Synthesis of a Chitosan-Zeolite Composite Modified with La(III): Characterization and its Application in the Removal of Fluoride from Aqueous Systems

The high fluoride content of water in some areas of the world has garnered interest in searching for technologies and processes capable of efficiently removing fluoride at low cost. The use of bio adsorbent is a good and environmentally friendly technique for removing fluoride, due to the green nature of employed materials. Because of its high adsorption capacity, chitosan is a promising biosorbent that contains high amounts of amino and hydroxyl groups capable of interacting with fluoride. Furthermore, the presence of electropositive metal ions, such as transition metals and rare earth elements, like lanthanum, can improve the adsorption of electronegative fluoride. This study aims to synthesize a chitosan-zeolite composite modified with La(III) ions to improve its fluoride adsorption. Synthesized and modified composites were characterized by scanning electron microscopy, N2 physisorption, infrared spectroscopy, thermogravimetric analysis, X-ray diffraction, and point of zero charge techniques in order to determine its physicochemical and texture properties and elucidate the mechanism of fluoride adsorption. The adsorption capacity was assessed by using the Langmuir and Freundlich isotherm models. According to the adsorption experiments, the composite modified with La (III) had a fluoride adsorption capacity of 14.3 mg g−1.