多级孔碳monolith阴极产•OH的原理及矿化难降解有机物的性能

Electro-Fenton is considered to be one of promising advanced oxidation technologies for the control of toxic pollutants reluctant to the conventional biological or chemical treatments. Benefiting from good mass transfer, its homogeneous type always performed high efficiency in decomposing pollutants. However, the disadvantages, such as rigorous restriction to pH value, iron hydroxide precipitate and suffering in catalyst separation, limited the practical application. Although the heterogeneous type may overcome these shortcomings, the slow interface reaction and long mass transfer distance have inhibited the production rate of •OH, which is several orders of magnitude lower than that of homogeneous type. Therefore, how to improve the efficiency of •OH generation is one of the most important scientific topics in this field. Inspiring by electrochemical filter, nanoreactor and sharp-tip effect for enhancing electric field, this project will fabricate a series of carbon monolith derived from nature wood and etch its channel with millimeter-diameter diameters to produce mesopores and millipores. The aim is to speed up H2O2 production, generate •OH via in-situ activation of H2O2 and bridge the distance between pollution and •OH to enhance mineralization. The results will be significant for not only the generation and utilization of •OH during electro Fenton process but also the application of hierarchical porous carbon monolith in other advanced oxidation processes.

电芬顿是最有应用前景的高级氧化技术(AOP)之一，在难降解有机物分解方面受到广泛关注。其均相形式具有传质方面的优势，可高效分解污染物，但存在必须在酸性条件工作、容易产生铁泥、催化剂分离困难等缺点。非均相形式可以克服上述缺点，但受界面反应速度及传质距离的限制，生成•OH的动力学常数比均相过程小几个数量级。本项目结合电化学过滤器、纳米反应器、尖端电场理论，提出可利用具有微米直径有序通道、通道表面有大量介孔和微孔的碳monolith阴极加快H2O2生成速率、原位产生•OH、缩短污染物传质距离，使污染物分解在原水流经多级孔电极过程中高效地完成，实现非均相体系获得接近均相反应效率。预期成果不但能提高电芬顿技术•OH产率和利用率，而且对促进这种新型monolith材料在其他AOP中应用具有借鉴价值。

电化学是工业废水深度处理及回用的关键技术之一。电化学技术通过电极与水的固液界面反应实施氧化还原去除污染物，强化污染物迁移到电极表面附近与电子、活性氢、•OH等活性物种的接触，可缩短停留时间、节能提效，是推动电化学技术规模化应用的关键。本项目研制出多通道碳monolith电极，通道直径10-50微米可控，通道壁上有大量直径1-5微米的孔，建立了通道壁含氧基团的调控方法，揭示了微通道、微孔、含氧基团与电化学还原溶解氧产H2O2和•OH的构效关系。将污染物到活性物种的扩散距离限制在微米尺度，实现了停留时间120s完全矿化污染物，速度与均相芬顿效率相当。提出微通道曝气电极的思路和方法，H2O2产量达到4.34 mg/(h∙cm2), 能耗仅7.35 kWh/kg，30 mL溶液30min反应累积浓度可达476mg/L，满足实际水处理去除COD的要求。发明了大面积木头碳微通道电极的制备方法，电极面积已做到2500cm2。建立了中空纤维膜阵列阴极、纳米FeOCl修饰木头碳电极的制备方法，探索了通过串并联放大反应器的方法，研制各类反应器3台，在氧还原产H2O2、活化H2O2产OH、有机物降解、海产养殖循环水硝酸根还原、工业循环冷却水硬度去除等方面的性能均明显优于普通电极和常用反应器。