Simultaneous Crystallization of Cyclopentane Hydrate and Sodium Chloride for Desalination and Salt Manufacture

Simultaneous crystallization of cyclopentane hydrate and sodium chloride dihydrate was implemented to demonstrate a dual-functional system for hydrate-based seawater desalination and salt manufacture that could be performed with zero emission. A sodium chloride aqueous solution having an initial mass fraction of sodium chloride of 0.235 or 0.264 was used for the experiments as an alternative to seawater. When using the aqueous solution having a sodium chloride concentration of 0.264 in mass fraction, the precipitation of polyhedral sodium chloride dihydrate crystals was first observed, followed by the formation of particulate cyclopentane hydrate crystals. In contrast, when using the aqueous solution having a sodium chloride concentration of 0.235 in mass fraction, the formation of particulate cyclopentane hydrate was first observed and then the particulate sodium chloride dihydrate precipitated. The formed cyclopentane hydrate and the precipitated sodium chloride dihydrate were separated by the remaining sodium chloride aqueous solution due to the density difference even after the agitation of the system. The eutectic temperature and concentration were determined to be 259.75 K and 0.238 in mass fraction of sodium chloride, respectively.