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Effect of Ambient Atmosphere on Solid State Reaction of Kaolin-Salt Mixtures

Published online by Cambridge University Press:  02 April 2024

M. Gábor ,
L. Pöppl  and
E. Körös
M. Gábor
Affiliation:
Institute of Inorganic & Analytical Chemistry, L. Eötvös University, P.O. Box 123, H-1443 Budapest, Hungary
L. Pöppl
Affiliation:
Institute of Inorganic & Analytical Chemistry, L. Eötvös University, P.O. Box 123, H-1443 Budapest, Hungary
E. Körös
Affiliation:
Institute of Inorganic & Analytical Chemistry, L. Eötvös University, P.O. Box 123, H-1443 Budapest, Hungary
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Abstract

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The reaction of kaolin with NaCl was followed by dynamic thermal analysis and mass spectrometry under N2, CO2, and air atmospheres and in a 10−5-torr vacuum. The weight loss was a function of the atmosphere used and, according to mass spectrometry, was due to the evolution of H2O, HCl, and very small amounts of H2. HCl was formed only after the release of 85% of the hydroxyl content of the kaolin. When the clay was pretreated with saturated salt solution, H2O and HCl evolved in more or less the same temperature range, indicating that only some of the OH groups reacted with the chloride ion. High-temperature X-ray powder diffraction patterns showed that the sodium ion reacted with the noncrystalline metakaolin to give NaAlSiO4. Chemical analysis showed that the reaction of kaolinite and sodium chloride started below 400°C. The rate of the reaction increased at higher water vapor concentration. From mass spectrometric data, the NaCl-treated kaolin appeared to adsorb CO2. Desorption at several distinct temperatures suggests that CO2 was adsorbed by different parts of the structure, i.e., holes and channels. X-ray powder diffraction and infrared absorption data indicate that the kaolinite structure persisted even after it had been heated with NaCl in a CO2 atmosphere to as high as 800°C.

Keywords

Infrared spectroscopyGaseous atmosphereKaolinMetakaolinSaltThermal analysis
Type
Research Article
Information
Clays and Clay Minerals , Volume 34 , Issue 5 , October 1986 , pp. 529 - 533
Copyright
Copyright © 1986, The Clay Minerals Society

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