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The 1640 cm-1 infrared band, monitor for the gain and thermal stability of water produced in ground kaolinites

Published online by Cambridge University Press:  09 July 2018

E. Mendelovici
Affiliation:
Laboratory of Physico-Chemistry of Materials, IVIC, Apartado 21827, Caracas 1020A, Venezuela
R. Villalba
Affiliation:
Laboratory of Physico-Chemistry of Materials, IVIC, Apartado 21827, Caracas 1020A, Venezuela
A. Sagarzazu
Affiliation:
Laboratory of Physico-Chemistry of Materials, IVIC, Apartado 21827, Caracas 1020A, Venezuela
O. Carias
Affiliation:
Laboratory of Physico-Chemistry of Materials, IVIC, Apartado 21827, Caracas 1020A, Venezuela

Abstract

The development of the infrared (IR) absorption band at 1640 cm−1 (δH2O) is employed to monitor the gain in molecular water of progressively mortar-ground kaolinite. The planimetred area of this band shows a linear correlation with weight loss at 105°C (free moisture) between 2 and 18 h grinding, indicating a steady increase of molecular water in this range. Heating of ground products to 105°C causes a decrease of about ⅓ in the 1640 cm−1 peak area for all ground samples. This area decrease corresponds to a 34% (average) loss of free moisture as determined by gravimetry. The remaining water is held up to 280°C and is more tightly held in the kaolinite ground for shorter (2–5 h) intervals than in further ground kaolinites. The 1640 cm−1 peak is not detected in any ground kaolinite after heating to 600°C the temperature at which kaolinite dehydroxylates completely. The differentiation of the energetically different OH groups present in ground kaolinite and the mechanism of water gain are compared and discussed from IR spectroscopy and weight loss results.

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1995

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