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Structured water in hydrotalcites of formula Mg x Zn 6− x Al 2 (OH) 16 (CO 3 )·4H 2 O: a Raman microscopic study
Author(s) -
Johnson Therese E.,
Martens Wayde,
Frost Ray L.,
Ding Z.,
Theo Kloprogge J.
Publication year - 2002
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.886
Subject(s) - hydrotalcite , raman spectroscopy , carbonate , chemistry , hydrogen bond , hydrogen , ion , inorganic chemistry , carbonate ion , crystallography , molecule , catalysis , organic chemistry , physics , optics
Raman microscopy was used to characterize synthesized hydrotalcites of formula Mg x Zn 6− x Al 2 (OH) 16 (CO 3 )·4H 2 O. The Raman spectra are conveniently subdivided into spectral features based on (a) the carbonate anion, (b) the hydroxyl units and (c) metal–oxygen units. A model is proposed based on a tripod of M 3 OH units in the hydrotalcite structure. In a simplified model, Raman spectra of the hydroxyl‐stretching region enable bands to be assigned to the Mg 3 OH, Zn 3 OH and Al 3 OH units. Bands are also assigned to the hydroxyl stretching vibrations of water. Three types of water are identified: (a) water hydrogen bonded to the interlayer carbonate ion, (b) water hydrogen bonded to the hydrotalcite hydroxyl surface and (c) interlamellar water. A model of water in the hydrotalcite structure is proposed in which water is in a highly ordered structure as it is hydrogen bonded to both the carbonate anion and the hydroxyl surface and also forms bridges between the MOH surface and the carbonate anion. Copyright © 2002 John Wiley & Sons, Ltd.