Self-driven and directional transport of water during hydrate formation: Potential application in seawater desalination and dewatering

Hydrate-based desalination has attracted considerable attention as an innovative desalination process without extra pollution; however, the slow kinetics of hydrate formation and the difficulty of separating solid hydrate from liquid brine hinder the industrialization of this technology. Hydrates exhibit water absorption effects and can be formed above silica sand beds to promote separation. Unfortunately, the mechanism underlying the self-driven and continuous directional transport of water during hydrate formation is unclear. In this study, the spatial and temporal formation behavior of hydrate in quartz glass beads were observed using a nuclear magnetic resonance system. The results revealed that not all types of guest molecules capable of forming hydrates exhibited the hydrate water absorption effect. The interfacial tension between the hydrate and bound water provided capillary driving force for water migration. Large particle sand had larger pore channels for water migration and low initial water saturation will inhibited water migration. The results of this study improve the understanding of water migration during hydrate formation in porous media. Our findings have significant potential for the application in desalination, sludge dewatering processes, and gas capture. •Not all types of hydrate guest molecules exhibit the hydrate water absorption effect.•Mechanism underlying the self-driven and continuous directional transport of water is analyzed.•Gases with low solubility tend to nucleate at the gas–liquid interface.•The capillary force of water in a porous structure drives water migration.•Sands with large particle sizes have large pore channels, which promote migration.