Module 8 : Surface Chemistry
Lecture 36 : Adsorption
36.2

Adsorption Isotherms

36.2.4

Langmuir adorption isotherm for several non-dissociatively adsorbed species

 

If two species A and B are adsorbed on the surface. Then applying Langmuir hypothesis for species A, we have,

 

(36.2.16)
 

(36.2.17)
 
 
  (36.2.18)
  Similarly for species B,
 

(36.2.19)
 

or,

 
 

(36.2.20)
 

Now, patting the value from (36.2.20) into equation (36.2.18), we get

 
 
 

(36.2.21)
  (36.2.22)
 

Similarly, we can obtain

  (36.2.23)
  In general, Langmuir adsorption isotherm for species A under conditions of several non-dissociatively adsorbed species could be derived as,
 

(36.2.24)
  where the sum runs over all species.
   
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