Removal of fluoride from aqueous solution using Zr(IV) immobilized cross-linked chitosan

In the present paper, zirconium immobilized cross-linked chitosan (Zr-CCS) was reported for the adsorption of fluoride. Zr-CCS was synthesized by methods of membrane-forming and subsequent cross-linking reaction. Zr-CCS was characterized by FTIR, XRD, and SEM technologies. Batch adsorption experiments were performed to evaluate the adsorption capacity of Zr-CCS toward fluoride. The adsorption of fluoride onto the Zr-CCS favored at low pH values, and reduced in the presence of other co-anions. The adsorption equilibrium data had a good agreement with the Langmuir isotherm model, and the maximum adsorption capacity was calculated as 48.26 mg/g for fluoride at 303 K and natural pH (6.0). Thermodynamic parameters indicate that the nature of fluoride adsorption was spontaneous and endothermic. The adsorption mechanism of fluoride onto the Zr-CCS was controlled by chemical ion-exchange and electrostatic attraction between Zr-CCS and fluoride.