Rapid and highly efficient adsorptive removal of doxycycline from water using a reduced graphene oxide–cobalt oxide nanocomposite

Doxycycline (DOX), a widely used antibiotic, poses a significant environmental risk due to its potential contamination of water resources. In this study, a reduced graphene oxide–cobalt oxide (rGO-Co 3 O 4 ) nanocomposite was synthesized and evaluated for efficient DOX removal from water-based solutions. The nanocomposite was thoroughly characterized using FTIR, XRD, SEM and EDX providing detailed insights into its structure and morphology. A series of adsorption experiments were performed to assess the impact of contact time, adsorbent loading, solution pH, initial DOX concentration, and temperature on the adsorption process. The rGO-Co 3 O 4 nanocomposite achieved 99% DOX removal within 12 min at neutral pH with a low adsorbent dosage of 0.25 g/L. Kinetic analysis indicated pseudo-second-order behavior, while isotherm studies showed better fitting to the Freundlich model, suggesting multilayer adsorption. The maximum adsorption capacity at 25 °C was 7.88 mg/g. Thermodynamic evaluation indicates that the adsorption occurs spontaneously and is endothermic in nature, accompanied by an increase in disorder at the solid–liquid interface. Additionally, the material exhibited excellent reusability over eight consecutive cycles, demonstrating its promise as a sustainable, high-performance adsorbent for the quick and efficient remediation of antibiotic-contaminated water.