Table 1 Kinetics parameters of Pb²⁺ adsorption by RMEC.

Pseudo-first order

C_o (mg/L)

50

100

150

200

250

300

Q_{e exp} (mg g^− 1)

19.25

26.76

42.33

50.27

67.33

74.03

Q_{e cal} (mg g^− 1)

19.02

25.62

40.05

51.21

68.03

74.28

k₁ (min^− 1)

0.055

0.087

0.105

0.116

0.124

0.153

R²

0.996

0.995

0.998

0.997

0.997

0.994

%SSE

0.005

0.019

0.024

0.008

0.005

0.002

RMSE

0.094

0.467

0.931

0.384

0.287

0.102

Pseudo-

second order

Q_{e cal} (mg g^− 1)

20.12

29.87

47.03

55.83

71.02

79.36

k₂ (g mg^− 1 min^− 1)

0.265

0.638

0.882

1.063

1.192

1.225

R²

0.965

0.975

0.988

0.984

0.967

0.974

%SSE

0.020

0.052

0.050

0.049

0.025

0.032

RMSE

0.355

1.268

1.919

2.270

1.506

2.176

Elovich

α

0.531

0.864

1.263

1.774

2.076

2.257

β

0.846

1.638

2.277

2.867

3.746

4.829

R²

0.993

0.987

0.966

0.986

0.978

0.981

Intra-particle diffusion

K_1d (mg g^− 1 min^− 0.5)

3.321

7.664

9.831

12.67

14.88

16.015

C₁(mg g^− 1)

0.075

0.273

0.543

0.885

1.289

1.875

R²

0.997

0.975

0.988

0.964

0.958

0.977