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

Monodispersed and uniform hexagonal thin plate-like magnesium-aluminum layered double hydroxide intercalated with CO32- (MgAl-CO32--LDH) is synthesized by an ethanol-water mediated solvothermal method. The maximum adsorption capacities of the as-synthesized and calcined MgAl - CO32- - LDH are 129.9 and 143.27 mg g(-1), respectively, which are higher than those of the other metal oxide nano-structures 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 - CO32- - LDH to 165.07 m(2) g(-1) for the calcined MgAl - CO32- - LDH, the as-synthesized and calcined hexagonal thin plate-like MgAl - CO32- - 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. (C) 2016 Elsevier B.V. All rights reserved.