Desalination of high-salt brine via carbon materials promoted cyclopentane hydrate formation

Abstract

Significant advances in seawater desalination have been made to meet the world's increasing demand for clean water. However, the accompanying hypersaline concentrate discharge has negative environmental impact and is challenging for treatment. Herein, we demonstrate the potential of hydrate-based desalination (HBD) in treating brine with concentrations up to 16 wt%. It is difficult for hydrate nucleation to occur in strong brine without nucleation agents, as this results in lengthy induction time, the challenge can be resolved using carbon materials. We found that crystallinity and surface compositions have critical impact on cyclopentane hydrate formation and desalination efficiency. Carbon material with high crystallinity is more effective in inducing hydrate nucleation in NaCl solution due to the properly tuned interface hydrogen-bonding network as confirmed by Raman spectra. The improved hydrophilic property would degrade the desalting efficiency due to the tightly trapped brine among carbon materials and hydrate crystals. Although high concentration of NaCl would hinder hydrate formation, leading to a lower water recovery, desalting efficiency unexpectedly increases due to interfacial pre-melting in the presence of salt, reaching up to 79% in 16 wt% NaCl. The findings would help to identify and fabricate the good hydrate promoters used for HBD for treating hypersaline brine.