Preparation of a novel CeO2/SiO2 adsorbent and its adsorption behavior for fluoride ion

摘要

The silica-based CeO2 adsorbent (CeO2/SiO2) was prepared for removing fluoride from the aqueous solution. The synthesized adsorbent was characterized by scanning electron microscope, energy dispersive spectrum, X-ray diffractometer, Fourier transform infrared spectrometer, and zeta potential measurement analyses. The adsorption batch experiments in the various experimental conditions including solution pH, contact time, initial fluoride concentration, and adsorption temperature were performed and investigated. The maximum adsorption capacity of fluoride into CeO2/SiO2 was 2.441mmol/g at pH3 and 298K. The adsorption kinetics and isotherms were well described by the pseudo-second-order model and the Langmuir model, respectively. The fluoride adsorption reached the equilibrium in 15min from the aqueous solution with the initial fluoride concentration of 400mg/l at 298K. In the temperature range of 298-338K, the maximum adsorption capacity of fluoride decreased from 2.441mmol/g to 2.109mmol/l at pH3. The adsorption thermodynamics study revealed that this process was a spontaneous, exothermic, and entropy-driving adsorption. Furthermore, the mechanism of adsorption was identified as the anion exchange and the electrostatic interaction. The desorption efficiency of fluoride-loaded CeO2/SiO2 adsorbent could reach about 95% by 0.1mol/l NaOH.