Synthesis and properties of CaAl-layered double hydroxides of hydrocalumite-type.

CaAl-layered double hydroxides (CaAl-LDHs) with various carbonate ion contents are essentially formed in Bayer liquors during the causticisation step in alumina production. Under well-defined conditions hemicarbonate is formed, which is beneficial in the process of retrieving both Al(OH) and OH ions. In the current work, CaAl-LDHs with various carbonate contents were prepared by the co-precipitation procedure and the products were dried in different ways. Structural information was obtained by a variety of methods, such as X-ray diffractometry (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). Elemental maps were constructed through a combination of SEM images and EDX measurements. The targeted CaAl-hydrocalumites were successfully synthesised. It was found that the method used for drying did not influence the basal spacing although it significantly altered the particle sizes. [ABSTRACT FROM AUTHOR]