基于能量耦合的低渗透介质氯代烃电化学修复的体系建立和机制研究

Groundwater contamination by chlorinated hydrocarbons (CHCs) has become the world-wide environmental issues. During their migration, CHCs can enter and accumulate in the low permeable media, acting as the secondary pollution source which causes the constant back diffusion. Therefore, it requires great attention to remediate the CHC in the low permeable media. However, due to the mass transport limitation as a result of low permeability, most conventional technologies could not achieve the remediation goal. Electrokinetic (EK) remediation holds the promise as the mass transport can be greatly enhanced by the electric field. Till now, there are still some drawbacks, including the insufficient understanding of the mechanisms, and the lack of novel electrode reactions. In order to address these issues, this proposal proposed an enhanced electrochemical remediation system based on the EK approach. The new electrode reactions involve the cathode for advanced electrochemical oxidation, and the bioanode that can convert the chemical energy in the CHCs to electrical energy. It is hypothesized that hydrogen peroxide and •OH could be produced at the cathode for the transformation of the CHC to less toxic compounds, while the incomplete oxidation products can be further oxidized at the anode by the exoelectrogenic biofilm. The proposed system has the great advantage of energy saving. Based on this electrochemical system, we will investigate the migration and transformation mechanisms of CHC and its incomplete oxidation products in the electric field as the result of charge transfer, and study the synergistic effect of the electric field and the electrode reactions. We will also further investigate the optimal operating conditions to achieve the best performance with the low energy consumption, including the electrode configurations, spacing and the setting of current densities. This study will shed light on future research regarding the CHC remediation in the low permeable media.

地下水氯代烃污染是全球范围的重大环境问题。氯代烃在迁移过程中易在低渗透区域积累滞留，可以长期反向扩散，构成二次污染源，因此必须对低渗透介质中的氯代烃进行妥善的修复。然而受到低渗透介质水力传输的限制，许多修复技术的效果不佳。电动修复可以通过外加电场极大地加速氯代烃在低渗透地层的迁移，但是在电场迁移转化微观机理方面研究不足，在电极反应方面缺乏创新。针对以上需求和不足，本研究拟在电动强化迁移的基础上，开发新型电极，在阴极上原位生成过氧化氢和•OH，协同阳极的产电微生物对氯代烃进行氧化-矿化，同时实现化学能的耦合利用，形成一个功能协同、能量耦合的电化学修复体系。在此基础上，深入探索电场中由于电荷转移所引起的氯代烃和不完全氧化产物的迁移转化，解析其在电场-电极迁移转化的协同机制和影响因素，进一步探索最佳的电极布设方法、间距和运行条件，为低渗透介质中氯代烃污染的电化学修复技术奠定基础。

地下水氯代烃污染是全球范围的重大环境问题。氯代烃在迁移过程中易在低渗透区域积累滞留，移动性差、脱附难，导致修复效率低、易反弹。电动修复可通过外加电场加速氯代烃迁移，但是在电场迁移转化微观机理方面研究不足，在电极反应方面缺乏创新。针对以上需求和不足，本项目研发了多类电极材料，构建了电化学协同下的高效低耗的低渗透介质氯代烃修复系统，并探讨了溶解性有机质（DOM）对电化学修复能效的影响。主要研究成果包括：① 围绕氯代烃等污染高效净化研发/优化了3类电极材料：一是可在阴极上原位生成H2O2或•OH的高级氧化阴极，通过空气煅烧提升炭黑含氧官能团含量，使H2O2产率提高了8倍，并在电极上负载柠檬酸铁实现中性pH下•OH的原位高效生成；进一步优化了电极结构，研发半亲半疏水电极促进氧传质，构建漂浮式空气阴极并实现电极的放大。二是基于铜镍界面的“氢溢流”效应，开发了具有纳米片层结构的Cu-Ni双金属阴极，20 mA cm−2电流密度下90 min三氯乙烯（TCE）去除率可达99.7%；三是可通过电容吸附富集地下水金属离子的一维Mn3O4纳米棒电极，比电容量可达136.5 F g−1。② 构建了基于不同电极作用的低渗透介质氯代烃等污染电化学修复系统：构建了低渗透地层氯代烃电场强化迁移协同阴极电化学降解修复体系，TCE随电渗析流由阳极定向迁移至阴极，并在Cu-Ni阴极表面实现还原脱氯，TCE降解率>98%；研发了具有自供氧和自调节pH功能的双阴极电芬顿系统、自持能量驱动的铁-空气阴极高级氧化-絮凝协同净化系统、微生物降解耦合电化学法的氯代烃污染地下水修复系统，提升污染去除效率的同时极大降低能耗。③ 创新了DOM得失电子能力的定量表征方法，并初步探究其对电化学修复效率的潜在影响。上述研究丰富了对低渗透介质氯代烃污染电化学修复的认识，为修复中运行条件优化、系统能效提升提供了理论和技术支撑。相关成果以通讯作者发表论文13篇，其中第一标注5篇，第二标注8篇；获得国家发明专利授权7项。