Mechanistic insights into surface catalytic oxidation of fluoroquinolone antibiotics on sediment mackinawite

Fluoroquinolone antibiotics (FQs) have been widely detected in the sediments due to vast production and consumption. In this study, the transformation of FQs was investigated in the presence of sediment mackinawite (FeS) under ambient conditions. Moreover, the role of dissolved oxygen was evaluated for the enhanced degradation of FQs induced by FeS. Our results demonstrated that typical FQs (i.e., flumequine, enrofloxacin and ciprofloxacin) could be efficiently adsorbed and degraded by FeS under neutral pH conditions. As indicated by the results of electron paramagnetic resonance analysis (EPR) and free radicals quenching experiments, hydroxyl radical and superoxide radical anions were identified as the dominant reactive species responsible for FQs degradation. Based on the results of product analysis and theoretical calculation, the degradation of FQs mainly occurred at the piperazine ring and quinolone structure. Our results show that FQs could be efficiently removed by FeS, which benefits understanding the transformation of antibiotics in the sediments, and even sheds light on the remediation of organic pollutants contaminated soils.