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外源性新兴有机污染物不断进入水环境，浓度低但生物毒性强，其环境风险日益受到关注。同时，由于水中溶解性有机物种类繁多、且浓度远高于新兴污染物，常规废水深度处理方法难以针对性去除浓度更低、毒性更强的的新兴有机污染物。因此，如何在其他污染物共存的情况下有效控制水中新兴有毒有机污染物一直是水和废水深度处理领域的重要研究课题。为此，本文针对水中低浓度高毒性的新兴有机污染物，研究在生物酶、锰氧化合物和过氧乙酸三种弱催化氧化及无外源催化剂/氧化剂体系下，新兴污染物与其他有机污染物发生聚合/偶联的反应途径与机理，并采用计算化学手段预测反应活性位点与聚合产物毒性变化，实现污染物选择性深度去除与解毒，为深度处理新兴有机污染物提出一种新思路与方法，主要工作为：（1）在生物酶催化体系，研究了硫醇类药物卡普托利(CAP)在酚类腐殖酸模拟物存在时的动力学行为与聚合/偶联机理，并通过计算化学福井函数预测聚合反应中间产物结构及活性位点，发现不同酚类结构经过漆酶催化单电子氧化作用后可生成醌类、碳正离子自由基等活性中间产物，显著影响后续与CAP继续发生亲核加成/取代等反应途径与产物，最终CAP以C-S-C共价键的形式进入腐殖酸结构，实现硫醇类污染物的深度去除。进一步基于密度泛函(DFT)理论计算，深入阐释氯酚类污染物在酶催化单电子氧化中的反应机理，并优化酶-电催化耦合技术，通过电流与CO2协同控制氯酚类污染物的聚合过程，减少氯醌类毒性中间产物的产生，实现酶-电催化聚合解毒的协同与调控。（2）针对雌二醇（E2）类内分泌干扰物，分别在MnO2直接氧化和MnO2复合材料光催化体系，研究了E2去除动力学和反应机理，结果表明MnO2复合材料对E2的去除比单独MnO2有显著促进效果。并进一步采用计算化学方法对活性中间产物E2酚氧自由基的自旋密度和电荷分布进行分析，发现复合材料中的MnO2组份首先通过单电子氧化E2分子产生E2酚氧自由基，激活了光催化氧化中羟基自由基亲电偶联反应，从而大大促进了后续的E2氧化降解反应。（3）研究了过氧乙酸弱氧化剂对有机物的直接或间接氧化聚合过程，发现过氧乙酸在直接氧化氨基酸分子过程中反应速率较慢，且反应产物主要为加氧产物以及相应的二聚体衍生物。同时，使用钴离子高效激发过氧乙酸溶液生成相应的活性自由基形态，如 CH3C(=O)O?，CH3C(=O)?，?OH和?CH3等，与有机污染物发生亲电/亲核加成反应，实现污染物的偶联去除。其中，在氧化水晶紫染料实验中，由于活性自由基在助色官能团上的加成作用，反应液出现了不断的颜色变换现象。进一步基于量子化学计算所得有机物结构物化参数和其在钴离子激发过氧乙酸氧化体系中的反应活性之间的关系，建立定量构效关系模型，公式为 ，有效预测有机污染物在钴离子激发过氧乙酸体系中的偶联反应活性。（4）研究了在无外源催化剂/氧化剂存在条件下，氯醌类高毒性污染物与水体中氨基酸小分子之间的聚合偶联解毒机理，并基于反应产物鉴定及细菌急性毒性实验结果，提出水中富电氨基酸通过亲核加成/取代反应进入氯醌类毒性污染物结构，以C-N-C共价键形式占据氯醌类污染物活性位点使其毒性降低。计算化学研究表明，氯醌类污染物结构和相应物化参数，如ELUMO值的不同，导致其相应的亲电指数，氧化能力和初始毒性也有差异，显著影响了聚合偶联解毒途径及产物毒性。;With the continuous discharge of external emerging organic pollutants into waters, the related pollution problems have draw increasing attentions. These pollutants are usually found to be with low concentration, however, great risk towards aquatic organisms and humanity. Non-selective traditional water treatment methods show low efficiency in the removal of target pollutants, especially in the presence of abundant and harmless humic substances. Therefore, how to effectively control emerging organic pollutants has become an important issue in water deep-treatment research field.In this study, we focus on the coupling transformation of target pollutants in enzymatic oxidation, manganese oxides oxidation, peracetic acid oxidation, and non-oxidant polymerization system. Quantum chemistry is further applied to predict the regioselectivity and toxicity variation, and explore the detailed coupling reaction mechanism for selective removal and detoxification of emerging organic pollutants. The main work and results are listed as follows:(1) Laccase-catalyzed coupling transformation of CAP in the presence of phenolic humic substances was studied. The results of reaction kinetics, products identification, and Fukui function showed that the humic substances may firstly transform to corresponding quinoid intermediates or carbon-centered radical cations during laccase-catalyzed one-electron oxidation, which greatly impacted the further coupling of CAP molecules and combination conjugates formation. Furthermore, detailed coupling mechanism of DCP was proposed based on DFT study, combined enzymatic-electronic catalyzed-oxidation technology was explored, in which CO2 and current was adjusted to control the reaction pathways for toxification of chlorophenols.(2) Based on the typical radical coupling of phenolic pollutants in MnO2 oxidation, MnO2-doped TNTs material was prepared for photocatalyzed oxidation. The result of reaction kinetics indicated that the prepared MnO2-doped TNTs is more efficient in the oxidation of E2 than pure TNTs or MnO2. On the basis of materials characterization, reaction products verification and radical scavenging experiments, Theoretical spin density and charge population were applied to analyze the regioselectivity of radical attacks on E2 molecule and radical. Corresponding explanations were proposed: heterojunction structure of MnO2 and titanate may result in inhibited electron-hole recombination and promoted visible-light-driven photocatalytic activity, more reactive radicals were produced; moreover, MnO2-induced pre-oxidation could facilitate the barrier-less coupling of E2 radical and ?OH.(3) Peracetic acid-based oxidant was studied to explore its direct and indirect oxidation behavior toward organic pollutants. The results showed that the direct oxidation of amino acids by peracetic acids is relatively weak, the oxidation products were mainly [O] addition conjugate and relative dimers. Moreover, we found that Co2+ may effectively activate peracetic acid to generate reactive radicals, such as CH3C(=O)O?, CH3C(=O)?, ?OH and ?CH3, which may react with target pollutants through nucleophilic/electrophilic addition reactions. Color-shifting was observed during the oxidation of crystal violet in Co2+ catalyzed peracetic acid system, this may be caused by the radical addition on the chromophore groups of crystal violet. A QSAR model was established based on the structural physiochemical parameter of organic pollutants and reaction kinetics in Co2+ catalyzed peracetic acid oxidation system, this model can be used to predict the reactivity of other organic pollutants in this system, the equation is .(4) The spontaneous coupling reaction of toxic chlorobenzoquinones intermediates and electron-rich amino acids without additional oxidants was investigated. Based on products identification and bacteria toxicity assessment, the reaction mechanisms were proposed as follows: electron-rich amino acids could react with chlorobenzoquinones through nucleophilic addition, which is a detoxification step by occupying the reactive site of quinones through C-N-C combination. Theoretical calculations suggested that the structure and physicochemical property may decide the corresponding electron affinity, oxidative potential and toxicity of CBQs, and further impact the spontaneous coupling reaction pathways and toxicity change with amino acids.
|杜朋辉. 水中新兴有机污染物的聚合偶联机理研究[D]. 中国科学院大学,2018.|
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