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

A novel magnetic bioadsorbent beads composed of Fe 3 O 4 , chitosan, and Al(OH) 3 (Fe 3 O 4 /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 Fe 3 O 4 /CS/Al(OH) 3 was investigated as a function of Fe 3 O 4 concentration, initial solution pH, adsorbent dosage, initial fluorion concentration, co-existing ions in water and initial temperature. The addition of Fe 3 O 4 could enhance the adsorption properties of CS/Al(OH) 3 . The saturated adsorption capacity of magnetic Fe 3 O 4 /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 Fe 3 O 4 /CS/Al(OH) 3 beads could be easily separated from water under a low magnetic field.