【作者】 李安；

【导师】 陈忠林；

【作者基本信息】 哈尔滨工业大学 ， 市政工程， 2011， 博士

【摘要】 饮用水安全性问题一直受到人们的广泛关注,是国际国内的研究热点。饮用水的生物安全性主要依靠消毒工艺来保证,而氯化消毒技术是目前应用最为广泛的消毒技术。但是氯化消毒过程中可能会产生对人体有危害的消毒副产物(DBPs),为提高饮用水的安全性,对饮用水中DBPs形成和控制的研究显得尤为重要。本文通过实验和理论推导对典型含氮有机物氨基酸(AA)在氯化过程中形成DBPs的生成势、影响因素和生成途径进行了研究。为了考察氨基酸氯化反应过程中DBPs的生成势大小,本文选取20种基本氨基酸进行氯化消毒实验,并以气相色谱对各DBPs的产量进行分析。实验结果表明,以色氨酸(Trp)、天冬氨酸(Asp)和天冬酰胺(Asn)分别具有最强的三卤甲烷(THMs)、卤乙酸(HAAs)和卤乙腈(HANs)的生成能力。酪氨酸(Tyr)、组氨酸(His)、天冬酰胺(Asn)、苯丙氨酸(Phe)、苏氨酸(Thr)和Asp依次具有较大的THMs生成势;组氨酸(His)、Trp、Asn、Tyr、脯氨酸(Pro)、Phe和Thr依次具有较大的HAAs生成势;Tyr、谷氨酰胺(Gln)、谷氨酸(Glu)、His、Trp、Phe和Pro也依次具有相对较大的HANs生成势。实验结果还表明,各氨基酸的耗氯能力大小也是不同的,通过N,N-二乙基对苯二胺-硫酸亚铁铵分光光度法对各氨基酸氯化实验的余氯进行检测,与初始投氯量进行差值计算得知,侧链上具有芳香性环状结构的AA的耗氯量较大,含有羟基,巯基和氨基官能团结构的AA也有较大的耗氯量,这些官能团基本都是具有给电子特性的官能团。鉴于各氨基酸生成DBPs的不同生成势,为进一步明确各氨基酸不同结构在DBPs形成过程中的作用,分类选取六个典型具代表性的氨基酸进行氯化过程的研究。它们分别是侧链具有烷基结构的丙氨酸(Ala)、侧链具有羟基官能团结构的Tyr、侧链具有酰胺结构的Asn、侧链具有羧基结构的Asp、侧链具有吲哚杂环结构的Trp和具有咪唑杂环结构的His。对它们在氯化反应过程中的反应时间、有效氯浓度、pH值、温度、溴离子等影响因素对形成DBPs的影响作用进行了考察。结果显示,THMs和HAAs的产量都是随着时间的增加而增加的,HANs的产量随着反应时间的增加呈现先增加后减少的趋势,温度、pH值和有效氯浓度对DBPs的形成也有较大的影响,由于各氨基酸生成DBPs的机理不同,它们的产量随着温度、pH值和有效氯浓度的不同也表现出不同的变化规律。在溴离子存在情况下,生成溴代和溴氯混合取代产物,DBPs的总产量也会有所提高。经过实验及化学推导分析得知,Ala氯化过程中生成的N-氯代Ala分解生成乙醛,乙醛再氯代生成二氯乙醛和三氯乙醛,再经过氧化即可生成二氯乙酸(DCAA)和三氯乙酸(TCAA);Tyr氯化过程中会生成三氯苯酚,而三氯苯酚氯化则生成TCM,Ala也是Tyr氯化过程中的中间产物,所以经由Ala而生成TCM也是Tyr氯化生成TCM的途径之一;Asn氯化过程中生成三氯乙醛经过亲核加成反应可以形成TCM,而且Asn氯化过程中生成的二氯乙腈(DCAN)水解也可以生成TCM;Asn氯化过程中氯代生成的N-二氯代Asn分解会生成亚胺中间体,可以进一步形成氰基氯胺,再经过取代加成能够得到DCAN,而且由于Asn氯化过程中可以生成二氯乙醛,其侧链的酰胺基团结构氯化又可以生成氯胺,氯胺和二氯乙醛反应即可生成DCAN;Asn氯化过程生成的DCAN的水解可以产生DCAA,而且Asn氯化过程中还可以形成β-二羰基酸的结构,它可以进一步反应生成DCAA;Asp氯化过程中生成三氯乙醛经过亲核加成反应也可以生成TCM, DCAN的水解可以形成TCM;Trp氯化过程中五元吡咯环氧化开环然后再氯代消去可以生成TCM。Trp氯化过程中吲哚基团中的吡咯环上进行α位亲电取代,之后再开环生成亚胺中间体,再经过氯取代反应最终可以生成DCAN;His氯化过程中氯代生成的氯代咪唑进一步发生α位亲电取代,在HOCl的作用下进行开环加成反应,再经过氯取代反应之后形成TCM。更多还原

