Solubility product of Pu(VI) hydrous oxide

The solubility of Pu(VI) hydrous oxide was measured in the pH(c) range from 4 to 5.5 at 25+/-2 degreesC in a NaClO4 solution containing 03 gas. The experiment was carried out by oversaturation and undersaturation methods at ionic strength I = 0.1, 0.5 and 1.0. The concentration of Pu(VI) was measured by alpha-spectrometry and UV/visible spectrophotometry, and the equilibrium constant of the reaction, PuO2(OH)(2) = PuO22+ +2OH(-), was obtained. From the obtained results, the solubility products (K-sp) of Pu hydrous oxide at I = 0.1, 0.5 and 1.0 were determined. The experimental values were extrapolated to the standard state (I = 0) by using the specific interaction theory (SIT), and the solubility product of Pu hydrous oxide was determined to be log K-sp(degrees) = -22.88+/-0.39. The ion interaction coefficient epsilon (PuO22+, ClO4-) was also evaluated to be 0.30+/-0.09.