Enriched fluoride sorption using chitosan supported mixed metal oxides beads: Synthesis, characterization and mechanism

Adsorbents, lanthanum (III)–zirconium (IV) mixed oxide (LZMO) and chitosan supported lanthanum (III) and zirconium (IV) mixed oxides beads (CLZMOB), were prepared. The prepared sorbents were characterized using FTIR, SEM with EDAX, XRD and TGA–DSC studies. Sorption studies were performed at different temperatures, equilibrium time, pH values and in the presence of foreign ions in batch mode. Maximum fluoride adsorption occurred at pH 7 for both LZMO and CLZMOB. The kinetic study revealed an optimum equilibrium time as 50 min with an adsorbent dose of 100 mg/L at room temperature. The sorption data were fitted well with Langmuir isotherm. Thermodynamic parameters such as ΔG°, ΔH°, and ΔS° indicated that the nature of fluoride sorption is spontaneous and endothermic. The column experiment with CLZMOB at neutral pH was successfully employed for the removal of fluoride ions from synthetic fluoride water. 0.1 M NaOH was used for desorption studies and the regeneration ability was tested. Based on the column experiment, a defluoridation model has been illustrated. The results showed that CLZMOB could be an effective sorbent for the removal of fluoride from aqueous solutions.