Impacts of Surface Coating Aging on Nanomaterial Fate and Transport in Porous Media

尽管在过去的十年中，纳米技术取得了迅速的进步，但我们目前对纳米材料在环境中的命运和运输的理解仍然有限。 最近的研究表明，需要新的方法来准确预测纳米材料在土壤和含水层中的迁移和保留。 此外，已知纳米材料的流动性取决于表面涂层性质和稳定剂（例如表面活性剂和有机物质）的存在。 虽然大多数商业上可获得的纳米材料都是用表面涂层生产的，但关于其寿命和随着时间的推移对纳米材料命运的影响的信息很少。 为了解决我们目前对纳米材料理解的这些差距，该项目将实验室实验与数学建模相结合，以量化和预测表面涂层老化对沙子和天然土壤中几种代表性工程纳米材料（铁和锰氧化物）的命运和运输的影响。 本研究围绕三个任务展开;（1）使用石英晶体微天平（QCM）确定作为表面涂层性质的函数的纳米颗粒沉积和释放速率，（2）测量土壤柱和含水层单元中的纳米颗粒运输和附着，以及（3）开发和验证数学模型，以预测表面涂层特性和老化对纳米粒子流动性和持久性的影响在土壤和含水层物质中。 研究的新方面包括纳米颗粒沉积速率的评估，利用扫描电子显微镜（SEM），磁共振成像（MRI）和光透射（LT）分析来可视化纳米颗粒的流动性，以及实验和数学建模的整合来评估纳米材料在环境中的命运。 智力优势：拟议研究的知识价值在于三个对追求无害环境和可持续的纳米技术至关重要的领域;（1）开发将纳米颗粒沉积测量转化为可用于预测传输行为的附着速率参数的方法，（B）测量表面涂层老化对纳米颗粒稳定性、聚集和迁移率的影响，以及（c）开发和验证能够预测纳米材料作为表面涂层完整性变化函数的环境归宿的数值模拟器。 独特的耦合实验研究与数学建模允许仔细评估的方法，可用于快速估计纳米颗粒附着参数的表面和溶液条件的范围内，并最终在数值模型的发展，能够预测的影响表面涂层的完整性和组成的纳米材料的命运和运输。 我们预计，在这项工作中开发的实验参数和数学模型可以用来预测其他纳米材料在地下系统的命运和运输，并将作为一个重要组成部分的纳米材料的生命周期分析。 此外，在这些研究中获得的知识将提高我们对用于处理含有纳米颗粒的饮用水和废水沃茨的过滤技术的理解。 更广泛的影响：该项目的一个重要组成部分是将教育举措纳入调查人员的研究和教学活动，目的是扩大所获知识的影响，使其超出期刊出版物和会议演讲的传统框架。 这一目标将通过以下活动实现：（a）让大学生参与实验和数学建模相结合的研究;（B）开发互动式多媒体教学工具;（c）招收女生和人数不足的少数民族学生。 这些教学材料包括基于模型的教程、本科生和研究生制作的视频以及说明性案例研究和建模工具，将被纳入新生和大学一级的课程，并在网站上发布，以便更广泛的学生能够探索控制原始和老化纳米材料在陆地环境中的归宿和迁移的过程。

1236653PennellDespite rapid advances in nanotechnologies over the past decade, our current understanding of nanomaterial fate and transport in the environment remains limited. Recent studies have demonstrated that new approaches are needed to accurately predict the transport and retention of nanomaterials in soils and aquifers. In addition, nanomaterial mobility is known to depend upon surface coating properties and the presence of stabilizing agents, such as surfactants and organic matter. Although most commercially-available nanomaterials are produced with surface coatings, very little information is available regarding their longevity and impact on nanomaterial fate over time. To address these gaps in our current understanding of nanomaterials, the project combines laboratory experiments with mathematical modeling to quantify and predict the effects of surface coating aging on the fate and transport of several representative engineered nanomaterials (iron and manganese oxides) in sands and natural soils. The research is structured around three tasks; (1) determination of nanoparticle deposition and release rates as a function of surface coating properties using a quartz crystal microbalance (QCM), (2) measurement of nanoparticle transport and attachment in soil columns and aquifer cells, and (3) development and validation of mathematical models to predict the effects of surface coating properties and aging on nanoparticle mobility and persistence in soils and aquifer materials. Novel aspects of the research include the assessment of nanoparticle deposition rates, utilization of scanning electron microscopy (SEM), magnetic resonance imaging (MRI) and light transmission (LT) analysis to visualize nanoparticle mobility, and the integration of experimental and mathematical modeling to assess nanomaterial fate in the environment. Intellectual Merit: The intellectual merit of the proposed research lies in three areas critical to the pursuit of environmentally sound and sustainable nanotechnologies; (1) development of methods to convert nanoparticle deposition measurements into attachment rate parameters that can be used to predict transport behavior, (b) measurement of the effects of surface coating aging on nanoparticle stability, aggregation, and mobility, and (c) development and validation of numerical simulators capable of predicting the environmental fate of nanomaterials as a function of changes in surface coating integrity. The unique coupling of experimental studies with mathematical modeling allows for careful evaluation of methods that can be used to rapidly estimate nanoparticle attachment parameters for a range of surface and solution conditions, and will culminate in the development of numerical models that are able to predict the effects of surface coating integrity and composition on nanomaterial fate and transport. We anticipate that the experimental parameters and mathematical models developed in this work can be utilized to predict the fate and transport of other nanomaterials in subsurface systems, and will serve as an important component for nanomaterial life cycle analysis. In addition, the knowledge gained in these studies will improve our understanding of filtration technologies used to treat drinking and waste waters containing nanoparticles. Broader Impacts: An important component of the project is the incorporation of education initiatives into the research and instructional activities of the investigators, with the goal of extending the impact of acquired knowledge beyond the traditional framework of journal publications and conference presentations. This goal will be achieved through the following activities: (a) inclusion of undergraduate students in coupled experimental and mathematical modeling research, (b) development of interactive, multi-media instructional tools, and (c) recruitment of female and under-represented minority students. The instructional materials, consisting of model-based tutorials, videos prepared by undergraduate and graduate students, and illustrative case studies and modeling tools, will be incorporated into freshmen and sophomore-level courses and released on a web site so that a broader audience of students can explore processes that govern the fate and transport of pristine and aged nanomaterials in terrestrial environments.