A comprehensive review on the characteristics and kinetics of freshwater separation by hydrate-based method: Current progress, challenges and perspectives

Freshwater is an indispensable source of life for human beings, while desalination is one of the main ways of freshwater replenishment. Hydrate technology is considered to be a promising technical proposal in the fields of freshwater production and wastewater treatment. Therefore, this paper addresses the desalination and freshwater separation technology by hydrate method, comprehensively reviews the effects of guest molecules, promoters, reaction systems, reaction devices and other factors on the formation and decomposition characteristics of hydrate. On this basis, the influence of post-treatment process on hydrate crystals and freshwater recovery under different conditions has been quantitative analyzed. The mechanism and its law of the influence of factors such as the guest molecular, the component ratio, the temperature and pressure conditions (TPC), the ionic type and concentration, and the water content on the freshwater separation efficiency have been revealed. Furthermore, understanding the the rapid formation and decomposition mechanism of hydrate still need to be further studied. Finally, the deficiencies of freshwater separation technology by hydrate method and the future development direction were pointed out in detail. "Green" and efficient facilitation technology should be developed as much as possible and the formation/dissociation kinetics of hydrate should be studied more deeply. The process and its economy for industrial application need to be further optimized and improved in the future.