Table 4 Isotherm parameters for the biosorption of Cu²⁺ on Oxalic acid modified and raw Saccharum officinarum biomas

Langmuir

Q _max (mg g⁻¹)

379.15

236.16

b (L mg⁻¹)

0.0069

0.12

R_L

0.36

0.04

R ²

0.999

0.990

Freudlinch

K_F (mg g⁻¹ (mg L⁻¹)^−1/n)

6.55

51.13

n

1.46

2.83

R ²

0.996

0.983

Tempkin

A_T (L g⁻¹)

0.08

1.14

B_T (J mol⁻¹ g mg⁻¹)

33.06

49.62

R ²

0.999

0.989

Dubinin–Radushkevich

Q _s (mg g⁻¹)

172.08

195.14

E (kJ mol⁻¹)

0.06

0.39

R ²

0.984

0.989

Redlich–Peterson

Q ₀ (mg g⁻¹)

2.28

26.39

K _R (mg⁻¹ g)^1/g

0.000513

0.0845

g

1.47

1.07

R ²

0.999

0.990

Sips

Q _s (mg g⁻¹)

258.63

207.09

\(K_{s} \left( {{\text{mg}}^{{ - 1}} {\text{L}}} \right)_{{\text{s}}}^{{1/\beta }}\)

0.014

0.17

β_s

1.32

1.61

R ²

0.999

0.992

Hill

Q _H (mg g⁻¹)

262.65

207.09

\(K_{H} \left( {mg^{ - 1} L} \right)_{H}^{1/n}\)

269.23

17.58

n_H

1.30

1.61

R ²

0.999

0.992

Toth

Q _T (mg g⁻¹)

142.99

270.12

K _T (mg L⁻¹)

108.91

8.88

t

1.18

0.97

R ²

0.999

0.990