Catalytic ozonation of norfloxacin using CoO/C composite derived from ZIF-67 as catalyst.

In this study, CoO-carbon composite was synthesized by calcined metal organic framework (MOF) ZIF-67 and used as efficient catalysts for ozonation of norfloxacin (NOF). The MOF-derived CoO-C composite remained similar polyhedrons structure of ZIF-67, suggesting that CoO was well-dispersed in CoO-C composite. Furthermore, a larger amount of surface carbon-oxygen functional groups were distributed on CoO-C composite, which resulted in the diversification of active sites for catalytic ozonation reaction. NOF degradation and mineralization could be effectively enhanced in CoO-C/O process. Moreover, NOF mineralization by catalytic ozonation strongly depended on the solution pH, while other operational conditions, such as O concentration and catalyst dosage had not obvious influence on it. CoO-C composite could significantly accelerate O decomposition to produce active free radicals (such as •OH), which enhanced the mineralization of NOF. The possible catalytic mechanism of CoO-C composite was proposed. Additionally, after five consecutive use of CoO-C composite in catalytic ozonation process, there was no obvious decrease in TOC removal efficiency, indicating a stable performance of CoO-C composite, which was suitable for the catalytic ozonation for wastewater treatment.