Diffusion of U(VI) in Opalinus Clay: Influence of temperature and humic acid

Joseph, Claudia; Loon, Luc R. Van; Jakob, A.; Steudtner, Robin; Schmeide, Katja; Sachs, Susanne; Bernhard, Gert

doi:10.1016/j.gca.2013.01.027

Cited by 60 publications

(47 citation statements)

References 54 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…9, it can be derived that when S 1 = 100 nm and S 2,3 = 50 nm, D 1 = 5.1 × 10 −11 m 2 /s and D 3 = 1.3 × 10 −11 m 2 /s. These values and the ratio of D 3 /D 1 are closest to the experimental data (Van Loon et al 2004;Joseph et al 2013).…”

Section: Effective Diffusivity Of Systems With Different Length Scalessupporting

confidence: 85%

A Network Model for Diffusion in Media with Partially Resolvable Pore Space Characteristics

Jivkov

Xiong

2014

Transp Porous Med

View full text Add to dashboard Cite

A microstructure-informed meso-scale model for diffusion of foreign species in porous media is proposed. The model is intended for media where the pore geometry data acquired experimentally represent a fraction of total porosity. A cellular complex, with a cell representing the average pore neighbourhood, is used to generate 3D graphs of sites at cell centres and bonds between neighbouring cells. The novel interpretation of pore systems as graphs allows for clear separation between topology (here connectedness) and physics (here diffusion) in the mathematical formulation of transport. Further, it allows for easy introduction of dynamics into the system, i.e., local changes in topology due to other physical mechanisms, such as micro-cracking or blockage of pores. A mapping between microstructure features and graph elements is used for model construction. The mapping is based on data for clays, where the experimentally resolved pore system comprises isolated elongated pores of preferred orientation with a large volume fraction of unresolved pores. Both the resolved and the "hidden" systems are accounted for. The graph geometry is described by a principal length, the cell size in the preferred orientation, and a secondary length, the cell size out of preferred orientation. This is considered as a representation of mineralogical heterogeneity of clays. Analysis on graphs, a specialisation of the discrete exterior calculus, is used to obtain connectivity and diffusivity properties of formed networks. Since the experimental data are not sufficient to determine the principal length, upper and lower limits are determined from the limited information. Effects of the principal cell size between limits and of the secondary cell size are studied. The results are within the range of experimentally measured macroscopic (bulk) diffusivity for the material studied, including anisotropic diffusion coefficients. The variation of calculated diffusivity coefficients with principal and secondary lengths provides an explanation for the variability in experimentally measured coefficients across different clays.

show abstract

Section: Effective Diffusivity Of Systems With Different Length Scalessupporting

confidence: 85%

A Network Model for Diffusion in Media with Partially Resolvable Pore Space Characteristics

Jivkov

Xiong

2014

Transp Porous Med

View full text Add to dashboard Cite

show abstract

“…1-1.5 orders of magnitude. (Yaroshchuk and Van Loon, 2008), Na + and Sr 2+ , U(VI) (Joseph et al, 2013), Np(V) (Wu et al, 2009) and Co(II) (Van Loon and Müller, 2015), all measured on Opalinus Clay. The total porosity for calculating effective diffusion coefficients for HTO and cations with Eq.…”

Section: Surface Diffusionmentioning

confidence: 99%

“…In Switzerland, several clay rocks are currently under investigation (Nagra, 2008). Up to the present sorption and diffusion studies were performed solely on Opalinus Clay (Van Loon et al, 2003a, 2005Appelo et al, 2010;Wu et al, 2009;Joseph et al, 2013). Because diffusion is the main transport process in clay rocks, diffusion parameters are important input data for safety analysis, making reliable methods for estimating diffusion coefficients essential.…”

Section: Introductionmentioning

confidence: 99%

A modified version of Archie’s law to estimate effective diffusion coefficients of radionuclides in argillaceous rocks and its application in safety analysis studies

Loon

Mibus

2015

Applied Geochemistry

View full text Add to dashboard Cite

“…As evidenced below, this simplicity is instrumental in identifying the key trends associated with water and ion diffusion in clay materials. The diffusion of more complex or less extensively studied species such as oxyanions (Aertsens et al, 2003;Jansson and Eriksen, 2004;Sato and Miyamoto, 2004), actinides Joseph et al, 2013), lanthanides , trace metals (Lange et al, 2009), dissolved gases (Higashihara et al, 2004(Higashihara et al, , 2005, and organic molecules (Chapman and Parker, 2005;Martens et al, 2010) is not addressed here despite its interest in a range of areas. Diffusion in unsaturated conditionsdan important phenomenon in soils (Calvet, 1973;Nye, 1979) and, potentially, in HLRW repositories in certain conditions (Savoye et al, 2010)dis not discussed.…”

Section: Introductionmentioning

confidence: 99%