1. Introduction {#s0005}
===============

With the rapid development of global economy, the development and utilization of coal have brought serious pollution to the environment, especially as the coal-fired power plant boiler emits large amounts of sulfur dioxide and nitrogen oxides (accounts for about 35%∼40% of the total SO2 and NOx emissions) to further aggravate the deterioration of the environment. For example, Shanghai and Beijing are two of the largest cities in China. Both cities have populations of over 10 million. These two urban areas have experienced a rapid increase in the use of vehicles, concurrent with large increases in energy consumption. Particulate pollution has become a major problem ([@b0155]). NOx and hydrocarbon with photochemical smog formation, cause serious harm to human health. In hazy weather during sports the human respiratory system changes direction, damaging the human respiratory system seriously ([@b0035]). Exposures to particulate matter with a diameter of 2.5um or less (PM2.5) may influence the risk of birth defects and make you allergic ([@b0015]).

Bamboo planting in China is very large, it is a kind of short growth cycle and timber fast biomass resource. Therefore, bamboo charcoal is a natural, renewable environmental protection material and functional material. Bamboo charcoal was created by heating bamboo at temperatures of 600--900 °C and then the charcoal itself was processed and mixed in with fabrics as part of the growing field of nanotechnology ([@b0015], [@b0150], [@b0020], [@b0005], [@b0025], [@b0050], [@b0125], [@b0145], [@b0010], [@b0030], [@b0095], [@b0100], [@b0105], [@b0070]). Bamboo charcoal had many positive qualities ([@b0015], [@b0150], [@b0020], [@b0005]). The fabric inhibited bacterial metabolism causing fewer allergic skin reactions than other fibers sterilized with antimicrobial agents. Because the trait was due to the highly porous structure of the bamboo fabric, it could absorb sulfur-based compounds, nitrogen-based compounds and so on ([@b0020], [@b0005], [@b0025], [@b0050], [@b0125], [@b0145], [@b0010]). What's more, bamboo charcoal, which contained potassium, calcium and other minerals, could cause adsorption and filtration of extractives, oil, and other substances ([@b0080], [@b0140], [@b0085], [@b0135], [@b0090], [@b0075], [@b0060], [@b0065], [@b0160], [@b0115]), that was beneficial for people's health. But so far, the bamboo charcoal in coal-fired flue gas pollution (sulfide, etc.) control in the field of study is less reported. In order to figure out the optimal adsorbtion condition and the intrinsic change of the bamboo charcoal, five chemicals were adsorbed by bamboo charcoal and were analyzed by FT-IR.

2. Materials and methods {#s0010}
========================

2.1. Materials {#s0015}
--------------

Bamboo charcoal, Na~2~SO~3~, Na~2~S~2~O~8~, Na~2~SO~4~, Fe~2~(SO~4~)~3~ and S were purchased from the market.

2.2. Methods {#s0020}
------------

Five kinds of pharmaceutical powder were weighed in amounts of 25 g. These powders and 4 g bamboo charcoal were put into the closed vessel. It was blasted in a closed vessel for 20 min, 40 min, 60 min, 80 min, 100 min and 120 min. Each bamboo charcoal was removed, dried, and weighed.

*FT-IR spectra*. FT-IR spectra of the above samples were obtained using a Thermo Scientific Nicolet iN10 FT-IR microscope as previously ([@b0040], [@b0095], [@b0100], [@b0105], [@b0120]).

3. Result and analysis {#s0025}
======================

Based on the above test, the results of adsorption were obtained and listed in [Table 1](#t0005){ref-type="table"}.

3.1. SC Effect {#s0030}
--------------

Based on [Table 1](#t0005){ref-type="table"}, Na~2~SO~3~'s adsorption capacity was 1.48 g/100 g, 0.25 g/100 g, 0.5 g/100 g, 1.52 g/100 g, 1.24 g/100 g, 1.5 g/100 g; Na~2~S~2~O~8~'s adsorption capacity was 1.75 g/100 g, 0.75 g/100 g, 0.74 g/100 g, 2 g/100 g, 2.02 g/100 g, 1.73 g/100 g; Na~2~SO~4~'s adsorption capacity was 2.25 g/100 g, 2.02 g/100 g, 2.02 g/100 g, 0.74 g/100 g, 1.49 g/100 g, 0.5 g/100 g; Fe~2~(SO~4~)~3~'s adsorption capacity was 1.49 g/100 g, 0.49 g/100 g, 1.01 g/100 g, 1.26 g/100 g, 1.24 g/100 g, 1.74 g/100 g; S's adsorption capacity was 2.76 g/100 g, 3.25 g/100 g, 4.47 g/100 g, 2.24 g/100 g, 4.47 g/100 g, 2.98 g/100 g for a blast time of 20 min, 40 min, 60 min, 80 min, 100 min and 120 min, respectively. It showed that adsorption capacity changed the regularity difference. It might be because rapid stirring lead to a small amount of five kinds of pharmaceutical powders on the surface of bamboo charcoal. The optimal blast time was 80 min of Na~2~SO~3~, 100 min of Na~2~S~2~O~8~, 20 min of Na~2~SO~4~, 120 min of Fe~2~(SO~4~)~3~ and 60 min or 100 min of S (see [Table 2](#t0010){ref-type="table"}).

