Oxidation of Cr(III) to Cr(VI) Species During the Thermal Decomposition Process of Zn/Cr-layered Double Hydroxide Carbonate.

The intermediates obtained from thermal decomposition of Zn/Cr-layered double hydroxide carbonates (Zr/Cr-LDH; Zn0.66Cr0.34(OH)2(CO3)0.170.57H2O) were studied by XRD, TPD, FT-IR, ESCA and chemical analyses. It was found that Cr(III) ions embedded originally in the hydroxide layers were oxidized to Cr(VI) species in the temperature range between 473 and 773 K where the layer structure was lost, and reduced again to Cr(III) in the spinel phase over 773 K.