Preparation and Characterization of Fluoride Adsorption Efficiency from Water of Mesoporous Hollow CaO Spheres

Abstract

The excessive consumption of fluoride, mostly via drinking water, poses a severe health risk to humans and has received the attention of many researchers. In this study, a novel mesoporous calcium oxide hollow sphere adsorbent was prepared to remove redundant fluoride ions from natural water. The as-prepared adsorbent was characterized by using several methods. The fluoride removal capacity of the adsorbent was studied by adsorption kinetics, isotherm, different pH, and co-existing ions. The Langmuir isotherm model showed a better fit to the adsorption data compared with the Freundlich isotherm model. The adsorbent achieved a maximum adsorption capacity of 181.69 mg/g at pH 6.5. The adsorption kinetics followed the pseudo-second-order model, and the adsorption process reached high efficiency in a large pH range of 3 to 11. The thermodynamic parameters demonstrated the spontaneous evolution of fluoride on mesoporous calcium oxide hollow spheres and revealed an endothermic reaction. Meanwhile, the presence of chloride, carbonate, and sulfate ions showed minimal effects on adsorption, thereby making the adsorbent an attractive material.