Desorption of Cl- from Mg-Al layered double hydroxide intercalated with Cl- using CO2 gas and water

Mg-Al layered double hydroxide intercalated with CO₃^2- (CO₃·Mg-Al LDH) is effective for treating HCl exhaust gas. HCl reacts with CO₃^2- in CO₃·Mg-Al LDH, resulting in the formation of Cl·Mg-Al LDH. We propose that CO₂ can be used for the desorption of Cl^- from Cl·Mg-Al LDH to regenerate CO₃·Mg-Al LDH. Herein, we studied the desorption of Cl^- from Cl·Mg-Al LDH by adding water to Cl·Mg-Al LDH and blowing CO₂ into it. We also analyzed the effects of temperature and water addition speed on the desorption of Cl^- from Cl·Mg-Al LDH. Our results show that the added water adhered to Cl·Mg-Al LDH and that CO₂ in the gaseous phase was dissolved in this adhered water, thus generating CO₃^2-. Therefore, anion exchange occurred between CO₃^2- and Cl^- in the Cl·Mg-Al LDH, thus desorbing Cl^-.