Multicomponent Equilibrium Thermodynamics - Elements of Environmental Engineering: Thermodynamics and Kinetics - page 94

satisfactorily at low C i values, whereas significant deviations are observed at high C i
values. The Langmuir isotherm severely under-predicts adsorption at high C i values,
whereas the Freundlich isotherm severely over-predicts the adsorption in the same
region.Thus neither of the isotherms can be used over the entire region of concentrations

(a) 4.00E + 4 (b) -8

-8.1
-8.2
-8.3
-8.4
-8.5
-8.6
-8.7
-8.8
-8.9
-9

3.50E + 4

3.00E + 4

2.50E + 4

2.00E + 4

1.50E + 4

1.00E + 4

5.00E + 3

0.00E + 0

-9

-8.5 -8 -7.5 -7 -6.5 -6

log C i

1/ C i (L/mol)

FIGURE 3.13 Langmuir (a) and Freundlich (b) isotherm plots for the adsorption of
an insecticide (chlordane) on GAC.

0.00030

0.00025

0.00020

0.00015

0.00010

Langmuir
Freundlich
Experimental

0.00005

0.00000

0.0 5.0e-8 1.0e-7 1.5e-7 2.0e-7 2.5e-7 3.0e-7 3.5e-7

C i /mol ∙ L -1

FIGURE 3.14 Adsorption isotherms for chlordane on GAC.