Different dye removal mechanisms between monodispersed and uniform hexagonal thin plate-like MgAl–CO32--LDH and its calcined product in efficient removal of Congo red from water

Abstract Monodispersed and uniform hexagonal thin plate-like magnesium-aluminum layered double hydroxide intercalated with CO 3 2− (MgAl–CO 3 2− -LDH) is synthesized by an ethanol–water mediated solvothermal method. The maximum adsorption capacities of the as-synthesized and calcined MgAl − CO 3 2 − − LDH are 129.9 and 143.27 mg g −1 , respectively, which are higher than those of the other metal oxide nanostructures reported to date. More importantly, although N 2 adsorption–desorption analysis indicates that the BET surface area changed from 24.74 m 2  g −1 for the as-synthesized MgAl − CO 3 2 − − LDH to 165.07 m 2  g −1 for the calcined MgAl − CO 3 2 − − LDH , the as-synthesized and calcined hexagonal thin plate-like MgAl − CO 3 2 − − LDH structures show similar adsorption capacity of Congo red (CR) from aqueous solution. The adsorption mechanism for the as-prepared LDH is anion exchange while adsorption mechanism for the calcined LDH is reconstruction. Our study opens a new insight for understanding and preparing high-performance adsorbents for organic dye removal.