Affiliation:
1. Inspection and Development Company, 4-33, Muramatsu, Ibaraki-ken, Japan
Abstract
Abstract
The hydrolysis constants of tetravalent neptunium (Np(IV)) were determined by solvent extraction method using thenoyltrifluoroacetone(TTA). In order to avoid colloid formation, a stock solution of carrier-free 239Np(V) was from 243Am milked. The valence of Np in the solution was then reduced to Np(IV) by using zinc amalgam. The hydrolysis constants (β
m
) of the reactions, Np4++mOH−=Np(OH)
m
(4−m)+ was evaluated by using distribution ratios at ionic strengths (I)=0.1, 0.5 and 1.0. All experiments were performed in oxygen- free 0.5% H2−N2 atmosphere (below 1.0 ppm of O2) in a glovebox at room temperature (23±2 °C) to avoid oxidation of Np(IV). The β
m
values were extrapolated to the standard state (I=0) by using the specific ion interaction theory (SIT), and the formation constants at I=0 were determined to be logβ
1°=13.91±0.23, logβ
2°=27.13±0.15, logβ
3°=37.70±0.30 and logβ
4°=46.16±0.30. The ion interaction coefficients were also evaluated to be ε(NpOH3+, ClO4
−)=0.49±0.15, ε(Np(OH)2
2+, ClO4
−)=0.35±0.11, and ε(Np(OH)3
+, ClO4
−)=0.29±0.15.
Subject
Physical and Theoretical Chemistry
Cited by
7 articles.
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