CHEMICAL, SORPTIVE AND MORPHOLOGICAL PROPERTIES OF MONTMORILLONITE TREATED WITH AMMONIUM B IFLUORIDE (NH4HF 2) SOLUTIONS

(NH4HF2) has been investigated bychemical, sorptive, porosimetric and electron microscopic methods. Changes inthe chemical composition f the montmorillonite during the fluorination were compared both in the crystal surface and in the bulk sample. The accumulation f fluorine was distinctly zonal, being present mainly in the surface layers. The electron microscope studies showed that he 300--400 nm thick macrodomains i the initial montmorillonite w re cracked into small microdomains 20-30 nm in thickness, this resulting from disruption i the continuity ofthe octahedral sheets. These distinct changes in morphology of the montmoriUonite aggregates particularly influenced the porosity and sorptive properties. During the last fifteen years the insertion of fluorine into the structure of aluminosilicates to modify their physico-chemical properties has been studied extensively. The fluoro-derivatives of silicates and layer aluminosilicates can be obtained either through synthesis of their fluorine structural analogues (Granquist & Kennedy, 1967; Granquist et al., 1972