Absorption Properties and Spectroscopic Studies of Dilute Sulfur

Oct 23, 2012 - ABSTRACT: Isothermal gas−liquid equilibrium (GLE) data were reported at 298.15 K and 123.15 kPa for the absorption of dilute SO2 in ...
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Absorption Properties and Spectroscopic Studies of Dilute Sulfur Dioxide in Aqueous Glycerol Solutions Zhiqiang He, Jinrong Liu,* Lijun Li, Dawei Lan, and Jianbin Zhang College of Chemical Engineering, Inner Mongolia University of Technology, Huhhot 010051, China S Supporting Information *

ABSTRACT: Isothermal gas−liquid equilibrium (GLE) data were reported at 298.15 K and 123.15 kPa for the absorption of dilute SO2 in aqueous glycerol solutions, in which SO2 partial pressures are calculated in the range of (0 to 140) Pa. The GLE data were obtained with uncertainties within ±0.02 K for temperatures, ± 0.133 kPa for total pressures, ± 3.5% for SO2 concentration in the gas phase, and ±5% for SO2 concentration in the liquid phase. The measurements showed that the solubility of dilute SO2 in the system of glycerol (1) + water (2) increases with the increasing glycerol concentrations in the whole composition, and the solubility of SO2 in the system of glycerol (1) + water (2) presents an extreme minimum of 60.1 mg·L−1 at the mass fraction of w1 = 1.00 when SO2 in the gas phase is designed at ySO2 = 5 × 10−4. In addition, UV, FTIR (Fourier transform infrared), 1H NMR, and fluorescence spectra in the absorption processes of SO2 in the system of glycerol (1) + water (2) were investigated to present important absorption mechanism. Based on the spectral results obtained, the possibility of intermolecular hydrogen bond formation by hydroxyl oxygen atoms in the glycerol molecule with hydrogen atom in the H2O molecule and S···O interaction formation by hydroxyl oxygen atom in the glycerol molecule with sulfur atom in the SO2 molecule are discussed.

1. INTRODUCTION Sulfur dioxide (SO2), the main source of which is flue gas from the burning of fuels with high sulfur content from 0.03 mg·m−3 in the air up to several g·m−3 in a typical flue gas,1 is an important atmospheric pollutant in environmental protection. The SO2 control in flue gas from industrial processes is usually carried out by wet and dry scrubbing technologies where the disposal of waste products is giving rise to major problems due to the lack of suitable deposits. There are considerable interests in the solubility of SO2 because of its importance in industrial applications and in pollution control. Among the many procedures employed to desulfurize exhaust gases, organic solvents used as absorbents have been identified as an option among the regenerative processes2−6 because regeneration can be carried out by pressure reduction, by temperature increase, and by use of a carrier gas. Considering all these, our research group has paid great attention to the aqueous ethylene glycol (EG) and solutions of its similar compounds7−12 because of its favorable properties, such as low vapor pressure, low toxicity, high chemical stability, and low melting point. On the other hand, EG and polyethylene glycol (PEG) present native hydrogen bonding sites for flue gas desulfurization (FGD) so that the potential desorption characters are presented in the regenerative processes of desulfurizing solutions dissolving SO2. In previous works,7−12 Zhang and his co-workers found the solubility of SO2 with degree of polymerization of PEG. However, we were faced with the problem of whether the absorption of SO2 is related with the hydroxyl group or ether bonds. This work is mainly focused on providing gas−liquid equilibrium (GLE) data for SO2 + N2 mixtures with various glycerol + water solutions (GWs) at 298.15 K and 123.15 kPa to examine the effect of contents on the solubility of SO2 in © 2012 American Chemical Society

GWs and to present the GLE data and Henry’s law constants. Based on the data determined and calculated, the solubility of dilute SO2 in glycerol and EG and its similar compounds were compared. Furthermore, the present work investigates intermolecular hydrogen bonding and S···O interaction of GW with SO2 by UV, FTIR (Fourier transform infrared), 1H NMR, and fluorescence spectroscopic techniques. The results of this work can be used to provide important absorption mechanism for the design and operation of the absorption and desorption processes in flue gas desulfurization (FGD) with potential industrial application of aqueous glycerol solutions.

