THERMODYNAMICS OF CURIUM(III) IN CONCENTRATED ELECTROLYTE-SOLUTIONS -FORMATION OF SULFATE COMPLEXES IN NACL NA2SO4 SOLUTIONS/

The formation of sulfate complexes of Curium in aqueous solutions is s tudied by time resolved laser fluorescence spectroscopy (TRLFS) at 25 degrees C. The species Cm3+, Cm(SO4)(+), Cm(SO4)(2)(-) and Cm(SO4)(3)( 3-) are quantified spectroscopically in the trace concentration range by peak deconvolution of fluorescence emission spectra. The complex fo rmation equilibria are measured in NaCl/Na2SO4 solutions of constant i onic strength (3 molal) as a function of the sulfate concentration. Th e stability constants of Cm(SO4)(+) and Cm(SO4)(2)(-) are determined t o be log beta(1) = 0.93+/-0.08 and log beta(2) = 0.61+/-0.08, respecti vely. The complex Cm(SO4)(3)(3-) is found to be stable only at very hi gh sulfate concentrations (above 1 molal) and therefore not considered for further evaluation.