Emulsification and Demulsification Processes in Liquid–Liquid System by Electrostatic Atomization Technique

Abstract

A new electrical emulsification and demulsification apparatus using an electrostatic atomization technique was developed, and the investigation of both processes in a liquid-liquid system was conducted. First, fine water droplets were generated in silicone oil using a nozzle electrode with ac high voltage, and then, a stable water-in-oil (W/O) emulsion was produced without surfactants. The mode of electrostatic atomization and the trajectory of the fine droplets' flow were observed. The diameter of fine droplets and their distributions were measured as a function of the applied voltage and its frequency. Experiments indicated that electrohydrodynamic (EHD) induced liquid flow with water droplets played an important role in the formation of the emulsion. Next, the demulsification of W/O emulsion was carried out by two injections of oppositely charged water droplets, using the method of electrostatic atomization. The test liquid, which was prepared by the electrostatic atomization technique, was maintained in a state of emulsion for a longer time if no electric field was applied. When the positive- and negative-charged droplets were injected into the test liquid, the emulsion, with a dull color, gradually became transparent as time elapsed. The aggregated droplets fell down due to gravity and the EHD flow effect, resulting in the separation of water and oil. It was found that two injections of oppositely charged water droplets were effective for resolving the emulsion.