Uranyl and arsenate cosorption on aluminum oxide surface

Tang, Yuanzhi; Reeder, Richard J.

doi:10.1016/j.gca.2009.02.003

Cited by 72 publications

(42 citation statements)

References 51 publications

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“…Recently, U and As have also been found to form uranyl arsenate surface complexes with aluminium oxide under a range of pHs and uranyl arsenate aqueous complexes and precipitates under acidic conditions in the laboratory. [36,37] Little is known about the formation of uranyl arsenates in the environment, but their effect on mobility of U and As should be considered in environments where both elements are present.…”

Section: Introductionmentioning

confidence: 99%

“…[4] Aqueous surface water and pore water Fe, U and As measurements in Larson et al complement sediment concentrations determined in our study. [4] Although As can occur in U ore at concentrations up to 10 wt-%, [37] the fate and transport of both U and As at U mine tailings has not been previously investigated at any other field sites. However, U geochemistry has been studied extensively in Rifle, Colorado and other mill tailing sites.…”

Section: Introductionmentioning

confidence: 99%

“…[31] Donahue and Hendry studied As transport at a U mill tailing in Canada and found that As is primarily present as calcium arsenates, which could dissolve into site pore water resulting in concentrations of up to 126 ppm As. [37,42] Arsenic was also found to be adsorbed to ferrihydrite resulting in long-term stability under site conditions, preventing aqueous As transport. [37,43,44] The majority of these studies have focussed on the geochemistry and stability of U or As in tailing piles rather than physical and chemical controls on down-gradient transport of both elements in the same study.…”

Section: Introductionmentioning

confidence: 99%

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Effect of biogeochemical redox processes on the fate and transport of As and U at an abandoned uranium mine site: an X-ray absorption spectroscopy study

Troyer

Stone

2014

Environ. Chem.

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Environmental context. Uranium and arsenic, two elements of human health concern, are commonly found at sites of uranium mining, but little is known about processes influencing their environmental behaviour. Here we focus on understanding the chemical and physical processes controlling uranium and arsenic transport at an abandoned uranium mine. We find that the use of sedimentation ponds limits the mobility of uranium; however, pond conditions at our site resulted in arsenic mobilisation. Our findings will help optimise restoration strategies for mine tailings.Abstract. Although As can occur in U ore at concentrations up to 10 wt-%, the fate and transport of both U and As at U mine tailings have not been previously investigated at a watershed scale. The major objective of this study was to determine primary chemical and physical processes contributing to transport of both U and As to a down gradient watershed at an abandoned U mine site in South Dakota. Uranium is primarily transported by erosion at the site, based on decreasing concentrations in sediment with distance from the tailings. Sequential extractions and U X-ray absorption near-edge fine structure (XANES) fitting indicate that U is immobilised in a near-source sedimentation pond both by prevention of sediment transport and by reduction of U VI to U IV . In contrast to U, subsequent release of As to the watershed takes place from the pond partially due to reductive dissolution of Fe oxy(hydr)oxides. However, As is immobilised by adsorption to clays and Fe oxy(hydr)oxides in oxic zones and by formation of As-sulfide mineral phases in anoxic zones down gradient, indicated by sequential extractions and As XANES fitting. This study indicates that As should be considered during restoration of uranium mine sites in order to prevent transport.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effect of biogeochemical redox processes on the fate and transport of As and U at an abandoned uranium mine site: an X-ray absorption spectroscopy study

Troyer

Stone

2014

Environ. Chem.

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“…Building on earlier work on clean single-crystal mineral surfaces studied under ultra-high vacuum conditions [3][4][5][6], experimental studies of hydrated surfaces have emerged to address questions, such as how exposed surfaces transform under geochemical conditions [7][8][9][10]. Experimental studies of Al and Fe (hydr)oxide surfaces are prolific [11][12][13][14][15][16][17], as these materials have a natural abundance and reactivity towards aqueous contaminants. As an example, numerous studies conducted by Catalano and co-workers can be mentioned [18][19][20][21].…”

Section: Introductionmentioning

confidence: 99%

“…There is a consensus in literature as to how arsenate binds to aluminum or iron surfaces, based on EXAFS data [11][12][13][14]. When arsenate binds to α-alumina, γ-alumina, and gibbsite, these studies reveal that arsenate preferentially binds to the aluminum surface in a bidentate, binuclear manner (which can also be called corner-sharing).…”

Section: Introductionmentioning

confidence: 99%

Density Functional Theory Study of Arsenate Adsorption onto Alumina Surfaces

2018

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Atomistic modeling of mineral-water interfaces offers a way of confirming (or refuting) experimental information about structure and reactivity. Molecular-level understanding, such as orbital-based descriptions of bonding, can be developed from charge density and electronic structure analysis. First-principles calculations can be used to identify weaknesses in empirical models. This provides direction on how to propose more robust representations of systems of increasing size that accurately represent the underlying physical factors governing reactivity. In this study, inner-sphere complex geometries of arsenate on hydrated alumina surfaces are modeled at the density functional theory (DFT)-continuum solvent level. According to experimental studies, arsenate binds to alumina surfaces in a bidentate binuclear (BB) fashion. While the DFT calculations support the preference of the BB configuration, the optimized geometries show distortion from the ideal tetrahedral geometry of the arsenic atom. This finding suggests that steric factors, and not just coordination arguments, influences reactivity. The O surf -As-O surf angle for the more favorable arsenate configurations is closest to the ideal tetrahedral angle of 109.5 • . Comparing the results of arsenate adsorption using a small cluster model with a periodic slab model, we report that the two model geometries yield results that differ qualitatively and quantitatively. This relates the steric factors and rigidity of the surface models.

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