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Optimizing Cr(VI) and Tc(VII) Remediation through Nanoscale Biomineral Engineering

DOI: 10.1021/es902119u DOI Help

Authors: Richard Cutting (University of Manchester) , Vicky Coker (University of Manchester) , Neil Telling (University of Manchester) , Richard L. Kimber (University of Manchester) , Carolyn Pearce (University of Manchester) , Beverly L. Ellis (Manchester Royal Infirmary) , Richard S. Lawson (Manchester Royal Infirmary) , Gerrit Van Der Laan (Diamond Light Source) , Richard A. D. Pattrick (University of Manchester) , David J. Vaughan (University of Manchester) , Elke Arenholz (Lawrence Berkeley National Laboratory) , Jon Lloyd (University of Manchester)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Environmental Science & Technology , VOL 44 (7) , PAGES 2577-2584

State: Published (Approved)
Published: January 2010

Abstract: The influence of Fe(III) starting material on the ability of magnetically recoverable biogenic magnetites produced by Geobacter sulfurreducens to retain metal oxyanion contaminants has been investigated. The reduction/removal of aqueous Cr(VI) was used to probe the reactivity of the biomagnetites. Nanomagnetites produced by the bacterial reduction of schwertmannite powder were more efficient at reducing Cr(VI) than either ferrihydrite "gel"-derived biomagnetite or commercial nanoscale Fe3O4. Examination of post-exposure magnetite surfaces indicated both Cr(III) and Cr(VI) were present. X-ray magnetic circular dichroism (XMCD) studies at the Fe L-2,L-3-edge showed that the amount of Fe(III) "gained" by Cr(VI) reduction could not be entirely accounted for by "lost" Fe(II). Cr L-2,L-3-edge XMCD spectra found Cr(III) replaced similar to 14%-20% of octahedral Fe in both biogenic magnetites, producing a layer resembling CrFe2O4. However, schwertmannite-derived biomagnetite was associated with approximately twice as much Cr as ferrihydrite-derived magnetite. Column studies using a gamma-camera to image a (99)mTc(VII) radiotracer were performed to visualize the relative performances of biogenic magnetites at removing aqueous metal oxyanion contaminants. Again, schwertmannite-derived biomagnetite proved capable of retaining more (similar to 20%) Tc-99m(VII) than ferrihydrite-derived biomagnetite, confirming that the production of biomagnetite can be fine-tuned for efficient environmental remediation through careful selection of the Fe(III) mineral substrate supplied to Fe(III)reducing bacteria.

Subject Areas: Environment

Technical Areas: