Formation of iodo-trihalomethanes, iodo-acetic acids, and iodo-acetamides during chloramination of iodide-containing waters: Factors influencing formation and reaction pathways.
This study investigated systematically the factors influencing the formation of iodinated disinfection by-products (I-DBPs) during chloramination of I--containing waters, including reaction time, NH2Cl dose, I-concentration, pH, natural organic matter (NOM) concentration, Br-/I-molar ratio, and water matrix. Among the I-DBPs detected, iodoform (CHI3), iodoacetic acid (IAA), diiodoacetic acid (DIAA), triiodoacetic acid (TIAA), and diiodoacetamide (DIAcAm) were the major species produced from reactions between reactive iodine species (HOI/I2) and NOM. A kinetic model involving the reactions of NH2Cl auto-decomposition, iodine species transformation and NOM consumption was developed, which could well describe NH2Cl decay and HOI/I2evolution. Higher concentrations of CHI3, IAA, DIAA, TIAA, and DIAcAm were observed in chloramination than in chlorination, whereas IO3-was only formed significantly in chlorination. Maximum formation of I-DBPs occurred at pH 8.0, but acidic conditions favored the formation of iodinated haloacetic acids and DIAcAm. Increasing Br-/I-molar ratio from 1 to 10 did not increase the total amount of I-DBPs, but produced more bromine-substituting species. In addition, chloramination of 18 model compounds indicated that low-SUVA254(specific ultraviolet absorbance at 254nm) NOM generally favored the formation of I-DBPs compared to high-SUVA254NOM. Finally, potential pathways for I-DBPs formation from chloramination of NOM were proposed.
Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 18 Shuang-qing Road, Beijing, 100085, China; Guangxi Colleges and Universities Key Laboratory of Food Safety and Pharmaceutical Analytical Chemistry, Guangxi Key Laboratory of Chemistry and Engineering of Forest Products, School of Chemistry and Chemical Engineering, Guangxi University for Nationalities, Nanning, 530006, Guangxi, China.
Shaogang
S
Liu
Guangxi Colleges and Universities Key Laboratory of Food Safety and Pharmaceutical Analytical Chemistry, Guangxi Key Laboratory of Chemistry and Engineering of Forest Products, School of Chemistry and Chemical Engineering, Guangxi University for Nationalities, Nanning, 530006, Guangxi, China.
Zhenlin
Z
Li
Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 18 Shuang-qing Road, Beijing, 100085, China.
Huiyu
H
Dong
College of Physical Science and Engineering, State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangxi University, Nanning, 520004, Guangxi, China.
Bernard A
BA
Goodman
Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 18 Shuang-qing Road, Beijing, 100085, China. Electronic address: qiangz@rcees.ac.cn.
Zhimin
Z
Qiang
Influential factors; Iodinated disinfection by-products (I-DBPs); Monochloramine (NH(2)Cl); Natural organic matter (NOM); Pathways