芬顿法降解有机废气过程中粒子催化-传质耦合作用及其机制研究

Degradation of high concentration hydrophobic organic gaseous pollutants in Fenton reaction has always been limited by the extremely low gas-liquid mass transfer rate. In this study, by employing the enhancement of gas-liquid mass transfer by the dispersed particles, we endow the particles with catalysis and mass transfer enhancement effects simultaneously (C-M particles) by combining catalysts with nano-particles such as carbon nanotubes. Then, the C-M particles will be applied to Fenton reaction in a bubble column reactor. After observing the formation, breakup and coalescence of gas bubbles and measuring bubble sizes and the concentrations of organic gas in both gas and liquid phases, mass transfer coefficients will be calculated and the coupling effect also will be explored. Meanwhile, we introduce mass transfer enhancement factor as well as reaction rate factor to mass transfer models. By studying the effects of convective generated by reactor’s bubble, micro-scale convective of a particle’s Brownian motion and catalytic oxidation reaction on mass transfer enhancement, a more realistic mathematical model of gas-liquid mass transfer will be established. The research achievement of C-M particles may strengthen Fenton reaction in treatment of high concentration hydrophobic organic pollutants and provide a novel treatment method for atmospheric pollution in our country.

极低的气-液传质速率是芬顿（Fenton）氧化法降解高浓度疏水性有机气体污染物反应速率的限制因素。本研究利用分散相粒子强化气-液传质原理，创新性地将Fenton反应催化剂与传质强化粒子碳纳米管进行耦合，同时实现催化和传质强化作用。将催化-传质耦合粒子应用于泡罩塔Fenton反应体系中，分析气泡的形变、破裂和聚并形态特征，测定气泡的大小和气液两相的有机气体浓度，计算有效传质系数，探讨粒子催化-传质的耦合作用机制。在粒子传质模型中引入反应器鼓泡引起的对流项、粒子布朗运动导致的微对流强化传质项和催化反应项，建立更加符合实际的数理模型。本课题的顺利实施，可解决Fenton氧化法处理高浓度、疏水性气体有机物效率低的关键问题，可望为我国大气污染综合治理提供新途径。

非均相Fenton催化氧化法具有降解效率高、适用条件广、催化剂能够回收利用等优点，应用于有机废气污染物去除领域具有广阔前景。提高Fenton法降解有机废气的关键是提高气液传质效率和提高催化氧化效率，本项目以能够增强传质的碳材料与具有高催化氧化效率的Fe3O4复合制备出核壳结构Fe3O4@C，并将其应用于Fenton降解VOCs有机废气体系中，研究其对VOCs的传质-催化协同作用。通过一步水热法和牺牲模板法制备出两种核壳结构Fe3O4@C：实心型Fe3O4@C（178nm）和铃铛型Fe3O4@C（440nm），颗粒大小均匀，结构清晰，分散性良好，表现出超顺磁性，可以方便地从溶液中分离回收。分别研究了实心型Fe3O4@C和铃铛型Fe3O4@C在纯水体系和Fenton体系中的传质作用，通过对比体积传质系数，证明核壳结构Fe3O4@C相比于单独Fe3O4具有传质增强作用，在Fenton体系中传质增强因子分别为1.47和1.28。表明核壳结构外层碳的包覆可以提高催化剂传质作用。实验通过测定两种核壳结构Fe3O4@C和单独Fe3O4在Fenton体系中对VOCs的去除率，以及出气口CO2浓度、液相中CO2浓度、H2O2浓度和中间产物浓度，证明核壳结构Fe3O4@C对VOCs的去除效率大于单独Fe3O4，并且被降解的VOCs几乎都被氧化为CO2和H2O。由核壳结构Fe3O4@C在Fenton中催化氧化VOCs去除率大于其纯水吸附去除率和单独Fe3O4在Fenton中催化氧化VOCs去除率的加和，证实核壳结构Fe3O4@C对Fenton反应去除VOCs存在传质-催化协同作用。实心型Fe3O4@C和铃铛型Fe3O4@C协同因子分别为1.29~1.54和1.12~1.22。传质-催化协同作用的存在使得Fenton法处理VOCs去除效率显著提高。本项目的研究成果为促进Fenton体系的传质-催化协同效应，实现Fenton体系对有机废气的深度降解提供了理论研究基础和治理途径。