Solubility of dilute SO2 in binary system of polyethylene glycol 200 and dimethyl sulfoxide as a function of liquid composition and system's spectroscopic studies

In a previous work, the binary mixture of polyethylene glycol 200 (PEG) and dimethyl sulfoxide (DMSO) was used as a promising medium for absorption of SO2 (J. Chem. Eng. Data 2015, 60, 2135). As a continuation of the previous study, the solubility data of dilute SO2 in the binary mixture of PEG + DMSO were measured by isothermal gas-liquid equilibrium experiments at 298.15 K and 122.66 kPa with SO2 partial pressure below 128 Pa in the gas phase. The solubility of SO2 decreased gradually with increasing mass fraction of PEG in the mixtures. We found that the absorption process, which obeyed Henry's law within the given experimental conditions, was physical absorption, and Henry's constants were further calculated from solubility data. Furthermore, to obtain important information about the absorption mechanism, the inter-molecular interactions among SO2, PEG, and DMSO were investigated by UV, FTIR, and 1H NMR spectroscopic techniques. Spectral results showed that the interactions among SO2, PEG, and DMSO were resulted from both intermolecular hydrogen bonding and the O → S charge-transfer interaction.