Gibbs adsorption and the compressibility equation
- Department of Chemical Engineering, The Johns Hopkins University, Baltimore, Maryland 21218 (United States)
A new approach for deriving the equation of state is developed. It is shown that the integral in the compressibility equation is identical to the isotherm for Gibbs adsorption in radial coordinates. The Henry, Langmuir, and Frumkin adsorption isotherms are converted into equations of state. It is shown that using Henry`s law gives an expression for the second virial coefficient that is identical to the result from statistical mechanics. Using the Langmuir isotherm leads to a new analytic expression for the hard-sphere equation of state which can be explicit in either pressure or density. The Frumkin isotherm results in a new equation of state for the square-well potential fluid. Conversely, new adsorption isotherms can be derived from equations of state using the compressibility equation. It is shown that the van der Waals equation gives an adsorption isotherm equation that describes both polymolecular adsorption and the unusual adsorption behavior observed for supercritical fluids. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.
- DOE Contract Number:
- FG02-87ER13777
- OSTI ID:
- 76406
- Journal Information:
- Journal of Chemical Physics, Vol. 103, Issue 6; Other Information: PBD: 8 Aug 1995
- Country of Publication:
- United States
- Language:
- English
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