Thermodynamics and statistical mechanics of multilayer adsorption.
The multilayer adsorption models of Brunauer-Emmett-Teller and Guggenheim-Anderson-de Boer are reconsidered. The relationship between the fitting parameters and the physical parameters of the equation is discussed. The preexponential factors of the parameters are shown to be in general far different from unity, contrary to a widespread use. A thermodynamical derivation illuminates the hypothesis on which the multilayer sorption equation is dependent and frees it from too restrictive hypothesis usually taken as necessary for its validity. Equations are derived for the number fraction of sorption sites occupied by different numbers of molecules. The Guggenheim-Anderson-de Boer equation is shown to imply incomplete occupation (jamming) of the first sorption layer at saturation.
Monleón Pradas
Manuel
M
Centro de Biomateriales, Universidad Politécnica de Valencia, P.O. Box 22012, E-46071 Valencia, Spain. mmonleon@upvnet.upv.es
Salmerón Sánchez
Manuel
M
Gallego Ferrer
Gloria
G
Gómez Ribelles
José Luis
JL
D000042:Absorption; D000327:Adsorption; D002627:Chemistry, Physical / Q000379:methods*; D003627:Data Interpretation, Statistical; D008956:Models, Chemical; D015233:Models, Statistical; D008962:Models, Theoretical; D015394:Molecular Structure; D013379:Substrate Specificity; D013696:Temperature; D013816:Thermodynamics; D014867:Water
D014867:Water