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Protein Film Infrared Electrochemistry Demonstrated for Study of H2 Oxidation by a [NiFe] Hydrogenase
Published on: December 4, 2017
Inhibited Cr(VI) reduction by aqueous Fe(II) under hyperalkaline conditions
Y Thomas He1, Chia-Chen Chen, Samuel J Traina
1Environmental Science Graduate Program, The Ohio State University, Columbus, Ohio 43210, USA. heyong@vt.edu
Hexavalent chromium (Cr(VI)) reduction by dissolved iron(II) (Fe(II)) is rapid in hyperalkaline conditions. Higher Fe(II):Cr(VI) ratios increase Cr(VI) removal, though nonstoichiometry occurs due to iron precipitation and oxidation.
Area of Science:
- Environmental Chemistry
- Inorganic Chemistry
- Nuclear Waste Management
Background:
- Hyperalkaline pH conditions are characteristic of fluid wastes from nuclear weapons programs.
- Hexavalent chromium (Cr(VI)) is a toxic contaminant often found in industrial and nuclear waste streams.
- Dissolved iron(II) (Fe(II)) is a potential reductant for Cr(VI) remediation.
Purpose of the Study:
- To investigate the reduction of Cr(VI) by Fe(II) under hyperalkaline pH conditions.
- To understand the reaction kinetics and stoichiometry of this process.
- To characterize the resulting precipitates.
Main Methods:
- Experimental investigation of Cr(VI) reduction by Fe(II) in alkaline solutions.
- Varying the Fe(II):Cr(VI) ratio to observe its effect on reduction.
- Analysis of solution and precipitate composition.
- Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy for precipitate characterization.
Main Results:
- Cr(VI) reduction by Fe(II) is rapid in alkaline solutions.
- Increased Fe(II):Cr(VI) ratio enhances Cr(VI) removal and reduction.
- Nonstoichiometric reduction is observed, attributed to Fe(II) precipitation and oxidation.
- Cr(III) precipitates as mixed iron-chromium (oxy)hydroxides with a Cr:Fe ratio of 1:3.
- EXAFS data indicates a spinel-type structure (chromite) in the precipitates.
Conclusions:
- Fe(II) is an effective reductant for Cr(VI) even in hyperalkaline environments.
- Precipitation and oxidation of Fe(II) limit the efficiency of Cr(VI) reduction.
- The study elucidates the fate of chromium in alkaline waste streams, forming stable precipitates.
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