配离子改性蒙脱石的性能与重金属捕集模式的研究

Heavy metals are not biodegradable, released into the environment will cause pollution to water and soil, thereby cause toxic to humans after bioaccumulation. Most common disposal methods of heavy metal pollutants have the problem of heavy metal ions release under certain conditions. Design and preparation of heavy metal capture agent with the ability of permanent lock of heavy metal ions has practical significance. This project aims to modify the Na-montmorillonite with different weak stable coordination cation by using a standardized procedure established and improved. By using SEM, XRD, FT - IR, TG and other methods. the effects of the modification procedure on layer space and the apparent morphology of the product will be studied, and the interaction patterns of the complex cation with the inner surface of montmorillonite will be discussed. The interaction mode of the modified montmorillonite with the heavy metal ions and the relationship between the contribution from the coordination bond and the structure of the complex cation will be discussed based on the determination of absorption capacity, strength and the selectivity. The mechanism and the thermodynamics of the absorption will be discussed after the determination of absorption parameters of the general organic substances on the modified montmorillonite. By probing the interlayer microenvironment of the modified montmorillnite with molecular dynamics simulation, the absorption details of heavy metal ions on the modified montmorillnite will be discussed in the case of coexistence with water molecule and the common cations, and the manner of influence of the structure of the complex cations on the interlayer microenvironment of the modified montmorillnite will be revealed. The achievements of the program will be helpful and useful to the application of the montmorillnite modified with complex cations.

重金属不能被生物降解，排放到环境后会对水体、土壤造成污染，经生物富集后对人类造成毒害。常用的重金属污染物的处置方法大多存在着污染物重新释放的问题，设计和制备能够永久锁定重金属离子的重金属捕集剂具有实际意义。本项目用弱稳定阳性配离子为改性剂对钠基蒙脱石进行改性处理，研究改性过程对蒙脱石层间距、表观形态的影响，讨论配离子与蒙脱石内表面的相互作用方式。测定改性前后蒙脱石对重金属离子的吸附特性，研究配离子改性蒙脱石与重金属离子的作用模式，讨论配位模式的吸附贡献比与配离子种类与结构的关系。测定改性蒙脱石对有机污染物的吸附参数，研究吸附作用的机理和吸附过程热力学。用MM或MD方法模拟改性蒙脱石的层间微环境，研究在水分子、常见无机离子共存的情况下改性蒙脱石分别对重金属离子和有机污染物的吸附作用方式，揭示配离子的结构和种类对蒙脱石层间距和层间微环境的影响规律，为配离子改性剂的设计和选择提供理论和实验依据。

随着工农业的快速发展，各类污染物的排放和处理问题日益突出。水体中、土壤中残存的重金属离子和多种有机污染物已经严重危害到环境安全和人类健康。本项目选择吸附法进行废水处理，选取合适的改性剂对蒙脱石进行改性处理，改善其物理化学结构，提高其表面的疏水性能，从而提高其对有机污染物和无机重金属离子的吸附能力，可以大大拓宽蒙脱石在水处理及土壤环境修复中的应用范围。本项目成功制备了二乙烯三胺改性蒙脱石、氨基酸改性蒙脱石、表面活性剂改性蒙脱石、木质素磺酸钠改性蒙脱石、生物炭改性蒙脱石、氮化碳（g-C3N4）改性蒙脱石和磁改性蒙脱石等多种复合材料。采用FTIR、XRD、TG、SEM、BET等分析手段对样品进行性能表征。采用原子吸收分光光度计、紫外光谱等仪器分析改性蒙脱石与原钠基蒙脱石对重金属离子和有机污染物的吸附效果，发现新制备的复合材料对重金属离子及有机物的吸附效果明显优于钠基蒙脱石。研究了改性剂用量、反应温度、pH值、污染物的初始浓度、接触时间等因素对污染物去除效果的影响，并研究了吸附热力学和动力学。同时，采用Material Studio软件包中的Forcite 模块，选用UFF力场，构建了蒙脱石和改性剂、层间水分子以及吸附的有机物分子混合体系的晶体-非晶体模型，采用分子动力学模拟（MD simulation）计算了系统中各组分之间的相互作用、层间各组分的扩散系数、浓度梯度剖面、径向分布函数、相互作用能等参数。结合Multiwfn程序，计算静电势和平均离子局域化能，探讨活性吸附位点，从而从原子角度研究改性前后蒙脱石的吸附机理，为下一步合成新型高效低廉的吸附材料提供了技术支持。