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

Reaction of an aqueous slurry of an Mg2Al-NO3 layered double hydroxide with a four-fold excess of Na[Eu(EDTA)] gives a material which analyses for Mg0.68Al0.32(OH)(2)[Eu(EDTA)](0.10)(CO3)(0.11)(.) 0.66H(2)O. The interlayer spacing of the material is 13.8 Angstrom, corresponding to a gallery height of 9.0 Angstrom, which accords with the maximal dimensions (9-10Angstrom) 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. (C) 2004 Elsevier Inc. All rights reserved.