臭氧预氧化过程中NDMA生成机理及前体物识别

To elucidate the fate of N-nitrosodimethylamine (NDMA) precursors in the pre-ozonation process, the specific structures of NDMA precursors that react with ozone and generate NDMA easily were identified. By studying the species transformation and oxidation mechanism of NDMA precursors, the relationships between the intermediate oxidation products and NDMA formation were clarified and a model of quantity structure-activity relationship (QSAR) was established. Based on the identified general features of NDMA precursors, polarity rapid assessment method (PRAM) was set up for the enrichment and classification of this kind of precursors in water source. PRAM combing the method of the molecular weight distribution and organic spectroscopy technology made up the NDMA precursors identification system, the key functional groups /component that react with ozone fast and accurately were further researched. The effect of pre-ozonation on subsequent disinfection process was also investigated. The pre-oxidation conditions were optimized to slash down the NDMA formation for different water source. Finally, a comprehensive model was put forward to reduce NDMA formation on the basis of precursors identification in pre-ozonation process. The results can provide the theoretical basis and technical support for the application of ozone, abating the effect of NDMA in drinking water on human health.

针对二甲基亚硝胺（NDMA）前体物在臭氧预氧化过程中行为归趋不明确问题，识别易与臭氧反应生成NDMA的前体物结构特征，研究氧化过程中其形态转化及氧化机理，阐明前体物结构与NDMA生成的内在联系，建立两者之间的定量构效关系模型；基于已识别NDMA前体物的结构特征，建立快速极性分析法（PRAM）对实际水体中NDMA前体物进行富集和分类，将其和分子量分布、有机波谱等技术组合，构建NDMA前体物解析体系，进一步研究实际水体中易与臭氧反应前体物的关键官能团/组分；考察臭氧预氧化NDMA前体物对后续消毒的影响，优化针对不同水源的预氧化条件以削减NDMA生成量，提出基于前体物识别削减臭氧预氧化生成NDMA的综合控制模型。研究成果可为臭氧应用提供理论依据和技术支撑，降低饮用水中NDMA对人类健康的风险。

臭氧氧化能力较强，能有效去除具有强烈致癌性的副产物二甲基亚硝胺（NDMA）前体物，然而近年来却发现其能直接与前体物反应生成NDMA。针对臭氧对NDMA前体物作用不明确问题，本项目选取典型胺基化合物，识别出易与臭氧反应生成NDMA的前体物含有 (CH3)2N-R-N-结构，前体物结构与NDMA生成具有内在联系，N-N直接连接或R是易移去基团或者吸电子基团的这类化合物臭氧氧化时NDMA的摩尔转化率较高，两者之间存在定量构效关系。.臭氧及臭氧预氧化化对后续氯和氯胺消毒的影响是多方面的：前体物中(CH3)2N-基团边上有吸电子基团，预臭氧可降低该类物质后续消毒NDMA的摩尔转化率；反之，增加其生成；且水体中的各组分对不同前体物的影响也各异，应根据前体物的性质及水体条件选择合适的预氧化方式、氧化条件及后续的消毒方式。以典型前体物雷尼替丁（RNTD,降低）和丁酰肼（DMNZD, 增加）为例，研究其形态转化及氧化机理。臭氧化能将雷尼替丁转化成NDMA摩尔转化率较低的二甲胺(DMA)，能大大降低后续氯胺消毒生成的NDMA量。因而，对于含有RNTD等前体物的水体可通过增加臭氧投加量来降低其后续氯胺消毒生成NDMA。实际水体中溴离子、有机物和碳酸氢根等羟基猝灭剂增加RNTD臭氧化后续氯胺消毒NDMA的生成。丁酰肼与氯和氯胺反应不生成NDMA，但其易与臭氧直接反应生成NDMA，且随臭氧投加量增加而增加，水中溴离子和有机物的存在可降低丁酰肼臭氧化生成的NDMA量，但水中的碳酸氢根等羟基猝灭剂却能增加NDMA生成。.基于已识别NDMA前体物的结构特征，构建NDMA前体物解析体系，研究发现实际水体中易与臭氧反应前体物的关键组分是非极性物质和正电组分，因而，对于这两种成分较高的水体，应尽量避免使用臭氧预氧化工艺。研究成果可为臭氧应用提供理论依据和技术支撑，降低饮用水中NDMA对人类健康的风险，该成果对保护公众健康、发展安全饮用水具有重要现实意义，具有广阔的应用前景，经济和社会效益是不可估量。