Multifunctional nanoparticles as effective adsorbents for fluoride removal from synthetic and drinking waters: equilibrium, kinetics, and thermodynamics

In this work, a series of bimetallic nano-oxide ZrO₂–CeO₂ xerogel adsorbent with different Ce/Zr molar ratio (0.1, 0.2, 0.3 and 0.5) were prepared in one step via sol–gel method in order to obtain the highest-performing composition for fluoride removal from drinking water. BET, SEM, EDX, TEM, FTIR spectroscopy, and XRD techniques were performed to characterize the solids before and after fluoride adsorption. The selected material exhibits a high surface area (S_BET = 255 m² g⁻¹) and a large porosity (V_P = 0.30 cm³ g⁻¹). FTIR spectroscopy demonstrated the significant role played by the adjunct sulfate anion and superficial hydroxyl groups in the defluorination process. Thermodynamic study confirms that the sorption is spontaneous and endothermic. Our adsorbent's behavior for the removal of fluoride is described by the Freundlich isotherm model. The pseudo-second order kinetic model represents the adsorption kinetic process. Less than 1 min, 100% of fluoride removal is reached in a wide pH range (2–8). The results of this study were effectively applied to natural drinking water in Tunisia. The development of innovative water treatment technology can be effectively advanced by using our multifunctional nano-oxide.