3.2. FT-IR analysis {#s0035}
-------------------

FT-IR spectra were recorded to investigate the functional groups of bamboo charcoal during adsorption of Na~2~SO~3~, Na~2~S~2~O~8~, Na~2~SO~4~, Fe~2~(SO~4~)~3~ and S. Spectra of the samples were shown in supporting information [Figure 1](#f0005){ref-type="fig"}, [Figure 2](#f0010){ref-type="fig"}, [Figure 3](#f0015){ref-type="fig"}, [Figure 4](#f0020){ref-type="fig"}, [Figure 5](#f0025){ref-type="fig"}. In the spectrum of adsorption, the S---S stretch, H~2~O stretch, O---H stretch, CO stretch or CC stretch, NO~2~ stretch were observed at 3850 cm^−1^, 3740 cm^−1^, 3430 cm^−1^, 1630 cm^−1^ and 1530 cm^−1^, respectively \[28--32\].

For FT-IR spectra of Na~2~SO~3~, the transmissivity of the peaks at 3850 cm^−1^, 3740 cm^−1^, 3430 cm^−1^, 1630 cm^−1^ and 1530 cm^−1^ achieved the maximum for 20 min.

For FT-IR spectra of Na~2~S~2~O~8~, the transmissivity of the peaks at 3850 cm^−1^, 3740 cm^−1^, 3430 cm^−1^ and 1530 cm^−1^ achieved the maximum for 40 min, the transmissivity of the peaks at 1630 cm^−1^ achieved the maximum for 120 min.

For FT-IR spectra of Na~2~SO~4~, the transmissivity of the peaks at 3850 cm^−1^, 3740 cm^−1^ and 1530 cm^−1^ achieved the maximum for 40 min, the transmissivity of the peaks at 3430 cm^−1^ and 1630 cm^−1^ achieved the maximum for 60 min.

For FT-IR spectra of Fe~2~(SO~4~)~3~, the transmissivity of the peaks at 3850 cm^−1^, 3740 cm^−1^, 1630 cm^−1^ and 1530 cm^−1^ achieved the maximum for 120 min, the transmissivity of the peaks at 3430 cm^−1^ achieved the maximum for 100 min.

For FT-IR spectra of S, 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^ achieved the maximum for 100 min, the transmissivity of the peaks at 1630 cm^−1^ and 1530 cm^−1^ achieved the maximum for 40 min.

4. Conclusion {#s0040}
=============

Na~2~SO~3~'s, Na~2~S~2~O~8~'s, Na~2~SO~4~'s, Fe~2~(SO~4~)~3~'s and S's adsorption capacity were different for blast times of 20 min, 40 min, 60 min, 80 min, 100 min and 120 min, respectively. The optimal blast time was 80 min of Na~2~SO~3~, 100 min of Na~2~S~2~O~8~, 20 min of Na~2~SO~4~, 120 min of Fe~2~(SO~4~)~3~ and 60 min or 100 min of S.

FT-IR spectra showed that bamboo charcoal had the eight characteristic absorption band. And the S---S stretch, H~2~O stretch, O---H stretch, CO stretch or CC stretch, NO~2~ stretch were observed at 3850 cm^−1^, 3740 cm^−1^, 3430 cm^−1^, 1630 cm^−1^ and 1530 cm^−1^, respectively. For FT-IR spectra of Na~2~SO~3~, the transmissivity of the peaks at 3850 cm^−1^, 3740 cm^−1^, 3430 cm^−1^, 1630 cm^−1^ and 1530 cm^−1^ achieved the maximum for 20 min. For FT-IR spectra of Na~2~S~2~O~8~, the transmissivity of the peaks at 3850 cm^−1^, 3740 cm^−1^, 3430 cm^−1^ and 1530 cm^−1^ achieved the maximum for 40 min. For FT-IR spectra of Na~2~SO~4~, the transmissivity of the peaks at 3850 cm^−1^, 3740 cm^−1^ and 1530 cm^−1^ achieved the maximum for 40 min. For FT-IR spectra of Fe~2~(SO~4~)~3~, the transmissivity of the peaks at 3850 cm^−1^, 3740 cm^−1^, 1630 cm^−1^ and 1530 cm^−1^ achieved the maximum for 120 min. For FT-IR spectra of S, 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 1630 cm^−1^ and 1530 cm^−1^ achieved the maximum for 40 min. In these states, the number of the transmissivity of the maximum peaks is the largest.

