All Publications

  • Electrolytes with moderate lithium polysulfide solubility for high-performance long-calendar-life lithium-sulfur batteries. Proceedings of the National Academy of Sciences of the United States of America Gao, X., Yu, Z., Wang, J., Zheng, X., Ye, Y., Gong, H., Xiao, X., Yang, Y., Chen, Y., Bone, S. E., Greenburg, L. C., Zhang, P., Su, H., Affeld, J., Bao, Z., Cui, Y. 2023; 120 (31): e2301260120


    Lithium-sulfur (Li-S) batteries with high energy density and low cost are promising for next-generation energy storage. However, their cycling stability is plagued by the high solubility of lithium polysulfide (LiPS) intermediates, causing fast capacity decay and severe self-discharge. Exploring electrolytes with low LiPS solubility has shown promising results toward addressing these challenges. However, here, we report that electrolytes with moderate LiPS solubility are more effective for simultaneously limiting the shuttling effect and achieving good Li-S reaction kinetics. We explored a range of solubility from 37 to 1,100 mM (based on S atom, [S]) and found that a moderate solubility from 50 to 200 mM [S] performed the best. Using a series of electrolyte solvents with various degrees of fluorination, we formulated the Single-Solvent, Single-Salt, Standard Salt concentration with Moderate LiPSs solubility Electrolytes (termed S6MILE) for Li-S batteries. Among the designed electrolytes, Li-S cells using fluorinated-1,2-diethoxyethane S6MILE (F4DEE-S6MILE) showed the highest capacity of 1,160 mAh g-1 at 0.05 C at room temperature. At 60 °C, fluorinated-1,4-dimethoxybutane S6MILE (F4DMB-S6MILE) gave the highest capacity of 1,526 mAh g-1 at 0.05 C and an average CE of 99.89% for 150 cycles at 0.2 C under lean electrolyte conditions. This is a fivefold increase in cycle life compared with other conventional ether-based electrolytes. Moreover, we observed a long calendar aging life, with a capacity increase/recovery of 4.3% after resting for 30 d using F4DMB-S6MILE. Furthermore, the correlation between LiPS solubility, degree of fluorination of the electrolyte solvent, and battery performance was systematically investigated.

    View details for DOI 10.1073/pnas.2301260120

    View details for PubMedID 37487097

  • X-ray Absorption Spectroscopy Reveals Mechanisms of Calcium and Silicon Fouling on Reverse Osmosis Membranes Used in Wastewater Reclamation ACS ES&T WATER Niemann, V. A., Huck, M., Steinrueck, H., Toney, M. F., Tarpeh, W. A., Bone, S. E. 2023
  • Microporous Polyethersulfone Membranes Grafted with Zwitterionic Polymer Brushes Showing Microfiltration Permeance and Ultrafiltration Bacteriophage Removal. ACS applied materials & interfaces Qin, J., Ziemann, E., Bar-Zeev, E., Bone, S. E., Liang, Y., Mauter, M. S., Herzberg, M., Bernstein, R. 2023


    Virus removal from water using microfiltration (MF) membranes is of great interest but remains challenging owing to the membranes' mean pore sizes typically being significantly larger than most viruses. We present microporous membranes grafted with polyzwitterionic brushes (N-dimethylammonium betaine) that combine bacteriophage removal in the range of ultrafiltration (UF) membranes with the permeance of MF membranes. Brush structures were grafted in two steps: free-radical polymerization followed by atom transfer radical polymerization (ATRP). Attenuated total reflection Fourier transform infrared (ATR-FTIR) and X-ray photoelectron (XPS) verified that grafting occurred at both sides of the membranes and that the grafting increased with increasing the zwitterion monomer concentration. The log reduction values (LRVs) of the pristine membrane increased from less than 0.5 LRV for T4 (100 nm) and NT1 (50 nm) bacteriophages to up to 4.5 LRV for the T4 and 3.1 LRV for the NT1 for the brush-grafted membranes with a permeance of about 1000 LMH/bar. The high permeance was attributed to a high-water fraction in the ultra-hydrophilic brush structure. The high measured LRVs of the brush-grafted membranes were attributed to enhanced bacteriophages exclusion from the membrane surface and entrapment of the ones that penetrated the pores due to the membranes' smaller mean pore-size and cross-section porosity than those of the pristine membrane, as seen by scanning electron microscopy (SEM) and measured using liquid-liquid porometry. Micro X-ray fluorescence (mu-XRF) spectrometry and nanoscale secondary ion mass spectrometry showed that 100 nm Si-coated gold nanospheres accumulated on the surface of the pristine membrane but not on the brush-coated membrane and that the nanospheres that penetrated the membranes were entrapped in the brush-grafted membrane but passed the pristine one. These results corroborate the LRVs obtained during filtration experiments and support the inference that the increased removal was due to a combined exclusion mechanism and entrapment. Overall, these microporous brush-grafted membranes show potential for use in advanced water treatment.

