Thermodynamic properties for MMoO4 (M = Mg, Sr and Ba) as the end-members of the yellow phases formed in the nuclear fuel waste glasses

摘要

The standard molar entropy Delta S-T(0)degrees(m) at 298.15 K of MgMoO4(cr) of the end-members of the yellow phases formed in the nuclear fuel waste glasses was determined by measuring C degrees(p), (m) at the temperature of 2K and above using the most recent Debye-Einstein formula. The Delta S-T(0)degrees(m) data obtained in our previous study for SrMoO4(cr) and BaMoO4(cr) were re-evaluated using this most recent formula. The standard Gibbs free energies of formation, Delta(f)G degrees(m) of MgMoO4, SrMoO4(cr) and BaMoO4(cr) were determined by combining the Delta S-T(0)degrees(m) data with the reference data for the standard enthalpy of formation, Delta H-f degrees(m). The Delta(f)G degrees(m) of MoO42-(aq) was updated from the thermodynamic cycle based on the data obtained in the present work. The unknown standard Gibbs free energy of solution, Delta(sln) G degrees(m), and the solubility product, K-s, at 298.15K for MgMoO4 were predicted. The thermodynamic values were obtained as follows: