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Chemosphere. 2017 Oct;184:489-497. doi: 10.1016/j.chemosphere.2017.06.012. Epub 2017 Jun 5.

Chlor(am)ination of iopamidol: Kinetics, pathways and disinfection by-products formation.

Author information

1
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.
2
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. Electronic address: tjwenwu@gmail.com.
3
Department of Safety, Health and Environmental Engineering, National Kaohsiung First University of Science and Technology, Kaohsiung, 824, Taiwan, ROC.
4
College of Environmental and Chemical Engineering, Shanghai University of Electric Power, Shanghai, 200090, PR China.

Abstract

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) × 10-3 M-1 s-1 and (0.45± 0.02) M-1 s-1, 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., NH2Cl and NHCl2) 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 CHI3.

KEYWORDS:

Chloramination; Chlorination; Disinfection by-products (DBPs); Iopamidol; Kinetics

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