To develop a simple technique for separating submicron particles, aqueous suspensions of silica particle mixtures were ultrasonically atomized and the behavior of particle separation was examined under various conditions. Ultrasonic atomization brought silica particles of a specific size, 100 nm into fog from a suspension containing a mixture of silica particle of 100 and 300 nm. Most of the fog was successfully recovered with liquid nitrogen coldtrap, and the recovery percent of particles reached more than 90 %. In the recovered suspension, enrichment of 100 nm particle was observed and dilution of 300 nm was attained. The result indicated selective transfer of 100 nm silica particle into the fog and rejection of 300 nm silica particle. Interestingly, the separation disappeared after degassing the feedstock. Also, when the gas dissolving in the suspension was changed from air to argon, the rejection of 300 nm silica particle was decreased. The separation, selective transfer of silica particle depending on the size was significantly affected by the amount of dissolving gas as well as type of the gas. The result clearly indicates a strong influence of cavitation on the separation mechanism.
