Enhancing photo-degradation of ciprofloxacin using simultaneous usage of eaq � and radOH over UV/ZnO/I- process: Efficiency, kinetics, pathways, and mechanisms

The aim of this study is to develop the process relies on the UV irradiation of ZnO and I�, i.e. UV/ZnO /I� (UZI), to create both oxidizer and reducer agents simultaneously for photo-degradation of the Ciprofloxacin (CIP). This paper shows that while applying UV irradiation, UV/ZnO and UV/I� for 20 min can lead to achieve 37.5, 58.12, and 61.4 photo-degradation of 100 mg L�1 CIP at pH 7, respectively. Moreover, the UZI treatment can provide 91.54 photo-degradation efficiency. The LC�MS analysis of the UZI effluent indicates that 10 min process was adequate to degrade CIP into simple ring-shaped metabolites while 15 min treatment, mostly of CIP intermediates were linear and biodegradable organic compounds. Furthermore, fourteen little fragments were identified in the CIP photo-degradation via UZI, during the photoreaction time of 2.5 to 20 min. Then, a pseudo first-order kinetics equation was utilized to model the observed photo-degradation process. Finally, the computational results show that the increased concentration of the CIP solution from 100 to 400 mg L�1 decreases the observed rate constant (kobs) from 0.4125 to 0.2189 min�1 while increases the photoreaction rate (robs) from 41.25 to 87.56 mg L�1 min�1. © 2019 Elsevier B.V