Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (2) Citing Articles via Google Scholar Google Scholar Articles by Gionis, V. Articles by Chryssikos, G. D. Search for Related Content GeoRef GeoRef Citation

On the structure of palygorskite by mid- and near-infrared spectroscopy

¹ Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, 48 Vass. Constantinou Avenue, Athens 11635, Greece
² Geohellas S.A., 60 Zephyrou Street, Athens, 17564, Greece

Correspondence: ^* E-mail: gdchryss{at}eie.gr

The OH-structural characteristics of an iron-rich palygorskite from Western Macedonia, Greece (Gr-1) and an aluminous palygorskite from Florida (PFl-1) were examined by combined Fourier-transform near-infrared reflectance (NIR) and mid-infrared attenuated total reflectance (ATR) spectroscopy. Analyses of samples heated from ambient to 130 °C allowed for the development of a self-consistent set of band assignments for the structural and surface OH and H₂O species of both the hydrated and dehydrated forms. The inner octahedral sites of both samples are largely accounted for by dioctahedral AlAlOH,AlFe³⁺OH, and Fe³⁺Fe³⁺OH pairs. Band intensities for these pairs are consistent with variations in the concentration of octahedral Fe and Al in the two samples. In addition, both samples display a trace trioctahedral signature in NIR, which may be related to local trioctahedral domains, or the presence of sepiolite in trace amounts, or as intergrowths. A surface H₂O species typical of the hydrated phase was identified via its NIR combination mode at 5317 cm^–1. The desorption of this species by heating revealed distinct silanol groups with overtone and combination modes at 7255 and 4575 cm^–1, respectively. Mg-coordinated and zeolitic H₂O species are strongly coupled in the hydrated phase and give rise to NIR combination modes at 5190 and 5240 cm^–1. The removal of zeolitic H₂O causes the blue shift of the three dioctahedral OH overtones by ca. 20 cm^–1 and the rearrangement of the coordinated H₂O manifested by the growth of sharp combination modes at ca. 5215 and 5120 cm^–1.

Key Words: IR spectroscopy • palygorskite • NIR spectroscopy • Fe-rich • hormite • hydration

This article has been cited by other articles:

				V. Gionis, G. H. Kacandes, I. D. Kastritis, and G. D. Chryssikos COMBINED NEAR-INFRARED AND X-RAY DIFFRACTION INVESTIGATION OF THE OCTAHEDRAL SHEET COMPOSITION OF PALYGORSKITE Clays and Clay Minerals, December 1, 2007; 55(6): 543 - 553. [Abstract] [Full Text] [PDF]

				Z. LI, K. HE, L. YIN, F. XIONG, and Y. C. ZHENG Crystallochemistry of Fe-rich palygorskite from eastern China Clay Minerals, December 1, 2007; 42(4): 453 - 461. [Abstract] [Full Text] [PDF]