Hydrodynamics and mass transfer characteristics of a single microbubble in liquids with different properties

Microbubbles have great potential in enhancing gas-to-liquid mass transfer. However, there is still a lack of systematic research on how the liquid properties affect the hydrodynamics and mass transfer characteristics of a single microbubble. In this work, the diameter, velocity, and mass transfer of a single microbubble in liquids with different properties were analyzed by using high-speed photograph technology. It was found that the rise velocity was minimally affected by the surfactant but decreased with the increase of liquid viscosity. A new velocity correlation was developed to predict the rise velocities of microbubbles, with deviations within 20%. The addition of surfactants and increasing liquid viscosity both reduce the mass transfer coefficient (k_L) compared to ultrapure water. Conversely, k_L increased by 1.3 to 4.1 times as the reactant concentration increased in chemical absorption. This study provides meaningful data to understand the hydrodynamic behaviors and mass transfer characteristics of microbubbles.