A green and sustainable approach using Thuja occidentalis-mediated Fe3O4 QDs decorated on rGO NSs for enhanced photocatalytic degradation of antibiotics

Abstract

Emerging pharmaceutical contaminants such as antibiotics, personal care products, and anti-inflammatory drugs have become major environmental concerns due to their persistence and toxicity. In this study, Fe₃O₄ quantum dots supported on reduced graphene oxide nanosheets (Fe₃O₄ QDs–rGO NSs) were successfully synthesized via a green hydrothermal route using Thuja occidentalis leaf extract as a natural reducing and capping agent. The resulting nanocomposites (NCs) exhibited a high surface area (168 m² g⁻¹) and mesoporous structure (average pore size ≈14 nm), favouring pollutant adsorption and charge separation. Under visible-light irradiation, the Fe₃O₄ QDs–rGO NSs demonstrated superior photocatalytic performance toward pharmaceutical contaminants, achieving degradation efficiencies of 94.5% for ciprofloxacin (CIP), 76.2% for ibuprofen (IBU), and 90.7% for tetracycline (THC) within 120 min at an optimum catalyst dose of 5 mg and neutral pH ≈ 7. The apparent first-order rate constants (k) were 0.024, 0.017, and 0.012 min⁻¹ for CIP, IBU, and THC, respectively. The nanocomposite retained over 90% of its photocatalytic efficiency after five reuse cycles, confirming its excellent stability and recyclability. The enhanced activity is attributed to the synergistic interaction between Fe₃O₄ QDs and rGO, which promotes efficient charge carrier separation and radical generation. These results highlight the potential of bioinspired Fe₃O₄ QDs–rGO NSs as an efficient, sustainable photocatalyst for wastewater remediation applications.