Chemical Reactions and Chemically-driven Transport in Channels and Porous Media

在模拟发生在液体和固体之间、两种液体之间或液体和气体之间的界面上的环境和传输过程时，平衡物理化学原理是众所周知的。界面输运过程对于在广泛的工业或环境系统中处理和研究胶体非常重要，但对于非平衡系统，例如当存在引入pH和表面电荷效应的化学梯度时，界面输运过程不被理解，甚至可能不被重视。在这个项目中，将通过实验、数学建模和数值模拟来研究模拟多孔材料中胶体运输的重要特征。该项目将研究ph调节的表面电荷、微观和纳米尺度系统中的流动、材料类型和传输模式（例如，积累或分散）的综合效应，从纳米尺度到宏观尺度，形成一个将物理化学与传输联系起来的连贯框架。该项目更广泛的影响包括培养研究生和本科生利用流体力学、物理化学和输运现象的实验和模拟工具来研究这些及时的问题，从而对这些问题有定量的认识。外联工作包括描述PI与未来研究科学家接触、教学和指导的方法，包括延续自2002年以来每年举办的“假日”讲座。该项目的目标是将固液界面及其附近的物理化学过程的知识结合起来，以理解和控制无数小尺度和多孔材料中的颗粒传输和流体流动。重点是由ph诱导的表面电荷变化驱动的非平衡现象，这种变化与化学浓度的宏观梯度相耦合，产生渗透和渗透流动。这些想法将通过实验、模拟和基于电动力学原理的理论来解决，包括最近对修正的泊松-玻尔兹曼描述的扩展，该描述解释了对输运现象重要的分子水平特征。本研究有以下三个系统目的：(1)研究在pH和电解质梯度存在下，不同pH、离子强度和颗粒类型下的表面反应和扩散电泳颗粒运动；(2)利用微流体方法研究表面反应和扩散通道流动，以控制通道壁表面电荷的空间异质性，从而了解诱导流动如何以pH、离子强度和颗粒类型为函数影响颗粒输移；(3)多孔材料中悬浮液的流动，其中定性和定量条件（化学，颗粒类型，几何等）可导致颗粒积聚或分散，迄今为止人们对其知之甚少，表征也很差。研究主题将促进对地表主导的运输过程的理解，这些过程发生在广泛的环境和工业问题和过程中。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The principles of equilibrium physical chemistry are well known when modeling environmental and transport processes at interfaces that occur at the boundary between a liquid and a solid, between two liquids, or between a liquid and a gas. Interfacial transport processes are important for handling and studying colloids in a wide range of industrial or environmental systems, but they are not understood and may not even be appreciated for systems that are out of equilibrium, such as when there are chemical gradients that introduce pH and surface charge effects. In this project, configurations that mimic important features common to transport of colloids in porous materials will be studied with experiments, mathematical modeling, and numerical simulations. The project will examine the integrated effects of pH-regulated surface charge, flows in micro- and nano-scale systems, material type, and mode of transport (e.g., accumulation or dispersion), yielding a coherent framework linking physical chemistry to transport, from nano- to macro-scales. The broader impacts of the project include training graduate students and undergraduates to study these timely problems with experimental and simulation tools of fluid dynamics, physical chemistry, and transport phenomena so as to develop quantitative understanding of these problems. The outreach efforts included characterize the PI’s approaches to engaging with, teaching, and mentoring future research scientists, including continuing an annual “holiday” lecture that has been delivered since 2002. The goal of this project is to couple knowledge of physicochemical processes at and near solid-liquid interfaces to understand, and control, particle transport and fluid flow in a myriad of small-scale and porous materials. The focus is on non-equilibrium phenomena driven by pH-induced changes in surface charge, which is coupled to macroscopic gradients in chemical concentrations, to produce phoretic and osmotic flows. These ideas will be tackled using experiments, simulations, and theory based on the principles of electrokinetics, including recent extensions to the modified Poisson-Boltzmann description that accounts for molecular-level features important to transport phenomena. The research has the following three systematic aims: (1) The study of surface reactions and diffusiophoretic particle motions in the presence of pH and electrolyte gradients, for different pH, ionic strength, and particle type; (2) The study of surface reactions and diffusioosmotic channel flows by using microfluidic methods to control the spatial heterogeneity of the surface charge of the channel walls and so understand how the induced flows affect particle transport as a function of pH, ionic strength, and particle type; and (3) the flow of suspensions in porous materials, where qualitative and quantitative conditions (chemical, particle type, geometry, etc.) can lead to particle accumulation or dispersion that until now is poorly understood and poorly characterized. The research themes will advance the understanding of surface-dominated transport processes, which occur in a wide range of environmental and industrial problems and processes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.