Preparation and characterization of activated carbons from tobacco stem by chemical activation

Figures & data

Table 1. Characteristics of tobacco stem.

Ultimate analysis (wt%)		Proximate analysis (wt%)		Structural analysis (wt%)
C	42.34	Ash	8.27	Lignin	8.28
H	3.78	Moisture	4.88	Hemicellulose	13.75
N	1.45	Volatiles	68.79	Cellulose	27.36
S	0.75	Fixed C	18.06
O	51.68

Figure 1. TG and DTG curves of tobacco stem.

Table 2. Pore structural properties of activated carbon (the activation temperature of 873 K and the activation time of 1.5 hr).

Sample^a	Reagent	Ratio	SBET (m^2/g)	V (mL/g)	Vm (mL/g)	Vm/V (%)
PH-0.5	KOH	0.5	500.8	0.304	0.221	72.6
PH-1		1.0	474.8	0.309	0.196	63.2
PH-2		2.0	217.2	0.220	0.0839	38.2
PH-4		4.0	2.0	0.0132	0	0
PC-0.5	K2CO3	0.5	355.2	0.218	0.143	65.4
PC-1		1.0	422.1	0.271	0.174	64.0
PC-2		2.0	399.4	0.240	0.164	68.4
PC-4		4.0	553.2	0.320	0.228	71.2
ZC-0.5	ZnCl2	0.5	296.6	0.156	0.120	76.9
ZC-1		1.0	382.7	0.199	0.160	80.3
ZC-2		2.0	977.2	0.453	0.398	87.9
ZC-4		4.0	1347.3	0.672	0.413	61.4
ZC-8		8.0	997.7	0.922	0.0967	10.5

^aThe nomenclature of the samples contains the identification of the activating agents (PH, PC and ZC for KOH, K₂CO₃ and ZnCl₂, respectively), followed by a number indicating the impregnation ratio.

Figure 2. Effects of impregnation ratio on (a) the BET surface area and (b) micropore volume of activated carbons.

Figure 3. (a) Micropore and (b) mesopore volume distribution of activated carbons with KOH activation.

Figure 4. (a) Micropore and (b) mesopore volume distribution of activated carbons with K₂CO₃ activation.

Figure 5. (a) Micropore and (b) mesopore volume distribution of activated carbons with ZnCl₂ activation.

Figure 6. (a) Micropore and (b) mesopore volume distributions of PH-0.5, PC-4, and ZC-4.

Figure 7. SEM graphs of (a, b) raw material and activated carbon samples: (c, d) PH-0.5, (e, f) PC-4, and (g, h) ZC-4.

Figure 8. FT-IR spectra of raw material, PH-0.5, PC-4, and ZC-4.

Table 3. Atomic percentage on the activated carbon surface from XPS analysis.

Sample	C (%)	O (%)	N (%)
PH-0.5	85.74	11.90	2.36
PC-4	81.43	16.79	1.78
ZC-4	89.83	7.34	2.83

Figure 9. Peak deconvolutions of the C1s: (a) PH-0.5, (c) PC-4, and (e) ZC-4, and O1s XPS spectra: (b) PH-0.5, (d) PC-4, and (f) ZC-4.

Table 4. The contribution of carbon and oxygen species.

B.E. (eV)	Group	PH-0.5	PC-4	ZC-4
C1s (%)
284.7 ± 0.1	Amorphous carbon, aromatics	69.88	62.53	65.80
286.1	Alcohols, phenols, ester groups, C-N	15.48	20.75	17.27
287.6	Keto groups	5.52	3.89	7.12
289.1	Carboxyl groups	3.75	6.36	3.10
290.6	Carbonate, carbon dioxide	5.37	6.46	6.71
O1s (%)
531.1	Keto groups	4.99	14.18	19.75
532.2 ± 0.2	Hydroxyls	25.77	32.91	15.87
533.2 ± 0.2	Ester groups	62.45	25.02	44.05
534.2	Carboxyl groups	5.25	21.56	17.51
536.1	Water or oxygen adsorbed	1.54	6.32	2.82

Figure 10. TG curves of PH-0.5, PC-4, and ZC-4.