Table 2 Freundlich isotherm model parameters and correlation coefficients for the adsorption of Cu²⁺ and Fe³⁺ ions on ZnO, SiO₂, and MgO NPs.

2.85

2.88

0.95

5.26

1.05

0.63

2.85

2.34

0.96

3.35

8.12

0.94

2.00

1.13

0.96

2.94

6.45

0.88

3.35

9.54

0.94

1.88

1.11

0.97

3.33

8.31

0.95

2.94

2.15

0.95

2.11

0.70

0.92

2.92

1.62

0.78

1.88

2.42

0.96

1.74

1.10

0.99

2.08

2.51

0.90

1.97

3.81

0.92

1.53

1.17

0.98

2.38

2.70

0.99