Table 4.

Isotherm parameters for OFL adsorption onto HNT, HNT/Fe₃O₄-C, HNT/Fe₃O₄-H, and HNT/Fe₃O₄-SG.

Adsorption Model	Isotherm Parameters	HNT	HNT/Fe3O4-C	HNT/Fe3O4-SG	HNT/Fe3O4-H
Langmuir	qm (mg g−1)	29.6 (8)	23 (2)	31 (2)	45 (2)
	KL (L mg−1)	0.026 (2)	0.012 (2)	0.028 (4)	0.063 (9)
	R2	0.9970	0.9910	0.9881	0.9840
	χ2	0.1739	0.2218	0.7893	2.5004
Freundlich	KF (mg g−1) (L mg−1)1/n	3.1 (6)	1.1 (1)	3 (1)	9 (2)
	1/n	0.42 (4)	0.53 (3)	0.41 (7)	0.33 (5)
	R2	0.9734	0.9931	0.9381	0.9304
	χ2	1.5239	0.1712	4.1164	10.844