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 center dot Mg-Al LDHs) are examined as a means of sequestering gaseous pollutants, such as HCl, NOx, and SOx, which are bound to afford X center dot Mg-Al LDH (X = Cl, SO4, or NO3). In view of the fact that the common regeneration method of CO3 center dot Mg-Al LDH (agitation in aqueous Na2CO3) poses a number of problems, we herein develop a new method of regenerating CO3 center dot Mg-Al LDH by treatment of X center dot 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. (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.