    View details for DOI 10.1021/acsami.3c01495

    View details for PubMedID 37010122

  • Creating water-in-salt-like environment using coordinating anions in non-concentrated aqueous electrolytes for efficient Zn batteries ENERGY & ENVIRONMENTAL SCIENCE Vazquez, D., Pollard, T. P., Mars, J., Yoo, J., Steinrueck, H., Bone, S. E., Safonova, O., Toney, M. F., Borodin, O., Lukatskaya, M. R. 2023

    View details for DOI 10.1039/d3ee00205e

    View details for Web of Science ID 000950522800001

  • Nitrate-Stimulated Release of Naturally Occurring Sedimentary Uranium. Environmental science & technology Westrop, J. P., Yadav, P., Nolan, P. J., Campbell, K. M., Singh, R., Bone, S. E., Chan, A. H., Kohtz, A. J., Pan, D., Healy, O., Bargar, J. R., Snow, D. D., Weber, K. A. 2023


    Groundwater uranium (U) concentrations have been measured above the U.S. EPA maximum contaminant level (30 mug/L) in many U.S. aquifers, including in areas not associated with anthropogenic contamination by milling or mining. In addition to carbonate, nitrate has been correlated to uranium groundwater concentrations in two major U.S. aquifers. However, to date, direct evidence that nitrate mobilizes naturally occurring U from aquifer sediments has not been presented. Here, we demonstrate that the influx of high-nitrate porewater through High Plains alluvial aquifer silt sediments bearing naturally occurring U(IV) can stimulate a nitrate-reducing microbial community capable of catalyzing the oxidation and mobilization of U into the porewater. Microbial reduction of nitrate yielded nitrite, a reactive intermediate, which was further demonstrated to abiotically mobilize U from the reduced alluvial aquifer sediments. These results indicate that microbial activity, specifically nitrate reduction to nitrite, is one mechanism driving U mobilization from aquifer sediments in addition to previously described bicarbonate-driven desorption from mineral surfaces, such as Fe(III) oxides.

    View details for DOI 10.1021/acs.est.2c07683

    View details for PubMedID 36848522

  • Successful Conversion of Pb-Contaminated Soils to Low-Bioaccessibility Plumbojarosite Using Potassium-Jarosite at Ambient Temperature. Environmental science & technology Sowers, T. D., Blackmon, M. D., Bone, S. E., Kirby, A. M., Jerden, M. L., Noerpel, M. R., Scheckel, K. G., Bradham, K. D. 2022


    Methods promoting lead (Pb) phase transformation in soils are essential for decreasing Pb bioaccessibility/bioavailability and may offer an in situ, cost-efficient process for mitigating contaminant exposure. Recent plumbojarosite (PLJ) conversion methods have shown the greatest potential to reduce soil Pb bioaccessibility, an in vitro bioaccessibility assay measurement of the proportion of Pb solubilized under gastric chemical conditions. Soils tested utilizing the recent PLJ method were found to have a Pb bioaccessibility of <1%, compared to original soils possessing bioaccessibility of >70%. However, this technique requires heat (95-100 °C) to promote mineral transformation. Jarosite-group minerals may incorporate multiple interlayer cations; therefore, we probed the potential for jarosite to remediate Pb via intercalation by reacting presynthesized potassium (K)-jarosite with aqueous Pb and/or Pb-contaminated soil at room temperature. Both K-jarosite and heated PLJ-treated samples were investigated by pairing bioaccessibility analyses with advanced bulk and spatially resolved X-ray absorption spectroscopy analyses. Samples treated with K-jarosite promoted Pb transformation to low-bioaccessibility (<10%) PLJ, with soil being converted to 100% PLJ using both heated and nonheated techniques. mu-X-ray fluorescence (mu-XRF) and mu-X-ray absorption near-edge structure (mu-XANES) showcase significant differences between elemental interactions for heated and nonheated PLJ-treated samples with anglesite impurities being found on the microscale. Although further development is necessary to accommodate for suitable field conditions, results indicate, for the first time, that K-jarosite may successfully convert soil Pb to PLJ without high-temperature conditions. The newfound utility of K-jarosite is expected to be key to future jarosite-based soil Pb remediation method development.

    View details for DOI 10.1021/acs.est.2c05606

    View details for PubMedID 36239028

  • Mercury Removal from Contaminated Water by Wood-Based Biochar Depends on Natural Organic Matter and Ionic Composition. Environmental science & technology Chaudhuri, S., Sigmund, G., Bone, S. E., Kumar, N., Hofmann, T. 2022


