Department of Geology and Geophysics, University of Utah, Salt Lake City, Utah 84112, USA.
Langmuir. 2011 Dec 20;27(24):14982-94. doi: 10.1021/la203587j. Epub 2011 Nov 22.
Many mechanisms of colloid retention in porous media under unfavorable conditions have been identified from experiments or theory, such as attachment at surface heterogeneities, wedging at grain to grain contacts, retention via secondary energy minimum association in zones of low flow drag, and straining in pore throats too small to pass. However, no previously published model is capable of representing all of these mechanisms of colloid retention. In this work, we demonstrate that incorporation of surface heterogeneity into our hemispheres-in-cell model yields all experimentally observed non-straining retention mechanisms in porous media under unfavorable conditions. We also demonstrate that the predominance of any given retention mechanism depends on the coupled colloid-collector-flow interactions that are governed by parameters such as the size and spatial frequency of heterogeneous attractive domains, colloid size, and solution ionic strength. The force/torque balance-simulated retention is shown to decrease gradually with decreasing solution ionic strength, in agreement with experimental observations. This gradual decrease stands in sharp contrast to predictions from mean field theory that does not account for discrete surface heterogeneity.
已经从实验或理论中确定了许多在不利条件下胶体在多孔介质中保留的机制，例如在表面不均匀处附着、在颗粒与颗粒接触处楔入、在低流动阻力区的二次能量最小关联处保留以及在太小而无法通过的孔隙喉道中受到限制。然而，以前没有发表的模型能够代表胶体保留的所有这些机制。在这项工作中，我们证明将表面不均匀性纳入我们的半球细胞模型可以产生在不利条件下多孔介质中所有实验观察到的非限制保留机制。我们还证明，任何给定保留机制的优势取决于胶体-收集器-流动相互作用的耦合，这些相互作用受参数的控制，如有吸引力的异质域的大小和空间频率、胶体大小和溶液离子强度。模拟的力/扭矩平衡保留与实验观察一致，随着溶液离子强度的降低而逐渐降低。这种逐渐降低与不考虑离散表面不均匀性的平均场理论的预测形成鲜明对比。
