Separation of oil from oily sludge by freezing and thawing

This communication reports for the first time the feasibility of employing freeze/thaw method to separate oil from an oily sludge. The freeze/thawed sludge comprises three distinct layers, an oil layer at the top, a sediment layer at the bottom and a water layer locating in between, whose compositions were identified with the help of GC–MS. Freezing and thawing can separate over 50% of its oil content. However, ultra-fast freezing is not beneficial for oil separation.