Article Cite This: Environ. Sci. Technol. XXXX, XXX, XXX−XXX
pubs.acs.org/est
Kinetics of Uranyl Peroxide Nanocluster (U60) Sorption to Goethite Luke R. Sadergaski and Amy E. Hixon* Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, Indiana 46556, United States
Environ. Sci. Technol. Downloaded from pubs.acs.org by UNIV OF SOUTH DAKOTA on 08/16/18. For personal use only.
S Supporting Information *
ABSTRACT: The unique properties of uranium-based nanomaterials may significantly impact our current understanding of the fate and transport of U(VI) in environmental systems. Sorption of the uranyl peroxide nanocluster [(UO2)(O2)(OH)]6060‑ (U60) to goethite (α-FeOOH) was studied using batch sorption experiments as a function of U60 concentration (0.5−2 g·L−1), mineral concentration (100−500 m2·L−1), and pH (8−10). The resulting rate law describing U60 interactions with goethite at pH 9 was R = −krxn[U60]0.29±0.02[goethite]1.2±0.1 where krxn = (6.7 ± 2.0) × 10−4 (g·L−1)0.71±0.02(m2· L−1)−1.2±0.1(day−1). The largest fraction of U60 removed from solution was at pH 8, which is below the isoelectric point of the goethite used in this study. Site density calculations suggest that U60 may exist on the goethite surface at a center-to-center distance of 5.4−6.5 nm, depending upon pH, which mirrors the center-to-center distance observed in the aqueous phase near the U60 solubility limit. At pH 10, approximately 20% uranium was desorbed within 3 days. Analysis of the reacted mineral surface using X-ray photoelectron spectroscopy confirmed the presence of a single U(VI) species on the mineral surface, and electrospray ionization mass spectrometry revealed that U60 remains intact during the sorption and desorption processes. These results demonstrate that the behavior of U60 at the goethite-water interface is similar to that of discrete U(VI) but is governed by different sorption mechanisms and reaction kinetics, which has the potential to alter our current understanding of the fate and transport of uranium species in the environment.
■
INTRODUCTION Understanding the sorption behavior of radioactive contaminants is essential for evaluating the effectiveness of remediation strategies at contaminated sites and predicting the safety of future nuclear waste repositories.1 While studies investigating the thermodynamic equilibrium of sorption reactions are prevalent in the literature and captured in data repositories such as the RES3T database,2 kinetic studies have received much less attention.3−6 The latter are important in evaluating when equilibrium has been achieved, can highlight important intermediate species, and inform conceptual models describing reactions that occur at the mineral-water interface. One objective of this study is to derive the rate law describing sorption of U60, a uranium(VI) polyoxometalate, to goethite (α-FeOOH). Uranium is a relatively common radioactive species that has been thoroughly studied due to its radiotoxicity and prevalence at contaminated sites.7 Uranyl peroxide species may form under environmentally relevant conditions when alpha radiolysis of water produces sufficient quantities of hydrogen peroxide. This can occur in natural uranium deposits where enough hydrogen peroxide is produced for the formation of the minerals studtite and metastudtite.8 Such conditions are also expected where damaged irradiated nuclear fuel interacts with water, within future nuclear waste repositories, and at contaminated sites such as the Hanford Site, FukushimaDaiichi, and the Savannah River Site.9,10 While uranyl peroxide clusters have not been directly observed in natural systems, a © XXXX American Chemical Society
recent transmission electron microscopy (TEM) study focused on characterizing nuclear waste stored in underground tanks at the Hanford Site in Richland, Washington (USA).11 The authors identified uranium particles with trace amounts of strontium that have diameters on the order of the tens of nanometers.11 These uranium-bearing particles look similar to blackberries made of U60 which were characterized previously by cryogenic TEM.12 The uranium peroxide nanocluster [(UO2)(O2)(OH)]6060‑ (U60) was chosen for this study because it well characterized and easy to synthesize in gram quantities. It is used as a model structure for the wider family of uranyl peroxide nanoclusters, which spontaneously self-assemble in solution under alkaline conditions and are thermodynamically stable in the absence of excess peroxide.10,13,14 U60 is comprised of 60 compositionally identical uranyl peroxide hydroxide polyhedra which are connected by shared peroxide linkages and has the same topology as the Buckminsterfullerene C60.15,16 These nanoclusters persist in aqueous solution from pH 7.5 to 11,13 and the negative charge of the uranyl peroxide cage is balanced by K+ and Li+ counter-cations both in solution and when crystallized. In solution, Li+ cations are not closely associated with the uranyl peroxide cage at the concentrations of U60 used Received: Revised: Accepted: Published: A
May 21, 2018 July 29, 2018 July 31, 2018 July 31, 2018 DOI: 10.1021/acs.est.8b02716 Environ. Sci. Technol. XXXX, XXX, XXX−XXX
Article
Environmental Science & Technology