【Abstract】 Drinking water risk issue was always widely concerned by people and has become international research hotspot over the recent years. Biologic safety of drinking water has been always ensured by disinfection. Chlorination disinfection, as the most common disinfection technology in the water treatment, has been applied in most water plants.But in the process of chlorination disinfection, there will be disinfection by-products(DBPs) produced, which are harmful to person body. Hence, it is very importment to control the formation of DBPs. Amino acids are the representative nitrogenous organic compounds and important precursors of DBPs, the influencing factors and formation mechanisms of DBPs formation via amino acids have been studied.In order to find out the DBPs formation potentials of amino acids, experiments of chlorination disinfection used 20 amino acids as precursors have been carried out. The yields of DBPs are analyzed by Gas Chromatogram. As shown in the experiments results,tryptophan(Trp), has the highest THMs formation potential, and tyrosine(Tyr) takes the second place, histidine(His), asparagines(Asn), phenylalanine (Phe), threonine (Thr) and aspartic acid(Asp) also have higher THMs formation potential than other amino acids. Asp has the highest HAAs formation potential, and His takes the second place, Trp, Asn, Tyr, proline (Pro), Phe and Thr also have higher HAAs formation potential than others. Asn has the highest HANs formation potential, and Tyr takes the second place, glutamine (Gln), glutamic acid (Glu), His, Trp, Phe and Pro also have higher HANs formation potential than others. The results of chlorination disinfection also showed that chlorine demands of amino acids are different. Amino acids with activated aroma rings have higher chlorine demands,and amino acids with hydroxide group, sulfydryl group and amido group also have high chlorine demands.These function groups can lose electron.In view of the differences of structure among the 20 amino acids,in order to confirm the effects of different structure in the course of DBPs formation,the chlorination of six representative amino acids have been studied,which are alanine containing alkyl group,Tyr containing hydroxide group,Asn containing acyl group,Asp containing carboxyl group, Trp containing indole function group and His containing imidazole function group. The effects of influence factors of DBPs, such as reaction time, chlorine concentration, pH, temperature and bromine, have been reviewd. Results shown that the yields of THMs and HAAs both increase with the increase of reaction time, and with the increase of reaction time, the yield of HANs increase at first and then decreased. Chlorine concentration, pH and temperature also influence the formation of DBPs greatly, and the yields of DBPs take on different results as the different structure of amino acids.When there was bromine ion in water, bromine-substituted productions appeared, and the total yields of DBPs increased with the increase of bromine concentration.Some results have been gained by chlorination disinfection experiments and analysis in chemistry theory as follows: Ala react with chlorine to bring N-chloroalanine, which decomposed to acetaldehyde, and then acetaldehyde react with chlorine to produce dichloroacetaldehyde and chloral, via oxidation to form DCAA and TCAA. Tyr react with chlorine can bring trichlorophenol, while trichlorophenol can produce TCM, so via this way, TCM formed from Tyr. While, Tyr also can produce Ala, so TCM formation from Tyr also can via Ala. Asn react with chlorine can bring to chloral, which via nucleophilic reaction can make TCM. Otherwise, DCAN hydrolysis also can induce the formation of TCM.Asn chlorination can produce imine intermediate products, which further react with chlorine to bring cyanogen chloramines, then further to form DCAN. Otherwise, Asn can also produce dichloroacetaldehyde and chloramines, which can react with each other to DCAN.DCAA formation from Asn can via the hydrolysis of DCAN, and also can via the intermediate productsβ-carboxyl. Asp can bring to chloral by reaction with chlorine, chloral via nucleophilic reaction can make TCM. The reaction between Trp with chlorine can open the ring of pyrrole, then further chlorination to form TCM. On indole group of Trp the reaction ofαsubstitute carried at first, then ring opening to bring imine intermediate products, which can further chlorination to DCAN. His react with chlorine to form chloroimidazole, viaαsubstitute, chlorination, ring opening to produce TCM.更多还原