Solubility of uranium(IV) hydrous oxide in high pH solution under reducing condition

The solubility of uranium(IV) hydrous oxide was measured at 25 degrees C in NaClO4 solution containing Na2S2O4 as a reducing agent in the pH range from 12 to 14. The experiment was carried out from oversaturation at I = 0.5, 1.0 and 2.0 mol/dm(3) (M). The solubility data were analyzed to obtain the hydrolysis constants (beta(m)) of U(OH)(m) ((4-m)). By taking the specific ion interaction theory (SIT) for ionic strength corrections and by using the solubility product log K(sp)degrees = -53.93 +/- 0.20, the hydrolysis constants at I = 0, log beta(5)degrees < 48.10 and log beta(6)degrees = 48.95 +/- 1.01, were determined together with the ion interaction coefficients of U(OH)(5)(-) and U(OH)(6)(2-).