Comparison of visible light driven H2O2 and peroxymonosulfate degradation of norfloxacin using Co/g-C3N4

Abstract

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-C₃N₄ photocatalyst was prepared by facial calcination strategy and used to evaluate the behavior of the Co/g-C₃N₄/H₂O₂ and Co/g-C₃N₄/PMS systems for norfloxacin (NOR) photocatalytic degradation under visible light irradiation. The composite photocatalysts exhibited better performance compared to that of pure g-C₃N₄ due to the efficient separation of electron-hole pairs and visible light absorption. The Co/g-C₃N₄/PMS system possessed better photocatalytic performance than the Co/g-C₃N₄/H₂O₂ 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 SO₄^⋅- were the dominant reaction species in the Co/g-C₃N₄/H₂O₂ and Co/g-C₃N₄/PMS systems, respectively. According to the analysis of the NOR degradation path, SO₄^⋅- 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 SO₄^⋅- and ⋅OH. The destruction of the quinolone group was the main pathway in the H₂O₂ process, while the destruction of the piperazine ring was the main pathway in the PMS process. In sum, the Co/g-C₃N₄/PMS process had a higher photocatalytic activity and economic applicability.

Keywords: Co/g-C(3)N(4); Co/g-C(3)N(4)/H(2)O(2) process; Co/g-C(3)N(4)/PMS process; Norfloxacin; Photocatalysis.