NMR evidence for formation of octahedral and tetrahedral Al and repolymerization of the Si network during dissolution of aluminosilicate glass and crystal
-
Natia Tsomaia
,
Susan L. Brantley
Abstract
Five sodium aluminosilicate glasses in the series Na2O: xAl2O3,:(3-x) SiO2 and Na20:Al2O3:ySiO2 were prepared and subjected to leaching at pH 2 under ambient conditions for up to 1000 h. Solid- state nuclear magnetic resonance (NMR) spectroscopy revealed the identity of aluminate and silicate environments in the leached surface layers of these glasses as well as a sample of albite crystal subjected to the same aqueous leaching. While 29Si and 27Al magic-angle spinning (MAS) NMR experiments report on the bulk structures of the samples, cross-polarization from hydrogen atoms that are present only in the surface layers provides structural information from the regions of the sample transformed during treatment. Aluminum in octahedral coordination by O atoms (AlVI) is confirmed for the first time on the near-surface region of an albite crystal under the treatment conditions of this study. A quantification of the change in the amount of six-coordinate aluminum as a function of bulk Al/Si ratio is made possible by comparing the relative amounts of 1H → 27Al CPMAS signals from AF and AlVI obtained from different samples under reproducible experimental conditions. The relative contribution of AlVI to total Al in the hydrated layers increases with the Al/Si ratio of the glasses studied. The leached albite crystal sample has an anomalously high concentration of AlVI given its Al/Si ratio. This anomaly is probably related to the relatively low thickness of the leached layer developed on this phase: little hydrogen penetrates the crystal surface and almost all of the Al in the thin leached layer is octahedrally coordinated, similar to Al in solution. These data suggest that hydrolysis of bridging O atoms around Al atoms in the glass or crystal hydrated layer is accompanied by a change in the coordination number of the Al atom. Aging of surfaces documents no formation of AlVI during storage after leaching. The MAS data, coupled with 27Al → 29Si CPMAS experiments, describe the bulk network structure and provide further insight into the surface structures, including documentation of repolymerization of the silicon network in the surface layer of a nepheline glass via formation of condensed Q4 units. Further triple-resonance experiments correlate 1H, 29Si, and 27Al environments in the glasses, and indicate that the repolymerized structures in nepheline glass are not phase-separated from aluminum-containing network structures. These data for acid dissolution under ambient conditions yield the first picture of the complicated series of reactions relating connectivity and coordination number of Al and Si at the altered surfaces of geologically interesting aluminosilicates.
© 2015 by Walter de Gruyter Berlin/Boston
Articles in the same Issue
- A molecular dynamics study of the behavior of sodium in low albite
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- The formation of Sr silicates at low temperature and the solubility product of tobermorite-like Sr5Si6O16(OH)2 .5H2O
- Thermal equation of state of omphacite
- The effect of thermal decarbonation on stable isotope compositions of carbonates
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- The fusion curve of albite revisited and the compressibility of NaAlSi3O8 liquid with pressure
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- Hydration, expansion, structure, and dynamics of layered double hydroxides
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Articles in the same Issue
- A molecular dynamics study of the behavior of sodium in low albite
- Observation and interpretation of paramagnetic defects in Brazilian and Central African carbonados
- Dissolution of gibbsite: Direct observations using fluid cell atomic force microscopy
- Polytypes and higher-order structures of antigorite: A TEM study
- An infrared spectroscopic study of the basic copper phosphate minerals: Cornetite, libethenite, and pseudomalachite
- Influence of F content on the composition of Al-rich synthetic phlogopite: Part I. New information on structure and phase-formation from 29Si, 1H, and 19F MAS NMR spectroscopies
- NMR evidence for formation of octahedral and tetrahedral Al and repolymerization of the Si network during dissolution of aluminosilicate glass and crystal
- Thermodynamic properties of hercynite (FeAl2O4) based on adiabatic calorimetry at low temperatures
- The formation of Sr silicates at low temperature and the solubility product of tobermorite-like Sr5Si6O16(OH)2 .5H2O
- Thermal equation of state of omphacite
- The effect of thermal decarbonation on stable isotope compositions of carbonates
- Synthetic MgAl2O4 (spinel) at high-pressure conditions (0.0001–30 GPa): A synchrotron X-ray powder diffraction study
- The stability of antigorite in the systems MgO-SiO2-H2O (MSH) and MgO-Al2O3-SiO2-H2O (MASH): The effects of Al3+ substitution on high-pressure stability
- The fusion curve of albite revisited and the compressibility of NaAlSi3O8 liquid with pressure
- Correction of secondary X-ray fluorescence near grain boundaries in electron microprobe analysis: Application to thermobarometry of spinel lherzolites
- An overgrowth model to explain multiple, dispersed high-Mn regions in the cores of garnet porphyroblasts
- Synchrotron X-ray diffraction study of the structure and dehydration behavior of todorokite
- Retrograde mineral reactions in saline fluid inclusions: The transformation ferropyrosmalite ↔ clinopyroxene
- The effect of ionizing radiation on uranophane
- Hydration, expansion, structure, and dynamics of layered double hydroxides
- Relict edenite in a garnet lherzolite from the Chinese Su-Lu UHP metamorphic terrane: Implications for metamorphic history
- Norrishite, K(Mn23+Li)Si4O10(O)2, an oxymica associated with sugilite from the Wessels Mine, South Africa: Crystal chemistry and 40Ar-39Ar dating
- The amblygonite (LiAlPO4F)-montebrasite (LiAlPO4OH) solid solution: A combined powder and single-crystal neutron diffraction and solid-state 6Li MAS, CP MAS, and REDOR NMR study
- An X-ray Rietveld, infrared, and Mössbauer spectral study of the NaMn(Fe1–xInx)2(PO4)3 alluaudite-type solid solution
- Gatelite-(Ce), a new REE-bearing mineral from Trimouns, French Pyrenees: Crystal structure and polysomatic relationships with epidote and törnebohmite-(Ce)
- Hydroxyl in clinopyroxene from the deep subducted crust: Evidence for H2O transport into the mantle
- A model for the structure of the hydrated aluminum phosphate, kingite determined by ab initio powder diffraction methods
- The crystal structure of synthetic autunite, Ca[(UO2)(PO4)]2(H2O)11
