The wide occurrence of fluoroquinolones (FQs) in aquatic environments has aroused increasing concern about their potential adverse effects on human health. In this study, an emerging advanced oxidation process, i.e., the Medium-Pressure Ultraviolet/Peracetic Acid (MPUV/PAA) process, was used to degrade FQs (e.g., levofloxacin (LEV) and norfloxacin (NOR) ). The results have shown the compared with the MPUV process alone and the PAA process alone, the MPUV/PAA process significantly promoted the FQs degradation due to the considerable contribution of reactive radicals. The solution pH was a key factor affecting the efficiency of MPUV/PAA. Rapid FQs degradation via the MPUV/PAA process was achieved within a wide range of pH values (5–9), and higher pH values were more favorable for the reaction. The rate of PAA photolysis, which resulted in the formation of reactive radicals, increased with pH, as evidenced by the observed increase in the molar absorption coefficient of PAA (εPAA). Electron paramagnetic resonance (EPR) tests also indicated that the generation of ROS was significantly enhanced when the pH increased from 5 to 7, and at pH 9, a large amount of ●OH were possibly consumed by PAA to form organic radicals, leading to a decrease in the ●OH signal. Furthermore, ●OH was primarily responsible for FQs degradation at pH 5, whereas organic radicals were primarily responsible for the degradation at pH 7 and 9. Besides, the slight impacts of Cl– and CO32−/HCO3– on FQs removal were observed. The demethylation and the piperazine ring cleavage were the main degradation pathways of LEV by direct MPUV photolysis, and the reactive radicals mainly attacked the piperazine ring. OH/F substitution and direct defluorination were the main degradation pathways of NOR by direct MPUV photolysis, and the oxidation of NOR by reactive radicals mainly caused the transformation of the quinolone ring and piperazine ring. This study is the first report that evaluates the feasibility and performance of FQs by MPUV/PAA, which provide a promising strategy for the FQs elimination from aquatic environment.

Comprehensive understanding of fluoroquinolones degradation via the MPUV/PAA process: Radical chemistry, matrix effects, and degradation pathways

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