Zirconium ion incorporated β-cyclodextrin and chitosan composites for nitrate and fluoride pollution remedy

Cyclodextrin and chitosan are derived from the biopolymers starch and chitin respectively. Both cyclodextrin and chitosan have primary alcohol in its structure and chitosan also possesses primary amine. In this study, these reactive functional groups were utilized to convert them into anion selective adsorbents. Ethylenediamine was grafted on β-cyclodextrin to introduce primary amine and converted into a composite by loading it with Zr (IV) [ZrECD]. Though chitosan has primary amine, ethylenediamine was grafted on it through the primary alcohol to introduce more adsorption sites. Then Zr(IV) was loaded on it [ZrECS] for the removal of nitrate and fluoride. Both ZrECD and ZrECS were characterized by BET surface area, porosity, FTIR, SEM, EDAX, XRD and TGA-DSC. The effect of adsorption parameters were investigated and various isotherm, kinetic and thermodynamic models were adopted to explain the nature of the adsorption. The maximum adsorption capacity exhibited by ZrECD and ZrECS towards nitrate/fluoride was 139.8/138 and 184.6/124.5 mg/g respectively. The efficient regeneration and repeated use of adsorbents were studied up to five cycles and 100 % efficiency was observed. The applicability of both ZrECD and ZrECS at field conditions was inspected by conducting experiments using nitrate and fluoride polluted drinking water samples.