    Biochars can remove potentially toxic elements, such as inorganic mercury [Hg(II)] from contaminated waters. However, their performance in complex water matrices is rarely investigated, and the combined roles of natural organic matter (NOM) and ionic composition in the removal of Hg(II) by biochar remain unclear. Here, we investigate the influence of NOM and major ions such as chloride (Cl-), nitrate (NO3-), calcium (Ca2+), and sodium (Na+) on Hg(II) removal by a wood-based biochar (SWP700). Multiple sorption sites containing sulfur (S) were located within the porous SWP700. In the absence of NOM, Hg(II) removal was driven by these sites. Ca2+ bridging was important in enhancing removal of negatively charged Hg(II)-chloro complexes. In the presence of NOM, formation of soluble Hg-NOM complexes (as seen from speciation calculations), which have limited access to biochar pores, suppressed Hg(II) removal, but Cl- and Ca2+ could still facilitate it. The ability of Ca2+ to aggregate NOM, including Hg-NOM complexes, promoted Hg(II) removal from the dissolved fraction (<0.45 mum). Hg(II) removal in the presence of Cl- followed a stepwise mechanism. Weakly bound oxygen functional groups in NOM were outcompeted by Cl-, forming smaller-sized Hg(II)-chloro complexes, which could access additional intraparticle sorption sites. Therein, Cl- was outcompeted by S, which finally immobilized Hg(II) in SWP700 as confirmed by extended X-ray absorption fine structure spectroscopy. We conclude that in NOM containing oxic waters, with relatively high molar ratios of Cl-: NOM and Ca2+: NOM, Hg(II) removal can still be effective with SWP700.

    View details for DOI 10.1021/acs.est.2c01554

    View details for PubMedID 35926116

  • A low input strategy for chromium removal from industrial stormwater using peat sorbent. Journal of environmental quality Stewart, B., Nicholas, S., Bone, S., Tappero, R., Eger, P., Sheik, C., Toner, B. 2022


    Low-cost and low-input water treatment systems are important for industrial stormwater remediation. Here we examine a flow-through reactor treatment installation where water exceeds the allowable maximum concentration for drinking water in multiple metals (e.g., Cr, Cd, Zn) prior to treatment. Specifically, we seek to understand why chromium attenuated in the reactors is not leachable by identifying the specific chemical form of chromium and dominant mechanisms promoting sequestration in the reactors. Total solid-phase chromium concentration in the peat media ranged from 50-150mg/kg after 1 year of exposure to stormwater to 300-900mg/kg after 3.5 years. X-ray fluorescence (XRF) mapping images show chromium, iron, and zinc spatially correlated over a scale of 10 um to 5mm. Chromium rinds form on the edges of peat particles as chromium accumulates. Chromium and iron K-edge X-ray absorption near edge structure (XANES) spectroscopy reveals chromium predominately in the 3+ oxidation state with lesser amounts of elemental chromium. We propose the primary means of chromium attenuation in the reactors is precipitation as Cr-Fe hydroxides combined with trivalent chromium adsorption onto peat surfaces. This article is protected by copyright. All rights reserved.

    View details for DOI 10.1002/jeq2.20397

    View details for PubMedID 35900088

  • Low-energy electronic structure of perovskite and Ruddlesden-Popper semiconductors in the Ba-Zr-S system probed by bond-selective polarized x-ray absorption spectroscopy, infrared reflectivity, and Raman scattering PHYSICAL REVIEW B Ye, K., Koocher, N. Z., Filippone, S., Niu, S., Zhao, B., Yeung, M., Bone, S., Robinson, A. J., Vora, P., Schleife, A., Ju, L., Boubnov, A., Rondinelli, J. M., Ravichandran, J., Jaramillo, R. 2022; 105 (19)
  • Performance and lifetime of intercalative water deionization cells for mono- and divalent ion removal DESALINATION Besli, M. M., Kuppan, S., Bone, S. E., Sainio, S., Hellstrom, S., Christensen, J., Metzger, M. 2021; 517
  • Plumbojarosite Remediation of Soil Affects Lead Speciation and Elemental Interactions in Soil and in Mice Tissues. Environmental science & technology Sowers, T. D., Bone, S. E., Noerpel, M. R., Blackmon, M. D., Karna, R. R., Scheckel, K. G., Juhasz, A. L., Diamond, G. L., Thomas, D. J., Bradham, K. D. 2021


    Lead (Pb) contamination of soils is of global concern due to the devastating impacts of Pb exposure in children. Because early-life exposure to Pb has long-lasting health effects, reducing exposure in children is a critical public health goal that has intensified research on the conversion of soil Pb to low bioavailability phases. Recently, plumbojarosite (PLJ) conversion of highly available soil Pb was found to decrease Pb relative bioavailability (RBA <10%). However, there is sparse information concerning interactions between Pb and other elements when contaminated soil, pre- and post-remediation, is ingested and moves through the gastrointestinal tract (GIT). Addressing this may inform drivers of effective chemical remediation strategies. Here, we utilize bulk and micro-focused Pb X-ray absorption spectroscopy to probe elemental interactions and Pb speciation in mouse diet, cecum, and feces samples following ingestion of contaminated soils pre- and post-PLJ treatment. RBA of treated soils was less than 1% with PLJ phases transiting the GIT with little absorption. In contrast, Pb associated with organics was predominantly found in the cecum. These results are consistent with transit of insoluble PLJ to feces following ingestion. The expanded understanding of Pb interactions during GIT transit complements our knowledge of elemental interactions with Pb that occur at higher levels of biological organization.

