Unveil the mechanism of photosensitized fluoroquinolones enhancing chlortetracycline photodegradation under simulated sunlight: Batch experiments and DFT calculation

Jiaqi Tao; Tianyi Shen; Longfei Kang; Liqiu Zhang; Yongze Liu; Yajun Tian; Li Feng

doi:10.1016/j.envres.2023.116961

Unveil the mechanism of photosensitized fluoroquinolones enhancing chlortetracycline photodegradation under simulated sunlight: Batch experiments and DFT calculation

Environ Res. 2023 Nov 15;237(Pt 1):116961. doi: 10.1016/j.envres.2023.116961. Epub 2023 Aug 22.

Authors

Jiaqi Tao¹, Tianyi Shen², Longfei Kang¹, Liqiu Zhang¹, Yongze Liu¹, Yajun Tian³, Li Feng⁴

Affiliations

¹ College of Environment Science and Technology, Beijing Forestry University, Beijing, 100083, China.
² Key Laboratory of Microbial Technology for Industrial Pollution Control of Zhejiang Province, College of Environment, Zhejiang University of Technology, Hangzhou, 310014, China.
³ College of Environment Science and Technology, Beijing Forestry University, Beijing, 100083, China; Key Laboratory of Microbial Technology for Industrial Pollution Control of Zhejiang Province, College of Environment, Zhejiang University of Technology, Hangzhou, 310014, China. Electronic address: yajunt1991@163.com.
⁴ College of Environment Science and Technology, Beijing Forestry University, Beijing, 100083, China. Electronic address: fengli_hit@163.com.

PMID: 37619632
DOI: 10.1016/j.envres.2023.116961

Abstract

Fluoroquinolones (FQs), as the most commonly used antibiotics, are ubiquitous in the aquatic environment. The FQs' self-sensitization process could generate reactive oxygen species (ROS), which could react with other coexisting organic pollutants, impacting their transformation behaviors. However, the FQs' influences and mechanisms on the photochemical transformation of coexisting antibiotics are not yet revealed. In this study, we found ofloxacin (OFL) and norfloxacin (NOR), the two common FQs, can obviously accelerate chlortetracycline (CTC) photodegradation. In the presence of OFL and NOR (i.e., 10 μM), CTC photodegradation rate constants increased by 181.1% and 82.9%, respectively. With the help of electron paramagnetic resonance (EPR) and quenching experiments, this enhancement was attributed to aromatic ketone structure in FQs, which absorbed photons to generate ROS (i.e., ³OFL*, ³NOR*,¹O₂, and •OH). Notably, ³OFL* or ³NOR* was dominantly contributed to the enhanced CTC photodegradation, with the contribution ratios of 79.9% and 77.3% in CTC indirect photodegradation, respectively. Compared to CTC direct photodegradation, some new photodegradation products were detected in FQs solution, suggesting that ³OFL* or ³NOR* may oxide CTC through electron transfer. Moreover, the higher triple-excited state energy of OFL and NOR over DFT calculation implied that energy transfer from ³OFL* or ³NOR* to CTC was also theoretically feasible. Therefore, the presence of FQs could significantly accelerate the photodegradation of coexisting antibiotics mainly via electron or energy transfer of ³FQs*. The present study provided a new insight for accurately evaluating environmental behaviors and risks when multiple antibiotics coexist.

Keywords: Chlortetracycline; Enhancement; Fluoroquinolones; Photodegradation; Reactive oxygen species.