U(VI) sorption during ferrihydrite formation: Underpinning radioactive effluent treatment

Winstanley, Ellen H.; Morris, Katherine; Abrahamsen-Mills, Liam; Blackham, Richard; Shaw, Samuel

doi:10.1016/j.jhazmat.2018.11.077

Cited by 28 publications

(32 citation statements)

References 45 publications

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“…22,[43][44][45][46] These traits of ferrihydrite have been utilized to decontaminate radioactive effluent 47 and in various nuclear abatement technologies. 48 When Pu is present in solutions where iron (oxy)hydroxide minerals may be forming, such as in a contaminated ponds, lakes, or streams, or during corrosion of steel, its fate is unknown. The Pu could conceivably adsorb to the newly formed iron oxides (e.g.…”

Section: Introductionmentioning

confidence: 99%

Transformation of Ferrihydrite to Goethite and the Fate of Plutonium

Balboni

Smith

Moreau

et al. 2020

ACS Earth Space Chem.

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Understanding interactions between plutonium and iron (oxy)hydroxide minerals is necessary to gain a predictive understanding of plutonium environmental mobility and ensuring long-term performance of nuclear waste repositories. Plutonium sorption and desorption reactions with mineral surfaces, formation of PuO2 nanoparticles, and coprecipitation processes are all likely important processes under a range of geochemical conditions. We investigated plutonium fate during the formation of ferrihydrite and its subsequent recrystallization to goethite. Ferrihydrite was synthesized with varying quantities of Pu(IV) following either a sorption or coprecipitation process; the ferrihydrite was then aged hydrothermally to yield goethite. The synthesized materials were characterized via extended x-ray absorption fine structure spectroscopy, transmission electron microscopy, and acid leaching to elucidate the nature of plutonium association with ferrihydrite and goethite. In samples prepared following the sorption method, plutonium was identified in two different forms: a PuO2 precipitate and a surface sorbed plutonium complex. For the samples prepared via coprecipitation the data demonstrate that no PuO2 formation occurs in the ferrihydrite precursor and in the goethite experiments where plutonium concentration is ≤ 1000 ppm (mg Kg -1 ). In these coprecipitation experiments plutonium extended x-ray absorption fine structure data indicate the plutonium is strongly bound to the minerals either via formation of a strong inner sphere complex, or via an incorporation process. In the coprecipitation experiments, PuO2 formation only occurs at the highest plutonium concentration (3000 ppm), suggesting that during ferrihydrite recrystallization part of the plutonium can be remobilized to form PuO2 nanoparticles if the plutonium concentration is sufficiently elevated. In a series of acid leaching 11/16/21 3 experiments, less plutonium was removed from the goethite surface when formed via the coprecipitation process compared to the sorption process. Collectively, our results demonstrate that the nature of plutonium associated with the precursor ferrihydrite (adsorbed versus coprecipitated) will have a direct impact on the association of plutonium with its recrystallization product (goethite). Furthermore, the data illustrate that some properties of plutonium association with the precursor ferrihydrite are retained through recrystallization process to goethite. These findings show that plutonium strongly associates to iron (oxy)hydroxides formed through coprecipitation processes and in these materials plutonium can be strongly retained by the iron minerals.

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Section: Introductionmentioning

confidence: 99%

Transformation of Ferrihydrite to Goethite and the Fate of Plutonium

Balboni

Smith

Moreau

et al. 2020

ACS Earth Space Chem.

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“…Similar distances were also measured for abiotic ferrihydrite by Ulrich et al (2006). Recent EXAFS studies of uranium sorption on ferrihydrite by Winstanley et al (2018) can also be used for comparison, noting however that the studies were performed under alkaline conditions and using uranium concentrations up to 1.05 mM, where precipitation of a discrete U(VI) phase was detected. However, the sorption mechanism was also described as uranium sorption to ferrihydrite via a bidentate edge-sharing inner-sphere species with carbonate forming a ternary surface complex.…”

Section: Comparison Of Abiotic Iron Oxides and Oxyhydroxides With Bios Samplesmentioning

confidence: 99%

“…The O ax bond lengths are shorter than those observed for Np(V) adsorbed to hematite (Müller et al 2015;Amayri et al 2007) and goethite (Combes et al 1992). According to Bots et al (2016) [3] Winstanley et al (2018) [4] Dodge et al (2002) [5] This study Radial distance error ± 0.01 Å [2] Müller et al (2015) [3] Amayri et al (2007) [4] Combes et al (1992) [5] Bots et al (2016) [6] This study could be caused by positively charged neptunyl, forming stronger and consequently shorter bonds with negatively charged hydroxide than with the oxygen of water molecules. EXAFS studies on neptunium(V)-ferrihydrite were exclusively carried out under alkaline conditions (pH 9.5 and 11) by Bots et al (2016).…”

Section: Comparison Of Abiotic Iron Oxides and Oxyhydroxides With Bios Samplesmentioning

confidence: 99%

Uranium and neptunium retention mechanisms in Gallionella ferruginea/ferrihydrite systems for remediation purposes

