Table 2. Freundlich, Langmuir and Dubinin-Radushkevich isotherm constants for the metal ions adsorption on unmodified and modified maize husk of 450 µm and 850 µm particle sizes.

Metal ions

Unmodified

Modified

450 µm

850 µm

450 µm

850 µm

*F

K_F

n

K_F

n

K_F

n

K_F

n

Cd

Pb

Zn

4.0 x 10^-6

0.38

2.93 x 10^-3

0.62

114.10

3.42

1.22

1.03

6.64 x 10^-4

0.55

4.41 x 10^-5

0.46

117.19

3.99

3.06

0.94

0.49

0.86

0.16

0.76

614.11

40.82

94.84

3.21

*L

As

K

As

K

As

K

As

K

Cd

-151.51

-6.88 x 10^-4

-3.33 x 10²

-3.86 x 10^-4

833.33

8.93 x 10^-3

1.25 x 104

8.43 x 10^-5

Pb

-217.39

-4.58 x 10^-4

-142.86

-4.78 x 10^-4

714.29

7.36 x 10^-3

1.25 x 104

3.85 x 10^-5

Zn

-3.33 x 10³

-3.26 x 10^-4

-166.67

-4.97 x 10^-3

769.23

0.04

833.33

7.25 x 10^-3

*D-R

B_D

q_D

E

B_D

q_D

E

B_D

q_D

E

B_D

q_D

E

Cd

0.456

3422.07

1.05

0.326

1138.54

1.24

0.011

748.37

6.74

0.083

1186.78

2.45

Pb

0.388

1401.36

1.14

0.469

1585.41

1.03

0.015

647.42

5.77

0.144

1004.66

1.86

Zn

0.093

1685.47

2.32

0.125

2049.40

2.00

0.003

743.45

12.91

0.013

733.04

6.20