Table 4.

Langmuir and Freundlich isotherm constants for the adsorption of Hg(II) on PPTA-AM at 25°C (pH 5.0).

Adsorbents	Langmuir			Freundlich			Ratio of functional group to metal ion*
	qthe (mmol g−1)	KL (L mmol−1)	$R_L^2$	KF (mmol g−1)	n	$R_F^2$	(NH2+SH)/Hg(II)
PPTA-AM-90	1.32	1.42	0.9982	0.051	1.80	0.9802	1.36
PPTA-AM-70	1.54	0.41	0.9961	0.10	2.42	0.9775	1.25
PPTA-AM-50	1.41	0.43	0.9914	0.11	1.98	0.9682	1.42
PPTA-AM-30	1.34	0.45	0.9912	0.15	1.68	0.9743	1.49
PPTA-AM-10	1.33	0.54	0.9941	0.041	1.57	0.9891	1.42

^*The Ratio of functional group to metal ion is equal to M/q; wherein, M presents the amount of functional group (NH₂ + SH) in PPTA-AM (Table 1).