Reversible removal of SO2 at low temperature by l-α-alanine supported on γ-Al2O3

l-α-Alanine was supported on γ-Al2O3 to remove SO2 in this work. The effects of SO2 concentration, water vapor and temperature on the removal of SO2 were investigated. The experiment results showed that the activity of l-α-alanine on SO2 removal increased significantly when supported on γ-Al2O3. SO2 saturation capacity increased with increase SO2 concentration, and kept about 57 mg/g when SO2 concentration exceeded 1.7%. Water vapor promoted SO2 removal and made SO2 saturation capacity increase greatly. SO2 saturation capacity decreased with increase in temperature, and room temperature was optimum. Raman spectroscopy analysis results revealed that SO2 weakly adsorbed onto the adsorbent mainly due to the interaction of SO2 and amino group via hydrogen bonds in the presence of water vapor. X-ray photoelectron spectroscopy (XPS) analysis results indicated that a small amount of SO2 strongly adsorbed onto the adsorbent by forming aluminum sulfite. However, the strong chemical adsorption sites were saturated after the first adsorption and would no longer adsorb SO2 afterwards. Ten continuous adsorption–desorption cycles showed that the adsorbent had an excellent regeneration performance.