Structural Characterisation of Kaolinite:NaCl Intercalate and its Derivatives

John G. Thompson1, Philippa J. R. Uwins2, Andrew K. Whittaker3 and Ian D. R. Mackinnon2
1 Research School of Chemistry, Australian National University, GPO Box 4, Canberra, ACT 2601, Australia
2 Centre for Microscopy and Microanalysis, University of Queensland, QLD 4072, Australia
3 Centre for Magnetic Resonance, University of Queensland, QLD 4072, Australia

Abstract: Kaolinite:NaCl intercalates with basal layer dimensions of 0.95 and 1.25 nm have been prepared by direct reaction of saturated aqueous NaCl solution with well-crystallized source clay KGa-1. The intercalates and their thermal decomposition products have been studied by XRD, solid-state 23Na, 27Al, and 29Si MAS NMR, and FTIR. Intercalate yield is enhanced by dry grinding of kaolinite with NaCl prior to intercalation. The layered structure survives dehydroxylation of the kaolinite at 500°–600°C and persists to above 800°C with a resultant tetrahedral aluminosilicate framework. Excess NaCl can be readily removed by rinsing with water, producing an XRD ‘amorphous’ material. Upon heating at 900°C this material converts to a well-crystallized framework aluminosilicate closely related to low-camegieite, NaAlSiO4, some 350°C below its stability field. Reaction mechanisms are discussed and structural models proposed for each of these novel materials.

Key Words: FTIR • Intercalate • Kaolinite • NaCl • NMR • Structure • Synthesis • XRD

Clays and Clay Minerals; August 1992 v. 40; no. 4; p. 369-380; DOI: 10.1346/CCMN.1992.0400401
© 1992, The Clay Minerals Society
Clay Minerals Society (www.clays.org)