Effects of environmental factors on the fleroxacin photodegradation with the identification of reaction pathways. (December 2022)

• Record Type: Journal Article
• Authors: Huang, Ruisi; Cao, Hongyu; Huang, Ting; Li, Hongjiang; Tang, Qian; Wang, Lihao; Zheng, Xuefang
• Is Part Of: Chemosphere. Volume 308:Part 2(2022)
• Publication Date: 2022-12
• Subjects: Fleroxacin -- Photodegradation -- Transition state theory -- Reaction pathways -- Density functional theory; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2022.136373
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: The abuse of fluoroquinolones (FQs) antibiotics leads to bacterial resistance and environmental pollution, so it is of great significance to verify the decomposition mechanism for eliminating antibiotic efficiently and conveniently. The effects of various environmental factors and the fleroxacin (FLE) photodegradation mechanisms were investigated by high-performance liquid chromatography–tandem mass spectrometry (HPLC-MS), UV–Vis absorption spectroscopy, fluorescence spectroscopy and quantum chemical calculation. Six possible photodegradation reaction paths on T1 (excited triplet state) were proposed and simulated. The departure of the piperazine ring and the substitution of F atom at C-6 position by OH group were determined as the main reactions based on the reaction rates and energy barriers of each path. The multi-pathway reactions resulted in the fastest photodegradation rates of FLE at pH 6–7 than other pH conditions. NaN3 would promote FLE photodegradation by inhibiting the reverse reaction of the separation process of F atom at C-8 and the generation of biphenyl molecules, which was a novel and distinctive phenomenon in this report. ·OH would rapidly combine with the free radicals generated in photolysis processes and made a great contribution to FLE photodegradation. Ca 2+, Mg 2+ and Ba 2+ could stabilize the carboxyl group to impede the photo-competitive process of the decarboxylation reaction, while NO3 − could generate reactive oxygen species to promote photodegradation. Graphical abstract: Image 1 Highlights: The environmental factors effects on six photolysis paths were investigated. The piperazine departure and the F replacement at C-6 were the main reactions. The synergy of Path-3/5/6 resulted in the highest FLE photolysis rate at pH 6–7. NaN3 promoted FLE photodegradation by impeding the Path-4 reverse reaction. Various cations inhibited the decarboxylation to promote FLE photolysis.