Table 3.

Isotherm model parameters of the metal adsorption on PAC and MWCNT at pH 7.0.

Adsorbents	Systems	Metals	Langmuir			Freundlich
			q max⁡ a	k L b	R 2	k F c	1/n d	R 2
PAC	Single metal	Cu(II)	34.72 ± 1.47e	0.94 ± 0.13e	0.993	15.54 ± 1.54e	0.40 ± 0.07e	0.931
		Pb(II)	35.15 ± 1.15	1.30 ± 0.14	0.995	17.04 ± 1.60	0.39 ± 0.07	0.925
		Cd(II)	11.23 ± 0.38	0.11 ± 0.01	0.999	1.40 ± 0.11	0.60 ± 0.03	0.994
	Multimetal	Cu(II)	32.79 ± 0.76	0.73 ± 0.05	0.998	12.93 ± 0.99	0.44 ± 0.05	0.970
		Pb(II)	35.08 ± 0.38	0.617 ± 0.02	0.999	12.69 ± 0.98	0.46 ± 0.05	0.972
		Cd(II)	6.84 ± 0.20	0.10 ± 0.01	0.999	0.85 ± 0.09	0.595 ± 0.04	0.988
MWCNT	Single metal	Cu(II)	41.42 ± 0.58	0.72 ± 0.03	0.999	17.49 ± 0.98	0.41 ± 0.04	0.988
		Pb(II)	59.08 ± 0.37	1.22 ± 0.02	0.999	30.95 ± 0.96	0.57 ± 0.05	0.983
		Cd(II)	23.07 ± 0.97	0.13 ± 0.01	0.998	3.34 ± 0.45	0.60 ± 0.06	0.976
	Multimetal	Cu(II)	36.53 ± 2.63	1.13 ± 0.33	0.985	19.11 ± 0.54	0.32 ± 0.02	0.994
		Pb(II)	48.21 ± 2.00	0.36 ± 0.03	0.998	12.53 ± 0.57	0.58 ± 0.03	0.993
		Cd(II)	17.86 ± 0.56	0.11 ± 0.01	0.999	2.26 ± 0.27	0.62 ± 0.05	0.983

^aMaximum adsorption capacity estimated by Langmuir isotherm model (mg g⁻¹).

^bAdsorption affinity estimated by Langmuir isotherm model (L mg⁻¹).

^cFreundlich model capacity ((mg/g) (L/mg)^1/n).

^dFreundlich model site heterogeneity factor (dimensionless).

^eStandard errors.