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XAFS study of Cu model compounds and Cu2+ sorption products on amorphous SiO2, γ-Al2O3, and anatase

  • Sing-Foong Cheah EMAIL logo , Gordon E. Brown and George A. Parks
Published/Copyright: March 25, 2015
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American Mineralogist
From the journal American Mineralogist Volume 85 Issue 1

Abstract

The primary objective of this study is to determine the effect of substrate type on the coordination environments of Cu2+ adsorbed on amorphous SiO2, γ-Al2O3, and anatase at a surface coverage of approximately 1 mmol/m2. We also collected X-ray absorption fine structure (XAFS) data for several Cu2+-containing model compounds, including tenorite (VICuO), spertiniite [VICu(OH)2], dioptase (VICuSiO2·H2O), shattuckite [VICu5(SiO3)4(OH)2], chrysocolla [VI(Cu,Al)2H2Si2O5 (OH)4·nH2O], and Cu2+ acetate monohydrate [VICu(CH4CO2)2·H2O], for comparison with the sorption sample data. Detailed analysis of these model compounds indicates that the bonding of second neighbors surrounding a central Cu absorber determines whether these second neighbors can be detected by XAFS. The XAFS results of Cu2+ sorption samples are consistent with the presence of Jahn-Teller distorted Cu2+(O,OH)6 octahedra, with four equatorial Cu-O bonds (1.95 Å) and two longer axial bonds; the axial Cu-O bonds are difficult to characterize quantitatively by XAFS spectroscopy. Cu2+ sorbed on amorphous SiO2 was found to have Cu second and third neighbors at 2.95 Å, 3.30 Å, and 5.72 Å, but no Cu-Si correlation was detected for these sorption products associated with amorphous SiO2. Based on XAFS and wet chemical results, it seems likely that a Cu(OH)2 precipitate has formed in the Cu2+/amorphous SiO2 system. Cu2+ sorbed on γ-Al2O3 is present as a mixture of monomeric, dimeric, and perhaps a small number of oligomeric hydroxo-bridged Cu(O,OH)6 species with a Cu-Cu distance of approximately 2.95 Å. Sorbed Cu2+ on anatase is present predominantly as hydroxo-bridged Cu dimers. At similar sorption densities, Cu2+ cluster sizes on amorphous SiO2 are significantly larger than those on g-Al2O3 or anatase, indicating that the substrate has an important effect on the type of Cu2+ sorption complex or precipitates formed.

Received: 1998-3-9
Accepted: 1999-9-1
Published Online: 2015-3-25
Published in Print: 2000-1-1

© 2015 by Walter de Gruyter Berlin/Boston

Articles in the same Issue

  1. Eclogite-facies relics and inferred ultrahigh-pressure metamorphism in the North Dabie Complex, central-eastern China
  2. Application of INVEQ to the geothermobarometry of metamorphic rocks near a kyanite-sillimanite isograd, Mica Creek, British Columbia
  3. Microstructural characterization of metamorphic magnetite crystals with implications for oxygen isotope distribution
  4. Coexisting monazite and allanite in peraluminous granitoids of the TribečMountains, Western Carpathians
  5. Effect of alkalis, phosphorus, and water on the surface tension of haplogranite melt
  6. Direct observation of immiscibility in pyrope-almandine-grossular garnet
  7. On the cluster analysis of grains and crystals in rocks
  8. Experimental approach to constrain second critical end points in fluid/silicate systems: Near-solidus fluids and melts in the system albite-H2O
  9. Estimation and testing of standard molar thermodynamic properties of tourmaline end-members using data of natural samples
  10. An investigation of matrix effects in the analysis of fluorine in humite-group minerals by EMPA, SIMS, and SREF
  11. New data on the crystal-chemistry of fluoborite by means of SREF, SIMS, and EMP analysis
  12. Effect of aluminum on Ti-coordination in silicate glasses: A XANES study
  13. XAFS study of Cu model compounds and Cu2+ sorption products on amorphous SiO2, γ-Al2O3, and anatase
  14. Oxidation-reduction mechanism of iron in dioctahedral smectites: I. Crystal chemistry of oxidized reference nontronites
  15. Oxidation-reduction mechanism of iron in dioctahedral smectites: II. Crystal chemistry of reduced Garfield nontronite
  16. 15N NMR study of nitrate ion structure and dynamics in hydrotalcite-like compounds
  17. 29Si and 27Al MAS-NMR spectroscopy of b-eucryptite (LiAlSiO4): The enthalpy of Si,Al ordering
  18. The nuclear and magnetic structure of “white rust”—Fe(OH0.86D0.14)2
  19. In-situ study of the R3̅ to R3̅c phase transition in the ilmenite-hematite solid solution using time-of-flight neutron powder diffraction
  20. In situ X-ray diffraction investigation of lawsonite and zoisite at high pressures and temperatures
  21. A shell model for the simulation of rhombohedral carbonate minerals and their point defects
  22. Optical properties of natural and cation-exchanged heulandite group zeolites
  23. The crystal structure of gearksutite, CaAlF4(OH)· H2O
  24. A new anhydrous amphibole from the Eifel region, Germany: Description and crystal structure of obertiite, NaNa2(Mg3Fe3+Ti4+)Si8O22O2
  25. Kinoshitalite, Ba(Mg)3(Al2Si2)O10(OH,F)2, a brittle mica from a manganese deposit in Oman: Paragenesis and crystal chemistry
  26. The crystal structure of parisite-(Ce), Ce2CaF2(CO3)3
  27. High-pressure synthesis of Na2Mg6Si6O18(OH)2—a new hydrous silicate phase isostructural with aenigmatite
https://doi.org/10.2138/am-2000-0113

