Effect of time on the reconstruction of the Mg4Al2(OH)12CO3Æ3H2O layered double hydroxide in a Na2CO3 solution

The effect of time on the reconstruction of an Mg4Al2(OH)12CO3Æ3H2O LDH compound in a 0.1 M Na2CO3 solution have been investigated. It seems that the reconstruction phenomena of the Mg4Al2(OH)12CO3Æ3H2O LDH after a moderate thermal treatment is a very fast process, as it is already completed after 5 min of soaking in a 0.1 M Na2CO3 solution. Indeed, the weight of the reconstructed samples after the centrifuging-washing-drying cycle, as well as the carbon content of the reconstructed samples, remains constant whatever the time of contact between the solution and the mixed oxides issued from LDH. Powder XRD patterns are also similar for all the reconstructed samples without significant FWHM variations. SEM and TEM observations coupled with granulometric and BET measurements show that all the samples, both mixed oxides and reconstructed LDHs, are composed by aggregates of small plate-like particles (less than 100 nm) with a sub-hexagonal morphology but with different porosities.