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Redox interactions of Tc(VII), U(VI) and Np(V) with microbially reduced biotite and chlorite.

DOI: 10.1021/acs.est.5b03463 DOI Help
PMID: 26488884 PMID Help

Authors: Diana R. Brookshaw (University of Manchester) , Richard A. D. Pattrick (University of Manchester) , Pieter Bots (University of Manchester) , Gareth T. W. Law (University of Manchester) , Jonathan R. Lloyd (University of Manchester) , J. Frederick W. Mosselmans (Diamond Light Source) , David J. Vaughan (University of Manchester) , Kathy Dardenne (Institut fur Nukleare Entsorgung) , Katherine Morris (University of Manchester)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Environmental Science & Technology , VOL 49 (22)

State: Published (Approved)
Published: October 2015
Diamond Proposal Number(s): 7367 , 7593

Open Access Open Access

Abstract: Technetium, uranium and neptunium are contaminants that cause concern at nuclear facilities due to their long half8life, 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 towards soluble TcO4, UO2[2+] and NpO[2+]. When reacted with unaltered biotite and chlorite, significant sorption of U(VI) occurred in low carbonate (0.2 mM) buffer whilst U(VI), Tc(VII) and Np(V) showed l ow 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: 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 analy sis suggested that in the reaction products, Tc(IV) was associated with Fe, Np(IV) formed nano8particulate 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.

Subject Areas: Chemistry, Earth Science, Materials


Instruments: B18-Core EXAFS

Other Facilities: ANKA