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Kenso Fujiwara, Hajimu Yamana, Toshiyuki Fujii, Hirotake Moriyama

Determination of uranium(IV) hydrolysis constants and solubility product of UO₂·xH₂O

The hydrolysis constants of tetravalent uranium were determined by a solvent extraction method using thenoyltrifluoroacetone(TTA) and ²³³U. The distribution ratio of U(IV) was measured as a function of the pH_c value in the aqueous phase at I=0.1, 0.5 and 1.0, and was analyzed to obtain the hydrolysis constants (β_m) of U(OH)_m^{(4-m )+} at the standard state (I=0). By taking the specific ion interaction theory (SIT) for ionic strength corrections, the hydrolysis constants at I=0 were determined to be β₁°=13.71&plusm;0.31, β₂°=26.12&plusm;0.21 and β₃°=36.85&plusm;0.36, together with the ion interaction coefficients of UOH³⁺, U(OH)₂²⁺ and U(OH)₃⁺. The solubility product (K_sp) for the reaction of UO₂· x H₂O=U⁴⁺+4OH^- + (x-2)H₂O was also calculated to be log K_sp° = -53.93&plusm;0.20 by considering the hydrolysis constants.

Radiochimica Acta, Oldenbourg Wissenschaftsverlag

Print ISSN: 0033-8230
Volume: 91, 06/2003
Pages: 345

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