抗坏血酸强化含水层介质Fenton降解PNP研究

为解决Fenton技术在地下水有机污染的原位修复中铁基材料难注入、降低二次污染的问题，并拓宽适用的pH范围. 以含水层介质(aquifer medium，简称“AM”)中的铁矿物为铁源，综合考虑区域地下水系统分区、地质类型和地质时代，采集京津冀5处典型地区浅层含水层介质，以天然还原剂/配体-抗坏血酸(ascorbic acid，简称“AA”)为强化试剂，构建了AM/AA/H₂O₂体系，并探究该体系对硝基苯酚(PNP)的降解效能以及环境pH对PNP降解的影响，同时揭示了AM/AA/H₂O₂体系降解污染物的机制. 结果表明:①五处含水层介质主要为长石类介质和碳酸盐类介质，表面都均匀分布了一定量的铁矿物，且以长石类介质催化H₂O₂分解降解PNP效果较好. ②抗坏血酸可显著促进含水层介质催化H₂O₂分解降解PNP，反应40 h内PNP的去除率最高可在89.00%以上(TOC的去除率为84.03%)，与未加抗坏血酸的体系相比提升了6.82倍. ③降解PNP的主要功能自由基为·OH，是由液相中经抗坏血酸络合的铁离子催化H₂O₂分解产生的. ④与传统Fenton体系相比，抗坏血酸可有效拓宽AM/H₂O₂体系适用的pH范围，初始pH在5~10的范围内对PNP的降解无显著影响. 研究显示，AM/AA/H₂O₂体系在地下水有机污染的原位修复中具有较大的应用潜能. 

Research on Degradation of PNP with Enhanced Aquifer Media Fenton System by Ascorbic Acid

In order to solve the problems of difficulty in injecting iron-based materials and the secondary pollution in the in-situ remediation of organic contaminated groundwater by Fenton technology, and to broaden the applicable pH range, iron minerals in aquifer medium (AM) were taken as the iron sources in this study. Considering the groundwater system, geological type and geologic age, shallow aquifer media in five typical areas of Beijing, Tianjin and Hebei were taken. The natural reducing agent/ligand-ascorbic acid (AA) was used as the strengthening reagent to construct the AM/AA/H₂O₂ system. The degradation efficiency of organic pollutants (p-nitrophenol, PNP), effect of environmental pH were explored, and the degradation mechanism of PNP by the AM/AA/H₂O₂ system was also revealed. The results show that: (1) The main rock types of the five aquifer medium were feldspar and carbonate, and iron was distributed evenly on their surface. Among the five aquifer medium, feldspar media showed good catalytic efficiency for PNP degradation. (2) Ascorbic acid significantly promoted the catalytic decomposition of H₂O₂ in aquifer medium, therefore promoting the degradation rate of PNP. The maximum removal rate of PNP reached more than 89.00% within 40 h (the remove rate of TOC=84.03%), which is 6.82 times higher than that without ascorbic acid. (3) The main functional radical for PNP degradation is ·OH, which is mainly produced by the catalytic decomposition of H₂O₂ by ascorbic acid complexed iron ions in the liquid phase. (4) Compared with the traditional Fenton system, ascorbic acid can significantly broaden the applicable pH range of AM/H₂O₂ system, and the initial pH in the range of 5-10 has no obvious effect on PNP degradation. These results indicate that the AM/AA/H₂O₂ system has a great application potential in the in-situ remediation of organic contaminated groundwater.