Solubility product of plutonium hydrous oxide and its ionic strength dependence

Abstract

SummaryThe solubility of PuO2·xH2O was measured at 25°C in a NaClO4solution containing Na2S2O4as a reductant. The experiment was carried out by an oversaturation method atI= 1.0 and by an undersaturation method atI= 0.5, 1.0 and 2.0. The concentration of Pu3+was measured by α-spectrometry and UV/Visible spectrophotometry, and the equilibrium constant of the reaction, PuO2·xH2O + e−= Pu3++ 4 OH−+ (x–2) H2O, was obtained. From the obtained results, the solubility product (Ksp) of PuO2·xH2O, for PuO2·xH2O = Pu4++ 4 OH−+ (x − 2) H2O atI= 0.5, 1.0 and 2.0 was determined. By using the specific interaction theory (SIT), the solubility product of PuO2·xH2O at the standard state (I= 0) was determined to be logK°sp= −57.97 ± 0.24, and the ion interaction coefficient ε(Pu4+, ClO4-) was also evaluated to be 0.99 ± 0.20.