Caption title. At head of title: Project summary. Distributed to depository libraries in microfiche. "May 1985." "EPA/600-S2-85-045."

"The objective of this program was to determine the technical feasibility of the use of 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 were: oily mill scale from the steel industry, oil-laden bleaching clays from specialty oil and vegetable oil decolorization and clarification, and lube-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. The iron value of the de-oiled scale and the fuel value of the oil would provide sufficient credits to permit an attractive payout on the investment in treating 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%) was recovered. An analyzed silicone oil met product specifications. The cost of a critical-fluid-based extraction plant of representative capacity would pay out favorably due to credits for recovered oil. Waste lube oil emulsions from aluminum-can forming and combined steel mill operations were de-oiled using CO2 as a solvent near its critical point."