Upcycled coffee waste-derived carbon nanoparticles@Ag nanostructures via microwave-assisted synthesis for efficient tetracycline photodegradation

The increasing presence of tetracycline antibiotics in aquatic environments poses serious ecological and health risks due to their persistence and potential to promote antibiotic resistance. In this study, we report a sustainable and efficient strategy for the photocatalytic degradation of tetracycline using Ag-decorated carbon nanoparticles synthesized via a rapid microwave-assisted method. The carbonaceous component was derived from spent coffee grounds, promoting a circular economic approach. Structural, optical, and vibrational analyses (UV-Vis, FTIR, Raman, TERS, and XRD) reveal significant transformations in both the carbon matrix and silver phase, enabling enhanced photocatalytic activity. The optimized hybrid nanocomposite exhibits remarkable performance, achieving 95% tetracycline degradation under simulated solar irradiation within 30 min (solar simulator AM 1.5, 0.1 W cm⁻² light intensity). Mechanism studies using optical filters and radical scavengers confirm the role of interfacial charge transfer and reactive oxygen species in the photocatalytic process. The catalyst maintains its activity over four consecutive cycles, highlighting its potential for practical applications in sustainable water remediation.