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

平衡物理化学的原理是众所周知的，当模拟环境和传输过程中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边界处的界面。界面输运过程对于处理和研究广泛的工业或环境系统中的胶体是重要的，但它们不被理解，甚至可能不被理解为不平衡的系统，例如当存在引入pH和表面电荷效应的化学梯度时。 在本项目中，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传输的重要特征的配置。该项目将研究pH调节的表面电荷、微米和纳米尺度系统中的流动、材料类型和运输模式（例如，积累或分散），产生一个连贯的框架，将物理化学与运输联系起来，从纳米到宏观尺度。该项目的更广泛的影响包括培训研究生和本科生，用流体动力学、物理化学和传输现象的实验和模拟工具研究这些及时的问题，以便对这些问题进行定量理解。推广工作包括描述PI与未来研究科学家接触、教学和指导的方法，包括继续自2002年以来提供的年度“假日”讲座。该项目的目标是耦合的物理化学过程的知识和附近的固液界面，以了解和控制，颗粒传输和流体流动在无数的小规模和多孔材料。重点是由pH值引起的表面电荷的变化，这是耦合到宏观梯度的化学浓度，产生泳动和渗透流驱动的非平衡现象。这些想法将使用基于电动力学原理的实验，模拟和理论来解决，包括最近对修改后的泊松-玻尔兹曼描述的扩展，该描述解释了对传输现象重要的分子水平特征。本研究主要有以下三个方面的内容：（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的表面反应和扩散电泳颗粒运动;（二）研究表面反应和扩散渗透通道流动，通过使用微流体方法来控制通道壁表面电荷的空间异质性，从而了解如何诱导流动影响颗粒传输作为pH值，离子强度和颗粒类型的函数;和（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，几何形状等）可能导致颗粒积聚或分散，这一点迄今为止还不清楚，也不清楚其特征。该研究主题将促进对表面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NSF的法定使命，并被认为值得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来支持。

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.