Ternary Porosity Effects on Organic Attenuation by Clays in Clay/Organic/Electrolyte Ternary Systems Studied by Clay- Modified Electrodes and Low Angle X-ray Diffraction

分析和表面化学计划的这个项目的主要重点是利用粘土修饰电极的电化学性质来研究应该模拟有机污染物在粘土床中移动的物种的传输。多扫描循环伏安法将建立多孔介质中离子交换(吸附)和分配反应的动力学模型。这些将是快速的准显式有限差分模型，并将在粘土修饰的电极上进行实验测试，各种化合物应属于不同的动力学区域。该模型将被用来预测电解质形态对最大限度地保留通过粘土床层扩散的有机化合物的影响。孔隙率在控制反应中的作用将由一个电活性探头现场监测，其电流将纯粹由扩散控制，而扩散又由介质的孔隙率控制。建立了一个模型，将取向良好的薄膜的孔隙率与层间距联系起来。这些结果有望帮助人们更好地理解在粘土中发生的几个重要过程，这些粘土被用来衬砌化学废物处置地点。其中包括粘土对化学物质的吸附和吸收，以及粘土在吸收溶剂和电解质时的收缩和膨胀。该项目也有可能导致开发一种用于测量粘土孔隙度的快速电化学方法。

The main focus of this project in the Analytical and Surface Chemistry Program is the utilization of the electrochemical properties of clay modified electrodes to study the transport of species that should mimic the movement of organic pollutants through a clay bed. Models for the kinetic process of ion exchange (adsorption) followed by partitioning reactions in a porous medium will be developed for multisweep cyclic voltammetry. These will be fast quasi-explicit finite difference models, and will be tested experimentally at a clay-modified electrode with a variety of compounds which should fall into different kinetic regions. The model will be used to predict the effect of electrolyte speciation in maximizing retention of an organic compound diffusing through a clay bed. The role of porosity in controlling the reaction will be monitored in situ by an electroactive probe whose current will be controlled purely by diffusion, which is, in turn, controlled by the porosity of the medium. A model has been developed which relates the porosity of a well-oriented film to the interlayer spacing. The results are expected to provide an improved understanding of several important processes which occur in the clays which are used to line chemical waste disposal sites. Among these are the adsorption and absorption of chemicals by clays and the shrinking and swelling of clays as solvents and electrolytes are absorbed. It is also possible that the project will lead to the development of a rapid electrochemical method for measuring the porosity of clays.