Table 3.

Langmuir, Freundlich, Sips, and Redlich–Peterson isotherm model parameters for Pb(II) adsorption onto NK and KDK

Adsorbent	Langmuir isotherm model
	qm (mg g−1)		kL (dm3mg-1)	R2	RMSE	SSE
NK	15.52		0.2292	0.9953	0.4089	1.338
KDK	46.45		1.157	0.9994	0.4598	1.057
Adsorbent	Freundlich isotherm model
	KF (mg g−1) (L mg−1)1/n		n	R2	RMSE	SSE
NK	6.226		5.524	0.8954	1.921	29.53
KDK	30.23		10.28	0.9565	4.003	80.12
Adsorbent	Sips isotherm model
	KS (L g−1)	βS	aS	R2	RMSE	SSE
NK	15.06	1.269	0.1747	0.9985	0.2443	0.4177
KDK	53.15	1.152	1.152	0.9998	0.3281	0.4307
Adsorbent	Redlich–Peterson isotherm model
	KR (L g−1)	aR (L/mg)	g	R2	RMSE	SSE
NK	3.138	0.17	1.036	0.9973	0.3296	0.7606
KDK	51.17	1.065	1.008	0.9996	0.4166	0.6941