Thermodynamic properties of uranyl ion in aqueous solution at high temperature

To specify the values of standard enthalpies and free energies of UO22+ (solution) formation at high temperatures, enthalphies of UO2(NO3)2x6H2O dissolution in the aqueous solution of HClO4 of different molalities (m=0.01-0.18 mol/kg H2O) have been measured. On the basis of results of calorimetric measurements and analysis of literary data, values of thermodynamic properties (Cp0, S0 and δG0fT) of uranyl ion in the temperature range of 25-300 deg C, are calculated and recommended. The equation of the temperature dependence of partial molal thermal capacity of uranyl is obtianed that can be recommended for thermodynamic analysis of conditions for migration and uranium concentration in natural processes, as well as for the development of chemical-technological scheme of reprocessing uranium raw materials