TABLE 2.

Kinetic parameters for the adsorption of Congo red dye on lignin and magnetic lignin composites.

Kinetics model	Parameter	Lignin	Fe3O4@lignin
			1:0.5	1:1	1:2	1:3
Pseudo-first order	qe exp (mg/g)	37.43	237.69	152.44	25.78	26.73
	qe cal (mg/g)	34.52	236.60	136.43	21.14	24.66
	k1 (× 10–2/min)	0.10	17.90	6.30	4.10	2.40
	R2	0.89	0.99	0.68	0.49	0.83
Pseudo-second order	qe exp (mg/g)	37.43	237.69	152.44	25.78	26.73
	qt cal (mg/g)	32.67	261.13	148.27	22.26	28.21
	k2 (× 10–2 g/mg min–1)	0.06	0.12	0.07	0.33	0.11
	R2	0.93	0.98	1.00	0.64	0.99
Intraparticle diffusion model	ki (mg/g min1/2)	2.45	1.57	4.59	1.04	1.21
	C (mg/g)	1.90	216.00	80.18	8.48	7.50
	R2	0.94	0.46	0.94	0.94	0.97