生物炭介导希瓦氏菌还原FeOOH降解地下水氯代有机物污染机理

The applications of nanoscale zero-valent iron (nZVI) for degradation of contaminants have been received widespread attention due to its controllable particle size, high reactivity and abundant reactive surface sites. However, nZVI has a strong tendency to surface oxided which blocks the surface active sites and decreases the reaction rate. It has been reported that surface film of oxidized minerals often formed on the surface of nZVI. The negative effect of iron corrosion products on the reactivity of ZVI has become a major issue in the further development of nZVI technology. It is therefore significant to develop an method able to re-activation the aged nZVI to enhance removal efficiency of contaminants. In this work, based on biochar which has large specific surface area and high surface energy, and contains many functional groups, it could be used as electron shuttle to increase the electron transfer rate from iron reducing bacteria to aged ZVI. The aim is to establish the aged ZVI, biochar and iron reducing bacteria coupled system. chlorinated organic was selected as a representative target contaminants. The mechanism of biochar in reductive dechlorination of PCP by aged ZVI was discussed, and the mechanism of reduction dechlorination of target pollutants by system was also investigated. This study establish a system that enhance the activity of aged ZVI. It provides a theoretical basis for the popularization and application of zero valent iron technology in environmental remediation, and provides technical support for developing new groundwater remediation materials.

地下水环境普遍受到氯代有机物污染，对生态环境和人体健康造成严重危害，亟需进行修复；纳米零价铁是最具潜力的原位修复材料之一，但在地下水环境中容易发生钝化，生成铁氧化物覆盖在纳米零价铁颗粒表面，阻止零价铁与污染物反应。为提高钝化纳米零价铁的反应活性，本项目提出采用生物炭作为电子穿梭体介导铁氧化物与铁还原菌的电子传递过程，基于生物炭多孔结构可以将微生物和氯代有机物吸附于表面，形成局部富集，构建生物炭负载钝化纳米零价铁和铁还原菌耦合体系，研究还原脱氯转化氯代有机污染物的特性，采用电化学手段阐明生物炭介导希瓦氏菌还原钝化零价铁强化氯代有机物降解的机理；揭示铁还原菌氧化过程产生的电子通过呼吸链传递给生物炭过程，生物炭将电子传递给钝化零价铁的表面的FeOOH，使其还原成吸附态Fe(II)，提高钝化零价铁的反应活性，为阐明耦合体系强化地下水氯代有机污染物降解的生物地球化学过程及其环境响应机制提供科学依据。

卤代有机物（包括PCB、氯酚类）等大多属于典型持久性有机污染物，因其化学性质相当稳定，生物降解性差，导致氯代烃等典型有机污染物在环境中如水体沉积物或土壤有机质中发生积累，并通过生物富集进入食物链；同时还具有三致效应与遗传毒性，对环境构成了持久性污染，其中国内外研究者对持久性有机污染物生物降解、高级氧化和零价铁还原转化的机理、应用基础等方面作了大量的、系统的研究，其中异化铁还原菌与铁氧化物的交互作用对有机污染物的转化受到广泛关注。.纳米零价铁具有较大的比表面积和较强的反应活性，能够有效地去除环境中的有机污染物，是目前最具有应用潜力的高效还原剂之一，但由于其在处理污染物时表现出易钝化的缺陷，零价铁去除污染过程中生成的Fe2+/Fe3+会水解生成沉淀，覆盖在零价铁的表面形成钝化膜,阻止零价铁与污染物的进一步反应。为提高已钝化零价铁的反应活性,本课题基于EDDS具有较强的络合Fe(III)的能力，生物炭具有较大的比表面积和较高的表面能，含有多种官能团，能作为电子穿梭体，构建针铁矿、铁还原菌、EDDS交互体系以及钝化零价铁、铁还原菌和生物炭交互体系。以氯代有机类污染物为研究对象，研究耦合体系还原脱氯转化目标污染物的特性，阐述生物炭和EDDS分别在铁还原菌还原铁氧化物脱氯过程中发挥的作用，探明交互体系协同还原脱氯转化目标污染物的机理。研究结果表明：EDDS和生物炭均能有效促进铁还原菌还原零价铁表面的氧化物，提高钝化零价铁的反应活性。本研究构建出能解决促进钝化零价铁活性的耦合体系，为零价铁技术在环境修复中的推广和应用提供理论基础，对开发新型地下水污染修复材料提供技术支持。