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A Kinetic Study of the Dehydroxylation of Kaolinite

Published online by Cambridge University Press:  01 January 2024

G. W. Brindley
Affiliation:
Department of Ceramic Technology, The Pennsylvania State University, University Park, Pennsylvania, USA
M. Nakahira
Affiliation:
Department of Ceramic Technology, The Pennsylvania State University, University Park, Pennsylvania, USA

Abstract

When dehydroxylation of kaolinite powder is carried out in the usual way, the linear relations anticipated for first-order kinetics and for the Arrhenius plot of log k versus 1/T are satisfied only very approximately. Factors relating to the form of the specimen, (shape, size, compaction, container, etc.) are shown to be very important. A method is developed for obtaining data for a specimen in the form of an infinitely thin disc. The first-order kinetic relation and the Arrhenius relation are then linear, and the latter gives an activation energy of 65 K cal./mol. The dehydroxylation process is shown by x-ray analysis to proceed crystal by crystal and this leads to an interpretation of the first-order kinetics. The x-ray method is used to study the distribution of reacted and unreacted material throughout a disc of material. Although isothermal conditions are employed, large differences are found between the interior and exterior of a partially dehydroxylated disc. These effects are attributed to the influence of a water vapor atmosphere within the heated disc.

Type
Article
Copyright
Copyright © Clay Minerals Society 1956

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Footnotes

Contribution no. 56-35 from the College of Mineral Industries, The Pennsylvania State University, University Park, Pennsylvania.

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