Incorporation of rare-earth ions in Mg–Al layered double hydroxides: intercalation with an [Eu(EDTA)] − chelate

Abstract

Reaction of an aqueous slurry of an Mg 2Al–NO 3 layered double hydroxide with a four-fold excess of Na[Eu(EDTA)] gives a material which analyses for Mg 0.68Al 0.32(OH) 2[Eu(EDTA)] 0.10(CO 3) 0.11·0.66H 2O. The interlayer spacing of the material is 13.8 Å, corresponding to a gallery height of 9.0 Å, which accords with the maximal dimensions (9–10 Å) of the anion in metal-EDTA complex salts as determined by single crystal X-ray diffraction. Geometrical considerations show that the charge density on the layered double hydroxide layers is too high to be balanced by intercalation of [Eu(EDTA)] − alone, necessitating the co-intercalation of carbonate ions which have a much higher charge density.