Interfacial tension and equilibrium contact angle of lipids on polished glass in supercritical CO2

Better understanding of the wettability behavior of lipids on different surfaces is needed for supercritical CO2 (SC-CO2) fractionation of lipid mixtures using packed columns. This study aimed to determine the interfacial tension (IFT) and equilibrium contact angle (CA(eq)) of oleic acid (OA) and canola oil (CO) on polished glass in SC-N-2 and SC-CO2 environments at 40, 60, 80 degrees C and 16, 20, 24 MPa. IFT and CA(eq) were determined using pendant drop and height/width methods, respectively. IFT values decreased with pressure due to the increase in CO2 density. CA(eq) values of lipids in SC-CO2 exhibited three different patterns: complete, complete-partial, and partial wettability at different conditions due to the solubility of SC-CO2 in lipid and vice versa, and formation of thin vapour film on glass surface. Novel phenomena of formation of satellite droplets, SC fluid cavity, bouncing and sliding of CO droplet on glass in SC-CO2 were observed.