Surface complexation of arsenic(V) to iron(III) (hydr)oxides: structural mechanism from ab initio molecular geometries and EXAFS spectroscopy

Sherman, David M.; Randall, Sarah

doi:10.1016/s0016-7037(03)00237-0

Cited by 638 publications

(582 citation statements)

References 29 publications

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“…22,33,34 The result confirmed that the tetrahedral AsO 4 structure did not change under the competition of F. The second peak in the FT was attributed to 1.3−1.6 Ti atoms at an interatomic distance of 3.33−3.35 Å. In line with our previous study, 11 the As−Ti distances and coordination numbers suggested that As(V) formed bidentate binuclear inner-sphere complexes on TiO 2 .…”

Section: ■ Introductionsupporting

confidence: 88%

Fabrication, Characterization, and Application of a Composite Adsorbent for Simultaneous Removal of Arsenic and Fluoride

Jing

Cui

Hao

et al. 2012

ACS Appl. Mater. Interfaces

103

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Coexisting arsenic (As) and fluoride (F) in groundwater poses severe health risks worldwide. Highly efficient simultaneous removal of As and F is therefore of great urgency and high priority. The purpose of this study was to fabricate a novel composite adsorbent and explore the mechanism for concurrent removal of As(V) and F at the molecular level. This bifunctional adsorbent with titanium and lanthanum oxides impregnated on granular activated carbon (TLAC) exhibits a pronounced As(V) and F adsorption capacity over commercially available iron-and aluminumbased adsorbents for synthetic and real contaminated groundwater samples. Synchrotron-based X-ray microfluorescence analysis demonstrates that La and Ti were homogeneously distributed on TLAC. Extended X-ray absorption fine structure spectroscopic results suggest that As(V) formed bidentate binuclear surface complex as evidenced by an averaged Ti−As bond distance of 3.34 Å in the presence of F. Adsorption tests and Fourier transform infrared spectroscopy analysis indicate that F was selectively adsorbed on lanthanum oxides. The surface configurations constrained with the spectroscopic results were formulated in the charge distribution multisite complexation model to describe the competitive adsorption behaviors of As(V) and F. The results of this study indicate that TLAC could be used as an effective adsorbent for simultaneous removal of As(V) and F.

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Section: ■ Introductionsupporting

confidence: 88%

Fabrication, Characterization, and Application of a Composite Adsorbent for Simultaneous Removal of Arsenic and Fluoride

Jing

Cui

Hao

et al. 2012

ACS Appl. Mater. Interfaces

103

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“…The geometry and energy were calculated using the 6-31+G(d) basis set for O and H; the 6-311+G(d) basis set for As; and the LANL2DZ relativistic effective core potential (RECP) basis set for Ti transition metal [28,29]. To eliminate boundary effects and reduce charge on the clusters, the dangling bonds of boundary O atoms were saturated with H atoms [2][3][4]28].…”

Section: Methods and Theorymentioning

confidence: 99%

“…Electronic structure methods such as density functional theory (DFT) were widely used to calculate the adsorption structures of oxyanions on mineral surfaces [1][2][3][4]. However, the details of the formation of the surface complexes are little discussed.…”

Section: Introductionmentioning

confidence: 99%

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Studies on the reaction pathway of arsenate adsorption at water–TiO2 interfaces using density functional theory

