Dynamic interplay between uranyl phosphate precipitation, sorption, and phase evolution

Munasinghe, Prinith; Madden, M. E. Elwood; Brooks, Scott C.; Madden, Andrew S.

doi:10.1016/j.apgeochem.2015.04.008

Cited by 25 publications

(18 citation statements)

References 59 publications

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“…DU is used in kinetic energy penetrators and armor plating as well as having widespread applications as aircraft counterweights and radiation shielding in medical radiation therapy (Betti, 2003;Global Security, 2008). Leaching of U to water occurs naturally due to interaction with soil minerals (Choy et al, 2006;Munasinghe et al, 2015). Anthropogenic contamination also arises from U ore mining/processing, medical waste, nuclear power station operation, accidents, and weapons testing.…”

Section: Introductionmentioning

confidence: 99%

Removing uranium (VI) from aqueous solution with insoluble humic acid derived from leonardite

Meng

Yuan

Larson

et al. 2017

Journal of Environmental Radioactivity

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The occurrence of uranium (U) and depleted uranium (DU)-contaminated wastes from anthropogenic activities is an important environmental problem. Insoluble humic acid derived from leonardite (L-HA) was investigated as a potential adsorbent for immobilizing U in the environment. The effect of initial pH, contact time, U concentration, and temperature on U(VI) adsorption onto L-HA was assessed. The U(VI) adsorption was pH-dependent and achieved equilibrium in 2 h. It could be well described with pseudo-second-order model, indicating that U(VI) adsorption onto L-HA involved chemisorption. The U(VI) adsorption mass increased with increasing temperature with maximum adsorption capacities of 91, 112 and 120 mg g at 298, 308 and 318 K, respectively. The adsorption reaction was spontaneous and endothermic. We explored the processes of U(VI) desorption from the L-HA-U complex through batch desorption experiments in 1 mM NaNO and in artificial seawater. The desorption process could be well described by pseudo-first-order model and reached equilibrium in 3 h. L-HA possessed a high propensity to adsorb U(VI). Once adsorbed, the release of U(VI) from L-HA-U complex was minimal in both 1 mM NaNOand artificial seawater (0.06% and 0.40%, respectively). Being abundant, inexpensive, and safe, L-HA has good potential for use as a U adsorbent from aqueous solution or immobilizing U in soils.

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Section: Introductionmentioning

confidence: 99%

Removing uranium (VI) from aqueous solution with insoluble humic acid derived from leonardite

Meng

Yuan

Larson

et al. 2017

Journal of Environmental Radioactivity

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“…The reactivity of sediments at contaminated sites is dominated by the fine fraction mineralogy, which often contains a mixture of iron oxide and clay minerals (Qafoku et al, 2005;Catalano et al, 2006;Zachara et al, 2007;Komlos et al, 2007;Hyun et al, 2009;Singer et al, 2009;Stubbs et al, 2009;Campbell et al, 2011). Oxide minerals such as goethite have been shown to display enhanced adsorption of U(VI) in the presence of phosphate because of ternary complexation and may also act to nucleate U(VI) phosphate minerals (Payne et al, 1996;Cheng et al, 2004;Singh et al, 2010Singh et al, , 2012Munasinghe et al, 2015). U(VI)-phosphate ternary surface complexes have also been shown to form in the presence of alumina (Galindo et al, 2010).…”

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confidence: 99%

Effect of phosphate on U(VI) sorption to montmorillonite: Ternary complexation and precipitation barriers

