Used lubricating oil is a complex mixture of recoverable base
oil, polymeric additives, water, light hydrocarbons, metals and carbonaceous
particles. A good extraction–flocculation solvent should
dissolve base oil and precipitate other substances to form sludge.
1-butanol, petroleum-ether and 1-hexanol behave as efficient
extraction–flocculation solvents for used oil due to their good solubility
parameters for base oil and good antisolvent effect for nonpolar
or slightly polar polymeric additives, metals and
carbonaceous particles