Pan

Zhang

2011

Journal of Colloid and Interface Science

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a b s t r a c tReaction pathway information of transition states and intermediate species is crucial for understanding the adsorption mechanism of pollutants at mineral-water interfaces. However, it has been difficult to obtain such information using existing experiments. Here, the activation barriers, transition states, intermediate species and surface complexes of arsenate adsorption on TiO 2 surfaces were studied using DFTbased reaction pathway calculations. The results indicated that the bidentate binuclear (BB) adsorption structure was formed through a monodentate mononuclear (MM) metastable-equilibrium adsorption (MEA) state. A two-step adsorption mechanism was proposed on the basis of the detailed picture of bond breaking and bond formation during each reaction step. When the adjacent surface sites were occupied, the transform from MM mode to BB mode was greatly inhibited so that both MM and BB coexisted in the equilibrium adsorption sample. The BB complex was energetically more stable than the MM complex, and so, the adsorption irreversibility was fundamentally related to the ratio BB:MM in the final equilibrium state. This mechanism may also explain the initial concentration effect, where, for the given adsorption experiment of arsenate on TiO 2 under the same thermodynamic conditions, both equilibrium constants and the BB:MM ratio in equilibrium adsorption samples changed with the reaction kinetics.

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“…To eliminate boundary effects and reduce charge on the clusters, the dangling bonds of O atoms were saturated with H atoms. 16,24,25 The geometry and energy were calculated by use of the 6-31G(d) basis set for O and H and the LANL2DZ relativistic effective core potential basis set for Zn and Ti transition metals.…”

Section: Introductionmentioning

confidence: 99%

Coordination Structure of Adsorbed Zn(II) at Water−TiO₂Interfaces

He¹,

Pan²,

Zhang³

et al. 2011

Environ. Sci. Technol.

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The local structure of aqueous metal ions on solid surfaces is central to understanding many chemical and biological processes in soil and aquatic environments. Here, the local coordination structure of hydrated Zn(II) at water-TiO 2 inter faces was identified by extended X-ray absorption fine structure (EXAFS) and X-ray absorption near-edge structure (XANES) spectroscopy combined with density functional theory (DFT) calculations. A nonintegral coordination number of average ~4.5 O atoms around a central Zn atom was obtained by EXAFS analy sis. DFT calculations indicated that this coordination structure was consistent with the mixture of 4-coordinated bidentate bi nuclear (BB) and 5-coordinated bidentate mononuclear (BM) metastable equilibrium adsorption (MEA) states. The BB com plex has 4-coordinated Zn, while the monodentate mononuclear (MM) complex has 6-coordinated Zn, and a 5-coordinated adsor bed Zn was found in the BM adsorption mode. DFT calculated energies showed that the lower-coordinated BB and BM modes were thermodynamically more favorable than the higher-coordinated MM MEA state. The experimentally observed XANES fingerprinting provided additional direct spectral evidence of 4-and 5 coordinated Zn-O modes. The overall spectral and computational evidence indicated that Zn(II) can occur in 4-, 5-, and 6-oxygen coordinated sites in different MEA states due to steric hindrance effects, and the coexistence of different MEA states formed the multiple coordination environments.

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Surface complexation of arsenic(V) to iron(III) (hydr)oxides: structural mechanism from ab initio molecular geometries and EXAFS spectroscopy

Cited by 638 publications

References 29 publications

Fabrication, Characterization, and Application of a Composite Adsorbent for Simultaneous Removal of Arsenic and Fluoride

Fabrication, Characterization, and Application of a Composite Adsorbent for Simultaneous Removal of Arsenic and Fluoride

Studies on the reaction pathway of arsenate adsorption at water–TiO2 interfaces using density functional theory

Coordination Structure of Adsorbed Zn(II) at Water−TiO₂Interfaces

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Surface complexation of arsenic(V) to iron(III) (hydr)oxides: structural mechanism from ab initio molecular geometries and EXAFS spectroscopy

Cited by 638 publications

References 29 publications

Fabrication, Characterization, and Application of a Composite Adsorbent for Simultaneous Removal of Arsenic and Fluoride

Fabrication, Characterization, and Application of a Composite Adsorbent for Simultaneous Removal of Arsenic and Fluoride

Studies on the reaction pathway of arsenate adsorption at water–TiO2 interfaces using density functional theory

Coordination Structure of Adsorbed Zn(II) at Water−TiO2Interfaces

Contact Info

Product

Resources

About

Coordination Structure of Adsorbed Zn(II) at Water−TiO₂Interfaces