One-step synthesis of zirconium dioxide-biochar derived from Camellia oleifera seed shell with enhanced removal capacity for fluoride from water

Zirconium dioxide-biochar (ZrO2/BC) with excellent fluoride adsorption properties, was successfully prepared by calcining the zirconium-impregnated byproduct from Camellia oleifera (C. oleifera) seed shell in a one-step method. Compared with C. oleifera seed biochar, the zirconium-impregnated C. oleifera seed shell biochar can effectively adsorb fluoride in water. The adsorption process is consistent with a pseudo second-order kinetic model and the Langmuir adsorption isotherm. Fluoride adsorption was tested in solutions ranging from pH to obtain the best pH value for adsorption. The fluoride adsorption mechanism was better understood by Zeta potential analysis. Thermodynamic studies indicated that the adsorption process was a spontaneous endothermic reaction. Scanning electron microscopy (SEM), Energy-Dispersive Spectroscopy (EDS) and X-ray diffraction (XRD) analyses revealed that the morphology and crystal form of the ZrO2/BC were improved and that fluoride could be effectively absorbed. Fourier-transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) were used to show how ZrO2 affects the surface of the zirconium-biochar and to show that the fluoride was removed from the water by ion exchange. This work can not only effectively remove fluoride from the water, but also reuse waste C. oleifera seed to reduce environmental pollution.