Mechano-chemical activation of kaolin minerals

Tests have been made to study processes during the intensive grinding (supergrinding) as mechanical activation of kaolins. Activation was made by dry grinding for different times in a vibrating mill. Conclusions: 1. Change of the inner morphology of kaolin powders is due to three partial processes:...

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Bibliographic Details
Main Author: Juhász Zoltán
Corporate Author: International Kaolin Symposium (10.) (1979) (Budapest)
Format: Article
Published: University of Szeged, Department of Mineralogy, Geochemistry and Petrology Szeged 1980
Series:Acta mineralogica-petrographica 24
Kulcsszavak:Kőzettan, Ásványtan, Földtan
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Online Access:http://acta.bibl.u-szeged.hu/24680
Description
Summary:Tests have been made to study processes during the intensive grinding (supergrinding) as mechanical activation of kaolins. Activation was made by dry grinding for different times in a vibrating mill. Conclusions: 1. Change of the inner morphology of kaolin powders is due to three partial processes: disintegration, aggregation and agglomeration. The first one prevails for a short activation time, the latter two being overwhelming in prolonged activation. Therefore the grade of dispersity initially grows to decrease after prolonged grinding. In this latter case, compacted aggregates result, inacessible to soaking in water, even if a peptizer is added. Also plasticity of the kaolin-water system decreases. 2. Supergrinding also affects the mutual adhesion, adsorption properties and action exchange capacity of kaolin particles as well as the acid solubility of kaolins very much. Test data hint to surface activation. At the same time, surface active centres will be covered by neighbouring particles ("overlapping effect"). 3. Supergrinding causes amorphization of the crystal structure, beside appearance of fireclay structure. Amorphization is bound to a critical crystallite size, and has different rates along each crystallographic direction. 4. Destruction of the crystal structure of kaolinite is concomitant to.the release of water of structural OH groups followed by incorporation of water into a gel structure. Xerogel when heated yields stable phases at the sáme high temperature as the original kaolinite. The high-temperature sintering process is, however, somewhat different in the two materials. 5. Mechano-chemical processes are somewhat accessible to artificial influencing by preliminary ion exchange."
Physical Description:121-145
ISSN:0365-8066