Photochemical degradation kinetics and mechanisms of norfloxacin and oxytetracycline
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RESEARCH ARTICLE
Photochemical degradation kinetics and mechanisms of norfloxacin and oxytetracycline Honghai Xue 1 & Ming Li & Binshuo Liu 1 & Qingling Meng 1 Received: 12 May 2020 / Accepted: 6 October 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The photochemical degradation of norfloxacin (NOR) and oxytetracycline (OTC) was investigated under ultraviolet (UV) irradiation. The results indicated that both NOR and OTC can be degraded, whereas the reaction rates decreased with increasing concentration of NOR and OTC. The degradation rates of NOR and OTC (5 μM) were 0.0256 min−1 and 0.0140 min−1. Acidic conditions inhibited the degradation of NOR; however, alkaline conditions promoted the degradation of NOR. Meanwhile, the degradation of OTC was promoted by alkaline conditions but hardly affected by acidic conditions. In real water, the degradation of NOR was slower than that in ultrapure water, whereas the degradation of OTC was faster in real water. NOR produced five degradation products, with pathways mainly comprising hydroxylation and defluorination. OTC produced three degradation products, with its degradation pathways mainly consisting of deep oxidation, dehydration, and secondary alcohol oxidation. During the UV photolysis process, the mineralization rates of NOR and OTC (5 μM) were 9.83% and 6.87% after 60-min irradiation. This work can provide a theoretical basis for understanding the migration and transformation behavior of antibiotics in the water environment. Keywords Norfloxacin . Oxytetracycline . Photolysis . Degradation . Kinetics . Mechanism
Introduction Antibiotics, such as quinolones, tetracyclines, and macrolides, are frequently used in the aquaculture industry, not only for disease treatment but also for growth (Chen et al. 2008; Kim et al. 2009; Liang et al. 2015). Most antibiotics do not readily metabolize in human body and excreted as parental compounds (Kovalakova et al. 2020); they have been identified in surface water, seawater, soil, and sediment worldwide (Chen et al. 2020; Han et al. 2020; Hopanna et al. 2020). Frequent occurrences of antibiotics in the environment could increase the resistance of bacteria to drugs and spread the antibiotic resistance genes into the environment, consequently threat human health (Han et al. 2020; Snowberger et al. 2016; Responsible editor: Sami Rtimi * Qingling Meng [email protected] 1
Key Laboratory of Songliao Aquatic Environment, Ministry of Education, Jilin Jianzhu University, Changchun 130118, People’s Republic of China
Wang and Zhuan 2020); therefore, it is essential to investigate the degradation behavior of antibiotics in waters. Norfloxacin (NOR) and oxytetracycline (OTC) are two commonly used antibiotics, both of which are persistent against biological degradation due to pharmaceutical activity (Zhang et al. 2012; Zhang et al. 2019). Photolysis was demonstrated to be a predominant elimination pathway of antibiotics in sunlit surface waters due to strong photo-oxidation capability (Ge et al. 2015). It is a cl
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