Synthesis and characterization of rGO/ZrO2 nanocomposite for enhanced removal of fluoride from water: kinetics, isotherm, and thermodynamic modeling and its adsorption mechanism

Abstract

A nanocomposite of rGO/ZrO₂ prepared by a simple hydrothermal method using GO and ZrOCl₂·8H₂O has been successfully utilized for the removal of fluoride from aqueous solutions by adsorption. The synthesized nanocomposite was characterized by various techniques, such as FT-IR, XRD, SEM, EDX, TGA, XPS, Raman spectroscopy and BET surface area measurement. Various process parameters viz. rGO/ZrO₂ dose, initial fluoride concentration, temperature and pH, which influence the removal of fluoride, were studied and it was found that the maximum uptake capacity of the nanocomposite was 46 mg g⁻¹ at 30 °C, pH 7, rGO/ZrO₂ dose of 0.5 g L⁻¹ and initial fluoride concentration of 25 mg L⁻¹. The rGO/ZrO₂ possesses a high surface area (632 cm² g⁻¹) and maximum adsorption occurs at neutral pH and ambient temperature. Therefore, rGO/ZrO₂ can be used for the adsorption of fluoride without much alteration in the quality of drinking water. The experimental data was applied to various kinetics, isotherm and thermodynamic studies. The monolayer adsorption of fluoride followed a pseudo-second order kinetic model, which was found to be spontaneous and endothermic in nature. The results obtained from the current adsorption system might be helpful for designing a continuous column system for the treatment of fluoride contaminated water.