sites, while the Freundlich equation is based on the sorption,
on a heterogeneous surface. Parameters of both
Langmuir and Freundlich models were calculated from the
intercepts and slopes of 1/qeq versus 1/Ceq and log qeq
versus log Ceq plots, respectively (Fig. 5). The Langmuir
plot of lead ions is shown in Fig. 5a and the summary
detailing the Langmuir constant (b), maximum adsorption
capacity and determination coefficient is shown in Table 7.
The maximum adsorption capacity (qmax) is 20.36 mg g-1,
which is almost similar to the experimental value
(21.6 mg g-1) indicating that the isotherm data fitted well
to the Langmuir plot. The maximum adsorption capacity
(Kf) of lead ions based on Freundlich model, the adsorption
intensity value (n), and determination coefficient are given
in Table 7. Although the value of n is greater than 1, the Kf
value (5.12 mg g-1) is by far, much lower than the
experimental adsorption capacity, which indicates that the
adsorption of lead ions does not fit well with Freundlich
model.