Enhanced fluoride removal from water by non-thermal plasma modified CeO2/Mg–Fe layered double hydroxides

Abstract

A novel fast and efficient adsorbent based on lamellar compound namely CeO2/Mg–Fe layered double hydroxide composite has been designed for fluoride removal from water. In order to improve fluoride removal efficiency, non-thermal plasma (NTP) was used to modify the surface state of composites. The prepared composites were characterized by powder X-ray diffraction, thermogravimetric analysis and surface area analyzer. Adsorption equilibrium and kinetics of fluoride on NTP modified composites were investigated. Experimental results indicated that the adsorption capacity was enhanced with NTP surface modification. The maximum adsorption capacity has been found to be 38.7–60.4mg/g. The kinetic data of adsorption were found to best fit the pseudo-second-order model, while the equilibrium data were found to be well described by Langmuir model. In order to understand the mechanism of adsorption, thermodynamic parameters such as ΔGθ, ΔSθ and Ea were calculated. After NTP treatment, the ΔSθ increased from −34.7J/mol·K to −0.770J/mol·K, the Ea decreased from 78.8kJ/mol to 58.9kJ/mol and the ΔGθ (25°C) decreased from −2.62kJ/mol to −3.14kJ/mol. These values indicate that the fluoride adsorption on NTP modified composites was improved.