阿特拉津及其光解产物三聚氰酸的电子束辐照降解研究

发布时间：2018-01-03 10:15

本文关键词：阿特拉津及其光解产物三聚氰酸的电子束辐照降解研究　出处：《上海大学》2015年硕士论文　论文类型：学位论文

【摘要】：阿特拉津作为被广泛使用的除草剂,在地表和地下水中无处不在,属于一种环境内分泌干扰物,对生态环境和人类具有毒性和毒害作用,同时,前人研究发现,在光降解阿特拉津过程中,降解反应进行到三聚氰酸就无法被降解了。并且在水体环境中,当三聚氰酸和三聚氰胺共存时,对生态环境的毒性会显著增强。因此,采取有效的降解矿化阿特拉津及其光解产物三聚氰酸手段成为紧迫而关键的任务。本实验研究表明,通过电子束辐照能够实现对阿特拉津的彻底的降解矿化而没有任何三聚氰酸的残留。在纯水中阿特拉津的电子束辐照降解遵循一级降解动力学。在纯水中,浓度为6mg/L的阿特拉津能够在较低辐照剂量(0.5k Gy)时,其降解率就达到90%以上,并且同时伴随氯离子的有效释放。上述剂量下,氯离子的转化率达到85%。通过光解与电子束降解三聚氰酸的对比实验发现:在紫外光解阿特拉津的过程中,浓度为6mg/L的阿特拉津生成的三聚氰酸的量,浓度一直升高到0.8mg/L之后保持不变,且紫外辐照100h之后,三聚氰酸没有任何被降解的迹象;而在电子束辐照降解阿特拉津的过程中,辐照剂量低于20k Gy时,浓度为6mg/L的阿特拉津生成三聚氰酸的浓度一直升高,浓度最大值可到3.14mg/L。在辐照剂量为60k Gy时,浓度为6mg/L的阿特拉津生成的三聚氰酸逐渐被降解到0.37mg/L。三聚氰酸在不同氧化和还原条件的降解效果比较结果如下:通入氮气和叔丁醇形成的还原条件下降解最好,其次是通入空气形成的氧化还原条件,最差是通入氧气形成的氧化条件。此研究表明,不同自由基对阿特拉津和三聚氰酸作用有所差别,其中水合电子对阿特拉津和三聚氰酸的降解矿化起着重要的作用。在电子束辐照降解阿特拉津过程中,依据离子产物分析推测阿特拉津的降解路径和机理可能为:水合电子将阿特拉津的侧链氯还原为氯离子,侧链的烷基被羟基自由基氧化为甲酸,之后聚合形成草酸,并且氨基侧链既可以被羟基自由基氧化为硝酸根,又可以被水合电子还原形成铵根离子,随着辐照剂量的升高,阿特拉津的缺电子苯氮环逐渐被水合电子攻击开环,使得苯氮环中的氮元素大量地被水合电子转化形成铵根离子,同时,苯氮环中的碳元素被转化为甲酸,之后聚合为草酸。在电子束辐照降解三聚氰酸的过程中,也依据离子产物分析推测三聚氰酸的降解路径和机理可能为:水合电子直接攻击缺电子苯氮环致使其开环,将苯氮环中的氮还原为铵根离子,苯氮环中的碳降解为甲酸,之后两个甲酸聚合成草酸。综上所述,电子束辐照能够降解矿化阿特拉津,形成无机离子和有机小分子,同时也能降解矿化阿特拉津光降解产物三聚氰酸。相比于一般高级氧化技术,尤其是光降解,电子束辐照是一种降解阿特拉津及其光降解产物三聚氰酸的有效且安全的手段。
[Abstract]:As a widely used herbicide atrazine, ubiquitous in groundwater and surface water, is a kind of environmental endocrine disruptors, on the ecological environment and human toxicity and toxic effects, at the same time, previous studies found that, in the light of atrazine degradation process, the degradation reaction of cyanuric acid cannot be degraded and in water environment. And when cyanuric acid and melamine coexist, the ecological environment will significantly enhance the toxicity. Therefore, effective degradation of atrazine and its degradation products of cyanuric acid means become urgent and crucial task. The experimental results show that the electron beam irradiation can be achieved on the atrazine completely without any degradation of residues of cyanuric acid degradation of atrazine in water. The electron beam irradiation followed the first-order degradation kinetics. In pure water, the concentration of 6mg/L at Lazin can at low dose irradiation (0.5K Gy), the degradation rate is above 90%, and at the same time with the effective release of chloride ions. The chloride ion dose, conversion rate reached 85%. by contrast experiment and electron beam photolysis degradation of cyanuric acid found in the process of UV solution of atrazine in concentration for atrazine 6mg/L generation of cyanuric acid amount, concentration has been increased to remain unchanged after 0.8mg/L, and 100h after UV irradiation, cyanuric acid without any signs of degradation; and in the process of electron beam irradiation degradation of atrazine, irradiation dose is lower than 20K Gy when the concentration of 6mg/L of atrazine generated cyanuric acid has been increased, the maximum concentration to 3.14mg/L. at dose of 60K Gy, the concentration of atrazine 6mg/L generated cyanuric acid was degraded gradually to three 0.37mg/L. in different polycyanate The degradation effect of oxidation and reduction conditions, the results are as follows: under the condition of the best degradation reduction by adding nitrogen and tert butyl alcohol formation, followed by oxidation with air formed by reducing conditions, the worst is to pass into the oxidation conditions. This study shows that the formation of oxygen free radical, different different of atrazine and cyanuric acid. Among them, degradation of the hydrated electron of atrazine and cyanuric acid. It plays an important role in the electron beam irradiation of atrazine degradation process, based on degradation pathways and mechanism of atrazine ion product analysis may be: hydrated electron will restore the side chain of chlorine atrazine was chlorine ion, the alkyl side chain oxidation by hydroxyl radicals for after the polymerization to form formic acid, oxalic acid, and amino side chain hydroxyl radical can be oxidized to nitrate, but also by the hydrated electron reduction to form ammonium ions, with radiation The exposure dose increased, electron deficient benzene ring nitrogen atrazine was gradually hydrated electron attack ring opening, the nitrogen benzene nitrogen ring is heavily hydrated electron formation of ammonium ions, at the same time, the carbon nitrogen in benzene ring was transformed into formic acid, oxalic acid in the process of polymerization after electron beam irradiation. The degradation of cyanuric acid, also based on the analysis of product ion degradation pathways and mechanism of cyanuric acid may be: hydrated electrons directly attack the electron deficient benzene nitrogen ring resulting in the open loop, the reduction of nitrogen in the nitrogen cycle for ammonium ion, carbon nitrogen degradation of benzene ring in formic acid, after two formic acid polymerization into oxalic acid. In summary, electron beam irradiation can degrade atrazine mineralization, the formation of inorganic ions and small organic molecules, but also degradation of the photodegradation of atrazine to cyanuric acid. Compared to the general product of advanced oxidation technology, especially optical degradation, Electron beam irradiation is an effective and safe method for the degradation of atrazine and Its Photodegradation product of cyanuric acid.

【学位授予单位】：上海大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X592

【参考文献】