Vesicular Biomimetic Membranes for Metal Recovery

本文研究了一种基于囊泡膜的仿生系统，用于去除水中的有害金属阳离子。在初步工作中，PI使用平衡洗涤剂透析法制备单层囊泡，由大豆磷脂酰胆碱制成，囊泡膜中含有亲脂性金属载体离子载体A23187，囊泡内部含有螯合剂（NTA, nitrilotiacetate）。当囊泡分散体与含有金属阳离子的水溶液混合时，阳离子与膜中的金属载体结合。该络合物可溶于膜，并通过膜片扩散到膜泡的内表面，在那里金属离子被释放。释放的离子与螯合剂形成络合物，从而使囊泡膜内表面的亲脂离子络合物的浓度保持极小。当这个值很小时，离子和亲脂物的附加络合物的扩散驱动力仍然很大，并且囊泡继续强烈地吸收金属离子。批量实验结果表明，这些囊泡是铜（II）、镉（II）或铅（II）阳离子混合溶液的有效清除剂，具有快速吸收和高负荷的特点。该技术的主要问题是亲脂载体和磷脂酰胆碱的高成本。本研究将探索成本较低的亲脂性载体，如裂缝型金属结合剂和冠醚基结合剂，以及成本较低的囊泡成分，如烷基苯磺酸盐表面活性剂。还将研究竞争性金属离子吸收，并将测试一个实验规模的连续金属回收系统，该系统使用中空纤维膜筒以逆流模式接触囊泡分散体和废物流。

This proposal studies a vesicular membrane based biomimetic system for removing hazardous metals cation from aqueous streams. In preliminary work, the PI has used equilibrium detergent dialysis to fabricate unilamellar vesicles made of soybean phosphatidylcholine harboring a lipophilic metal carrier, the ionophone A23187, in the vesicle membrane, and a chelating agent (NTA, nitrilotiacetate) in the vesicle interior. When the vesicle dispersion is mixed with an aqueous solution containing the metal cations, the cations become bound to the metal carrier in the membrane. The complex is soluble in the membrane, and it diffuses across the lamella to the inside surface of the membrane vesicle where the metal ion is released. The released ion complexes with the chelator, thereby keeping the concentration of the ion- lipophile complex at the inside surface of the vesicle membrane extremely small. With this value small, the driving force for diffusion of additional complexes of the ion and the lipophile remains large, and the vesicle continues to strongly uptake the metal ions. Results of batch experiments in which the vesicles were mixed solutions containing only Cu(II), Cd(II), or Pb(II) cations demonstrate that the vesicles are effective scavengers of these metal ions with rapid uptake and high loading. The primary problem with this technique is the high cost of the lipophilic carrier and the phosphidylcholine. The proposed research will explore less costly lipophilic carriers such as cleft type metal binding agents and crown ether-based agents, and less costly components for the vesicles such as alkyl benzene sulfonate surfactants. Competitive metal ion uptake will also be studied, and a bench scale continuous metal recovery system will be tested which uses hollow fiber membrane cartridges to contact the vesicle dispersion and the waste stream in a countercurrent mode.