g-C3N4 固载的单原子分散Pd催化剂及其催化PBDEs深度还原脱溴

Polybrominated diphenyl ethers(PBDEs) is a group of organic pollutants being resistant to completely reductive debromination. Since there are few methods which can achieve deep reduction of PBDEs, it is still urgent to develop new methods to achieve deep reduction and debromination of PBDEs. On the basis of catalytic activity of noble metal Pd, a single-atom dispersed Pd catalysts immobilized on g-C3N4 is designed and prepared in this proposal. The strong interaction between Pd atoms and the cavities formed by six C3N4 rings on the layered structure of g-C3N4 leads to the stabilization of Pd atoms, which can improve both atom economy and catalytic activity of noble metal Pd. The adsorption of PBDEs on the surface of catalysts is enhanced by strengthening the matching effect of benzene-π system in PBDEs with the conjugated structure of g-C3N4. For the purpose, this proposal will systematically investigate the adsorption behavior and degradation performance of PBDEs, coupled with the mechanism of deeply reductive debromination on the surface of single-atom dispersed Pd catalysts. By the optimization of degradation conditions and preliminary application for treating practical liquid waste with PBDEs, a novel method for completely debromination of PBDEs is developed, which is not only efficient and low-cost but also convenient for the large-scale application. This proposal will provide an alternative approach to treat PBDEs on a large scale, which is significant in both environmental science and technology.

多溴联苯醚（PBDEs）是一类难以深度还原脱溴的有毒有机污染物。目前能使PBDEs高效深度脱溴的方法不多，急需研究能催化PBDEs深度还原脱溴的新方法。本项目以贵金属Pd催化还原为中心，设计并制备g-C3N4固载的单原子分散Pd催化剂；利用g-C3N4层状结构中六个C3N4环形成的空腔对Pd原子的束缚作用，实现Pd的单原子分散，提高贵金属Pd的原子经济性及其催化活性；借助g-C3N4共轭π电子与PBDEs分子中苯环π体系的匹配效应，强化催化剂对PBDEs的捕集。针对PBDEs的深度脱溴过程，系统地研究PBDEs在载体以及催化剂表面的吸附和降解行为及其深度还原脱溴机制；优化反应条件，结合在处置实际废液中PBDEs的初步应用，提出一种效率高、成本低、便于规模化操作的催化PBDEs深度还原脱溴新方法。本项目的实施可为规模化处置PBDEs提供一种新思路，具有重要的科学意义和工程应用前景。

多溴联苯醚（PBDEs）是一类难以深度还原脱溴的持久性有机污染物。目前能使PBDEs高效深度脱溴的方法不多，急需寻找能够催化PBDEs深度还原脱溴的新方法。PBDEs的还原一般可由电子或活性氢主导，本项目基于这两种还原途径，并结合PBDEs的分子结构特点主要进行了如下工作：在以电子进攻为主导的进攻方式中，建立了PBDEs的还原降解速率与溴原子数目更多的苯环上的溴原子数和ELUMO之间的关系，阐明了低溴代联苯醚难以继续被电子还原的原因，并设计了RGO/TiO2光催化还原-氧化接力“一锅法”降解BDE47的新体系，通过耦合氧化体系实现低溴代联苯醚在以电子进攻为主导的体系中的完全矿化脱溴；在以活性氢进攻为主导的进攻方式中，建立了Pd/g-C3N4可见光光催化深度还原降解BDE47的体系，解释了Pd在促进光生电荷分离、产生活性氢以及弱化C-Br键等方面的作用。建立了Cu/TiO2-N2H4•H2O超快速深度处理BDE47的新体系，利用体系的催化转移加氢过程实现了BDE47在温和条件下的超快速深度脱溴。建立了Pd/TiO2-NaOH化学催化BDE47脱溴的新体系，提出了BDE47在Pd表面加氢脱溴和偶联脱溴的反应路径和机理。以上方法的建立和机理的阐述为设计和构筑高效处理卤代污染的体系提供了新的思路，具有重要的科学意义和工程应用前景。