Langmuir model

Freundlich model

adsorbent

adsorbate

qm (mmol∙g1)

KL (L∙mmol1)

R2

n

KF (mmol∙L−1/n∙L1/n∙g−1)

R2

Sewage sludge

Cd2+

0.25

1.17

0.986

3.25

0.35

0.962

Pb2+

0.35

3.50

0.982

0.44

2.68

0.936

Ni2+

0.20

0.52

0.991

0.21

2.15

0.984

Alkali treated sludge

Cd2+

0.76

21.14

0.993

0.80

3.50

0.947

Pb2+

1.05

35.09

0.970

1.07

4.69

0.929

Ni2+

0.52

3.18

0.992

0.55

2.04

0.990