Fluoride adsorption from aqueous solution by magnetic core-shell Fe3O4@alginate-La particles fabricated via electro-coextrusion

The magnetic core-shell Fe 3 O 4 @Alg-La particles were fabricated successfully by a simple method of electro-coextrusion, and employed as an adsorbent for separation of fluoride from aqueous solution. Main factors affecting the removal of fluoride, including pH, adsorbent dosage, initial concentration, temperature and contact time were investigated. The adsorption isotherm and adsorption kinetics were studied to understand the adsorption process in detail. The experimental data were fitted well by the non-linear Freundlich isotherm and linear pseudo-second-order model, the maximum fluoride adsorption capacity was 45.230   mg/g at pH 4, 298.15   K. Thermodynamic parameters indicated that the fluoride adsorption process was feasible and spontaneous. The presence of other anions like Cl − , SO 4 2− , HCO 3 − and PO 4 3− had almost no effect on the fluoride adsorption. The adsorbent can be easily separated from the solution by a magnet. The magnetic core-shell Fe 3 O 4 @Alg-La particles before and after fluoride adsorption were studied by SEM, FTIR, EDX and XPS, which indicated that the adsorption mechanism may be related to electrostatic attraction and Lewis acid-base interaction.