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题名: 机械化学法降解六氯苯污染物的自由基脱氯反应机理及应用研究
作者: 邓闪闪1
学位类别: 硕士
答辩日期: 2017-05
授予单位: 中国科学院大学
授予地点: 北京
导师: 朱建新
关键词: 自由基脱氯,密度泛函理论,机械化学法降解,土壤修复,六氯苯 ; Free-radical dechlorination, Density functional theory (DFT),Mechanochemical degradation, Soil remediation, Hexachlorobenzene
其他题名: Free-radical Dechlorination Mechanism and Application for Mechanochemical Degradation of Hexachlorobenzene
学位专业: 环境工程
中文摘要: 持久性有机污染物(POPs)中有机卤素含量较高,处理难度大,是全球性 的污染难题。因此,研发安全、高效的非焚烧类处置技术对于缓解我国 POPs废 物的环境污染,履行斯德哥尔摩国际公约,保护生态环境和人类健康,具有重要 的意义。机械化学法反应条件温和,能够实现 POPs的高效降解并且不易产生高 毒性副产物,是一种先进的 POPs污染物处理处置技术。 论文针对 POPs污染土壤的机械化学脱氯降解,以六氯苯(HCB)为模型化 合物,采用量子化学理论分析和实验研究相结合的方法探索了机械化学法降解 HCB的自由基脱氯反应机理,提出了基于氯代苯氧自由基主导的逐级脱氯反应 路径,研究和分析了机械化学降解技术在 HCB污染土壤修复中应用的可行性。 主要研究内容和成果包括: (1)机械化学反应过程中,HCB污染土壤的脱氯路径的主要特点为逐级脱 氯,根据主要中间产物分布可以得到主要脱氯路径为 HCB → PeCB → 1,2,3,4-TeCB → 1,2,3-TrCB → 1,2-DCB → MCB。电子自旋共振(ESR),X-射线 光电子能谱(XPS)和傅里叶变换红外光谱(FTIR)等检测表明 HCB污染物的 脱氯降解过程伴随着自由基的生成和迁移转化。HCB与氧化硅、氧化铝等氧化 物在机械球磨过程中会发生相互作用生成氯代苯氧自由基。 (2)通过密度泛函理论(DFT)的量子化学计算得到氯代苯氧自由基的生 成路径及反应活化能。结果表明,在机械力作用下,HCB中的 Cl逐渐远离相连 的 C原子和苯环平面,O的路径正好相反。自由基生成过程中 C-Cl键的共价作 用逐渐减弱而 C-O共价键逐渐形成。电子定域性可视化分析和拓扑分析定量化 表明了氯代苯氧自由基生成过程中伴随的成键状态和电子密度分布的明显变化。 (3)原子电荷、静电势、双描述符、前线轨道理论和福井函数六种量子化 学描述符分析表明氯代苯氧自由基的脱氯反应活性位点、脱氯顺序和中间产物的 分布与 HCB污染土壤的机械化学脱氯实验结果相符,表明机械化学降解 HCB 的脱氯过程为自由基攻击主导的逐级还原脱氯反应,脱氯过程涉及的自由基主要 为氯代苯氧自由基。 (4)HCB污染土壤工艺降解实验表明机械化学法对 HCB污染土壤有较好 的降解效率,在 POPs污染土壤修复中具有良好的技术可行性和应用前景。两种 模拟土壤和两种实际土壤球磨 210 min后,HCB污染物的降解效率均在 95%以 上,氧化物含量较高的土壤降解效果略好,表明氧化物(尤其是氧化铝)含量较 高有利于提高 HCB的降解效率。添加金属单质可以在一定程度上提高 HCB的 降解效率,而腐殖酸含量的增加会降低降解效率。
英文摘要: Persistent Organic Pollutants (POPs) contains high amounts of halogen, resulting in high difficultities for dispose. Therefore, developing the eco-friend and high-efficient non-incineration technology is of great significance for alleviating the POPs pollution, fulfilling the Stockholm Convention and protecting the environment and human health. Mechanochemical degradation (MCD) is a promising method to eliminate the environmental hazards, which can effectively degrade the POPs and avoid the formation of high-toxic byproducts in mild reaction conditions. With HCB as the model compound, this paper aims to study the mechanochemical dechloriantion process of POPs contaminated soils. The free-radical dechloriantion mechanism of HCB was studied through the unite method of quantum chemical analysis and experiments. The chlorinated phenoxy radicals (CB-O●) based step-wise dechlorination pathway was proposed. At last, we carried on the research on the application of MCD technology into the remediation of HCB contaminated soils. The main research contents and achievements were as follows. (1) The dechloriantion reaction followed the step-wise dechlorination process and the main dechlorination route was HCB → PeCB → 1,2,3,4-TeCB → 1,2,3-TrCB → 1,2-DCB → MCB according to the distribution of intermediates. Formation and transformation of radicals were demonstrated by results of electron spin-resonance (ESR), X-ray photoelectron (XPS) spectra and Fourier transform infrared (FTIR) spectra. Characterizations of milled alumina and silica indicated that oxides would react with HCB and formed the CB-O● in the milling process. (2) A reasonable CB-O● formation path was demonstrated and the activation energies were obtained by Density Functional Theory (DFT) calculations.Under the mechanic force, the chlorine deviate from the linked carbon atom and the benzene ring, while the oxygen atom showed the opposite route. Moreover, two kinds of electron localized analysis and topological analysis were applied to visualized and quantified depict the changes of electron states. The covalent interaction gradually weakened and the covalent bond formed along the radical formation pathway. (3) Five quantum chemical descriptors were selected in predicting the active dechlorination sites, the main intermediates and reaction pathway of CB-O●: (i) atomic charge, (ii) electrostatic potential (ESP), (iii) dual descriptor, (iv) frontier molecular orbitals (FMO) theory and (v) Fukui function. The calculation results agreed well with the experimental results and indicated that the mechanochemical reduction dechlorination was induced by radical attack. The CB-O● dechlornation pathway is the main dechloriantion route in the MCD process. based (4) This thesis also studied the efficiencies for contaminated soil remediation through mechanochemical degradation. After milling for 210 min, the degradation rates achieved at least 95% for the two kinds of actual soil and two kinds of synthetic soil. The soil with higher concentration of oxides exhibited the higher removal effect The addition of Al can increase the degradation rate at a low degree. Besides, results also showed that the humic would restrain the MCD process.
内容类型: 学位论文
URI标识: http://ir.rcees.ac.cn/handle/311016/38613
Appears in Collections:固体废弃物处理与资源化实验室_学位论文

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作者单位: 1.中国科学院生态环境研究中心

Recommended Citation:
邓闪闪. 机械化学法降解六氯苯污染物的自由基脱氯反应机理及应用研究[D]. 北京. 中国科学院大学. 2017.
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