Surface chemistry of disordered mackinawite (FeS)

Disordered mackinawite, FeS, is the first formed iron sulfide in ambient sulfidic environments and has a highly reactive surface. In this study, the solubility and surface chemistry of FeS is described. Its solubility in the neutral pH range can be described by K s app = {Fe 2+} · {H 2S(aq)} · {H +}...

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Bibliographic Details
Published in:Geochimica et cosmochimica acta 2005-07, Vol.69 (14), p.3469-3481
Main Authors: Wolthers, Mariëtte, Charlet, Laurent, van Der Linde, Peter R., Rickard, David, van Der Weijden, Cornelis H.
Format: Article
Language:English
Subjects:
Density
domain_sde.mcg.cpe
Earth Sciences
Editors
Environmental Sciences
Geochemistry
Global Changes
Sciences of the Universe
Solubility
Sulfides
Sulfur
Surface chemistry
Titration
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Summary:Disordered mackinawite, FeS, is the first formed iron sulfide in ambient sulfidic environments and has a highly reactive surface. In this study, the solubility and surface chemistry of FeS is described. Its solubility in the neutral pH range can be described by K s app = {Fe 2+} · {H 2S(aq)} · {H +} −2 = 10 +4.87±0.27. Acid-base titrations show that the point of zero charge (PZC) of disordered mackinawite lies at pH ∼7.5. The hydrated disordered mackinawite surface can be best described by strongly acidic mono-coordinated and weakly acidic tricoordinated sulfurs. The mono-coordinated sulfur site determines the acid-base properties at pH < PZC and has a concentration of 1.2 × 10 −3 mol/g FeS. At higher pH, the tricoordinated sulfur, which has a concentration of 1.2 × 10 −3 mol/g FeS, determines surface charge changes. Total site density is 4 sites nm −2. The acid-base titration data are used to develop a surface complexation model for the surface chemistry of FeS.
ISSN:0016-7037
1872-9533
DOI:10.1016/j.gca.2005.01.027