Solubilities and Thermodynamic Properties of SO2 in Ionic Liquids

Task-specific ionic liquids (TSILs) have been experimentally demonstrated to absorb more sulfur dioxide (SO2) than normal ILs from gas mixtures with low SO2 concentrations; however, the differences of SO2 solubilities in the two kinds of ILs at given temperatures and pressures have not been studied systematically. Moreover, the mechanism of the interaction between SO2 and ILs still remains unclear. In this work, the solubilities of SO2 in TSILs (1,1,3,3-tetramethylguanidinium lactate and monoethanolaminium lactate) and normal ILs (1-butyl-3-methylimidazolium tetrafluoroborate and 1-butyl-3-methylimidazolium hexafluorophosphate) were determined. The solubilities of SO2 are correlated by a modified Redlich−Kwong equation of state (RK EoS). The chemical absorption and physical absorption are differentiated, and the absorption mechanism has been proposed with the aid of the modified RK EoS. SO2 absorption capacity in TSILs is contributed from both chemical interaction and physical interaction. Two TSIL molecu...