Redistribution of Electron Equivalents between Magnetite and Aqueous Fe ²⁺ Induced by a Model Quinone Compound AQDS

Journal Article · Wed Jan 23 00:00:00 EST 2019 · Environmental Science and Technology

DOI:https://doi.org/10.1021/acs.est.8b05098· OSTI ID:1506691

Peng, Huan ^[1]; Pearce, Carolyn I.  ^[2]; N’Diaye, Alpha T. ^[3]; Zhu, Zhenli ^[4]; Ni, Jinren  ^[5]; Rosso, Kevin M.  ^[2]; Liu, Juan  ^[5]

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1. The Key Laboratory of Water and Sediment Sciences, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China; State Key Laboratory of Biogeology and Environmental Geology, School of Earth Sciences, China University of Geosciences, Wuhan, Hubei 430074, China
2. Pacific Northwest National Laboratory, Richland, Washington 99352, United States
3. Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
4. State Key Laboratory of Biogeology and Environmental Geology, School of Earth Sciences, China University of Geosciences, Wuhan, Hubei 430074, China
5. The Key Laboratory of Water and Sediment Sciences, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China

The complex interactions between magnetite and aqueous Fe2+ (Fe2+(aq)) pertain to many biogeochemical redox processes in anoxic subsurface environments. The effect of natural organic matter, abundant in these same environments, on Fe2+(aq)–magnetite interactions is an additional complex that remains poorly understood. We investigated the influence of a model quinone molecule anthraquinone-2,6-disulfonate (AQDS) on Fe2+(aq)–magnetite interactions by systematically studying equilibrium Fe2+(aq) concentrations, rates and extents of AQDS reduction, and structural versus surface-localized Fe(II)/Fe(III) ratios in magnetite under different controlled experimental conditions. The equilibrium concentration of Fe2+(aq) in Fe2+-amended magnetite suspensions with AQDS proportionally changes with solution pH or initial AQDS concentration, but independent of magnetite loadings through the solid concentrations that were studied here. The rates and extents of AQDS reduction by Fe2+-amended magnetite proportionally increased with solution pH, magnetite loading, and initial Fe2+(aq) concentration, which correlates with the corresponding change of reduction potentials for the Fe2+–magnetite system. AQDS reduction by surface-associated Fe(II) in the Fe2+–magnetite suspensions induces solid-state migration of electron equivalents from particle interiors to the near-surface region and the production of nonmagnetic Fe(II)-containing species, which inhibits Fe2+(aq) incorporation or electron injection into the magnetite structure. This study demonstrates the significant influence of quinones on reductive activity of the Fe2+–magnetite system.

• Research Organization: Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1506691
• Report Number(s): PNNL-SA-142677
• Journal Information: Environmental Science and Technology, Vol. 53, Issue 4; ISSN 0013-936X
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English