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快速的进步，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运输和保留。此外，已知纳米材料的迁移率取决于表面涂层性能和稳定剂（如表面活性剂和有机物）的存在。虽然大多数商业上可用的纳米材料都是用表面涂层生产的，但是关于它们的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中的这些空白，该项目将实验室实验与数学模型相结合，量化和预测表面涂层老化对几种代表性工程纳米材料（铁和锰氧化物）在沙子和自然土壤中的命运和运输的影响。这项研究主要围绕三个任务展开；(1)利用石英晶体微天平（QCM）测定纳米颗粒沉积和释放速率作为表面涂层特性的函数；(2)测量纳米颗粒在土壤柱和含水层细胞中的迁移和附着；(3)建立和验证数学模型，预测表面涂层特性和老化对纳米颗粒在土壤和含水层材料中的迁移和持久性的影响。该研究的新方面包括评估纳米颗粒沉积速率，利用扫描电子显微镜（SEM），磁共振成像（MRI）和光透射（LT）分析可视化纳米颗粒迁移率，以及整合实验和数学模型来评估纳米材料在环境中的命运。智力价值：拟议研究的智力价值在于追求环境无害和可持续纳米技术的三个关键领域；(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、聚集性和迁移性的影响；(c)开发和验证能够预测纳米材料环境命运的数值模拟器，作为表面涂层完整性变化的函数。实验研究与数学建模的独特耦合允许对方法进行仔细评估，这些方法可用于快速估计纳米颗粒在一系列表面和溶液条件下的附着参数，并将最终发展能够预测表面涂层完整性和组成对纳米材料命运和运输的影响的数值模型。我们期望在这项工作中建立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中的命运和运输，并将成为纳米材料生命周期分析的重要组成部分。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粒子的饮用水和废水的过滤技术的理解。更广泛的影响：该项目的一个重要组成部分是将教育倡议纳入研究人员的研究和教学活动，其目标是将获得的知识的影响扩展到期刊出版物和会议报告的传统框架之外。这一目标将通过以下活动实现：(a)将本科生纳入耦合实验和数学建模研究，(b)开发交互式多媒体教学工具，以及(c)招募女性和代表性不足的少数民族学生。教学材料，包括基于模型的教程，由本科生和研究生准备的视频，以及说明性案例研究和建模工具，将被纳入大一和大二的课程，并在网站上发布，以便更广泛的学生可以探索控制原始和老化纳米材料在陆地环境中的命运和运输的过程。

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.