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Sintering of Montomorillonites Pillared by Hydroxy-Aluminum Species

Published online by Cambridge University Press:  02 April 2024

D. Tichit ,
F. Fajula ,
F. Figueras ,
B. Ducourant ,
G. Mascherpa ,
C. Gueguen  and
J. Bousquet
D. Tichit
Affiliation:
Laboratoire de Chimie Organique Physique et Cinétique Chimique Appliquées, UA 418 CNRS, ENSCM 8, rue Ecole Normale, 34075 Montpellier Cedex, France
F. Fajula
Affiliation:
Laboratoire de Chimie Organique Physique et Cinétique Chimique Appliquées, UA 418 CNRS, ENSCM 8, rue Ecole Normale, 34075 Montpellier Cedex, France
F. Figueras
Affiliation:
Laboratoire de Chimie Organique Physique et Cinétique Chimique Appliquées, UA 418 CNRS, ENSCM 8, rue Ecole Normale, 34075 Montpellier Cedex, France
B. Ducourant
Affiliation:
Laboratoire des Acides Minéraux, USTL-UA 79, Place Eugène Bataillon, 34060 Montpellier Cedex, France
G. Mascherpa
Affiliation:
Laboratoire des Acides Minéraux, USTL-UA 79, Place Eugène Bataillon, 34060 Montpellier Cedex, France
C. Gueguen
Affiliation:
Centre de Recherches ELF-Solaize, Saint Symphorien d'Ozon, France
J. Bousquet
Affiliation:
Centre de Recherches ELF-Solaize, Saint Symphorien d'Ozon, France
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Abstract

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The sintering of montmorillonites pillared by hydroxy-Al species was investigated by several techniques. The change of the microporosity of the pillared interlayer clay with temperature shows that sintering was mainly due to the loss of microporosity. On calcination of the parent clay at 760°C, the X-ray powder diffraction pattern did not change; the 060 line shifted only slightly from 8.988 to 9.017 Å. The infrared (IR) spectrum suggested some dehydroxylation, but the structure appears to have been preserved. On calcination of the pillared clay at >700°C, the intensity of the 001 line decreased steadily, the 060 line broadened, and the b parameter decreased slightly from 8.988 to 8.928 Å. Fe3+ ions apparently occupied only one site after calcination at 300°C and two sites after calcination at 700°C. Smaller isomer shifts and higher quadrupole splittings in the Mössbauer spectra suggest that calcination produced more covalent bonding of Fe3+ and a highly distorted structure. The IR spectrum was significantly modified by calcination of the sample, and the 935- and 1125-cm−1 bands disappeared and the 1035-cm−1 band broadened. These results suggest that at <700°C the pillars sintered and that the clay progressively decomposed at >750°C. The pillaring-induced decrease of thermal stability of the clay was likely due to the introduction of protons during the first step of the preparation. The thermal stability of these Al-pillared interlayer complexes is comparable to that reported for hydroxy-silicoaluminum montmorillonites and fluorhectorites.

Résumé

Résumé

Le frittage de montmorillonites pontées par des polycations aluminiques a été étudié par différentes techniques. Les variations de la porosité de l'argile pontée en fonction de la température de calcination sous air sec montrent que le frittage est principalement dû à la disparition de la microporosité. Le spectre de rayons X de l'argile initiale est préservé après calcination à 760°C, la seule modification notable étant un léger déplacement de la raie 060 de 8,988 à 9,017 Å; le spectre infrarouge révèle un début de deshydroxylation, mais la structure reste intacte. La calcination de l'argile pontée provoque une diminution régulière de l'intensité de la raie 001 et un élargissement de la raie 060 au dessus de 700°C, avec une légère contraction du paramètre b de 8,988 à 8,928 Å. Les ions Fe3+ occupent un seul type de site après calcination à 300°C et deux sites différents après calcination à 700°C. Après calcination, le déplacement chimique relatif à ces ions diminue et l’écartement quadrupolaire augmente, ce qui suggère des liaisons plus covalentes avec le réseau et une structure très désordonnée. Le spectre IR est également fortement modifié par la calcination avec la disparition des bandes de vibration à 935 et 1125 cm−1 et l’élargissement de la bande à 1035 cm−1. Ces résultats sont interprétés par un frittage des piliers aluminiques pour T <700°C et une destruction progressive du feuillet de l'argile au dessus de 750°C. La baisse de stabilité thermique de l'argile induite par le pontage est attribuée à l'introduction de protons au cours de la première étape de la préparation. La stabilité thermique de ces argiles pontées par des polycations aluminium est comparable à celle des montmorillonites et des fluorhectorites pontées par des silico-aluminates.

Keywords

CalcinationHydroxy-AlInfrared spectroscopyMontmorilloniteMössbauer spectroscopyPillared interlayer complexThermal stability
Type
Research Article
Information
Clays and Clay Minerals , Volume 36 , Issue 4 , August 1988 , pp. 369 - 375
Copyright
Copyright © 1988, The Clay Minerals Society

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