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

Abstract

Abstract Hectorite and saponite are exchanged with [Al 13 O 4 (OH) 24 (H 2 O) 12 ] 7+ and the amount of Al 3+ 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 Al 3+ /g adsorbed and release of 0.80 mmol Na + /g. On hectorite the ion exchange is accompanied by supplementary hydrolysis-polymerization of Al 13 . When excess Al is offered in the form of Al 13 , ion exchange is incomplete and is accompanied by precipitation and polymerization of Al 13 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 Al 3+ /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 Al 3+ /g is thermally stable up to 550°C.