Table 1.

Langmuir and Freundlich adsorption isotherm constants for the adsorption of Pb²⁺ ions on to GAC, HAP/GAC and HAP/TE/GAC

Material	Langmuir adsorption isotherm constants			Freundlich adsorption isotherm constants
	qm (mg/g)	K (L/mg)	R2	Kf	n	R2
HAP/GAC	36.9 (± 0.8)	3.1 × 10−3 (± 1.1 × 10−4)	0.9989	1.1 (± 0.2)	2.0 (± 0.1)	0.9939
GAC	31.1 (± 2.3)	3.6 × 10−3 (± 4.6 × 10−4)	0.9891	1.4 (± 0.2)	2.3 (± 0.2)	0.9905
HAP/TE/GAC	29.4 (± 7.2)	3.1 × 10−3 (± 1.2 × 10−3)	0.8931	1.1 (± 0.7)	2.2 (± 0.6)	0.8818