树状反胶束调制的多孔吸附剂及其用于广谱微量水污染物的清除

A finely structured nanomaterial can efficiently capture a pollutant but is too small to be separated, while a macroscopic adsorbent is just opposite, can a material combine their merits? In this project, a multifunctional dendritic reverse micelle is used to mediate the one-pot synthesis of a meticulously structured adsorbent. The dendritic reverse-micelle, hydrophobically derived from hyperbranched polyethylenimine (PEI), can readily undergo self-assembly along the interface of a concentric water-in-oil emulsion, and after polymerization of the monomers in the oil phase, forms a microscopically finely surface-functionalized adsorbent. The topological openness of the dendritic reverse micelle can be controlled (by the degree of hydrophobic derivation), and the electronic environment can also be controlled (by chemical derivation of the functional groups). Such a structure can shield the competitive binding by water and enhance the adsorbent-pollutant molecule complement in electronic environment, improving the adsorbing strength by over 105-fold. It is worth to notice that a variety of dendritic reverse micelles, with different topologies and electronic environments, can be simultaneously used, and each embedded on the surface of the adsorbent just like the transmembrane proteins on a cell, and each dendritic reverse micelles will capture a specified pollutant independently, rendering the elimination of wide spectrum of pollutants in one time possible. Preliminary tests show that typical hydrophilic dyes can be reduced to a level below 10 parts per billion (ppb), while that of hydrophobic and carcinogenic polycyclic aromatic hydrocarbons to below 1 ppb. This is a class of adsorbents readily available and recyclable, and can be used to produce quality water in large scale.

结构化纳米粒子虽能强烈捕获污染物但太小而难以从水中分出，宏观吸附剂则刚好相反，二者的优点能否结合？本课题利用多官能团的树状反胶束作调控剂一釜大规模合成具有精细结构的宏观吸附剂。由亲水聚乙撑亚胺亲油衍生而得到的树状反胶束能在浓乳液的油/水界面组装，并在油相聚合后直接得到表面微观精细官能化的多孔宏观吸附剂。树状反胶束允许人们对其拓扑开放度（亲油取代度）和电子环境（官能团演变）进行预控，因而不仅能屏蔽大量水对互补吸附点的竞争，还能增强与污染物分子间的电子互补，使结合强度提高十万倍以上。特别是各种拓扑形态和电子环境都不同的树状反胶束可同时用作调控剂，最终都镶嵌在多孔材料表面并各自发挥捕捉特定分子的作用，类似于细胞膜上功能各异的各种跨膜蛋白，因此能一次性消除广谱微量水污染物。初步尝试使水中残留亲水染料低于10 ppb，而亲油致癌芳烃低于1 ppb。该类水处理剂易合成、能再生、可规模生产高质量饮用水。

能有效针对水中多种痕量污染物的吸附剂的获取仍是科技挑战。本项目利用对多孔通孔材料的表面设计来制备吸附剂，力求高性能与实用并举。与常见的固相化学修饰法不同，项目将预先设计好的反胶束状树状大分子以自组装法附着在原位生成的多孔基质表面。具体地，烷基化超支化聚乙撑亚胺形成反胶束状树状两亲体，两亲体通过自组装法稳定浓乳液，激发浓乳液固化成为通孔基质，基质的表层则由单层树状两亲体表达，具有精细微观结构。所用的树状两亲体由于其分子量很大，在基质上的物理吸附力能超越共价力，故而十分牢固。相反，线性两亲体对照物不仅粘度大、难溶，对应的吸附效果也较差。如果同时用两种树状体共组装时，吸附剂的表面就有两类功能区，其中一种以补丁存在，能同时针对更多种类的污染物。除了自组装法，以超支化聚乙撑亚胺的水溶液填充微米颗粒物间的缝隙，然后通过去溶剂沉积交联可以更简便地获得功能化通孔吸附剂。上述多孔材料表面残留的大量活泼氨基经氯乙酸进一步处理后，产物对多种重金属离子有优良吸附效果，使后者残留水平降至ppm左右。综合来看，这类吸附剂的合成方法简便，结构精细，能处理水中多种污染物尤其是痕量污染物，能循环利用。值得注意的是这些含金属配体的多孔材料也能作为优良的催化剂载体，降低金属催化剂泄漏与残留。