Bedner Mary, MacCrehan William A, Helz George R
Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, USA.
Environ Sci Technol. 2004 Mar 15;38(6):1753-8. doi: 10.1021/es035064z.
Chlorination of treated wastewaters is undertaken to prevent dispersal of human pathogens into the environment. Except in well-nitrified effluents, the primary agents in chlorination, Cl2(g) or NaOCl(aq), are short-lived and quickly transfer oxidative chlorine to secondary agents (N-chloramines), which then participate in the disinfection process. Maturation of residual chlorine resulting from chlorine-transfer reactions is still poorly characterized. Using gel permeation and reversed-phase liquid chromatography combined with a novel, oxidant-specific detector, unanticipated trends during the maturation of residual chlorine in wastewater are identified. Within 2 min after addition of NaOCl, and continuing for several hours at least, significant amounts of oxidative chlorine are transferred to secondary agents that are moderately to strongly hydrophobic and to agents that have high relative molecular masses (Mr 1300-25000). It is hypothesized that hydrophobic stabilization of organic chloramines (RNHCl(o)) thermodynamically drives these transfers, making macromolecular chloramines the ultimate oxidative chlorine carriers. Macromolecular chloramines are expected to be sluggish oxidants, as observed in their reduction by sulfite, and are expected to be poor disinfectants. If transfer of oxidative chlorine to high Mr components occurs widely at treatment plants, then this phenomenon offers a new, physicochemical explanation for the well-known impotency of organic chloramines in wastewater disinfection.
对处理后的废水进行氯化处理是为了防止人类病原体扩散到环境中。除了在充分硝化的废水中，氯化处理中的主要试剂，Cl2(g) 或 NaOCl(aq)，寿命较短，并会迅速将氧化态氯转移给二级试剂（N-氯胺），然后这些二级试剂参与消毒过程。氯转移反应产生的余氯成熟过程仍未得到充分表征。使用凝胶渗透和反相液相色谱结合一种新型的、针对氧化剂的检测器，确定了废水中余氯成熟过程中出现的意外趋势。在添加 NaOCl 后的 2 分钟内，并且至少持续数小时，大量的氧化态氯被转移到中度至强疏水性的二级试剂以及具有高相对分子质量（Mr 1300 - 25000）的试剂中。据推测，有机氯胺（RNHCl(o)）的疏水稳定性在热力学上驱动了这些转移，使得大分子氯胺成为最终的氧化态氯载体。正如在它们被亚硫酸盐还原时所观察到的那样，大分子氯胺预计是反应迟缓的氧化剂，并且预计是低效的消毒剂。如果氧化态氯向高分子量成分的转移在处理厂中广泛发生，那么这种现象为废水中有机氯胺在消毒方面众所周知的低效性提供了一种新的物理化学解释。
