活性炭载纳米铁还原-生物反硝化耦合去除地下水中硝酸盐的机制

Groundwater nitrate pollution is a global environmental problem, and recently, the mechanism and technology for nitrate remediation has been paid more and more attention in hydrogeology because of its difficult efficient removal from groundwater. Therefore, the proposal intends to investigate the characteristics of activated carbon-supported nano-iron composite material and its control effect to nano-iron agglomeration; to explore the ability of the composite material to nitrate reduction promotion and ammonia byproduct inhibition as well as the features of regulating hydrogen formation in nitrate reduction owing to the internal iron-carbon micro-electrolysis effect. Subsequently, the process and characteristics of hydrogen supply to achieve autotrophic denitrification efficiently also will be studied intensively. Furtherly, the possibility, characteristics and hydrogeochemical factors of removal nitrate from groundwater by coupling reduction of activated carbon-supported nano-iron with autotrophic denitrification will be researched. In order to ascertain the relationship between hydrogen generation and chemical reduction of nitrate by the composite material, this study will emphasis on the mechanism of nitrate removal in groundwater by the coupling system of activated carbon-supported nano-iron with autotrophic denitrification. Based on these results, the synergistic mechanism of nitrate removing from groundwater by chemical reduction coupling with autotrophic denitrification will be revealed, and efficient nitrate removing method from groundwater in-situ by coupling activated carbon-supported nano-iron reduction with biological denitrification will be built. Consequently, the achievements will provide a theoretical basis for development economic and secure prevention techniques for nitrate pollution groundwater.

地下水硝酸盐污染是全球性的环境问题。关于其修复的机理与技术一直是水文地质学研究的热点。本项目拟研究活性炭载纳米铁复合材料的结构特点，探究其还原硝酸盐过程中对纳米铁不稳定、易团聚等不足的控制作用，铁-碳微电解效应促进硝酸盐还原和抑制副产物氨氮产生的能力与机制，以及对氢气形成与传质过程的调控规律；研究氢气的传质特征在实现自养反硝化作用高效去除硝酸盐过程中的作用；进而研究活性炭载纳米铁还原与生物自养反硝化耦合去除地下水中硝酸盐的可能性、特点及规律，以及水文地球化学因素对耦合作用的影响，旨在探明活性炭载纳米铁的结构特征与化学还原作用、氢气传质过程及生物反硝化作用之间的构-效关系，揭示化学还原-生物反硝化耦合去除地下水中硝酸盐的协同作用机制，构建高效去除地下水中硝酸盐的活性炭载纳米铁还原-生物反硝化耦合方法，为拟订经济安全的地下水硝酸盐污染防治方法提供理论依据。

众所周知，水污染和水危机是全球性的环境问题，地下水作为宝贵的饮用水源，对保障居民饮水安全具有举足轻重的作用。然而，地下水硝酸盐污染已成新常态，并呈恶化趋势，因此，探索和发展高效经济的地下水硝酸盐污染防治方法成为环境与水文地质领域研究的重点。.项目针对活性炭载纳米铁还原-生物反硝化耦合去除地下水中硝酸盐的机制，研究了活性炭种类、铁源、表面活性剂和制备途径对活性炭载纳米铁复合材料(nZVI/GAC)结构的影响，运用批处理实验研究了化学还原去除硝酸盐的功效与氢气产生机制，利用微环境实验研究了生物自养反硝化去除硝酸盐的功效与氢气的传质特点，基于纳米铁的还原和产氢作用，将化学还原与生物反硝化耦合，构建出nZVI/GAC还原-生物反硝化耦合的体系，探明nZVI/GAC的结构特征与化学还原、氢气传质、自养反硝化之间的构-效关系，揭示出化学还原-生物反硝化耦合去除地下水中的硝酸盐不仅可能，而且可行，还具有显著的增效作用。.研究发现，通过液相还原法，先吸附后还原，制备的nZVI/GAC的结构相对较好，活性炭的介入，对纳米铁的团聚、稳定性和活性具有显著的改善作用；nZVI/GAC在地下水硝酸盐去除过程中能够形成铁-碳微电解效应，活性炭作为电子传递的通道，显著提高电子传递的效率，从而促进氢气的产生，提高硝酸盐的化学还原效率，抑制氨氮、亚硝态氮等副产物的产生，这种促进作用受水化学条件(如pH值、离子强度等)的影响；活性炭还具有载体作用，便于微生物富集，快速形成生物膜，提高化学-生境耦合脱氮功效，以至于活性炭载纳米铁还原-生物反硝化耦合去除硝酸盐具有显著的增效作用，但耦合作用的发挥受nZVI/GAC用量、硝酸盐初始浓度以及共存小分子有机碳的影响。项目取得的成果，对促进化学-生物协同脱氮机理研究，具有重要的学术价值，为寻找高效经济的地下水原位脱氮方法提供了新思路和新方法，具有潜在的实际应用价值。