Electric Charge of Micro and Nano Bubbles by Interferometric Laser Imaging Technique

In this paper we investigated ζ potential of microbubbles by electrophoresis method. The individual bubble diameter measured by means of interferometric laser imaging technique. The experimental results showed that different methods for producing microbubbles which were pressurizing dissolution method, swiveling gas-liquid two-phase flow method and electrolysis method did not make difference in the resultant values of ζ potential. In order to understand the mechanism of charging characteristic of microbubbles, we changed the pH of the deionized water and added alcohols or a surfactant to the deionized water. The results showed that the absolute value of the ζ potential increased when the pH increased. ζ potential was drastically changed by alcohols and surfactant which easily absorbed on the air-water interface. Moreover, simultaneous measurement of ζ potential and diameter of shriking microbubble resulted that bubbles shose diameter is less than 3 μm were observed by using Mie theory.