Clays and Clay Minerals

, Volume 37, Issue 5, pp 469–473 | Cite as

Mechanisms of Palygorskite and Sepiolite Alteration as Deduced from Solid-State 27A1 and 29Si Nuclear Magnetic Resonance Spectroscopy

  • Sridhar Komarneni


The mechanisms of palygorskite and sepiolite alteration to smectite under mild hydrothermal conditions were investigated by solid-state 27Al and 29Si magic-angle spinning-nuclear magnetic resonance (MAS-NMR) spectroscopy, X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). Palygorskite altered to smectite in the presence of NaOH at 150°C. 27Al MAS-NMR spectroscopy showed that the Al coordination changed from chiefly octahedral in palygorskite to chiefly tetrahedral in the smectite product. 29Si MAS-NMR spectroscopy showed that the nearest neighbor environment of Si also changed when palygorskite altered to smectite. The XRD data showed that the synthetic smectite is trioctahedral in nature with tetrahedral charge. The TEM results revealed that the needle-like morphology of palygorskite was preserved in the product smectite. The MAS-NMR results in conjunction with the above XRD and TEM studies suggest that the mechanism of palygorskite alteration was a dissolution and recrystallization process rather than a solid-state reorganization to form 2:1 layer silicate units from the preexisting chain structure. Sepiolite altered to smectite in the presence of 2 N salt solutions at 300°C. The trioctahedral nature of the product smectite as detected by XRD and the foil-like morphology of product smectite as shown by TEM suggest that the mechanism of sepiolite transformation to smectite was also a dissolution and recrystallization process. The tetrahedral Al coordination detected by 27Al MAS-NMR in the smectite altered from sepiolite corroborated the XRD and TEM results.

Key Words

Al coordination Hydrothermal transformation Nuclear magnetic resonance Palygorskite Sepiolite Smectite X-ray powder diffraction 


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Bethke, C. M. and Altaner, S. P. (1986) Layer-by-layer mechanism of smectite illitization and application to a new rate law: Clays & Clay Minerals 34, 136–145.CrossRefGoogle Scholar
  2. Brindley, G. W. and Brown, G., eds. (1980) Crystal Structures of Clay Minerals and their X-ray Identification: Mineralogical Society, London, 495 pp.Google Scholar
  3. DeJong, B. H. W. S., Schramm, C. M., and Parziale, V. E. (1983) Polymerization of silicate and aluminate tetrahedra in glasses, melts, and aqueous solutions–IV. Aluminum coordination in glasses and aqueous solutions and comments on the aluminum avoidance principle: Geochim. Cosmochim. Acta 47, 1223–1236.CrossRefGoogle Scholar
  4. Eberl, D., Whitney, G., and Khoury, H. (1978) Hydrothermal reactivity of smectite: Amer. Mineral. 63, 401–409.Google Scholar
  5. Fyfe, C. A., Gobbi, G. C., Hartman, J., Lenkinski, R., O’Brien, J., Beange, E. R., and Smith, M. A. R. (1982) High resolution solid state MAS spectra of Si-29, A1-27, B-11 and other nuclei in inorganic systems using a narrow-bore 400 MHz high resolution NMR spectrometer: J. Mag. Reson. 47, 168–173.Google Scholar
  6. Golden, D. C., Dixon, J. B., Shadfan, H., and Kippenberger, L. A. (1985) Palygorskite and sepiolite alteration to smectite under alkaline conditions: Clays & Clay Minerals 33, 44–50.CrossRefGoogle Scholar
  7. Greene-Kelley, R. (1955) Dehydration of montmorillonite minerals: Mineral. Mag. 30, 604–615.Google Scholar
  8. Giiven, N. and Carney, L. L. (1979) The hydrothermal transformation of sepiolite to stevensite and the effect of added chlorides and hydroxides: Clays & Clay Minerals 27, 253–260.CrossRefGoogle Scholar
  9. Hofmann, V. U. and Kiemen, R. (1950) Verlust der Austauschfahigkeit von Lithiumionen an Bentonit durch Erhitzung: Z. Anorgan. Chemie 262, 95–99.CrossRefGoogle Scholar
  10. Howard, J. J. (1981) Lithium and potassium saturation of illite/smectite clays from interlaminated shales and sandstones: Clays & Clay Minerals 29, 136–142.CrossRefGoogle Scholar
  11. Komaraeni, S. and Breval, E. (1985) Characterization of smectites synthesized from zeolites and mechanism of smectite synthesis: Clay Miner. 20, 181–188.CrossRefGoogle Scholar
  12. Komarneni, S., Freeborn, W. P., and Smith, C. A. (1979) Simple cold-weld sealing of noble metal tubes: Amer. Mineral. 64, 650–651.Google Scholar
  13. Komarneni, S., Fyfe, C. A., and Kennedy, G. J. (1986) Detection of nonequivalent Si sites in sepiolite and palygorskite by solid-state 29Si magic-angle spinning-nuclear magnetic resonance: Clays & Clay Minerals 34, 99–102.CrossRefGoogle Scholar
  14. Lippmaa, E., Magi, M., Samoson, A., Engelhardt, G., and Grimmer, A. R. (1980) Structural studies of silicates by solid-state high-resolution Si-29 NMR: J. Amer. Chem. Soc. 102, 4889–4893.CrossRefGoogle Scholar
  15. Magi, M., Lippmaa, E., Samoson, A., Engelhardt, G., and Grimmer, A. R. (1984) Solid-state high-resolution silicon-29 chemical shifts in silicates: J. Phys. Chem. 88, 1518–1522.CrossRefGoogle Scholar
  16. Muller, D., Gessner, W., Behrends, H. J., and Scheler, G. (1981) Determination of the aluminum coordination in aluminum-oxygen compounds by solid-state high-resolution 27Al NMR: Chemical Physics Letters 79, 59–62.CrossRefGoogle Scholar
  17. Mumpton, F. A. and Roy, R. (1956) New data on sepiolite and attapulgite in Clays & Clay Minerals, Proc. 5th Natl. Conf., Urbana, Illinois, 1955, Ada Swineford, ed., Natl. Acad. Sci. Natl. Res. Counc. Publ. 566, 136–143.CrossRefGoogle Scholar
  18. Roberson, H. E. and Lahann, R. W. (1981) Smectite to illite conversion rates, effect of solution chemistry: Clays & Clay Minerals 29, 129–135.CrossRefGoogle Scholar
  19. Schultz, L. G. (1969) Lithium and potassium absorption, dehydroxylation temperature and structural water content of aluminous smectites: Clays & Clay Minerals 17, 115–149.CrossRefGoogle Scholar
  20. Whitney, G. and Northrup, H. R. (1987) Experimental investigation of the smectite to illite reaction: Dual reaction mechanisms and oxygen-isotope systematics: Amer. Mineral. 73, 77–90.Google Scholar

Copyright information

© The Clay Minerals Society 1989

Authors and Affiliations

  • Sridhar Komarneni
    • 1
  1. 1.Materials Research Laboratory and Department of AgronomyThe Pennsylvania State UniversityUniversity ParkUSA

Personalised recommendations