非均相金Fenton催化体系中羟基自由基生成的构-效关系研究

Generally, advanced oxidation processes (AOPs) are based on the in situ generation of powerful oxidizing species obtained at a sufficient concentration to effectively decontaminate waters. In specific, the generation efficiency of hydroxyl radical from H2O2 decay in Fenton reaction is of critical importance for the oxidative degradation of refractory micro- pollutants. Heterogeneous Au Fenton-like system was greatly developed since 2008, due to the high stability toward acidic conditions, high productivity of hydroxyl radicals and the feasibility of enhancement by photo-/electro- fields. However, the structure- performance relationship of hydroxyl radical generation over heterogeneous Au Fenton catalyst is rarely studied owing to the complicated mechanism of hydroxyl radical generation towards the surface structure and reaction condition, respectively. In this study, by using the modified ion exchange method, Au/C catalysts with specific particle size, interface morphology and electronic property will be prepared. The catalytic performance for Fenton degradation of benzoic acid (BA) will be evaluated. On the basis of H2O2 decomposition rate, O2 generation rate and BA decay rate, the kinetics behavior of hydroxyl radical generation will be modeled by the non-linear fitting with multiply factors. The relationship between catalyst structure and the radical production will be built up. The results will help to design rationally of AOPs system and to reveal the insight on mechanism of oxygen over heterogenous Au catalysts. Eventually, the present research will be greatly contributed to the water pollutant control.

以Fenton为代表的高级氧化反应依靠过氧化氢分解产生羟基自由基，实现难降解有机物的去除，其中羟基自由基的生成直接关系高级氧化技术的效率。非均相Au基Fenton催化体系化学稳定性好、自由基生成效率高、易被光/电强化、发展潜力高。非均相Fenton催化反应兼具表面结构敏感性和反应环境敏感性，羟基自由基生成与非均相催化剂表面的构-效关系尚不明晰。本研究拟采用改性离子交换法，在活性炭表面制备粒子大小与界面尺寸可调、电子状态可控的负载型Au/C催化剂。以苯甲酸为探针分子，同时测定H2O2分解速率、O2生成速率和苯甲酸降解速率，应用多参数非线性拟合，建立基元反应动力学模型，得出羟基自由基生成速率与效率，构筑Au-Fenton体系中羟基自由基生成的构效关系。研究方法及结论可指导高级氧化体系的理性设计，并可揭示Au催化体系中氧活化原理及调控机制，为探索绿色高效的污染控制方法开辟新思路。

本研究从负载型纳米金Fenton催化体系入手，研究了Au/C催化剂对过氧化氢的分解动力学和催化活性的构效关系。Au/C催化剂的自由基生成效率可达30%，尽管这一数值低于文献上已知最佳的Au/纳米钻石体系，但考虑到活性炭价廉易得，仍具有一定的发展潜力。提出了基于双活性中心拟酶机理的动力学模型，用以描述Au/C 催化剂催化过氧化氢分解和羟基自由基生成过程中的非线性现象。自由基生成的单电子 转移过程易受到过氧化氢过渡覆盖的竞争性抑制，从而发生双电子转移，产生无效分解 产物氧气。即在Au/C多相Fenton催化过程中可能存在动力学反应速率与自由基生成速率之间的制约关系。进一步，与美国Rice大学、杜邦公司和国际黄金协会建立了联系，了解到贵金属特别是金催化环境修复的应用前沿，并调整采用全生命周期分析的策略预估了Au-Fenton催化体系的应用潜力和发展瓶颈。