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Inner-Helmholtz pot...
Inner-Helmholtz potential development at the hematite (α-Fe2O3) (0 0 1) surface
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- Boily, Jean-François (författare)
- Umeå universitet,Kemiska institutionen
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Chatman, Shawn (författare)
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Rosso, Kevin M (författare)
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(creator_code:org_t)
- Elsevier BV, 2011
- 2011
- Engelska.
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Ingår i: Geochimica et Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533. ; 75:15, s. 4113-4124
- Relaterad länk:
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https://urn.kb.se/re...
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visa fler...
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https://doi.org/10.1...
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Abstract
Ämnesord
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- Electric potentials of the (0 0 1) surface of hematite were measured as a function of pH and ionic strength in solutions of sodium nitrate and oxalic acid using the single-crystal electrode approach. The surface is predominantly charge-neutral in the pH 4–14 range, and develops a positive surface potential below pH 4 due to protonation of μ-OH0 sites (pK1,1,0,int = −1.32). This site is resilient to deprotonation up to at least pH 14 (−pK−1,1,0,int ≫ 19). The associated Stern layer capacitance of 0.31–0.73 F/m2 is smaller than typical values of powders, and possibly arises from a lower degree of surface solvation. Acid-promoted dissolution under elevated concentrations of HNO3 etches the (0 0 1) surface, yielding a convoluted surface populated by sites. The resulting surface potential was therefore larger under these conditions than in the absence of dissolution. Oxalate ions also promoted (0 0 1) dissolution. Associated electric potentials were strongly negative, with values as large as −0.5 V, possibly from metal-bonded interactions with oxalate. The hematite surface can also acquire negative potentials in the pH 7–11 range due to surface complexation and/or precipitation of iron species (0.0038 Fe/nm2) produced from acidic conditions. Oxalate-bearing systems also result in negative potentials in the same pH range, and may include ferric-oxalate surface complexes and/or surface precipitates. All measurements can be modeled by a thermodynamic model that can be used to predict inner-Helmholtz potentials of hematite surfaces.
Ämnesord
- NATURVETENSKAP -- Kemi (hsv//swe)
- NATURAL SCIENCES -- Chemical Sciences (hsv//eng)
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