Hydrothermal reaction of albite and a sodium aluminosilicate glass: A solid-state NMR study

Journal Article · Sat Apr 01 04:00:00 EST 1989 · Geochimica et Cosmochimica Acta; (USA)

OSTI ID:5022854

Yang, Wanghong Alex; Kirkpatrick, R J ^[1]

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1. Univ. of Illinois, Urbana (USA)

The authors present here a solid-state NMR study of the structure and chemical composition of the products and mechanisms of the reaction of crystalline low albite and a glass of nearly albite composition with aqueous solutions of pH from 1 to 11 at 250{degree}C. For the crystalline albite, there are no detectable bulk or surface structural changes due to aqueous attack, consistent with the idea that both cation exchange and disruption of the aluminosilicate framework occur only near the mineral/solution interface and that the hydrated surface layer, if it exists, is not more than about 30 {angstrom} thick. This reaction occurs by solution/reprecipitation, and its rate decreases with increasing solution pH, supporting the idea that the dissolution of feldspar is initiated by cation-exchange. The incorporation of molecular water and cation-exchange cause structural changes in the glass via solid-state adjustment without dissolution/reprecipitation. The large cations in the hydrated glass (Na and K) probably have a shell of water molecules round them, with a maximum average coordination number of six. The secondary phases formed from both albite and the glass are often amorphous and can be well characterized by NMR. The compositional and structural variations of the amorphous phases are important factors in these reactions and cannot be ignored in theoretical models of aluminosilicate dissolution. As expected, the aluminum coordination in the secondary phases changes from six-fold to four-fold as the solution pH increases.

• OSTI ID: 5022854
• Journal Information: Geochimica et Cosmochimica Acta; (USA), Journal Name: Geochimica et Cosmochimica Acta; (USA) Vol. 53:4; ISSN GCACA; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
ABSORPTION SPECTROSCOPY
ALBITE
ALKALI METAL COMPOUNDS
ALUMINIUM COMPOUNDS
ALUMINIUM SILICATES
AMORPHOUS STATE
CHEMICAL COMPOSITION
CHEMICAL REACTIONS
CHEMISTRY
CRYSTAL STRUCTURE
CRYSTALLOGRAPHY
DISSOLUTION
FELDSPARS
GEOCHEMISTRY
HYDROTHERMAL ALTERATION
INFRARED SPECTRA
ION EXCHANGE
MAGNETIC RESONANCE
MINERALOGY
MINERALS
MOLECULAR STRUCTURE
NUCLEAR MAGNETIC RESONANCE
OXYGEN COMPOUNDS
PH VALUE
RESONANCE
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
SODIUM COMPOUNDS
SODIUM SILICATES
SPECTRA
SPECTROSCOPY