Solvent efficiency for oil extraction from spent bleaching clay

Various alcohols and hydrocarbons were used as solvents to extract the residual oil in spent bleaching clay from palm oil refining. The content of oil and minor components in the spent clay was >40% by weight. The efficiencies of extraction by the polar alcohols, except for methanol, were higher but with a slower initial rate than the nonpolar hydrocarbons. The free fatty acids contents, the Totox values (anisidine value+2 x peroxide value), and the color of the alcohol-extracted oil were also higher than that by the hydrocarbons resulting in poorer quality oils. All the extracted oils, irrespective of the solvent used, have poorer quality than crude palm oil. However, for regeneration of the residual spent clay, the polar alcohols should be more suitable as more of the impurities are removed.