ATR-FTIR spectroscopic characterization of coexisting carbonate surface complexes on hematite

Bargar, John R.; Kubicki, James D.; Reitmeyer, Rebecca; Davis, James A.

doi:10.1016/j.gca.2004.08.002

Cited by 164 publications

(265 citation statements)

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“…Numerous studies applying QM, or specifically density functional theory (DFT) methods [113,114], use models similar to those shown in Figures 2A-C. For example, DFT methods have been used to study the thermodynamics [91, [115][116][117], vibrational frequencies [75,[118][119][120][121], kinetics [120][121][122], ligand effects [87], oxidation-reduction reactions [123], and the coordination of adsorbed As [90,91,117,119,[124][125][126][127][128][129][130][131][132].…”

Section: Studying As Adsorption With Quantum Mechanics Modeling Methodsmentioning

confidence: 99%

“…FTIR and Raman studies are useful for determining the bonding configurations between As species and mineral surfaces. When As adsorbs as an inner-sphere complex, characteristic vibrational frequency shifts are observable [74][75][76][77][78][79]. XANES spectroscopy can provide information about the oxidation state of As that is adsorbed to mineral surfaces [80][81][82][83][84], and can determine if the oxidation state of As or the surface changes during the adsorption process [78,85].…”

Section: Studying As Adsorption With Experimentsmentioning

confidence: 99%

“…Figure 1 shows examples of a tetrahydrated Fe (oxyhydr)oxide cluster, (Fe 2 (OH) 6 . Hydration can be a key in accurately predicting structures and frequencies of anionic surface complexes because they are both a function of the hydration state of the sample [75,157]. The interatomic distances calculated in each model surface complex were compared to As-O bond lengths and As-Fe distances obtained from EXAFS spectra [46,[80][81][82][86][87][88][89][90][91][92].…”

Section: Molecular Orbital Theory Calculations With Fe Clustersmentioning

confidence: 99%

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Arsenic Adsorption onto Minerals: Connecting Experimental Observations with Density Functional Theory Calculations

2014

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A review of the literature about calculating the adsorption properties of arsenic onto mineral models using density functional theory (DFT) is presented. Furthermore, this work presents DFT results that show the effect of model charge, hydration, oxidation state, and DFT method on the structures and adsorption energies for As (oxyhydr)oxide cluster models were calculated using planewave and cluster-model DFT methods.

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Section: Studying As Adsorption With Quantum Mechanics Modeling Methodsmentioning

confidence: 99%

Section: Studying As Adsorption With Experimentsmentioning

confidence: 99%

Section: Molecular Orbital Theory Calculations With Fe Clustersmentioning

confidence: 99%

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Arsenic Adsorption onto Minerals: Connecting Experimental Observations with Density Functional Theory Calculations

2014

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“…Infrared spectroscopy is the main source of information on the structural state of C 4ϩ in soil minerals (20)(21)(22). Overall, the spectra indicate that C 4ϩ is present in these minerals as a carbonate ion, but with the trigonal symmetry broken as indicated by splitting of the asymmetric stretching frequency.…”

Section: Vibrational Spectroscopy and Isotope Fractionation Factorsmentioning

confidence: 99%

“…at 1,550-1,515 cm Ϫ1 and 1,375-1,345 cm Ϫ1 were assigned to the 3a and 3b (20)(21)(22). It is rare, however, for calculated harmonic frequencies with the B3LYP functional to underestimate measured frequencies.…”

Section: Vibrational Spectroscopy and Isotope Fractionation Factorsmentioning

confidence: 99%

Calculation of site-specific carbon-isotope fractionation in pedogenic oxide minerals

Rustad

Zarzycki²

2008

Proc. Natl. Acad. Sci. U.S.A.

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atmospheric carbon dioxide ͉ electronic structure calculations ͉ paleosols ͉ goethite ͉ gibbsite T he paleosol carbon-isotope method is one of the major techniques for reconstructing the composition of the ancient atmosphere (1, 2). The depth-dependent mixing of respirative CO 2 from soil ( 13 C-depleted) with atmospheric CO 2 ( 13 Cenriched) can be preserved in soil minerals and has been used to infer atmospheric PCO 2 and respiration rates in paleosols (3). The idea was directed originally at soil carbonate minerals (4) and later applied to the CO 2 component of pedogenic goethite (␣-FeOOH) (5-7) and gibbsite (Al(OH) 3 ) (8, 9). The fractionation between mineral-dissolved CO 2 [CO 2 (m)] and CO 2 (g) is a key factor in the technique because it determines how the respired CO 2 vs. atmospheric CO 2 mixing profile is imprinted onto the soil mineralogy. Direct measurements of the CO 2 (m)-CO 2 (g) fractionation factors for (oxy)hydroxide soil minerals have thus far been elusive. The small values (0 to ϩ2.5 per mil) that have been provisionally implied are surprising because, by analogy with carbonate minerals, a 13 C-enriched fractionation factor (close to ϩ10 per mil) might be expected (10,11).In carbonate minerals with the calcite and aragonite structure, the overwhelming majority of carbonate ions are in a single crystallographic site that governs the equilibrium isotope fractionation. In contrast, occlusion of CO 2 in oxide soil minerals at trace concentrations could involve multiple sites with varying populations, possibly depending on the kinetics and conditions of soil formation. For goethite, it has commonly been assumed that the open pseudochannels parallel to the c crystallographic axis are the major host for CO 2 (m) (12), but this has not been definitively demonstrated, and it is possible that other types of sites could be involved in the uptake of CO 2 (m). An important question is then whether the various kinds of CO 2 (m) sites would have large differences in their equilibrium 12/13 C isotope fractionation factors. Little attention has been given to the possibility of heterogeneous chemical speciation of CO 2 (m) within the host mineral. Site heterogeneity would complicate the interpretation of the carbon isotope records preserved in these minerals. At the same time, a better understanding of the crystal chemistry of CO 2 (m) defects in oxide/oxhydroxide minerals and their isotopic fractionations could serve as a foundation for a much more sensitive paleoclimate indicator than would be possible with knowledge of only the overall isotopic composition. Knowledge of site-specific isotopic signatures in minerals could have much wider applicability than the CO 2 -Fe,Al(oxy)hydroxide system.Although the experimental difficulties of sampling these individual sites might be daunting, accurate theoretical calculation of the potential fractionations is now feasible by using methods of quantum chemistry. During the last several years, there has been notable success in first-principles calculation of equilibriu...

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Biogeochemical Mechanisms of Arsenic Mobilization and Sequestration

Campbell

Hering

2008

Arsenic Contamination of Groundwater

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ATR-FTIR spectroscopic characterization of coexisting carbonate surface complexes on hematite

Cited by 164 publications

References 40 publications

Arsenic Adsorption onto Minerals: Connecting Experimental Observations with Density Functional Theory Calculations

Arsenic Adsorption onto Minerals: Connecting Experimental Observations with Density Functional Theory Calculations

Calculation of site-specific carbon-isotope fractionation in pedogenic oxide minerals

Biogeochemical Mechanisms of Arsenic Mobilization and Sequestration

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