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Roles of polyDADMACs, dithiocarbamates and activated carbons in formation of N-nitrosamine contaminants in water.

机译：聚DADMAC，二硫代氨基甲酸酯和活性炭在水中N-亚硝胺污染物形成中的作用。

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摘要

N-Nitrosamines are an emerging group of disinfection byproducts characterized by high carcinogenic risks at ng/L levels and by their frequent detection in water and wastewater treatment systems in the U.S. and other parts of the world. The overall goal of this research is to achieve a better understanding of the roles of common nitrosamine precursors in leading to N-nitrosamine formation in water and wastewater treatment systems. The specific objectives of this research are: (a) To probe the mechanisms of nitrosamine formation from commonly employed water treatment polymers, particularly polyDADMACs, during ozonation, (b) To evaluate the role of dithiocarbamate compounds as nitrosamine precursors in reaction with common water disinfection oxidants, and (c) To investigate the potential enhancement effect of activated carbons (AC) to promote transformation of amines to nitrosamines and identify the involved reaction mechanism.;Results of this research show that, upon ozonation, polyDADMACs may yield N-nitrosodimethylamine (NDMA) at levels up to two orders of magnitude higher than current advisory guidelines for NDMA. Radical pathways may be responsible for the degradation of the quaternary ammonium ring groups in polyDADMACs to release of dimethylamine (DMA). Ozonation of released DMA through formation of reaction intermediates such as hydroxylamine and unsymmetrical dimethylhydrazine (UDMH) may be responsible for observed NDMA formation during ozonation of polyDADMACs. Study results also reveal dithiocarbamates as potent nitrosamine precursors with significant nitrosamine yields upon ozonation and monochloramination. Identification and quantification of reaction products suggest UDMH and chlorinated-UDMH oxidation as primary reaction mechanisms in nitrosamine formation from ozonation and monochloramination of dithiocarbamates compounds, respectively. This research also demonstrates that many commercial AC materials may catalyze transformation of secondary amines to yield trace levels of N-nitrosamines under ambient aerobic conditions. This is a novel discovery with far-reaching implications because of the widespread usage of AC materials in numerous analytical and environmental applications. The study results show that the properties of AC materials and reaction conditions play a crucial role in the catalyzed nitrosamine formation and should be carefully selected to minimize analytical errors and undesirable nitrosamine formation in water samples. Overall, the mechanistic information obtained in this research will be useful for the water industry and research communities to develop more effective strategies to control undesirable nitrosamine formation in water and wastewater treatment systems and thus better protect the public health.
机译：N-亚硝胺是一类新兴的消毒副产物，其特征是在ng / L浓度下具有很高的致癌风险，并且经常在美国和世界其他地区的水和废水处理系统中被检测出。这项研究的总体目标是更好地了解常见亚硝胺前体在水和废水处理系统中导致N-亚硝胺形成的作用。这项研究的具体目标是：（a）探讨在臭氧化过程中常用水处理聚合物（尤其是聚DADMAC）形成亚硝胺的机理，（b）评估二硫代氨基甲酸酯化合物作为亚硝胺前体在与普通水消毒反应中的作用。 （c）研究活性炭（AC）促进胺向亚硝胺转化的潜在增强作用，并确定涉及的反应机理。 NDMA）的级别比当前的NDMA咨询指南高两个数量级。自由基途径可能是造成polyDADMAC中季铵环基团降解以释放二甲胺（DMA）的原因。通过形成反应中间体（例如羟胺和不对称的二甲基肼（UDMH））使释放的DMA发生臭氧化，可能是造成聚DADMAC臭氧化过程中观察到的NDMA形成的原因。研究结果还表明，二硫代氨基甲酸酯是有效的亚硝胺前体，在臭氧化和单氯胺化后，亚硝胺的收率很高。反应产物的鉴定和定量表明，UDMH和氯化UDMH氧化分别是二硫代氨基甲酸酯化合物的臭氧化和单氯胺化形成亚硝胺的主要反应机理。这项研究还表明，许多商业交流材料可能会在环境好氧条件下催化仲胺的转化，从而产生痕量的N-亚硝胺。由于AC材料在众多分析和环境应用中的广泛使用，这是一个具有深远意义的新发现。研究结果表明，交流材料的性能和反应条件在催化亚硝胺的形成中起着至关重要的作用，应谨慎选择以最大程度地减少水样中的分析误差和不良亚硝胺的形成。总体而言，从这项研究中获得的机械信息将对水行业和研究团体制定更有效的策略以控制水和废水处理系统中不良的亚硝胺形成，从而更好地保护公众健康很有帮助。

著录项

  • 作者

    Padhye, Lokesh Pradeep.;

  • 作者单位

    Georgia Institute of Technology.;

  • 授予单位 Georgia Institute of Technology.;
  • 学科 Engineering Environmental.
  • 学位 Ph.D.
  • 年度 2010
  • 页码 186 p.
  • 总页数 186
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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