Reclamation of Base Oil from Depleted Engine Oil by Solvent Extraction Process: An Insightful Review

Abstract

Lubricating oils are viscous hydrocarbon liquids obtained from crude oil, are essential for lubricating the moving parts of various machines. Used lubricants are classified as hazardous waste due to their elevated concentrations of environmentally dangerous organic substances, including Polychlorinated Biphenyl (PCBs), Polycyclic Aromatic Hydrocarbons (PAHs), and heavy metals. These contaminants, originating from the integrity of lubricating oil, are significantly affected by wear and tear, additive breakdown, thermal cracking, and oxidation during their operational life, necessitating their replacement. Direct disposal of this used oil into the environment causes substantial pollution. Incineration of used oil generates significant ash and carcinogenic byproducts, further contributing to environmental contamination. Recycling lubricants, through the application of physical-chemical processes, enables the recovery of base oil, a valuable reusable raw material in lubricant production. Numerous studies have investigated oil reuse and used oil re-refining. Research consistently validates solvent extraction, frequently enhanced using adsorption, as a more performant and efficacious technique for recycling used lubricating oil. The present review offers a thorough analysis of the solvent extraction procedure for this application.