Transformation of norfloxacin during the chlorination of marine culture water in the presence of iodide ions
2019
Pan, Zihan | Zhu, Yunjie | Li, Leiyun | Shao, Yanan | Wang, Yinghui | Yu, Kefu | Zhu, Hongxiang | Zhang, Yuanyuan
The antibacterial agent norfloxacin (NOR) and sodium hypochlorite (NaClO), which are both widely used in marine culture, react with each other to form the halogenated disinfection byproducts (X-DBPs). The effects of the water characteristics and iodide concentration on the reaction kinetics were investigated. The results showed that the reaction rate of NOR with NaClO increases from 0.0586 min⁻¹ to 0.1075 min⁻¹ when the iodide concentration was changed from 0 μg⁻¹ to 50 μg⁻¹. This demonstrated the enhancement of NOR oxidation in the presence of iodide ions. Four novel iodinated DBPs (I-DBPs) were identified in the marine culture water. Iodine substitutions occurred at the C3 and C8 positions of NOR. The formation mechanisms of X-DBPs in the marine culture water were proposed based on the intermediate and final products. NOR may undergo a ring-opening reaction, a de-carbonyl reaction and substitution to form intermediates and finally generate the X-DBPs. Furthermore, the predicted logKOW and logBCF values of the I-DBPs were higher than that of the Br-DBPs and Cl-DBPs. The AOX concentration in the synthetic water samples decreased in the following order: seawater (8.49 mg L⁻¹) > marine culture water (4.05 mg L⁻¹) > fresh water (1.89 mg L⁻¹). The amount of AOX also increased with the increase in iodide concentration. These results indicated that the I-DBPs were more toxic than their brominated and chlorinated analogues.
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