Characteristics of activated carbon remove sulfur particles against smog.

Sulfur particles, which could cause diseases, were the main powder of smog. And activated carbon had the very adsorption characteristics. Therefore, five sulfur particles were adsorbed by activated carbon and were analyzed by FT-IR. The optimal adsorption time were 120 min of Na2SO3, 120 min of Na2S2O8, 120 min of Na2SO4, 120 min of Fe2(SO4)3 and 120 min of S. FT-IR spectra showed that activated carbon had the eight characteristic absorption of S-S stretch, H2O stretch, O-H stretch, -C-H stretch, conjugated C[bond, double bond]O stretch or C[bond, double bond]C stretch, CH2 bend, C-O stretch and acetylenic C-H bend vibrations at 3850 cm-1, 3740 cm-1, 3430 cm-1, 2920 cm-1, 1630 cm-1, 1390 cm-1, 1110 cm-1 and 600 cm-1, respectively. For Na2SO3, the peaks at 2920 cm-1, 1630 cm-1, 1390 cm-1 and 1110 cm-1 achieved the maximum at 20 min. For Na2S2O8, the peaks at 3850 cm-1, 3740 cm-1 and 2920 cm-1 achieved the maximum at 60 min. The peaks at 1390 cm-1, 1110 cm-1 and 600 cm-1 achieved the maximum at 40 min. For Na2SO4, the peaks at 3430 cm-1, 2920 cm-1, 1630 cm-1, 1390 cm-1, 1110 cm-1 and 600 cm-1 achieved the maximum at 60 min. For Fe2(SO4)3, the peaks at 1390 cm-1, 1110 cm-1 and 600 cm-1 achieved the maximum at 20 min. For S, the peaks at 1630 cm-1, 1390 cm-1 and 600 cm-1 achieved the maximum at 120 min. It provided that activated carbon could remove sulfur particles from smog air to restrain many anaphylactic diseases.

Introduction

Sulfur powder, is solid at room temperature, mainly from the exploitation of natural gas, oil and natural sulfur mine. Reactive sulfur in general, it can burn to sulfur dioxide, mixing with oxidants may explode, can react with the alkali metal (Zhang et al., 2010). An association between high levels of air pollutants and human disease has been known for more than half a century. Air pollution is composed of a heterogeneous mixture of compounds including ozone (O3), carbon monoxide (CO), sulfur dioxide (SO2), nitrogen oxides (NO), liquids, and particulate matter (PM). Substantial epidemiological evidence implicates air pollution, particularly sulfur dioxide (SO2) and PM, as a major risk factor with serious consequences on human health (Ahmadpour and Do, 1996, Chandra et al., 2009, Jumasiah et al., 2005). Of particular interest in PM are the particles that are ⩽10 μm in diameter (PM10) because they are the PM that ultimately enters the lungs, which may make the person allergic and sick. Globally, the number of people receiving TB therapy grew to 5.4 million in 2013, from 1.0 million enrolled in the DOTS (directly observed treatment, short-course) program in 1995 (Yuan et al., 2004). Sulfur powder and sulfur dioxide (SO2) often floated in air. If this was inhaled in vivo, it could cause diseases.

Activated carbon can use almost any type of carbon materials, such as wood (Zhang et al., 2010), sawdust, coal (Ding et al., 2002), shells (Yu et al., 2005), the stone of the fruit, bagasse, oil waste, waste plastics (Peng et al., 2014a), paper and leather scrap (Peng et al., 2013a), waste tires, urban waste, etc (Xiao et al., 2013). Activated carbon with highly developed porous structure and huge specific surface area (Peng et al., 2013b), good chemical stability and thermal stability, high mechanical strength and surface contains a variety of oxygen containing functional groups (Wang et al., 2013; Peng et al., 2013c). What’s more, activated carbon, which contained potassium, calcium and other minerals, could have adsorption and filtration of extractives, oil, sulfur-based compounds, other matters (Liu et al., 2008, Zhang et al., 2008, Ling et al., 1999, Bautista-Toledo et al., 1994). Therefore, activated carbon has a strong adsorption, and at the same time can make high dispersed catalyst load system, and as a reducing agent to participate in the reaction, reduces the reaction temperature (Wang et al., 2009). Activated carbon adsorption method is simple, no secondary pollution, can be very good for adsorption of sulfide in the air (Lin et al. 2015; Peng et al., 2014b, Peng et al., 2015, Sun et al., 2014, Wang et al., 2009) that was beneficial for people’s health. In order to figure out the optimal adsorb condition and the intrinsic change of the activated carbon, five chemicals were adsorbed by activated carbon and were analyzed by FT-IR.