with goethite.28 Powder patterns and Raman spectra are provided in the Supporting Information. Raman spectra were collected using a Bruker Sentinel system with fiber optics and a video-assisted Raman probe equipped with a 785 nm laser source and a high-sensitivity, TE-cooled, 1024 × 255 CCD array. Spectra were collected using a 200 mW light source and three, 30-s scans over the range 80−3200 cm−1. The specific surface area of goethite was determined by N2 adsorption−desorption at 77 K with a Micromeritics ASAP 2020 accelerated surface area and porosimetry system. Samples (∼1.0 g) were degassed at 100 °C for 24 h before Brunauer− Emmett−Teller (BET) surface area analysis. The specific surface area of goethite used in this study was determined to be 30.2 m2·g−1, which is typical of goethite.27 Phase analysis light scattering was used to determine the isoelectric point by measuring the zeta potential of goethite powder samples (0.25 g·L−1 goethite) using a Brookhaven NanoBrook Omni instrument (see the Supporting Information). Triplicate zeta potential measurements were modeled using Smoluchowsky calculations to determine an isoelectric point (IEP) of 9.06 ± 0.04. This value is within a common range for reported goethite minerals.29−31 ICP-OES Analysis. Inductively coupled plasma optical emission spectroscopy (ICP-OES) was used to quantify the elemental concentrations in reactor solutions. Elemental analyses were determined using a PerkinElmer Optima 8000 DV ICP-OES instrument with 165−800 nm coverage and a resolution of approximately 0.01 nm for multielemental analysis. External calibration was used to determine the unknown elemental concentrations of U (0.2 to 20 ppm), K (0.07 to 2 ppm), Li (0.025 to 1 ppm), and Fe (0.05 to 5 ppm). Aliquots from each reactor were dissolved in 10 mL of 5% nitric acid. Each dilution was measured gravimetrically, using an OHAUS model AX124/E balance with an accuracy of ±0.0001 g. An internal standard (1 ppm Y) was added to each standard, blank, and sample to monitor for instrument drift. X-ray Photoelectron Spectroscopy. X-ray photoelectron spectroscopy (XPS) was used to examine the valence states of uranium and iron by measuring their respective photoelectron spectra using a PHI VersaProbe II X-ray photoelectron spectrometer. Spectra were collected at high resolution with monochromatic Al−K radiation using a pass energy of 93.9 eV and a 100-μm spot size. Reacted U60-goethite samples were rinsed twice with Milli-Q water before XPS analysis and placed on carbon tape. Spectra were collected for U 4f, Fe 2p, and C 1s peaks, and the measured binding energies were referenced by fixing the position of adventitious C 1s to 285.0 eV. Surface charge neutralization was performed automatically. Shirley background and asymmetric peak shape profile parameters were used to model the uranium fitted bands.32 Satellite peak positions were used to determine oxidation state of U and Fe by comparison with published data.33,34 Batch Sorption Experiments. Batch sorption experiments were performed in duplicate by spiking the appropriate amount of the U60 stock solution into suspensions containing 100 m2·L−1−500 m2·L−1 goethite (see the Supporting Information). The U60 concentration (0.5−2 g·L−1 U60; 290−1160 ppm U) used here is consistent with or lower than other studies probing the properties of uranyl peroxide nanoclusters17,18,24,25,35 and is necessary to meet instrument detection limits. Because uranyl peroxide nanoclusters have not been observed in the environment, acceptable concentration ranges are not known. However, the high solubility of U60 and
in this study, which leaves the cage with an overall negative charge.17,18 Goethite is one of the most common iron (hydr)oxide minerals in the environment and is considered to be one of the most important sorbents for uranium.19,20 While the behavior of (UO2)2+ at the goethite surface is fairly well established,19−23 only one study has considered the sorption of uranium polyoxometalate nanoclusters to natural minerals.24 Interactions of uranium nanoclusters at the mineral-water interface may strongly impact the fate and transport of uranium in the environment since they are considerably different than discrete (UO2)2+.24,25 For this reason, there is a strong need for more experimental data that can be used in both predictive and performance assessment models. This study examines the sorption of U60 to goethite as a function pH (8−10), time ( PZC whereas the (001) and (010) faces will carry a positive proton charge since pH < PZC). However, if our hypothesis of U60-goethite interactions by cation-bridge formation is correct (see below), U60 could potentially interact with the (100) face of goethite as well. We expect that U60 associated with the goethite surface would pack no closer than that observed in the crystal structure (i.e., 2.7 nm center-to-center24). Peruski et al.36 determined theoretically and experimentally that the U60 clusters approach a center-to-center distance of 5.0−5.5 nm in the aqueous phase when near the solubility limit. Closer association of the clusters with each other is restricted by the electric double layer surrounding each cage. The packing distance calculated in the present study approaches these values. Even greater agreement is reached at pH 8, when approximately 1.5 times as much U60 is removed from solution. The calculated center-to-center distance is 5.4 nm. Since we expect U60 to associate with the goethite surface through an electrostatic outer-sphere complex, we might expect similar packing to what is found in saturated solutions. The experiments presented here are at a much lower U60 concentration than those of Peruski et al.;36 however, the
Figure 1. Removal of uranium from solution as a function of time and goethite concentration in systems containing 0.5 g·L−1 U60 at pH 9. Data points represent the average of duplicate samples. Error bars represent propagation of error based on the uncertainty of ICP-OES measurements and gravimetric sample preparation.
