Fe₃O₄/Graphene Oxide/Chitosan Nanocomposite: A Smart Nanosorbent for Lead(II) Ion Removal from Contaminated Water

A new graphene oxide (GO) nanocomposite that contains chitosan, a biological polymer, combined with a magnetic nanoparticle inorganic material (Fe₃O₄) was successfully prepared and applied for the adsorption of Pb(II) from aqueous solutions. The structural and morphological properties of the GO/Fe₃O₄/CS (GFC) nanocomposites were characterized by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Influent factors for Pb(II) adsorption, including the contacting time, pH of the working medium, working temperature, and adsorbent dosage on the adsorption efficiency, have been optimized. Under optimized conditions, the adsorption isotherm results indicated that the Langmuir model provided a better description for the adsorption of Pb(II) onto the GFC nanosorbent than the Freundlich model. The maximum adsorption capacity (q_max) was 63.45 mg g^-1. The pseudo-second-order kinetic model (R² = 0.999) was fitted with the experimental results, implying that the adsorption of Pb(II) onto GFC is a chemical process. The thermodynamic studies demonstrated the exothermic nature of the adsorption process. Another advantage of the GFC nanosorbent for Pb(II) removal is its capability to be easily recovered under the use of an external magnet and subsequently regenerated. Our work demonstrated that the removal efficiency was stable after several regeneration cycles (i.e., approximately 12% reduction after four successive adsorption-desorption cycles), implying that the GFC nanosorbent exhibits satisfactory regeneration performance. Therefore, with high removal efficiency, high adsorption capacity, and stable reusability, the GFC nanocomposite is a remarkable application potential adsorbent for the in situ treatment of Pb(II) ion-containing aqueous solutions.