Effect of cosurfactant on water solubilization in supercritical carbon dioxide microemulsions

Water solubilization in supercritical carbon dioxide (SC CO2) microemulsions prepared using F-AOT (fluorinated-sodium bis (2-ethylhexyl) sulfosuccinate) analogues has been compared in the presence of cosurfactant n-butanol. At pressure 44 MPa and 35 °C, the addition of n-butanol to di-HCF4 (sodium bis(1H,1H,5H, octafluoropentyl) sulfosuccinate)/SC CO2 microemulsion enhanced the water solubilization from W0 = 30 to 45. Increasing the amount of cosurfactant further enhanced the water solubilization. At R = 10, a maximum amount of water W0 = 49 was dissolved in di-HCF4/SC CO2 system which is highest reported so far in SC CO2 microemulsions. W0 and R represent the molar ratio of water- and n-butanol-to-surfactant, respectively. F-AOT/SC CO2 microemulsions were characterized by pressure dependent water solubilization phase diagram and high pressure UV absorption spectroscopy.