Krawczyk-Bärsch

Scheinost

Roßberg

et al. 2020

Environ Sci Pollut Res

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The ubiquitous β-Proteobacterium Gallionella ferruginea is known as stalk-forming, microaerophilic iron(II) oxidizer, which rapidly produces iron oxyhydroxide precipitates. Uranium and neptunium sorption on the resulting intermixes of G. ferruginea cells, stalks, extracellular exudates, and precipitated iron oxyhydroxides (BIOS) was compared to sorption to abiotically formed iron oxides and oxyhydroxides. The results show a high sorption capacity of BIOS towards radionuclides at circumneutral pH values with an apparent bulk distribution coefficient (Kd) of 1.23 × 104 L kg−1 for uranium and 3.07 × 105 L kg−1 for neptunium. The spectroscopic approach by X-ray absorption spectroscopy (XAS) and ATR FT-IR spectroscopy, which was applied on BIOS samples, showed the formation of inner-sphere complexes. The structural data obtained at the uranium LIII-edge and the neptunium LIII-edge indicate the formation of bidentate edge-sharing surface complexes, which are known as the main sorption species on abiotic ferrihydrite. Since the rate of iron precipitation in G. ferruginea-dominated systems is 60 times faster than in abiotic systems, more ferrihydrite will be available for immobilization processes of heavy metals and radionuclides in contaminated environments and even in the far-field of high-level nuclear waste repositories.

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“…Minerals 2022, 12, 165 2 of 12 237 Np is produced from 238 U in nuclear reactors by neutron capture [7] and the α-decay of 241 Am (t1 /2 = 432.5 years) [1] in radioactive wastes, meaning the concentration of 237 Np will increase in radioactive wastes over time. Additionally, 237 Np is often considered a priority radionuclide for removal from radioactive effluents by treatment facilities, for example, the Enhanced Actinide Removal Plant (EARP, Sellafield, UK) [8][9][10], with research into its behaviour offering insight into AnO 2 + (e.g., PuO 2 + ) behaviour more generally. Consequently, there is a need to obtain a mechanistic understanding of the solid-aqueous partitioning of Np in both natural and engineered environments.…”

Section: Introductionmentioning

confidence: 99%

“…In addition to environmental interactions with iron minerals, effluent treatment facilities also utilise the sorption capacity of iron (oxyhydr)oxides to partition contaminants to the solid phase. One key example is the use of ferrihydrite to remove actinides from effluents at EARP [8,10]. Here, the pH of an acidic effluent is increased through addition of NaOH, resulting in the formation of ferrihydrite via Keggin clusters (Fe 13 ) [35].…”

Section: Introductionmentioning

confidence: 99%

Neptunium and Uranium Interactions with Environmentally and Industrially Relevant Iron Minerals

et al. 2022

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Neptunium (237Np) is an important radionuclide in the nuclear fuel cycle in areas such as effluent treatment and the geodisposal of radioactive waste. Due to neptunium’s redox sensitivity and its tendency to adsorb strongly to mineral phases, such as iron oxides/sulfides, the environmental mobility of Np can be altered significantly by a wide variety of chemical processes. Here, Np interactions with key iron minerals, ferrihydrite (Fe5O8H·4H2O), goethite (α-FeOOH), and mackinawite (FeS), are investigated using X-ray Absorption Spectroscopy (XAS) in order to explore the mobility of neptunyl(V) (Np(V)O2+) moiety in environmental (radioactive waste disposal) and industrial (effluent treatment plant) scenarios. Analysis of the Np LIII-edge X-ray Absorption Near-Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) showed that upon exposure to goethite and ferrihydrite, Np(V) adsorbed to the surface, likely as an inner-sphere complex. Interestingly, analysis showed that only the first two shells (Oax and Oeq) of the EXAFS could be modelled with a high degree of confidence, and there was no clear indication of Fe or carbonate in the fits. When Np(V)O2+ was added to a mackinawite-containing system, Np(V) was reduced to Np(IV) and formed a nanocrystalline Np(IV)O2 solid. An analogous experiment was also performed with U(VI)O22+, and a similar reduction was observed, with U(VI) being reduced to nanocrystalline uraninite (U(IV)O2). These results highlight that Np(V) may undergo a variety of speciation changes in environmental and engineered systems whilst also highlighting the need for multi-technique approaches to speciation determination for actinyl (for example, Np(V)O2+) species.

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U(VI) sorption during ferrihydrite formation: Underpinning radioactive effluent treatment

Cited by 28 publications

References 45 publications

Transformation of Ferrihydrite to Goethite and the Fate of Plutonium

Transformation of Ferrihydrite to Goethite and the Fate of Plutonium

Uranium and neptunium retention mechanisms in Gallionella ferruginea/ferrihydrite systems for remediation purposes

Neptunium and Uranium Interactions with Environmentally and Industrially Relevant Iron Minerals

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