Journal
CHEMOSPHERE
Volume 77, Issue 10, Pages 1346-1351Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.chemosphere.2009.09.030
Keywords
Disinfection by-products; Trihalomethanes; Dissolved organic nitrogen; Alanine; Formation pathway
Categories
Funding
- national major science and technology project of China [2008ZX07421-002]
- 11th Five-year Plan science and technology support project of China [2006BAJ08B06]
- Shanghai Tongii Gao Tingyao Environmental Science and Technology Development Foundatio
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Currently, dissolved nitrogenous organic matters in water, important precursors of disinfection by-products (DBPs), are of significant concern. This study was to explore the formation of chloroform (CF) during chlorination of alanine (Ala), an important nitrogenous organic compound commonly present in water sources. Our results indicated that the CF yield reached a maximum value of 0.143% at the molar ratio of chlorine atom to nitrogen atom (Cl/N) = 1.0 over a Cl/N range of 0.2-5.0 (pH = 7.0, reaction time = 5 d, and initial Ala = 0.1 mM). At an acidic-neutral condition (pH 4-7), the formation of CF was suppressed. However, the highest CF yield (0.227%) occurred at weakly alkaline condition (pH 8.0) (initial Ala= 0.1 mM, and Cl/N = 1.0). The increase of Br- in water can increase total trihalomethanes (THMs) and bromo-THMs. However, the bromo-THMs level reached a plateau at Br-/Cl > 0.04. Finally, based on the computation of frontier electron density and identification and measurement of key intermediates during Ala chlorination, we proposed a formation pathway of CF from Ala chlorination: Ala -> monochloro-N-alanine (MC-N-Ala) -> acetaldehyde (AAld) -> monochloroacetaldehyde acetaldehyde (MCAld) -> dichloroacetaldehyde (DCAld) -> trichloroacetaldehyde (TCAld) -> CF. (C) 2009 Elsevier Ltd. All rights reserved.
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