Thermal decomposition of synthesized layered double hydroxides based upon Mg/(Fe,Cr) and carbonate
Thermal analysis complimented with evolved gas mass spectrometry has been applied to hydrotalcites of the pyroaurite-stitchtite series containing the carbonate anion prepared by co-precipitation and with varying Fe3+,Cr3+ trivalent cation ratio. The resulting materials were characterized by XRD, and TGA/DTG to determine the stability of the hydrotalcites synthesised. Hydrotalcites of formula Mg6(Cr0.8,Fe0.2)2(OH)16(CO3).xH2O, Mg6(Cr0.6,Fe0.4)2(OH)16(CO3).xH2O, Mg6(Cr0.4,Fe0.6)2(OH)16(CO3).xH2O and Mg6(Cr0.2,Fe0.8)2(OH)16(CO3).xH2O formed by intercalation with the carbonate anion as a function of Fe3+,Cr3+ trivalent cationic ratio show variation in the d-spacing attributed to the size of the cation.
The thermal decomposition of stitchtite-pyroaurite solid solution
a) removal of adsorbed water (< 100 degrees Celsius),
b) elimination of the interlayer structural water (100 – 150 degrees Celsius), and
c) the simultaneous dehydroxylation and decarbonation of the hydrotalcite framework (300 – 400 degrees Celsius).
The effect of replacement of Cr3+ by Fe3+ has no effect on the dehydroxylation temperature. The ion current curves provide evidence for the formation of Fe3+ and Cr3+ carbonates during dehydroxylation. Dehydroxylation results in the collapse of the hydrotalcite structure to that of its corresponding metal oxides, and results in the formation of spinels, including MgO, MgFe2O4, MgCr2O4, and MgFeAlO4.
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|Item Type:||Journal Article|
|Keywords:||hydrotalcite, stitchtite, pyroaurite, carbonate, X, ray Diffraction, thermal analysis|
|Subjects:||Australian and New Zealand Standard Research Classification > CHEMICAL SCIENCE (030000) > PHYSICAL CHEMISTRY (INCL. STRUCTURAL) (030600)
Australian and New Zealand Standard Research Classification > CHEMICAL SCIENCE (030000) > PHYSICAL CHEMISTRY (INCL. STRUCTURAL) (030600) > Catalysis and Mechanisms of Reactions (030601)
Australian and New Zealand Standard Research Classification > CHEMICAL SCIENCE (030000) > PHYSICAL CHEMISTRY (INCL. STRUCTURAL) (030600) > Colloid and Surface Chemistry (030603)
|Divisions:||Past > QUT Faculties & Divisions > Faculty of Science and Technology
Current > QUT Faculties and Divisions > Science & Engineering Faculty
|Copyright Owner:||Copyright 2008 Elsevier|
|Copyright Statement:||Reproduced in accordance with the copyright policy of the publisher.|
|Deposited On:||17 Oct 2008|
|Last Modified:||05 May 2014 23:44|
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