Adsorption of fluoride ion on Al/La modified acidified attapulgite composite materials

Abstract

This study developed a novel fluoride ion adsorbent material (Al/La-A) for efficient removal of fluoride ions in water. The crystal structure, elemental composition, surface morphology, specific surface area, thermal stability and surface electronegativity before and after modification were explored using FTIR, XRD, XPS, SEM-EDS, BET, TG-DSC, and zeta potential measurements. Results showed that the fluoride ion adsorption capacity of Al/La-A reached 130.42 mg/g, with the surface area increasing from 65.66 m2/g to 111.68 m2/g, respectively, compared to unmodified attapulgite. Al/La-A maintained excellent fluoride ion removal performance over a wide pH range, with the best adsorption at pH 2. Coexisting ion experiments indicated weak competitive adsorption effects of Cl-, SO42-, and HCO3–, with fluoride ion adsorption remaining above 100 mg/g in the presence of different concentrations of coexisting anions. After 5 adsorption–desorption cycles, Al/La-A exhibited strong adsorption capacity and reusability. The fitting of Langmuir adsorption model and pseudo-second-order kinetic model to the adsorption of fluoride ions on Al/La-A indicated that the adsorption of fluoride ions on Al/La-A was primarily monolayer chemical adsorption. The adsorption mechanism of fluoride ions involved electrostatic interactions, ion exchange, and coordination complexation. This study provides a new research approach for the optimal utilization of attapulgite-based adsorbent materials and the efficient removal of fluoride-containing wastewater.