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Abstract

Diffusion-osmosis is an important electro kinetic flow mechanism in microchannels and nanochannels. In an electrolyte system, diffusion-osmosis transport results from the electrostatic interaction between a tangential concentration gradient of the electrolyte and a charged wall. The diffusion-osmotic flow of an electrolyte solution along a plane (in porous media) which is induced by the presence of a charged surface induced by the imposed electrolyte concentration gradient has been reviewed and investigated theoretically. It was assumed that there will be a constant concentration gradient imposed along the axial direction at the steady state. Electrostatic and induced potential distribution and velocity distribution of an electrolyte solution near a charged plate wall were determined from using Poisson, linearized Poisson-Boltzmann and modified Navier-Stokes equations, respectively. It was found that the normalized induced electric field approaches unity as we go far away from the EDL and normalized velocity increases with an increase in the electro-kinetic distance and approaches a constant. The effect of the induced electric field in the EDL was found to be of a dominant significance on the diffusion-osmotic flow.