Preparation of Cs-Fe@Fe₃O₄ nanocomposite as an efficient and recyclable adsorbent for azo dyes removal

As an effective and in situ purification strategy, adsorption technology has drawn much attention and recently the utilization of biomass substrate has been regarded as a promising way to enhance the adsorption performance and reduce cost. In this study, chitosan was applied as matrix and the magnetic Fe-crosslinked chitosan (CS-Fe@Fe₃O₄) composite was obtained through a chelation procedure with cheap and environmentally friendly chitosan and iron salts. Then, the resultant CS-Fe@Fe₃O₄ composites were characterized by scanning electron microscopy, transmission electron microscopy, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and thermogravimetric analysis. The sorption and desorption of methyl orange (MO), a common type of azo dye, on CS-Fe@Fe₃O₄ composite was systematically studied to understand its availability for dyeing wastewater. The results revealed that CS-Fe@Fe₃O₄ composites could efficiently remove MO in a wide pH range. The mixed Fe₃O₄ particles were physically mixed and almost had no negative effect on its adsorption. Moreover, the dye adsorption process was found to be controlled by the pseudo-second-order rate model and the adsorption isotherm behavior could be described by the Langmuir model. The repeatability test showed that the CS-Fe@Fe₃O₄ composites could retain its high efficiency after desorption and regeneration. In summary, the results presented herein indicated that the resultant CS-Fe@Fe₃O₄ nanocomposite with high adsorption efficiency and strong magnetic property could serve as a potential adsorbent for remediating industrial dyeing wastewater.