The ultrasonic technique has been demonstrated to be a promising method for the disposal of hazardous oily sludge. However

the separation of oil from the surfaces of the solid particles is still difficult due to the strong interaction between the oil and solid particle. In this study

three types of surfactants were used to assist the ultrasonic treatment of oily sludge. The oil component

surface composition

and structure of the solid particle were determined. The results showed that different surfactants had different oil removal abilities. In the three surfactant-assisted sonication systems

the oil removal rate increased during the starting reaction period and then decreased with longer sonication time. The results of four components analysis suggested that surfactant easy to be ionized in water posed a better removal effect on resins

while the amphiphilic surfactant preferred saturates

aromatics and asphaltenes. The morphology analysis indicated that particle size was shattered into smaller ones by the ultrasonic process

and the wettability of the solid surface also changed during this treatment. The characterization of the oil component and solid particle during surfactant-assisted ultrasonication treatment will help to better understand the separation of oil from oily sludge and improve the oil recovery efficiency from oily sludge.