The shrinkage of microbubbles that are less than about 50 µm in diameter is an established phenomenon that results from relatively high surface tension.  It has also been shown recently that hydroxyl ions have an extremely strong affinity for gas–water interfaces including bubble surfaces.  A theoretical model is proposed that predicts bulk nanobubble stability in water based on a force balance that results naturally from the shrinkage of microbubbles.  This model was designed to test the hypothesis that the increasing surface tension of a shrinking microbubble can ultimately be balanced by the repulsion of hydroxyl ions that initially adsorb onto the microbubble surface prior to shrinkage.  No special assumptions are required in the present model other than the recently reported strong affinity of hydroxyl ions to gas/water interfaces.  The Debye-Hückel theory was used to determine the number of ions on the microbubble surface prior to shrinkage.  The results of this model predict a stable balance between the surface tension and the electrostatic repulsion of hydroxyl ions for nanobubble diameters less than 1100 nm in pure water at neutral pH.  The predicted maximum in nanobubble size, as well as other results, are shown to be consistent with experimental findings.  Potential applications for nanobubbles based on their ability to bind to hydrophobic and/or positively charged surfaces will also be discussed.

Hydroxyl ion stabilization of bulk nanobubbles that naturally results from microbubble shrinkage

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.