This work was financially supported by the National 948 Plan (2014-4-38).

Peer review under responsibility of King Saud University.

![FT-IR spectra of bamboo charcoal during adsorption of Na~2~SO~3~.](gr1){#f0005}

![FT-IR spectra of bamboo charcoal during adsorption of Na~2~S~2~O~8~.](gr2){#f0010}

![FT-IR spectra of bamboo charcoal during adsorption of Na~2~SO~4~.](gr3){#f0015}

![FT-IR spectra of bamboo charcoal during adsorption of Fe~2~(SO~4~)~3~.](gr4){#f0020}

![FT-IR spectra of bamboo charcoal during adsorption of S.](gr5){#f0025}

###### 

Adsorption results.

  Blast time \[min\]   20     40     60     80     100    120
  -------------------- ------ ------ ------ ------ ------ ------
  Na~2~SO~3~           1.48   0.25   0.5    1.52   1.24   1.5
  Na~2~S~2~O~8~        1.75   0.75   0.74   2      2.02   1.73
  Na~2~SO~4~           2.25   2.02   2.02   0.74   1.49   0.5
  Fe~2~(SO~4~)~3~      1.49   0.49   1.01   1.26   1.24   1.74
  S                    2.76   3.25   4.47   2.24   4.47   2.98

###### 

Groups of bamboo charcoal during adsorption of Na~2~SO~3~, Na~2~S~2~O~8~, Na~2~SO~4~, Fe~2~(SO~4~)~3~ and S (%).

  Kind              Peak (cm^−1^)   Adsorption time (min)   Groups                                        
  ----------------- --------------- ----------------------- -------- ------ ------ ------ --------------- -------
  Na~2~SO~3~        1530            87.7                    56.9     51.3   44.3   56.9   52.2            NO~2~
  1630              87.0            59.3                    54.3     43.0   60.7   52.8   CO or CC        
  3430              81.7            55.1                    47.2     37.4   55.9   47.2   O---H stretch   
  3740              88.7            57.9                    48.5     43.7   57.8   52.1   H~2~O           
  3850              89.1            59.4                    49.6     43.7   59.5   52.7   S---S stretch   
                                                                                                          
  Na~2~S~2~O~8~     1530            84.7                    87.3     82.5   88.5   82.9   83.7            NO~2~
  1630              86.9            86.9                    86.8     87.2   87.4   88.1   CO or CC        
  3430              80.5            83.0                    82.6     78.5   78.0   80.7   O---H stretch   
  3740              81.3            88.7                    81.8     87.1   81.5   82.0   H~2~O           
  3850              84.4            89.0                    84.0     88.1   83.0   84.0   S---S stretch   
                                                                                                          
  Na~2~SO~4~        1530            85.5                    88.3     85.6   83.4   82.0   82.5            NO~2~
  1630              87.4            87.9                    88.1     86.0   84.8   86.4   CO or CC        
  3430              79.0            79.2                    80.5     78.8   77.1   80.0   O---H stretch   
  3740              83.2            86.5                    82.6     82.3   81.4   81.1   H~2~O           
  3850              85.0            87.5                    84.6     84.0   83.4   83.0   S---S stretch   
                                                                                                          
  Fe~2~(SO~4~)~3~   1530            81.2                    82.0     89.1   82.0   84.2   90.4            NO~2~
  1630              86.0            87.3                    86.5     87.3   86.6   88.3   CO or CC        
  3430              78.5            81.2                    78.4     81.2   82.8   78.8   O---H stretch   
  3740              79.3            81.2                    88.1     81.2   84.3   88.9   H~2~O           
  3850              81.5            83.4                    88.8     83.4   85.8   89.2   S---S stretch   
                                                                                                          
  S                 1530            90.5                    90.1     79.2   85.1   85.2   80.3            NO~2~
  1630              88.8            88.3                    84.0     86.4   88.1   83.7   CO or CC        
  3430              78.2            80.4                    76.1     78.3   83.4   73.8   O---H stretch   
  3740              88.4            89.2                    78.9     84.3   83.5   79.5   H~2~O           
  3850              88.7            89.4                    81.3     85.5   85.2   81.7   S---S stretch   
