Characterization of new sorbent constructed from Fe3O4/chitin magnetic beads for the dynamic adsorption of Cd2+ ions

Novel magnetic chitin (CM) beads were successfully prepared by in situ synthesis of Fe3O4 nanoparticles in regenerated chitin beads (Ch beads) for the packing fixed-bed columns. The interpenetrated porous structure in the regenerated Ch beads at the swollen state served as templates for the inorganic nanoparticle preparation. The morphology and structure of the hybrid nanomaterials were characterized with scanning transmission electron microscopy, transmission electron microscopy, thermal gravimetry analysis, X-ray diffraction, and Fourier transform infrared spectroscopy, and the Cd2+ ion adsorption capacity of the CM beads was determined by UV-Vis spectrophotometry. The results revealed that the CM beads exhibited efficient adsorption of Cd2+ ions in the aqueous solution, as a result of the microporous structure, large surface area, and affinity for metal ions. The equilibrium process of this fixed-bed column was well described by Thomas and Bohart-Adams model, indicating that the external mass transfer was the rate-limiting process at the beginning of adsorption. The adsorption equilibrium was better described by the bed depth-service time model, indicating that the Cd2+ uptake could be controlled by external mass transfer at the beginning and intraparticle diffusion at a later stage of the adsorption. The CM beads loaded with the Cd2+ could be regenerated and reused easily. The CM beads should have potential applications in the chromatography packing and adsorbent both at the laboratory and industrial scales.