| Summary: | 碩士 === 國立交通大學 === 應用化學系 === 90 === Reverse micelle formation is presented in this study as a strategy for improving the extraction of polar species with supercritical carbon dioxide (SC CO2). Only mediocre solubilities of almost all commercial surfactants in neat SC CO2 have been reported in the literature. However, adding organic modifiers to SC CO2 can increase the surfactant solubilities. We measured the solubilities of seven commercially available ionic surfactants in the modifier-containing SC CO2. The solubilities of DDAB (didodecyldimethylammonium bromide) and AOT (sodium bis-2-ethylhexyl sulfosuccinate) exceeded 18000 mg/L at 225bar while the concentration of ethanol was 20% v/v. The high surfactant solubilities ensured formation of reverse micelle in SC CO2 for dissolving hydrophilic compounds. We successfully used AOT and DDAB to extract two ionic dyes (methylene blue & methyl orange), but failed to extract protein molecules - cytochrome c. In addition, a nonionic surfactant, i.e. tetraethylene glycol n-lauryl ether, was demonstrated to be able to extract the ionic dyes. Due to the relatively lower polarity of this nonionic surfactant and thus higher solubility in SC CO2, the extraction could be accomplished under relatively lower applied pressure and modifier concentration.
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