Table 3. Comparison of the Regression Coefficients (R²) for the three Isotherms.

Metal ions

Regression coefficient (R²)

Unmodified

Modified

450 µm

850 µm

450 µm

850 µm

Freundlich Isotherm

Cd
Pb
Zn

0.9405
0.9564
0.9935

0.6772
0.9508
0.9913

0.7478
0.9551
0.8963

0.9333
0.9805
0.9834

Langmuir Isotherm

Cd
Pb
Zn

0.7067
0.8918
0.9491

0.8156
0.1742
0.7529

0.1902
0.3227
0.9762

0.8969
0.8083
0.9034

Dubinin-Radushkevich Isotherm

Cd
Pb
Zn

0.9177
0.9698
0.9605

0.955
0.9849
0.9903

0.9114
0.9727
0.9969

0.9768
0.9899
0.9903