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E. Horváth University of Veszprém Department of Environmental Engineering and Chemical Technology H-8201 Veszprém P.O. Box 158 Hungary H-8201 Veszprém P.O. Box 158 Hungary

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J. Kristóf University of Veszprém Department of Environmental Engineering and Chemical Technology H-8201 Veszprém P.O. Box 158 Hungary H-8201 Veszprém P.O. Box 158 Hungary

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R. Frost Queensland University of Technology Centre for Instrumental and Developmental Chemistry GPO Box 2434 Brisbane Q 4001 Australia GPO Box 2434 Brisbane Q 4001 Australia

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Á. Rédey University of Veszprém Department of Environmental Engineering and Chemical Technology H-8201 Veszprém P.O. Box 158 Hungary H-8201 Veszprém P.O. Box 158 Hungary

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V. Vágvölgyi University of Veszprém Department of Environmental Engineering and Chemical Technology H-8201 Veszprém P.O. Box 158 Hungary H-8201 Veszprém P.O. Box 158 Hungary

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T. Cseh University of Veszprém Department of Environmental Engineering and Chemical Technology H-8201 Veszprém P.O. Box 158 Hungary H-8201 Veszprém P.O. Box 158 Hungary

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Abstract  

The thermal behaviour of halloysite fully expanded with hydrazine-hydrate has been investigated in nitrogen atmosphere under dynamic heating and at a constant, pre-set decomposition rate of 0.15 mg min-1. Under controlled-rate thermal analysis (CRTA) conditions it was possible to resolve the closely overlapping decomposition stages and to distinguish between adsorbed and bonded reagent. Three types of bonded reagent could be identified. The loosely bonded reagent amounting to 0.20 mol hydrazine-hydrate per mol inner surface hydroxyl is connected to the internal and external surfaces of the expanded mineral and is present as a space filler between the sheets of the delaminated mineral. The strongly bonded (intercalated) hydrazine-hydrate is connected to the kaolinite inner surface OH groups by the formation of hydrogen bonds. Based on the thermoanalytical results two different types of bonded reagent could be distinguished in the complex. Type 1 reagent (approx. 0.06 mol hydrazine-hydrate/mol inner surface OH) is liberated between 77 and 103C. Type 2 reagent is lost between 103 and 227C, corresponding to a quantity of 0.36 mol hydrazine/mol inner surface OH. When heating the complex to 77C under CRTA conditions a new reflection appears in the XRD pattern with a d-value of 9.6 , in addition to the 10.2 Ĺ reflection. This new reflection disappears in contact with moist air and the complex re-expands to the original d-value of 10.2 in a few h. The appearance of the 9.6 reflection is interpreted as the expansion of kaolinite with hydrazine alone, while the 10.2 one is due to expansion with hydrazine-hydrate. FTIR (DRIFT) spectroscopic results showed that the treated mineral after intercalation/deintercalation and heat treatment to 300C is slightly more ordered than the original (untreated) clay.

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Journal of Thermal Analysis and Calorimetry
Language English
Size A4
Year of
Foundation
1969
Volumes
per Year
1
Issues
per Year
24
Founder Akadémiai Kiadó
Founder's
Address
H-1117 Budapest, Hungary 1516 Budapest, PO Box 245.
Publisher Akadémiai Kiadó
Springer Nature Switzerland AG
Publisher's
Address
H-1117 Budapest, Hungary 1516 Budapest, PO Box 245.
CH-6330 Cham, Switzerland Gewerbestrasse 11.
Responsible
Publisher
Chief Executive Officer, Akadémiai Kiadó
ISSN 1388-6150 (Print)
ISSN 1588-2926 (Online)

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