© A.W.Marczewski 2002
A Practical Guide to Isotherms of ADSORPTION on Heterogeneous Surfaces
Reload Adsorption Guide
Linear Langmuir plot
Use a linear Langmuir plot (compare other linear plots as well as Graham plot): Ads vs. Ads / Conc in order to find your type of heterogeneity (if any), lateral interactions (if needed) or multilayer buildup "correction". (Ads/Conc vs. Ads plot is known as Scatchard plot).
(Here are model pictures):
NOTE:
Replace Conc with Pressure for gas adsorption.
-
L - Langmuir - ideal bulk and surface phase; monolayer; homogeneous surface
-
GL - Generalized Langmuir - ideal bulk and surface (adsorbed) phase; monolayer; heterogeneous surface (it has its own version of linear plot which requires a priori knowledge of heterogeneity parameters). LF, GF and Toth may be considered as special cases of GL isotherm.
-
bi-L - bi-Langmuir - ideal bulk and surface phase; monolayer; two types of surface sites (special case of multi-site Langmuir equation.
-
F-G - Fowler-Guggenheim: as Langmuir + mean-field lateral interactions in surface phase (formally the same as Frumkin isotherm)
-
Kis - Kiselev (simplified equation): as Langmuir + lateral associative interactions in surface phase.
full-Kis - full Kiselev: as Langmuir + lateral associative interactions in surface phase, may also involve lateral interactions of FG-type (mean field approx.)
-
GF - Generalized Freudlich - Langmuir + surface heterogeneity similar to Freudlich (exponentially decreasing distribution of ads. energy), but in contrast to the "true Freundlich" - monolayer; reduces to Freundlich eq. for low adsorption values and to Langmuir at high adsorption values. Special case of GL isotherm
-
LF - Langmuir-Freudlich - Langmuir + symmetrical quasi-gaussian surface heterogeneity (exponentially decreasing distribution of ads. energy on both sides); monolayer; reduces to Freundlich (or GF) eq. for low adsorption values, for high adsorptions becomes similar to Toth equation. Special case of GL isotherm
-
T - Tóth - Langmuir + asymmetrical quasi-gaussian surface heterogeneity (exponentially decreasing distribution of ads. energy on both sides with bigger tail for low adsorption energies); monolayer; reduces to Henry eq. (a=Kc) for low adsorption values and becomes similar to LF for high adsorption values. Special case of GL isotherm
-
GF-Kis - as GF but with associative interactions (Kiselev)
-
GF-BET - as GF but with BET multilayer buildup
-
Jov - Jovanovic - homogeneous surface with vertical interactions bulk-surface phase
-
Jov-m - Jovanovic-Freundlich (JF/Jov-m) - Jovanovic + surface heterogeneity
-
RP - Radke-Prausnitz (aka. Redlich-Peterson) - non-monolayer experimental equation, contains Henry region, for higher adsorptions behaves like Freundlich eqn.
Adsorption
My papers
Search for papers
Main page
Top
E-mail addresses are modified to in order to prevent spamming / mail-abuse:
in e-mail remove spaces, replace " AT@AT " by "@"
Send a message to Adam.Marczewski AT@AT umcs.lublin.pl
Disclaimer