Synthesis and Characterization of a Hollow Spherical Form of Monolayer Aluminosilicate

Koji Wada1, Michael Wilson2, Yasuko Kakuto1 and Shin-Ichiro Wada1
1 Faculty of Agriculture, Kyushu University 46, Fukuoka 812, Japan
2 Division of Fossil Fuels, CSIRO, Delhi Road, North Ryde New South Wales 2113, Australia

Abstract: Hollow spherical particles of aluminosilicate having diameters of 80 to 100 Å and high electric charge were synthesized by heating solutions containing Si and Al concentrations of about 2 mM (Si/Al molar ratio = 1.0–1.2; pH = 9.0) at 95°–100°C for 7 days. Electron microscopy, X-ray powder diffraction, and infrared spectroscopy suggested that the walls of the spherical particles consisted of monolayer aluminosilicate, most probably having a 1:1 layer structure. Chemical analysis supported this supposition but indicated modifications as shown in the formula (Si1.85Al0.62)IV(A1.38)VI(OH)4.10O 4.96Na0.62, compared with (Si2)IV(Al2)VI(OH)4O5 for an ideal 1:1 layer silicate. High-resolution 29Si and 27Al nuclear magnetic resonance spectroscopy indicated the substitution of Al for Si in the tetrahedral sheet, the presence of AlIV and AlVI, and the presence of Si bonded through oxygen to three Al atoms and one H. A natural counterpart of the synthesized aluminosilicate may be a precursor of halloysites formed by weathering of volcanic ash and pumice and have a close structural relation with allophane and imogolite.

Key Words: Allophane • Aluminosilicate • Halloysite • Imogolite • Infrared spectroscopy • Nuclear magnetic resonance • Synthesis • Transmission electron microscopy

Clays and Clay Minerals; February 1988 v. 36; no. 1; p. 11-18; DOI: 10.1346/CCMN.1988.0360102
© 1988, The Clay Minerals Society
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