Water Configuration and Transport in Wet "Unsaturated" Porous Media

“非饱和”湿多孔介质中水的形态和运移本项目是对“非饱和”湿多孔介质中水的位置、表面积和由表面张力梯度引起的运动的研究。“不饱和”是指只有部分可用孔隙空间被水填充，其余部分被空气或第二种流体填充的状态。这种情况的例子是地下水位以上的土壤和任何其他多孔固体或颗粒材料，它们暴露于但未被水分饱和。必要的表面张力梯度是通过将具有非常特殊性质的表面活性剂应用于部分湿不饱和体系而建立的。在最佳情况下，80-90%的水会流动。以前的工作已经建立了表面活性剂有效性的标准和影响水运动的机制。它导致了确定湿“非饱和”多孔介质中空气-水界面面积的第一个直接实验方法。本研究的目标是更好地理解这些系统，并将这种理解应用于解决涉及它们的重要技术问题。这项基于成果的更新（ABR）提案的具体目标是：(a)完成一个计算空气-水界面面积的模型的开发，(b)确定表面活性剂扩散和水运动的动力学，作为系统饱和度的函数，(c)寻找能够影响两相油水输送的表面活性剂，(d)研究实际系统中的水和溶解溶质输送。该模型是基于首次应用模拟退火来确定湿“非饱和”多孔介质的表面积。表面活性剂的扩散动力学将用放射性示踪剂方法跟踪。随着水的运动动力学的发展，一种新的基于水在标准柱内运动时发生的重心变化的重力测量技术将紧随其后。要研究的系统包括玻璃球和沙子，粘土矿物和模型土壤。将比较有和没有溶解电解质的水的运动，以及存在和不存在不溶性非水相液体（NAPL）的水的运动。将尝试将表面活性剂扩散和水运动的动力学与毛细壁附近的水异常高粘度联系起来。这项研究具有巨大的潜在技术影响。结果可能导致在工业中更有效的干燥/脱水过程，这些操作现在使用蒸汽干燥机进行。通过廉价、无毒和可生物降解的“化学泵”转移土壤水分的能力在环境修复和农业中有着重要的应用。空气-水界面面积的知识是模拟界面传质过程的基础，也是理解土壤中氧传输的基础。表面积模型应适用于非水石油体系，适用于湿“非饱和”多孔介质中的水-油和水-空气界面。

Abstract CTS -9703574 Water Configuration and Transport in Wet "Unsaturated" Porous Media This project is an investigation of the location, surface area, and movement caused by surface tension gradients, of water held in wet "unsaturated" porous media. By "unsaturated" is meant a condition where only part of the available pore space is filled with water, the remainder being filled with air or a second fluid. Examples of the condition are soil above the water table and any other porous solid or particulate material which has been exposed to but is not saturated with moisture. The necessary surface tension gradients are established by applying surfactants with very specific properties to part of a wet unsaturated system. In optimum cases, 80-90% of the water moves. Previous work has established criteria for surfactant effectiveness and the mechanism through which water movement is effected. It has led to the first direct experimental means of determining the area of the air-water interface in wet "unsaturated" porous media. The goals of this research are to better understand these systems and to apply this understanding to solution of important technological problems which involve them. Specific objectives of this accomplishment-based renewal (ABR) proposal are to: (a) complete development of a model to calculate the air-water interfacial area, (b) determine the kinetics of surfactant spreading and water movement as a function of system saturation, (c) scout for surfactants capable of effecting two phase oil-water transport and (d) investigate water and dissolved solute transport in practical systems. The model is based on the first application of simulated annealing to determination of surface areas in wet "unsaturated" porous media. The kinetics of surfactant spreading will be followed by radiotracer methods. The kinetics of water movement will be followed by a new gravimetric technique based on the changes in the center of gravity which occur when water moves withi n a standard column. Systems to be studied include glass spheres and sand, clay minerals and model soils. Comparison will be made of the movement of water with and without dissolved electrolytes, and in the presence and absence of an insoluble nonaqueous phase liquid (NAPL). Attempts will be made to relate the kinetics of surfactant spreading and water movement to the abnormally high viscosity which has been reported for water near capillary walls. This study has great potential technological impact. Results may lead to more efficient drying/de-watering processes in industries where these operations are now conducted with a steam dryer. The ability to move water in soils by means of a cheap nontoxic and biodegradable "chemical pump" has important applications in environmental remediation and in agriculture. Knowledge of the area of the air-water interface is fundamental to modeling interfacial mass transfer processes, and for understanding oxygen transport in soils. The surface area model should be applicable to non-aqueous petroleum systems, and to water-oil as well as to the water-air interface, in wet "unsaturated" porous media.