Ultrasound Emulsification: Effect of Additives on Dispersed Phase Volume and Droplet Size

Ultrasonic emulsification of oil and water was carried out to observe the effect of addition of a minimal amount of surfactant. The effect of ultrasound irradiation time, power, and physicochemical properties of oil on the dispersed phase volume and dispersed phase droplet size has been studied. The increase in the irradiation time increases the dispersed phase volume, while it decreases the dispersed phase droplets size. With an increase in the ultrasonic irradiation power, there is an increase in the fraction of volume of the dispersed phase, while the droplet size of the dispersed phase decreases over the same irradiation time. The fractional volume of the dispersed phase is higher for the case of the groundnut oil–water system, while it is low for the paraffin (heavy) oil–water system. The droplet size of soyabean oil dispersed in water is found to be small, while that of paraffin (heavy) oil is found to be large. These variations could be explained on the basis of varying physicochemical properties of the system, i.e., viscosity of oil and the interfacial tension. During the ultrasonic emulsification, a coalescence phenomenon which is relatively weak has also been observed, which can be attributed to the collision of small droplets when the droplet concentration increases (higher dispersed phase hold-up) and the acoustic streaming strength is higher.