Highly efficient photocatalytic environmental remediation of MET over Z-Co3O4/K7HNb6O19 Z-scheme heterojunction with controllable hierarchical peony flower-like morphology using Co-ZIF-67 as a template

Abstract

Metformin (MET) is an oral anti-glucose medication, which can not be removed effectively by traditional wastewater treatment technology. Herein, we fabricated for the first time highly active Z-scheme heterogeneous photocatalysts Z-Nb-X by combining Co-ZIF-67 derived Co3O4 skeleton material with Lindqvist type PONb (K7HNb6O19) during a simple solvothermal. The obtained Z-scheme photocatalysts can significantly remove emerging contaminant metformin from effluent with an optimal removal efficiency of 63.8% within 7 min over the sample Z-Nb-0.8, which exhibits superior performance in comparison with photocatalytic systems reported, and has good stability and recoverability. The highly boosted photocatalytic degradation efficiency is attributed to a Z-scheme heterojunction constructed and hierarchical peony flower-like structure, which not only improved the photogenerated interfacial charge transfer but also greatly restrained electron-hole recombination. For MET removal process, three possible degradation pathways were unraveled according to the identification of intermediates. Additionally, the toxicity evaluation of intermediates was investigated, which shows that our prepared composites can reduce the toxicity of MET through the photocatalytic route. This work affords a new idea for the development of highly efficient and recyclable photocatalysts, which may be helpful to the extended application of POM-based composites in the environmental remediation of wastewater.