电化学循环井耦合氧化 -还原降解地下水中三氯乙烯

三氯乙烯（TCE）是一种地下水中常见的有机污染物，传统的地下水循环井修复技术虽然有效但耗时长，且需配套地面处理。文章研发了一种电化学循环井耦合修复体系，以期通过顺序化学氧化 -还原作用高效快速降解地下水中TCE。以地下水循环井为基础，通过抽水井中的地下水电解，原位提供O2和H2，投加Fe（Ⅱ） -EDTA络合物活化O2产生羟基自由基氧化降解TCE，进而利用钯催化剂催化剩余的H2还原降解TCE。在二维砂槽模拟含水层中评价了该体系的运行效果，含水层中初始TCE浓度为7.50 mg/L，经过13天的连续通电处理后，TCE浓度降低到1.65 mg/L，降解率达到78%。处理后Cl-浓度相应增加118.20 μmol/L，接近于TCE降解量（44.50 μmol/L）的3倍，证明TCE近乎完全脱氯。运行过程中，TCE平均降解速率由0~5 d的0.90 mg/(L·d) 降低到9~13 d的0.10 mg/(L·d)，氧化降解主要发生在前期阶段，钯催化还原效率较为稳定，后期两种过程降解效率都逐渐下降，主要原因是溶解态Fe（Ⅱ）浓度减少以及钯催化剂活性降低。该耦合修复体系是基于地下水循环井技术的改进，其氧化 -还原作用机理有望实现地下水中多种不同有机污染物的降解。

Electrolytic circulation well coupled with oxidation and reduction for trichloroethylene degradation in groundwater

Trichloroethylene (TCE) is a common organic pollutant in groundwater. Traditional groundwater circulation wells (GCW) are effective but time -consuming and requires ground treatment. This study develops a coupled system for treating TCE -contaminated groundwater through sequential chemical oxidation and reduction. In this system, groundwater is circulated by two separated wells, and electrolysis in a pumping well is utilized to generate O2 and H2 in situ. To degrade TCE, Fe（Ⅱ） -EDTA is added to activate O2 to hydroxyl radicals for oxidation, and Pd catalyst is coupled to catalyze H2 for reduction. The system performance is evaluated in a 2D sandy tank. The initial TCE concentration in the tank is 7.50 mg/L. After 13 days of continuous electrolytic treatment, TCE concentration decreases to 1.65 mg/L (78%). The corresponding increase in Cl-concentration (118.20 μmol/L) is nearly three times that of the decrease in TCE concentration (44.50 μmol/L), which proves the near complete TCE dichlorination. During the operation, the average degradation rate of TCE decreases from 0.90 (0~5 d) to 0.10 (9~13 d) mg/(L·d). Oxidative degradation mainly occurres in the early stage, and catalytic reduction efficiency is relatively stable. The degradation efficiency of both mechanisms decreased gradually in the later stage, which is attributed to the decreased concentration of dissolved Fe（Ⅱ） and decreased activity of Pd catalyst. The coupled system is an improvement of GCW technique, which is feasible for oxidizing and reducing a wide range of different organic contaminants.