Two separation processes have been developed to remove contaminants (cutting oil with trace phosphorus additive) from high-speed steel grinding sludge. One process uses an aqueous surfactant washing technique, and the second process uses supercritical carbon dioxide (SCCO2) extraction. Our bench scale aqueous washings have shown that the required phosphorus removal is easily obtained, but a sufficient oil removal is more difficult. The experimental results also indicate a strong dependence of the aqueous washing efficiency on the choice of a suitable surfactant. A mass transfer model is used to simulate a semi-continuous washing process. SCCO2 extraction at 80 degrees C and 340 atm shows that approximately 80% of the oil can be removed from the sludge during a 60-minute process to produce a batch of recyclable steel, and that the phosphorus removal also reaches the required level. A linear desorption model is used to describe the irreversible desorption of oil from the solid phase into the CO2 phase and the simulated results agree very well with the experimental data.