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Transformation of an aluminosilicate gel into pre-kaolinitic and pre-zeolite structures: effects of the solution media

Published online by Cambridge University Press:  09 July 2018

C. R. De Kimpe  and
H. Kodama
C. R. De Kimpe
Affiliation:
Agriculture Canada, Station de Recherches, 2560 Hochelaga Blvd, Sainte-Foy, Québec G1V 2J3
H. Kodama
Affiliation:
Agriculture Canada, Chemistry and Biology Research Institute, Ottawa K1A OC6, Canada
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Extract

Rodrique et al. (1972) reported that kaolinite was formed at 200°C from gels with an A12O3/(A12O3 + SiO2) weight ratio ⩽0·315 and pH values ranging from 4·8 to 5·8. At this temperature and using a gel with an A12O3/(A12O3 + SiO2) weight ratio >0.315, boehmite and pseudoboehmite, were obtained at pH values of up to 5·8. The latter minerals were also observed in the products formed under similar conditions at 175°C.

Unlike the situation under acidic conditions, where gel composition is important, the gel/solution ratio becomes critical under alkaline conditions. When the gel/solution ratio is low, zeolites are produced from a gel with a weight ratio between 0·3 and 0·5 in the presence of NaOH at 130-170°C (De Kimpe, 1976). When the gel/solution ratio is high, kaolinite instead of zeolites is formed under similar conditions (De Kimpe, 1969, 1976). For an intermediate gel/solution ratio, smectite is produced from a gel with a weight ratio of 0.4 in the presence of NaOH at 175°C In the presence of KOH, however, kaolinite is the only crystalline product formed under similar pH and temperature conditions (De Kimpe et al., 1981).

Type
Notes
Information
Clay Minerals , Volume 19 , Issue 2 , April 1984 , pp. 237 - 242
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1984

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References

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