Determination of uranium(IV) hydrolysis constants and solubility product of UO₂·<i>x</i>H₂O

Abstract

Summary The hydrolysis constants of tetravalent uranium were determined by a solvent extraction method using thenoyltrifluoroacetone(TTA) and 233 U. 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 β 1 °=13.71±0.31, β 2 °=26.12±0.21 and β 3 °=36.85±0.36, together with the ion interaction coefficients of UOH 3+ , U(OH) 2 2+ and U(OH) 3 + . The solubility product ( K sp ) for the reaction of UO 2 · x H 2 O=U 4+ +4OH - + (x-2)H 2 O was also calculated to be log K sp ° =-53.93±0.20 by considering the hydrolysis constants.