2. EXPERIMENTAL SECTION 2.1. Materials. The certified standard mixtures (SO2 + N2) with 5000 ppmv, purchased from the Beijing Gas Company (Beijing, China), were employed to determine the GLE data for the SO2 + N2 + glycerol + water systems. The analytical grade glycerol was purchased from Beijing Reagent Company (Beijing, China), which was used after drying over molecular sieves (type 4A) and decompression filtration before measurements. The density value of glycerol at 298.15 K was found to be 1.2580 g·cm−3, in good agreement with the literature.13 The purity of the final samples, as found by gas chromatograph, was better than 99.2%. Bidistilled water was used in this work. 2.2. Apparatus and Procedure. The experimental apparatus used in this work is shown in Figure 1 and based on Zhang’s work.11 Received: Revised: Accepted: Published: 13882

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province, China) with the accuracy of ±0.133 kPa and the total pressure was estimated to be ±0.11%. In the whole experiment, SO2 partial pressure was found in the range 0−140 Pa. First, 300 mL of solution was poured into the jacketed vessel (1) as the absorption solution; then, about 3000 mL of the SO2 + N2 mixture gas was poured into the experimental system and recycled by the gas recycle pump (4); the temperature and pressure in the experimental system are set at the experimental condition. Meanwhile, EG extracts SO2 from the SO2 + N2 mixture gas to reach the GLE situation, at this time, the concentrations of SO2 separately in the gas phase and in the liquid phase are determined as the GLE data. This performance was repeated with different SO2 + N2 mixtures, and the different GLE data were obtained. The sulfur(IV) concentration in the liquid phase (CSO2, mg/ L) was determined, once equilibrium was reached, by adding a known volume of solution from the vessel to a known volume of standard iodine solution. The excess iodine solution was back-titrated with the standard sodium thiosulfate solution.14 The overall uncertainty in the determination of the sulfur(IV) concentration was estimated to be ±0.6%. The concentrations of SO2 in the gas phase were determined by the Testo 350-Pro flue gas analyzer (Germany) with uncertainties within ±5%. UV−vis spectra were recorded on an UV-3150PC UV−vis spectrometer. FTIR spectra were recorded on a Bruker VECTOR22 FTIR spectrometer with a resolution of 1 cm−1 at 298 K in the range from 4000 cm−1 to 400 cm−1. The spectrometer possesses autoalign energy optimization and have a dynamically aligned interferometer, and it is fitted with a constringent ZnS pellet for the measurement of aqueous solution, an OPUS/IR operator, and an IR source. A baseline correction was made for the spectra that were recorded in air; then, 15 μL solution was used on the FTIR spectrometer in every measurement, and the thin layer of samples are less than 2 μm typical thickness. 1H NMR spectra were acquired using a Bruker ARX-400 nuclear magnetic resonance spectrometer and DMSO-d6 was used as the NMR solvent. Fluorescence spectra were acquired using an F-4500 fluorescence spectrophotometer employing a 500 W Hg−Xe high pressure lamp. All spectral

Figure 1. Sketch of the experimental apparatus: (1) jacketed vessel; (2) cold trap; (3) thermostatic bath; (4) gas circulatory pump; (5) flue gas analyzer; (6) regulating valve; (7) thermometer; (8) pressure meter; (9) SO2/N2 gas cylinder; (10) buffer; (11) absorption apparatus; (12) liquid circulatory pump.

