Comparative fluoride sorption study of new calix[4]arene-based resins Original Research Article

The present article demonstrates the synthesis of p-tetraaminocalix[4]arene- and p-tetrathioureacalix[4]arene-based resins (4 and 5). The resins (4 and 5) were characterized by using different analytical techniques such as FT-IR and elemental analysis. In addition, their comparative fluoride sorption study was conducted and it was observed that 5 is highly efficient for the removal of fluoride from aqueous media at a wide range of pH as compared to 4. Consequently, on the basis of kinetic and thermodynamic studies, the pseudo first-order, pseudo second-order, entropy, enthalpy, and Gibbs free energy of fluoride sorption onto resin 5 were calculated. The experimental data were also evaluated by equations of isotherms used, i.e., Freundlich, Langmuir, and Dubinin–Radushkevich. The observations reveal that the sorption is favorable and confer the physiosorption interaction between resin 5 and fluoride.