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

Understanding the microscopic hydrate phase transition process is of crucial importance to the application of hydrate-based techniques. This process is nevertheless significantly limited by the insufficient enrichment of hydrophobic gas molecules in the solution. Here, in this work, ultrasonic technology was applied to generate stable and large amount of nanobubbles in pure water to promote hydrate formation kinetics. The particle size distribution of the nanobubbles was following the log-normal distribution, with a concentration of ∼109 mL–1 and a diameter concentrated in 100–120 nm. The concentration of the nanobubbles increased with the ultrasonic duration and power. Notably, the concentrations of nanobubbles produced by hydrate decomposition were slightly higher with the bubble size concentrated around 200 nm. The effect of nanobubbles on the induction time of hydrate formation was further analyzed by forming from the nanobubble solution with different concentrations and particle size distributions. Hydrate formation induction time was reduced by up to 61.13%. We further analyzed the mechanism of the nanobubble dominant hydrate memory effect. The results proved ultrasound as an approach to enhance the solubility of gases in water and thus promote hydrate formation kinetics, providing evidence for the dominant role of nanobubbles in the memory effect.