Effect of trivalent cation on the physicochemical properties of cobalt containing anionic clays

A series of cobalt containing hydrotalcites having the general formula CoMCO(3)-HT where M = Al, Fe and Cr were synthesized by sequential and coprecipitation methods. The samples were primarily characterized by X-ray diffraction (XRD), infrared absorption studies, transmission electron microscopy-energy dispersive X-ray analysis (TEM-EDAX), thermogravimetry-differential scanning calorimetry (TG-DSC) and BET surface area measurements. The lattice parameters, FTIR stretching wavelengths for O-H bonds and thermal stability depended on the ionic radius of the trivalent M cation. Thermal calcination of these materials yielded a non-stoichiometric spinel-type phase whose crystallinity was also affected by the nature of the trivalent cation.