Physical and chemical interactions between Mg:Al layered double hydroxide and hexacyanoferrate

The physical and chemical interactions of ferrocyanide (potassium and ammonium salts) and ferricyanide (potassium salt) with Mg:AI layered double hydroxides (LDH) (having Mg:AI ratios of 2 and 3) are investigated using powder XRD and FTIR spectroscopy. Physically, the potassium ferricyanide is shown to intercalate with a small local field deformation similar to that seen for hexacyanocobaltate (III) in similar materials. Chemically, the reduction of ferricyanide to ferrocyanide upon intercalation is confirmed. Physical interactions of ferrocyanide with 3:1 LDH are shown spectroscopically to include the possible generation of anions in differing environments. Chemically, ferrocyanide is shown to generate cubic ferrocyanides (of the type M2MgFe(CN)(6), where M = K+ or NH4+) under conditions where free Mg2+ is likely present in solution, namely, solutions with a pH lower than similar to7.5. It is shown that the reported 2112-cm(-1) band found in some chemically altered LDH ferrocyanide is indeed due to interlayer ferricyanide, but that the 2080 cm(-1) band is due to the cubic material. (C) 2001 Academic Press.