Collaborative Research: Near-Surface Repulsion and Mixing- Limitations: Upscaling of Colloid Retention, Breakthrough, and Elution in Non-Uniform Media under Unfavorable Conditions

在环境条件(所谓的不利条件)下，胶体-表面相互作用对胶体运移的深刻影响，使得在这些条件下胶体在多孔介质中的运移的定量预测到目前为止还无法实现。一个主要的问题是，表面是否通常可以用包括有吸引力的异质结构域的整体排斥表面来解释/分类？给定大小和空间频率(地表覆盖率)。具体地说，目前尚不清楚以这种方式表征表面是否可以预测在不利条件下胶体在多孔介质中的传输。这个离散的非均质模型预测(和实验表明)，由于弱吸引作用，在多孔介质颗粒周围的流体中的一小部分胶体将在近地表流体中停留很长时间，这提出了另一个基本问题：在不利条件下胶体在近地表流体中的长停留时间如何影响达西尺度下的输运行为？需要什么放大战略来认识到长时间近地表停留时间的影响？我们假设，这些长的近地表停留时间导致胶体在流体区域内的不完全混合，从而需要记忆功能/多速率或相关的随机游走方法来扩大规模。我们最近开发的具有异质结构域的力学模型捕捉到了在不利条件下胶体在孔隙尺度上的传输和保留行为。该模型将作为在不利条件下将预报扩大到达西等级的平台。模型结果将与撞击射流和多孔介质中胶体传输的实验结果进行比较，以确定胶体尺寸、溶液离子强度和流体速度的范围。我们预计会产生一个机制模型，可以预测在不利条件下胶体滞留的程度和模式。该项目将在胶体传输的数值模型中表示不利的表面，以便为胶体在多孔介质中传输过程中的胶体保留提供力学预测。这个力学模型的结果将被用来探索胶体-表面相互作用对从孔隙到达西尺度的高级传输预测策略的影响。这个项目将极大地提高我们预测环境条件下胶体运输的能力，例如环境中病原体的运输，以及具有新代谢特性的细菌的靶向输送。

The profound influence of repulsive colloid-surface interactions on colloid transport under environmental conditions (so-called unfavorable conditions) has rendered quantitative prediction of colloid transport in porous media under these conditions unattainable to date. A major question is whether surfaces can generally be interpreted/categorized in terms of a bulk repulsive surface that includes attractive ?heterodomains? of given size and spatial frequency (surface coverage). Specifically, it is unknown whether characterizing surfaces in this way allows prediction of colloid transport in porous media under unfavorable conditions. This discrete heterogeneity model predicts (and experiments indicate) that a fraction of colloids in the fluid surrounding a porous media grain will spend long residence times in the near-surface fluid due to weak attractive interactions, which raises another fundamental question: how do the long residence times of colloids in the near-surface fluid under unfavorable conditions influence transport behavior at the Darcy scale? What scale-up strategies are needed to recognize the influence of long near-surface residence times? We posit that these long near-surface residence times yield incomplete mixing of colloids across the fluid domain, necessitating memory function/multirate or correlated random walk approaches to upscaling. Our recently-developed mechanistic model with heterodomains captures colloid transport and retention behavior at the pore scale under unfavorable conditions. This model will serve as the platform from which to scale up predictions to the Darcy scale under unfavorable conditions. The model results will be compared to experimental results for colloid transport in an impinging jet and in porous media for a range of colloid sizes, solution ionic strengths, and fluid velocities. We anticipate producing a mechanistic model that will predict the extent and mode of colloid retention under unfavorable conditions. This project will represent unfavorable surfaces in numerical models of colloid transport in order to provide mechanistic prediction of colloid retention during transport in porous media. The results of this mechanistic model will be used to explore the influence of colloid-surface interaction on strategies to upscale transport prediction from the pore to the Darcy scale. This project will greatly enhance our ability to predict colloid transport under environmental conditions, in contexts such as pathogen transport in the environment, and targeted delivery of bacteria with novel metabolic properties.