Water Configuration and Transport in Wet "Unsaturated" Porous Media

CTS-9703574研究湿“非饱和”多孔介质中水的形态和运移这个项目是对湿“非饱和”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。所谓的“不饱和”是指只有一部分可用孔隙空间充满水，其余部分充满空气或第二种流体的情况。这种情况的例子是地下水位以上的土壤和任何其他暴露在水分中但未饱和的多孔固体或颗粒材料。通过将具有非常特殊性质的表面活性剂应用于湿不饱和体系的一部分来建立必要的表面张力梯度。在最佳情况下，80%-90%的水会移动。以前的工作已经为表面活性剂的有效性和影响水运动的机制建立了标准。这导致了第一个直接确定湿的“非饱和”多孔介质中的空气-水界面面积的实验方法。这项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。这项以成果为基础的更新(ABR)提案的具体目标是：(A)完成计算空气-水界面面积的模型，(B)确定作为体系饱和度函数的表面活性剂扩散和水运动的动力学，(C)寻找能够影响油-水两相传输的表面活性剂，以及(D)研究实际系统中的水和溶解溶质传输。该模型是基于模拟退火法首次应用于湿“非饱和”多孔介质中表面积的确定。表面活性剂的扩散动力学将通过放射性示踪剂方法进行跟踪。根据水在标准柱中运动时发生的重心变化，将采用一种新的重力测量技术来跟踪水的运动动力学。将要研究的系统包括玻璃球和沙子、粘土矿物和模型土壤。将比较有无溶解电解质的水的运动，以及有无不溶非水相液体(NAPL)的运动。将试图将表面活性剂扩散和水运动的动力学与毛细管壁附近的水的异常高粘度联系起来。这项研究具有很大的潜在技术影响。在目前使用蒸汽干燥机进行这些操作的行业中，结果可能会导致更高效的干燥/脱水过程。通过廉价、无毒、可生物降解的“化学泵”在土壤中移动水分的能力在环境修复和农业中有着重要的应用。对空气-水界面面积的了解是模拟界面传质过程和了解土壤中氧气传输的基础。表面积模型应适用于非水石油体系，以及水-油和水-空气界面，在潮湿的“非饱和”多孔介质中。

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.