m2·L−1 to 500 m2·L−1, more surface area becomes available, and a larger fraction of U60 is removed. Each system appeared to reach a steady-state within the time frame of this study (i.e., within 5 days). The fraction of uranium removed from solution decreased with increasing U60 concentration (see Figure 2). This is expected because as the U60 concentration increases at
Figure 2. Removal of uranium from solution as a function of time and U60 concentration in systems containing 500 m2·L−1 goethite at pH 9. Data points represent the average of duplicate samples. Error bars represent propagation of error based on the uncertainty of ICP-OES measurements and gravimetric sample preparation. D
DOI: 10.1021/acs.est.8b02716 Environ. Sci. Technol. XXXX, XXX, XXX−XXX
Article
Environmental Science & Technology
charge and attract more U60 to the mineral surface through electrostatic interactions. As the pH is increased from pH 8 to pH 10, there are fewer positive mineral sites, and less U60 is removed from solution. Despite pH 9 and 10 being at and above the point of zero charge, respectively, there was still some U60 removed from solution. Since the PZC is simply the average of all positive, negative, and neutral mineral sites which sum to zero, there will still be some positive sites present at the PZC which could attract the negatively charged U60 nanocluster. If U60 is interacting via weak electrostatic interactions, the sorption process should be reversible. Desorption experiments of 1 g·L−1 U60 to 500 m2·L−1 goethite at pH 9 revealed that the sorption of U60 to goethite was reversible under certain pH conditions. While no appreciable amount of uranium was desorbed from the surface at pH 8, approximately 20% was resuspended at pH 10. Figure 4 shows the ESI-MS fingerprint
packing within the electric double layer is nearly the same and may be due to the suppression of the electric double layer surrounding each nanocluster as it interacts with the positive potential of the goethite surface. ICP-OES was used to measure the concentrations of K+ and + Li in the aqueous phase as a function of time. K+ and Li+ cations are present from the original U60 crystals that were dissolved. The largest fraction of Li removed, in relation to U and K, was found in systems containing 2 g·L−1 U60. On the contrary, the least fraction of Li in relation to U and K removed was observed in the 0.5 g·L−1 U60 system (see the Supporting Information). The concentration of potassium decreased at a rate similar to that of uranium at each U60 concentration (see the Supporting Information). These results support previous findings which demonstrate that counterions are more strongly associated with the negatively charged uranyl peroxide cage as the concentration of U60 increases and that K+ ions are more closely associated with the cage than Li+.17,18 Since lithium ions are more likely dissociated from U60 at lower concentrations, the uranyl peroxide cage has greater effective negative charge, and we are likely to see more rapid uptake as shown in Figure 2. ESI-MS and SAXS data demonstrated that the U60 clusters remained intact in solution and were present over the duration of the batch sorption experiments (see the Supporting Information). The average molecular weight, of multiple charge states, determined by ESI-MS and the average size and shape of the uranyl clusters in solutions remained approximately constant throughout the sorption experiments. Sorption−Desorption as a Function of pH. Figure 3 presents the sorption of 0.5 g·L−1 U60 to 200 m2·L−1 goethite
Figure 3. Removal of uranium from solution as a function of time and pH in systems containing 0.5 g·L−1 U60 and 200 m2·L−1 goethite. Data points represent the average of duplicate samples. Error bars represent propagation of error based on the uncertainty of ICP-OES measurements and gravimetric sample preparation.
