Micro-mixing in flow-type process for supercritical CO2 extraction of ferulic acid and gallic acid from aqueous solution

Abstract

Micro-mixing technique in a flow-type process was applied for supercritical CO2 extraction of ferulic acid and gallic acid from aqueous solutions. Four principles of micro-mixing techniques such as swirl-mixing, cross-junction, T-junction, and cross-flow T-junction were used for the supercritical extractions. Swirl-mixer provides the best micro-mixing technique in terms of high extraction efficiency and high stability of the length of liquid slug formation. Using swirl-mixing technique, gallic acid was slightly extracted from single-component aqueous solution and its extraction efficiency was lower than ferulic acid. However, extraction of gallic acid from an aqueous solution containing both gallic and ferulic acids was undetectable since it acts as the promoter to facilitate the extraction of ferulic acid into CO2 extracts. At 39.5 °C, 14.3 MPa and using swirl-mixing technique, the extraction efficiency of ferulic acid from the aqueous solution was 10.5 % and it was further increased to 11.6 % with addition of 2.0 mol. % of ethanol as co-solvent. These results show the applicability of micro-mixing for supercritical CO2 extraction of highly polar compounds from aqueous solution.