Freundlich Isotherm; Temkin Isotherm - Micromeritics TriStar II 3020 Operator's Manual

TriStar II 3020

Freundlich Isotherm

The Freundlich isotherm has the form:
1/m
Q
-------
=
CP
Q
m
where
Q =
Q =
m
C =
m =
The pressure is absolute; typically, m > 1. In terms of quantity adsorbed,
1/m
=
Q Q CP
m
Taking the log of both sides yields:
log = log
Q Q

Temkin Isotherm

The Temkin isotherm has the form,
Q RT
------- -------- -
= ln

Q q
0
m
where
Q =
Q =
m
q =
0
A =
In terms of quantity adsorbed,
RTQ
S
------------- -
= ln
Q

q
0
Thus, the plot of the natural log of absolute pressure vs. quantity adsorbed yields a straight line with
slope RTQ /q and intercept (ln A) RTQ
m 0
302-42828-01 - Dec 2012
quantity of gas adsorbed
quantity of gas in a monolayer
temperature-dependent constant
temperature-dependent constant
1
--- -
+ log
C P
m
m
 
A P
0
quantity of gas adsorbed
quantity of gas in a monolayer
the differential heat of adsorption at zero surface coverage
/RT}, where 
a exp {-q
0 0
 
P
------ -
+ ln
A
 
0
Po
/q
m 0
and a are adjustable constants
0 0
.
Appendix C
C-35