Efficient defluoridation of water by employing hybrid nanosized cerium oxides embedded within cross-linked cellulose foam

Abstract

Efficient defluoridation utilizing current hybrid nano-oxides remains a great challenge because of low loading capacity and hindered nucleation during immobilization. In this study, a new adsorbent for defluoridation was developed by encapsulating nanosized cerium oxides within a cross-linked network of cellulose foam using an embedding method. The controllable structure, uniform dispersion, and high content of NCO endowed the composite with high efficiency for fluoride removal. The batch adsorption experiments exhibited a broad pH range (2.0–6.0) for optimal fluoride adsorption and confirmed that NCO@CF had a maximum adsorption capacity of 109.88 mg·g−1 at pH 4.0, which was much higher than that of other materials. Exceptional adsorption selectivity was also observed, indicating strong attraction between NCO@CF and fluoride ions, even at high concentrations of competing ions. X-ray photoelectron spectrogram and the Fourier transform infrared spectra analyses suggested that the defluoridation mechanism involved ligand exchange and inner-sphere complexation between NCO@CF and fluoride. Batch adsorption–regeneration cycles demonstrated that NCO@CF could be effectively and consistently regenerated using an alkaline solution. In fixed-bed adsorption experiments, remarkable working capacities of 1782 and 480 bed volume were observed for NCO@CF at pH 4.0 and 6.0, respectively. The findings of this study provide insights into the practical application of hybrid NCO in efficient defluoridation from water.