Filtration bleaching clay removal

Used engine oils can be reused. Sometimes, all that is needed is removal of particles by filtration or centrifugation. In others, it may be necessary to remove volatile acids and water by heating, followed by treatment with sulfuric acid, then lime, and, sometimes, bleaching clay. A final distillation under vacuum completes the rerefining.63 Another system uses propane at ambient temperature in a continuous process.64 The additives and impurities precipitate and settle out, after which the propane is flashed off and the... 

Wear eye protection, butyl rubber gloves,10 and laboratory coat. Cover spill with a 1 1 1 mixture by weight of sodium carbonate or calcium carbonate, clay cat litter (bentonite), and sand.11 Scoop the solid into a container, transport to the fume hood, and slowly add to water allowing 20 mL of water for each 1 g of hydrazine. Remove the clay and sand by filtration. For each 1 g of hydrazine, place 120 mL (about 25% excess) of household laundry bleach (containing 5.25% sodium hypochlorite) into a three-necked, round-bottom flask equipped with a stirrer, thermometer, and dropping funnel. Add the aqueous hydrazine dropwise to the stirred hypochlorite solution at such a rate that the temperature is maintained at 45-50°C. The addition takes about 1 hour. Stirring is continued overnight (at least 12 hours). The reaction mixture can be flushed down the drain with at least 50 times its volume of water.12 13... 

Next, the refined oil is bleached (reacted with activated clays, diatomaceous earths, or recoverable silicas) to adsorb phospholipids, color pigments, soaps, peroxides, aldehydes, and other polar compounds, and is recovered by filtration. Spent bleaching earths in the filter cake contain pigments, occasional residual pesticides, aldehydes, and other compounds removed from the oil, and they often present disposal problems. 

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