Thermodynamic insights into H2O-D2O separation via gas hydrate formation with HFC134a

This study investigates the thermodynamic phase behavior of mixed H2O and D2O systems using HFC134a gas hydrates, focusing on the potential for separating D2O from H2O. Hydrate formation and dissociation experiments were conducted on pure H2O, D2O, and their 50:50 vol% mixtures. Phase equilibrium data were obtained using the isochoric pressure-volume-temperature (PVT) method, and the Clausius-Clapeyron equation was applied to calculate dissociation enthalpies. The results revealed distinct differences in hydrate stability, with D2O hydrates forming at lower pressures and higher temperatures than H2O. The mixed system exhibited intermediate thermodynamic properties, reflecting the influence of both H2O and D2O within the hydrate. The dissociation enthalpy for H2O+HFC134a is approximately 131.85 kJ/mol, while D2O+HFC134a is about 167.28 kJ/mol. The dissociation enthalpy for the mixed hydrate is approximately 145.23 kJ/mol indicating an increase of about 10.14 % compared to H2O+HFC134a and a decrease of approximately 13.18 % compared to D2O+HFC134a. These findings highlight the potential for using HFC134a hydrates as an effective method for D2O and H2O separation, with future work aiming to explore their thermodynamic regimes and optimize experimental conditions for feasible separation.