Preparation of Activated Carbons from Raw and Biotreated Agricultural Residues for Removal of Volatile Organic Compounds

Figures & data

Table 1. Elemental analysis of agricultural residue precursors (wt % on dry basis; n = 3)

Element	Raw BH	BTBH	RH	PS
C	66.08 ± 1.24	63.27 ± 0.97	43.97 ± 1.15	41.94 ± 0.68
H	1.41 ± 0.06	1.35 ± 0.06	6.37 ± 0.11	6.13 ± 0.20
N	4.85 ± 0.19	1.49 ± 0.06	2.83 ± 0.02	<0.1
S	<0.1	<0.1	<0.1	<0.1
O	25.00 ± 1.15	28.78 ± 0.84	34.03 ± 0.69	51.36 ± 1.41
Ash	2.66 ± 0.14	5.11 ± 0.09	12.80 ± 0.17	0.57 ± 0.07
Notes: ± SD.

Figure 1. Effect of activation time on the burnoff of ARACs.

Table 2. Physical properties of raw sample, char, and activated carbons from raw BH and BTBH (n = 3)

Sample	S BET (m^2 g^−1)	S micro (m^2 g^−1)	S micro/ S BET (%)	V t (cm^3 g^−1)	V micro (cm^3 g^−1)	V micro/ V t (%)
Raw (BH)	6.5 ± 1.6	–	–	–	–	–
Char (BH)	8.4 ± 0.4	–	–	0.020 ± 0.006	–	–
BH-30	594.6 ± 3.7	431.0 ± 6.8	72.5	0.307 ± 0.002	0.194 ± 0.003	63.2
BH-45	656.7 ± 3.9	434.9 ± 5.4	66.2	0.351 ± 0.002	0.196 ± 0.001	55.9
BH-60	679.7 ± 2.0	456.5 ± 5.1	67.2	0.365 ± 0.001	0.205 ± 0.002	56.1
BH-90	913.6 ± 40.3	458.7 ± 18.3	50.2	0.558 ± 0.016	0.202 ± 0.008	36.2
BH-120	941.5 ± 26.1	412.3 ± 5.9	43.8	0.632 ± 0.034	0.181 ± 0.002	28.6
BH-180	947.2 ± 5.1	279.6 ± 8.4	29.5	0.742 ± 0.008	0.120 ± 0.003	16.2
Raw (BTBH)	5.2 ± 0.8	–	–	–	–	–
Char (BTBH)	5.9 ± 1.3	–	–	0.014 ± 0.003	–	–
BTBH-10	203.2 ± 47.4	136.0 ± 33.7	66.9	0.120 ± 0.028	0.061 ± 0.016	50.6
BTBH-20	438.7 ± 41.3	326.5 ± 47.7	74.4	0.249 ± 0.025	0.145 ± 0.015	58.3
BTBH-30	469.4 ± 3.3	340.5 ± 7.1	72.6	0.286 ± 0.007	0.154 ± 0.001	53.8
BTBH-45	503.9 ± 4.2	319.8 ± 2.7	63.5	0.317 ± 0.004	0.153 ± 0.004	45.9
BTBH-60	600.2 ± 28.9	338.4 ± 10.4	56.4	0.435 ± 0.025	0.145 ± 0.001	35.1
BTBH-90	407.8 ± 24.4	225.6 ± 13.0	55.3	0.315 ± 0.014	0.099 ± 0.007	31.5

Table 3. Physical properties of raw sample, char, and activated carbons from rice husk and pistachio shell (n = 3)

Sample	S BET (m^2 g^−1)	S micro (m^2 g^−1)	S micro/S BET (%)	V t (cm^3 g^−1)	V micro (cm^3 g^−1)	V micro/V t (%)
Raw (RH)	0.9 ± 0.1	–	–	–	–	–
Char (RH)	14.4 ± 0.6	–	–	0.045 ± 0.008	–	–
RH-10	304.2 ± 2.3	232.9 ± 11.1	76.6	0.198 ± 0.002	0.103 ± 0.001	52.2
RH-20	356.7 ± 2.5	248.1 ± 9.5	69.6	0.246 ± 0.001	0.111 ± 0.001	45.0
RH-30	362.3 ± 7.7	225.7 ± 3.9	62.3	0.281 ± 0.003	0.103 ± 0.002	36.8
RH-60	335.0 ± 32.6	198.5 ± 8.5	59.3	0.304 ± 0.019	0.088 ± 0.005	29.0
RH-120	236.8 ± 23.9	119.7 ± 13.7	50.5	0.252 ± 0.014	0.052 ± 0.005	20.7
RH-180	186.3 ± 27.8	80.6 ± 15.9	43.2	0.210 ± 0.030	0.035 ± 0.006	16.8
RH-240	68.1 ± 5.4	23.0 ± 3.9	33.8	0.095 ± 0.004	0.001 ± 0.002	10.6
Raw (PS)	0.4 ± 0.1	–	–	–	–	–
Char (PS)	11.9 ± 2.4	–	–	0.016 ± 0.002	–	–
PS-10	261.4 ± 17.2	206.2 ± 19.4	78.9	0.133 ± 0.011	0.087 ± 0.007	65.7
PS-30	571.2 ± 17.6	495.5 ± 39.2	86.7	0.284 ± 0.009	0.221 ± 0.008	77.9
PS-60	726.4 ± 4.0	615.0 ± 11.9	84.7	0.366 ± 0.004	0.276 ± 0.002	75.5
PS-120	949.1 ± 51.9	752.7 ± 66.2	79.3	0.479 ± 0.034	0.337 ± 0.021	70.3

