Sugarcane waste-derived carbon quantum dots–chlorophyll/bacterial cellulose composites for solar-driven antibiotic degradation

A bio-based CQDs-Chl/BC nanocomposite (NCs) was synthesized from sugarcane bagasse, sugarcane leaves, and bacterial cellulose (BC) via a green bio-construction strategy to enhance antibiotic removal through a synergistic adsorption-photocatalysis mechanism. CQDs were prepared by a microwave-assisted method, Chl was extracted from sugarcane leaves, and BC provided a renewable support matrix. The incorporation of CQDs and Chl broadened visible-light absorption and improved charge transfer, as confirmed by UV-Vis spectroscopy, FTIR, PL, TEM-EDS, and XPS analyses. Förster resonance energy transfer (FRET) and photoinduced electron transfer (PET) minimized charge recombination, while LC-MS spectra of degradation products identified transient intermediates of ciprofloxacin (CIP) and oxytetracycline (OTC), validating the proposed photocatalytic pathway. Under solar irradiation, the CQDs-Chl/BC NCs achieved near-complete degradation of CIP (98.83 ± 0.46%) and OTC (98.59 ± 0.50%) at 2 mg/L within 180 min, outperforming CQDs/BC (k = 0.01044 min^-1) and Chl/BC (k = 0.01109 min^-1), with a pseudo-first-order rate constant of 0.02642 min^-1. The composite also exhibited strong adsorption capacity, excellent recyclability, and structural stability, retaining 67.7% efficiency after five cycles, with FTIR and XPS confirming integrity post-reuse. Biotoxicity assays revealed no intrinsic antibacterial activity, underscoring its environmental safety. The novelty of this study lies in the dual biomass valorization approach, where CQDs from sugarcane bagasse and Chl from sugarcane leaves were synergistically integrated with BC to couple adsorption, photosensitization, and advanced charge-transfer processes in one photocatalyst. These findings confirm the potential of CQDs-Chl/BC NCs as a sustainable solution for visible-light-driven wastewater treatment.