Although the ozonation of common antibiotics, such as ciprofloxacin (CIP), in water has been well studied, the influence of bromide that is present at high levels in seawater, is essentially unknown. In this study, we investigated the effect of bromide on the reaction kinetics, formation of transformation products (TPs), reaction pathways, and toxicity in the ozonation of CIP. Bromide significantly accelerated the transformation of CIP by ozone, likely due to the formation of reactive bromine species. Based on time-of-flight high-resolution mass spectrometry and suspect screening, a total of 26 TPs, including 13 previously unknown products, were identified in artificial seawater, while only 9 of them were found in pure water without bromide. The transformation of CIP in artificial seawater was found to involve four major processes: oxidation at the piperazinyl moiety with the addition of hydroxyl group(s) to the ring and ring cleavage, oxidation at the quinolone moiety, and bromination. In contrast, the ozonation of CIP in pure water occurred only at the piperazinyl moiety. In addition, bromide also enhanced the removal of toxicity towards Escherichia coli. This study suggests that careful consideration should be taken when using ozone to treat antibiotics contaminated water in the presence of bromide.

尽管已经很好地研究了常见抗生素（例如环丙沙星（CIP））在水中的臭氧氧化作用，但基本上未知海水中存在的溴化物的影响。在这项研究中，我们研究了溴化物对CIP臭氧氧化反应动力学，转化产物（TPs）的形成，反应途径和毒性的影响。溴化物可能会由于反应性溴物质的形成而大大促进了CIP臭氧的转化。基于飞行时间高分辨率质谱和可疑筛查，在人造海水中总共鉴定出26种TP，包括13种先前未知的产物，而在纯净水中却没有溴化物，其中只有9种被发现。发现人工海水中CIP的转化涉及四个主要过程：在哌嗪基部分进行氧化，在环和环裂解上加成羟基，在喹诺酮部分进行氧化和溴化。相反，纯水中的CIP臭氧化仅发生在哌嗪基部分。此外，溴化物还增强了对大肠杆菌。这项研究表明，在存在溴化物的情况下，使用臭氧处理被抗生素污染的水时应谨慎考虑。