Redox Interactions of Tc(VII), U(VI), and Np(V) with Microbially Reduced Biotite and Chlorite.
Technetium, uranium, and neptunium are contaminants that cause concern at nuclear facilities due to their long half-life, environmental mobility, and radiotoxicity. Here we investigate the impact of microbial reduction of Fe(III) in biotite and chlorite and the role that this has in enhancing mineral reactivity toward soluble TcO4(-), UO2(2+), and NpO2(+). When reacted with unaltered biotite and chlorite, significant sorption of U(VI) occurred in low carbonate (0.2 mM) buffer, while U(VI), Tc(VII), and Np(V) showed low reactivity in high carbonate (30 mM) buffer. On reaction with the microbially reduced minerals, all radionuclides were removed from solution with U(VI) reactivity influenced by carbonate. Analysis by X-ray absorption spectroscopy (XAS) confirmed reductive precipitation to poorly soluble U(IV) in low carbonate conditions and both Tc(VII) and Np(V) in high carbonate buffer were also fully reduced to poorly soluble Tc(IV) and Np(IV) phases. U(VI) reduction was inhibited under high carbonate conditions. Furthermore, EXAFS analysis suggested that in the reaction products, Tc(IV) was associated with Fe, Np(IV) formed nanoparticulate NpO2, and U(IV) formed nanoparticulate UO2 in chlorite and was associated with silica in biotite. Overall, microbial reduction of the Fe(III) associated with biotite and chlorite primed the minerals for reductive scavenging of radionuclides: this has clear implications for the fate of radionuclides in the environment.
Research Centre for Radwaste Disposal and Williamson Research Centre for Molecular Environmental Science, School of Earth, Atmospheric and Environmental Sciences, The University of Manchester , Oxford Road, Manchester M13 9PL, United Kingdom.
Diana R
DR
Brookshaw
Research Centre for Radwaste Disposal and Williamson Research Centre for Molecular Environmental Science, School of Earth, Atmospheric and Environmental Sciences, The University of Manchester , Oxford Road, Manchester M13 9PL, United Kingdom.
Richard A D
RA
Pattrick
Research Centre for Radwaste Disposal and Williamson Research Centre for Molecular Environmental Science, School of Earth, Atmospheric and Environmental Sciences, The University of Manchester , Oxford Road, Manchester M13 9PL, United Kingdom.
Pieter
P
Bots
Centre for Radiochemistry Research, School of Chemistry, The University of Manchester , Manchester M13 9PL, United Kingdom.
Gareth T W
GT
Law
Research Centre for Radwaste Disposal and Williamson Research Centre for Molecular Environmental Science, School of Earth, Atmospheric and Environmental Sciences, The University of Manchester , Oxford Road, Manchester M13 9PL, United Kingdom.
Jonathan R
JR
Lloyd
Diamond Light Source Ltd., Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, United Kingdom.
J Fredrick W
JF
Mosselmans
Research Centre for Radwaste Disposal and Williamson Research Centre for Molecular Environmental Science, School of Earth, Atmospheric and Environmental Sciences, The University of Manchester , Oxford Road, Manchester M13 9PL, United Kingdom.
David J
DJ
Vaughan
Karlsruhe Institute of Technology, Institut fur Nukleare Entsorgung , D-76021 Karlsruhe, Baden-Württemberg, Germany.
Kathy
K
Dardenne
Research Centre for Radwaste Disposal and Williamson Research Centre for Molecular Environmental Science, School of Earth, Atmospheric and Environmental Sciences, The University of Manchester , Oxford Road, Manchester M13 9PL, United Kingdom.
Katherine
K
Morris
D000538:Aluminum Silicates / Q000378:metabolism*; D001419:Bacteria / Q000378:metabolism*; D002712:Chlorides / Q000378:metabolism*; D005296:Ferrous Compounds / Q000378:metabolism*; D008903:Minerals / Q000737:chemistry; D009405:Neptunium / Q000737:chemistry* / Q000302:isolation & purification; D010084:Oxidation-Reduction; D012996:Solutions; D013667:Technetium / Q000737:chemistry* / Q000302:isolation & purification; D014501:Uranium / Q000737:chemistry* / Q000302:isolation & purification; D056928:X-Ray Absorption Spectroscopy
D000538:Aluminum Silicates; D002712:Chlorides; D005296:Ferrous Compounds; D008903:Minerals; D012996:Solutions; C047410:biotite; D014501:Uranium; D009405:Neptunium; D013667:Technetium; C001599:chlorite