Layered metal hydroxides containing calcium and their structural analysis

Abstract

Layered metal hydroxides (LMHs) containing calcium were synthesized by coprecipitation in solution having two different trivalent metal ions, iron and aluminum. Two mixed metal solutions (Ca 2+/Al 3+ and Ca 2+/Fe 3+ = 2/1) were added to sodium hydroxide solution and the final pH was adjusted to ∼11.5 and ∼13 for CaAl-and CaFe-LMHs. Powder X-ray diffraction (XRD) for the two LMH samples showed well developed (00l) diffractions indicating 2-dimensional crystal structure of the synthesized LMHs. Rietveld refinement of the Xray diffraction pattern, the local structure analysis through X-ray absorption spectroscopy, and thermal analysis also confirmed that the synthesized precipitates show typical structure of LMHs. The chemical formulae, Ca 2.04Al 1(OH) 6(NO 3)· 5.25H 2O and Ca 2.01Fe 1(OH) 6(NO 3)· 4.75H 2O were determined by inductively coupled plasma-atomic emission spectroscopy (ICP-AES). Particle morphology and thermal behavior for the synthesized LMHs were examined by field emission scanning electron microscopy and thermogravimetricdifferential scanning calorimetry.