水体中邻苯二甲酸酯降解机理的量子化学及蒙特卡洛模拟

Phthalate esters(PAEs)are a class of organic compounds that are universally existed in the world. There are six PAEs have been listed as a category of priority control pollutants by the U.S. Environmental Protection Agency(US EPA) and three PAEs are classified as priority detect pollutants by the China National Environmental Monitoring Center. PAEs,as endocrine disruptors,show neurotoxicity and reproduction abnormality. It is desirable to study the environmental transfromation processes of PAEs. In this proposal, several classical PAEs are selected as models to investigate the degradation mechanisms of PAEs in aqueous solution using Quantum Chemical Calculation method and Monte Carlo simulations. The geometrical parameters and vibrational frequencies of the reactants, intermediates, transittion states and reaction products located on the reaction processes will be given out quantitively through thermaldynamic parameters such as active energies, enthalpies and Gibbs free energies will also be obtained. The total and individual reaction rate constants can be calculated on the basis of above thermaldynamic parameters and then the branch ratios will be postulated. Through Monte Carlo Simulations, the detailed degradation mechanisms of PAEs in aqueous solution are expected to be revealed. Some original innovative data about reaction processses and kinetics of PAEs in water will be gained which can provide reliable proofs for water treatment.

邻苯二甲酸酯(PAEs)是一类全球普遍存在的有机污染物。已有六种被美国EPA列为优先控制污染物，三种被我国国家环保局列为优先监测污染物。PAEs的生物暴露表现出了神经毒性和生殖异常，属于环境内分泌干扰物。PAEs的环境转化过程已成为环境化学亟待解决的科学问题。本项目拟以典型PAEs为研究目标，基于量子化学计算和蒙特卡洛模拟相结合的方法对其在水体中降解过程的微观反应机制进行研究。通过量子化学计算从理论上定量给出化学转化过程中各驻点的结构参数和振动频率；反应过程中各基元反应的活化能、反应焓及吉布斯自由能变等热力学参数；在此基础上计算各反应速率和反应分支比，比较不同条件下PAEs的降解效率。通过蒙特卡洛模拟定量给出溶剂存在时PAEs降解过程的各热力学参数和微观反应机理。期望本项目的开展能够揭示PAEs在水体中发生降解的微观机制，为污染物的水处理过程提供理论数据参考。

邻苯二甲酸酯（PAEs）及其OH加成产物对水生生物和人类存在健康风险，近年来引起世界范围内的广泛关注。本项目以不同取代基的邻苯二甲酸酯(DMP、DBP、DEP和DEHP)为模型化合物，从理论上研究了PAEs在高级氧化过程（AOPs）中由•OH、SO4•−引发的间接光化学转化机理、动力学和生态毒性。热力学及动力学数据均显示，PAEs很容易通过•OH加成反应及H抽提反应被降解，但二者没有明显的竞争关系。OH自由基的加成反应在氧化降解过程中起主要作用，并且侧链上的H抽提反应较最大。中间产物会继续与环境中的O2、HNO2及HO2•发生后续反应。给出了298K、760Torr时，由•OH及SO4•−引发的总反应速率常数。计算结果表明，在200-400 K温度范围内，PAEs与•OH、SO4•−的反应速率与温度成正相关性。生态毒性评价预测表明，PAEs及其OH加成中间体均具有明显的水生毒性，而SO4•−加成中间体不具有毒性，•OH在后续反应过程中并不能明显消除其转化产物及最终产物的毒性。该项目基本完成了预订计划，并且在原计划基础上对甲氧基苯酚类化合物水溶液中的降解过程及其水生毒性进行了拓展研究，为其他污染物在水体中的降解机制研究奠定了良好的基础。