Table 3 Parameters of different linear and nonlinear isotherms for Cr(VI) adsorption on PSD at 298 K

Langmuir

Linear form

q_m/mg g⁻¹

K_L/mg L⁻¹

R_L

R²

5.84

3.92

0.07

0.999

Nonlinear form

q_m/mg g⁻¹

K_L/mg L⁻¹

R_L

R²

5.77

3.84

0.07

0.9918

Freundlich

Linear form

K_F/mg g⁻¹

n

R²

1.33

2.32

0.9786

Nonlinear form

K_F/mg g⁻¹

n

R²

1.5

2.66

0.9618

Temkin–Pyzhev

Linear form

b_T/kJ mol⁻¹

A/L mg⁻¹

R²

2.12

2.93

0.9948

Nonlinear form

b_T/kJ mol⁻¹

A/L mg⁻¹

R²

2.12

2.93

0.9897

Dubinin–Radushkevich

Linear form

E/kJ mol⁻¹

q_m/mg g⁻¹

R²

1.22

3.73

0.885

Nonlinear form

E/kJ mol⁻¹

q_m/mg g⁻¹

R²

2.65

4.72

0.9028