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The Coordination of Aluminum Ions in the Palygorskite Structure
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- Journal:
- Clays and Clay Minerals / Volume 40 / Issue 4 / August 1992
- Published online by Cambridge University Press:
- 28 February 2024, pp. 457-461
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- Article
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NMR spectra of PF1-1 Floridan palygorskite strongly suggest that Al3+ occurs only in octahedral coordination. X-ray microanalysis of the palygorskite fibers indicate a chemical composition defined by the atomic ratios: Mg/Si = 0.34, Al/Si = 0.27, and Fe/Si = 0.04. Considering the NMR and CEC data in this report along with the previously published results of IR and Mössbauer spectroscopic studies, the following structural formula is proposed for PF1-1 palygorskite:
$${\rm{(M{g_{2.12}}A{l_{1.68}}F{e^{3 + }}_{0.24}{\square _{0.96}})S{i_8}{O_{20}}{(OH)_2}{(O{H_2})_4}}}$$where □ represents the vacant Ml octahedral sites in the structure, and Al3+ and Fe3+ are all exclusively assigned to the octahedral sites.
