Effects of activated carbon surface properties on the adsorption of volatile organic compounds

Figures & data

Table 1. Comparison of different adsorbate properties

	Adsorbate
Properties	Toluene	Acetone	Xylene
Formula	CH3C6H5	CH3COCH3	C6H4 (CH3)2
Molecular weight, g·mol^−1	92.14	58.08	106.16
Molecular diameter, nm	0.67	0.50	0.70
Polarity index	2.4	5.1	2.5
Boiling point, °C	110.6	56.2	139.12
Density at 25 °C, g·cm^−3	0.863	0.791	0.861
Vapor pressure at 25 °C, kPa	4.17	30.17	1.33

Figure 1. Experimental device: j drying bottle; k gas generator; l flow meter; m mixing chamber; n air pump; o adsorption bed; p thermostat; q gas chromatograph; r exhaust.

Table 2. Specific surface area and pore volume of AC

Adsorbent	S BET (m^2 ·g^−1)	S mic (m^2 ·g^−1)	S meso (m^2 ·g^−1)	νtotal (mL·g^−1)	νmic (mL·g^−1)
AC-1	951.5	617.4	334.1	0.4576	0.2741
AC-2	932.2	744.8	187.4	0.4318	0.3385
AC-3	947.7	704.3	243.4	0.4082	0.3156

Figure 2. SEM images of AC: (a) AC-1; (b) AC-2; (c) AC-3.

Figure 3. Micropore diameter distribution of AC.

Table 3. Chemical surface groups of AC (mmol·g⁻¹)

Adsorbent	Carboxyl	Lactones	Phenolic Hydroxyl	Total Acidic	Total Alkaline
AC-1	0.0536	0.0828	0.0472	0.1836	0.1546
AC-2	0.0893	0.0562	0.0339	0.1794	0.1386
AC-3	0.0714	0.0468	0.0570	0.1752	0.1573

Figure 4. Breakthrough curve of different adsorbates: (a) AC-1; (b) AC-2; (c) AC-3.

Table 4. Adsorption capacity of AC (g(100 g)⁻¹)

Adsorbent	Toluene	Acetone	Xylene
AC-1	28.16	14.75	31.45
AC-2	26.54	17.14	28.71
AC-3	27.18	18.36	30.26

Figure 5. Relationships between surface groups and adsorption capacity of AC: (a) carboxyl; (b) lactones; (c) phenolic hydroxyl; (d) total acidic group; (e) total alkaline group.

Figure 6. Relationships between adsorbate properties and adsorption capacity of AC: (a) molecular weigh; (b) molecular diameter; (c) polarity index; (d) boiling point; (e) density; (f) vapor pressure.

Table 5. Adsorption energy of AC (kJ·mol⁻¹)

Adsorbent	Toluene	Acetone	Xylene
AC-1	21.99	15.12	22.33
AC-2	22.22	15.27	22.57
AC-3	21.18	14.56	21.52

Figure 7. Curve of linear fit from the D-R equation and the nitrogen adsorption isotherm of AC: (a) AC-1; (b) AC-2; (c) AC-3.