Synthesis and Properties of Hexacyanoferrate Interlayered in Hydrotalcite. I. Hexacyanoferrate(II)

Hans Christian Bruun Hansen1 and Christian Bender Koch2
1 Chemistry Department, Royal Veterinary and Agricultural University Thorvaldsensvej 40, 1871 Copenhagen V, Denmark
2 Physics Department, Building 307, Technical University of Denmark DK-2800 Lyngy, Denmark

Abstract: Hydrotalcite (HT) interlayered with hexacyanoferrate(II) ions ([Mg4.62Al1.52(OH)12][(Fe(CN)6)0.30-(CO3)0.29]) has been synthesized from the carbonate-HT ([Mg4.52Al1.50(OH)12][(CO3)0.77]) through double ion exchange reactions, and the products have been studied by chemical and physical methods. Mössbauer spectroscopy shows that hexacyanoferrate(II) is held rigidly in the interlayer by electrostatic forces and is characterized by a singlet at 0.01 mm s-1 at 80 K. X-ray diffraction shows an increase of the basal spacing (d003) from 0.78 to 1.1 nm following exchange. Hexacyanoferrate(II) in the interlayer was oxidized to hexacyanoferrate(III) (up to 20%) by dioxygen on dehydrating the interlayer either by drying at 70°C or by washing with nonaqueous solvents like acetone or ethanol. The CN (ν6) band of hexacyanoferrate(II) and (III) is found at 2036 cm-1 and 2112 cm-1, respectively. The presence of an absorption band at 2080 cm-1, assigned to free cyanide anions in the interlayer, suggests that the hexacyanoferrate(II,III) complexes are not inert in the interlayer, cyanide ligands being substituted with either water or hydroxyls. Oxidation and ligand exchange of the hexacyanoferrate(II) are also indicated by Mössbauer spectroscopy.

Key Words: Anion exchange • FTIR spectroscopy • Hexacyanoferrate(II) • Hydrotalcite • Interlayer chemistry • Layered double hydroxides • Mössbauer spectroscopy

Clays and Clay Minerals; April 1994 v. 42; no. 2; p. 170-179; DOI: 10.1346/CCMN.1994.0420207
© 1994, The Clay Minerals Society
Clay Minerals Society (www.clays.org)