Figure 4. ESI-MS fingerprint of 1 g·L−1 U60 equilibrated with 500 m2· L−1 goethite for 3 days (A) and desorbed at pH 10 after 3 days (B).
of U60 that remained in solution in the presence of goethite after 3 days of contact (Figure 4A) and the fingerprint of U60 that was desorbed at pH 10 over the same amount of time (Figure 4B). This strongly suggests that discrete U60 sorbs to the goethite surface intact. Kinetics of U60 Interactions with Goethite. The sorption curves presented in Figures 1 and 2 were used to determine the reaction rate constant (krxn) and reaction orders
as a function of pH. The rate and percentage of uranium removed from solution increased with decreasing pH. ESI-MS revealed that clusters remained intact despite pH adjustment (see the Supporting Information) and controls showed no sign of uranium removal from solution in the absence of goethite. At pH 8 the goethite surface will retain the greatest net positive E
DOI: 10.1021/acs.est.8b02716 Environ. Sci. Technol. XXXX, XXX, XXX−XXX
Article
Environmental Science & Technology
an overall reaction rate constant (krxn) of (6.7 ± 2.0) × 10−4 (g·L−1)0.71±0.02(m2·L−1)−1.2±0.1(day−1) such that the overall rate law describing U60 interactions with goethite at pH 9 could be described by
with respect to U 60 concentration (a) and goethite concentration (b). Linear regressions based on eq 5 were used to derive k′rxn (see the Supporting Information). The reaction order with respect to goethite, 1.2 ± 0.1, was obtained from a log−log plot of k′rxn versus goethite concentration (see Figure 5). Similarly, linear regressions based on eq 8 were used
−
d[U60] = krxn[U60]0.29 ± 0.02 [goethite]1.2 ± 0.1 dt
(10)
These results indicate that the kinetics of U60 sorption to goethite are more strongly dictated by the concentration of goethite than by the concentration of U60. Although pH was varied, the concentration of protons in solution was not incorporated into the rate law due to the narrow pH stability range of U60 and its lack of acid−base chemistry.13 U60 Associated with the Goethite Surface. U 4f and Fe 2p electrons were probed using XPS to determine the oxidation state of each component on the reacted goethite surface (see the Supporting Information). The iron in goethite was fit without any contribution from Fe(II), suggesting that the removal of clusters from solution was likely not due to the reduction of the U(VI) to U(IV). U 4f5/2 and U 4f 7/2 corelevel peaks showed U(VI) satellites at approximately 4 eV, and the spin−orbit interactions separated the U 4f 7/2 and U 4f5/2 peaks by around 10.9 eV.34 Reacted powder from systems containing 1 and 2 g·L−1 U60 with 500 m2·L−1 goethite was analyzed by XPS. U 4f 7/2 and U 4f5/2 peaks occurred at 381.32 and 392.19 and 381.00 and 391.90, while U(VI) satellites occurred at 385.01, 395.76 and 385.07, 396.08 respectively (see the Supporting Information). XPS demonstrated that the uranium species deposited on the surface is U(VI) with no contribution from U(IV) or U(V). These results confirm that uranium is indeed associated with the goethite surface but do not prove whether uranium is present as discrete U(VI), as U60, or as a U(VI) precipitate. It is unclear what happens to U60 when subjected to the vacuum and X-ray beam during an XPS measurement. Previous studies show that U60 flattens and converts to UO2 during TEM analysis (300 kV operating voltage and ∼10−4 Pa).25 While we reasonably expect the vacuum of the XPS (∼10−6 Pa) to compromise the hollow cage structure of U60, our results show that the electron beam (94 eV) does not induce reduction of U(VI) to U(IV), which would presumably result in destruction of the clusters. U 4f 7/2 peaks were effectively fit with a single band which indicates a single uranium species was associated with the goethite mineral surface. These results, in addition to separate desorption experiments and ESI-MS results reported above, suggest that this single species was U60. U60 Removal Mechanism. At lower pH values and increased goethite concentration there is an increase in the amount of U60 removed from solution. We hypothesize that this is due to electrostatic interactions between the negatively charged U60 cluster and the positively charged goethite surface when the pH of the solution is near or below the point of zero charge of goethite. The effective negative charge of the uranyl peroxide cage finds a charge balance within the electric double layer of the goethite surface. Given the unreactive ‘-yl’ oxygens which truncate the uranyl cage and the relatively low charge density of U60 nanoclusters, we suspect that U60 is not interacting with goethite via an inner-sphere sorption complex. It is much more likely that it is interacting via an outer-sphere complex driven by weak electrostatic interactions between the anionic cage and the positive potential of the goethite particles in solution.
