A comparative study on the efficiency of polar and non-polar solvents in oil sludge recovery using solvent extraction.

Oily sludge is a stable emulsion of water in oil, containing solid particles, oily hydrocarbons, and metals with different compositions, which is greatly hazardous to the environment; as a consequence, they must be removed or recovered. Recovery methods are usually preferable because of the possibility of valuable oily hydrocarbons recovery as well as environmental protection. Liquid extraction is one of the most effective methods of oily sludge recovery. In this research, hydrocarbon recoveries from oily sludge using liquid extraction with methyl ethyl ketone (MEK) and toluene as polar and non-polar solvents have been studied and compared to each other. Different parameters will affect the quality of extraction process, among which the temperature, time, and solvent to sludge ratio are the most important ones. Response surface methodology was used as a method of experimental design to find the optimum conditions for obtaining maximum recovery. Then, the sludge recovery efficiencies under the optimum conditions for MEK and toluene were determined by gas chromatography and compared to each other. The results showed 30.41 and 37.24% hydrocarbon recovery for MEK and toluene respectively. Since the major composition of the sludge consisted of non-polar components, therefore, non-polar solvent (MEK) shows better efficiency. The optimum conditions of the studies were 20 °C, 19 min, and 6.4/4.2 for MEK and 55 °C, 17 min, and 3.6/3.6 for toluene.