Diffusion of14C in dense saturated bentonite under steady-state conditions

Oscarson, D. W.; Hume, Harold B.

doi:10.1007/bf00617028

Cited by 14 publications

(5 citation statements)

References 17 publications

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“…An enhanced transport of H 2 O through the gas phase compared to the liquid in partially saturated rocks was suggested by Gimmi et al (1997). A rapid transport through the gas phase is also consistent with findings for diffusion of 14 C in dense bentonite by Oscarson and Hume (1994). However, direct evidence for unsaturated conditions could not be obtained for this experiment.…”

Section: Samplesupporting

confidence: 88%

Diffusive transport of water in porous feldspars from granitic saprolites: In situ experiments using FTIR spectroscopy

Simonyan

Behrens

Dultz

2009

Geochimica et Cosmochimica Acta

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Section: Samplesupporting

confidence: 88%

Diffusive transport of water in porous feldspars from granitic saprolites: In situ experiments using FTIR spectroscopy

Simonyan

Behrens

Dultz

2009

Geochimica et Cosmochimica Acta

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“…More recently, a reduced diffusive solute flux of naphthalene, an aqueous miscible organic compound (nonelectrolyte), through a montmorillonite-based shale has been attributed to exclusion of the naphthalene from the pore space (17). Similar solute exclusion effects for a variety of inorganic solutes have been reported in studies involving the use of compacted sodium bentonites being considered for use as containment barriers for nuclear waste repositories (18)(19)(20)(21).…”

Section: Introductionmentioning

confidence: 63%

Coupling Effects during Steady-State Solute Diffusion through a Semipermeable Clay Membrane

Malusis

Shackelford

2002

Environ. Sci. Technol.

127

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Two separate coupling effects are evaluated with respect to steady-state potassium chloride (KCl) diffusion through a bentonite-based geosynthetic clay liner (GCL) that behaves as a semipermeable membrane. Both of the coupling effects are correlated with measured chemico-osmotic efficiency coefficients, omega, that range from 0.14 to 0.63 for the GCL. The first coupling effect is an explicit (theoretical) salt-sieving effect expressed as a coupled effective salt diffusion coefficient, Domega*, that is lower than the true (uncoupled) effective salt diffusion coefficient, Ds*, because of the observed membrane behavior. However, the maximum difference between Domega* and Ds* based on measured chloride concentrations is relatively small (i.e., = 10%), and the difference decreases with decreasing omega (i.e., Domega* --> Ds* as omega --> 0). The second coupling effect is implicit (empirical) and is characterized by the measurement of concentration-dependent effective salt diffusion coefficients that results in an degrees 300% decrease in Ds* as omega increases from 0.14 to 0.63. The decrease in Ds* resulting from implicit coupling is attributed to solute exclusion described in terms of a restrictive tortuosity factor.

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“…Mott and Weber () found tortuosity factors between 0.96 and 1.5 for trichloroethene, 1,4-dichorobenzene, and 4-chorophenol diffusion through soil/bentonite systems. Other investigators have suggested that measured diffusion coefficient in low-permeable materials have typi cally been accurate only to within a factor of 4 ( , ).…”

Section: Resultsmentioning

confidence: 99%

Estimating Diffusion Coefficients in Low-Permeability Porous Media Using a Macropore Column

Young

Ball

1998

Environ. Sci. Technol.

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Diffusion coefficients in an aquitard material were measured by conducting miscible solute transport experiments through a specially constructed macropore column. Stainless steel HPLC columns were prepared in a manner that created an annular region of repacked aquitard material and a central core of medium-grained quartz sand. The column transport approach minimizes volatilization and sorption losses that can be problematic when measuring hydrophobic organic chemical diffusion with diffusion-cell methods or column-sectioning techniques. In the transport experiments, solutes (tritiated water, 1,2,4trichlorobenzene, and tetrachloroethene) were transported through the central core by convection and hydrodynamic dispersion and through the low-permeability annulus by radial diffusion. All transport parameters were independently measured except for the effective diffusion coefficient in the aquitard material, which was obtained by model fitting. Batch-determined retardation factors agreed very closely with moment-derived retardation factors determined from the column experiments, and no evidence of pore exclusion was found. A model with retarded diffusion was found to apply, and the effective tortuosity factor of the aquitard material was estimated at an average value of 5.1 (based on estimates that ranged from 3.7 to 7.7).

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Diffusion of14C in dense saturated bentonite under steady-state conditions

Cited by 14 publications

References 17 publications

Diffusive transport of water in porous feldspars from granitic saprolites: In situ experiments using FTIR spectroscopy

Diffusive transport of water in porous feldspars from granitic saprolites: In situ experiments using FTIR spectroscopy

Coupling Effects during Steady-State Solute Diffusion through a Semipermeable Clay Membrane

Estimating Diffusion Coefficients in Low-Permeability Porous Media Using a Macropore Column

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