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Titolo:
HYDROTHERMAL SYNTHESIS (250-DEGREES-C) OF COPPER-SUBSTITUTED KAOLINITES
Autore:
PETIT S; DECARREAU A; MOSSER C; EHRET G; GRAUBY O;
Indirizzi:
UNIV POITIERS,CNRS,URA 721,40 AVE RECTEUR PINEAU F-86022 POITIERS FRANCE CTR GEOCHIM SURFACE,CNRS,URA 721 F-67084 STRASBOURG FRANCE CNRS,IPCMS F-67037 STRASBOURG FRANCE CTR RECH MECANISMES CROISSANCE CRISTALLINE,CNRS,UPR 7251 F-13288 MARSEILLE FRANCE
Titolo Testata:
Clays and clay minerals
fascicolo: 4, volume: 43, anno: 1995,
pagine: 482 - 494
SICI:
0009-8604(1995)43:4<482:HS(OCK>2.0.ZU;2-T
Fonte:
ISI
Lingua:
ENG
Soggetto:
ELECTRON-SPIN RESONANCE; NATURAL KAOLINITES; MONTMORILLONITE; PHYLLOSILICATES; CHEMISTRY; SMECTITES; IONS; IRON; ESR;
Keywords:
CU2+; KAOLINITE; OCTAHEDRAL SUBSTITUTION; SYNTHESIS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
67
Recensione:
Indirizzi per estratti:
Citazione:
S. Petit et al., "HYDROTHERMAL SYNTHESIS (250-DEGREES-C) OF COPPER-SUBSTITUTED KAOLINITES", Clays and clay minerals, 43(4), 1995, pp. 482-494

Abstract

To obtain Cu-kaolinites with a controlled range of chemical compositions, syntheses were performed by hydrothermally ageing gels with kaolinite stoichiometric compositions. Gels were prepared with sodium metasilicate and nitrates of octahedral cations. Temperature of synthesis was 250 degrees C with a corresponding equilibrium water pressure of 38bars. Three samples with copper contents ranging from 0.1 to 7% and another one with the chemical composition of the Cu end-member were synthesized. While this fourth sample led to tenorite after the hydrothermal treatment, the three others crystallized well into kaolinite. Up to almost 1% CuO was measured by TEM in some isolated 'clean' and hexagonal kaolinite particles. EPR and XPS spectroscopies were consistent with an octahedral position of Cu2+. In IR spectra, vAl-OH-Cu absorption bands were not observed, but vAl(2)OH bands appeared more and more blurred when Cu content of samples increased. Weak bands situated at 868 cm(-1) and 840 cm(-1) are tentatively attributed to delta AlCuOH. Bydifferential thermal analysis, a downward shift of 20 degrees C in temperature of the endothermic peak from the less Cu-rich sample to the most Cu-rich one, argued for the existence of some Al-OH-Cu bonds, whose binding energies are presumed to be less than the Al-OH-Al ones. Inview of these results, Cu2+ appears incorporated in the octahedral sheet of kaolinite. Moreover, this incorporation is made without major perturbation of the kaolinite structure.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 28/11/20 alle ore 09:14:41