改性纳米二氧化硅的制备及其光催化降解多氯联苯的反应机理研究

Polychlorinated biphenyls (PCBs) are a group of persistent organic pollutants that have been widely detected in the environment. Given the potential adverse effects on organisms, it is necessary to develop efficient treatment methods to eliminate PCBs in the environment. Based on our previous findings that nano-silica could produce hydroxyl radicals under light irradiation, this project aims to develop novel green modified nano-silica photocatalysts for the efficient degradation of PCBs in sunlight. Detailed characterizations are made for the synthesized photocatalysts, and their catalytic activity for PCBs degradation are examined under different conditions. The major reactive species are determined by radical quenching experiments and electron paramagnetic resonance (EPR) technology. Modern analytical techniques such as LC-MS and GC-MS are employed to identify the intermediated products. The photocatalytic degradation mechanisms of PCBs are then proposed according to experimental evidences and theoretical calculations. The CASTEP module is used to construct crystal structure models of catalysts, and the electronic structures are analyzed to reveal the catalytic mechanisms of the photocatalysts. The QSAR model between degradation rate constants of PCBs and molecular structure parameters/number and position of Cl substitution will be established to explore the main molecular descriptors affecting the reaction rate. This project provides new insights into the environmental elimination of pollutants, and thus is of vital theoretical and environmental significance.

多氯联苯（PCBs）是一类持久性有机污染物，在环境中广泛检出，具有显著的生物毒性。因此，有必要发展高效的处理技术去除环境中的PCBs类化合物。本项目在发现纳米二氧化硅在光照下产生羟基自由基的基础上，拟制备新型绿色的改性纳米二氧化硅光催化剂，以实现自然光下对PCBs的高效降解。对合成的一系列催化剂进行详细表征，考察各种因素对PCBs降解效率的影响。通过自由基淬灭实验和电子顺磁共振波谱仪确定主要活性物种，采用LC-MS和GC-MS等技术确定中间产物，结合理论计算，提出PCBs的光催化降解机理。采用CASTEP模块，建立催化剂晶体结构模型，分析电子结构等性质，从而揭示催化作用机制。建立PCBs降解速率常数与分子结构参数/取代位置参数之间的QSAR模型，从分子结构的微观层面探究影响转化速率的主要因素。本研究可为环境污染物的去除提供新方法和思路，具有重要的理论价值和环境意义。

多氯联苯（PCBs）是一类持久性有机污染物，在环境中广泛检出，具有显著的生物毒性。因此，有必要发展高效的处理技术去除环境中的PCBs类化合物。本项目制备了新型绿色的改性纳米二氧化硅光催化剂，以实现自然光下对PCBs的高效降解。详细探究了各种环境因素对PCBs降解效率的影响，并对合成的催化剂进行了详细的表征，结合实验技术揭示了光催化体系的关键活性物种和催化机理。采用LC-MS和GC-MS等技术确定中间产物，结合理论计算提出PCBs的光催化降解机理。建立PCBs降解速率常数与分子结构参数之间的QSAR模型，从分子结构的微观层面探究影响转化速率的主要因素。此外，还探究了改性纳米二氧化硅材料对数种持久性有机污染物的光催化降解，发现除了羟基自由外，硅基自由基对有机污染物降解的也起到重要作用。研究还发现：除了可见光能激发二氧化硅产生自由基，红外光也具有同样的激发作用。本研究可为环境污染物的去除提供新方法和思路，具有重要的理论价值和环境意义。