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A. C. Grégoire-Kappenstein, Philippe Moisy, Gérard Cote, P. Blanc

Dimerization of Np(V) and media effects in concentrated solutions

Highly concentrated (up to 3.56mol L^-1) binary solutions of NpO₂NO₃ were prepared to investigate the self-association of Np(V). By using visible/NIR absorption spectrophotometry and chemometric techniques, Np(V) was shown to be only monomeric below 0.2mol L^-1, to exist under its monomeric and dimeric forms between 0.2 and 2mol L^-1, to begin to form self-associates of higher degrees above 2mol L^-1. In the range 0.2mol L^-1 < C_Np(V)<2mol L^-1, the neptunium distribution between the free NpO₂⁺ and dimeric (NpO₂)₂²⁺ forms was determined by Raman spectroscopy. The simple solution concept was used to establish the activity function for the reaction of dimerization. Such a water activity function can be used to calculate the apparent dimer formation constant for any solution of known composition and water activity, provided that this solution is simple.

Radiochimica Acta, Oldenbourg Wissenschaftsverlag

Print ISSN: 0033-8230
Volume: 91, 11/2003
Pages: 665

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