Performance of reverse osmosis membranes in the separation of supercritical CO2 and essential oils

The present work studied the performance of three commercial reverse osmosis membranes: SG, CG and AG, supplied by Osmonics, USA, regarding the permeability to supercritical CO2 and the retention of lemongrass, orange and nutmeg essential oils at 12 MPa and 40 °C. The oil retention and the membrane permeability to CO2 were studied as a function of feed concentration and of the transmembrane pressure difference (ΔP). It was observed that the CO2 flux was linearly dependent on ΔP. The essential oil retention reduced as ΔP was increased, but showed no alterations with changes in oil feed concentration. The SG membrane exhibited the best performance, with up to 90% essential oil retention. All the membranes tested presented good mechanical resistance to the severe pressure conditions applied. Promising results were achieved regarding the possibility of use of commercial reverse osmosis membranes for the separation of lemongrass, orange and nutmeg essential oils from supercritical CO2 in a hybrid extraction and separation process.