Sustainable photocatalytic degradation of antibiotic norfloxacin using microfibrillated cellulose@ZnO nanocomposites

Antibiotics from the fluoroquinolone class, such as norfloxacin (NOR), are emerging contaminants with significant environmental and human health impacts. Their safe degradation from water remains a global challenge due to their persistence, lack of biodegradability, and ability to induce resistant bacteria. To the best of our knowledge, for the first time, this work reports the development of highly efficient photocatalytic degradation of NOR using environmentally friendly microfibrillated cellulose@ZnO (MFC@ZnO) photocatalysts. Immobilization of ZnO nanoparticles on MFC has played a crucial role in controlling the particle dimensions of ZnO, keeping them around tens of nanometers. The impact of radiation (UV-A, UV-C, and simulated solar light) on NOR degradation efficiency was investigated. Additionally, the effects of catalyst dosage (0.125-0.5 g L⁻<sup>1</sup>), NOR concentration (5-20 mg L⁻<sup>1</sup>), and degradation pH (pH = 5 to 10) were investigated. LC-MS was used to identify degradation intermediates. The results showed over 94% degradation in 40 min via UV-Vis and 90% in 10 min via HPLC, and recyclability tests indicated MFC0.1@ZnO composites can maintain over 95% NOR degradation efficiency after five consecutive 60-min cycles. The highest NOR degradation efficiency was achieved in a significantly reduced time among metal oxide semiconductors (MOS)-based photocatalysts, thus opening new perspectives for the development of eco-friendly photocatalysts, especially towards emerging pollutant degradation.