Equilibrium properties and crystal growth of D 2 O  + cyclopentane hydrate for sustainable tritium separation

Abstract This study reports thermodynamic properties and crystal growth observations of D 2 O + cyclopentane hydrate toward the development of a hydrate‐based tritium separation process. We employed D 2 O as a host of hydrate with respect to the investigation into the formation of D 2 O hydrate substrate, which is a core component of the tritium separation process. The hydrate phase equilibrium temperature in the liquid D 2 O + liquid cyclopentane system was 3.2°C higher than the corresponding H 2 O 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 D 2 O/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 H 2 O + cyclopentane hydrate. Implications based on the obtained results for the hydrate‐based isotopic water separation process design are discussed.