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The fate of smectite in KOH solutions

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Published/Copyright: March 31, 2015
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American Mineralogist
From the journal American Mineralogist Volume 91 Issue 8-9

Abstract

The aim of the present study was to investigate the detailed evolution of the SAz-1 smectite in 1 M KOH at 80 °C at a solid/liquid ratio of 1/80. AFM observations indicated no change in crystal size or shape. XRD measurements at 40% relative humidity revealed changes in expandability of the smectite. The (001) reflection profile of smectite was modeled using a trial-and-error approach. The results indicate that with increasing run time, the number of non-expandable layers with zero or one water layer increases and that the coherent scattering domain size of the smectite decreases. IR spectroscopy of the reacted smectite suggests that there is no change from the initial clay products. The dehydroxylation temperature showed a slight decrease from 619 to 605 °C. STA measurements demonstrated that the cis-vacant character of the octahedral sheet remained nearly unchanged throughout the experiment. Determination of the average layer charge showed a continuous increase from 0.32 to 0.42 eq/(Si/Al)4O10, whereas the layer charge distribution indicated the appearance of high charged smectite layers with a charge of ~ 0.6 eq/(Si/Al)4O10 and the disappearance of the low charged layers. XPS and SEM measurements indicate an increase of Al in the smectite samples. Isotope data support the theory of an internal diffusion mechanism by gradual changes in δ18O values.

From these data it appears that KOH solutions provoke a mineralogical change in the 2:1 layer of the smectite minerals that increases the layer charge by increasing the Al content. This mineralogical change does not involve dissolution/crystallization processes and then must show solid-state transformation of the clays at 80 °C.

Keywords : Smectite; illitization; solid-state transformation; KOH
Received: 2005-11-11
Accepted: 2006-03-27
Published Online: 2015-03-31
Published in Print: 2006-08-01

© 2015 by Walter de Gruyter Berlin/Boston

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https://doi.org/10.2138/am.2006.2151
Keywords for this article
Smectite; illitization; solid-state transformation; KOH

Articles in the same Issue

  1. Low-temperature Zr mobility: An in situ synchrotron-radiation XRF study of the effect of radiation damage in zircon on the element release in H2O + HCl ± SiO2 fluids
  2. Magnetic properties, microstructure, composition, and morphology of greigite nanocrystals in magnetotactic bacteria from electron holography and tomography
  3. Site preference and local geometry of Sc in garnets: Part I. Multifarious mechanisms in the pyrope-grossular join
  4. Site preference and local geometry of Sc in garnets: Part II. The crystal-chemistry of octahedral Sc in the andradite–Ca3Sc2Si3O12 join
  5. The arrojadite enigma: I. A new formula and a new model for the arrojadite structure
  6. The arrojadite enigma: II. Compositional space, new members, and nomenclature of the group
  7. Single-crystal X-ray diffraction and temperature dependent 57Fe Mössbauer spectroscopy on the hedenbergite-aegirine (Ca,Na)(Fe2+,Fe3+)Si2O6 solid solution
  8. Stacking structures in pyrophyllite revealed by high-resolution transmission electron microscopy (HRTEM)
  9. Intensity of quartz cathodoluminescence and trace-element content in quartz from the porphyry copper deposit at Butte, Montana
  10. The fate of smectite in KOH solutions
  11. Light-induced changes in molecular arsenic sulfides: State of the art and new evidence by single-crystal X-ray diffraction
  12. Verifying and quantifying carbon Þ xation in minerals from serpentine-rich mine tailings using the Rietveld method with X-ray powder diffraction data
  13. Generation of pressures to ~60 GPa in Kawai-type apparatus and stability of MnGeO3 perovskite at high pressure and high temperature
  14. A model to predict phase equilibrium of CH4 and CO2 clathrate hydrate in aqueous electrolyte solutions
  15. Raman investigation of H2O molecule and hydroxyl groups in the channels of hemimorphite
  16. Stacking structure in disordered talc: Interpretation of its X-ray diffraction pattern by using pattern simulation and high-resolution transmission electron microscopy
  17. Electrical conductivities of pyrope-almandine garnets up to 19 GPa and 1700 °C
  18. Crystal chemistry and polytypism of tyrolite
  19. Effect of melt structure on trace-element partitioning between clinopyroxene and silicic, alkaline, aluminous melts
  20. Analysis of light lithophile elements (Li, Be, B) by laser ablation ICP-MS: Comparison between magnetic sector and quadrupole ICP-MS
  21. Stornesite-(Y), (Y, Ca)⃞2Na6(Ca,Na)8(Mg,Fe)43(PO4)36, the first terrestrial Mg-dominant member of the fillowite group, from granulite-facies paragneiss in the Larsemann Hills, Prydz Bay, East Antarctica
  22. Electron paramagnetic resonance spectroscopic study of carbonate-bearing fluorapatite: New defect centers and constraints on the incorporation of carbonate ions in apatites
  23. EXAFS signature of structural Zn at trace levels in natural and synthetic trioctahedral 2:1 phyllosilicates
  24. A neutron powder diffraction study of Fe and Ni distributions in synthetic pentlandite and violarite using 60Ni isotope
  25. Letter. Quantification of amphibole content in expanded vermiculite products from Libby, Montana U.S.A. using powder X-ray diffraction
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