Method for removing polynuclear aromatics from used lubricating oils

A method for removing polynuclear aromatics from a used lubricating oil which comprises passing the lubricating oil through a filter system containing a hollow solid composite comprising a thermoplastic binder and activated carbon, wherein the composite is formed by the steps comprising

• (a) providing a quantity of the thermoplastic binder in the form of particles having diameters between about 0.1 and about 250 micrometers;
• (b) providing a quantity of activated carbon having a softening temperature substantially greater than the softening temperature of the thermoplastic binder, the activated carbon being in the form of particles having diameters between about 0.1 and about 3,000 micrometers;
• (c) combining the particles from (a) and (b) to form a substantially uniform mixture wherein from about 2 to about 25 wt. % of the thermoplastic binder and about 40 to about 75 wt. % of the activated carbon are present in the mixture;
• (d) extruding the substantially uniform mixture of (c) into a die;
• (e) heating the substantially uniform mixture from (d) to a temperature substantially above the softening temperature of the thermoplastic binder but to a temperature less than the softening temperature of the activated carbon;
• (f) applying sufficient back pressure, from outside the die, to the heated mixture from (e) within the die to convert the heated mixture into a substantially homogeneous composite;
• (g) rapidly cooling the composite from (f) to a temperature below the softening point of the thermoplastic binder to produce a cooled composite;
• and
• (h) extruding the cooled composite from the die as an extruded hollow solid composite.