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Environ Sci Technol. 2017 Mar 21;51(6):3223-3232. doi: 10.1021/acs.est.6b05408. Epub 2017 Mar 3.

Siderophore and Organic Acid Promoted Dissolution and Transformation of Cr(III)-Fe(III)-(oxy)hydroxides.

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School of Earth and Atmospheric Sciences, Georgia Institute of Technology , Atlanta, Georgia 30332-0340, United States.
Department of Physics and Texas Center for Superconductivity (TCSUH), University of Houston , Houston, Texas 77204, United States.
Advanced Photon Source, Argonne National Laboratory , Argonne, Illinois 60439, United States.
Department of Ecosystem Science and Management, University of Wyoming , Laramie, Wyoming 82071, United States.
Department of Crop and Soil Science, North Carolina State University , Raleigh, North Carolina 27695, United States.


The role of microbial activities on the transformation of chromium (Cr) remediation products has generally been overlooked. This study investigated the stability of Cr(III)-Fe(III)-(oxy)hydroxides, common Cr(VI) remediation products, with a range of compositions in the presence of common microbial exudates, siderophores and small organic acids. In the presence of a representative siderophore, desferrioxamine B (DFOB), iron (Fe) was released at higher rates and to greater extents relative to Cr from all solid phases. The presence of oxalate alone caused the release of Cr, but not of Fe, from all solid phases. In the presence of both DFOB and oxalate, oxalate acted synergistically with DFOB to increase the Fe, but not the Cr, release rate. Upon reaction with DFOB or DFOB + oxalate, the remaining solids became enriched in Cr relative to Fe. Such incongruent dissolution led to solid phases with different compositions and increased solubility relative to the initial solid phases. Thus, the presence of microbial exudates can promote the release of Cr(III) from remediation products via both ligand complexation and increased solid solubility. Understanding the potential reaction kinetics and pathways of Cr(VI) remediation products in the presence of microbial activities is necessary to assess their long-term stability.

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