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Hexavalent chromium, Cr(VI), is a highly toxic carcinogen occurring in natural and industrial environments. Pathways to economical reduction to the more benign trivalent form, Cr(III), are necessary for treatment of contaminated groundwater. Magnetite’s (Fe3O4) mixture of Fe(II) and Fe(III) make it a promising material for remediation. This study investigated the mechanisms for reduction of Cr(VI) catalyzed by Fe3O4as a redox mediator in the presence of oxalic acid in HClO4and SO42−solutions, a system where the interactions among these species are not fully understood. The reduction of Cr(VI) in different anion environments is first measured on an Au rotating disk electrode. SO42−inhibits the formation of a passivation layer and Cl-partially inhibits passivation. The reduction of Cr(VI) on Fe3O4is limited by the availability of Fe(II) surface sites. Addition of oxalic acid works synergistically through liberation of Fe(II)-oxalate and soluble Cr(III)-oxalate products. A combination of Fe3O4activated by exposure to oxalic acid and use of an oxalic acid solution as a medium for reduction of Cr(VI) produces over 97% removal of Cr(VI). These results provide relevant insights regarding interactions of Fe3O4with organic acids and the anion environment which lead to the effective reduction of Cr(VI).
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Deconvoluting charge-transfer, mass transfer, and ohmic resistances in phosphonic acid–sulfonic acid ionomer binders used in electrochemical hydrogen pumps
This work reveals how electrode binders affect reaction kinetics, ionic conductivity, and gas transport in electrochemical hydrogen pumps (EHPs). Using a blend of phosphonic acid and perfluorosulfonic acid ionomers as the electrode binder, an EHP was operated at 5 A cm−2.
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- Award ID(s):
- 2143056
- PAR ID:
- 10471067
- Publisher / Repository:
- Royal Society of Chemistry
- Date Published:
- Journal Name:
- Energy & Environmental Science
- ISSN:
- 1754-5692
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/D3EE01776A
