Preparation and characterization of novel magnetic Fe3O4/chitosan/Al(OH)3 beads and its adsorption for fluoride

A novel magnetic bioadsorbent beads composed of Fe3O4, chitosan, and Al(OH)3 (Fe3O4/CS/Al(OH)3) was synthesized by a modified solvothermal and in-situ reaction. The composite adsorbent was characterized by Fourier-transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, and vibrating sample magnetometer, respectively. Adsorption toward F− onto Fe3O4/CS/Al(OH)3 was investigated as a function of Fe3O4 concentration, initial solution pH, adsorbent dosage, initial fluorion concentration, co-existing ions in water and initial temperature. The addition of Fe3O4 could enhance the adsorption properties of CS/Al(OH)3. The saturated adsorption capacity of magnetic Fe3O4/CS/Al(OH)3 calculated from the Langmuir isotherm model was 76.63 mg/g at 298 K. The adsorption isotherm of F− followed Langmuir isotherm model and the adsorption kinetics fitted better to the pseudo-second order kinetic model. The influence of temperature confirmed that the adsorption was spontaneous and endothermic. The magnetic Fe3O4/CS/Al(OH)3 beads could be easily separated from water under a low magnetic field.