This study reports thermodynamic properties and crystal growth observations of D2O + cyclopentane hydrate toward the development of a hydrate-based tritium separation process. We employed D2O as a host of hydrate with respect to the investigation into the formation of D2O hydrate substrate, which is a core component of the tritium separation process. The hydrate phase equilibrium temperature in the liquid D2O + liquid cyclopentane system was 3.2°C higher than the corresponding H2O hydrate. Experiments on crystal growth were conducted at temperatures ranging from 5.1 to 8.5°C under atmospheric pressure. Under each thermodynamic condition, polygonal hydrate crystals appeared, growing along the D2O/cyclopentane interface. The geometric shape and size of the crystals varied depending on the temperature. The variation in crystal morphology was comparable to that of the H2O + cyclopentane hydrate. Implications based on the obtained results for the hydrate-based isotopic water separation process design are discussed.
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