State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China.
Chemosphere. 2009 Nov;77(10):1346-51. doi: 10.1016/j.chemosphere.2009.09.030. Epub 2009 Oct 12.
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=5d, and initial Ala=0.1mM). 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=0.1mM, 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.
目前，水中溶解的含氮有机物是消毒副产物（DBP）的重要前体，受到了广泛关注。本研究旨在探讨丙氨酸（Ala）在氯化过程中生成三氯甲烷（CF）的情况，Ala 是水中常见的一种重要含氮有机化合物。结果表明，在氯原子与氮原子摩尔比（Cl/N）为 1.0，Cl/N 范围为 0.2-5.0（pH=7.0，反应时间为 5d，初始 Ala=0.1mM）时，CF 的产率达到最大值 0.143%。在酸性-中性条件（pH 4-7）下，CF 的生成受到抑制。然而，在弱碱性条件（pH 8.0）下（初始 Ala=0.1mM，Cl/N=1.0），CF 的产率最高（0.227%）。水中 Br-的增加会增加总三卤甲烷（THMs）和溴代三卤甲烷。然而，当 Br-/Cl-＞0.04 时，溴代三卤甲烷的水平达到了一个平台期。最后，根据 Ala 氯化过程中前沿电子密度的计算以及关键中间产物的鉴定和测量，我们提出了 Ala 氯化生成 CF 的途径：Ala→一氯-N-丙氨酸（MC-N-Ala）→乙醛（AAld）→一氯乙醛-乙醛（MCAld）→二氯乙醛（DCAld）→三氯乙醛（TCAld）→CF。