Figure 5. Dependence of log(k′rxn) on log([goethite]). Data points represent the average of duplicate samples. Error bars represent propagation of error based on ICP-OES measurements and gravimetric sample preparation; the shaded area represents a 95% confidence interval for the linear regression (R2 = 0.987). Reaction term b = 1.2 ± 0.1 and krxn = (7.4 ± 3.9) × 10−4 (g·L−1)0.71±0.02(m2· L−1)−1.2±0.1(day−1).
to derive k′rxn (see the Supporting Information), which was then plotted as a function of U60 concentration to derive the reaction order with respect to U60 concentration, 0.29 ± 0.02 (see Figure 6). Combining data from Figures 5 and 6 leads to
Figure 6. Dependence of log(k′rxn) on log([U60]). Data points represent the average of duplicate samples. Error bars represent propagation of error based on ICP-OES measurements and gravimetric sample preparation; the shaded area represents a 95% confidence interval for the linear regression (R2 = 0.986). Reaction term a = 0.29 ± 0.02 and krxn = (5.94 ± 0.08) × 10−4 (g· L−1)0.71±0.02(m2·L−1)−1.2±0.1(day−1). F
DOI: 10.1021/acs.est.8b02716 Environ. Sci. Technol. XXXX, XXX, XXX−XXX
Article
Environmental Science & Technology
‘-yl’ oxygens and full coordination in the equatorial plane or perhaps a K+-bridged ternary complex and demonstrate that steady-state is achieved within a longer time frame (i.e., days). These different sorption mechanisms are also manifested in different desorption behaviors. No appreciable U60 is desorbed from the goethite surface at pH 8 within 3 days, and only 20% is removed within the same time frame at pH 10. While there are some studies demonstrating rapid removal of U(VI) from goethite,41,42 they are conducted at lower pH and require the addition of complexing agents to the desorption solution. No such complexing agents are required for U60 desorption. The greatest difference between U(VI) and U60 behavior at the goethite-water interface is manifested in the extremely large mineral surface areas which are required to remove U60 from solution. This, combined with their high solubility, suggests that uranyl peroxide nanoclusters may be more mobile in the environment than U(VI), which has the potential to alter our current understanding of the fate and transport of uranium species in the environment.
When the pH of the solution is above the point of zero charge, we see that a larger fraction of K+ is removed from solution with the uranium. This suggests that U60 may interact with the mineral surface through the formation of a cationbridged complex. By monitoring the concentration of potassium and lithium in solution, we determined that a larger fraction of lithium remains in solution, while potassium is removed from solution nearly identically to uranium. This suggests that lithium dissociates from U60, and if a cationbridged surface complex is formed, it is facilitated by potassium instead of lithium. These results are similar to those found for U60 sorption to hematite.24 To ensure that the reaction rate could be measured in a reasonable amount of time (i.e., days to weeks instead of months), the amount of goethite used in the present study was significantly higher than in our previous work involving hematite.24 The results presented here build upon this previously published work by defining the relationship between pH and the removal of U60 from solution. We were also able to demonstrate the reversibility of the sorption process, which supports the hypothesis that U60 is bound by weak electrostatic interactions. Steady-state was achieved in the presence of goethite because the pH did not drop as rapidly as experiments in the presence of hematite. Early time points were near pH 9 in our hematite experiments with comparable concentrations of U60 and mineral to the reactions presented here. However, much less loading was achieved in a system containing 1 g·L−1 and 200 m2·L−1 hematite, leading to a calculated U60 center-tocenter distance of ∼9 nm. We believe this may be explained by the lower PZC of hematite compared to goethite, which would lead to a greater proportion of negatively charged surface sites in comparison to goethite. XPS confirmed that a single U(VI) bearing species was associated with the reacted goethite surface, and ESI-MS revealed that U60 sorption was reversible at pH 10 and that U60 survived the sorption−desorption process. ESI-MS and SAXS data attest to the persistence of the clusters in the presence of goethite during the sorption experiments and suggest that the removal of U60 from solution is due to interactions with the mineral surface. While we cannot explicitly rule out the possibility of a uranium phase precipitated on the goethite surface, we believe there is enough evidence to suggest this is not the case. We know that surface-induced crystallization of U60 is not occurring due to the high solubility of U60,36 the lack of a precipitate in mineral-free controls, and the observed dissociation of Li+ from the clusters, which is needed for crystallization. In addition, our desorption experiments show that when uranium is desorbed from goethite, U60 is present in the aqueous phase. This suggests that U60 is associated with the goethite surface but could also be explained by the formation of a precipitate containing U60. The amount of uranium associated with goethite is not high enough to detect by methods such as powder X-ray diffraction (pXRD), but our previous work did not show a change in the pXRD pattern even after hematite had been exposed to a solution containing U60 for 120 days.24 Environmental Implications. The behavior of U60 at the goethite-water interface is similar to that of discrete U(VI) but is governed by different sorption mechanisms and reaction kinetics. While U(VI) forms inner-sphere complexes with goethite21,40 and is characterized by fast sorption kinetics (i.e., minutes-hours),41,42 we hypothesize that U60 behavior is dominated by outer-sphere interactions due to the unreactive
■
ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.est.8b02716.
