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Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses
Published on: June 7, 2018
Ni(II) complexation to amorphous hydrous ferric oxide: an X-ray absorption spectroscopy study
Ying Xu1, Lisa Axe, Thipnakarin Boonfueng
1ConocoPhillips Company, Ponca City, OK 74602, USA.
Journal of Colloid and Interface Science
|June 15, 2007
Summary
Nickel sorption to hydrous ferric oxide (HFO) was studied using extended X-ray absorption fine structure (EXAFS) analysis. Ni(II) forms inner-sphere complexes on HFO surfaces, influencing metal mobility and distribution in the environment.
Area of Science:
- Environmental Chemistry
- Geochemistry
- Materials Science
Background:
- Nickel (Ni(II)) sorption onto iron oxides, particularly hydrous ferric oxide (HFO), is crucial for understanding its environmental fate.
- Accurate mechanistic models are needed to predict Ni distribution, mobility, and bioavailability.
Purpose of the Study:
- To elucidate the adsorption mechanisms of Ni(II) onto amorphous iron oxide (HFO) using EXAFS spectroscopy.
- To identify the specific surface complex formed by Ni(II) on HFO.
- To provide data for constraining surface complexation models.
Main Methods:
- Extended X-ray absorption fine structure (EXAFS) analysis was performed on Ni(II) sorbed to HFO.
- Coprecipitation experiments were conducted to study Ni(II) interactions.
- Structural parameters, including Ni-O and Ni-Fe distances, were determined.
Main Results:
- Ni(II) forms inner-sphere mononuclear bidentate complexes on HFO surfaces, with specific Ni-O and Ni-Fe bond distances.
- The formation of metastable alpha-Ni(OH)(2) was observed under certain conditions.
- Ni(II) sorption inhibited the transformation of amorphous HFO into crystalline forms.
- Ni(2+) did not substitute for Fe(3+) within the oxide structure.
Conclusions:
- The study identified specific Ni(II) surface complexes on HFO, crucial for environmental modeling.
- These findings improve predictions of metal distribution at the iron oxide/aqueous interface.
- Ni(II) adsorption mechanisms on amorphous iron oxides are systematically addressed.
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