Table of Contents
Physical Separation in Science and Engineering
Volume 2009 (2009), Article ID 817135, 8 pages
http://dx.doi.org/10.1155/2009/817135
Research Article

Influence of pH and Compression on Electrohydrodynamic Effects in Nanoporous Packed Beds

Institut für Mechanische Verfahrenstechnik und Mechanik, Universität Karlsruhe (TH), Straße am Forum 8, 76131 Karlsruhe, Germany

Received 18 August 2008; Revised 9 January 2009; Accepted 28 January 2009

Academic Editor: Eiji Iritani

Copyright © 2009 Bastian Schaefer and Hermann Nirschl. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

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.