Phase behavior of supercritical CO2 microemulsion with food-grade surfactant AOT

Phase behavior of scCO2 microemulsion formed with food grade surfactant sodium bis-(2-ethylhexyl) sulfosuccinate (AOT) was studied. Critical microemulsion concentration (cμc) was deduced from the dependence of pressure of cloud points on the concentration of surfactant AOT at constant temperature and water concentration. The results show that there are transition points on the cloud point curve in a very narrow range of concentration of surfactant AOT. The transition points were changed with the temperature and water concentration. These phenomena show that lower temperature is suitable to forming microemulsion droplet and the microemulsion with high water concentration is likely to absorb more surfactants to structure the interface.