Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan.
Langmuir. 2011 Nov 15;27(22):13481-8. doi: 10.1021/la203240b. Epub 2011 Oct 24.
Electrokinetic treatments such as the electrophoretic technique have been applied successfully to various soil remediation and contaminant removal situations. To understand further the fundamental features involved, the electrophoretic motion of a charged particle in porous media is investigated theoretically in this study, focusing on the boundary effect of a nearby solid plane toward which the particle moves perpendicularly. The porous medium is modeled as a Brinkman fluid with a characteristic screening length (λ(-1)) that can be obtained directly from the experimental data. General electrokinetic equations are used to describe the system and are solved with a pseudospectral method based on Chebyshev polynomials. We found that the particle motion is deterred by the boundary effect in general. The closer the particle is to the boundary, the more severe this effect is. Up to a 90% reduction in particle mobility is observed in some situations. This indicates that a drastic overestimation (10-fold!) of the overall transport rate of particles may occur for large-scale in situ operations in porous media, such as soil remediation utilizing large planar electrodes, should a portable analytical formula valid for bulk systems only be used. Correction factors for various situations in porous media are presented as convenient charts with which to aid engineers and researchers in the field of environmental engineering, for instance, as a realistic estimation of the actual transport rate obtainable. In addition, the results of present study can be applied to biomedical engineering and drug delivery as well because polymer gels and skin barriers both have a porous essence.
电动处理方法，如电泳技术，已成功应用于各种土壤修复和污染物去除情况。为了进一步了解所涉及的基本特征，本研究从理论上研究了带电荷粒子在多孔介质中的电泳运动，重点研究了粒子垂直移动时靠近固体平面的边界效应。多孔介质被建模为具有特征屏蔽长度（(\lambda^{-1})）的 Brinkman 流体，该长度可以直接从实验数据中获得。一般的电动方程用于描述系统，并使用基于切比雪夫多项式的伪谱方法求解。我们发现，粒子的运动通常会受到边界效应的阻碍。粒子越靠近边界，这种效应就越严重。在某些情况下，粒子的迁移率会降低 90%。这表明，如果仅使用适用于整体系统的便携式分析公式，则在大型原位操作（例如利用大型平面电极进行土壤修复）中，对颗粒整体传输速率的严重高估（10 倍！）可能会发生。本研究提出了各种多孔介质情况下的修正因子，以方便工程师和研究人员在环境工程领域使用，例如，作为对实际可获得的实际传输速率的现实估计。此外，本研究的结果还可应用于生物医学工程和药物输送，因为聚合物凝胶和皮肤屏障都具有多孔本质。