■
Detailed description of goethite synthesis and characterization, percent ion removal comparisons, SAXS, ESIMS, and XPS spectra, and a detailed, step-by-step description of the kinetic analysis and error propagation (PDF)
AUTHOR INFORMATION
Corresponding Author
*Phone: 574-631-1872. Fax: 574-631-9236. E-mail: ahixon@ nd.edu. ORCID
Amy E. Hixon: 0000-0003-4513-4574 Author Contributions
The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. Notes
The authors declare no competing financial interest.
■
ACKNOWLEDGMENTS The authors thank Mr. Samuel N. Perry for assistance with CrystalMaker. The following centers and facilities at the University of Notre Dame provided access to instrumentation used in this research study: the Center for Environmental Science and Technology (BET, ICP-OES, zeta potential), the Mass Spectrometry and Proteomics Facility (ESI-MS), and the Center for Sustainable Energy’s Materials Characterization Facility (pXRD, Raman, XPS). This material is based on work supported as part of the Materials Science of Actinides, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under award number DE-SC0001089.
■
REFERENCES
(1) Walther, C.; Denecke, M. A. Actinide Colloids and Particles of Environmental Concern. Chem. Rev. 2013, 113 (2), 995−1015.
G
DOI: 10.1021/acs.est.8b02716 Environ. Sci. Technol. XXXX, XXX, XXX−XXX
Article
Environmental Science & Technology (2) RES3T - Rossendorf Expert System for Surface and Sorption Thermodynamics. https://www.hzdr.de/db/res3t.login (accessed Aug 7, 2018). (3) Hu, W.; Lu, S.; Song, W.; Chen, T.; Hayat, T.; Alsaedi, N. S.; Chen, C.; Liu, H. Competitive Adsorption of U(VI) and Co(II) on Montmorillonite: A Batch and Spectroscopic Approach. Appl. Clay Sci. 2018, 157, 121−129. (4) Xu, H.; Liu, G.; Li, G.; Ren, X.; Gong, Y.; Chen, X.; Tan, X. Kinetic and Thermodynamic Studies on the Interaction of Europium(III) and Phosphate with γ-Al2O3. J. Radioanal. Nucl. Chem. 2017, 311 (1), 395−408. (5) Zhao, P.; Begg, J. D.; Zavarin, M.; Tumey, S. J.; Williams, R.; Dai, Z. R.; Kips, R.; Kersting, A. B. Plutonium(IV) and (V) Sorption to Goethite at Sub-Femtomolar to Micromolar Concentrations: Redox Transformations and Surface Precipitation. Environ. Sci. Technol. 2016, 50 (13), 6948−6956. (6) Hixon, A. E.; Powell, B. A. Observed Changes in the Mechanism and Rates of Pu(V) Reduction on Hematite As a Function of Total Plutonium Concentration. Environ. Sci. Technol. 2014, 48 (16), 9255−9262. (7) Um, W.; Serne, R. J.; Brown, C. F.; Rod, K. A. Uranium(VI) Sorption on Iron Oxides in Hanford Site Sediment: Application of a Surface Complexation Model. Appl. Geochem. 2008, 23 (9), 2649− 2657. (8) Kubatko, K.-A. H.; Helean, K. B.; Navrotsky, A.; Burns, P. C. Stability of Peroxide-Containing Uranyl Minerals. Science 2003, 302 (5648), 1191−1193. (9) Burns, P. C.; Ewing, R. C.; Navrotsky, A. Nuclear Fuel in a Reactor Accident. Science 2012, 335 (6073), 1184−1188. (10) Armstrong, C. R.; Nyman, M.; Shvareva, T.; Sigmon, G. E.; Burns, P. C.; Navrotsky, A. Uranyl Peroxide Enhanced Nuclear Fuel Corrosion in Seawater. Proc. Natl. Acad. Sci. U. S. A. 2012, 109 (6), 1874−1877. (11) Peterson, R. A.; Buck, E. C.; Chun, J.; Daniel, R. C.; Herting, D. L.; Ilton, E. S.; Lumetta, G. J.; Clark, S. B. Review of the Scientific Understanding of Radioactive Waste at the U.S. DOE Hanford Site. Environ. Sci. Technol. 