Studies of hybrid ceria polypyrrole CPP-2 composite for effective defluoridation from potable water

Abstract

Drinking water sources should eliminate fluoride ions, as they pose a serious threat to human health. By using in situ oxidative polymerization and Pechini’s method of CeO2 (CO), a new hybrid composite, CPP-2, was designed. Several physicochemical techniques were used to establish the properties of the adsorbent in its as synthesized state. The F- ions were removed from effluent using the hybrid composite adsorbent. The adsorption isotherm model was best represented by the Langmuir adsorption isotherm model. It yielded a maximum adsorption capacity of 351.8 mg/g at an optimal pH of 4 ± 0.2 at room temperature. The pseudo second order model best describes the adsorption process according to kinetic results. To get a detailed understanding of the fluoride adsorption mechanism, FTIR and XPS spectra are analyzed. Anionic exchange of the hydroxyl groups with F- ions and electrostatic attractions of the protonated hydroxyl on the surface of the adsorbent, as well as the nitrogen atoms of the amino groups from the polypyrrole (PP) moiety with the F- ions, were responsible for the process. The enthalpy change (ΔH° = +6.32 KJ/mol) and Gibbs free energy (ΔG° = -8.95 KJ/mol) were obtained from the thermodynamic data, which demonstrated the spontaneity, feasibility, and endothermic nature of adsorption. It had a great potential for defluoridation from groundwater at a pH level below the thresholds specified by the WHO and could withstand up to five cycles of adsorption and desorption. The overall results exhibited that CPP-2 has an enormous promise for defluoridation.