Selective and Regenerable Metal Sorbing Vesicles for Metal Ion Recovery

这项研究的中心目标是论证新型金属吸附泡囊介质在连续过程中从稀水溶液中选择性回收有毒重金属离子如Cu2+、Cd2+和Pb2+的可行性。金属吸附囊泡是一种亚微米直径的表面活性双层膜胶囊，利用囊壁中的亲脂性金属载体和溶解于水中的囊泡内部的水溶性螯合剂，已被设计用于清除和浓缩金属离子。载体促进带电金属离子通过否则不渗透的脂类双层的传输，而包裹的螯合剂提供金属离子吸收的驱动力。批量结果表明，每升悬浮液的表面积为103-104m2的工程金属吸附微囊悬浮液，可以在几分钟或更短的时间内选择性地将Pb2+或Cu2+浓度从1-5ppm降至低ppb水平，同时将金属浓缩3个数量级。这些结果被用来设计一种小试规模的连续金属离子提取过程，其中囊泡和进料流使用中空纤维超滤筒接触。铅离子在该连续体系中选择性分离，可用一个简单的数学模型来描述。然而，这种连续体系不包括用于金属离子释放的囊泡再生阶段，从而使囊泡可以重复使用。在拟议的三年项目中，这项分离技术将在三个关键领域提出，这三个领域对建立技术可行性至关重要：选择性设计、具有囊泡再生的连续处理和增强囊泡稳定性。吸附金属的囊泡的总体选择性以非相加的方式取决于载体和螯合剂对溶液中存在的离子的相对亲和力。对这种全新的分离机理提出的定性模型表明，如果它们的选择性曲线匹配得当，整个系统的选择性可以比载体或螯合剂单独的选择性高出一个数量级。含有精心选择的载体和螯合剂对的囊泡的选择性将被测定，以证实金属吸附囊泡选择性的定性模型。至于囊泡的可重用性，初步数据表明，在略高的温度和适度的pH为2.0的条件下，载金属的囊泡可以在几分钟内再生。金属吸附囊泡再生过程将被进一步研究、优化，并集成到小试规模的连续金属离子回收系统中。将建立系统的描述性数学模型，用于工艺设计，并通过与实验结果的比较进行测试。最后，将测试不同化学成分的聚合囊泡在洗涤剂、醇和钙离子水平升高时的稳定性，例如，在实际工艺流程中可能会遇到的情况。与这项研究相结合的是对聚合泡囊的渗透性和可再生性的评估，因为这些属性对拟议的连续金属回收系统的效果有直接影响。目前，在文献中还没有关于载体介导的跨聚合囊泡双层的转运的数据。

CTS-9525019 Monbouquette UCLA The central goal of this research is to demonstrate the feasibility of novel metal-sorbing vesicle media for the selective recovery of toxic heavy metal ions, such as Cu2+, Cd2+ and Pb2+, from dilute aqueous solution in a continuous process. Metal-sorbing vesicles, which are submicron-diameter, surfactant bilayer membrane capsules, have been engineering to scavenge and to concentrate metal ions by virtue of a lipophilic metal carrier in the vesicle wall and a water-soluble, meal-chelating agent dissolved in the aqueous vesiclle interior. The carrier facilitates transport of the charged metal ion across the otherwise impermeable lipiid bilayer while the encapsulated chelating agent provides the driving force for metal ion uptake. Batch results show that suspensions of engineered metal-sorbing vesicles, which present 103-104m2 of surface area per liter of suspension, can selectively reduce Pb2+ or Cu2+ concentrations from 1-5 ppm to low ppb levels in minutes or less while concentrating the metal by 3 orders of magnitude. These results were used to design a bench-scale continuous metal-ion extractin process where the vesicles and the feed stream were contacted using a hollow-fiber ultrafiltration cartridge. Lead ions were selectivly separated in this continous systems, which was described well by a simple mathematical model. However, this continuous system did not include a vesicle regeneration stage for metal ion release such that the vesicles could be reused repeatedly. During the proposed three-year project, this separations technology will be brought forward in three areas critical to the establishment of technical feasibility: design for selectivity, continous processing with vesicle regeneration, and vesicle stability enhancement. The overall selectively of the metal-sorbing vesicle depends in a non-additive way on the relative affinity of both carrier and chelator for the ions present in solution. A proposed qualitative model of this fundamentally new mechanisms in separations shows that the overall systems can be orders of magnitude more selective than the carrier or chelator alone if their selectivity profiles are properly matched. The selectivity of vesicles harboring carefully chosen carrier and chelator pairs will be determined to confirm the qualititative model of metal-sorbing vesicle selectivity. As for vesicle reusability, preliminary data indicates that metal-laden vesicles can be regenerated in minutes at slightly elevated temperature and a moderate pH of 2.0. A metal-sorbing vesicle regeneration process will be further investigated, optimized and integrated into a bench-scale continuous metal-ion recovery system. A descriptive mathematical model of the system, useful for process design, will be constructed and tested by comparison to experimental results. Finally, polymerized vesicles of various chemistry will be tested for improved stability at the elevated levels of detergent, alcohols, and Ca2+ ions, for example, that could be encountered in an actual process stream. Coupled to this study will be an assessment of the permeability and regenerability properties of the polymerized vesicles, as these properties have a direct impact on the efficacy of the proposed continuous metal recovery systems. Currently there is no data available in the literature on carrier mediated transport across polymerized vesicle bilayers.