Insights into the relationship between regulation of oxygen vacancy and singlet oxygen generation in peracetic acid activation

Abstract

Peracetic acid (PAA) has shown good potential in advanced oxidation techniques, but the mechanism regulating the generation of non-radical species in peracetic acid has not been clarified. Herein, Ov-Co3O4/C-x was prepared by pyrolysis of ZIF-L precursors at different temperatures to achieve the regulation of oxygen vacancy concentration and used for the degradation of sulfamethazine (SMT) by activated PAA. When x = 350 °C, the prepared Ov-Co3O4/C-350 with the highest oxygen vacancy content had the highest SMT removal efficiency and the highest rate constant(kobs), which degraded SMT by 99.6 % within 30 min. The role of oxygen vacancies(OVs) on the surface of Ov-Co3O4/C-350 was investigated using quenching experiments, Electron Paramagnetic Resonance (EPR) and X-ray Photoelectron Spectroscopy (XPS) techniques. The results showed that oxygen vacancy on the metal oxide surface can be converted into more reactive oxygen(O*), and surface OVs of Ov-Co3O4/C-350 enable efficient capture of PAA, thus generating 1O2 and R-O•. The higher the content of oxygen vacancies is, the more 1O2 is produced, while concentration of R-O• was not significantly correlated with oxygen vacancy content. Furthermore, the degradation pathway of SMT was predicted through density functional theory (DFT) calculations and identifications of intermediates, indicating that electron-rich sites such as aromatic rings and S-N bonds in the SMT molecule are more easily oxidized by reactive species. Besides, due to the low biotoxicity of the degradation products of the Ov-Co3O4/C-350/PAA system, the reaction can effectively reduce the biotoxicity and developmental toxicity. This study provides a controllable surface property strategy for a new idea in PAA-based AOP.