【作者】 韩莹；

【导师】 陈忠林；

【作者基本信息】 哈尔滨工业大学 ， 市政工程， 2009， 硕士

【摘要】 亚硝基二甲胺（NDMA）具有潜在强致癌性,美国环保署确定其单位致癌风险对应的浓度为0.7ng·L^-1。加拿大的许多水井中都被发现存在有不同浓度的NDMA,经氯或氯胺消毒后的水体中也可检测到NDMA,其作为一种新型的消毒副产物逐渐引起国内外水处理行业的广泛重视。传统的去除方法不能有效地去除NDMA,紫外光解对NDMA的去除效果好,但此种方法能耗高、处理费用高,难以进行实际应用。零价金属还原技术,原料来源广泛且操作简便,是水处理中去除污染物研究的新方向,研究零价金属还原对NDMA的去除与控制技术,具有重要的理论意义和实际应用价值。本文采用零价锌还原降解水中NDMA,考察各种因素对于零价锌还原降解NDMA的影响,分析确定其降解产物,并由此推测出零价锌还原降解NDMA的机理,从而为进一步的研究和工程应用,提供数据支持。首先考察了零价锌还原降解NDMA的影响因素。结果表明,零价锌可以有效地还原降解水中痕量NDMA。在锌粉投量10g·L^-1,反应温度20℃,溶液初始pH=7.0,反应搅拌转速为200r·min-1时,反应进行14h,NDMA的去除率可达99%以上;水中溶解氧和NDMA初始浓度对于去除率的影响不大;pH值和反应温度对于零价锌还原降解NDMA的影响显著,pH值越小,温度越高,反应进行得越快;水体中常见阴阳离子和腐殖酸对零价锌还原降解NDMA有一定的抑制作用。中性条件下,零价锌还原降解NDMA的过程分为慢速启动期和快速上升期。各种反应条件下,当NDMA降解率高时,锌离子溶出量一般大于1mg·L^-1。在对溶液不同初始溶解氧浓度、pH值、反应温度和常见阴阳离子对于NDMA去除影响的考察中发现,反应过程中pH值的变化、锌离子的溶出量、NDMA的降解率三者之间具有一定的相关性。对于零价锌还原降解NDMA的产物进行了测定和分析,产物主要为偏二甲肼（UDMH）、二甲胺（DMA）和氨氮（NH₄⁺）。不同溶液初始pH条件下,UDMH、DMA和NH₄⁺的生成规律有所不同。锌离子对于NDMA的检测和降解影响不明显。零价锌还原NDMA的历程为:由NDMA还原为UDMH之后再还原为DMA和NH₄⁺,推测其还原途径为催化加氢和氢原子直接还原。更多还原

【Abstract】 N-nitrosodimethylamine（NDMA） is potent carcinogen. The U.S.EPA drinking water Standard for NDMA is set at 0.7 parts per trillion. NDMA has been detected at elevated levels at many wells throughout Canada. NDMA can be detected in water after chlorination or chloramination. It has caused significant concern among drinking water and wastewater recycling utilities. NDMA is difficult to remove using conventional treatment methods. Currently, the most prevalent NDMA treatment method is direct UV photolysis, but it needs the high energy consumption and is expensive and difficult to be applied. The zero-valent metal technology , with wide raw sources and simple operation, has recently received much attention. There is strong practical significance by applying it to the control of NDMA.Zero-valent zinc was used to degrade NDMA in water. The objectives were not only to investigate the affecting factors, but also to identify the products and deduce the degradation pathways especially. The data can be used to support further research and engineering applications.The affecting factors of reduction of NDMA by zero-valent zinc were investigated. Results show that,the trace NDMA can be degraded effectively by zero-valent zinc. The degradation rate of above 99% can be achieved after 14h under the condition of 10g·L^-1 zinc, 20℃, initial solution pH of 7.0, rotating rates of 200r·min-1. The effect of dissolved oxygen and initial NDMA concentration on the reduction of NDMA are not remarkable while the pH and temperature of solution could effect the reduction of NDMA by zinc greatly. With pH decreasing or temperature ascending, the removal rate of NDMA increased. The removal of NDMA could be inhibited by the anions, cations and humic acid in the water.On neutral conditions, the reduction process of NDMA by zero-valent zinc is divided into two periods of slow start-up and rapid increasing. The leaching of zinc ions are generally larger than 1mg·L^-1 when NDMA reach to a high degrading efficiency. On the conditions of different initial dissolved oxygen concerntration, pH, reaction temperature and the common ions ,the pH value variation and the dissolution of zinc ions are relevant with the degradation of NDMA. The products of the reduction of NDMA by zero-valent zinc were detected and analyzed.The main products are 1,1-dimethylhydrazine（UDMH）, dimethylamine（DMA） and ammonium（NH₄⁺）.Under Different initial solution pH conditions, the generation trends of UDMH, DMA and NH₄⁺ were different.The effects of Zinc ions on NDMA detection and the degradation of NDMA were not obvious. The degradation pathway of the reduction of NDMA by Zero-valent zinc is from NDMA to UDMH first and then to DMA and NH₄⁺.The reduction mechanism has been deduced as catalytic hydrogenation and direct reduction by hydrogen atom.更多还原