2018, 52 (2), 381−396. (12) Soltis, J. A.; Wallace, C. M.; Penn, R. L.; Burns, P. C. CationDependent Hierarchical Assembly of U60 Nanoclusters into MacroIon Assemblies Imaged via Cryogenic Transmission Electron Microscopy. J. Am. Chem. Soc. 2016, 138 (1), 191−198. (13) Qiu, J.; Burns, P. C. Clusters of Actinides with Oxide, Peroxide, or Hydroxide Bridges. Chem. Rev. 2013, 113 (2), 1097−1120. (14) Burns, P. C.; Nyman, M. Captivation with Encapsulation: A Dozen Years of Exploring Uranyl Peroxide Capsules. Dalton Trans. 2018, 47 (17), 5916−5927. (15) Sigmon, G. E.; Unruh, D. K.; Ling, J.; Weaver, B.; Ward, M.; Pressprich, L.; Simonetti, A.; Burns, P. C. Symmetry versus Minimal Pentagonal Adjacencies in Uranium-Based Polyoxometalate Fullerene Topologies. Angew. Chem., Int. Ed. 2009, 48 (15), 2737−2740. (16) Olds, T. A.; Dembowski, M.; Wang, X.; Hoffman, C.; Alam, T. M.; Hickam, S.; Pellegrini, K. L.; He, J.; Burns, P. C. Single-Crystal Time-of-Flight Neutron Diffraction and Magic-Angle-Spinning NMR Spectroscopy Resolve the Structure and 1H and 7Li Dynamics of the Uranyl Peroxide Nanocluster U60. Inorg. Chem. 2017, 56 (16), 9676− 9683. (17) Gao, Y.; Haso, F.; Szymanowski, J. E. S.; Zhou, J.; Hu, L.; Burns, P. C.; Liu, T. Selective Permeability of Uranyl Peroxide Nanocages to Different Alkali Ions: Influences from Surface Pores and Hydration Shells. Chem. - Eur. J. 2015, 21 (51), 18785−18790. (18) Flynn, S. L.; Szymanowski, J. E. S.; Gao, Y.; Liu, T.; Burns, P. C.; Fein, J. B. Experimental Measurements of U60 Nanocluster Stability in Aqueous Solution. Geochim. Cosmochim. Acta 2015, 156, 94−105. (19) Guo, Z.; Li, Y.; Wu, W. Sorption of U(VI) on Goethite: Effects of PH, Ionic Strength, Phosphate, Carbonate and Fulvic Acid. Appl. Radiat. Isot. 2009, 67 (6), 996−1000.
(20) Jung, H. B.; Xu, H.; Konishi, H.; Roden, E. E. Role of NanoGoethite in Controlling U(VI) Sorption-Desorption in Subsurface Soil. J. Geochem. Explor. 2016, 169, 80−88. (21) Sherman, D. M.; Peacock, C. L.; Hubbard, C. G. Surface Complexation of U(VI) on Goethite (Alpha-FeOOH). Geochim. Cosmochim. Acta 2008, 72 (2), 298−310. (22) Singh, A.; Ulrich, K.-U.; Giammar, D. E. Impact of Phosphate on U(VI) Immobilization in the Presence of Goethite. Geochim. Cosmochim. Acta 2010, 74 (22), 6324−6343. (23) McBriarty, M. E.; Soltis, J. A.; Kerisit, S.; Qafoku, O.; Bowden, M. E.; Bylaska, E. J.; De Yoreo, J. J.; Ilton, E. S. Trace Uranium Partitioning in a Multiphase Nano-FeOOH System. Environ. Sci. Technol. 2017, 51 (9), 4970−4977. (24) Sadergaski, L. R.; Stoxen, W.; Hixon, A. E. Uranyl Peroxide Nanocluster (U60) Persistence and Sorption in the Presence of Hematite. Environ. Sci. Technol. 2018, 52 (5), 3304−3311. (25) Liu, Y.; Czarnecki, A.; Szymanowski, J. E. S.; Sigmon, G. E.; Burns, P. C. Extraction of Uranyl Peroxo Clusters from Aqueous Solution by Mesoporous Silica SBA-15. J. Radioanal. Nucl. Chem. 2015, 303 (3), 2257−2262. (26) McGrail, B. T.; Sigmon, G. E.; Jouffret, L. J.; Andrews, C. R.; Burns, P. C. Raman Spectroscopic and ESI-MS Characterization of Uranyl Peroxide Cage Clusters. Inorg. Chem. 2014, 53 (3), 1562− 1569. (27) Schwertmann, U.; Cornell, R. M. Iron Oxides in the Laboratory: Preparation and Characterization; VCH Publishers, Inc.: New York, NY, 1991. (28) Hanesch, M. Raman Spectroscopy of Iron Oxides and (Oxy)Hydroxides at Low Laser Power and Possible