Articles in the same Issue

  1. Eclogite-facies relics and inferred ultrahigh-pressure metamorphism in the North Dabie Complex, central-eastern China
  2. Application of INVEQ to the geothermobarometry of metamorphic rocks near a kyanite-sillimanite isograd, Mica Creek, British Columbia
  3. Microstructural characterization of metamorphic magnetite crystals with implications for oxygen isotope distribution
  4. Coexisting monazite and allanite in peraluminous granitoids of the TribečMountains, Western Carpathians
  5. Effect of alkalis, phosphorus, and water on the surface tension of haplogranite melt
  6. Direct observation of immiscibility in pyrope-almandine-grossular garnet
  7. On the cluster analysis of grains and crystals in rocks
  8. Experimental approach to constrain second critical end points in fluid/silicate systems: Near-solidus fluids and melts in the system albite-H2O
  9. Estimation and testing of standard molar thermodynamic properties of tourmaline end-members using data of natural samples
  10. An investigation of matrix effects in the analysis of fluorine in humite-group minerals by EMPA, SIMS, and SREF
  11. New data on the crystal-chemistry of fluoborite by means of SREF, SIMS, and EMP analysis
  12. Effect of aluminum on Ti-coordination in silicate glasses: A XANES study
  13. XAFS study of Cu model compounds and Cu2+ sorption products on amorphous SiO2, γ-Al2O3, and anatase
  14. Oxidation-reduction mechanism of iron in dioctahedral smectites: I. Crystal chemistry of oxidized reference nontronites
  15. Oxidation-reduction mechanism of iron in dioctahedral smectites: II. Crystal chemistry of reduced Garfield nontronite
  16. 15N NMR study of nitrate ion structure and dynamics in hydrotalcite-like compounds
  17. 29Si and 27Al MAS-NMR spectroscopy of b-eucryptite (LiAlSiO4): The enthalpy of Si,Al ordering
  18. The nuclear and magnetic structure of “white rust”—Fe(OH0.86D0.14)2
  19. In-situ study of the R3̅ to R3̅c phase transition in the ilmenite-hematite solid solution using time-of-flight neutron powder diffraction
  20. In situ X-ray diffraction investigation of lawsonite and zoisite at high pressures and temperatures
  21. A shell model for the simulation of rhombohedral carbonate minerals and their point defects
  22. Optical properties of natural and cation-exchanged heulandite group zeolites
  23. The crystal structure of gearksutite, CaAlF4(OH)· H2O
  24. A new anhydrous amphibole from the Eifel region, Germany: Description and crystal structure of obertiite, NaNa2(Mg3Fe3+Ti4+)Si8O22O2
  25. Kinoshitalite, Ba(Mg)3(Al2Si2)O10(OH,F)2, a brittle mica from a manganese deposit in Oman: Paragenesis and crystal chemistry
  26. The crystal structure of parisite-(Ce), Ce2CaF2(CO3)3
  27. High-pressure synthesis of Na2Mg6Si6O18(OH)2—a new hydrous silicate phase isostructural with aenigmatite
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