多氯酚光化学降解过程中氧空位诱导底物活化作用研究

Polychlorinated phenols residue problem and transformation in environment has been highly concerned in the environmental field due to their high toxicity, bioaccumulation and long-distance migration. Photochemical degradation is of great important in their abiotic transformation pathways. In this process, various reactive oxygen species are involved and play crucial roles in their dechlorination and mineralization. However, the roles of defects induced substrate activation by oxygen vacancies on natural suspended solids and soil minerals are scarcely investigated. In this project, the mechanism of oxygen vacancies induced substrate activation will be systematically studied by photocatalytic degradation of chlorophenol pollutants over BiOCl with oxygen species. Theoretical calculation and intermediate products analysis will be applied to investigate the influence of substrate activation on the photochemical decomposition path of chlorophenol pollutants. And trapping experiment and active species detection will be adopted to study the synergistic mechanism of substrate activation and reactive oxygen species during photocatalytic degradation process of chlorophenol, as well as to clarify the relationship between mineralization and the photochemical decomposition path of chlorophenol pollutants. On the basis of the above results, novel chlorophenol pollutants removal strategies will be proposed by utilizing oxygen vacancies induced substrate activation and reactive oxygen species. This study can deepen our understanding on the absorption, migration and photochemical transformation of polychlorinated phenols on the surface of mineral with defects.

多氯酚类化合物的高毒、生物累积及远距离迁移等特征，使其在环境中的残留问题及降解转化过程备受关注。而光化学降解是氯酚在环境中非生物转化的一种重要途径，其转化过程中活性物种对脱氯和矿化起着关键性的作用。然而，自然水体颗粒物表面和土壤矿物表面缺陷(如氧空位)引起的底物活化却鲜有报道。本项目拟利用含氧空位氯氧铋光催化降解多氯酚类污染物，系统研究氧空位诱导底物活化作用机制；通过理论计算和中间产物检测分析，探究氧空位底物活化作用对多氯酚类污染物光催化降解路径的影响规律；同时，通过活性物种捕获实验和检测分析揭示氧空位底物活化与活性氧物种在多氯酚类污染物光降解过程中的协同作用机制，探索氯酚类污染物降解和矿化途径之间的关系，以期探索出利用氧空位诱导的底物活化与活性氧物种高效深度氧化氯酚类化合物的新途径，为进一步深入理解多氯酚污染物在含缺陷矿物表面的吸附，迁移和光化学转化过程提供参考。

本项目制备了多种氧空位浓度可调的纳米材料，并研究了小分子化合物在氧空位上的活化作用和一些常见有机污染物的光化学转化路径；以此作为参考，申请人接下来研究了五氯酚在含氧空位纳米材料表面的活化机理，通过离子色谱和总有机碳分析发现，氧空位的存在显著促进了五氯酚的矿化和脱氯效果；利用活性物种捕获实验和中间产物检测分析发现超氧负离子和单线态氧分别在五氯酚的脱氯还原过程和脱氯氧化过程起着关键作用；另外红外分析和理论模拟等相关数据还发现表面氧空位能够活化吸附的五氯酚分子协同表面羟基自由基完成羟基化反应;在可见光下，表面氧空位浓度的增大有利于羟基化产物四氯氢醌的生成，并进一步氧化成易开环的四氯醌，有利于污染物的开环降解，而太阳光下，氧空位浓度的增大则会促进五氯酚的还原脱氯过程，降低中间产物的环境毒性，有利于开环和矿化反应。该结果为进一步深入理解多氯酚污染物在含缺陷矿物表面的吸附，迁移和光化学转化过程提供了参考。