    View details for DOI 10.1021/acs.est.1c06067

    View details for PubMedID 34806356

  • Water or Anion? Uncovering the Zn2+ Solvation Environment in Mixed Zn(TFSI)(2) and LiTFSI Water-in-Salt Electrolytes ACS ENERGY LETTERS Zhang, Y., Wan, G., Lewis, N. C., Mars, J., Bone, S. E., Steinrueck, H., Lukatskaya, M. R., Weadock, N. J., Bajdich, M., Borodin, O., Tokmakoff, A., Toney, M. F., Maginn, E. J. 2021; 6 (10): 3458-3463
  • Location-Dependent Cobalt Deposition in Smartphone Cells upon Long-Term Fast-Charging Visualized by Synchrotron X-ray Fluorescence CHEMISTRY OF MATERIALS Besli, M. M., Usubelli, C., Subbaraman, A., Safaei, F., Bone, S., Johnston, C., Schneider, G., Beauchaud, F., Ravi, N., Christensen, J., Doeff, M. M., Metzger, M., Kuppan, S. 2021; 33 (16): 6318-6328
  • Uranium(VI) attenuation in a carbonate-bearing oxic alluvial aquifer. Journal of hazardous materials Nolan, P. J., Bone, S. E., Campbell, K. M., Pan, D., Healy, O. M., Stange, M., Bargar, J. R., Weber, K. A. 2021; 412: 125089


    Uranium minerals are commonly found in soils and sediment across the United States at an average concentration of 2-4mg/kg. Uranium occurs in the environment primarily in two forms, the oxidized, mostly soluble uranium(VI) form, or the reduced, sparingly soluble reduced uranium(IV) form. Here we describe subsurface geochemical conditions that result in low uranium concentrations in an alluvial aquifer with naturally occurring uranium in soils and sediments in the presence of complexing ligands under oxidizing conditions. Groundwater was saturated with respect to calcite and contained calcium (78-90mg/L) with elevated levels of carbonate alkalinity (291-416mg/L as HCO3-). X-ray adsorption near edge structure (XANES) spectroscopy identified that sediment-associated uranium was oxidized as a uranium(VI) form (85%). Calcite was the predominant mineral by mass in the ultrafine fraction in uranium-bearing sediments (>16mg/kg). Groundwater geochemical modeling indicated calcite and/or a calcium-uranyl-carbonate mineral such as liebigite in equilibrium with groundwater. The delta13C (0.57±0.15) was indicative of abiotic carbonate deposition. Thus, solid-phase uranium(VI) associated with carbonate is likely maintaining uranium(VI) groundwater levels below the maximum contaminant level (MCL; 30g/L), presenting a deposition mechanism for uranium attenuation rather than solely a means of mobilization.

    View details for DOI 10.1016/j.jhazmat.2021.125089

    View details for PubMedID 33517059

  • Advanced Characterization in Clean Water Technologies JOULE Bone, S. E., Steinrueck, H., Toney, M. F. 2020; 4 (8): 1637–59
  • Complexation by Organic Matter Controls Uranium Mobility in Anoxic Sediments. Environmental science & technology Bone, S. E., Cliff, J. n., Weaver, K. n., Takacs, C. J., Roycroft, S. n., Fendorf, S. n., Bargar, J. R. 2020


    Uranium contamination threatens the availability of safe and clean drinking water globally. This toxic element occurs both naturally and as a result of mining and ore-processing in alluvial sediments, where it accumulates as tetravalent U [U(IV)], a form once considered largely immobile. Changing hydrologic and geochemical conditions cause U to be released into groundwater. Knowledge of the chemical form(s) of U(IV) is essential to understand the release mechanism, yet the relevant U(IV) species are poorly characterized. There is growing belief that natural organic matter (OM) binds U(IV) and mediates its fate in the subsurface. In this work, we combined nanoscale imaging (nano secondary ion mass spectrometry and scanning transmission X-ray microscopy) with a density-based fractionation approach to physically and microscopically isolate organic and mineral matter from alluvial sediments contaminated with uranium. We identified two populations of U (dominantly +IV) in anoxic sediments. Uranium was retained on OM and adsorbed to particulate organic carbon, comprising both microbial and plant material. Surprisingly, U was also adsorbed to clay minerals and OM-coated clay minerals. The dominance of OM-associated U provides a framework to understand U mobility in the shallow subsurface, and, in particular, emphasizes roles for desorption and colloid formation in its mobilization.

    View details for DOI 10.1021/acs.est.9b04741

    View details for PubMedID 31886668

  • Abiotic phosphorus recycling from adsorbed ribonucleotides on a ferrihydrite-type mineral: Probing solution and surface species. Journal of colloid and interface science Klein, A. R., Bone, S. E., Bakker, E., Chang, Z., Aristilde, L. 2019; 547: 171–82


