Electrical potential of microbubble generated by shear flow in pipe with slits

Microbubbles are very small bubbles with a diameter of 50μm or less. The important characteristics of microbubbles are their large specific area and small buoyancy, and therefore effective dissolution of gas phase and high adsorption rate are expected. The utilization of microbubbles is useful in improving water environments. Research efforts at a number of institutions have been devoted to the development of microbubble generators. However, in previous microbubble generation devices, complex mechanisms and a high power supply have been required. In this study, a compact and low-power microbubble generator has been developed. Microbubbles were generated by inducing local shear stress in the flow of water through a pipe with slits. Three types of model (slit angle θ=30∘, 60∘, and 90∘) were used in order to investigate the effect of slit angle on the purification technique. The proposed microbubble generator with the slit angle θ=60∘ showed superior performance for the water purification technique in comparison with the other two models. It was confirmed that microbubble generation was affected by slit angle. Also, in this study, we investigated the electrical property of the gas-water interface, and the ζ-potential of microbubbles was measured by electrophoresis. The results of the floatation experiments were affected by the ζ-potential of the microbubbles.