Effect of jet cavitation on oil recovery from oily sludge

•Hydrodynamic cavitation improves the oil recovery efficiency of oily sludge.•Sedimentation performance of oily sludge is improved and average particle size is reduced.•Asphaltenes and resins are important components that hinder oil desorption from oily sludge.•Hydrodynamic cavitation improves the recovery efficiency of oil components.•Reveal the mechanism of hydrodynamic cavitation to disintegrate oily sludge. Jet cavitation method was proposed to treat oily sludge to improve oil recovery. The key components affecting the oil desorption efficiency were analyzed by TLC-FID (Thin-layer chromatography and flame ionization detection) method and FT-IR(Fourier-transform infrared spectroscopy), and the mechanism of oil recovery from oily sludge enhanced by jet cavitation was revealed. The results show that when the inlet pressure is 12 MPa, the temperature is 35 °C, the solid concentration is 25 %, and the hydraulic retention time for oily sludge is 4 s, the maximum oil recovery rate is 82.3 %, which is much higher than that after ultrasonic cavitation. After jet cavitation, the sedimentation performance of the oily sludge was improved, and the average particle size was reduced. Asphaltenes and resins are the main components affecting oil desorption. Heteroatoms such as N, S, and O form stable hydrogen bonds with the surface of solid particles, which impede the oil desorption process. The mechanical effect such as micro-jet shock waves and shear forces generated by jet cavitation could disrupt the hydrogen bonds, promoting the reformation of hydrogen bonds between water and solid particles, leading to the separation of oil from the surface of solid particles.