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

Abstract

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.