    Iron (Fe) (oxyhydr)oxide minerals, which are amongst most reactive minerals in soils and sediments, are known to exhibit strong adsorption of inorganic phosphate (Pi) and organophosphate (Po) compounds. Beyond synthetic Po compounds, much still remains unknown about the reactivity of these minerals to transform naturally-occurring Po compounds to Pi, particularly with respect to solution versus surface speciation of Po hydrolysis. To investigate this reactivity with a ferrihydrite-type mineral and ribonucleotides, we employed high-resolution liquid chromatography-mass spectrometry (LC-MS), X-ray absorption near-edge structure (XANES), Fourier-transform infrared (FTIR) spectroscopy, and molecular modeling. Kinetic experiments were conducted with the mineral (1 g L-1) reacted with adenosine monophosphate, diphosphate, or triphosphate (respectively AMP, ADP, ATP; 50 M). Analysis of solution organic species by LC-MS implied that only adsorption occurred with AMP and ADP but both adsorption and dephosphorylation of ATP were evident. Maximum adsorption capacities per gram of mineral were 40.6 ± 0.8 mol AMP, 35.7 ± 1.6 mol ADP, and 10.9 ± 1.0 mol ATP; solution dephosphorylated by-products accounted for 15% of initial ATP. Subsequent XANES analysis of the surface species revealed that 16% of adsorbed AMP and 30% of adsorbed ATP were subjected to dephosphorylation, which was not fully quantifiable from the solution measurements. Molecular simulations predicted that ADP and ATP were complexed mainly via the phosphate groups whereas AMP binding also involved multiple hydrogen bonds with the adenosine moiety; our FTIR data confirmed these binding confirmations. Our findings thus imply that specific adsorption mechanisms dictate the recycling and subsequent trapping of Pi from ribonucleotide-like biomolecules reacted with Fe (oxyhydr)oxide minerals.

    View details for DOI 10.1016/j.jcis.2019.03.086

    View details for PubMedID 30954001

  • Advancing Chelation Chemistry for Actinium and Other +3 f-Elements, Am, Cm, and La. Journal of the American Chemical Society Stein, B. W., Morgenstern, A. n., Batista, E. R., Birnbaum, E. R., Bone, S. E., Cary, S. K., Ferrier, M. G., John, K. D., Pacheco, J. L., Kozimor, S. A., Mocko, V. n., Scott, B. L., Yang, P. n. 2019


    A major chemical challenge facing implementation of 225Ac in targeted alpha therapy-an emerging technology that has potential for treatment of disease-is identifying an 225Ac chelator that is compatible with in vivo applications. It is unclear how to tailor a chelator for Ac binding because Ac coordination chemistry is poorly defined. Most Ac chemistry is inferred from radiochemical experiments carried out on microscopic scales. Of the few Ac compounds that have been characterized spectroscopically, success has only been reported for simple inorganic ligands. Toward advancing understanding in Ac chelation chemistry, we have developed a method for characterizing Ac complexes that contain highly complex chelating agents using small quantities (μg) of 227Ac. We successfully characterized the chelation of Ac3+ by DOTP8- using EXAFS, NMR, and DFT techniques. To develop confidence and credibility in the Ac results, comparisons with +3 cations (Am, Cm, and La) that could be handled on the mg scale were carried out. We discovered that all M3+ cations (M = Ac, Am, Cm, La) were completely encapsulated within the binding pocket of the DOTP8- macrocycle. The computational results highlighted the stability of the M(DOTP)5- complexes.

    View details for DOI 10.1021/jacs.9b10354

    View details for PubMedID 31794205

  • The coordination chemistry of CmIII, AmIII, and AcIII in nitrate solutions: an actinide L3-edge EXAFS study. Chemical science Ferrier, M. G., Stein, B. W., Bone, S. E., Cary, S. K., Ditter, A. S., Kozimor, S. A., Lezama Pacheco, J. S., Mocko, V., Seidler, G. T. 2018; 9 (35): 7078-7090


    Understanding actinide(iii) (AnIII = CmIII, AmIII, AcIII) solution-phase speciation is critical for controlling many actinide processing schemes, ranging from medical applications to reprocessing of spent nuclear fuel. Unfortunately, in comparison to most elements in the periodic table, AnIII speciation is often poorly defined in complexing aqueous solutions and in organic media. This neglect - in large part - is a direct result of the radioactive properties of these elements, which make them difficult to handle and acquire. Herein, we surmounted some of the handling challenges associated with these exotic 5f-elements and characterized CmIII, AmIII, and AcIII using AnIII L3-edge X-ray absorption spectroscopy (XAS) as a function of increasing nitric acid (HNO3) concentration. Our results revealed that actinide aquo ions, An(H2O) x 3+ (x = 9.6 ± 0.7, 8.9 ± 0.8, and 10.0 ± 0.9 for CmIII, AmIII, and AcIII), were the dominant species in dilute HNO3 (0.05 M). In concentrated HNO3 (16 M), shell-by-shell fitting of the extended X-ray fine structure (EXAFS) data showed the nitrate complexation increased, such that the average stoichiometries of Cm(NO3)4.1±0.7(H2O)5.7±1.3(1.1±0.2)-, Am(NO3)3.4±0.7(H2O)5.4±0.5(0.4±0.1)-, and Ac(NO3)2.3±1.7(H2O)8.3±5.2(0.7±0.5)+ were observed. Data obtained at the intermediate HNO3 concentration (4 M) were modeled as a linear combination of the 0.05 and 16 M spectra. For all three metals, the intermediate models showed larger contributions from the 0.05 M HNO3 spectra than from the 16 M HNO3 spectra. Additionally, these efforts enabled the Cm-NO3 and Ac-NO3 distances to be measured for the first time. Moreover, the AnIII L3-edge EXAFS results, contribute to the growing body of knowledge associated with CmIII, AmIII, and AcIII coordination chemistry, in particular toward advancing understanding of AnIII solution phase speciation.

