Surfactants and Microemulsions in Supercritical Fluids

A potrat, new solvoit is evolving— a supo-oritical carbon dioxide micromulsion. A C02-based microemulsion is especially attractive since CO2 is very abundant, relatively inexpensive, and environmentally benign at this scale of use.. plications of this system to cleaning processes appear very promising. 

The technique may be viewed as an alternative to the addition of cosolvents or modifiers (sometimes termed entrainers) that are commonly used in supercritical fluid technology to enhance the polarity of the fluid. For cleaning processes, however, these cosolvents may be toxic or detrimental in various ways to the substrate. In addition, these modifiers are usually more difBcult to separate downstream from the process due to their higfi volatility. In contrast, surfactants typically have very low volatility and thus into act to a much lesser d ree with the substrate. Fuithomore, they often dramatically improve the solubility of polar species, well beyond that of simple modifiers. 

Because of the obvious importance of a C02-based system, there has been much work in the area of developing this type of supercritical fluid microemulsion.On the sur ce, the strat- y is simple and interesting parallels can be made to the first soap or surfactants used in water thousands of years ago. For instance, with 

The application of supercritical microemulsions to cleaning is a new area and there have been no published results to date applying these systems to cleaning operations but the combination of surfactants with fluids would be a natural choice for many systems. The information in this chapter is to be used as a guide to the development of cleaning applications based upon supercritical fluid-based microemulsions. 

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