四聚磷酸亚铁活化分子氧增强型中性电-Fenton氧化系统构建及其有机农药污染物降解特性

Electro-Fenton technology shows advantages for treatment of recalcitrant organic pollutants. However, the low efficiency of H2O2 generation on the cathode hinders its application. Recently, we found that tetrapolyphosphate could significantly enhance the efficiency of the molecular oxygen activation to degrade atrazine by nanoscale zero valent iron (nZVI). This project aims to develop a novel electro-Fenton system by adding an inorganic ligand of tetrapolyphosphate (TPP) as electrolyte instead of Na2SO4. It is expected that the coupling of molecular oxygen activation by ferrous-tetrapolyphosphate complex with electro-Fenton oxidation could significantly enhance the organic pollutants degradation efficiency of this novel electro-Fenton system. The characteristics of iron species, the reactions on electrode, the types and formation of ROS will be studied in detail to reveal the mechanism of ROS generation in this novel electro-Fenton system. Both the kinetics and the degradation pathways of typical organic pesticides will be investigated as well to disclose the reaction mechanism between ROS and organic pesticides. Combining the electro-Fenton oxidation with molecular oxygen activaiton induced by ferrous-tetrapolyphosphate complex will not only improve the pollutant degradation efficiency, but also broaden the pH range. This project could provide portential for developing efficient green oxidation technology for pesticides pollution control based on molecular oxygen activation.

电-Fenton法在处理难降解有机废水方面表现出极大潜力，然而阴极电生H2O2效率不高制约了其应用。基于项目申请人关于四聚磷酸根能极大促进纳米零价铁活化分子氧降解阿特拉津的最新发现，本项目通过在电-Fenton体系中引入四聚磷酸钠替代硫酸钠作为支持电解质，构建一个四聚磷酸亚铁活化分子氧增强型高效电-Fenton氧化系统。本项目将系统研究四聚磷酸根对电极表面反应、铁物种变化以及活性氧物种形成的影响，揭示四聚磷酸亚铁活化分子氧增强型中性电-Fenton氧化系统的活性氧物种生成机制。以典型有机农药为对象，研究其降解动力学和降解机理，提出活性氧物种与农药分子的相互作用规律。本项目研究的四聚磷酸亚铁活化分子氧增强型中性电-Fenton氧化系统不仅能提高污染物降解效率，还能拓宽pH适用范围，为发展基于分子氧活化增强型高效电-Fenton氧化污染控制技术提供思路。

电-Fenton法的应用受到中性条件下阴极电生双氧水以及Fe(II)再生效率低的限制，因此本项目主要围绕四聚磷酸亚铁活化分子氧增强型中性电-Fenton氧化系统的构建以及活性氧物种与有机污染物的相互作用规律展开研究。项目首先设计了以四聚磷酸钠（Na6TPP）为支持电解质的电-Fenton体系，从双氧水生成途径及铁循环角度探讨了四聚磷酸亚铁活化分子氧增强电Fenton体系氧化效率的机理。研究结果表明阳极释放出的Fe2+与TPP形成的配合物通过单电子活化分子氧途径生成H2O2是该体系中污染物降解效率增强的主要因素。项目同时还制备了不同复合阴极材料，探讨了复合阴极材料对电Fenton体系的增强作用。在以负载Fe@Fe2O3纳米线的ACF为阴极的电Fenton体系中，污染物的降解效率和矿化效率明显提高。自由基捕获实验证明在该体系中铁纳米线单电子还原氧气产生•O2-，进而产生羟基自由基(•OH)是提高污染物降解和矿化效率的主要原因。而在以PPy@Fe2O3@CC为阴极的电Fenton体系中，阻抗测试及表面Fe(II)浓度变化情况表明聚吡咯（PPy）的包覆有利于电子传输，从而使Fe2O3表面的Fe(III)易于电还原为Fe(II)，进而提高电Fenton体系降解有机污染物的效率。项目还以不同氯酚为对象，分析了不同活性氧物种对有机污染物降解动力学和降解机理的影响，揭示活性氧物种与有机污染物的作用规律。研究结果发现随着氯原子数的增加，•O2–对于氯酚降解、脱氯以及开环的贡献越大。本项目研究结果有望为电Fenton体系的设计和应用提供一定的理论和技术基础。