The report gives results of a study of the technical feasibility of using critical fluids (condensed gases or supercritical fluids) as extracting solvents to treat oily industrial wastes. The process has the potential for recovering by-product values from the wastes to offset the operating cost of the treatment. Wastes studied at bench-scale were: oily mill scale from the steel industry, oil-laden bleaching clays from specialty- and vegetable-oil decolorization and clarification, and lubricating oil/water waste emulsions from metal working in the aluminum and steel industries. Steel mill scales were successfully de-oiled to below 0.1 wt%, using condensed-gas hydrocarbon and halocarbon solvents for extraction, the recovered oil met acceptable fuel specifications, and credits were sufficient to permit an attractive payout on the investment in treatment equipment. Spent bleaching clays, used to process silicone oils and vegetable (soybean) oil, were treated with hydrocarbon and halocarbon solvents: most of the oil (up to 100%) were recovered, an analyzed silicone oil met product specifications, and the cost of a critical-fluid-based extraction plant of representative capacity would pay out favorably due to credits for recovered oil. Waste lubricating oil emulsions from aluminum-can forming and combined steel mill operations were de-oiled using CO2 as a solvent near its critical point.

"April 1985." "EPA/600/2-85/045." Microfiche.