IMIS | Flanders Marine Institute

Flanders Marine Institute

Platform for marine research


Publications | Institutes | Persons | Datasets | Projects | Maps
[ report an error in this record ]basket (0): add | show Print this page

Wetting-induced layer contraction in illite and mica-family relatives
Kühnel, R.A.; Van der Gaast, S.J.; Broekmans, M.A.T.M.; Theng, B.K.G. (2017). Wetting-induced layer contraction in illite and mica-family relatives. Applied Clay Science 135: 226–233.
In: Applied Clay Science. Elsevier: Amsterdam. ISSN 0169-1317; e-ISSN 1872-9053, more
Peer reviewed article  

Available in  Authors 

Author keywords
    Contraction/expansion; Humidity-controlled XRD; Hydronium; Illite; Mica; Protonation/deprotonation

Authors  Top 
  • Kühnel, R.A.
  • Van der Gaast, S.J.
  • Broekmans, M.A.T.M.
  • Theng, B.K.G.

    When dry illite is wetted, its layer structure contracts along the c-axis by up to 0.2 Å. This behavior contrasts with that of smectite which shows interlayer swelling on wetting. Layer contraction has also been found to occur in glauconite and celadonite that are structurally more disordered than illite, as well as with phengite and artificially degraded hydromuscovite. In contrast, muscovite proper does not show contraction. The contraction is ascribed to the deprotonation of hydronium ions (H3O+ → H2O + H+) occupying interlayer K+ positions. The hydronium ion is approximately 5% larger than the neutral water molecule. This difference in size is proportional to the magnitude of contraction. The change in molecular volume and interlayer separation of illite particles may explain the anomalous decrease in density after dehydration under pressure. This paper reports on wetting-induced contraction in illite and related layer silicates, using humidity-controlled X-ray diffraction.

All data in the Integrated Marine Information System (IMIS) is subject to the VLIZ privacy policy Top | Authors