Urea-Modified Graphene Oxide (GO-Ur): Adsorption Mechanism for Methylene Blue

This study developed urea-modified graphene oxide (GO-Ur) for efficient methylene blue (MB) adsorption. Characterization confirmed that urea modification introduced amino and hydroxyl groups, enhancing the material’s surface properties. GO-Ur achieved a high MB adsorption capacity of 367.37 mg/g under optimal conditions (the adsorption tests used 0.01 g of adsorbent, 50 mL of 80 mg/L MB solution (pH 9), a temperature of 25 °C, and a contact time of 120 min), driven by a synergistic mechanism of hydrogen bonding, electrostatic attraction, and π-π stacking. The adsorbent also demonstrated excellent reusability, with only a 0.37% capacity loss after 5 cycles of adsorption–desorption processes, and outperformed many reported adsorbents in both capacity and equilibrium time. These results highlight GO-Ur as a promising material for MB wastewater treatment.