    View details for DOI 10.1039/c8sc02270d

    View details for PubMedID 30310628

    View details for PubMedCentralID PMC6137438

  • The coordination chemistry of Cm-III, Am-III, and Ac-III in nitrate solutions: an actinide L-3-edge EXAFS study CHEMICAL SCIENCE Ferrier, M. G., Stein, B., Bone, S. E., Cary, S. K., Ditter, A. S., Kozimor, S. A., Lezama Pacheco, J. S., Mocko, V., Seidler, G. T. 2018; 9 (35): 7078–90

    View details for DOI 10.1039/c8sc02270d

    View details for Web of Science ID 000445777400006

  • Redox-Active vs Redox-Innocent: A Comparison of Uranium Complexes Containing Diamine Ligands INORGANIC CHEMISTRY Pattenaude, S. A., Mullane, K. C., Schelter, E. J., Ferriere, M. G., Stein, B. W., Bone, S. E., Pacheco, J., Kozimor, S. A., Fanwick, P. E., Zeller, M., Bart, S. C. 2018; 57 (11): 6530–39


    Uranium complexes (MesDAE)2U(THF) (1-DAE) and Cp2U(MesDAE) (2-DAE) (MesDAE = [ArN-CH2CH2-NAr]; Ar = 2,4,6-trimethylphenyl (Mes)), bearing redox-innocent diamide ligands, have been synthesized and characterized for a full comparison with previously published, redox-active diimine complexes, (MesDABMe)2U(THF) (1-DAB) and Cp2U(MesDABMe) (2-DAB) (MesDABMe = [ArN═C(Me)C(Me)═NAr]; Ar = Mes). These redox-innocent analogues maintain an analogous steric environment to their redox-active ligand counterparts to facilitate a study aimed at determining the differing electronic behavior around the uranium center. Structural analysis by X-ray crystallography showed 1-DAE and 2-DAE have a structural environment very similar to 1-DAB and 2-DAB, respectively. The main difference occurs with coordination of the ene-backbone to the uranium center in the latter species. Electronic absorption spectroscopy reveals these new DAE complexes are nearly identical to each other. X-ray absorption spectroscopy suggests all four species contain +4 uranium ions. The data also indicates that there is an electronic difference between the bis(diamide)-THF uranium complexes as opposed to those that only contain one diamide and two cyclopentadienyl rings. Finally, magnetic measurements reveal that all complexes display temperature-dependent behavior consistent with uranium(IV) ions that do not include ligand radicals. Overall, this study determines that there is no significant bonding difference between the redox-innocent and redox-active ligand frameworks on uranium. Furthermore, there are no data to suggest covalent bonding character using the latter ligand framework on uranium, despite what is known for transition metals.

    View details for PubMedID 29749729

  • Oxidative uranium release from anoxic sediments under diffusion-limited conditions Bone, S., Cahill, M., Jones, M., Fendorf, S., Davis, J., Williams, K., Bargar, J. AMER CHEMICAL SOC. 2018
  • Microbially-mediated metal/radionuclide oxidation coupled to nitrate reduction in an alluvial aquifer Weber, K., Westrop, J., Nolan, J., Bone, S., Bargar, J., Campbell, K., Snow, D. AMER CHEMICAL SOC. 2018
  • Redox Controls over the Stability of U(IV) in Floodplains of the Upper Colorado River Basin ENVIRONMENTAL SCIENCE & TECHNOLOGY Noel, V., Boye, K., Pacheco, J., Bone, S. E., Janot, N., Cardarelli, E., Williams, K. H., Bargar, J. R. 2017; 51 (19): 10954–64


    Aquifers in the Upper Colorado River Basin (UCRB) exhibit persistent uranium (U) groundwater contamination plumes originating from former ore processing operations. Previous observations at Rifle, Colorado, have shown that fine grained, sulfidic, organic-enriched sediments accumulate U in its reduced form, U(IV), which is less mobile than oxidized U(VI). These reduced sediment bodies can subsequently act as secondary sources, releasing U back to the aquifer. There is a need to understand if U(IV) accumulation in reduced sediments is a common process at contaminated sites basin-wide, to constrain accumulated U(IV) speciation, and to define the biogeochemical factors controlling its reactivity. We have investigated U(IV) accumulation in organic-enriched reduced sediments at three UCRB floodplains. Noncrystalline U(IV) is the dominant form of accumulated U, but crystalline U(IV) comprises up to ca. 30% of total U at some locations. Differing susceptibilities of these species to oxidative remobilization can explain this variability. Particle size, organic carbon content, and pore saturation, control the exposure of U(IV) to oxidants, moderating its oxidative release. Further, our data suggest that U(IV) can be mobilized under deeply reducing conditions, which may contribute to maintenance and seasonal variability of U in groundwater plumes in the UCRB.

