Surfactant and water migration in unsaturated sand

Abstract

In unsaturated coarse disperse materials such as sand, the water on the surface is continous and ‘deep’ enough to be an adequate medium for the migration of surface active substances (SAS). The influence of the tangential force on water migration in unsaturated coarse disperse material is studied by compensating the capillary pressure difference caused by the surface tension gradient. The influence on water migration in unsaturated disperse materials exerted by the additional pressure difference, originating from SAS migration, is comparable to that exerted by capillary pressure difference.

Capillary pressure driven water movement in wet unsaturated porous media: effect of particle electric charge

“…Prior studies in our laboratories, [1][2] in agreement with those accomplished by Karkare et al 3 have shown that application of insoluble surfactants to part of a wet unsaturated porous medium leads to water movement from the surfactant-containing to the surfactant-free part of the system. Different surfactants were analyzed on wet unsaturated porous medium (mainly of sand columns).…”

“…Notwithstanding, further studies performed by Henry et al 4 found that the resultant moisture content distribution in the column was different when the low-solubility alcohol as butanol was used. In the literature, sand was almost always used to simulate the wet unsaturated porous medium, 1,[5][6][7][8][9][10] and similar results indicate that the surfactant causes differences in capillary pressure within the system and water moves to re-establish equilibrium. [7][8] The amount of water that moves depends 7 on all the factors that influence capillary pressure -particle wettability, size, size distribution, packing, etc., as well as the character of the surfactant monolayer that establishes the capillary pressure gradient within the system.…”

Numerical demonstration of surfactant concentration-dependent capillarity and viscosity effects on infiltration from a constant flux line source

“…The pressure differences, when considered across the distance of an infiltration surfactant solute front, can result in large capillary pressure gradients and correspondingly high fluxes between the surfactant-contaminated and surfactant-free regions (Henry and Smith, 2003). Experimental evidence of flow perturbations caused by surfactant-induced capillary pressure gradients in waterwettable unsaturated porous media has been seen in onedimensional (e.g., Tschapek and Boggio, 1981;Tschapek et al, 1984;Smith and Gillham, 1999;Henry et al, 1999) and twodimensional laboratory systems . Though examined surfactant infiltration from a source at the soil surface, their laboratoryscale experiments and subsequent modeling focused on capillary fringe and shallow water table effects but did not examine surfactant effects on infiltration into a low moisture content medium with a thick vadose zone (deep water table) as is examined in the present work.…”

Potential Changes in Chemical Soil Quality Resulting from Graywater Recycling for Landscape Irrigation

“…It has been reported that percolation and infiltration rate of the soil may be altered in the presence of surfactants (Kuhnt, 1993). In addition, permeability and capillarity dispersion of water can be altered by surfactants (Tschapek and Boggio, 1981). Surfactants can also affect soil chemistry by altering the redox potentials, increasing/decreasing the pH, and changing the sorption characteristics of the soil (Kuhnt, 1993).…”