表面固载离子液体材料的制备及其在环境样品前处理中的应用

The materials prepared by immobilizing ionic liquids (ILs) on surface of solid supports can not only maintain the excellent absorption performance of ILs for environmental pollutants, but also decrease the dosage of the ILs and avoid their loss. Thus, it is a class of environmentally friendly material for air and water. In this project, surface immobilized ILs materials will be prepared by chemical bonding of cations of ILs or their structural analogs on the surface of chloromethyl polystyrene and magnetic carbon nanotubes. After that, micro-structure and properties of the materials will be characterized by Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), IR/Raman spectra, Thermo -gravimetric Analysis (TGA), and Brunauer-Emmett-Teller (BET) techniques. The influences of chemical structure of ILs, surface structure of solid supports, pH value of aqueous solution and extraction temperature on the selective adsorption of environmental pollutants are systematically investigated. The inherent relationship between the material structure and adsorption performance is also discussed. The adsorption mechanism will be analyzed from the study of adsorption capacity, adsorption dynamics, binding site, binding constant and the lowest adsorption concentration of the environmental pollutants. Based on these results, the micro-column packed with surface immobilized IL material will be prepared as a solid phase extraction column, and the column parameters such as the column adsorption capability, its regeneration and recyclability will be also investigated. Thereafter, new methods for rapid separation and determination of low level of pollutants will be established based on on-line solid phase extraction coupled with chromatography or molecular spectrophotometry determinations. It is expected that these studies would provide basic knowledge for the development of new methods and technologies for the pre-treatment of environmental samples and deep treatment of waste waters.

固载离子液体既可保持离子液体的优良吸附性能，又可显著减少离子液体的用量，防止离子液体的流失，是一类对大气、水体更加友好的环境材料。本项目拟采用化学接枝技术，将离子液体的阳离子或其结构类似物键合在氯甲基聚苯乙烯、磁性碳纳米管等载体表面，制备表面固载离子液体新材料。利用电镜、红外/拉曼光谱、热分析、比表面积等手段对材料的微观结构进行表征。系统研究离子液体的化学结构、载体的表面结构、溶液pH值、萃取温度等对环境污染物的选择性吸附性能的影响规律，认识材料的结构与吸附性能的内在关系。通过吸附容量、吸附动力学、结合位点、结合常数、最低吸附浓度等参数的研究，分析固载离子液体的吸附机理。在此基础上，制备固载离子液体固相萃取柱，考察柱容量、再生及循环使用等固相萃取参数，并与色谱、分子光谱等检测技术联用，建立对痕量环境污染物的快速分离分析新方法，为其在环境样品前处理及废水深度处理中的应用提供科学依据。

本项目采用化学接枝技术，分别以氯甲基聚苯乙烯树脂、磁性纳米材料和介孔材料为载体，设计合成了17种吸附性能优良的表面固载离子液体新材料。研究了离子液体的结构、链长、官能团的特性、阴离子的类型、载体的表面结构、溶液pH值、萃取温度等因素对固载离子液体材料的物理化学性质、微观结构以及对环境污染物的特异吸附性能的影响规律，考察了固载离子液体材料对污染物的吸附容量、吸附动力学、吸附模型、最低吸附浓度等参数，探讨了可能的吸附机理。研究结果表明，固载离子液体材料保持了离子液体优良的吸附性能，可有效富集和去除纳克级的有害重金属(0.00097 mg L-1 Hg(II)、0.0050 mg L-1 Pb(II)、0.0011 mg L-1 Cd(II)、0.028 mg L-1 Cr(VI))和有机污染物, 对酚类污染物的最大吸附量可达到1269.8mg g-1，吸附效果明显优于市售离子交换树脂和活性炭；溶液温度和pH值的改变，可有效地调控材料对污染物的特异吸附性能，30余种离子和有机物不干扰目标污染物的去除；材料具有较快的传质速度，吸附平衡时间大多在30 min左右；不同碳链长度的固载离子液体材料对污染物的吸附能力不同，可以通过离子液体侧链长短和官能团种类的调控改变材料的吸附选择性；吸附机理以离子交换、静电、配位为主。此外，以介孔材料固载氨基酸阴离子功能化的离子液体材料对温室气体CO2表现出等摩尔吸收的优良的捕集性能。所合成的固载离子液体材料具有较好的稳定性，不仅极大地减少了离子液体用量，降低了成本，防止离子液体的流失，同时也提高了选择性萃取效率，发挥固体载体的优势，便于分离回收及循环利用，为环境样品中痕量重金属的分离分析、低浓度重金属废水的深度处理、有机污染物的样品处理以及CO2捕集提供了新的技术方法和科学依据。