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Plutonium(IV) sorption during ferrihydrite nanoparticle formation

DOI: 10.1021/acsearthspacechem.9b00105 DOI Help

Authors: Kurt F. Smith (The University of Manchester) , Katherine Morris (The University of Manchester) , Gareth Law (The University of Manchester) , Ellen H. Winstanley (The University of Manchester) , Francis R. Livens (The University of Manchester) , Joshua S. Weatherill (The University of Manchester) , Liam G. Abrahamsen-mills (National Nuclear Laboratory) , Nicholas D. Bryan (National Nuclear Laboratory) , J. Frederick W. Mosselmans (Diamond Light Source) , Giannantonio Cibin (Diamond Light Source) , Stephen Parry (Diamond Light Source) , Richard Blackham (Sellafield Ltd.) , Kathleen A. Law (The University of Manchester) , Samuel Shaw (The University of Manchester)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Acs Earth And Space Chemistry

State: Published (Approved)
Published: September 2019
Diamond Proposal Number(s): 17243

Abstract: Understanding interactions between iron (oxyhydr)oxide nanoparticles and plutonium is essential to underpin technology to treat radioactive effluents, in clean-up of land contaminated with radionuclides, and to ensure the safe disposal of radioactive wastes. These interactions include a range of adsorption, precipitation and incorporation processes. Here, we explore the mechanisms of plutonium sequestration during ferrihydrite precipitation from an acidic solution. The initial 1 M HNO3 solution with Fe(III)(aq) and 242Pu(IV)(aq) underwent controlled hydrolysis via the addition of NaOH to pH 9. The majority of Fe(III)(aq) and Pu(IV)(aq) was removed from solution between pH 2 and 3 during ferrihydrite formation. Analysis of Pu-ferrihydrite by Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy showed that Pu(IV) formed an inner sphere tetradentate complex on the ferrihydrite surface, with minor amounts of PuO2 present. Best fits to the EXAFS data collected from Pu-ferrihydrite samples aged for two- and six- months showed no statistically significant change in the Pu(IV)-Fe oxyhydroxide surface complex despite the ferrihydrite undergoing extensive recrystallisation to hematite. This suggests the Pu remains strongly sorbed to the iron (oxyhydr)oxide surface and could be retained over extended time periods.

Journal Keywords: Plutonium; ferrihydrite; hematite; nanoparticle; XAS; sorption

Subject Areas: Chemistry, Environment


Instruments: B18-Core EXAFS