Oil removal from spent bleaching earth of vegetable oil refinery plant using supercritical carbon dioxide

The oil in the spent bleaching earth (SBE) matrix was successfully removed by applying the supercritical carbon dioxide (SCCO₂) extraction technique in a semi-continuous flow-type system. The SCCO₂ extraction process was conducted at 40-80 °C and 20-30 MPa with extraction time of ∼180 min. The color of SBE matrix changes from the dark to dark-pale color after the SCCO₂ extraction treatment exhibiting the substances including oil in the SBE matrix were successfully removed. The extracted oil yield was around 95% when the SCCO₂ extraction process was performed at 40 °C and 30 MPa with 10% ethanol addition as a co-solvent. The GC analysis showed that the prominent fatty acid constituents in the extracted oil are palmitic and oleic acids, furthermore it can be fed as a feedstock to produce biodiesel fuel. Next, it can be proposed that SCCO₂ extraction system is a viable way to extract oil from the SBE matrix.