调控反应性电化学Ti4O7陶瓷膜净化水中全氟化合物技术原理研究

Dr. Hui Lin will severe as the PI of this proposal, this limited-scope proposal aims at a proof-of-concept study to explore a novel reactive electrochemical filter (REF) technique to efficiency degradation target contaminants, PFOA and PFOS. By revealing the structure-activity relationship between the pore structure of Magnéli Phase Ti4O7-based electrochemical active membranes (Ti4O7-REMs) and contaminants mass transfer efficiency at Ti4O7-REMs during filtration, the optimal pore structure of the Ti4O7-REMs was then determined. Subsequently, the electrochemical properties and catalysis ability of the Ti4O7-REMs with pore structure optimized will be thoroughly characterized. High-resolution mass spectrometry (HRMS) in combination with 13C labeling will be used to investigate the mechanism of PFOA/PFOS electrochemical over Ti4O7-REMs surface in systems having complex background components such as dissolved organic matter (DOM). Finally, a laboratory scale Ti4O7-REMs-based REF (Ti4O7-REF) system operated in dead-end and/or cross-flow filtration mode with more than 5 L hr-1 treatment capacity will be assembled, and the Ti4O7-REF system will be systematic evaluated to degradation PFOA and PFOS under varying water and operation conditions. Findings in this proposal will provided the theoretical basis and basic data for developing efficient REMs, in addition, it also has important theoretical significance and application value for purification of contaminated water such as perfluorinated compounds contaminated water.

本申请课题以PFOA/PFOS两种典型PFCs为目标污染物，通过提高污染物在电化学体系中传质效率，发展出新型低能耗反应性电化学过滤（Reactive Electrochemical Filter, REF）水处理技术。主要研究内容：①通过揭示反应性电化学Ti4O7陶瓷膜（Ti4O7 Reactive Electrochemical Membranes, Ti4O7-REMs）孔结构与污染物传质效率之间的构-效关系，调控Ti4O7-REMs孔结构发展出高性能Ti4O7-REMs，并构建基于高性能Ti4O7-REMs的反应性电化学过滤（Ti4O7-REF）水处理装置；②从降解机理和反应动力学角度，提出调控目标污染物降解效率的方法与途径；③系统评价Ti4O7-REF水处理技术长期运行稳定性。研究结果将为发展高性能REMs提供基础数据和理论依据，对水中PFCs污染控制具有重要的理论意义和应用价值。

本项目以PFOA和PFOS为目标污染物，以提高污染物传质效率为切入点研发出高性的Ti4O7膜催化电极（Ti4O7-REMs），开展复杂背景基质条件下Ti4O7-REMs降解PFOA和PFOS有效性的深入研究，最终发展出高性能的基于Ti4O7-REMs的膜式电催化水处理技术（Ti4O7-REF）。项目组开发了高真空固态粒子烧结、真空等离体喷涂和真空放电等离体烧结3类Ti4O7-REMs的制备方法，并通过添加造孔剂或以不同孔结构多孔钛为基材或调控烧结压力等，实现了Ti4O7-REMs孔结构的定向调控制备。研究表明开发的Ti4O7-REMs具有优异的电化学性能，具有超高析氧电位（2.7 V vs. SCE）和电化学稳定性，羟基自由基（·OH）产率达2×10-9 mol cm-2 min-1（0.5 mA cm-2 ），电化学孔隙度达88.79%，粗糙系数（Rf）达1075.5。以K4Fe(CN)6为分子探针，通过极限电流法测定出不同孔结构Ti4O7-REMs的传质效率，优化了Ti4O7-REMs的孔结构。研究发现PFOA向Ti4O7-REMs的传质效率要高于PFOS，但PFOS更易在电极表面发生电子转移而降解。PFOA和PFOS的降解动力学随电极电位的增加而加快，高浓度Cl-会竞争反应位点降低它们的降解动力学，而低浓度Cl-，HCO3-和腐殖酸（HA）无明显抑制效应。实际污水测试表明Ti4O7-REMs能够有效降解共存高浓度有机物（43774 mg L-1 TOC）和盐度（6445 mg L-1 Cl-）等复杂背景基质污水中的各种典型多氟及全氟化合物（PFASs），包括PFOA、PFOS以及和大量未知的全氟化合物的前驱体，高分辨质谱分析表明Ti4O7-REMs对PFOA和PFOS降解为彻底矿化过程，具有很好的安全性, 长时间运行测试表明Ti4O7-REF技术能够长期稳定运行。