Figure 2. Pore diameter vs. pore volume for (1) micropore and (2) mesopore size distribution of the tested ARACs: (a) raw BH, (b) BTBH, (c) RH, and (d) PS.

Table 4. Elemental analysis of ARACs (moisture-ash-free basis; wt %)

Sample	C	H	N	O^a
BH-30	68.46	2.46	4.13	24.95
BH-45	69.01	2.61	3.52	24.86
BH-60	69.97	2.22	3.63	24.18
BH-90	67.28	2.80	3.19	26.73
BH-120	68.01	3.13	2.65	26.21
BH-180	69.04	1.60	1.85	27.51
BTBH-10	80.41	1.51	2.07	16.01
BTBH-20	80.13	1.48	2.38	16.01
BTBH-30	81.40	1.69	2.50	14.42
BTBH-45	79.04	1.50	1.83	17.63
BTBH-60	75.88	1.82	1.62	20.69
BTBH-90	74.12	1.23	1.38	23.28
RH-10	71.26	1.15	0.99	26.59
RH-20	70.74	1.92	0.92	26.43
RH-30	67.52	1.41	1.31	29.77
RH-60	66.97	1.83	0.52	30.67
RH-120	56.79	1.27	1.04	40.89
RH-180	53.51	5.73	1.04	39.72
RH-240	48.69	2.92	2.48	45.91
PS-10	81.62	1.07	0.14	17.17
PS-30	77.45	2.26	0.23	20.06
PS-60	75.27	2.55	0.15	22.02
PS-120	70.34	2.32	0.23	27.10
Notes: ^aO content (wt %) = 100 wt % - (C + H + N) wt %.

Table 5. Percent area of deconvoluted surface functional groups from the XPS C_1s peak between 280 and 294 eV for activated carbons from BTBH and RH

	Graphitic (C-C Bonding)	Hydroxyl	Carbonyl	Carboxyl	π-Electron Resonance
BTBH-10	66.7	26.0	3.97	1.26	2.01
BTBH-20	55.2	34.9	6.51	2.23	1.21
BTBH-30	66.7	25.4	5.43	1.31	1.14
BTBH-45	67.1	26.8	4.26	0.79	1.03
BTBH-60	59.4	25.8	11.4	2.74	0.58
BTBH-90	55.0	32.3	9.95	2.23	0.51
RH-10	46.6	35.9	11.1	4.92	1.48
RH-20	58.3	26.2	9.88	4.41	1.18
RH-30	53.3	26.0	13.8	5.39	1.50
RH-60	44.4	20.2	24.1	8.96	2.31
RH-120	37.5	18.8	34.3	7.75	1.55
RH-180	35.0	19.7	35.9	7.63	1.79
RH-240	27.3	17.2	43.5	9.53	2.56
Notes: Values given in percent of total C1s peak area.

Table 6. Freundlich, Langmuir, and DR parameters for toluene adsorption with BTBH-60 and CAC

	Temperature (ºC)	Freundlich			Langmuir			DR
		K	n	R ^2	q m (mg g^−1)	K L (ppmv^−1)	R ^2	W 0 (cm^3 g^−1)	E 0 (kJ mol^−1)	R ^2
BTBH-60	40	87.80	11.14	0.990	161.29	0.0442	0.999	0.2166	26.09	0.977
	50	84.29	11.07	0.970	151.52	0.0509	0.999	0.2156	25.67	0.965
	60	74.28	9.66	0.998	149.25	0.0415	0.999	0.2196	25.18	0.997
	70	65.43	8.45	0.994	144.93	0.0368	0.999	0.2281	24.38	0.996
	80	59.81	7.94	0.996	140.85	0.0313	0.998	0.2299	22.97	0.988
CAC	40	71.35	5.77	0.997	227.27	0.0229	0.998	0.3510	18.00	0.991
	50	54.15	4.98	0.997	208.33	0.0197	0.997	0.3546	17.71	0.999
	60	37.64	4.04	0.998	200.00	0.0140	0.993	0.3879	16.60	0.993
	70	37.50	4.46	0.996	172.41	0.0159	0.995	0.3340	17.69	0.991
	80	28.73	3.92	0.999	161.29	0.0130	0.995	0.3575	15.81	0.999

Figure 3. Adsorption isotherms of (a) BTBH-60 and (b) CAC.

Figure 4. Comparison of toluene adsorption capacities for BTBH-60 and CAC at various temperatures.