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The linearized Langmuir and Freundlich equations for the metal ions removal from solutions are shown (Figure 5) and their calculated constants (qm, KL, KF, and n) with correlation (r2) values are tabulated (Table 2). By looking at the Ni(II) ions removal data, we can see that r2 values are almost equal to unity, indicating that their adsorption fits Langmuir at 313 and 328 K while at 298 the isotherm fits better to the Freundlich model. Nevertheless, the Langmuir model fits better the adsorption equilibrium data Cd(II) ions.
Table 2

Langmuir and Freundlich isotherm parameters for the metal ions removal

Metal ionT(K)Langmuir constants
Freundlich constants
qm (mg·g−1)KL (L·mg−1)r2nkfr2
Ni (II) 298 57.14 0.0204 0.9906 2.099 4.21 0.9947 
313 71.94 0.0227 0.9926 1.9201 4.57 0.9592 
328 82.65 0.0236 0.9917 1.9231 5.39 0.9624 
Cd (II) 298 104.17 0.0264 0.9960 1.837 6.80 0.9706 
313 111.12 0.0281 0.9885 1.886 7.69 0.9800 
328 128.21 0.0294 0.9961 1.7717 7.97 0.9559 
Metal ionT(K)Langmuir constants
Freundlich constants
qm (mg·g−1)KL (L·mg−1)r2nkfr2
Ni (II) 298 57.14 0.0204 0.9906 2.099 4.21 0.9947 
313 71.94 0.0227 0.9926 1.9201 4.57 0.9592 
328 82.65 0.0236 0.9917 1.9231 5.39 0.9624 
Cd (II) 298 104.17 0.0264 0.9960 1.837 6.80 0.9706 
313 111.12 0.0281 0.9885 1.886 7.69 0.9800 
328 128.21 0.0294 0.9961 1.7717 7.97 0.9559 
Figure 5

(a) Langmuir and (b) Freundlich adsorption isotherms of Cd(II) and Ni(II) at different temperatures.

Figure 5

(a) Langmuir and (b) Freundlich adsorption isotherms of Cd(II) and Ni(II) at different temperatures.

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