GALLIUM AND CHROMIUM SUBSTITUTION FOR ALUMINUM IN SYNTHESIZED BEIDELLITE

The hydrothermal synthesis of Mg-beidellite in which limited amounts o f Ga and Cr are clearly shown to be incorporated into nonexchangeable positions in the clay layer framework is reported for the first time. Elemental analyses indicate that, up to at least 15 mole percent, Ga c an replace Al virtually completely; Cr incorporation is more difficult . It appears that the cia that is incorporated into the beidellite is located primarily in the octahedral sheet. Pillaring of the synthesize d beidellite by replacing the Mg2+ with large AlO4Al12(OH)(24)(H2O)(12 )(7+) ions showed that approximately 5.5 meq Al3+ was required per g o f beidellite to achieve complete pillaring. This amount is very simila r to that required for montmorillonite, and suggests that the cation e xchange capacity (CEC) of the beidellite is about 98 meq/g.