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

  • C. R. De Kimpe (a1) and H. Kodama (a2)

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).

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Cloos, P., Leonard, A.J., Moreau, J.P., Herbillon, A. & Fripiat, J.J. (1969) Structural organization in amorphous silico-aluminas. Clays Clay Miner. 17, 279287.
De Kimpe, C.R. (1969) Crystallization of kaolinite at low temperature from an alumino-silicic gel. Clays Clay Miner. 17, 3738.
De Kimpe, C.R. (1976) Formation of phyllosilicates and zeolites from pure silica-alumina gels. Clays Clay Miner. 24, 200207.
De Kimpe, C.R., Gastuche, M.C. & Brindley, G.W. (1964) Low-temperature synthesis of kaolin minerals. Am. Miner. 49, 116.
De Kimpe, C.R., Kodama, H. & Rivard, R. (1981) Hydrothermal formation of a kaolinite-like product from non-crystalline aluminosilicate gels. Clays Clay Miner. 29, 446450.
Klug, H.P. & Alexander, L.E. (1974) X-ray Diffraction Procedure for Polycrystalline and Amorphous Materials. 2nd edition, 791859. John Wiley and Sons, New York.
Leonard, A., Suzuki, S., Fripiat, J.J. & De Kimpe, C.R. (1964) Structure and properties of amorphous silico-aluminas. I—Structure from X-ray fluorescence spectroscopy and IR spectroscopy. J. Phys. Chem. 68, 26082617.
Rodrique, L., Poncelet, G. & Herbillon, A. (1973) Importance of the silica subtraction process during the hydrothermal kaolinization of amorphous silico-aluminas. Proc. Int. Clay Conf. Madrid, 187198.
White, E., McKinstry, H. & Bates, T.F. (1958) Crystal chemical studies by X-ray fluorescence. Proc. 7th Ann. Conf. X-ray Anal. Denver 2, 239245.

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

  • C. R. De Kimpe (a1) and H. Kodama (a2)

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