Mechanism and kinetics of reduction of a FeO-Fe2O3-CaO-MgO aluminosilicate melt in a high-CO-activity environment
-
Reid F. Cooper
,
Rebecca L.A. Everman
Abstract
Droplets of an iron-bearing calcia magnesia aluminosilicate (Fe-CMAS) melt were reacted under distinctly reducing conditions (fO₂ = 2.4 × 10-13 and 6.4 × 10-15 atm) at high temperature (~1400 °C) and ambient pressure. The low fO₂ environment was maintained by a flowing gas mixture of CO and CO2, with a high content of CO. Molten metallic iron alloyed with silicon and carbon formed on the surface of the melt; no metal was observed in sample interiors. A color change from brown to pale blue confined to the outer layer of the melt indicated that essentially complete reduction of Fe3+ to Fe2+ had occurred in this region. Analysis of the reaction kinetics, particularly in comparison to melts of similar polymerization but free of CaO, reveals that the concentration of electron holes has decreased to such an extent that ionic transport in the melt is significantly slowed and the diffusion of CO as a neutral species becomes dominant and rate-limiting: molecular CO, initially incorporated into the melt as a physically dissolved species, subsequently reacts to form chemically dissolved (bonded into the melt structure) CO32- anions, consuming electron holes in the process. The chemical diffusion coefficient for CO in the reduced melt at 1400 °C is estimated as DCO ≈ 4 × 10-4 cm2/s, consistent with that of other, similarly sized molecular species (e.g., H2 and H2O) for similarly polymerized melts, as reported by other investigators. Upon quenching, the droplet acts as a closed system. Internal redox couples see the reduction of the carbonate so as to form bubbles of CO, the composition of which are confirmed with Raman spectroscopy. The open-system reduction and closed-system quenching dynamics are analyzed following an Ellingham-diagram approach.
© 2015 by Walter de Gruyter Berlin/Boston
Articles in the same Issue
- TEM-assisted dynamic scanning force microscope imaging of (001) antigorite: Surfaces and steps on a modulated silicate
- PH₂O-dependent structural phase transitions in the zeolite mesolite: Real- and reciprocal-space crystal structure refinements
- The crystal structure of esperite, with a revised chemical formula, PbCa2(ZnSiO4)3, isostructural with beryllonite
- Dendritic zircon formation by deterministic volume-filling fractal growth: Implications for the mechanisms of branch formation in dendrites
- Enthalpies of formation of pyrrhotite Fe1–0.125xS (0 ≤ x ≤ 1) solid solutions
- Crystal chemistry of synthetic lawsonite solid-solution series CaAl2[(OH)2/Si2O7]·H2O– SrAl2[(OH)2/Si2O7]·H2O and the Cmcm–P21/m phase transition
- Coulsellite, CaNa3AlMg3F14, a rhombohedral pyrochlore with 1:3 ordering in both A and B sites, from the Cleveland Mine, Tasmania, Australia
- Synthesis and characterization of zeolite 4A-type desiccant from kaolin
- Effect of iron on the compressibility of hydrous ringwoodite
- Kapundaite, (Na,Ca)2Fe4 3+(PO4)4(OH)3·5H2O, a new phosphate species from Toms quarry, South Australia: Description and structural relationship to mélonjosephite
- Rate of antigorite dehydration at 2 GPa applied to subduction zones
- IR absorption coefficients for water in nominally anhydrous high-pressure minerals
- Experimental techniques for determining tin solubility in silicate melts using silica capsules in 1 atm furnaces and rhenium capsules in the piston cylinder
- Cassiterite-saturated minimum melting behavior within Sn-SnO2-SiO2 at 1 atm and 10 kbar
- Cr-bearing tourmaline associated with emerald deposits from Swat, NW Pakistan: Genesis and its exploration significance
- Mechanism and kinetics of reduction of a FeO-Fe2O3-CaO-MgO aluminosilicate melt in a high-CO-activity environment
- Biodurability of chrysotile and tremolite asbestos in simulated lung and gastric fluids
- High-pressure behavior of Ca/Na clinopyroxenes: The effect of divalent and trivalent 3d-transition elements
- Uvarovite from chromite-bearing ultramafic intrusives, Orissa, India, a crystal-chemical characterization using 57Fe Mössbauer spectroscopy
