Development of a Copolymer-Based System for Targeted Delivery of Nanoparticulate Iron to Environmental Non-Aqueous Phase Liquids

ABSTTACT -0521721卡耐基梅隆大学智力优异。地下土壤和地下水的有机污染是一个广泛而棘手的环境问题，它将从纳米技术中受益。环境保护署报告说，有机污染物的污染，特别是氯化挥发性有机化合物，是超过一半的超级基金国家优先事项清单网站的主要问题[在超级基金网站发现的常见化学品，美国环保署，2003年]。与这些化合物相关的健康风险导致了过去30年来广泛但相对不成功的补救努力。过去的补救努力取得的有限成功主要是因为大多数有机污染物在水中的溶解度有限，并且倾向于作为单独的非水相液体（NAPL）保留在地下。残留的NAPL池作为污染物浸出到地下水的长期来源，导致大量的溶解污染物和非常长的修复时间。先前的研究表明，悬浮的铁纳米颗粒与NAPLs反应，将其转化为无毒的产品。该提案的主要目标是开发和优化优先将含铁纳米颗粒靶向NAPL-水界面的聚合物组件，因此修复活动可以集中在NAPL源。该研究的重点是成功开发靶向纳米颗粒递送系统所需的界面行为。该聚合物被设计为多功能的-它们将铁纳米颗粒分散到水中以通过多孔介质获得良好的水传输性，最小化对矿物和天然有机物质（NOM）表面的不期望的吸附，并且优先锚纳米颗粒以在NAPL/水界面处积聚。实验指标包括聚合物对胶体稳定性的影响，通过多孔砂柱的运输，对模型矿物和NOM表面的吸附，以及对NAPL/水界面的分配。嵌段共聚物的组成和结构将系统地变化。使用受控自由基聚合方案将提供对嵌段长度的严格控制。最后，将比较两种聚合物附着到纳米颗粒上的模式-可溶性嵌段共聚物的物理吸附和从纳米颗粒表面接枝的嵌段共聚物。使用流行的“泵和处理”技术，通常需要几十年才能达到NAPL清除目标，因为它们主要针对NAPL羽流，而不是源。因此，能源部目前提倡开发新型原位技术来修复其受污染的场地[美国能源部场地地下水响应行动优化指南，美国能源部环境管理局，2002年]。提出的纳米颗粒系统被设想为一种新的原位修复技术的基础，该技术具有通过直接将修复行动瞄准源而不是羽流来加速清理的潜力。学生将通过这项补助金接受研究培训。通过本科生参与研究，特别是通过利用卡内基梅隆大学的少数民族本科生暑期研究所，将产生进一步的教育效益。参与的学生和教师将为卡内基梅隆大学的“工程你的未来”项目准备动手操作的“智能聚合物”和“环境中的纳米技术”模块，该项目旨在提高匹兹堡地区女高中生的技术意识。

ABSTTACT - 0521721Carnegie Mellon UniversityIntellectual Merit. Organic contamination of subsurface soil and groundwater is an extensive and vexing environmental problem that stands to benefit from nanotechnology. The Environmental Protection Agency reports that contamination by organic pollutants, especially chlorinated volatile organic compounds, are primary concerns at over half of the Superfund National Priorities List sites [Common Chemicals Found at Superfund Sites, U.S. E.P.A., 2003]. Health risks associated with these compounds have led to an extensive, but relatively unsuccessful, remediation effort for the past 30 years. The limited success of past remediation efforts is primarily because most organic pollutants have limited solubility in water and tend to remain as a separate non-aqueous phase liquid (NAPL) in the subsurface. Residual NAPL pools act as long-term sources for contaminant leaching to the groundwater, resulting in large plumes of dissolved contaminants and very long remediation times.Prior research indicates that suspended iron nanoparticles react with NAPLs to convert them to non-toxic products. The major goal of this proposal is to develop and optimize polymer assemblies that preferentially target iron-containing nanoparticles to the NAPL-water interface, so the remediation activity can be concentrated at the NAPL source. The research focuses on the interfacial behaviors that are required to successfully develop a targeted nanoparticle delivery system. The polymers are designed to be multifunctional - they disperse the iron nanoparticles into water for good aqueous transportability through porous media, minimize undesirable adsorption to mineral and natural organic matter (NOM) surfaces, and preferentially anchor nanoparticles to accumulate at the NAPL/water interface. Experimental metrics include the polymers' effects on colloidal stability, transport through porous sand columns, adsorption to model mineral and NOM surfaces, and partitioning to the NAPL/water interface. The composition and architecture of the block copolymers will be systematically varied. Use of controlled radical polymerization schemes will provide tight control over block lengths. Finally, two modes of polymer attachment to the nanoparticle will be compared - physisorption of soluble block copolymers and block copolymer grafting from nanoparticle surfaces.Broader Impact. Several decades are typically required to reach NAPL cleanup targets using the prevailing "pump-and-treat" technologies, because they address primarily the NAPL plume, not the source. Accordingly, the Department of Energy currently advocates the development of novel in situ technologies to remediate its contaminated sites [Guidance for Optimizing Ground Water Response Actions at Department of Energy Sites, U.S. D.O.E. Office of Environmental Management, 2002]. The proposed nanoparticle system is envisioned as the basis for a new in situ remediation technology with the potential to accelerate cleanup by directly targeting remediation action to the source, rather than the plume.One Ph.D. student will receive research training through this grant. Further educationalbenefits will accrue through the involvement of undergraduate students in the conduct of the research, especially by leveraging Carnegie Mellon's Summer Institute for MinorityUndergraduate Students. Participating students and faculty will prepare hands-on "smartpolymer" and "nanotechnology in the environment" modules for Carnegie Mellon's Engineering Your Future program that increases technology awareness among female high school students in the Pittsburgh area.