Charge Location as a Factor in the Dehydration of 2:1 Clay Minerals

Water was removed from Cu(II)‐saturated smectites by methanol when the isomorphic substitution was in the octahedral layer. However, Cu(II)‐saturated tetrahedrally charged smectites and vermiculites were not completely dehydrated by this treatment. Similarly, when (CH 3 ) 4 N + ‐smectites and vermiculites were degassed, only those clays octahedrally charged were dehydrated. Deuteration of (CH 3 ) 4 N‐montmorillonite and saponite showed the OD stretching frequency for D 2 O bonded to the silica surface was at a higher frequency for montmorillonite than saponite, indicating a stronger deuterium bond to the surface oxygen for the latter clay. These results showed water was bonded with greater energy to tetrahedrally charged clays, possibly resulting from their more localized charge on the silicate surface.