Fluoride remediation from on-site wastewater using optimized bauxite nanocomposite (Bx-Ce-La@500): Synthesis...

Bauxite is a widely available Al-O-rich mineral with great potential for abating fluoride. However, low adsorption capacity, a narrow workable pH range, and a lack of clarity on the best removal mechanism hinder its application. In this work, a highly efficient bauxite nanocomposite (Bx-Ce-La@500) was synthesized via doping and pyrolysis, and its fluoride adsorption in industrial wastewater was examined. Doping Ce/La synergistically improved the fluoride adsorption affinity of the composite (from pH_PZC 8.0 ~ 10.0) and enhanced the •OH. The materials were characterized by SEM-EDS, BET, XRD, and TGA while XPS, FTIR, and DFT were used to investigate the mechanism of fluoride sorption. Results show that Bx-Ce-La@ 500 has a positive zeta potential of 26.3-23.1 mV from pH 1~ 10. The Langmuir model was the best fit with a maximum adsorption capacity of 88.13 mg/g and removal efficiency up to 100% in 50 ppm F^- solution. The high F^- removal was attributed to the enhanced surface affinity and the formation of adequate •OH on the material. Except for carbonate and phosphate ions, other ions exhibited negligible effects and the selective removal of F^- in real wastewater was high. The main mechanism of adsorption was the ligand/ion exchange and electrostatic attraction.