STRUCTURAL CHARACTERIZATION OF KAOLINITE-NACL INTERCALATE AND ITS DERIVATIVES

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 Na-23, Al-27, and Si-29 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-degrees-600-degrees-C and persists to above 800-degree-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-degrees-C this material converts to a well-crystallized framework aluminosilicate closely related to low-carnegieite, NaAlSiO4, some 350-degrees-C below its stability field. Reaction mechanisms are discussed and structural models proposed for each of these novel materials