The influence of carbonization temperature on the modification of TiO₂ in the removal of methyl orange from aqueous solution by adsorption

Figures & data

Fig. 1. Schematic presentation of installation setup for the synthesis of C–TiO₂ [21].

Notes: (1) Gas cylinder with argon, (2) controller, (3) Dreschel bottle with ethanol, (4) pipe furnace, (5) combustion boat with powder sample, and (6) scrubber.

Fig. 2. SEM of (a) unmodified TiO₂, (b) C–TiO₂-200, (c) C–TiO₂-300, and (d) C–TiO₂-400. The scale bar represents 500 nm.

Fig. 3. Nitrogen adsorption/desorption isotherm of (a) TiO₂, (b) C–TiO₂-200, (c) C–TiO₂-300, and (d) C–TiO₂-400.

Table 1 Textual properties of TiO₂ and C–TiO₂ adsorbents

Adsorbent	SBET (m^2/g)	Vtotal 0.95 (cm^3/g)	Vmikro DR (cm^3/g)	Vmezo (cm^3/g)
TiO2	44	0.0163	0.016	0.003
C–TiO2-200	51	0.710	0.020	0.690
C–TiO2-300	52	0.49	0.020	0.47
C–TiO2-400	53	0.790	0.020	0.770

Fig. 4. XRD patterns of the prepared adsorbents and TiO₂ precursor.

Fig. 5. FTIR spectra of modified and unmodified TiO_2, (a) C–TiO₂-200, (b) C–TiO₂-300, (c) C–TiO₂-400, and (d) TiO₂.

Fig. 6. Time dependency of the adsorption of MO by C–TiO₂ adsorbents. Solid and dashed lines represent the predicted q_t values by PSO model.

Table 2 Obtained constants of PFO and PSO rate equations for the adsorption of MO onto C–TiO₂ adsorbents

Adsorbent	PFO				PSO
	qe (mg/gads)	k1 (1/min)	r^2		qe (mg/gads)	k2 (gads/mg min)	r^2
C–TiO2-200	201.3	0.0050	0.9642		200.00	0.00038	0.9996
C–TiO2-300	403.9	0.0044	0.8962		400.00	0.00006	0.9955
C–TiO2-400	520.1	0.1506	0.8644		588.235	0.00030	0.9956

Fig. 7. Adsorption isotherm of MO onto TiO₂ and C–TiO₂ adsorbents at 25°C.

Table 3 Obtained isotherm constants for adsorption of MO onto TiO₂ and C–TiO₂ adsorbents

Isotherm models		TiO2	C–TiO2-200	C–TiO2-300	C–TiO2-400
Langmuir	KL (L/mg)	3.000	4.367	137.475	182.936
	qm (mg/g)	0.0288	0.018	0.0007	0.0003
	r^2	0.8875	0.9584	0.7260	0.9668
Freundlich	KF (L mg^(1−1/n)/g)	0.1822	1.059	141.982	321.436
	n	0.442	0.452	0.479	0.393
	r^2	0.9304	0.968	0.9307	0.9905
Langmuir–Freundlich	KL–F (L/mg)	0.0624	0.057	0.0015	0.0018
	qm (mg/g)	47.619	171.428	500.000	909.090
	n	0.90	0.90	0.25	0.25
	r^2	0.8714	0.9488	0.9982	0.9990
Tempkin	b	180.66	53.373	189.000	354.43
	r^2	0.6968	0.433	0.9271	0.8516

Fig. 8. Removal percentage of MO by (a) C–TiO₂-200 (b) C–TiO₂-300 and (c) C–TiO₂-400 at different pH.

Fig. 9. MO structure at (a) acidic and (b) basic mediums.

Fig. 10. ZPs of TiO₂ and C–TiO₂ adsorbents.

Fig. 11. Regeneration studies of C–TiO₂ adsorbent.

Fig. 12. The intraparticle diffusion plot for adsorption of MO onto (a) C–TiO₂-200, (b) C–TiO₂-300 and (c) C–TiO₂-400.

M. Janus, M. Inagaki, B. Tryba, M. Toyoda, A. Morawski, Carbon-modified TiO2 photocatalyst by ethanol carbonisation, Appl. Catal. B 63 (2006) 272–276.10.1016/j.apcatb.2005.10.005

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