Materials and methods

Materials

Activated carbon, Na2SO3, Na2S2O8, Na2SO4, Fe2(SO4)3 and S were purchased from the market.

Methods

Five kinds of pharmaceutical powders were weighed to 25 g, respectively. These powder and 4 g activated carbon were put into the closed vessel, respectively. It was left in closed vessel for 20 min, 40 min, 60 min, 80 min, 100 min and 120 min, respectively. Each activated carbon was removed, dried, weighed, respectively.

FT-IR spectra: FT-IR spectra of the above samples were obtained using a Thermo Scientific Nicolet iN10 FT-IR microscope as previously mentioned (Lin et al., 2015; Peng et al., 2014b, Peng et al., 2015, Sun et al., 2014, Wang et al., 2009).

Result and analysis

Based on the above test, the result of adsorption was obtained and is listed in Table 1.

Table 1

Adsorption results.

Adsorption time [min]	20	40	60	80	100	120
Na2SO3	5.01	9.23	9.68	11.9	11.9	16.3
Na2S2O8	5.94	6.93	12.4	17	15.3	17.7
Na2SO4	5.99	4.24	5.99	6.48	7.54	15
Fe2(SO4)3	7.21	6.27	8.93	12.1	13.3	16.8
S	9.5	10.2	11.6	13.6	16.8	19.5

SC effect

Based on Table 1, Na2SO3’s adsorption capacity was 5.01 g/100 g, 9.23 g/100 g, 9.68 g/100 g, 11.9 g/100 g, 11.9 g/100 g, 16.3 g/100 g; Na2S2O8’s adsorption capacity was 5.94 g/100 g, 6.93 g/100 g, 12.4 g/100 g, 17 g/100 g, 15.3 g/100 g, 17.7 g/100 g; Na2SO4’s adsorption capacity was 5.99 g/100 g, 4.24 g/100 g, 5.99 g/100 g, 6.48 g/100 g, 7.54 g/100 g, 15 g/100 g; Fe2(SO4)3’s adsorption capacity was 7.21 g/100 g, 6.27 g/100 g, 8.93 g/100 g, 12.1 g/100 g, 13.3 g/100 g, 16.8 g/100 g; S’s adsorption capacity was 9.5 g/100 g, 10.2 g/100 g, 11.6 g/100 g, 13.6 g/100 g, 16.8 g/100 g, 19.5 g/100 g for adsorption time of 20 min, 40 min, 60 min, 80 min, 100 min and 120 min, respectively. It showed that adsorption capacity changed at regularity difference. It might be because rapid stirring led to a small amount of five kinds of pharmaceutical powders on the surface of the activated carbon. The optimal adsorption times were 120 min of Na2SO3, 120 min of Na2S2O8, 120 min of Na2SO4, 120 min of Fe2(SO4)3 and 120 min of S (Table 2).

Table 2

Groups of activated carbon during adsorption of Na2SO3, Na2S2O8, Na2SO4, Fe2(SO4)3 and S (%).

