生物炭基纳米零价铁对重金属的选择性吸附调控和机理研究

Remediation of heavy metals contaminated soil by biochar and nano zerovalent iron (nZVI) is a hot topic in recent years. However, the former is limited by the selective adsorption of heavy metals and the latter is easy to be agglomerated, which are still the urgent problems that need to be solved in the current academe. In response to solve the problems of the remediation of contaminated soil induced by biochar and nZVI alone, a new type of biochar-nZVI composite will be synthesized to study the coupling mechanism of high efficiency and selectivity. By adjusting the contents of oxygen functional groups and iron, the influence factors of the composite on the selective adsorption capacity of different heavy metals will be investigated. Combined with the simulation experiment, infrared spectroscopy, X-ray diffraction technology, synchrotron radiation technology and so on, the remediation effect and the adsorption sites of heavy metals will be analyzed. The 3D structure model of the composite will be constructed by molecular mechanics and molecular dynamics simulation. The selective adsorption ability of heavy metals to the composites is quantitatively evaluated by hybrid density functional theory, and the selective adsorption mechanism will be elucidated as a whole. The implementation of this project can be applied for selective removal of heavy metals as a specific target with better economics and high efficiency. What's more, the results can further improve the relevant theory of remediation, and provide scientific basis for the application of biochar-nano zerovalent iron in the remediation of soils contaminated by heavy metals.

利用生物炭、纳米零价铁（nZVI）修复重金属污染土壤是近年来的研究热点，但前者在重金属选择性吸附方面的限制及后者易团聚的缺点仍是当前学界亟需解决的问题。本项目旨在针对生物炭和nZVI单独修复重金属污染土壤存在的问题，构建新型生物炭基纳米零价铁，研究其高效高选择性的耦合机制。通过调节含氧官能团和铁含量，探究该复合材料对不同重金属的选择性吸附能力的影响因素；结合模拟实验和红外光谱、X-射线衍射技术、同步辐射技术等，分析其对重金属的修复效果及吸附固定位点；应用分子力学和分子动力学方法构建该复合材料的三维结构模型，并通过杂化密度泛函方法定量评价其对重金属的选择性吸附能力，从而整体上阐明其选择性吸附机理。项目的实施可经济、高效地将重金属作为特定靶标选择性去除，研究结果可进一步完善重金属污染土壤修复的相关理论，为生物炭基纳米零价铁在重金属污染土壤修复中的应用提供科学依据。

利用生物炭、纳米零价铁（nZVI）修复重金属污染土壤是近年来的研究热点，但前者在重金属选择性吸附方面的限制及后者易团聚的缺点仍是当前学界亟需解决的问题。本项目旨在针 对生物炭和nZVI单独修复重金属污染土壤存在的问题，构建新型生物炭基纳米零价铁，研究其高效高选择性的耦合机制。主要研究内容和进展包括：（1）通过调节制备温度和铁含量，探究了该复合材料的结构特性及对不同重金属的选择性吸附能力的影响因素。随着制备温度的增加，C/Fe复合材料对Pb(II)和Cd(II)的去除能力及对Pb(II)的选择性吸附能力增强；随着铁含量的增加，C/Fe复合材料对Cr(VI)和As(III)的去除能力及对Cr(VI)的选择性吸附能力增强。（2）结合红外光谱、X-射线衍射技术、同步辐射技术等，分析了其对重金属的吸附固定位点。Cr(VI)的还原产物包括FeCr2O4, (CrxFe1-x)(OH)3, Cr3+, Cr(OH)3, 和Cr2O3，As(III)的氧化产物主要是AsO43-。C/Fe复合材料中生物炭的OH 和 C-O 基团是Cr(VI)的吸附位点，而氧化产物γ-FeOOH是As(III)的吸附位点。（3）通过模拟实验分析C/Fe复合材料对土壤中重金属的修复效果。室内模拟实验显示土壤培养14天后，将C/Fe复合材料用磁铁与土壤进行分离，C/Fe复合材料对土壤中Cd和As的修复效果显著，修复14天后均降低到风险筛选值以下。（4）应用杂化密度泛函方法对构建的生物炭的三维结构模型进行优化，并定量评价其对重金属的选择性吸附能力，从而整体上阐明其选择性吸附机理。结果显示生物炭中的COOH和OH能与Cr(VI)形成配位化合物或者H键，相互作用能较大。O与Cr(VI)之间较强的相互作用是材料对Cr(VI)进行选择性吸附的原因。项目的实施可经济、高效地将重金属作为特定靶标选择性去除，研究结果可进一步完善重金属污染土壤修复的相关理论，为生物炭基纳米零价铁在重金属污染土壤修复中的应用提供科学依据。