Solubility product of plutonium hydrous oxide and its ionic strength dependence

Abstract

Summary The solubility of PuO 2 · x H 2 O was measured at 25°C in a NaClO 4 solution containing Na 2 S 2 O 4 as a reductant. The experiment was carried out by an oversaturation method at I = 1.0 and by an undersaturation method at I = 0.5, 1.0 and 2.0. The concentration of Pu 3+ was measured by α-spectrometry and UV/Visible spectrophotometry, and the equilibrium constant of the reaction, PuO 2 · x H 2 O + e − = Pu 3+ + 4 OH − + (x–2) H 2 O, was obtained. From the obtained results, the solubility product ( K sp ) of PuO 2 · x H 2 O, for PuO 2 · x H 2 O = Pu 4+ + 4 OH − + (x − 2) H 2 O at I = 0.5, 1.0 and 2.0 was determined. By using the specific interaction theory (SIT), the solubility product of PuO 2 · x H 2 O at the standard state ( I = 0) was determined to be log K ° sp = −57.97 ± 0.24, and the ion interaction coefficient ε(Pu 4+ , ClO 4 -) was also evaluated to be 0.99 ± 0.20.