Table 2.

Coefficients of determination (R²), standard errors of estimate (SEE) and other parameters obtained from kinetic models for methylthioninium chloride sorption onto date palm waste-derived biochar (DBC), date palm waste-derived carbon nanodots (nCD-DBC), and date palm waste-derived biochar composited with nano zero-valent iron (nZVI-DBC).

Sorbent	Parameter	nCD-DBC	nZVI-DBC	DBC
First-order	k1	1.6 × 10–3	1.8 × 10–3	2.3 × 10–3
	R2	0.15	0.10	0.23
	SEE	0.002	0.009	0.031
Second-order	k2	− 6.8 × 10–7	− 2.3 × 10–6	− 1.2 × 10–5
	R2	0.74	0.87	0.79
	SEE	0.009	0.020	0.899
Pseudo-first-order	k1'	− 4.8 × 10–3	− 5.1 × 10–3	− 5.4 × 10–3
	qe	5.99	6.38	6.23
	R2	0.07	0.08	0.07
	SEE	0.025	0.019	0.030
Pseudo-second-order	k2'	7.1 × 10–5	3.7 × 10–5	1.7 × 10–5
	qe	1793.40	1182.80	1008.80
	h	227.50	52.22	17.21
	R2	0.93	0.99	0.99
	SEE	0.001	0.001	0.001
Elovich	a	179.77	267.71	161.17
	β	202.23	− 3.11	− 122.28
	R2	0.86	0.97	0.94
	SEE	0.046	0.062	0.023
Intraparticle diffusion	kid	41.25	30.85	29.41
	c	724.82	311.92	140.11
	R2	0.50	0.70	0.76
	SEE	0.1137	0.0116	0.0133
Power function	kf	0.68	0.71	0.83
	b	3.82	3.11	2.07
	R2	0.51	0.62	0.81
	SEE	0.001	0.000	0.000