Measurement of the Zeta Potential of Gas Bubbles in Aqueous Solutions by Microelectrophoresis Method

An electrophoresis technique is used to measure the zeta potential of fine bubbles dispersed in aqueous solutions. An improved apparatus of a microelectrophoretic type is developed for the bubble zeta potential measurements. Electrodes for generating either oxygen or hydrogen gas bubbles are designed in such a manner that micrometer-sized bubbles can be produced over the entire cross section of the electrophoresis cell. Consequently, a bubble can be easily selected at the so-called stationary plane, where bubble electrophoresis measurements are conducted. Furthermore, a motorized vertical translation stage controlled by computer is implemented. When bubbles rise due to buoyancy, the electrophoresis cell mounted on the translation stage is made to move downward so that the bubbles can be kept in the field of view of the microscope. As a result, the movement of bubbles with diameters up to 80 μm can be readily followed and bubble trajectory can be traced for 4–8 s. Effects of water chemistry—pH concentration and type of metal ions—on the bubble zeta potential were studied. The experimental results generated for bubble zeta potential are consistent with data available in the literature.