An environmentally friendly process for the regeneration of used oils

We describe in this paper a process of filtration of highly viscous liquids assisted by pressurized CO2, and we present preliminary results obtained during the treatment of motor oils (two mineral oils and one used motor oil). Filtration and concentration runs are commentated in terms of permeate flux enhancement and metal retention. The behavior of these fluids during filtration exhibits significant discrepancies from the one observed with previously investigated model compounds. The permeate flux improvement is about 400% for mineral oils and about 200% for the used motor oil (P-CO2 = 15 Mfa, Delta P = 1 MPa, T = 353 K, cutoff of the membrane: 356 kDa). The presence of many pollutants can explain the lower improvement in the latter case. The performance of the membrane with regard to the retention of metals is very satisfactory: in the case of zinc and copper, the separation is higher than 99.5%, The 32 h concentration run carried out: at 393 K made it possible to regenerate 96% in mass of the used oil and to confine the majority of the metals in a black gum extremely viscous.