Reversible and Efficient Absorption of SO2 with Natural Amino Acid Aqueous Solutions: Performance and Mechanism

In previous research, we have found and reported for thefirst time that beta-alanine aqueous solution could be employed to efficiently separate SO2fromflue gas. However, the performance of most natural amino acids (AAs) on SO2absorptionand their interaction mechanisms are not fully understood. In this work, the performance of 20 natural AA aqueous solutions on SO2absorption from flue gas was systematically studied. The experimental data showed that monoamino AAs (MAAs) exhibited good absorption performance, especially glycine, of which thesaturation uptake of SO2reached 0.461 g/g. All the MAAs showedexcellent regeneration performance, while the polyamino AAs oflysine, arginine, and histidine performed poorly. Based on thecharacterization and analysis using Fourier transform infraredspectroscopy, Raman spectroscopy,13C-nuclear magnetic resonance, and the density-functional theory simulation, it was found that the interaction mechanism between MAA aqueous solutions represented by glycine and SO2is complex, including the hydrolysis ofSO2and the protonation of MAAs, the formation of hydrogen bonds between cationic MAAs and HSO3-, and the interaction between zwitterionic MAAs and SO2. In addition, cationic glycine could form a carboxylic acid dimer, which further interacted withHSO3-through hydrogen bonds.