Research Initiation Award: Novel Approaches to Probing the Mechanism of Brownian Colloid Release from Packed Bed Surfaces

摘要约瑟夫·瑞安CTS-9410301放射性核素、金属和疏水有机化合物等低溶解性污染物的传输与胶体的传输直接相关。布朗胶体从多孔介质表面的扩散驱动释放受胶体和多孔介质表面的化学、溶液化学(pH、离子强度)、流速以及胶体和颗粒大小的影响。在过去，胶体释放动力学被模拟为附着胶体和分离胶体之间的一级交换，其方式类似于Arrhenius动力学。在某些条件下，由于界面势能计算的特殊性，这种方法失败了。初步的实验结果表明，胶体的释放实际上是一个由表面和溶液化学控制的表面脱离和(2)由流速扩散系数控制的跨边界层扩散的两步机制。这里提出的实验旨在通过尝试分离和量化每一步来证明两步机制。分离步骤将通过在不流动的流体中进行实验来分离。扩散步骤将通过移除能量势垒来隔离。对实验结果进行分析，建立胶体释放的定量动力学模型。该项目解决了地下水中的环境问题。

ABSTRACT Joseph Ryan CTS-9410301 The transport of low-solubility contaminants like radionuclides, metals, and hydrophobic organic compounds is directly linked to the transport of colloids. The diffusion-driven release of Brownian colloids from porous media surfaces is influenced by the chemistry of the colloid and porous media surfaces, the solution chemistry (pH, ionic strength), the flow velocity, and the colloid and grain sizes. In the past, the kinetics of colloid release were modeled as a first-order exchange between attached and detached colloids in a manner analogous to Arrhenius kinetics. Under certain conditions, this approach has failed, owing to peculiarities in the calculation of the intersurface potential energy. Preliminary experimental results have indicated that colloid release is actually a two-step mechanism consisting of (1) detachment from the surface controlled by surface and solution chemistry and (2) diffusion across the boundary layer controlled by the effect of flow velocity diffusion coefficient. The experiments proposed here are designed to proof the two-step mechanism by attempting to isolate and quantify each step. The detachment step will be isolated by conducting experiments in non-moving fluid. The diffusion step will be isolated by removing the energy barrier. The results of the experiments will be analyzed to develop a quantitative kinetic model of colloid release. The project addresses environmental concerns in groundwaters.