The growing production and extensive use of pharmaceuticals have resulted in their frequent detection in various environmental compartments. Ciprofloxacin (CIP), a fluoroquinolone antibiotic used for treating respiratory, urinary tract, and gastrointestinal infections, is increasingly present in aquatic environment due to its intensive medical application and incomplete removal in conventional treatment systems. In response to the tightening of environmental regulations aimed at reducing pollutant emissions, the development of efficient and sustainable methods for eliminating pharmaceutical contaminants has become a priority. Among promising approaches, advanced oxidation processes stand out for their ability to generate highly reactive radicals under relatively mild operating conditions, enabling effective degradation of persistent pollutants.
In this study, the photodegradation of CIP was investigated under simulated sunlight using heterogeneous photocatalysis. Degradation kinetics was monitored with particular attention devoted to several operational parameters: catalyst type (ZnO and TiO₂), catalyst loading (0.5–5.0 mg/mL), initial CIP concentration (0.025–0.125 mmol/L), and photoreactor design. Complete removal of CIP was achieved within 60 min using both photocatalysts. The results indicate that increasing catalyst loading slightly decreases removal efficiency within the tested range, with the highest performance obtained at 0.5 mg/mL. Similarly, increasing initial CIP concentration led to a moderate reduction in degradation efficiency, with the most effective removal observed at 0.025 mmol/L. The higher photocatalytic performance observed with the xenon lamp reactor was attributed to its UVA light intensity, which was 26.1 times greater than that of the reactor with the halogen lamp. Finally, the reusability of ZnO was assessed over three successive cycles under identical conditions. A gradual decline in efficiency was observed, likely due to the adsorption of degradation products blocking active sites on the photocatalyst surface.
Acknowledgements
The financial support of the Ministry of Science, Technological Development and Innovation of the Republic of Serbia (Grants No. 451-03-137/2025-03/ 200125 & 451-03-136/2025-03/200125).