Applications in Environmental Magnetic Studies. Geophys. J. Int. 2009, 177 (3), 941− 948. (29) Kosmulski, M.; Maczka, E.; Jartych, E.; Rosenholm, J. B. Synthesis and Characterization of Goethite and Goethite−Hematite Composite: Experimental Study and Literature Survey. Adv. Colloid Interface Sci. 2003, 103 (1), 57−76. (30) Villalobos, M.; Trotz, M. A.; Leckie, J. O. Variability in Goethite Surface Site Density: Evidence from Proton and Carbonate Sorption. J. Colloid Interface Sci. 2003, 268 (2), 273−287. (31) Hiemstra, T.; Van Riemsdijk, W. H. Physical Chemical Interpretation of Primary Charging Behaviour of Metal (Hydr) Oxides. Colloids Surf. 1991, 59, 7−25. (32) Shirley, D. A. High-Resolution X-Ray Photoemission Spectrum of the Valence Bands of Gold. Phys. Rev. B 1972, 5 (12), 4709−4714. (33) Lin, T.-C.; Seshadri, G.; Kelber, J. A. A Consistent Method for Quantitative XPS Peak Analysis of Thin Oxide Films on Clean Polycrystalline Iron Surfaces. Appl. Surf. Sci. 1997, 119 (1), 83−92. (34) Schindler, M.; Hawthorne, F. C.; Freund, M. S.; Burns, P. C. XPS Spectra of Uranyl Minerals and Synthetic Uranyl Compounds. I: The U 4f Spectrum. Geochim. Cosmochim. Acta 2009, 73 (9), 2471− 2487. (35) Liu, Y.; Szymanowski, J. E. S.; Sigmon, G. E.; Morris, D. E.; Hixon, A. E.; Migliori, A.; Burns, P. C. Measurement of the Effective Capacitance of Solutions Containing Nanoscale Uranyl Peroxide Cage Clusters U6) Reveals Cluster Effects. J. Radioanal. Nucl. Chem. 2018, 315 (2), 341−346. (36) Peruski, K. M.; Bernales, V.; Dembowski, M.; Lobeck, H. L.; Pellegrini, K. L.; Sigmon, G. E.; Hickam, S.; Wallace, C. M.; Szymanowski, J. E. S.; Balboni, E.; Gagliardi, L.; Burns, P. C. Uranyl Peroxide Cage Cluster Solubility in Water and the Role of the Electrical Double Layer. Inorg. Chem. 2017, 56 (3), 1333−1339. (37) Feigin, L. A.; Svergun, D. I. Structure Analysis by Small-Angle XRay and Neutron Scattering; Taylor, G. W., Ed.; Plenum Press: New York, NY, 1987; DOI: 10.1007/978-1-4757-6624-0. (38) Davis, J. A.; Kent, D. B. Surface Complexation Modeling in Aqueous Geochemistry. In Mineral-Water Interface Geochemistry; Hochella, M. F., Jr., White, A. F., Eds.; Ribbe, P. H., Series Ed.; Reviews in Mineralogy; Mineralogical Society of America: Washington, DC, 1990; Vol. 23, pp 177−260. H
DOI: 10.1021/acs.est.8b02716 Environ. Sci. Technol. XXXX, XXX, XXX−XXX
Article
Environmental Science & Technology (39) Hiemstra, T.; Van Riemsdijk, W. H.; Bolt, G. H. Multisite Proton Adsorption Modeling at the Solid/Solution Interface of (Hydr) Oxides: A New Approach. I. Model Description and Evaluation of Intrinsic Reaction Constants. J. Colloid Interface Sci. 1989, 133 (1), 91−104. (40) Moyes, L.; Parkman, R.; Charnock, J.; Vaughan, D.; Livens, F.; Hughes, C.; Braithwaite, A. Uranium Uptake from Aqueous Solution by Interaction with Goethite, Lepidocrocite, Muscovite, and Mackinawite: An X-Ray Absorption Spectroscopy Study. Environ. Sci. Technol. 2000, 34 (6), 1062−1068. (41) Giammar, D. E.; Hering, J. G. Time Scales for Sorption− Desorption and Surface Precipitation of Uranyl on Goethite. Environ. Sci. Technol. 2001, 35 (16), 3332−3337. (42) Qian, L.; Ma, M.; Cheng, D. Adsorption and Desorption of Uranium on Nano Goethite and Nano Alumina. J. Radioanal. Nucl. Chem. 2015, 303 (1), 161−170.
I
DOI: 10.1021/acs.est.8b02716 Environ. Sci. Technol. XXXX, XXX, XXX−XXX
