纳米零价铁/生物碳增强地下水中铬还原-固定的机理及构效关系

Nanoscale zerovalent iron (nZVI) exhibits great potential of remediating chromium in groundwater, attracting considerable interests worldwide in environmental remediation sector, however, there is an urgent need to study the nZVI reunion mechanism that affects its activity and migration in groundwater. The project intends to use biochar (BC) as a carrier of nZVI, based on the structural evolution of nZVI/BC, elucidating the mechanism and regulatory processes of different composition and structure of biochar for nZVI reunion improvement; Focus on the mechanism of high efficient removal of chromium (Cr) by nZVI/BC, revealing the structure-activity of nZVI/BC and Cr removing; studying the integrated removing and regulation system of reduction-adsorption for Cr (Ⅵ) and Cr (Ⅲ) by nZVI/BC; Preliminary figure out the effect of Cr removing by enhanced nZVI migration and its key regulatory factors，and systematic study of the mechanism of Cr removal enhanced by nZVI and influence factor, providing a theoretical basis and technical guidance for Cr contaminated groundwater control and remediation.

纳米零价铁在地下水铬污染修复中巨大的应用潜力引起国际环境修复领域的极大关注，但地下水中纳米零价铁的团聚作用影响其迁移性和反应活性，亟需开展相关研究。本项目拟采用具有比表面积大和孔隙度丰富的生物碳作为纳米零价铁的载体，在搞清纳米零价铁/生物碳结构特征的基础上，研究不同组成和结构的生物碳对改善纳米零价铁团聚作用的机理及调控过程；重点探讨生物碳增强铬去除的机制，揭示纳米零价铁/生物碳结构与铬去除的构效关系，研究纳米零价铁/生物碳对Cr(Ⅵ)和Cr(Ⅲ)的还原-吸附一体化去除和调控机制；初步探明生物碳增强纳米零价铁迁移能力影响Cr去除的机理和关键调控因子，并系统研究纳米零价铁/生物碳增强对地下水Cr去除作用的原理及影响因素，为地下水中铬污染控制与修复提供理论依据和技术指导。

该项目针对纳米零价铁容易发生团聚作用降低其反应活性的瓶颈，采用吸附-还原法合成纳米零价铁-生物碳复合材料，并通过动力学、等温吸附、红外光谱表征、扫描电镜与能谱联用等方法系统研究了复合材料对铬的去除作用。结果表明，生物碳的酚类官能团和硅颗粒是六价铬还原-吸附的主要位点，将生物碳与纳米零价铁复合之后，硅是调控复合材料去除六价铬的关键因子，具体表现在：当铁碳比为1:1时，有机含氧官能团和硅颗粒为纳米零价铁提供负载位点，从而促进纳米零价铁对六价铬的还原作用；当铁碳比为4:1时，生物碳中的硅主导了纳米零价铁对六价铬的去除，生物碳中的硅为纳米零价铁提供吸附位点并促进其结晶化，增强对六价铬的还原；生物碳对反应产物的分散及硅颗粒可以促进复合材料对铬的吸附。同时，本项目还系统研究了纳米零价铁-生物碳复合材料的迁移特性、地下水中有机质及共存离子的催化和竞争机制等，为铁碳材料在铬污染地下水修复中的应用提供理论与技术支撑。