Synthesis of Cd/(Al+Fe) layered double hydroxides and characterization of the calcination products

Layered double hydroxides (LDHs) containing Cd(II), Al(III), and Fe(III) in the brucite-like layers with different starting Fe/Al atomic ratios and with nitrate as counteranion have been prepared following the coprecipitation method at a constant pH value of 8. An additional Cd(II),Al(III)-LDH sample interlayered with hexacyanoferrate(III) ions has been prepared by ionic exchange at pH 9. The samples have been characterized by elemental chemical analysis, powder X-ray diffraction (PXRD), and FT-IR spectroscopy. Their thermal stability has been assessed by thermogravimetric and differential thermal analyses (TG-DTA) and mass spectrometric analysis of the evolved gases. The PXRD patterns of the solids calcined at 800 °C show diffraction lines corresponding to Cd(Al)O and spinel-type materials, which precise nature (CdAl₂O₄, Cd_1−xFe_2+xO₄, or Cd_xFe_2.66O₄) depends on location and concentration of iron in the parent material or precursor.