Regeneration of carbonate-intercalated Mg–Al layered double hydroxides (CO₃·Mg–Al LDHs) by CO₂-induced desorption of anions (X) from X·Mg–Al LDH (X = Cl, SO₄, or NO₃): A kinetic study

Carbonate-intercalated Mg–Al layered double hydroxides (CO₃·Mg–Al LDHs) are examined as a means of sequestering gaseous pollutants, such as HCl, NO_x, and SO_x, which are bound to afford X·Mg–Al LDH (X = Cl, SO₄, or NO₃). In view of the fact that the common regeneration method of CO₃·Mg–Al LDH (agitation in aqueous Na₂CO₃) poses a number of problems, we herein develop a new method of regenerating CO₃·Mg–Al LDH by treatment of X·Mg–Al LDH with gaseous CO₂ under neutral or alkaline conditions. The desorption of X is shown to follow the intraparticle diffusion model, featuring the diffusion of CO₃²⁻ in between LDH layers as the rate-determining step. Given the importance of LDHs for wastewater treatment and gaseous pollutant removal, the obtained results pave the way to the efficient utilization of these adsorbents and contribute to the development of next-generation decontamination techniques.