Stevens Nate, Ralston John, Sedev Rossen
Ian Wark Research Institute, University of South Australia, Mawson Lakes, SA 5095, Australia.
J Colloid Interface Sci. 2009 Sep 1;337(1):162-9. doi: 10.1016/j.jcis.2009.04.086. Epub 2009 May 10.
The distribution and movement of fluids in porous media are important in a variety of situations arising naturally and industrially (e.g., water migration in soils, oil recovery, chromatography, filtration and separation processes). Our specific interest is in deriving advancing and receding contact angles from capillary pressure measurements in packed beds of particles partially saturated with liquids. The simplest model of a porous medium treats the porous body as an equivalent uniform capillary giving rise to the same capillary pressure. Pressure measurements were performed successfully with advancing as well as receding liquids. For an advancing liquid front a measurement with a second liquid is needed to calibrate the equivalent capillary radius and obtain the advancing contact angle. For a receding liquid front--an additional determination of the amount of liquid trapped behind in smaller pores is required. The equivalent capillary radius is mainly determined by the porosity of the packed bed and is easily corrected to account for capillary retention. Only then can the receding contact angle be obtained reliably. This new methodology for contact angle measurement was validated with model systems and applied successfully to various real particulate systems.
流体在多孔介质中的分布和流动在自然和工业中出现的各种情况下都很重要（例如，土壤中的水迁移、石油开采、色谱法、过滤和分离过程）。我们特别感兴趣的是从部分被液体饱和的颗粒填充床中的毛细管压力测量中得出前进接触角和后退接触角。多孔介质的最简单模型将多孔体视为等效的均匀毛细管，从而产生相同的毛细管压力。使用前进液和后退液都成功进行了压力测量。对于前进液前沿，需要用第二种液体进行测量以校准等效毛细管半径并获得前进接触角。对于后退液前沿，需要额外确定被困在较小孔隙中的液体量。等效毛细管半径主要由填充床的孔隙率决定，并且很容易校正以考虑毛细管滞留。只有这样才能可靠地获得后退接触角。这种测量接触角的新方法已在模型系统中得到验证，并成功应用于各种实际颗粒系统。
