Evaluation of fluoride adsorption in solution by synthetic Al₂ O₃ /CeO₂ : A fixed-bed column study

A highly efficient fluoride adsorbent Al₂ O₃ /CeO₂ was synthesized in this work and used it to fluoride removal in the fixed-bed adsorption through changing the different experimental conditions (influent F^- concentration, flow velocity, and bed heights). The adsorption capacity was 9.72 mg/g. In addition, the Adams-Bohart and Thomas models were used to fit and evaluate the column breakthrough curve of fluoride removal process by Al₂ O₃ /CeO₂ , and the correlation coefficients (R² ) of the Thomas model were close to 1 under all experimental conditions. The structure of Al₂ O₃ /CeO₂ and the adsorption mechanism were confirmed by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), N₂ adsorption and desorption isotherm, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Moreover, the adsorption of fluoride (F^- ) was mainly through metal binding (MF) and hydroxyl binding (AlOH⋯F) on the surface of the Al₂ O₃ /CeO₂ . Furthermore, the regeneration and coexisting anions studies of Al₂ O₃ /CeO₂ were carried out, and the efficiency of adsorption was still above 70% after five cycles. PRACTITIONER POINTS: Removal of fluoride was studied by fixed-bed experiment, and the adsorption capacity of composite Al₂ O₃ /CeO₂ was 9.72 mg/g. The metal complex played important role in fluoride removal and reusability makes a long-term application for fluoride adsorption. Fluoride wastewater is pumped to the fixed-bed column, and fluoride ions are absorbed by Al₂ O₃ /CeO₂ through fluoride metal complex and aluminum hydrofluoride.