Calcite precipitation dominates the electrical signatures of zero valent iron columns under simulated field conditions [electronic resource].

Published: Berkeley, Calif. : Lawrence Berkeley National Laboratory, 2009.
Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy.
Additional Creators: Lawrence Berkeley National Laboratory and United States. Department of Energy. Office of Scientific and Technical Information

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Summary

Calcium carbonate is a secondary mineral precipitate influencing zero valent iron (ZVI) barrier reactivity and hydraulic performance. We conducted column experiments to investigate electrical signatures resulting from concurrent CaCO₃ and iron oxides precipitation under simulated field geochemical conditions. We identified CaCO₃ as a major mineral phase throughout the columns, with magnetite present primarily close to the influent based on XRD analysis. Electrical measurements revealed decreases in conductivity and polarization of both columns, suggesting that electrically insulating CaCO₃ dominates the electrical response despite the presence of electrically conductive iron oxides. SEM/EDX imaging suggests that the electrical signal reflects the geometrical arrangement of the mineral phases. CaCO₃ forms insulating films on ZVI/magnetite surfaces, restricting charge transfer between the pore electrolyte and ZVI particles, as well as across interconnected ZVI particles. As surface reactivity also depends on the ability of the surface to engage in redox reactions via charge transfer, electrical measurements may provide a minimally invasive technology for monitoring reactivity loss due to CaCO₃ precipitation. Comparison between laboratory and field data shows consistent changes in electrical signatures due to iron corrosion and secondary mineral precipitation.

Report Numbers

E 1.99:lbnl-2154e
lbnl-2154e

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Note

Published through SciTech Connect.
06/01/2009.
"lbnl-2154e"
Journal of Contaminant Hydrology 106 3-4 ISSN 0169-7722; JCOHE6 FT
Slater, L.; LaBrecque, D.; Versteeg, R.; Wu, Yuxin.
Earth Sciences Division

Funding Information

DE-AC02-05CH11231

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