The equipment is initially designed to determined GLE data based on the static-analytic method. In this work, SO2/N2 mixtures from the gas cylinder (9) are poured into the apparatus through switching the regulating valve K1 and valve K2 (6) and recycled through jacketed vessel (1), cold trap (2), and gas circulatory pump (4) for whole recycling process. Liquid temperatures were registered on a standard thermometer (7) at different points, and the temperatures do not vary more than 0.02 K. Total pressures were recorded on a pressure meter (8). In the present work, SO2 concentrations in the gas phase were determined by a Testo 350-Pro flue gas analyzer (5). After GLE experiments were performed, the mixture gas was discharged out by switching the regulating valve (6) and passing buffer (10) and absorption apparatus containing alkaline solution (11). 2.3. Experimental Procedure. Experimental data were measured at 298.15 K and kept at a constant temperature using CS501SYC thermostatted bath, which was purchased from Gongyi Meter Factory (Henan province, China) with a precision of ±0.02 K and inspected using an accurate thermometer purchased from Fuqiang Meter Factory (Hebei province, China) with the precision of ±0.02 K. In the present work, the system total pressures were inspected using a pressure gauge purchased from Fuqiang Meter Factory (Hebei

Figure 2. (a) GLE curves for glycerol (1) + water (2) + SO2 (3) +N2 (4): □, 100% glycerol; ○, 80% glycerol; Δ, 60% glycerol; ▽, 40% glycerol; ◊, 20% glycerol; ☆, H2O. (b) Solubility of SO2 in EGWs when SO2 concentration in the gas phase is designed at Φ1 = 5 × 10−4. 13883

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experiments of glycerol + H2O + SO2 were performed at normal temperature and pressure.

3. RESULTS AND DISCUSSION In this work, isothermal GLE data for the SO2 + N2 mixture gases with glycerol were determined at 298.15 K and the SO2 partial pressures in the gas phase up to 140 Pa. The experimental SO2 concentrations, yexp, are acquired by the Testo 350-Pro flue gas analyzer. 3.1. GLE Data for Glycerol + Water with Dilute SO2. A series of GLE experiments for the absorption of dilute SO2 in glycerol (1) + water (2) binary system were performed at 298.15 K and 123.15 kPa, and the data are listed in Table S1 (Supporting Information). From Table S1, the mass fraction of glycerol in GW (w1) was used in the actual operation, and glycerol and water were weighed using a Sartorius BS224S balance with a precision of ±0.0001 g to present accurate factual mass fraction of GWs. The GLE data were obtained with relative uncertainties within ±0.6% for SO2 concentration in the liquid phase and ±5% for SO2 concentration in the gas phase. In Table S1 (Supporting Information), ySO2 denotes the volume fraction of SO2 in the gas phase as ySO2 ≈ VSO2/(VSO2 + VH2O + VN2 + Vglycerol = VSO2/Vtotal. VSO2 and Vtotal denote respectively the partial volume of SO2 in the gas phase and the total gas volume, and CSO2 denotes the concentration of SO2 in the liquid phase. Partial pressure of SO2 (pSO2) in the gas phase is given by pSO2 = pyexp. The GLE curves of the SO2 absorption in various GWs at 298.15 K and 123.15 kPa are plotted in Figure 2a, and SO2 partial pressure is in the range 0−140) Pa. Solubility of SO2 in GWs is shown in Figure 2b when SO2 volume fraction in the gas phase is designed at ΦSO2 = 5 × 10−4. Figure 2 shows that the solubility of SO2 in the system of glycerol (1) + water (2) increased with the decreasing glycerol concentrations in the whole mass fraction range, and the solubility of SO2 in the GWs presented an extreme minimum at the mass fraction of w1 = 1.00 of 60.1 mg·L−1 when SO2 in the gas phase is designed at ΦSO2 = 5 × 10−4. Based on the GLE data determined, Henry’s law constants for GLE were acquired using the fitting way (Figures 3−8), and the constants are listed in Table S2 (Supporting Information). The HLC fitted from the experimental GLE is often expressed as the following15 HLC = Pg /Cw

Figure 3. Henry fitting for GLE data for glycerol (1) + water (2) + SO2 (3) + N2 (4). SO2 absorption capacity of 100% glycerol.

Figure 4. SO2 absorption capacity of 80% glycerol.

