THE AL PILLARING OF CLAYS .2. PILLARING WITH [AL13O4(OH)24(H2O)12](7+)

Hectorite and saponite are exchange with [Al13O4(OH)24(H2O)12]7+ and t he amount of Al3+ adsorbed and Na+ released are followed as a function of the exchange conditions. On saponite the reaction is a pure ion ex change with 2-2.15 mmol Al3+/g adsorbed and release of 0.80 mmol Na+/g . On hectorite the ion exchange is accompanied by supplementary hydrol ysis-polymerization of Al13. When excess Al is offered in the form of Al13, ion exchange is incomplete and is accompanied by precipitation a nd polymerization of Al13 on the surface of both hectorite and saponit e. The typical spacing of 1.8 nm is developed after washing, when at l east 1.3-1.4 mmol Al3+/g is adsorbed. Above a loading of 2.2-2.5 mmol/ g the 1.8 nm spacing is obtained without washing. Only pillared saponi te with a loading of at least 1.9 mmol Al3+/g is thermally stable up t o 550-degrees-C.