Fig. 5. Linearized: (a) Langmuir and (b) Freundlich isotherm models for Pb2+
adsorption by the FeAA at different temperatures.
linear regression. According to Fig. 5b, the values of KF and n
are obtained similarly. The results are presented in Table 2 with
the correlation coefficients (R2). It can be seen from Table 2
that the Langmuir model yields a better fit than the Freundlich
model by comparing the results of correlation coefficient values
at different temperatures. The values of Freundlich constants
increased with increasing temperature and the highest KF value
was reported as 11.15 at 318 K. All n values were found high
enough for adsorption (>1.0). Values of qm and KL at different
temperatures are also tabulated in Table 2. The maximum capacity,
qm defined the total capacity of FeAA for Pb2+ adsorption
Table 2
Parameters of Langmuir and Freundlich adsorption isotherm models for Pb2+
on FeAA
T (K) Langmuir Freundlich
qm KL R2 KF n R2
288 0.096 17.5 0.986 6.15 4.49 0.983
308 0.11 35.45 0.997 8.37 4.76 0.981
318 0.14 48.13 0.996 11.15 4.83 0.97