University of Colorado Denver, Department of Civil Engineering, Campus Box 113, PO Box 173364, Denver, CO 80217-3364, USA.
J Colloid Interface Sci. 2011 Nov 1;363(1):418-24. doi: 10.1016/j.jcis.2011.06.046. Epub 2011 Jun 26.
Colloidal phenomena play an important role in natural porous media, where they influence soil structuring, contaminant migration, filtration, and clogging. Several methods are available to measure pore space geometry within porous media, but these methods have limited applicability when the relevant physical, chemical, or biological processes are dominated by dynamic colloidal phenomena. Here we report a new technique to quantify colloid aggregate structure as a fractal dimension using static light scattering within index-matched porous media (granular Nafion). We validate the method by obtaining consistent results for scattering in suspensions and in porous media, and verify that multiple scattering at environmentally relevant colloid concentrations does not affect the determination of fractal dimension. We also observe restructuring of aggregates during homogenization in the porous media, indicated by an apparent increase in fractal dimension, which can be explained by an analysis of the fluid shear stress caused by repeated inversions of test tubes either containing or not containing granular media. This technique will permit progress in obtaining fundamental descriptions of colloidal phenomena in porous media.
胶体现象在自然多孔介质中起着重要作用，它们影响土壤结构、污染物迁移、过滤和堵塞。有几种方法可用于测量多孔介质中的孔隙空间几何形状，但当相关的物理、化学或生物过程受动态胶体现象主导时，这些方法的适用性有限。在这里，我们报告了一种新的技术，通过在指数匹配的多孔介质（颗粒状 Nafion）内使用静态光散射来量化胶体聚集体结构作为分形维数。我们通过在悬浮液和多孔介质中的散射获得一致的结果验证了该方法，并验证了在环境相关胶体浓度下的多次散射不会影响分形维数的确定。我们还观察到在多孔介质中均匀化过程中聚集体的重构，这表现为分形维数的明显增加，这可以通过分析由反复倒置含有或不含有颗粒状介质的试管引起的流体剪切应力来解释。这项技术将有助于在获得胶体在多孔介质中现象的基本描述方面取得进展。
