Modeling diffusion and adsorption in compacted bentonite; a critical review

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doi: 10.1016/S0169-7722(02)00128-6
Authors:Bourg, Ian C.; Bourg, Alain C. M.; Sposito, Garrison
Author Affiliations:Primary:
University of Pau, Environmental Hydrogeochemistry Group, Pau, France
University of California at Berkeley, United States
Volume Title:8th international conference on Chemistry and migration behaviour of actinides and fission products in the geosphere; Migration '01
Volume Authors:Kim, Jae-Il, editor; Geckeis, Horst
Source:Journal of Contaminant Hydrology, 61(1-4), p.293-302; 8th international conference on Chemistry and migration behaviour of actinides and fission products in the geosphere; Migration '01, Bregenz, Austria, Sept. 16-21, 2001, edited by Jae-Il Kim and Horst Geckeis. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0169-7722
Publication Date:2003
Note:In English. 45 refs.; illus.
Summary:The current way of describing diffusive transport through compacted clays is a simple diffusion model coupled to a linear adsorption coefficient (Kd). To fit the observed results of cation diffusion, this model is usually extended with an adjustable "surface diffusion" coefficient. Description of the negative adsorption of anions calls for a further adjustment through the use of an "effective porosity". The final model thus includes many fitting parameters. This is inconvenient where predictive modeling is called for (e.g., for waste confinement using compacted clay liners).The diffusion/adsorption models in current use have been derived from the common hydrogeological equation of advection/dispersion/adsorption. However, certain simplifications were also borrowed without questioning their applicability to the case of compacted clays. Among these simplifications, the assumption that the volume of the adsorbed phase is negligible should be discussed. We propose a modified diffusion/adsorption model that accounts for the volume of the adsorbed phase. It suggests that diffusion through highly compacted clay takes place through the interlayers (i.e., in the adsorbed phase). Quantitative prediction of the diffusive flux will necessitate more detailed descriptions of surface reactivity and of the mobility of interlayer species. Abstract Copyright (2003) Elsevier, B.V.
Subjects:Adsorption; Bentonite; Clastic rocks; Clastic sediments; Clay; Competent materials; Controls; Diffusion; Diffusivity; Disposal barriers; Isotopes; Mathematical models; Mechanism; Migration of elements; Mobility; Models; Pollution; Porosity; Porous materials; Prediction; Radioactive isotopes; Radioactive waste; Sedimentary rocks; Sediments; Transport; Waste disposal; Waste management
Record ID:2003043711
Copyright Information:GeoRef, Copyright 2018 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands
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