    View details for PubMedID 28873299

  • Oxidative Uranium Release from Anoxic Sediments under Diffusion-Limited Conditions ENVIRONMENTAL SCIENCE & TECHNOLOGY Bone, S. E., Cahill, M. R., Jones, M. E., Fendorf, S., Davis, J., Williams, K. H., Bargar, J. R. 2017; 51 (19): 11039–47


    Uranium (U) contamination occurs as a result of mining and ore processing; often in alluvial aquifers that contain organic-rich, reduced sediments that accumulate tetravalent U, U(IV). Uranium(IV) is sparingly soluble, but may be mobilized upon exposure to nitrate (NO3-) and oxygen (O2), which become elevated in groundwater due to seasonal fluctuations in the water table. The extent to which oxidative U mobilization can occur depends upon the transport properties of the sediments, the rate of U(IV) oxidation, and the availability of inorganic reductants and organic electron donors that consume oxidants. We investigated the processes governing U release upon exposure of reduced sediments to artificial groundwater containing O2 or NO3- under diffusion-limited conditions. Little U was mobilized during the 85-day reaction, despite rapid diffusion of groundwater within the sediments and the presence of nonuraninite U(IV) species. The production of ferrous iron and sulfide in conjunction with rapid oxidant consumption suggested that the sediments harbored large concentrations of bioavailable organic carbon that fueled anaerobic microbial respiration and stabilized U(IV). Our results suggest that seasonal influxes of O2 and NO3- may cause only localized mobilization of U without leading to export of U from the reducing sediments when ample organic carbon is present.

    View details for PubMedID 28876920

  • Chemical changes in organic matter after fungal colonization in a nitrogen fertilized and unfertilized Norway spruce forest PLANT AND SOIL Nicolas, C., Almeida, J. P., Ellstrom, M., Bahr, A., Bone, S. E., Rosenstock, N. P., Bargar, J. R., Tunlid, A., Persson, P., Wallander, H. 2017; 419 (1-2): 113–26
  • Thermodynamically controlled preservation of organic carbon in floodplains NATURE GEOSCIENCE Boye, K., Noel, V., Tfaily, M. M., Bone, S. E., Williams, K. H., Bargar, J. R., Fendorf, S. 2017; 10 (6): 415-+

    View details for DOI 10.1038/NGEO2940

    View details for Web of Science ID 000402579200009

  • Molecular controls over uranium mobility in complex redox-active sediment systems Bargar, J., Noel, V., Bone, S., Janot, N., Roycroft, S., Boye, K. AMER CHEMICAL SOC. 2017
  • Understanding controls on redox processes in floodplain sediments of the Upper Colorado River Basin. The Science of the total environment Noël, V., Boye, K., Kukkadapu, R. K., Bone, S., Lezama Pacheco, J. S., Cardarelli, E., Janot, N., Fendorf, S., Williams, K. H., Bargar, J. R. 2017


    Floodplains, heavily used for water supplies, housing, agriculture, mining, and industry, are important repositories of organic carbon, nutrients, and metal contaminants. The accumulation and release of these species is often mediated by redox processes. Understanding the physicochemical, hydrological, and biogeochemical controls on the distribution and variability of sediment redox conditions is therefore critical to developing conceptual and numerical models of contaminant transport within floodplains. The Upper Colorado River Basin (UCRB) is impacted by former uranium and vanadium ore processing, resulting in contamination by V, Cr, Mn, As, Se, Mo and U. Previous authors have suggested that sediment redox activity occurring within organic carbon-enriched bodies located below the groundwater level may be regionally important to the maintenance and release of contaminant inventories, particularly uranium. To help assess this hypothesis, vertical distributions of Fe and S redox states and sulfide mineralogy were assessed in sediment cores from three floodplain sites spanning a 250km transect of the central UCRB. The results of this study support the hypothesis that organic-enriched reduced sediments are important zones of biogeochemical activity within UCRB floodplains. We found that the presence of organic carbon, together with pore saturation, are the key requirements for maintaining reducing conditions, which were dominated by sulfate-reduction products. Sediment texture was found to be of secondary importance and to moderate the response of the system to external forcing, such as oxidant diffusion. Consequently, fine-grain sediments are relatively resistant to oxidation in comparison to coarser-grained sediments. Exposure to oxidants consumes precipitated sulfides, with a disproportionate loss of mackinawite (FeS) as compared to the more stable pyrite. The accompanying loss of redox buffering capacity creates the potential for release of sequestered radionuclides and metals. Because of their redox reactivity and stores of metals, C, and N, organic-enriched sediments are likely to be important to nutrient and contaminant mobility within UCRB floodplain aquifers.

