Solvent selection in microwave assisted extraction of castor oil

Abstract

Castor oil has various uses in the field of cosmetics, plastics, manufacturing of biodiesel, lubricants and medicine. The use of microwave-Assisted extraction (MAE) of oils from plant materials has shown tremendous research interest and potential to overcome long extraction time and high solvent volume. This study aims to evaluate suitable solvents for MAE of castor oil because not all solvent molecules have the ability to absorb microwave energy for heating, and consequently effective extraction. The MAE operating conditions were fixed at 230 W power intensity, solvent to feed ratio (S/F) of 20 : 1 and 10 min extraction time using petroleum ether, water, hexane and ethanol. The castor oil was characterised according to yield and dielectric properties. Results showed that the mix of hexane-ethanol (5 % ethanol) was found to be the most stable and effective solvent for MAE of castor oil with 36 % yield. The characteristics of oil are comparable to that of conventional soxhlet method. The dielectric constant of hexane shows some alteration when small amount of ethanol was used as modifier to allow extraction to occur.