Insight into H2O2-mediated catalytic ozonation of cyclophosphamide by zinc peroxide

Abstract

Metal peroxides, owing to their ability to produce H2O2 in situ, are used for photocatalysis, ozonation, and oxidation of emerging contaminants (ECs) in wastewater. In the present study, catalytic ozonation of ZnO2 was investigated for the first time to our knowledge. The catalytic decomposition of O3 molecules to reactive oxygen species (ROS) was a dominant factor governing the degradation and mineralization of CYP by ZnO2/O3. Percent degradation of CYP by O3 and ZnO2/O3 was 17 and 99, respectively, implying that catalyst enhances the degradation of micropollutants under O3. The transformation products (TPs) of CYP formed after treatment with O3 and ZnO2/O3 as determined by HPLC-MS proves that O3 transforms CYP to still toxic and persistent transformation products (TPs) whereas by ZnO2/O3 significant decrease in TPs was observed suggesting that ZnO2/O3 not only degrades both CYP and TPs. CYP-degradation studies in presence of t-BuOH, MeOH and benzoquinone by ZnO2/O3 proved that OH. in bulk and on the surface of the catalyst and .O2- play significant roles in degrading and mineralizing CYP. CYP-degradation efficiency by ZnO2/O3 was compared to that by ZnO, CaO2, MgO2 and peroxonation, and ZnO2/O3 proved to be more relevant for real-time applications. To study ZnO2/O3 degradation capacity for real-scale applications, tertiary effluents from wastewater spiked with lamotrigine, bezafibrate, valsartan, iohexol, CYP and its TPs were investigated. A significant increase (75–99%) in degradation of the drug mixture was observed by ZnO2/O3 compared to O3 alone, demonstrating the former's potential suitability for effluent-treatment applications.