Collaborative Research: Retention of Anisotropic Colloids in Porous Media: A Modeling and Experimental Investigation at Multiple Scales

合作研究：多孔介质中各向异性胶体的保持：多尺度下的建模和实验研究摘要地下水是水文循环中最重要的组成部分之一，是约33%的公共供水的来源，并为美国90%以上的农村人口提供饮用水。生物(细菌)和非生物(土壤颗粒)天然胶体普遍存在于地下水中。病原体(生物胶体)的传输与生产安全饮用水有关，而地下水中胶体(非生物胶体)促进的重金属传输已被广泛认为是一个严重的公众关切。几乎所有的天然胶体在性质上都是各向异性的，形状非球形，表面电荷具有不同程度的不均一性。这个项目解决了我们目前对胶体颗粒在多孔介质中的传输和命运的理解的局限性，这些局限性源于以前研究中使用的球形和均匀表面电荷的近似。更好地了解胶体在环境中的传输和保留将提供生产安全饮用水和保护可持续水资源所需的关键知识，这是人类健康和发展的基本步骤。这项工作的结果将纳入本科生和研究生的课程。关于胶体和纳米材料的环境方面的互动演示将在为期两周的夏令营期间吸引初中生和高中生参加，该夏令营鼓励妇女和代表性不足的少数民族对STEM学科感兴趣。该项目是一项综合考虑形状各向异性和表面电荷异质性的实验和建模研究。这项研究使用多尺度方法来研究各向异性胶体在平面上、颗粒对颗粒接触处以及复杂的多孔介质中的保留情况。使用实验室制备的具有不同长宽比和表面电荷不均匀的棒状胶体颗粒的系统实验将以新的方式进行分析。在微电子学、高分辨率质量传感、光学显微镜和激光扫描细胞术中应用尖端方法，将能够观察到含有多孔介质的矿物颗粒表面和孔喉上的胶体附着率，并揭示适合于扩大对含水层的观察的现象。同时，将开发一种能够跟踪各向异性胶体在多孔介质中的运动和取向的数值模拟模型。该项目的结果提供了关于非球形和表面电荷不均匀如何影响各向异性胶体的传输和保留的预测性量化。

Collaborative Research: Retention of Anisotropic Colloids in Porous Media: A Modeling and Experimental Investigation at Multiple ScalesAbstractGroundwater is one of the most important components of the hydrologic cycle, serving as the source of about 33 percent of public water supply and providing drinking water to more than 90 percent of the rural population in the United States. Biological (bacteria) and non-biological (soil particles) natural colloids are ubiquitous in groundwater. The transport of pathogens (biological colloids) is relevant to producing safe drinking water, and the transport of heavy metals as facilitated by colloids (non-biological colloids) in groundwater has been widely recognized as a serious public concern. Almost all natural colloids are anisotropic in nature, being non-spherical in shape and possessing varied degrees of heterogeneity in surface charge. This project addresses the limitations of our current understanding of transport and fate of colloidal particles in porous media that stem from approximations of spherical shape and uniform surface charge used in previous studies. An improved understanding of colloid transport and retention in the environment will provide critical knowledge needed for producing safe drinking water and protecting sustainable water resources, essential steps for human health and development. Results from this work will be incorporated into undergraduate and graduate curriculums. Interactive demonstrations on environmental aspects of colloids and nanomaterials will engage middle- and high-school students during a two-week summer camp that encourages interest in STEM disciplines among women and under-represented minorities.This project is a combined experimental and modeling study that integrates considerations of shape anisotropy and surface-charge heterogeneity. The research uses a multi-scale approach to investigate the retention of anisotropic colloids onto flat surfaces, at grain-to-grain contacts, and in complex porous media. Systematic experiments using laboratory-prepared rod-shaped colloidal particles with various aspect ratios and surface-charge heterogeneity will be analyzed in novel ways. Applications of cutting-edge methodologies in microelectronics, high-resolution mass sensing, optical microscopy, and laser-scanning cytometry will enable observations of colloid attachment rates on the surfaces and pore throats of the mineral grains comprising porous media and reveal phenomena appropriate to scaling up observations to aquifers. In parallel, a numerical simulation model that is capable of tracking both the movement and orientation of anisotropic colloids within porous media will be developed. The results of this project provide predictive quantification on how non-spherical shape and surface-charge heterogeneity impact transport and retention of anisotropic colloids.