(1)

where Pg is the gas phase partial pressure (Pa) and Cw is the dissolved concentration (mol·m−3). At the same gas composition, the solubility of SO2 in pure PEG 400 presented an extreme maximum of 1330 mg·L−1,8 in pure DEG of 259 mg·L−1,9 and in pure EG of 128 mg·L−1.10 From these data, the absorption of SO2 can be related with the ether bonds but not with the hydroxyl group. 3.2. Spectral Properties. These results may be related to the intermolecular hydrogen bonding and interactions among glycerol, H2O, and SO2, and the similar interactions among ethylene glycol (EG) and its similar compounds, H2O, and SO2 had been published in the previous work.16−18 For research of the absorption mechanism of SO2 in GWs, FTIR, UV, and fluorescence spectroscopy are used to probe the intermolecular hydrogen bonding19,20 and interactions among molecules, since the FTIR spectra present precise information

Figure 5. SO2 absorption capacity of 60% glycerol.

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about water sensitive bonds21,22 and the glycerol characteristic vibrational properties; furthermore, FTIR is also advantageous to evaluate vibrational properties of bonds through very thin solution films, which are usually difficult to handle for the floating properties of solution. UV and fluorescence spectroscopy gives important information about various electronic transitions. Generally, FTIR,23,24 UV, and fluorescence spectroscopy offer the advantages to measure the association properties and hydrogen bonding capability and to assess interaction of alcohol with water by analyzing band shifts and changes. 3.2.1. Spectral Properties of Glycerol + H2O. The recorded FTIR spectra of glycerol + H2O are shown in Figure 9. In Figure 9a, the stretching vibrational band of hydroxyl group in GW is found to shift toward higher frequency, from 3342 cm −1 to 3382 cm −1 , with the increasing H 2 O concentration. The fact indicated that the interactions of glycerol with H2O are due to the vibrational property of hydroxyl group in glycerol. In Figure 9b, the bending vibrational frequency of H2O changes from 1657 cm−1 to 1650 cm−1, which has been reported to appear at 1645 cm−1 in H2O saturated low density polyethylene.21 The shift of H−O− H bending vibrational band indicates that the interactions of glycerol with H2O result from the property of hydrogen atom in H2O. Based on these results, the possible interactions between glycerol and H2O were due to the following, as the intermolecular hydrogen bonding and interaction of hydrogen atom in H2O with hydroxyl oxygen atom in glycerol by crosslinking, forming −O(H)···HOH···. The recorded UV spectra of glycerol + H2O are shown in Figure 10. Figure 10 shows that the electronic transitions blue-shift from 198 to 192 nm with increasing H2O concentration in GW. The absorption band is assigned to the n→σ* electronic transition of unshared electronic pair of hydroxyl oxygen atom in glycerol because the n→σ* electronic transition of H2O is often found at the vacuum ultraviolet region. With the increasing H2O concentration, intermolecular hydrogen-bonding interaction of hydroxyl oxygen atom in glycerol with hydrogen atom of H2O happened easily; however, the hydrogen bonding and interaction makes the n→σ* electronic transition of hydroxyl oxygen in glycerol become more difficulty. The present results show that the intermolecular hydrogen-bonding interaction in GW formed −O(H)···HOH···. Based on the IR and UV spectra and discussion, the interaction of glycerol with water can be contributed to the intermolecular hydrogen-bonding interaction in GW formed −O(H)···HOH···. 3.2.2. Spectral Properties of Glycerol + SO2. The recorded FTIR spectra of glycerol and glycerol + SO2 are shown in Figure 11. In Figure 11a, an asymmetry stretching band (Vas) of SO2 was observed at 1327 cm−1, which shows that the C−O−C asymmetry stretching band of glycrol was not affected by SO2. The absorption peak at 1327 cm−1, which is reported at 1344 cm−1 for SO2 in noncomplexing CCl4,25 can be attributed to the Vas of SO2 because the IR and Raman spectra indicate the following values for the fundamental frequencies: symmetry stretching band (Vs) = 1151.38 cm−1, δ = 517.69 cm−1, and Vas = 1361.76 cm−1.26 Meanwhile, the phenomenon that the Vas of SO2 shifts toward lower wavenumber than Vas = 1362 cm−1 can be due to the interaction of the sulfur atom in SO2 with other

Figure 6. SO2 absorption capacity of 40% glycerol.

