Sorbitol-modified graphene oxide-iron oxide nanocomposite for efficient doxycycline removal: mechanistic and kinetic insights

Abstract

This study reports the synthesis of a novel, eco-friendly and highly effective sorbitol-functionalized graphene oxide-iron oxide (GO/Fe-SBT) nanocomposite for the enhanced removal of doxycycline (DOX) from aqueous solutions. Comprehensive characterization (FTIR, XRD, SEM, TEM, and EDX) confirmed the successful incorporation of iron oxide nanoparticles and sorbitol into the GO matrix, leading to enhanced stability and dispersion as well as abundant active sites. The GO/Fe-SBT nanocomposite exhibited exceptional adsorption performance, achieving a maximum DOX removal efficiency of 96.82% within 5 minutes at an initial concentration of 0.2 mg L⁻¹. The equilibrium capacity reached 41.61 mg g⁻¹ under optimal conditions (pH 5, adsorbent dosage of 0.1 g L⁻¹, temperature of 25 °C). The adsorption process followed pseudo-second-order kinetics and the Freundlich isotherm model, indicating chemisorption-dominated multilayer adsorption. The high removal efficiency was attributed to synergistic mechanisms, including electrostatic interactions, hydrogen bonding, π–π stacking and iron chelation. Moreover, the nanocomposite demonstrated excellent reusability, maintaining over 94% of its initial removal efficiency after seven consecutive adsorption–desorption cycles. Overall, this work introduces a rapid, low-dose, sustainable and highly effective adsorbent with strong potential for scalable mitigation of antibiotic contamination in aqueous environments.