An attenuated total reflectance IR study of silicic acid adsorbed onto a ferric oxyhydroxide surface

Swedlund, Peter J.; Miskelly, Gordon M.; McQuillan, A. James

doi:10.1016/j.gca.2009.04.007

Cited by 74 publications

(134 citation statements)

References 72 publications

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“…However, recent studies have shown that silica could also occur on the surface [30][31][32]. Detailed infrared spectra studies of adsorbed silica on ferrihydrite surfaces show the formation of bidentate surface complexes composed of monomeric silicate species at low silica ratios, similar to the concentrations used in this study [33]. Formation of these silica surface complexes results in a net release of protons that decreases the positive charge on the precipitate surface [34].…”

Section: Characterization Of Initial Adsorbentssupporting

confidence: 66%

Dissolved Silica Effects on Adsorption and Co-Precipitation of Sb(III) and Sb(V) with Ferrihydrite

2018

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Elevated antimony concentrations in aqueous environments from anthropogenic sources are becoming of global concern. In this respect iron oxides are known to strongly adsorb aqueous antimony species with different oxidation states, but the effect of silica on the removal characteristics is not well understood despite being a common component in the environment. In this study, ferrihydrite was synthesized at various Si/Fe molar ratios to investigate its adsorption and co-precipitation behaviors with aqueous antimony anionic species, Sb(III) and Sb(V). The X-ray diffraction analyses of the precipitates showed two broad diffraction features at approximately 35 • and 62 • 2θ, which are characteristics of 2-line ferrihydrite, but no significant shifts in peak positions in the ferrihydrite regardless of the Si/Fe ratios. The infrared spectra showed a sharp band at~930 cm −1 , corresponding to asymmetric stretching vibrations of Si-O-Fe bonds which increased in intensity with increasing Si/Fe molar ratios. Further, the surface charge on the precipitates became more negative with increasing Si/Fe molar ratios. The adsorption experiments indicated that Sb(V) was preferentially adsorbed under acidic conditions which decreased dramatically with increasing pH while the adsorption rate of Sb(III) ions was independent of pH. However, the presence of silica suppressed the adsorption of both Sb(III) and Sb(V) ions. The results showed that Sb(III) and Sb(V) ions were significantly inhibited by co-precipitation with ferrihydrite even in the presence of silica by isomorphous substitution in the ferrihydrite crystal structure.

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Section: Characterization Of Initial Adsorbentssupporting

confidence: 66%

Dissolved Silica Effects on Adsorption and Co-Precipitation of Sb(III) and Sb(V) with Ferrihydrite

2018

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“…The total sorbed Si concentration (0.02 mol Si:mole Fe) is well below site saturation, according to Dzombak and Morel (1990) (e.g., Type 2 sites at 0.2 mol:mol Fe). ATR-IR measurements of adsorbed silica on ferrihydrite at this surface loading indicate the presence of approximately 75% monomeric surface complexes (Swedlund et al, 2009). Increased surface loadings beyond this value encourage surface polymerization, decreasing concentrations of the monomeric surface complex, and Si precipitation around aggregate surfaces (Swedlund et al, 2009;Dyer et al, 2010).…”

Section: Discussionmentioning

confidence: 85%

“…ATR-IR measurements of adsorbed silica on ferrihydrite at this surface loading indicate the presence of approximately 75% monomeric surface complexes (Swedlund et al, 2009). Increased surface loadings beyond this value encourage surface polymerization, decreasing concentrations of the monomeric surface complex, and Si precipitation around aggregate surfaces (Swedlund et al, 2009;Dyer et al, 2010). While retarding oxidative recrystallization, we have observed no influence of sorbed Si at this concentration on reductive ferrihydrite mineralization in previous studies .…”

Section: Discussionmentioning

confidence: 85%

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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“…The Si-O-Fe-bond disappears at a molar Si/Fe ratio <0.03 -0.04. Oligomeric Si species, which develop at molar Si/Fe ratios >0.01 and pH = 3 (Swedlund et al, 2009) could not be traced due to superposing bands from adsorbed sulfate. Although the molar Si/Fe ratio was 0.02 -0.06 in our study, we assume the predominance of monomeric Si species owing to the effluent pH ~ 7.5 (Table 1), which effectively inhibits Si polymerization at the Fe oxide surface (Doelsch et al, 2001).…”

Section: Elemental Composition Of the Fe-om Co-precipitatesmentioning

confidence: 98%

Structure and composition of Fe–OM co-precipitates that form in soil-derived solutions

Fritzsche

Schröder

Wieczorek

et al. 2015

Geochimica et Cosmochimica Acta

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Iron oxides represent a substantial fraction of secondary minerals and particularly affect the reactive properties of natural systems in which they formed, e.g. in soils and sediments. Yet, it is still obscure how transient conditions in the solution will affect the properties of in situ precipitated Fe oxides. Transient compositions, i.e. compositions that change with time, arise due to predominant non-equilibrium states in natural systems, e.g. between liquid and solid phases in soils. In this study, we characterize Fe-OM co-precipitates that formed in pH-neutral exfiltrates from anoxic topsoils under transient conditions. We applied soil column outflow experiments, in which Fe 2+ was discharged with the effluent from anoxic soil and subsequently oxidized in the effluent due to contact with air. Our study features three novel aspects being unconsidered so far: 3

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An attenuated total reflectance IR study of silicic acid adsorbed onto a ferric oxyhydroxide surface

Cited by 74 publications

References 72 publications

Dissolved Silica Effects on Adsorption and Co-Precipitation of Sb(III) and Sb(V) with Ferrihydrite

Dissolved Silica Effects on Adsorption and Co-Precipitation of Sb(III) and Sb(V) with Ferrihydrite

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

Structure and composition of Fe–OM co-precipitates that form in soil-derived solutions

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