Comparison of visible light driven HO and peroxymonosulfate degradation of norfloxacin using Co/g-CN.

As common advanced oxidation processes, Fenton-like and peroxymonosulfate (PMS) processes have received enormous attention due to their high efficiency in the pollutants degradation. In this study, the Co/g-CN photocatalyst was prepared by facial calcination strategy and used to evaluate the behavior of the Co/g-CN/HO and Co/g-CN/PMS systems for norfloxacin (NOR) photocatalytic degradation under visible light irradiation. The composite photocatalysts exhibited better performance compared to that of pure g-CN due to the efficient separation of electron-hole pairs and visible light absorption. The Co/g-CN/PMS system possessed better photocatalytic performance than the Co/g-CN/HO system, where the degradation ratio of NOR and removal ratio of total organic carbon (TOC) were 96.4% and 54%, respectively, in 10 min. The photocatalytic mechanism was investigated using reactive species trapping experiments and electron spin-resonance spectroscopy (ESR). ⋅OH and SO were the dominant reaction species in the Co/g-CN/HO and Co/g-CN/PMS systems, respectively. According to the analysis of the NOR degradation path, SO could attack the C-H bond on the piperazine ring or quinolone group of NOR, which resulted in it more active and accelerating the destruction of NOR with SO and ⋅OH. The destruction of the quinolone group was the main pathway in the HO process, while the destruction of the piperazine ring was the main pathway in the PMS process. In sum, the Co/g-CN/PMS process had a higher photocatalytic activity and economic applicability.