Kind	Peak (cm−1)	Adsorption time (min)						Group
		20	40	60	80	100	120
Na2SO3	600	89.8	90.6	89.9	89.3	76.5	87.5	C—H
	1110	90.4	89.0	85.2	87.3	74.8	87.7	C—O stretch
	1390	90.6	89.6	89.3	89.1	78.1	89.3	CH2 bend
	1630	86.8	86.7	86.2	86.6	75.1	86.2	CO or CC
	2920	87.5	87.2	87.3	86.6	76.9	86.8	—C—H stretch
	3430	75.5	78.7	77.5	77.8	64.9	75.9	O—H stretch
	3740	89.2	88.0	87.7	89.3	75.7	90.4	H2O
	3850	89.4	88.7	88.6	89.6	76.5	90.3	S—S stretch
Na2S2O8	600	76.0	91.3	89.9	90.4	87.5	83.7	C—H
	1110	76.1	90.5	89.5	89.3	85.4	83.3	C—O stretch
	1390	76.1	90.5	89.8	89.9	86.7	85.5	CH2 bend
	1630	73.6	86.9	86.5	87.1	85.5	84.6	CO or CC
	2920	72.9	87.1	88.3	87.6	87.6	87.2	—C—H stretch
	3430	63.6	75.7	74.8	75.9	79.9	77.3	O—H stretch
	3740	72.1	89.2	89.9	89.1	88.7	88.8	H2O
	3850	72.5	89.4	89.5	89.3	89.2	89.0	S—S stretch
Na2SO4	600	91.9	88.0	94.1	75.6	70.5	80.7	C—H
	1110	90.0	87.0	92.7	74.4	72.1	81.5	C—O stretch
	1390	90.8	89.1	92.0	75.9	72.6	82.1	CH2 bend
	1630	86.7	86.0	87.9	73.6	70.7	79.7	CO or CC
	2920	87.3	85.4	88.0	73.5	72.4	81.4	—C—H stretch
	3430	75.2	75.0	77.2	64.4	65.1	72.4	O—H stretch
	3740	87.8	89.4	88.3	73.9	71.6	80.8	H2O
	3850	88.6	89.3	88.8	74.2	72.4	81.6	S—S stretch
Fe2(SO4)3	600	93.0	89.8	91.7	90.8	90.8	86.9	C—H
	1110	91.1	88.6	90.3	90.0	89.6	86.2	C—O stretch
	1390	91.6	90.1	91.0	90.2	91.4	88.8	CH2 bend
	1630	87.5	86.1	88.0	86.8	87.5	86.1	CO or CC
	2920	87.0	86.8	87.0	87.4	86.0	85.5	—C—H stretch
	3430	77.6	75.5	77.8	76.4	76.5	75.6	O—H stretch
	3740	87.5	88.0	89.8	89.6	89.5	90.1	H2O
	3850	88.3	88.7	89.6	89.6	89.6	89.9	S—S stretch
S	600	90.4	87.5	83.3	89.8	88.9	91.7	C—H
	1110	90.9	87.2	84.6	90.2	88.9	90.8	C—O stretch
	1390	90.2	87.4	84.6	90.3	89.5	90.3	CH2 bend
	1630	86.9	85.9	82.0	87.4	85.8	87.1	CO or CC
	2920	88.0	88.0	82.8	88.4	87.0	88.0	—C—H stretch
	3430	77.2	80.4	73.4	77.5	73.7	78.1	O—H stretch
	3740	89.2	88.7	84.5	90.2	89.3	88.4	H2O
	3850	89.3	89.3	84.3	90.0	89.4	89.1	S—S stretch

FT-IR analysis

FT-IR spectra were recorded to investigate the functional groups of activated carbon during adsorption of Na2SO3, Na2S2O8, Na2SO4, Fe2(SO4)3 and S. Spectra of the samples were shown in Figure 1, Figure 2, Figure 3, Figure 4, Figure 5. In the spectrum of adsorption, the S—S stretch, H2O stretch, O—H stretch, —C—H stretch, conjugated CO stretch or CC stretch, CH2 bend, C—O stretch and acetylenic C—H bend vibrations were observed at 3850 cm–1, 3740 cm–1, 3430 cm–1, 2920 cm–1, 1630 cm–1, 1390 cm–1, 1110 cm–1 and 600 cm–1, respectively. For FT-IR spectra of Na2SO3, the transmissivity of the peaks at 3850 cm–1 and 3740 cm–1 achieved the maximum for 120 min, the transmissivity of the peaks at 3430 cm–1 and 600 cm–1 achieved the maximum for 40 min, the transmissivity of the peaks at 2920 cm–1, 1630 cm–1, 1390 cm–1 and 1110 cm–1 achieved the maximum for 20 min.

Figure 1

FT-IR spectra of activated carbon during adsorption of Na2SO3.

