Mass transfer and gas–liquid interface properties of single CO2 bubbles rising in tap water

•Mass transfer approximated by theories for mobile and immobile gas–liquid interface.•Changing bubble properties and mass transfer observed during bubble ascent.•Initial bubble diameter and velocity found to influence transition to immobile bubble surface.

To improve the mass transfer efficiency in many industrial applications better understanding of the mass transfer rate is required. High speed images of single CO2 bubbles rising in tap water were analysed to investigate the relationship between the mass transfer and properties of single bubbles. Transition to a lower mass transfer rate was shown to correspond with the transition from a mobile to an immobile bubble surface. This was indicated by the change in bubble rise velocity, bubble rise path and bubble shape. The presence of surfactants in untreated tap water appear to effect the transition point, particularly for bubbles with a smaller initial diameter and lower rise velocity.