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

Autor: Yoshiki Kinoshita, Masao Morishita, Hiroaki Yamamoto, Ai Nozaki
Rok vydání: 2018
Předmět:
Zdroj: Applied Geochemistry. 98:310-320
ISSN: 0883-2927
DOI: 10.1016/j.apgeochem.2018.08.023
Popis: The standard molar entropy Δ 0 T S 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 p , m ° at the temperature of 2 K and above using the most recent Debye-Einstein formula. The Δ 0 T S 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, Δ f G m ° , of MgMoO4, SrMoO4(cr) and BaMoO4(cr) were determined by combining the Δ 0 T S m ° data with the reference data for the standard enthalpy of formation, Δ f H m ° . The Δ f G 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, Δ sln G m ° , and the solubility product, Ks, at 298.15 K for MgMoO4 were predicted. The thermodynamic values were obtained as follows: Δ 0 T S m ° (MgMoO4(cr), 298.15 K)/(J K−1 mol−1) = 119.11 ± 1.19; Δ 0 T S m ° (SrMoO4(cr), 298.15 K)/(J K−1 mol−1) = 136.44 ± 1.36; Δ 0 T S m ° (BaMoO4(cr), 298.15 K)/(J K−1 mol−1) = 152.61 ± 1.53; Δ f G m ° (MgMoO4(cr), 298.15 K)/(kJ mol−1) = −1295.73 ± 0.91; Δ f G m ° (SrMoO4(cr), 298.15 K)/(kJ mol−1) = −1441.32 ± 1.36; Δ f G m ° (BaMoO4(cr), 298.15 K)/(kJ mol−1) = −1443.29 ± 1.33; Δ f G m ° (MoO42−(aq), 298.15 K)/(kJ mol−1) = −836.63 ± 0.97. Δ sln G m ° (MgMoO4(aq),298.15 K)/(kJ (mol of MoO42−(aq))−1) = 3.72 ± 1.88. Ks(MgMoO4(aq), 298.15) = 2.23 × 10−1 ± 4.46 × 10−2 The thermodynamic data obtained in this work are expected to be useful for nuclear fuel waste safety management.
Databáze: OpenAIRE
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