Table 2.

R² and constant values for the different adsorption isotherm models of Ni(II). (Adsorption experiments—sample dosage: 0.05 g; initial Ni(II) concentration: 700 mg/L; pH value: 5.5; temperature: 50 °C; adsorption time: 40 min).

Metal	Parameters	Langmuir		Freundlich		Temkin		Dubinin–Radushkevichl
Ni(II)	R2	0.9976		0.9364		0.7522		0.6917
	Constants	KL	0.0173 L/mg	Kf	90.64 L/g	bt	40.87 J/mol	B	1.374 × 10−8 mol2·2
		RL	0.165
		qmax	1120.33 mg/g	1/n	0.139	at	2.061 × 109 L/g	qmax	815.32 g/mg