Figure 7. SO2 absorption capacity of 20% glycerol.

Figure 8. SO2 absorption capacity of H2O.

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Figure 9. FTIR spectra of DEGW at various mass fractions: (a) 4000−2500 cm−1 and (b) 1800−1500 cm−1.

symmetry stretching band (Vas) of SO2 is presented at 1146 cm−1. In Figure 3b, a phenomenon was displayed. In the absence of SO2, the stretching vibrational band of hydroxyl in glycerol was observed at 3340 cm−1. In the presence of SO2, the band was changed into a peakier band. The phenomenon could be due to the fact that the addition of SO2 affects the original hydrogen bonding interaction among glycerol molecules and forms the new intermolecular hydrogen bonding of hydroxyl hydrogen atoms in glycerol with oxygen atoms in SO2 and intermolecular S···O interaction. The recorded UV spectra of glycerol and glycerol + SO2 are shown in Figure 12. In Figure 12, the characteristic bands of glycerol and SO2 were respectively identified, but no information on a complexing reaction could be obtained. From the figure, the absorption band of n→π* electron transition of oxygen atom in SO2 (Π43) is observed at 276 nm and the absorption intensity of the band increases with the increasing SO2 concentration. Another absorption band, which was mainly due to π→π* electron transition of sulfur atom in SO2 (Π43) and n→σ* electron transition of hydroxyl oxygen atom in glycerol, shifts from 198 to 230 nm, and the absorption intensity of the band increases. The shift results from the intermolecular hydrogen bond of oxygen atoms in SO2 with hydroxyl hydrogen atoms in glycerol

Figure 10. Absorption spectral changes with increasing H2O concentration at various GWs.

atoms. The SO2 molecule is known to be polar, and the sulfur atom is electropositive; thus, SO2 behaves as an electron acceptor by the sulfur atom, and its interaction with hydroxyl oxygen atom (electronegative) in glycerol should occur by the way of intermolecular S···O interaction. Furthermore, the

Figure 11. FTIR spectra of glycerol + SO2: (a) (1600−1000) cm−1 and (b) (4000−2250) cm−1. 13886

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Figure 12. UV spectra at various concentrations of glycerol + SO2.

and intermolecular S···O interaction. The bonding of oxygen atoms of SO2 with hydroxyl hydrogen atoms of glycerol results in the following two results: (1) the decreasing effects of oxygen atoms on sulfur atom of SO2 make the π→π* electron transition of sulfur atom in SO2 change easier; (2) the decreasing effects of hydroxyl hydrogen atoms in glycerol make the n→σ* electron transition of hydroxyl oxygen atom in glycerol change easier also. The recorded 1H NMR spectra of glycerol and glycerol + SO2 are shown in Figure 13. Figure 13a shows that the chemical shifts of hydroxyl hydrogen appears at δ = 4.508, 4.626, and 4.612 ppm (2H) in the 1H NMR spectrum of pure glycerol. However, with the increasing SO2 concentration in glycerol, because the bond length of O−H in glycerol molecules become longer and the electron cloud of hydroxyl hydrogen atoms in glycerol molecules become thinner, the signal changes into single peak and the chemical shift of hydrogen atoms in −OH groups shifts from δ = (4.640 to 4.612) ppm to 4.428 ppm in DMSOd6 (Figure 13). The phenomena can be due to the interaction of oxygen atoms in SO2 bonding with hydroxyl hydrogen atoms in glycerol increases shielding effect of hydroxyl hydrogen atoms in glycerol, so that the signal changes into single peak and the signal of chemical shift of hydroxyl hydrogen in glycerol move toward higher magnetic field. Stable state fluorescence spectra with selective excitation of glycerol with increasing SO2 concentration were recorded and are shown in Figure 14. Upon excitation at 205 nm, where the n→σ* electron transition of oxygen atom of glycerol absorbs, strong fluorescence with emission positions at 350 nm were observed. The fluorescence intensity of the σ*→n electron transition of oxygen atom of glycerol decreases with increasing SO2 concentration. The phenomena can be due to the intermolecular interaction of the oxygen atom in glycerol with SO2 as the formation of S···O interaction. According to the IR, UV, 1H NMR, and fluorescence spectral results, it is expected that glycerol bonds with SO2 by the intermolecular hydrogen bonds of −CH2CH2OH···OSO··· and intermolecular −CH2CH2O(H)···(O)S(O)··· interaction. 3.2.3. Spectral Properties of GW + SO2. The recorded FTIR spectra of H2O and H2O + SO2 are shown in the previous work.18 From the spectra, two special stretching bands are observed at 1329 cm−1 and 1150 cm−1, which can be attribute to the Vas and Vs of SO2.26

