one can easily understand the topic following these slides

1. Topic: Freundlich Adsorption Isotherm
Presented By
ARIFUL HOQUE
SCHOOL OF NANO SCIENCE
M. Sc 4TH Semester

2. Freundlich Adsorption Isotherm
The extent of adsorptions of a gas per unit mass of
adsorbent depends upon the pressure of the gas.
x
m
Where,
X= extent of adsorption
m= mass of adsorbent
∞ P
Adsorbent
Gas particles

3. Plot between extent of adsorption
vs pressure of the gas
Extent of adsorption:
x
m
x
m
P = pressure
= “x” is the amount of adsorbate
and “m” is the mass of adsorbent
= amount of gas adsorbed
Initially,
Finally,
x
m
x
m
∞P1
∞P0

4. The extent of adsorption increases
with pressure and become maximumAmountofgas
adsorbed
(Saturation pressure)

5.  The corresponding pressure is called equillibrium pressure,
Ps
At the pressure (Ps)
Amount of gas ADSORBED= Amount of gas DESORBED
Ps
Desorption of gas moleculeAdsorption of gas molecule

6. Detail analysis of the Freundlich
adsorption isotherm
1. At low pressure: The graph is almost straight line
2. At high pressure: The graph becomes parallel to X-axis
x
m ∞P1
x
m
=K P1
Where, K= Constant
x
m ∞P0
x
or
m
= K P0
Where, K= Constant
P0 =1
Therefore,
m
x = Constant
or

7. 3. Intermediate pressure: It becomes polynomial function of
the degree 1/n , x/m will depend upon the power of pressure
which lies between 0 & 1
m
x
= KP1/n
When “n” is an integer
Where “n” can take any whole number value which depends
upon the nature of ADSORBATE and ADSORBENT

8. Freundlich adsorption isotherm
equation
m
x
= KP1/n Where,0 > 1/n > 1
n= 1 to ∞
At low pressure At high pressure
=K P1x
m
1/n = 1
n = 1or
x
m = K P0
1/n = 0
n = ∞or
Where, Where,

9. Verification of Freundlich adsorption
isotherm equation
x
m
∞ KP1/n
x
m
= KP1/n
Taking log on both sides,
log x/m = log k + log P1/n
log x/m = log k + 1/n log p
Which is y = c + mx