Surface-Engineered Fe₃O₄/Graphene Oxide/Polymer Magnetic Nanocomposites for Efficient and Reusable Removal of Pb²⁺ and Cd²⁺ from Wastewater

Abstract The development of efficient and recyclable adsorbents for heavy metal removal remains a critical challenge in wastewater treatment. In this study, surface-engineered Fe₃O₄ based magnetic nanocomposites functionalized with graphene oxide (GO) and chitosan were synthesized and evaluated for the adsorption of Pb²⁺ and Cd²⁺ ions from aqueous solutions. Fe₃O₄ nanoparticles were prepared via a co-precipitation method and subsequently integrated with GO sheets, followed by polymer functionalization to introduce abundant oxygen and nitrogen containing functional groups. Structural and physicochemical characterization using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning and transmission electron microscopy (SEM/TEM), Brunauer–Emmett–Teller (BET) surface analysis, and vibrating sample magnetometry (VSM) confirmed the successful formation of a porous, magnetically responsive nanocomposite. Batch adsorption experiments conducted under varying conditions of pH 2–8, contact time of 0–120 minutes, initial metal ion concentration of 10–200 mg L⁻¹, and temperature of 298–318 K revealed that the adsorption process followed the Langmuir isotherm model, with maximum adsorption capacities of 182.4 mg g⁻¹ for Pb²⁺ and 136.7 mg g⁻¹ for Cd²⁺. Kinetic analysis showed that the adsorption followed a pseudo-second-order model, indicating chemisorption. Thermodynamic parameters confirmed that the adsorption was spontaneous and endothermic. Notably, the nanocomposite retained over 85% efficiency after six adsorption–desorption cycles, demonstrating excellent reusability. The enhanced performance is attributed to the synergistic effects of GO and chitosan functionalization, providing high surface area and abundant active sites. These findings suggest that the developed nanocomposite is a promising candidate for sustainable wastewater treatment.