Figure 13. 1H NMR spectra of glycerol in the presence and absence of SO2: (a) 1H NMR spectrum of glycerol, (b) 1H NMR spectrum of glycerol after 5 min ventilation of SO2, and (c) 1H NMR spectrum of glycerol after 10 min ventilation of SO2.

The recorded IR spectra of w1 = 0.60 GW and w1 = 0.60 GW + SO2 are shown in Figure 15. In Figure 15a, the stretching band at 1329 cm−1 was observed. Meanwhile, the phenomenon that the Vas of SO2 shifts lower wavenumber than Vas = 1362 cm−1 can be due to the interaction of the sulfur atom in SO2 with hydroxyl oxygen atom in glycerol by the way of S···O interaction. In Figure 15b, in the absence of SO2, the stretching vibrational band of hydroxyl in glycerol was observed at 3378 13887

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Figure 14. Fluorescence emission spectra of glycerol + SO2.

Figure 16. UV spectra at various concentrations of 60% glycerol + SO2.

cm−1 and the band was broad; in the presence of SO2, the band was changed into a more peak-like band. The phenomenon can be due to the new hydrogen bonding of hydroxyl hydrogen in glycerol with oxygen in SO2 and intermolecular S···O interaction. In Figure 16, the absorption band of n→π* electron transition of oxygen atom in SO2 is observed at 276 nm and the absorption intensity of the band increases with increasing SO2 concentration. Meanwhile, the special absorption band red shifts from 197 to 211 nm, and the absorption intensity of band increases, also. The results show the π→π* electron transition of SO2 and n→σ* electron transition of oxygen atom of glycerol in w1 = 0.60 GW with increasing SO2 concentration. These results suggest the hydrogen bonding and interaction between hydrogen atoms in glycerol molecules and oxygen atoms in SO2 molecules occurred. When such hydrogen bonds are formed, hydroxyl hydrogen atoms in the glycerol molecules are attracted by the oxygen atoms in SO2 and the bond length between the hydrogen atom and the oxygen atom in glycerol molecules is elongated. Such an interaction should decrease the double bond character of SO2 and so induce a lower absorption frequency, as is observed. From the FTIR spectral results recorded on the aqueous solution, one can suppose that the glycerol−SO2 complex is the less stable, as suggested by its

lower downshifted frequency and its stronger desorption capacity. Such a shift observed in FTIR spectra was attributed to the interactions of glycerol with SO2. Comparing the spectra of w1 = 0.60 GW + SO2 and w1 = 0.60 GW, it is observed that the H−O−H bending band and the characteristic bands of glycerol are not obviously shifted in the mixture under the influence of SO2 (Figure 15). The constant H−O−H bending band in the absorption processes of SO2 is mainly due to the hydrogen interaction of glycerol and SO2 rather than the reaction of water and SO2. Meanwhile, FTIR results support that there are S···O interaction of the sulfur atom in SO2 with hydroxyl oxygen atom in glycerol. The hydrogen bonding and interaction of SO2 with glycerol is very useful to desorb SO2 from GWs by pressure reduction, by temperature rise, and by use of a carrier gas in following work. However, these results only give us the present information, the exact molecular mechanism of interactions requires further investigation.

