Tian Fu-Xiang, Xu Bin, Lin Yi-Li, Hu Chen-Yan, Zhang Tian-Yang, Xia Sheng-Ji, Chu Wen-Hai, Gao Nai-Yun
State Key Laboratory of Pollution Control and Resource Reuse, Institute of Disinfection By-product Control in Water Treatment, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China.
State Key Laboratory of Pollution Control and Resource Reuse, Institute of Disinfection By-product Control in Water Treatment, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China.
Chemosphere. 2017 Oct;184:489-497. doi: 10.1016/j.chemosphere.2017.06.012. Epub 2017 Jun 5.
The degradation kinetics, pathways and disinfection by-products (DBPs) formation of iopamidol by chlorine and chloramines were investigated in this paper. The chlorination kinetics can be well described by a second-order model. The apparent second-order rate constants of iopamidol chlorination significantly increased with solution pH. The rate constants of iopamidol with HOCl and OCl were calculated as (1.66 ± 0.09) × 10 M s and (0.45± 0.02) M s, respectively. However, the chloramination of iopamidol fitted well with third-order kinetics and the maximum of the apparent rate constant occurred at pH 7. It was inferred that the free chlorine (i.e., HOCl and OCl) can react with iopamidol while the combined chlorine species (i.e., NHCl and NHCl) were not reactive with iopamidol. The main intermediates during chlorination or chloramination of iopamidol were identified using ultra performance liquid chromatography - electrospray ionization-mass spectrometry (UPLC-ESI-MS), and the destruction pathways including stepwise deiodination, hydroxylation as well as chlorination were then proposed. The regular and iodinated DBPs formed during chlorination and chloramination of iopamidol were measured. It was found that iodine conversion from iopamidol to toxic iodinated DBPs distinctly increased during chloramination. The results also indicated that although chloramines were much less reactive than chlorine toward iopamidol, they led to the formation of much more toxic iodinated DBPs, especially CHI.
本文研究了碘帕醇在氯和氯胺作用下的降解动力学、途径及消毒副产物（DBPs）的形成。氯化动力学可用二级模型很好地描述。碘帕醇氯化的表观二级速率常数随溶液pH值显著增加。碘帕醇与HOCl和OCl的速率常数分别计算为(1.66 ± 0.09)×10 M⁻¹s⁻¹和(0.45 ± 0.02) M⁻¹s⁻¹。然而，碘帕醇的氯胺化符合三级动力学，表观速率常数最大值出现在pH 7时。据推测，游离氯（即HOCl和OCl）可与碘帕醇反应，而结合氯物种（即NH₂Cl和NHCl₂）与碘帕醇无反应性。采用超高效液相色谱-电喷雾电离质谱（UPLC-ESI-MS）鉴定了碘帕醇氯化或氯胺化过程中的主要中间体，并提出了包括逐步脱碘、羟基化以及氯化在内的破坏途径。测定了碘帕醇氯化和氯胺化过程中形成的常规和碘化DBPs。结果发现，氯胺化过程中碘帕醇向有毒碘化DBPs的碘转化率明显增加。结果还表明，尽管氯胺对碘帕醇的反应性比氯低得多，但它们会导致形成毒性大得多的碘化DBPs，尤其是CHI₃。
