Enhanced Structural Stability of Fe₃O₄/GO–PEG Nanocomposite for Ultrasonic Pretreatment Applications

The development of magnetically recoverable nanocomposites with high structural stability and surface functionality is crucial for catalytic and biocatalytic processes in aqueous environments. In this work, a Fe₃O₄/GO–PEG nanocomposite was synthesized via a co-precipitation route followed by PEG functionalization to improve dispersibility, chemical robustness, and reusability. Comprehensive characterization using XRD, FTIR, TEM, BET, VSM, DLS, TGA, and ICP–OES confirmed the formation of monodisperse Fe₃O₄ nanoparticles (7 - 15 nm) uniformly anchored on GO sheets. XRD and FTIR analyses verified the Fe–O–C coordination and amide (–CO–NH–) linkages, indicating successful PEG grafting. The nanocomposite exhibited a mesoporous structure (6 - 9 nm) with a high surface area (137.4 m²·g⁻¹) and retained superparamagnetic behavior (Mₛ = 55.8 emu·g⁻¹), enabling rapid magnetic separation. DLS and zeta potential measurements demonstrated that PEG-induced steric stabilization effectively suppressed aggregation and reduced Fe leaching by 53% under ultrasonic conditions. The synergistic effect of GO support and PEG coating provides enhanced colloidal stability, chemical durability, and magnetic recyclability, making the material a promising platform for ultrasonic-assisted delignification and enzyme immobilization. This study establishes a clear structure–stability–function correlation in Fe₃O₄/GO–PEG systems, elucidating the critical role of PEGylation in preserving magnetism while mitigating degradation during sonochemical and biocatalytic operations. HIGHLIGHTS Fe₃O₄/GO–PEG nanocomposite synthesized via co-precipitation with PEGylation PEG functionalization enhanced dispersion stability and reduced Fe leaching FTIR confirmed Fe–O–C coordination and amide linkages in the hybrid structure VSM and BET revealed superparamagnetism and mesoporous surface retention Composite applicable for ultrasonic delignification and enzyme immobilization GRAPHICAL ABSTRACT