4. CONCLUSION This paper presents the results of fundamental investigations on isothermal GLE data of various aqueous glycerol solutions with SO2, which were determined as a function of composition at 298.15 K and 123.15 kPa. The GLE data show that the

Figure 15. FTIR spectral at various SO2 concentrations in 60% glycerol solution: (a) 1800−1100 cm−1 and (b) 4000−2250 cm−1. 13888

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of the kinetics of the liquid phase reaction. Chem. Eng. Sci. 2002, 57, 4883−4893. (6) De Kermadec, R.; Lapicque, F.; Roizard, D.; Roizard, C. Characterization of the SO2−N−formylmorpholine complex: Application to a regenerative process for waste gas scrubbing. Ind. Eng. Chem. Res. 2002, 41, 153−163. (7) Zhang, J. B.; Liu, L. H.; Huo, T. R.; Liu, Z. Y.; Zhang, T.; Wei, X. H. Absorption of dilute sulfur dioxide in aqueous polyethylene glycol 400 solutions at T = 308.15 K and p = 122.60 kPa. J. Chem. Thermodyn. 2012, 43, 1463−1467. (8) Zhang, J. B.; Han, F.; Zhang, P. Y.; Chen, G. H.; Wei, X. H. Gas− liquid equilibrium data for mixture gas of sulfur dioxide + nitrogen with poly(ethylene glycol) aqueous solutions at 298.15 K and 122.61 kPa. J. Chem. Eng. Data 2010, 55, 959−961. (9) Zhang, J. B.; Chen, G. H.; Zhang, P. Y.; Han, F.; Wang, J. F.; Wei, X. H. Gas−liquid equilibrium data for mixture gas of sulfur dioxide + nitrogen with diethylene glycol + water at 298.15 K and 123.15 kPa. J. Chem. Eng. Data 2010, 53, 1446−1448. (10) Zhang, J. B.; Zhang, P. Y.; Han, F.; Chen, G. H.; Deng, R. H.; Wei, X. H. Gas−liquid equilibrium data for mixture gas of sulfur dioxide/nitrogen with ethylene glycol aqueous solutions at 298.15 K and 123.15 kPa. J. Chem. Eng. Data 2008, 53, 2372−2374. (11) Zhang, J. B.; Zhang, P. Y.; Chen, G. H.; Han, F.; Wei, X. H. Gas−liquid equilibrium data for mixture gas of sulfur dioxide/nitrogen with ethylene glycol at temperatures from 298.15 to 313.15 K under low pressures. J. Chem. Eng. Data 2008, 53, 1479−1485. (12) Wei, X. H.; Zhang, J. B.; Zhang, P. Y.; Zhang, L. W.; Li, X. B.; Wan, M. J. Removal of SOx from flue gas by ethylene glycol. CN Patent No. 101053746, 2007. (13) Spangler, J.; Davies, E. Freezing points, densities, and refractive indexes of system glycerol−ethylene glycol−water. Ind. Eng. Chem. Anal. Ed. 1943, 15 (2), 96−99. (14) Rodriguez-Sevilla, J.; Alvarez, M.; Liminana, G.; Diaz, M. C. Dilute SO2 absorption equilibria in aqueous HCl and NaCl solutions at 298.15 K. J. Chem. Eng. Data 2002, 47, 1339−1345. (15) Bamford, H. A.; Poster, D. L.; Baker, J. E. temperature dependence of Henry’s law constants of thirteen polycyclic aromatic hydrocarbons between 4 °C and 31 °C. Environ. Toxicol. Chem. 1999, 18, 1905−1912. (16) Zhang, J. B.; Li, Q.; Guo, Z. H.; Li, K. X.; Xu, M. D.; Zhang, N.; Zhang, T.; Wei, X. H. Spectral investigation of intermolecular hydrogen bonding and S···O interaction in diethylene glycol + H2O + SO2 systems. Ind. Eng. Chem. Res. 2011, 50, 674−679. (17) Zhang, J. B.; Han, F.; Wei, X. H; Shui, L. K.; Gong, H.; Zhang, P. Y. Spectral studies of hydrogen bonding and interaction in the absorption processes of sulfur dioxide in poly(ethylene glycol) 400 + water binary system. Ind. Eng. Chem. Res. 2010, 49, 2025−2030. (18) Zhang, J. B.; Zhang, P. Y.; Han, F.; Chen, G. H.; Zhang, L. W.; Wei, X. H. Hydrogen bonding and interaction in the absorption processes of sulfur dioxide in ethylene glycol + water binary desulfurization system. Ind. Eng. Chem. Res. 2009, 48, 1287−1291. (19) Ivopoulos, P.; Sotiropoulou, M.; Bokias, G.; Staikos, G. Watersoluble hydrogen-bonding interpolymer complex formation between poly (ethylene glycol) and poly(acrylic acid) grafted with poly(2acryla-mido-2-methylpropanesulfonic acid). Langmuir 2006, 22, 9181−9186. (20) Schofield, D. P.; Lane, J. R.; Kjaergaard, H. G. Hydrogen bonded OH-stretching vibration in the water dimer. J. Phys. Chem. A 2007, 111, 567−572. (21) Lasgabaster, A.; Abad, M. J.; Barral, L.; Ares, A. FTIR study on the nature of water sorbed in polypropylene (PP)/ethylene alcohol vinyl (EVOH) films. Eur. Polym. J. 2006, 42, 3121−3132. (22) Dharmalingam, K.; Ramachandran, K. P. FTIR and dielectric studies of molecular interaction between alkyl methacrylates and primary alcohols. Physica. B 2006, 4, 1−5. (23) Palombo, F.; Paolantoni, M.; Sassi, P.; Morresi, A.; Cataliotti, R. S. Spectroscopic studies of the ‘‘free’’ OH Stretching bands in liquid alcohols. J. Mol. Liq. 2006, 125, 139−146.

