Flow in "Unsaturated" Porous Media Due to Water-Insoluble Surfactants: Role of Momentum Transfer from a Spreading Monolayer

Karkare, Milind V.; Fort, Tomlinson

doi:10.1021/la00022a051

Cited by 16 publications

(12 citation statements)

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“… Tschapek and Wasowski [1982] qualitatively showed that spreading of a sparingly soluble surfactant at the air‐water interface in an unsaturated porous medium was “…some thousand times slower than on the bulk water surface…”. In addition, Karkare and Fort [1994] used radiolabeled surfactant to demonstrate that surfactant‐induced flow in unsaturated sand columns was not correlated with surfactant spreading at the air‐water interface. So, though the potential exists for surfactant spreading at the air‐water interface in unsaturated media, the current experimental evidence suggests that this mechanism may not have a significant effect on surfactant‐induced flow behavior.…”

Section: Discussionmentioning

confidence: 99%

Two‐dimensional modeling of flow and transport in the vadose zone with surfactant‐induced flow

Henry

Smith

Warrick

2002

Water Resources Research

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[1] Surface-active solutes (surfactants) can induce capillary pressure gradients and water fluxes within the vadose zone. Common numerical models do not account for the effects of surfactant-induced capillary pressure gradients on unsaturated flow and transport. We modified the variably saturated flow and transport model HYDRUS-2D [Simunek et al., 1999] to incorporate the effects of surfactant concentration-dependent changes to surface tension and viscosity on moisture retention and hydraulic conductivity, respectively. The model was tested by simulating the two-dimensional surfactant infiltration experiment of Henry and Smith [2002]. The model successfully captured the major processes associated with the advance of a surface-active contaminant plume through the vadose zone, including drainage of the vadose zone and depression of the capillary fringe associated with the solute front. The simulations also provided insight into unusual features of surfactant-induced flow such as the upward flow of surfactant solution that was associated with capillary fringe drainage.

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Section: Discussionmentioning

confidence: 99%

Two‐dimensional modeling of flow and transport in the vadose zone with surfactant‐induced flow

Henry

Smith

Warrick

2002

Water Resources Research

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“…A static method developed by Karkare and Fort [1993, 1994, 1996], Karkare et al , [1993], and Silverstein and Fort [1997] relies on the principles of capillary action, and the use of a surfactant that forms a solid monolayer at the air‐water interface. With this method, a horizontally positioned column is packed with uniformly wetted porous media.…”

Section: Introductionmentioning

confidence: 99%

Air‐water interfacial areas in unsaturated soils: Evaluation of interfacial domains

Costanza-Robinson

Brusseau

2002

Water Resources Research

115

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A gas‐phase miscible‐displacement method, using decane as an interfacial tracer, was used to measure air‐water interfacial areas for a sand with water contents ranging from ∼2% to 20%. The expected trend of decreasing interfacial areas with increasing water contents was observed. The maximum estimated interfacial area of 19,500 cm−1 appears reasonable given it is smaller than the measured surface area of the porous medium (60,888 cm−1). Comparison of the experimental data presented herein with literature data provided further insight into the characterization of the air‐water interface in unsaturated porous media. Specifically, comparison of interfacial areas measured using gas‐phase versus aqueous‐phase methods indicates that the gas‐phase method generally yields larger interfacial areas than the aqueous‐phase methods, even when accounting for differences in water content and physical properties of the porous media. The observations are consistent with proposed differences in interfacial accessibility of the aqueous‐ and gas‐phase tracers. Evaluation of the data in light of functional interfacial domains, described herein, yields the hypothesis that aqueous interfacial tracers measure primarily air‐water interfaces formed by “capillary water,” while gas‐phase tracers measure air‐water interfaces formed by both capillary and surface‐adsorbed (film) water. The gas‐ and aqueous‐phase methods may each provide interfacial area information that is more relevant to specific problems of interest. For example, gas‐phase interfacial area measurements may be most relevant to contaminant transport in unsaturated systems, where retention at the air‐water interface may be significant. Conversely, the aqueous‐phase methods may yield information with direct bearing on multiphase flow processes that are dominated by capillary‐phase behavior.

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“…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.…”

Section: Introductionmentioning

confidence: 92%

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

Sánchez¹

2010

J. Braz. Chem. Soc.

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Experimentos do fluxo da água usando um meio poroso não saturado compoto por diferentes sistemas de a-alumina molhada não-saturada indicam que a carga superficial da partícula diminuiu com o aumento da água movimentada. O movimento máximo de água ocorreu quando a carga superficial era zero. O movimento da água foi afetado pela espessura da dupla camada elétrica no pH em que as partículas têm carga líquida (a partir do IEP pH ). Estes resultados sugerem estruturação da água, induzida por carga, adjacente a superfícies de partículas carregadas.Experiments of water flow using a non saturated porous medium constituted by different a-wet unsaturated alumina systems indicate that particle surface charge decreased the amount of water moved. Maximum water movement occurred when surface charge was zero. Water movement was affected by thickness of the electrical double layer at pH where particles have net charge (out of the IEP pH ). These results suggest charge-induced structuring of water adjacent to charged particle surfaces.

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Flow in "Unsaturated" Porous Media Due to Water-Insoluble Surfactants: Role of Momentum Transfer from a Spreading Monolayer

Cited by 16 publications

References 0 publications

Two‐dimensional modeling of flow and transport in the vadose zone with surfactant‐induced flow

Two‐dimensional modeling of flow and transport in the vadose zone with surfactant‐induced flow

Air‐water interfacial areas in unsaturated soils: Evaluation of interfacial domains

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

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