    View details for DOI 10.1016/j.scitotenv.2017.01.109

    View details for PubMedID 28359569

  • Uranium(IV) adsorption by natural organic matter in anoxic sediments PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Bone, S. E., Dynes, J. J., Cliff, J., Bargar, J. R. 2017; 114 (4): 711–16


    Uranium is an important carbon-free fuel source and environmental contaminant that accumulates in the tetravalent state, U(IV), in anoxic sediments, such as ore deposits, marine basins, and contaminated aquifers. However, little is known about the speciation of U(IV) in low-temperature geochemical environments, inhibiting the development of a conceptual model of U behavior. Until recently, U(IV) was assumed to exist predominantly as the sparingly soluble mineral uraninite (UO2+x) in anoxic sediments; however, studies now show that this is not often the case. Yet a model of U(IV) speciation in the absence of mineral formation under field-relevant conditions has not yet been developed. Uranium(IV) speciation controls its reactivity, particularly its susceptibility to oxidative mobilization, impacting its distribution and toxicity. Here we show adsorption to organic carbon and organic carbon-coated clays dominate U(IV) speciation in an organic-rich natural substrate under field-relevant conditions. Whereas previous research assumed that U(IV) speciation is dictated by the mode of reduction (i.e., whether reduction is mediated by microbes or by inorganic reductants), our results demonstrate that mineral formation can be diminished in favor of adsorption, regardless of reduction pathway. Projections of U transport and bioavailability, and thus its threat to human and ecosystem health, must consider U(IV) adsorption to organic matter within the sediment environment.

    View details for DOI 10.1073/pnas.1611918114

    View details for Web of Science ID 000392597000045

    View details for PubMedID 28069941

    View details for PubMedCentralID PMC5278482

  • Regional importance of organic-rich sediments to uranium mobility in the upper Colorado River Basin Noel, V., Boye, K., Bargar, J., Lefebvre, P., Maher, K., Bone, S., Lezama, J., Carderelli, E., Dam, W., Johnson, R. AMER CHEMICAL SOC. 2016
  • Impact of redox conditions on interfacial uranium chemistry in complex natural sediments Bargar, J., Bone, S., Lezama-Pacheco, J., Alessi, D., Cerrato, J., Veeramani, H., Noel, V., Suvorova, E., Bernier-Latmani, R., Giammar, D., Long, P., Williams, K. AMER CHEMICAL SOC. 2016
  • Persistent Secondary Contaminant Sources at a Former Uranium Mill Site, Riverton, Wyoming, USA Johnson, R. H., Dam, W. L., Campbell, S., Noel, V., Bone, S. E., Bargar, J. R., Dayvault, J., Drebenstedt, C., Paul, M. TU BERGAKADEMIE FREIBERG, INST MINING & SPECIAL CIVIL ENG. 2016: 398–404
  • Probing the sorption reactivity of the edge surfaces in birnessite nanoparticles using nickel(II) GEOCHIMICA ET COSMOCHIMICA ACTA Simanova, A. A., Kwon, K. D., Bone, S. E., Bargar, J. R., Refson, K., Sposito, G., Pena, J. 2015; 164: 191-204
  • Influence of natural organic matter on uranium mobility in the upper Colorado River Basin Bargar, J., Janot, N., Pham, D., Jones, M., Bone, S., Lezama-Pacheco, J., Fendorf, S., Williams, K., Long, P. AMER CHEMICAL SOC. 2015
  • Mackinawite (FeS) Reduces Mercury(II) under Sulfidic Conditions ENVIRONMENTAL SCIENCE & TECHNOLOGY Bone, S. E., Bargar, J. R., Sposito, G. 2014; 48 (18): 10681–89


    Mercury (Hg) is a toxicant of global concern that accumulates in organisms as methyl Hg. The production of methyl Hg by anaerobic bacteria may be limited in anoxic sediments by the sequestration of divalent Hg [Hg(II)] into a solid phase or by the formation of elemental Hg [Hg(0)]. We tested the hypothesis that nanocrystalline mackinawite (tetragonal FeS), which is abundant in sediments where Hg is methylated, both sorbs and reduces Hg(II). Mackinawite suspensions were equilibrated with dissolved Hg(II) in batch reactors. Examination of the solid phase using Hg LIII-edge extended X-ray absorption fine structure (EXAFS) spectroscopy showed that Hg(II) was indeed reduced in FeS suspensions. Measurement of purgeable Hg using cold vapor atomic fluorescence spectrometry (CVAFS) from FeS suspensions and control solutions corroborated the production of Hg(0) that was observed spectroscopically. However, a fraction of the Hg(II) initially added to the suspensions remained in the divalent state, likely in the form of β-HgS-like clusters associated with the FeS surface or as a mixture of β-HgS and surface-associated species. Complexation by dissolved S(-II) in anoxic sediments hinders Hg(0) formation, but, by contrast, Hg(II)-S(-II) species are reduced in the presence of mackinawite, producing Hg(0) after only 1 h of reaction time. The results of our work support the idea that Hg(0) accounts for a significant fraction of the total Hg in wetland and estuarine sediments.

    View details for DOI 10.1021/es501514r

    View details for Web of Science ID 000341801500020

    View details for PubMedID 25180562

    View details for PubMedCentralID PMC4167055

  • Hg reduction under sulfidic conditions by the nanocrystalline iron sulfide mackinawite Bone, S., Kwon, K., Bargar, J., Sposito, G. AMER CHEMICAL SOC. 2012
  • