited enhanced sorption capacity for Re(VII) in comparison with bare ZrO2 or rGO. The sorption kinetics could be described by the pseudo-second-order equation. The sorption process of Re(VII) on ZrO2@rGO was endothermic and spontaneous. X-ray photoelectron spectroscopy indicated the formation of an ionic bond of Zr-O with Re(VII). According to the density functional theory calculations, O-Re-Zr bonds on the surface of the monoclinic ZrO2 plane (m-ZrO2) (111) plane and tetragonal ZrO2 (t-ZrO2) (111) plane were formed when Re(VII) sorbs. The sorption energy of Re(VII) onto the t-ZrO2 (111) plane was 3.87 eV, being higher than that of Re(VII) onto m-ZrO2 (1.26 eV).