Mg-Al layered double hydroxide intercalated with CO

3

2-

(CO

3

·Mg-Al LDH) is effective for treating HCl exhaust gas. HCl reacts with CO

3

2-

in CO

3

·Mg-Al LDH

resulting in the formation of Cl·Mg-Al LDH. We propose that CO

2

can be used for the desorption of Cl

-

from Cl·Mg-Al LDH to regenerate CO

3

·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 CO

2

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 CO

2

in the gaseous phase was dissolved in this adhered water

thus generating CO

3

2-

. Therefore

anion exchange occurred between CO

3

2-

and Cl

-

in the Cl·Mg-Al LDH

thus desorbing Cl

-

.