高毒性含氯芳香污染物的仿酶光电催化降解机制研究

Owing to the high stability and toxicity, poor biodegradability, refractory characteristic and complex matrix, it is hard and challenging to achieve the selective and deep degradation of chlorinated aromatic pollutants which is of very low concentration in the water environment. In this project, a typical chlorinated pesticide atrazine is selected as the research object, and an enzyme mimic catalytic degradation method is proposed by fabricating enzyme mimic active center on the surface of ordered and mesoporous TiO2 electrode with molecular imprinting technique. Utilizing the active centers fabricated, the prepared MI-meso-TiO2 electrode can not only recognize atrazine from the coexisted pollutants and bind atrazine on the active centers, but also the interaction between the hydroxyls pre-organized around the active centers and the polar groups of atrazine can activate the atrazine molecules by forming intermolecular forces such as hydrogen bonds and halogen bonds. In this way, the distribution of electron cloud density on the neighbor chemical bond is changed which can be attacked more easily by the active species (hydroxyl radical) in photoelectrochemical catalysis leading to fast bond cleavage, enhanced oxidation efficiency and dynamics. The molecular recognition and activation mechanism of atrazine as well as the influence of active centers on the efficiency of dechlorination, oxidation intermediates, and reaction pathway will be investigated in detail. Besides, the deep oxidation of atrazine in coexistence with other pollutants of different kind and concentration will be studied in order to evaluate the applicability for selective atrazine removal in real environment, and finally the proposed method will be applied in the selective and deep oxidation of atrazine in wastewater after biochemical processes. It is believed that the project will provide fundamental theoretical guidance for selective and deep degradation of chlorinated aromatic pollutants in real environment with high toxicity and low concentration.

针对含氯芳香污染物共存体系复杂、分子结构稳定、溶解度低、毒性大、可生化性差，难以实现选择性深度处理的问题，本项目以环境中典型有机氯农药污染物阿特拉津为研究目标，借助分子印迹技术在有序介孔TiO2电极表面构筑仿酶催化活性中心，使其能够选择性识别、结合目标分子；同时利用预组装在识别位点周围的羟基与阿特拉津极性官能团之间的卤键、氢键等分子间作用力，将阿特拉津分子活化，改变相邻化学键上的电子云分布，进而在光电催化产生的羟基自由基活性物种作用下，实现快速、高效断键和仿酶催化氧化。着重阐明仿酶催化活性位点对阿特拉津的分子识别与活化机制，明确阿特拉津氧化脱氯、降解中间产物和反应动力学过程；研究不同种类与浓度的共存污染物对阿特拉津在仿酶催化界面上的选择性去除效率的影响，并将该催化体系用于生化尾水中阿特拉津的选择性深度去除，为环境中其他低浓度、高毒性的含氯芳香污染物的高效深度处理提供理论指导。

含氯芳香污染物，如有机氯农药阿特拉津，是一类分子结构稳定、溶解度低、毒性大、可生化性差的有机污染物，其共存体系复杂，难以实现选择性深度处理。针对这一难题，我们借助分子印迹技术在有序介孔TiO2电极表面构筑仿酶催化活性中心，利用预组装在识别位点周围的羟基与阿特拉津极性官能团之间的卤键、氢键等分子间作用力，提高对阿特拉津的结合能力，实现对阿特拉津的选择性识别和活化，提高了对阿特拉津的光电催化降解能力。在实际废水体系中，MI-meso-TiO2表面，阿特拉津的选择性光电催化氧化效率达到91.7%，表观速率常数为0.25h-1，比在meso-TiO2表面提升了60.3%。. 进一步，针对含氯芳香污染物难氧化、易还原的结构特点，我们构筑了基于PdQDs@TiO2NTs的光阴极，实现了阿特拉津的高效、快速光电化学还原去除。在-1.3V条件下，5小时内阿特拉津的光电还原效率达到99.5%，反应速率常数为1.036h-1。研究表明PdQDs的修饰有利于光生电子空穴的快速分离，并且作为助催化剂对阿特拉津的还原起到了电催化作用。此外，阴极偏压的大小对阿特拉津的还原也起到了至关重要的作用。随着阴极偏压的增大，阿特拉津的还原机制从电助光催化向光电协同与光助电催化逐渐过渡。. 此外，烷基酚类也是环境中一类重要的低浓度、高毒性的有机污染物，由于其强的疏水性在光催化降解过程中很难有效吸附在亲水型催化剂如TiO2表面，不利于其有效的去除。因此针对这一问题，我们提出利用全氟辛基三乙氧基硅烷对亲水型二氧化钛纳米管表面进行疏水改性，增强壬基酚疏水污染物在催化剂表面的吸附，促进其催化氧化效果的提升。结果表明在40分钟内壬基酚的去除率达到了100%，相比于TiO2NTs表面壬基酚的去除率增长了约17%。同时，利用疏水催化剂表面与疏水目标污染物之间选择性的吸附和氧化，实现高毒性疏水污染物的优先去除。. 本项目研究为针对复杂体系内，特定环境污染物设计高效、选择性的光催化、光电催化体系提供了重要的实验基础，具有重要的理论和应用价值。.