[Adsorption Performance and Mechanism of HZO@SGH for the Removal of Fluoride from Aqueous Solution]

Three-dimensional porous composites based on hydrous zirconium oxide and self-assembled graphene hydrogels (HZO@SGH) were successfully synthesized via homogeneous precipitation. HZO@SGH was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) to investigate the morphology and the defluoridation mechanism. The adsorption performance and mechanism of HZO@SGH for fluoride was investigated via batch adsorption experiments. The results revealed that the adsorption capacity of HZO@SGH for fluoride was obviously higher than that of HZO or SGH singly. The adsorption data for fluoride onto HZO@SGH complied with the pseudo-second-order kinetic model, indicating that the adsorption rate was mainly controlled by chemical adsorption. The adsorption process could be described well with the Dubinin-Radushkevich isotherm model, as the maximum adsorption capacity was approximately 31.79 mg·g^-1, which is higher than that of some zirconium-containing adsorbents, as previously reported. HZO@SGH showed excellent adsorption properties in the fluoride solution contained NO₃^-, Cl^-, and a low concentration of SO₄^2- (≤ 10 mg·L^-1) at low pH (3-6.5). The preparation of HZO@SGH was convenient and environmentally friendly, as it was easily separated from the fluoride solution and did not cause secondary pollution. Hence, the prospect of HZO@SGH in practice was brilliant.