Abstract
In the previous paper it has been proven that a BET compatible specific surface area, a(c)/(s)(N2, 77), can be calculated from any Type I isotherm measured below the critical temperature. In this paper it is proven that the same calculation can be performed from any Type II isotherms if the isotherm has a pure monolayer domain. In order to distinguish the mono- and multilayer adsorption the relative free energy of the surface as a function of the adsorbed amount, π(r)(n(s)), and the functions ψ(p(r)) and ψ(n(s)) are applied, both defined by the differential expression (n(s)/p(r))(dp(r)/dn(s)). When the multilayer adsorption becomes the dominant process then the function π(r)(n(s)) has a point of inflexion and functions ψ(p(r)) and ψ(n(s)) have maximum values. It has been demonstrated that in most of the Type II isotherms the mono- and multilayer domains can be separated, so the monolayer component isotherm can be calculated by the T (Toth) equation. Therefore, it is possible to calculate the BET compatible specific surface area discussed in detail in the previous paper. It has also been proven that there are Type II isotherms which describe only multilayer adsorption; i.e., the functions ψ(p(r)) and ψ(n(s)) do not have maximum values. In these cases the Harkins-Jura equation should be applied.
| Original language | English |
|---|---|
| Pages (from-to) | 411-418 |
| Number of pages | 8 |
| Journal | Journal of Colloid and Interface Science |
| Volume | 212 |
| Issue number | 2 |
| DOIs | |
| Publication status | Published - Apr 15 1999 |
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Keywords
- BET compatible surface area
- Harkins-Jura equation
- Mono- and multilayer domains
- Separation of those
- T equation
- Type II isotherms
ASJC Scopus subject areas
- Colloid and Surface Chemistry
- Physical and Theoretical Chemistry
- Surfaces and Interfaces
Cite this
Separation of the first adsorbed layer from others and calculation of the BET compatible surface area from type II isotherms. / Tóth, József; Berger, F.; Dékány, I.
In: Journal of Colloid and Interface Science, Vol. 212, No. 2, 15.04.1999, p. 411-418.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Separation of the first adsorbed layer from others and calculation of the BET compatible surface area from type II isotherms
AU - Tóth, József
AU - Berger, F.
AU - Dékány, I.
PY - 1999/4/15
Y1 - 1999/4/15
N2 - In the previous paper it has been proven that a BET compatible specific surface area, a(c)/(s)(N2, 77), can be calculated from any Type I isotherm measured below the critical temperature. In this paper it is proven that the same calculation can be performed from any Type II isotherms if the isotherm has a pure monolayer domain. In order to distinguish the mono- and multilayer adsorption the relative free energy of the surface as a function of the adsorbed amount, π(r)(n(s)), and the functions ψ(p(r)) and ψ(n(s)) are applied, both defined by the differential expression (n(s)/p(r))(dp(r)/dn(s)). When the multilayer adsorption becomes the dominant process then the function π(r)(n(s)) has a point of inflexion and functions ψ(p(r)) and ψ(n(s)) have maximum values. It has been demonstrated that in most of the Type II isotherms the mono- and multilayer domains can be separated, so the monolayer component isotherm can be calculated by the T (Toth) equation. Therefore, it is possible to calculate the BET compatible specific surface area discussed in detail in the previous paper. It has also been proven that there are Type II isotherms which describe only multilayer adsorption; i.e., the functions ψ(p(r)) and ψ(n(s)) do not have maximum values. In these cases the Harkins-Jura equation should be applied.
AB - In the previous paper it has been proven that a BET compatible specific surface area, a(c)/(s)(N2, 77), can be calculated from any Type I isotherm measured below the critical temperature. In this paper it is proven that the same calculation can be performed from any Type II isotherms if the isotherm has a pure monolayer domain. In order to distinguish the mono- and multilayer adsorption the relative free energy of the surface as a function of the adsorbed amount, π(r)(n(s)), and the functions ψ(p(r)) and ψ(n(s)) are applied, both defined by the differential expression (n(s)/p(r))(dp(r)/dn(s)). When the multilayer adsorption becomes the dominant process then the function π(r)(n(s)) has a point of inflexion and functions ψ(p(r)) and ψ(n(s)) have maximum values. It has been demonstrated that in most of the Type II isotherms the mono- and multilayer domains can be separated, so the monolayer component isotherm can be calculated by the T (Toth) equation. Therefore, it is possible to calculate the BET compatible specific surface area discussed in detail in the previous paper. It has also been proven that there are Type II isotherms which describe only multilayer adsorption; i.e., the functions ψ(p(r)) and ψ(n(s)) do not have maximum values. In these cases the Harkins-Jura equation should be applied.
KW - BET compatible surface area
KW - Harkins-Jura equation
KW - Mono- and multilayer domains
KW - Separation of those
KW - T equation
KW - Type II isotherms
UR - http://www.scopus.com/inward/record.url?scp=0343259961&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0343259961&partnerID=8YFLogxK
U2 - 10.1006/jcis.1998.6073
DO - 10.1006/jcis.1998.6073
M3 - Article
AN - SCOPUS:0343259961
VL - 212
SP - 411
EP - 418
JO - Journal of Colloid and Interface Science
JF - Journal of Colloid and Interface Science
SN - 0021-9797
IS - 2
ER -