光伏驱动介孔炭块电极还原芳香硝基化合物的机理研究

Electrochemical reduction is one of the promising approaches transforming recalcitrant nitroaromatic compounds into biodegradable aromatic amines due to its environmental compatibility and amenability to automation. The process has disadvantages of poor catalytic activity of electrode materials, large interface mass transfer resistance in electrochemical reactors and high energy cost in wastewater treatment. In this research, hierarchical ordered mesoporous carbon monoliths with high mass transfer rate and calalytic performance are prepared by using phenolic resins as precursor, pluronic F-127 as soft template and 1,6-diaminohexane or lysine as catalyst under certain polymerization and carbonization conditions. The electrochemical reactor is constructed with three-dimensional mesoporous carbon monoliths as electrode and driven with photovoltaic solar energy to reduce nitroaromatic compounds. Combination of renewable solar energy with high-performance mesoporous carbon monoliths electrode can remarkably improve reduction efficiency and cut down water treatment cost. Adsorption-catalytic reduction coupling mechanism of nitroaromatic compounds on three-dimensional electrode is elucidated by systematically investigating electrode microstrucures and process parameters. The result can heighten the efficiency of electrochemical reduction and provide the theoretical basis and technology support for promoting its application to refractory organic wastewater.

电催化还原技术绿色清洁、操作简便，是将难降解芳香硝基化合物转化为易降解芳香胺化合物的最有效途径之一。针对现有电催化还原水处理技术存在电极催化还原能力不强和电化学反应器界面传质阻力大、能耗高的缺陷，本项目提出采用酚醛树脂为原料，聚醚为软模板剂，赖氨酸或乙二胺为催化剂，控制树脂合成和高温炭化条件，制备快速传质、高催化性能的介孔炭块电极，构建以清洁能源-光伏太阳能驱动的三维电极电催化还原反应器，处理废水中的芳香硝基化合物。太阳能与高性能介孔炭块电极结合会明显提高芳香硝基化合物的还原效果，降低水处理成本。借助微观结构表征和工艺参数考察，阐明芳香硝基化合物在三维介孔炭块电极上的吸附-还原耦合机理，为提高电化学还原水处理技术效能，促进其在难降解有机废水处理中的应用提供理论依据和技术支持。

传统电化学还原法处理芳香硝基化合物废水存在电极催化能力不强和电化学反应器界面传质阻力大、能耗高的缺陷。针对上述技术难题，本项目采用酚醛树脂为原料，聚醚为软模板剂，1,6-己二胺为催化剂，控制树脂合成和高温炭化条件，制备出传质快、催化性能高的介孔炭修饰电极，并构建了高效的动态电化学反应器，处理废水中的芳香硝基化合物。系统考察了循环进水流量、电流密度、电解质硫酸钠浓度、初始芳香硝基化合物浓度和初始pH值等因素对还原过程中芳香硝基化合物去除率、芳香胺化合物生成率和转化库伦效率以及氧化过程中有机物去除率和电流效率的影响规律，从能耗角度探讨了动态处理方式的优势及其原因。研究结果表明，制备的介孔炭电极材料比表面达500m2/g以上、孔结构规整，中孔发达，孔径集中在5nm左右。这种发达的中孔结构有助于芳香硝基化合物在电极表面的富集和还原，对芳香硝基化合物还原去除和芳香胺化合物生成效率都比未修饰电极提高10-40%。与传统静态反应器相比，本项目构建的动态电化学反应器对芳香硝基化合物去除率可提高20%以上，芳香胺化合物生成效率提高35%以上，COD和电流效率分别提高30%和25%以上，库伦效率增大2倍以上，能耗降低40%以上。芳香硝基化合物在阴极被还原为芳香胺化合物后，更容易在阳极被矿化降解，这为推动电化学技术在芳香硝基化合物废水处理中的应用提供了有力支持。