Chemical Reactions on Solid Surfaces - Bioprocess Engineering: Kinetics, Biosystems, Sustainability and Reactor Design - page 465

on the adsorbent surface. However, the monolayer coverage deduced from the BET model
may not be true monolayer coverage, however it may be used to correlate the surface area.

Types IV and V are all multilayer adsorption isotherms. They could be observed for both
chemisorptions and physisorptions. For chemisorptions, the multilayer concept is merely an
approximation to the different level of interaction energy as a combination of adsorbate e
adsorbent and adsorbate e adsorbate interactions. Again, there is a saturation adsorption
level, i.e. the adsorption capacity is limited.
For multispecies adsorption on the same sites nonselectively, the coverage of species j on
layer i (among the total of N layers) is given by

i 1 N

cðb b Þ

q ij ¼

1 K j C j

(9.79)

Nþ

1 ð 1 cÞb b