Figure 2

FT-IR spectra of activated carbon during adsorption of Na2S2O8.

Figure 3

FT-IR spectra of activated carbon during adsorption of Na2SO4.

Figure 4

FT-IR spectra of activated carbon during adsorption of Fe2(SO4)3.

Figure 5

FT-IR spectra of activated carbon during adsorption of S.

For FT-IR spectra of Na2S2O8, the transmissivity of the peaks at 3850 cm–1, 3740 cm–1 and 2920 cm–1 achieved the maximum for 60 min, the transmissivity of the peaks at 3430 cm–1 achieved the maximum for 100 min, the transmissivity of the peaks at 1630 cm–1 achieved the maximum for 80 min, the transmissivity of the peaks at 1390 cm–1, 1110 cm–1 and 600 cm–1 achieved the maximum for 40 min.

For FT-IR spectra of Na2SO4, the transmissivity of the peaks at 3850 cm–1 and 3740 cm–1 achieved the maximum for 40 min, the transmissivity of the peaks at 3430 cm–1, 2920 cm–1, 1630 cm–1, 1390 cm–1, 1110 cm–1 and 600 cm–1 achieved the maximum for 60 min.

For FT-IR spectra of Fe2(SO4)3, the transmissivity of the peaks at 3850 cm–1 and 3740 cm–1 achieved the maximum for 120 min, the transmissivity of the peaks at 3430 cm–1 and 1630 cm–1 achieved the maximum for 60 min, the transmissivity of the peaks at 2920 cm–1 achieved the maximum for 80 min, the transmissivity of the peaks at 1390 cm–1, 1110 cm–1 and 600 cm–1 achieved the maximum for 20 min.

For FT-IR spectra of S, the transmissivity of the peaks at 3850 cm–1, 3740 cm–1 and 2920 cm–1 achieved the maximum for 80 min, the transmissivity of the peaks at 3430 cm–1 achieved the maximum for 40 min, the transmissivity of the peaks at 1630 cm–1, 1390 cm–1 and 600 cm–1 achieved the maximum for 120 min, the transmissivity of the peaks at 1110 cm–1 achieved the maximum for 20 min.

Conclusion

Na2SO3’s, Na2S2O8’s, Na2SO4’s, Fe2(SO4)3’s and S’s adsorption capacities were different for adsorption times of 20 min, 40 min, 60 min, 80 min, 100 min and 120 min, respectively. The optimal adsorption times were 120 min of Na2SO3, 120 min of Na2S2O8, 120 min of Na2SO4, 120 min of Fe2(SO4)3 and 120 min of S.

FT-IR spectra showed that activated carbon had the eight characteristic absorption bands. And the S—S stretch, H2O stretch, O—H stretch, —C—H stretch, conjugated CO stretch or CC stretch, CH2 bend, C—O stretch and acetylenic C—H bend vibrations were observed at 3850 cm–1, 3740 cm–1, 3430 cm–1, 2920 cm–1, 1630 cm–1, 1390 cm–1, 1110 cm–1 and 600 cm–1, respectively. For FT-IR spectra of Na2SO3 the transmissivity of the peaks at 2920 cm–1, 1630 cm–1, 1390 cm–1 and 1110 cm–1 achieved the maximum for 20 min. For FT-IR spectra of Na2S2O8, the transmissivity of the peaks at 3850 cm–1, 3740 cm–1 and 2920 cm–1 achieved the maximum for 60 min the transmissivity of the peaks at 1390 cm–1, 1110 cm–1 and 600 cm–1 achieved the maximum for 40 min. For FT-IR spectra of Na2SO4, the transmissivity of the peaks at 3430 cm–1, 2920 cm–1, 1630 cm–1, 1390 cm–1, 1110 cm–1 and 600 cm–1 achieved the maximum for 60 min. For FT-IR spectra of Fe2(SO4)3, the transmissivity of the peaks at 1390 cm–1, 1110 cm–1 and 600 cm–1 achieved the maximum for 20 min. For FT-IR spectra of S, the transmissivity of the peaks at 1630 cm–1, 1390 cm–1 and 600 cm–1 achieved the maximum for 120 min. In these states, the number of the transmissivity of the maximum peaks is the largest.