- An X-ray Rietveld and infrared spectral study of the Na2(Mn1–xM2+x )Fe2+Fe3+(PO4)3 (x = 0 to 1 and M2+ = Mg, Cd) alluaudite-type solid solutions
- Dissolution kinetics of anorthite in a supercritical CO2–water system
- Evaluation of the elasticity normal to the basal plane of non-expandable 2:1 phyllosilicate minerals by nanoindentation
- 57Fe Mössbauer spectroscopy and electrical resistivity studies on naturally occurring native iron under high pressures up to 9.1 GPa
- Letter. Discreditation of paraspurrite
- Letter. High-pressure magnetic transition in hcp-Fe
- Letter. Reduced As components in highly oxidized environments: Evidence from full spectral XANES imaging using the Maia massively parallel detector
- Letter. FTIR spectroscopy with a focal plane array detector: A novel tool to monitor the spatial OH-defect distribution in single crystals applied to synthetic enstatite
- Letter. Akaogiite: An ultra-dense polymorph of TiO2 with the baddeleyite-type structure, in shocked garnet gneiss from the Ries Crater, Germany
Articles in the same Issue
- TEM-assisted dynamic scanning force microscope imaging of (001) antigorite: Surfaces and steps on a modulated silicate
- PH₂O-dependent structural phase transitions in the zeolite mesolite: Real- and reciprocal-space crystal structure refinements
- The crystal structure of esperite, with a revised chemical formula, PbCa2(ZnSiO4)3, isostructural with beryllonite
- Dendritic zircon formation by deterministic volume-filling fractal growth: Implications for the mechanisms of branch formation in dendrites
- Enthalpies of formation of pyrrhotite Fe1–0.125xS (0 ≤ x ≤ 1) solid solutions
- Crystal chemistry of synthetic lawsonite solid-solution series CaAl2[(OH)2/Si2O7]·H2O– SrAl2[(OH)2/Si2O7]·H2O and the Cmcm–P21/m phase transition
- Coulsellite, CaNa3AlMg3F14, a rhombohedral pyrochlore with 1:3 ordering in both A and B sites, from the Cleveland Mine, Tasmania, Australia
- Synthesis and characterization of zeolite 4A-type desiccant from kaolin
- Effect of iron on the compressibility of hydrous ringwoodite
- Kapundaite, (Na,Ca)2Fe4 3+(PO4)4(OH)3·5H2O, a new phosphate species from Toms quarry, South Australia: Description and structural relationship to mélonjosephite
- Rate of antigorite dehydration at 2 GPa applied to subduction zones
- IR absorption coefficients for water in nominally anhydrous high-pressure minerals
- Experimental techniques for determining tin solubility in silicate melts using silica capsules in 1 atm furnaces and rhenium capsules in the piston cylinder
- Cassiterite-saturated minimum melting behavior within Sn-SnO2-SiO2 at 1 atm and 10 kbar
- Cr-bearing tourmaline associated with emerald deposits from Swat, NW Pakistan: Genesis and its exploration significance
- Mechanism and kinetics of reduction of a FeO-Fe2O3-CaO-MgO aluminosilicate melt in a high-CO-activity environment
- Biodurability of chrysotile and tremolite asbestos in simulated lung and gastric fluids
- High-pressure behavior of Ca/Na clinopyroxenes: The effect of divalent and trivalent 3d-transition elements
- Uvarovite from chromite-bearing ultramafic intrusives, Orissa, India, a crystal-chemical characterization using 57Fe Mössbauer spectroscopy
- An X-ray Rietveld and infrared spectral study of the Na2(Mn1–xM2+x )Fe2+Fe3+(PO4)3 (x = 0 to 1 and M2+ = Mg, Cd) alluaudite-type solid solutions
- Dissolution kinetics of anorthite in a supercritical CO2–water system
- Evaluation of the elasticity normal to the basal plane of non-expandable 2:1 phyllosilicate minerals by nanoindentation
- 57Fe Mössbauer spectroscopy and electrical resistivity studies on naturally occurring native iron under high pressures up to 9.1 GPa
- Letter. Discreditation of paraspurrite
- Letter. High-pressure magnetic transition in hcp-Fe
- Letter. Reduced As components in highly oxidized environments: Evidence from full spectral XANES imaging using the Maia massively parallel detector
- Letter. FTIR spectroscopy with a focal plane array detector: A novel tool to monitor the spatial OH-defect distribution in single crystals applied to synthetic enstatite
- Letter. Akaogiite: An ultra-dense polymorph of TiO2 with the baddeleyite-type structure, in shocked garnet gneiss from the Ries Crater, Germany
