Hydrate based desalination for sustainable water treatment: A review

Desalination processes are key to untangle the energy-water-environment nexus, to attain a green equitable world, and to address water scarcity on all continents. However, conventional desalination methods are energy-intensive, which stresses the balance of the nexus. Hydrate based desalination (HBD) is an innovative desalination process with the potential to desalinate both low- and high-salinity streams, including brackish water, seawater, and effluents. It recovers clean water in the form of ice-like structures, known as gas hydrates. Gas hydrates are crystalline nonstoichiometric solids composed of interlocking water molecules that physically encompass gaseous guest molecules. During the hydrate formation process, dissolved ions and salts are excluded from the hydrate crystals, resulting in high purity ice-like structures. This paper presents a comprehensive review on our fundamental understanding of gas hydrates and their applications in desalination. The effect of additives on the kinetics of HBD, which remains its Achilles' heel, is also studied. Finally, a comparative analysis between HBD and conventional desalination methods regarding their energy requirements indicates the strong potential of HBD as an energy efficient and selective desalination method, which could improve the overall sustainability of the energy-water-environment nexus.