ABSTRACT
A supercritical state is achieved when the temperature and the pressure of a substance are raised over its critical values. A supercritical fl uid has characteristics of both gases and liquids. Compared with liquid solvents, supercritical fl uids have several major advantages: (1) the dissolving power of supercritical fl uids depends on their density, which is highly adjustable by changing the pressure or temperature; (2) supercritical fl uids have a higher diffusion coeffi cient and lower viscosity and surface tension than liquid solvents, leading to more favorable mass transfer (Wang and Weller, 2006).
