Reversible absorption of SO2 by amino acid aqueous solutions

Abstract

Six water-soluble amino acids (glycine, l-α-alanine, dl-alanine, β-alanine, proline and arginine) aqueous solutions were applied to remove SO2 from SO2–N2 system in this report. All the tested amino acids solutions were found to be excellent absorbents for SO2 removal, and SO2 saturation uptake of β-alanine solution was the highest under the same experimental conditions. The effects of amino acid concentration, SO2 concentration, absorption temperature, desorption temperature and initial pH value of the absorbent on the removal of SO2 were investigated with β-Ala solution. The experimental results showed that SO2 saturation uptake increased with the increase in β-alanine solution and SO2 concentration. Room temperature (20–30°C) was found to be optimal for SO2 absorption. Additionally the SO2 desorption capacity increased with increasing desorption temperature. The neutral environment pH value of 6.8 was found to be optimal for SO2 removal. Ten continuous absorption–desorption cycles showed that the absorbent had an excellent regeneration performance. 13C NMR and ultraviolet analyses offer ample evidence to speculate that the bonding between SO2 and β-alanine was not covalent but some weak interactive forces, such as dispersion force, induction force, dipole–dipole force and hydrogen bond.