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Swelling Pressures, Electric Potentials, and Ion Concentrations: Their Role in Hydraulic and Osmotic Flow Through Clays
Author(s) -
Kemper W. D.,
Shainberg I.,
Quirk J. P.
Publication year - 1972
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1972.03615995003600020012x
Subject(s) - porous medium , pressure gradient , osmotic pressure , osmosis , diffusion , compressibility , outflow , chemistry , hydraulic conductivity , mechanics , concentration gradient , porosity , materials science , thermodynamics , membrane , chromatography , geology , soil science , soil water , physics , organic chemistry , biochemistry , oceanography
Using mass balance and force balance equations, the mechanisms of convective transport through porous media are outlined. Pressure differences across compressible porous media cause clay to concentrate at the outflow side until the resulting osmotic pressure gradient balances the hydraulic pressure gradient. The resulting gradient in mobile adsorbed cations causes a diffusion potential which moves solution by electro‐osmosis to the outflow side. When midplane potentials in the pores are appreciable, solution concentration differences across incompressible media are translated into a hydraulic pressure gradient along the midplane of the pores which moves the solution to the high concentration side. Similar concentration differences across compressible porous media result in nonuniform clay distribution, and diffusion potential gradients, which cause electro‐osmotic movement of solution to the high concentration side of the media. These mechanisms provide an explanation for the rapid rates of “osmotic” solution flow observed in response to solute concentration gradients across membranes and other porous media.