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Session 2213

Supercritical Fluid Extraction in the Undergraduate Laboratory l Rebecca K, Toghiani, Hossein Toghiani, and Jay Jones Department of Chemical Engineering Mississippi State University P.O. Box 9595 Mississippi State, MS 39762

Introduction

Thermodynamics experiments are often an overlooked component in the chemical engineering undergraduate laboratory curriculum. This is in part due to the expense of necessary equipment and also due to the length of time and degree of precision required to perform experiments to demonstrate textbook principles. At Missippi State University, a major portion of the renovation effort over the past six years has been the development and incorporation of experiments focusing on emerging technologies such as supercritical fluid extraction, Students can best be exposed to these technologies in a laboratory setting. Supercritical fluid extraction requires the use of phase equilibrium principles and thus, experiments focusing on this technology provide exposure both to its use as an emerging separations technology and to the underlying thermodynamic relationships.

Supercritical fluid extraction technology has been developing for the past fifteen years and while commercial applications in the U.S. are few and limited in scope, opportunities are ever expanding. In recent years, use of this technology in the environmental restoration sector, the food and drug sector, as well as the chemical industry have been discussed in the literature [Johnston, 1989; Taylor, 1995]. Supercritical fluid extraction does not give rise to secondary waste streams in environmental applications. This is in contrast to incineration or leaching, where monitoring and secondary disposal costs may contribute significantly to the overall process cost. The use of supercritical fluids in the food and drug industry arises from the need to separate thermally labile materials from complex mixtures. The use of supercritical carbon dioxide, in particular, allows the necessary separation to be conducted at much lower temperatures than would be realized in other separation processes.

The opportunities for laboratory experiments are diverse in nature and differ in their degree of difficulty and implementation. Solute volubility in supercritical solvents is crucial to the success of this technology in an industrial application, The measurement of volubility for various solutes, typically low volatility solids and liquids, in supercritical fluids has been reported in the literature [McHugh and Paulaitis, 1980; Chang and Morrell, 1984; Kurnik et al,, 1981]. An understanding of the various factors which affect this volubility can be gained by the undergraduate student through properly designed experiments.

Background and Theory

Supercritical fluid extraction exploits the unique behavior displayed by a material at a temperature and pressure slightly above its critical point. At a temperature slightly above the critical point of the solvent, the properties of the fluid vary smoothly from liquid-like behavior to gas-like behavior without the abrupt change in 1 Present Address: PPG Industries, Inc., PO, Box 1000, Lake Charles, LA 70602

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Jones, J., & Toghiani, R. K., & Toghiani, H. (1996, June), Supercritical Fluid Extraction In The Undergraduate Laboratory Paper presented at 1996 Annual Conference, Washington, District of Columbia. 10.18260/1-2--6305