Hole-driven solar photocatalysis of ofloxacin using cellulose nanocrystal-supported TiO2 nanocomposites

The persistence of fluoroquinolone antibiotics, such as ofloxacin, in aquatic environments presents a growing challenge and public health concern due to their resistance to biodegradation and their role in antimicrobial resistance. In this study, a sustainable and effective photocatalytic system based on cellulose nanocrystal-supported TiO2 (CNC–TiO2) nanocomposites was created to degrade ofloxacin under direct sunlight. The nanocomposite exhibited improved optical characteristics, with a lower band gap (2.99 eV) compared to pristine TiO2 (3.29 eV), thereby promoting better solar light absorption. Under optimized conditions (250 mg/L catalyst dosage, pH 7, 300 min irradiation), ~ 98.6% ofloxacin degradation was achieved, following pseudo-first-order kinetics. Reactive-species scavenging experiments showed that photogenerated holes (h⁺) governed the degradation process, while superoxide radicals (•O2⁻) provided a secondary oxidative route. LC–MS/MS analysis confirmed multiple degradation pathways and finally led to mineralization, with 73.82% TOC removal. The catalyst showed promising laboratory-scale performance in OFX-spiked complex wastewater matrix (~ 94% degradation) and retained 81.2% degradation efficiency after five reuse cycles. The findings indicate the potential of CNC–TiO2 nanocomposites as reusable photocatalysts for sunlight-driven antibiotic degradation in complex wastewater matrices. CNC–TiO2 nanocomposites enable efficient solar-driven degradation of ofloxacin. CNC serves as a functional support, reducing the apparent band gap (2.99 eV) and suggesting improved sunlight response. CNC incorporation improves catalyst recovery. Photogenerated holes were identified as the dominant reactive species. ~98.6% degradation and ~73.82% mineralization achieved under sunlight. Promising degradation achieved in OFX-spiked hospital wastewater (~94%). Catalyst exhibits good stability and reusability over multiple cycles.