Infrared and Raman study of interlayer anions CO2-3, NO-3,SO2-4, and CIO-4 in Mg/Alhydrotalcite

Kloprogge, J. Theo, Wharton, David, Hickey, Leisel, & Frost, Ray L. (2002) Infrared and Raman study of interlayer anions CO2-3, NO-3,SO2-4, and CIO-4 in Mg/Alhydrotalcite. American Mineralogist, 87(5-6), pp. 623-629.

Abstract

The difference in the local environment of CO3 2–, NO3 –, SO4 2–, and ClO4 – in Mg/Al-hydrotalcite compared to the free anions was studied by infrared and Raman spectroscopy. In comparison to free CO3 2– a shift toward lower wavenumbers was observed. A band around 3000–3200 cm–1 has been attributed to the bridging mode H2O-CO3 2–. The IR spectrum of CO3 – hydrotalcite clearly shows the split n3 band around 1365 and 1400 cm–1 together with weak n2 and n4 modes around 870 and 667 cm–1. The n1 mode is activated and observed as a weak band around 1012 cm–1. The Raman spectrum shows a strong n1 band at 1053 cm–1 plus weak n3 and n4 modes around 1403 and 695 cm–1. The symmetry of the carbonate anions is lowered from D3h to C2s resulting in activation of the IR inactive n1 mode around 1050–1060 cm–1. In addition, the n3 shows a splitting of 30–60 cm–1. Although NO3-hydrotalcite has incorporated some CO3 2– the IR shows a strong n3 mode at 1360 cm–1 with a weak band at 827 cm–1, and the n4 band is observed at 667 cm–1, although it is largely obscured by the hydrotalcite lattice modes. The Raman spectrum shows a strong n1 mode at 1044 cm–1 with a weaker n4 band at 712 cm–1. The n3 mode at 1355 cm–1 is obscured by a broad band due to the presence of CO3 2–. The symmetry of NO3 – did not change when incorporated in hydrotalcite. The IR spectrum of SO4-hydrotalcite shows a strong n3 at 1126, n4 at 614 and a weak n1 mode at 981 cm–1. The Raman spectrum is characterized by a strong n1 mode at 982 cm–1 plus medium n2 and n4 bands at 453 and 611 cm–1; n3 cannot be identified as a separate band, although a broad band can be seen around 1134 cm–1. The site symmetry of SO4 2– is lowered from Td to C2v. The distortion of ClO4 – in the interlayer of hydrotalcite is reflected in the IR spectrum with both n3 and n4 bands split around 1096 and 1145 cm–1 and 626 and 635 cm–1, respectively. A weak n1 band is observed at 935 cm–1. The Raman spectrum shows a strong n1 mode at 936 cm–1 plus n2 and n4 bands at 461 and 626 cm–1, respectively. A n3 mode cannot be clearly recognized, but a broad band is visible around 1110 cm–1. These data indicative a lowering of symmetry from Td to Cs.

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ID Code: 9873
Item Type: Journal Article
Refereed: Yes
Additional Information: For more information, please refer to the journal’s website (see hypertext link) or contact the author.
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ISSN: 0003-004X
Divisions: Past > QUT Faculties & Divisions > Faculty of Science and Technology
Copyright Owner: Copyright 2002 Mineralogical Society of America
Deposited On: 02 Oct 2007 00:00
Last Modified: 15 Jan 2009 07:48

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