The Al Pillaring of Clays. Part II. Pillaring with [Al13O4(OH)24(H2O)12]7+

Robert A. Schoonheydt, Hugo Leeman, Anita Scorpion, Ingrid Lenotte and P. Grobet
Centrum voor Oppervlaktechemie en Katalyse, Materials Research Center K.U. Leuven, K. Mercierlaan 92, 3001 Heverlee, Belgium

Abstract: Hectorite and saponite are exchanged with [Al13O4(OH)24(H2O)12]7+ and the amount of Al3+ adsorbed and Na+ released are followed as a function of the exchange conditions. On saponite the reaction is a pure ion exchange 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 hydrolysis-polymerization of Al13. When excess Al is offered in the form of Al13, ion exchange is incomplete and is accompanied by precipitation and polymerization of Al13 on the surface of both hectorite and saponite. The typical spacing of 1.8 nm is developed after washing, when at least 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 saponite with a loading of at least 1.9 mmol Al3+/g is thermally stable up to 550°C.

Key Wards: Aluminium • Hectorite • Keggin ion • Pillaring • Saponite

Clays and Clay Minerals; October 1994 v. 42; no. 5; p. 518-525; DOI: 10.1346/CCMN.1994.0420502
© 1994, The Clay Minerals Society
Clay Minerals Society (www.clays.org)