Sorption behavior of neptunium onto smectite under reducing conditions in carbonate media

Kitamura, Akira ; Tomura, Tsutomu*; not registered

Sorption behavior of neptunium onto smectite was investigated upder reducing conditions in carbonate media. Distribution coefficient (K $_{d}$ ) of neptunium on smectite was determined by a batch method as a function of total carbonate concentration (C $_{T}$ ) in a weak alkaline solution. The C $_{T}$ value ranged from 0.09 M (Mmoldm $^{-3}$ ) to 1.0 M. The obtained K $_{d}$ value decreased with increase the total carbonate concentration. It was found that both Np(IV) and Np(V) coexisted in the solution by a TTA-extraction method. In the present experimental conditions, contribution of neptunyl ion, NpO $_{2}$ $^{+}$ , carbonate complexes of Np(V), NpO $_{2}$ (CO $_{3}$ ) $_{n}$ $^{(2n-1)-}$ (n=1, 2 and 3), and a carbonatohydroxo complex of Np(IV), Np(CO $_{3}$ ) $_{2}$ (OH) $_{2}$ $^{2-}$ , to the sorption onto smectite was expected. The K $_{d}$ values of respective species of neptunium were estimated by a least-squares fit to the experimental data. From the obtained K $_{d}$ values of respective species, sorption behavior of neptunium onto smectite was discussed.

Language	:	English
Report No.	:	JNC TN8400 2001-015
Pages	:	30 Pages
Publication Year/Month	:	2001/09
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PDF	:	JNC-TN8400-2001-015.pdf:3.94MB
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Keywords	:	no keyword
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Registration No. : GJ0820010063
JAEA Abstracts No. :

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