生物可降解络合剂调控磁铁矿类芬顿降解含水层介质中氯代烯烃的效能与机理

Iron containing mineral-catalyzed Fenton-like reaction is ideally suited to degrade the refractory organic contaminants, which has been considered as an attractive option for in situ remediation of groundwater contaminated with chlorinated solvents. However, the decomposition of hydrogen peroxide easily goes along the non-radical producing pathways, limiting the Fenton-like reactions. Here, we propose a novel modified Fenton-like reaction of magnetite with biodegradable chelating agent. The proposal is based on the applicant’s previous studies and the latest advances in the iron containing mineral-catalyzed Fenton-like chemistry. Chlorinated ethenes such as perchloroethylene (PCE) and trichloroethylene (TCE) in particular are the most common organic contaminants in groundwater. In proposed work, we will investigate the degradation of chlorinated ethenes in aquifers using the modified Fenton-like reaction of magnetite with biodegradable chelating agent, and the decomposition of hydrogen peroxide will also be investigated. We seek to investigate the fundamental interfacial reactions describing the solid surface complexation chemistry for the magnetite and the aquifers with chelating agent, and their interactions with hydrogen peroxide. On the basis of the interfacial reactions, the mechanism of the modified Fenton-like reaction of magnetite with biodegradable chelating agent will be proposed. We will identify the primary reactive species, the main degradation intermediates and the degradation mechanism of chlorinated ethenes. We speculate that the biodegradable chelating agent is capable of complexing iron and other metals to form complexes on the surfaces of the magnetite and the aquifers, and that the surface complexes may play a key role in enhancing the Fenton-like reaction and the stability of hydrogen peroxide. In view of the outstanding benefits of the Fenton-like reaction with the iron minerals, the proposed work will provide a good basis for in situ remediation of organic contaminants in groundwater.

含铁矿物催化类芬顿反应在处理难降解有机污染物方面极具优越性，有望为有机氯溶剂污染地下水的原位修复提供一种新途径。但过氧化氢易于通过非自由基路径分解，导致类芬顿效率受限。本项目基于申请人现有研究成果，并结合当前含铁矿物催化类芬顿反应最新研究进展，提出通过生物可降解络合剂调控磁铁矿类芬顿反应的新方法。以地下水典型有机污染物氯代烯烃为研究对象，研究生物可降解络合剂调控磁铁矿类芬顿反应对含水层介质中氯代烯烃的降解特性和过氧化氢稳定性的影响；通过研究微界面反应过程，揭示生物可降解络合剂对磁铁矿类芬顿反应的调控机理；鉴别主要活性基团和中间降解产物，探讨氯代烯烃降解机制。我们推测生物可降解络合剂在磁铁矿和含水层介质表面可通过配体交换作用形成表面络合体，能够有效增强类芬顿效率并提高过氧化氢稳定性。鉴于含铁矿物催化类芬顿反应在地下水有机污染原位修复方面的优越性，该工作具有重要的基础研究价值和潜在的应用价值。

氯代烯烃是地下水中最常见的有机污染物，具有较强生物毒性和潜在致癌性，环境危害较大。含铁矿物催化类芬顿（Fenton-like）反应在处理难降解有机污染物方面极具优越性，有望为氯代烯烃污染地下水的原位修复提供一种新途径。本项目提出了通过生物可降解络合剂调控磁铁矿催化Fenton-like反应原位降解地下水中氯代烯烃污染物的新方法。以典型氯代烯烃-三氯乙烯（TCE）为目标污染物，通过批实验和柱实验的方法，研究多种生物可降解络合剂（例如次氮基三乙酸（NTA）、(S,S)-乙二胺-N,N′-二琥珀酸（EDDS）、丙二酸、柠檬酸和植酸等）调控磁铁矿催化Fenton-like反应降解含水层介质中TCE的效能与机理。研究结果表明：NTA调控磁铁矿催化Fenton-like反应能够显著提升TCE的降解效果；而使用EDDS对TCE的降解效果产生了抑制作用；丙二酸、柠檬酸和植酸等络合剂则对磁铁矿催化Fenton-like反应的增效作用不显著。此外，系统地评估了络合剂使用量、磁铁矿含量和H2O2投加量等重要因子对TCE降解动力学和H2O2分解动力学的影响，构建了中性pH条件下高效的Fenton-like反应体系，实现了对含水层介质中TCE的原位降解和H2O2利用率的提升。最后，通过微界面反应过程揭示了络合剂对磁铁矿催化Fenton-like反应的调控机制，并且依据鉴别的主要活性基团和中间降解产物阐明了TCE的降解机理。本项目研究结果推动了以含铁矿物催化Fenton-like反应为基础的原位化学氧化技术（ISCO）取得新发展，为地下水中TCE以及其他有机污染物的原位处理提供了科学依据和参考，具有重要的理论价值和实际应用价值。