Defluoridation from aqueous solution by chitosan modified natural zeolite

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. (C) 2012 Society of Chemical Industry