Exploring thermodynamic viable conditions for separation of highly energy intensive H2O and D2O mixtures through gas hydrate based process

The separation of heavy water (D2O) from light water (H2O) is an energy-intensive process. Heavy water is primarily used in nuclear reactors but has vast applications in medical and biological investigations. This paper comprehensively investigates suitable thermodynamic conditions for separating heavy water from light water using gas hydrates. Gas hydrates, which are crystalline structures made up of water and gas molecules, have drawn much interest because of their usage to separate gas mixtures. In this work, however, using high-pressure Differential Scanning Calorimetry, different thermodynamic phase boundaries of hydrate formation from the liquid mixture of D2O and H2O were explored for preferential separation of D2O as solid hydrates. Utilizing a laboratory scale, high-pressure reactor differences in the kinetics of hydrate growth using heavy water and light water were also investigated, thus clearly showing that the hydrate formation and dissociation process could be utilized for separating the two water isotopes. In this work, hydrates were formed at 278.15 K using methane & natural gas to understand the thermodynamic phase behavior of these hydrates. Since kinetics and morphology of hydrate formation are also crucial for a scale-up, comparing two different types of hydrate former will help understand the behavior better. The results of this study contribute to the fundamental understanding of thermal behavior and the kinetics of hydrate formation of light and heavy water. The comparative analysis of DSC thermograms provides valuable insights into the effects of isotopic substitution on the phase transitions of water.