Probing the Effects of Ultrasound-Generated Nanobubbles on Hydrate Nucleation: Implications for the Memory Effect

Understanding the microscopic hydrate phase transitionprocessis of crucial importance to the application of hydrate-based techniques.This process is nevertheless significantly limited by the insufficientenrichment of hydrophobic gas molecules in the solution. Here, inthis work, ultrasonic technology was applied to generate stable andlarge amount of nanobubbles in pure water to promote hydrate formationkinetics. The particle size distribution of the nanobubbles was followingthe log-normal distribution, with a concentration of similar to 10(9) mL(-1) and a diameter concentrated in 100-120nm. The concentration of the nanobubbles increased with the ultrasonicduration and power. Notably, the concentrations of nanobubbles producedby hydrate decomposition were slightly higher with the bubble sizeconcentrated around 200 nm. The effect of nanobubbles on the inductiontime of hydrate formation was further analyzed by forming from thenanobubble solution with different concentrations and particle sizedistributions. Hydrate formation induction time was reduced by upto 61.13%. We further analyzed the mechanism of the nanobubble dominanthydrate memory effect. The results proved ultrasound as an approachto enhance the solubility of gases in water and thus promote hydrateformation kinetics, providing evidence for the dominant role of nanobubblesin the memory effect.