Spectroscopic study on the mononuclear hydrolysis species of Pu(VI) under oxidation conditions

Abstract

The formation constants of mononuclear hydrolysis species of Pu(VI) were determined by absorption spectroscopy under carefully designed experimental conditions In order to exclude the formation of polynuclear hydrolysis species, the concentration of plutonium was diluted below 50 mu M To maintain the oxidation state of Pu(VI) NaOCl was applied as an oxidant The trace amount of Pu(V) was monitored by the measurement of redox potential and absorption spectroscopy by using a liquid waveguide capillary cell with the optical path length of 100 cm The determined molar absorption coefficients (epsilon, M(-1) cm(-1)) were 272+/-26 and 436+/-33 for PuO(2)(OH)(+) and PuO(2)(OH)(2)(aq) species, respectively The formation constants of mononuclear hydrolysis species of Pu(VI) at ionic strength of 0 01 M NaClO(4) were determined as follows log *beta(1) (for PuO(2)(OH)(+)) = -5 8+/-0 3, log *beta(2) (for PuO(2)(OH)(2)(aq)) = -13 4+/-0 2 and log *beta(2)' (for PuO(2)(OH)(3)(-)) = -24 3+/-0 8