Influence of pH and Compression on Electrohydrodynamic Effects in Nanoporous Packed Beds
Fluid flow and charge transport in fine structures can be driven both by pressure gradients and by electric fields if electrochemical double layers are present on the surfaces. The interrelated electrohydrodynamic effects may be used to drive liquids without moving parts, for example, in dewatering or in electroosmotic chromatography, or to generate small electric currents. While the electrohydrodynamic transport is well understood for simple geometries, models for porous structures are complex. Furthermore, the interconnected porous structure of a packed bed itself strongly depends on the electrochemical double layers. In this study, the electrohydrodynamic transport in packed beds consisting of boehmite particles with an average diameter of 38 nm is investigated. We describe a new approach to the electrokinetic effects by treating the packed beds as theoretical sets of cylindrical capillaries. The charge transport and the electrically driven fluid flow predicted with this model agree well with experimental results. Furthermore, the hydraulic permeability was found to be a nonlinear function of the porosity, independent of whether the porosity change is caused by changing the compression or the electrochemical double layer.
A. T. Yeung and J. K. Mitchell, “Coupled fluid, electrical and chemical flows in soil,” Geotechnique, vol. 43, no. 1, pp. 121–134, 1993.View at: Google Scholar
S. R. Santiwong, J. Guan, and T. D. Waite, “Effect of ionic strength and pH on hydraulic properties and structure of accumulating solid assemblages during microfiltration of montmorillonite suspensions,” Journal of Colloid and Interface Science, vol. 317, no. 1, pp. 214–227, 2008.View at: Publisher Site | Google Scholar
E. K. Zholkovskij, J. H. Masliyah, V. N. Shilov, and S. Bhattacharjee, “Electrokinetic Phenomena in concentrated disperse systems: general problem formulation and Spherical Cell Approach,” Advances in Colloid and Interface Science, vol. 134-135, pp. 279–321, 2007.View at: Publisher Site | Google Scholar
H. Nirschl, R. Wengeler, and B. Schäfer, “Nanofluidics in filtration and particle processing,” Filtration, vol. 7, no. 1, pp. 67–74, 2007.View at: Google Scholar
F. M. Tiller, C. S. Yeh, and W. F. Leu, “Compressibility of paniculate structures in relation to thickening, filtration, and expression—a review,” Separation Science and Technology, vol. 22, no. 2-3, pp. 1037–1063, 1987.View at: Google Scholar
H. Darcy, Les Fontaines Publiques de la Ville de Dijon, Dalmont, Paris, France, 1856.
P. C. Carman, “Fluid flow through granular beds,” Transactions of the Institution of Chemical Engineers, no. 15, pp. 150–166, 1937.View at: Google Scholar
G. E. Archie, “The electrical resistivity log as an aid in determining some reservoir characteristics,” Journal of Petroleum Technology, vol. 5, pp. 54–62, 1942.View at: Google Scholar
J. Lyklema, Ed., Fundamentals of Interface and Colloid Science II, J. Lyklema, Ed., Academic Press, London, UK, 1995.
R. J. Hunter, Introduction to Modern Colloid Science, Oxford University Press, Oxford, UK, 1993.