Development of dual functional methodology for seawater desalination and salt manufacture by carbon dioxide hydrate formation

Clathrate-hydrate-based seawater desalination is a novel technology that is performed by reaction between seawater and guest compounds to obtain fresh water. This study proposed a dual functional methodology for seawater desalination and salt manufacture by using carbon dioxide clathrate hydrate. In this methodology, the clathrate hydrate formation continues until the concentration of electrolytes in unreacted brine reaches the saturated solubility for the salt precipitation. The visual observation of the clathrate hydrate formation and the salt precipitation coupled with the analysis utilizing the powder X-ray diffraction (PXRD) technique was implemented to demonstrate the methodology. The carbon dioxide clathrate hydrate formation was first performed with sodium chloride aqueous solution. The carbon dioxide clathrate hydrate crystals floated on high salinity water. This experiment was followed by the occurrence of the sodium chloride dihydrate precipitation upon the carbon dioxide clathrate hydrate formation. The formed compounds, carbon dioxide clathrate hydrate and sodium chloride dihydrate, were identified by PXRD analysis. The mass fraction of the compounds was also determined by PXRD.