Catalytic ozonation of norfloxacin using Co3O4/C composite derived from ZIF-67 as catalyst

In this study, Co3O4-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 Co3O4-C composite remained similar polyhedrons structure of ZIF-67, suggesting that Co3O4 was well-dispersed in Co3O4-C composite. Furthermore, a larger amount of surface carbon-oxygen functional groups were distributed on Co3O4-C composite, which resulted in the diversification of active sites for catalytic ozonation reaction. NOF degradation and mineralization could be effectively enhanced in Co3O4-C/O3 process. Moreover, NOF mineralization by catalytic ozonation strongly depended on the solution pH, while other operational conditions, such as O3 concentration and catalyst dosage had not obvious influence on it. Co3O4-C composite could significantly accelerate O3 decomposition to produce active free radicals (such as •OH), which enhanced the mineralization of NOF. The possible catalytic mechanism of Co3O4-C composite was proposed. Additionally, after five consecutive use of Co3O4-C composite in catalytic ozonation process, there was no obvious decrease in TOC removal efficiency, indicating a stable performance of Co3O4-C composite, which was suitable for the catalytic ozonation for wastewater treatment.