Defluoridation from aqueous solution by chitosan modified natural zeolite

Abstract

Abstract BACKGROUND A novel hybrid material, chitosan‐modified zeolite (Ch‐Z), was synthesized for defluoridation. The structure was characterized by Fourier transform infrared spectroscopy ( FTIR ), scanning electron microscopy ( SEM ), X‐ray diffraction ( XRD ) and thermogravimetric analysis ( TGA ). RESULTS The maximum defluoridation capacity onto Ch‐Z was 4.16 mg g −1 from an initial fluoride concentration of 40 mg L ‐1 , which was almost three times higher than that of unmodified zeolite. The adsorption kinetics of fluoride onto Ch‐Z and zeolite followed pseudo‐second‐order and intra‐particle diffusion models, respectively. Based on a nonlinear method, the adsorption of fluoride onto Ch‐Z fitted the Freundlich and Redlich–Peterson isotherm models well. Various physicochemical parameters affecting the adsorption of fluoride onto Ch‐Z were investigated. It was observed that the maximum uptake of fluoride occurred in a pH range 4.5–5.5. CONCLUSION Although among various ions the presence of high concentration carbonate ions in aqueous solution had the greatest adverse impact on the adsorption of fluoride, Ch‐Z can be successfully used for treatment of real water samples. © 2012 Society of Chemical Industry