Desorption characteristic of oil from sludge surfaces under low-frequency ultrasound

Abstract

Oil and solids in oily sludge have complex composition and exhibit strong interaction, which both make difficult the oil removal. In this paper, experiments focused on oil/solid property analysis and oil removal have been conducted to determine desorption characteristics of oily sludge in low-frequency ultrasonic fields. Polar components have a high fraction of heteroatoms that form strong van der Waals forces and hydrogen bonds with solid particles. In comparison to nonpolar, polar components were found to be less desorbed from solid surfaces in the ultrasonic field. Metals in kaolinite had strong electrostatic interactions with carboxylic acid in oil. In addition, porous structure of kaolinite increased the re-adsorption probability of oil. In comparison to quartzite, kaolinite showed lower oil removal efficiency. Therefore, higher acoustic intensity with shorter treatment time was found to be effective for oily sludge with high content of polar components and kaolinite at constant energy.