Troyer

Maillot

Wang

et al. 2016

Geochimica et Cosmochimica Acta

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Phosphate addition is a potential treatment method to lower the solubility of U(VI) in soil and groundwater systems by causing U(VI) phosphate precipitation as well as enhancing adsorption. Previous work has shown that iron oxide surfaces may facilitate the nucleation of U(VI) phosphate minerals and, that under weakly acidic conditions, phosphate also enhances U(VI) adsorption to such phases. Like iron oxides, clays are important reactive phases in the subsurface but little is known about the interaction of U(VI) and phosphate with these minerals. The effect of aqueous phosphate on U(VI) binding to Wyoming montmorillonite (SWy-2) in airequilibrated systems was investigated. Equilibrium U(VI) uptake to montmorillonite was determined at pH 4, 6 and 8 at discrete initial phosphate concentrations between 0 and 100 M. The observed behavior of U(VI) indicates a transition from adsorption to precipitation with increasing total uranium and phosphate concentrations at all pH values. At the highest phosphate concentration examined at each pH value, a barrier to U(VI) phosphate nucleation is observed. At lower concentrations, phosphate has no effect on macroscopic U(VI) adsorption. To assess the mechanisms of U(VI)-phosphate interactions on smectite surfaces, U(VI) speciation was investigated under selected conditions using laser-induced fluorescence spectroscopy (LIFS) and extended X-ray absorption fine-structure (EXAFS) spectroscopy. Samples above the precipitation threshold display EXAFS and LIFS spectral signatures consistent with the autunite

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“…The formation of uranyl phosphates is also observed (Boekhout et al 2015). These phosphates are an efficient trap for uranium sequestration (Munasinghe et al 2015).…”

Section: Accepted Manuscriptmentioning

confidence: 94%

“…The evolution of oxidation in depth of the waste rock pile and the associated weathering processes were investigated in a preliminary study(Boekhout et al 2015), showing overall oxidation of the waste rock pile with dominantly uranyl phosphate precipitation. Secondary uranyl phosphates are important in the presently investigated surficial samples, as they are the dominant secondary U mineral found and are known to cause low levels of aqueous uranium in groundwaters due to their low solubility(Munasinghe et al 2015). The different micromorphology of autunites, from well-defined layered crystal in lamprophyres compared to isolated lamellae in granites, has been related to the duration of weathering.…”

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confidence: 99%

Impact of incipient weathering on uranium migration in granitic waste rock piles from former U mines (Limousin, France)

Kanzari

Gérard

Boekhout

et al. 2017

Journal of Geochemical Exploration

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International audienceThis study investigates the impact of incipient weathering on uranium (U) migration at the surface of granitic waste rock piles from former U mines in Limousin (France) operated half a century ago. We used a multi-scale mineralogical and geochemical approach to evaluate the impact of incipient weathering on uranium mobility in a chaotic waste rock pile. The surficial part of five former mines located in the “La Crouzille” and “La Creuse” mining districts was investigated. Four groups of samples were defined based on field observations and mineralogy, granites, lamprophyres, hydrothermally altered rocks and weathering products. Petrology, mineralogy and geochemistry investigations show the importance of mineralogical and geochemical transformations during incipient weathering over a few decades. The Chemical Index of Alteration (CIA) is successfully used to assess the weathering state of samples in the waste rock pile chaotic deposit. The mean CIA value is around 60 for unweathered/incipiently weathered granites whereas highly weathered samples have CIA around 70. This means that no significant major element loss occurs in the granitic rocks suffering incipient weathering. Various micron-size secondary U minerals consist in a large diversity of oxidized uranyl minerals (uranophane, uranyl sulfate, curite, autunite and other uranyl phosphates), with dominant uranyl phosphates, indicating local U mobility in the waste rock pile. Autunites micromorphology indicates different degrees of weathering of the samples in which it crystallizes. U is primarily concentrated in the clay fraction (< 2 μm), associated with secondary minerals from granite alteration (clay minerals such as smectite and vermiculite, Fe-oxides and phosphate minerals) and, to a limited extent, relict primary minerals. These weathering products contribute to U(VI) stabilization under oxidizing conditions

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Dynamic interplay between uranyl phosphate precipitation, sorption, and phase evolution

Cited by 25 publications

References 59 publications

Removing uranium (VI) from aqueous solution with insoluble humic acid derived from leonardite

Removing uranium (VI) from aqueous solution with insoluble humic acid derived from leonardite

Effect of phosphate on U(VI) sorption to montmorillonite: Ternary complexation and precipitation barriers

Impact of incipient weathering on uranium migration in granitic waste rock piles from former U mines (Limousin, France)

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