Neptunium(V) transport in granitic rock : A laboratory scale study on the influence of bentonite colloids

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Elo , O , Hölttä , P , Kekäläinen , P , Voutilainen , M & Huittinen , N M 2019 , ' Neptunium(V) transport in granitic rock : A laboratory scale study on the influence of bentonite colloids ' , Applied Geochemistry , vol. 103 , pp. 31-39 . https://doi.org/10.1016/j.apgeochem.2019.01.015

Titel: Neptunium(V) transport in granitic rock : A laboratory scale study on the influence of bentonite colloids
Författare: Elo, O.; Hölttä, P.; Kekäläinen, P.; Voutilainen, M.; Huittinen, Nina Maria
Upphovmannens organisation: Department of Chemistry
Datum: 2019-04
Språk: eng
Sidantal: 9
Tillhör serie: Applied Geochemistry
ISSN: 0883-2927
DOI: https://doi.org/10.1016/j.apgeochem.2019.01.015
Permanenta länken (URI): http://hdl.handle.net/10138/301163
Abstrakt: In the present study neptunium(V) uptake by crystalline granitic rock (Kuru Grey granite) and the role of stable and mobile bentonite colloids (MX-80) on the migration of neptunium(V) was investigated. Two different experimental setups were utilized, batch-type experiments under stagnant conditions and column experiments under flowing water conditions. The uptake of 10(-6) M neptunium(V) by 40 g/L crushed granite in 10 mM NaClO4 was found to be pH-dependent, whereas neptunium(V) uptake by MX-80 bentonite colloids (0.08-0.8 g/L) was pH-independent up to a pH-value of approximately 11. Column experiments were conducted in the presence and absence of colloids at two pH values (pH = 8 and 10) and two flow rates (0.3 and 0.8 mL/h) in 10 mM NaClO4. The injected neptunium(V) concentration was 2x10(-4) M and the colloid concentration ranged from 0.08 to 0.32 g/L. The properties of the flow field in the columns were investigated with a conservative chloride tracer, at the same two flow rates of 0.8 and 0.3 mL/h. The resulting breakthrough curves were modeled using the analytical solution of advection-matrix diffusion equation. A tailing of neptunium(V) breakthrough curves in comparison to the conservative tracer was observed, which could be explained by a slightly higher retardation of neptunium(V) in the column caused by sorption on the granite. The sorption was in general lower at pH 8 than at pH 10. In addition, the tailing was almost identical in the absence and presence of MX-80 bentonite colloids, implying that the influence of colloids on the neptunium(V) mobility is almost negligible.
Subject: 116 Chemical sciences
1171 Geosciences
Referentgranskad: Ja
Användningsbegränsning: openAccess
Parallelpublicerad version: publishedVersion


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