Phosphate bonding configuration on ferrihydrite based on molecular orbital calculations and XANES fingerprinting

Khare, Nidhi; Martin, James D.; Hesterberg, Dean

doi:10.1016/j.gca.2007.07.008

Cited by 116 publications

(103 citation statements)

References 27 publications

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“…Similar results at comparable P concentrations have been previously reported (Galvez et al, 1999;Borch et al, 2007). Phosphate is strongly adsorbed by ferrihydrite, apparently forming a stable bidentate surface complex at circumneutral pH (Arai and Sparks, 2001;Khare et al, 2007). Strong P adsorption decreases the ferrihydrite transformation rate by preventing the relatively soluble structure from dissolution and subsequent reprecipitation (Biber et al, 1994;Galvez et al, 1999;Majzlan, 2008).…”

Section: Influence Of Psupporting

confidence: 87%

The mineralogic transformation of ferrihydrite induced by heterogeneous reaction with bioreduced anthraquinone disulfonate (AQDS) and the role of phosphate

Zachara¹,

Kukkadapu²,

Peretyazhko³

et al. 2011

Geochimica et Cosmochimica Acta

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Bruce, "The mineralogic transformation of ferrihydrite induced by heterogeneous reaction with bioreduced anthraquinone disulfonate (AQDS) and the role of phosphate" (2011 Abstract Bioreduced anthraquinone-2,6-disulfonate (AH 2 DS; dihydro-anthraquinone) was reacted with a 2-line, Si-substituted ferrihydrite under anoxic conditions at neutral pH in PIPES buffer. Phosphate (P) and bicarbonate (C); common adsorptive oxyanions and media/buffer components known to effect ferrihydrite mineralization; and Fe(II) aq (as a catalytic mineralization agent) were used in comparative experiments. Heterogeneous AH 2 DS oxidation coupled with Fe(III) reduction occurred within 0.13-1 day, with mineralogic transformation occurring thereafter. The product suite included lepidocrocite, goethite, and/or magnetite, with proportions varing with reductant:oxidant ratio (r:o) and the presence of P or C. Lepidocrocite was the primary product at low r:o in the absence of P or C, with evidence for multiple formation pathways. Phosphate inhibited reductive recrystallization, while C promoted goethite formation. Stoichiometric magnetite was the sole product at higher r:o in the absence and presence of P. Lepidocrocite was the primary mineralization product in the Fe(II) aq system, with magnetite observed at near equal amounts when Fe(II) was high [Fe(II)/Fe(III)] = 0.5 and P was absent. P had a greater effect on reductive mineralization in the Fe(II) aq system, while AQDS was more effective than Fe(II) aq in promoting magnetite formation. The mineral products of the direct AH 2 DS-driven reductive reaction are different from those observed in AH 2 DS-ferrihydite systems with metal reducing bacteria, particularly in presence of P. Ó

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Section: Influence Of Psupporting

confidence: 87%

The mineralogic transformation of ferrihydrite induced by heterogeneous reaction with bioreduced anthraquinone disulfonate (AQDS) and the role of phosphate

Zachara¹,

Kukkadapu²,

Peretyazhko³

et al. 2011

Geochimica et Cosmochimica Acta

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“…Phosphate has a specific affinity to Mn oxides 8 and its coordination to Mn 3+ is expected to cause a red-shift of the d-d transition absorption band due to its electron-withdrawing property. 9 Meanwhile, a blue-shift of the Mn 3+ d-d transition from 510 to 470 nm was observed for Mn oxides following the coordination of electron-donating amine groups to Mn 3+ (trace 3, Fig. 1).…”

Section: Resultsmentioning

confidence: 95%

In situ UV-vis Absorption Spectra of Intermediate Species for Oxygen-Evolution Reaction on the Surface of MnO2 in Neutral and Alkaline Media

et al. 2014

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The mechanism of water oxidation by MnO 2 electrodes was investigated at various pH values, using in situ UV-vis absorption spectroscopy. The surface Mn 3+ formed as an intermediate species during water oxidation showed a d-d transition band with a peak at 510 nm at pH 6, while the peak shifted to 470 nm at pH 13. This shift of the absorption peak is attributed to the deprotonation of hydroxyl ligands of Mn. Interrelation between the protonation state of Mn 3+ and the O 2 evolution activity of MnO 2 electrocatalysts is discussed.

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“…However, the details of the formation of the surface complexes are little discussed. Because the adsorbate molecules may be generally ended on the surfaces in various adsorption modes [5][6][7][8], it is necessary to identify the interrelation of different adsorption structures to enhance our understanding of the adsorption of ions at mineral-water interfaces. Reaction pathway information containing transition states and intermediate species can provide a detailed picture of bond breaking and bond formation during each reaction step.…”

Section: Introductionmentioning

confidence: 99%

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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Phosphate bonding configuration on ferrihydrite based on molecular orbital calculations and XANES fingerprinting

Cited by 116 publications

References 27 publications

The mineralogic transformation of ferrihydrite induced by heterogeneous reaction with bioreduced anthraquinone disulfonate (AQDS) and the role of phosphate

The mineralogic transformation of ferrihydrite induced by heterogeneous reaction with bioreduced anthraquinone disulfonate (AQDS) and the role of phosphate

In situ UV-vis Absorption Spectra of Intermediate Species for Oxygen-Evolution Reaction on the Surface of MnO2 in Neutral and Alkaline Media

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

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