Mechanistic insight into enhanced florfenicol degradation by micro-nano bubbles ozonation in mariculture wastewater.

Intensive mariculture relies heavily on antibiotics, such as florfenicol (FF), which pose ecological risks due to their persistence, bioaccumulation, and promotion of antibiotic resistance. Conventional macro-bubbles ozonation (MaB-O3) faces challenges in effectively degrading FF due to poor ozone mass transfer and limited reactivity with FF (kO3 < 10 M-1 s-1), especially in high salinity and complex organic wastewater. This study introduces micro-nano bubbles ozonation (MNB-O3) as an efficient alternative, achieving 99.13 ± 0.08% removal of FF in actual mariculture wastewater, significantly surpassing MaB-O3. The enhanced performance is attributed to improved ozone dissolution and elevated generation of reactive oxygen species (ROS). The pseudo-first-order rate constant for MNB-O3 was determined to be 3.9 times that of MaB-O3 in ultrapure water and remained 2.4 times greater in artificial seawater. Alkaline conditions further promoted ROS formation and FF degradation. Radical probe experiments and electron paramagnetic resonance (EPR) analyses verified the predominant role of ROS. Degradation pathways, primarily involving defluorination, dechlorination, and hydroxylation, were elucidated using liquid chromatography-quadrupole time-of-flight tandem mass spectrometry (LC-QTOF-MS) and density functional theory (DFT) calculations. Luminescent bacteria assays confirmed an overall reduction in acute toxicity after treatment. These findings position MNB-O3 as a promising technology for antibiotic abatement in mariculture effluents.