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Brookshaw DR, Pattrick RAD, Bots P, Law GTW, Lloyd JR, Mosselmans JFW, Vaughan DJ, Dardenne K, Morris K. Redox Interactions of Tc(VII), U(VI), and Np(V) with Microbially Reduced Biotite and Chlorite. Environ Sci Technol 2015; 49:13139-13148. [PMID: 26488884 DOI: 10.1021/acs.est.5b03463] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
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.
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Affiliation(s)
- Diana R 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 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 Bots
- 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
| | - Gareth T W Law
- Centre for Radiochemistry Research, School of Chemistry, The University of Manchester , Manchester M13 9PL, United Kingdom
| | - Jonathan R Lloyd
- 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
| | - J Fredrick W Mosselmans
- Diamond Light Source Ltd., Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, United Kingdom
| | - David J Vaughan
- 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
| | - Kathy Dardenne
- Karlsruhe Institute of Technology, Institut fur Nukleare Entsorgung , D-76021 Karlsruhe, Baden-Württemberg, Germany
| | - Katherine Morris
- 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
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Brookshaw DR, Coker VS, Lloyd JR, Vaughan DJ, Pattrick RAD. Redox interactions between Cr(VI) and Fe(II) in bioreduced biotite and chlorite. Environ Sci Technol 2014; 48:11337-11342. [PMID: 25196156 DOI: 10.1021/es5031849] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Contamination of the environment with Cr as chromate (Cr(VI)) from industrial activities is of significant concern as Cr(VI) is a known carcinogen, and is mobile in the subsurface. The capacity of Fe(II)-containing phyllosilicates including biotite and chlorite to alter the speciation, and thus the mobility, of redox-sensitive contaminants including Cr(VI) is of great interest since these minerals are common in soils and sediments. Here, the capacity of bacteria, ubiquitous in the surface and near-surface environment, to reduce Fe(III) in phyllosilicate minerals and, thus, alter their redox reactivity was investigated in two-step anaerobic batch experiments. The model Fe(III)-reducing bacterium Geobacter sulfurreducens was used to reduce Fe(III) in the minerals, leading to a significant transformation of structural Fe(III) to Fe(II) of 0.16 mmol/g (∼ 40%) in biotite and 0.15 mmol/g (∼ 20%) in chlorite. The unaltered minerals could not remove Cr(VI) from solution despite containing a larger excess of Fe(II) than would be required to reduce all the added Cr(VI), unless they were supplied in a very high concentration (a 1:10 solid to solution ratio). By contrast, even at very low concentrations, the addition of bioreduced biotite and chlorite caused removal of Cr(VI) from solution, and surface and near surface X-ray absorption spectroscopy confirmed that this immobilization was through reductive transformation to Cr(III). We provide empirical evidence that the amount of Fe(II) generated by microbial Fe(III) reduction is sufficient to reduce the Cr(VI) removed and, in the absence of reduction by the unaltered minerals, suggest that only the microbially reduced fraction of the iron in the minerals is redox-active against the Cr(VI).
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Affiliation(s)
- Diana R Brookshaw
- Williamson Research Centre for Molecular Environmental Science, and School of Earth, Atmospheric and Environmental Sciences, University of Manchester , Manchester M13 9PL, United Kingdom
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