solubility of SO2 in the system glycerol (1) + water (2) increased with decreasing glycerol concentration in the whole mass fraction range, and the solubility of SO2 in the system glycerol (1) + water (2) presented an extreme minimum at the mass fraction of w1 = 1.00 of 60.1 mg·L−1 when SO2 in the gas phase is designed at ΦSO2 = 5 × 10−4. Compared with the previous data, the absorption of SO2 can be related with the ether bonds but not with the hydroxyl group. GW presents native hydrogen bonding sites for the absorption of SO2 so that the absorption and desorption properties of SO2 can be related to hydrogen bonding and intermolecular S···O interaction among molecules. Present results show that the possible interactions in GW result from the following way as hydrogen bonding and interaction of hydrogen atom in H2O with hydroxyl oxygen atom in glycerol by cross-linking as the formation of −CH2CH2O(H)···HOH···. In addition, in the absorption processes of SO2 in pure glycerol or GWs, the spectral analyses suggest that SO2 can interact with glycerol by hydrogen bonds as −CH2CH2O−H···OSO···, and intermolecular S···O interaction of hydroxyl oxygen atom in glycerol with sulfur atom in SO2.

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ASSOCIATED CONTENT

S Supporting Information *

Two additional tables. This material is available free of charge via the Internet at http://pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Author

*Tel.: +86-471-6576661. Fax: +86-471-6503298. E-mail: liujr@ imut.edu.cn. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by foundation of the national natural science foundation of China (21166017), the research fund for the doctoral program of higher education of China (20111514120002), the natural science foundation of Inner Mongolia Autonomous Region (2011BS0601, China), Yongfeng Boyuan Industry Co., Ltd. (Jiangxi province, China), Inner Mongolia Autonomous Region’s Educational Commission (NJZZ11068), the Inner Mongolia talented people development Fund, and the school scientific research fund (ZD201004, Inner Mongolia university of Technology, China).

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REFERENCES

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