title: Optimizing Cr(VI) and Tc(VII) remediation through nanoscale biomineral engineering.
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 Fe(3)O(4). 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(2,3)-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(2,3)-edge XMCD spectra found Cr(III) replaced approximately 14%-20% of octahedral Fe in both biogenic magnetites, producing a layer resembling CrFe(2)O(4). 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 (approximately 20%) (99)mTc(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.
authors.affiliation: Williamson Research Centre for Molecular Environmental Science, and School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Manchester, U.K. richard.cutting@manchester.ac.uk
authors.forename: Richard S
authors.initials: RS
authors.lastname: Cutting
authors.forename: Victoria S
authors.initials: VS
authors.lastname: Coker
authors.forename: Neil D
authors.initials: ND
authors.lastname: Telling
authors.forename: Richard L
authors.initials: RL
authors.lastname: Kimber
authors.forename: Carolyn I
authors.initials: CI
authors.lastname: Pearce
authors.forename: Beverly L
authors.initials: BL
authors.lastname: Ellis
authors.forename: Richard S
authors.initials: RS
authors.lastname: Lawson
authors.forename: Gerrit
authors.initials: G
authors.lastname: van der Laan
authors.forename: Richard A D
authors.initials: RA
authors.lastname: Pattrick
authors.forename: David J
authors.initials: DJ
authors.lastname: Vaughan
authors.forename: Elke
authors.initials: E
authors.lastname: Arenholz
authors.forename: Jonathan R
authors.initials: JR
authors.lastname: Lloyd
mesh_terms: D001673:Biodegradation, Environmental; D002857:Chromium / Q000302:isolation & purification*; D002942:Circular Dichroism; D004583:Electrons; D052918:Environmental Restoration and Remediation / Q000379:methods*; D005290:Ferric Compounds / Q000737:chemistry; D052203:Ferrosoferric Oxide / Q000737:chemistry; D008903:Minerals / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D056951:Photoelectron Spectroscopy; D013499:Surface Properties; D013667:Technetium / Q000302:isolation & purification*
chemical_list: D005290:Ferric Compounds; D008903:Minerals; D002857:Chromium; D013667:Technetium; C092844:ferric oxyhydroxide; D010100:Oxygen; D052203:Ferrosoferric Oxide