2015 Volume 48 Issue 7 Pages 523-527
It is not clear how the gas holdup of a solution containing microbubbles changes with the use of different surface-active agent coating microbubbles. This study investigated how the gas holdup of an aqueous solution containing microbubbles relates to the dynamic surface tension of the solution and the surface charge of surface-active agents coating the microbubbles. Microbubbles were generated using a static mixer. When a non-ionic organic chemical was used as the surface-active agent, the gas holdup increased with a decrease in dynamic surface tension. A similar trend was observed for sodium alkyl sulfate, alkyl trimethylammonium chloride, and polyoxyethylene dodecyl ether. However, the gas holdup in aqueous solutions of an ionic surfactant was more sensitive to the change in the dynamic surface tension than that of nonionic surfactant. The effect of electric charge on a surfactant on the gas holdup was examined using an amphoteric surfactant, i.e. N-lauryl β-aminopropionic acid. Its chemical structure changes with solution pH, resulting in a change in ionicity. The gas holdup was a minimum at the isoelectric point of the amphoteric surfactant (pH 4.0). Thus, this study proved that gas holdup depends on the dynamic surface tension of the solution and the surface charge of microbubbles.
