Fluoride removal from aqueous solutions using alginate beads modified with functionalized silica particles

Abstract

Fluoride in water and wastewater is considered a dangerous contaminant and in drinking water has a profound effect on teeth and bones. In this study, the synthesized controllable morphology silica particles were functionalized with N-(2-aminoethyl)-3-aminopropyl tri‑methoxy silane and used for the fabrication of alginate-silica composites for fluoride removal from aqueous solutions. The characterization of silica particles was performed using SEM, XRD, FTIR, and Zeta-potential analyses. The prepared particles were amorphous with positive surface charge, and had a narrow size distribution (300±5 nm). The results of the mechanical resistance analysis showed that the reinforced silica-alginate bead had remarkable stability, and only less than 10% of silica-alginate beads were damaged after incubation for 48 h. In the adsorption experiment section, the pH value of 4.5 was obtained as the optimum value for fluoride removal. The kinetics investigation showed that all the experiments achieve their adsorption equilibrium within 2 h. The reaction rate of the process was found to follow the second-order equation. The isotherm investigation illustrated that the Langmuir model provided a better prediction of the experimental data. The maximum removal capacities of the composites were found to be 51.02 mg/g for fluoride ions. The adsorbent was regenerated and reused for 6 cycles with proper performance.