Spectroscopic Studies on the Thermodynamics of the Complexation of Trivalent Curium with Propionate in the Temperature Range from 20 to 90 °C

The thermodynamics of the stepwise complexation reaction of Cm(III) with propionate was studied by time resolved laser fluorescence spectroscopy (TRLFS) and UV/Vis absorption spectroscopy as a function of the ligand concentration, the ionic strength and temperature (20–90 °C). The molar fractions of the 1:1 and 1:2 complexes were quantified by peak deconvolution of the emission spectra at each temperature, yielding the log 10 values. Using the specific ion interaction theory (SIT), the thermodynamic stability constants log 10 were determined. The log 10 values show a distinct increase by 0.15 ( n = 1) and 1.0 ( n = 2) orders of magnitude in the studied temperature range, respectively. The temperature dependency of the log 10 values is well described by the integrated van’t Hoff equation, assuming a constant enthalpy of reaction and yielding the thermodynamic standard state values for the formation of the , n = (1, 2) species.