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, ORe–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).