Decontamination of waste semi-synthetic or synthetic mineral oils comprises treatment with glycol, chelating agents, and barium hydroxide before ultimate fractional distillation and possible decoloration treatment

摘要

The stages of treatment of the contaminated oil enables operation of the fractional distillation stage at a lower temperature and avoids the cracking of any polymers present. The decontamination of waste lubricating oils comprising mineral oils, semi-synthetic and synthetic oils comprises: (a) the addition of 1-2 wt.% glycol to the oil in a container, heating to 60 deg C, stirring then cooling and separating to obtain an aqueous phase containing glycol and phenolic products, suspended material, silicone oil residues and anti-foam agents; (b) withdrawal of the aqueous phase and addition of a chelating agent to the oily phase in stoichiometric amount, or above, relative to the compounds to eliminate, in a soda solution at pH not exceeding 7 (preferably 6) at 60-80 deg C, with stirring for 1 hour, and centrifugation to separate off the oily phase from the solution containing chelated heavy metals; (c) the stoichiometric addition of a coagulant to the oily phase to separate iron, and separation of the aqueous phase obtained; (d) the stoichiometric addition of barium hydroxide to the oily phase in suspension or solution to precipitate sulfate and phosphate ions as barium phosphate and sulfate and separation by centrifugation; and (e) fractional distillation to recover the base constituents of the oils, and optionally decoloration of the products obtained.