Table 4.

Number of moles sorbed (Nf), parameters of the Freundlich (n and K_f), Temkin (K_T and b), correlation coefficients (r), and respective error for the interaction of Cu²⁺ and Pb²⁺ with chitosan, CH-AN at 298 ± 1 K, using a nonlinear method.

Isotherm	Constant	Cu(II)	Pb(II)
Langmuir	Nf (mmol g−1)	2.02	2.54
	Ns (mmol g−1)	2.87 ± 0.03	3.02 ± 0.03
	b (g mmol−1)	0.29 ± 0.01	0.30 ± 0.01
	R2	0.999	0.996
	χ2	0.002	0.001
Freundlich	Kf (mmol g−1)	0.70 ± 0.04	0.98 ± 0.06
	n	1.89 ± 0.12	2.87 ± 0.22
	R2	0.982	0.948
	χ2	0.007	0.017
Temkin	KT (mmol dm−3)	3.52 ± 0.32	2.96 ± 0.32
	b (kJ mol−1)	1.68 ± 0.06	1.50 ± 0.05
	R2	0.988	0.986
	χ2	0.005	0.004