Freundlich isotherm is used for modeling the adsorption on
heterogeneous surfaces. This isotherm can be described as
follows:
qe ¼ KfC1=n
e ð6Þ
where Kf and n are the Freundlich constants related to the
adsorption capacity and intensity of the sorbent, respectively
(Freundlich, 1906). The Freundlich model can be easily linearized
by plotting it in a logarithmic form:
log qe ¼ logKf þ 1=n logCe ð7Þ
The plots of non-linearized Langmuir and Freundlich
adsorption isotherms are shown in Figs. 7 and 8. The adsorption
isotherm constants were determined by using non-linear
regression. The Langmuir and Freundlich adsorption constants
evaluated from the isotherms with the correlation
coefficients are also presented in Table 1. The best-fit equilibrium
model was determined based on the linear regression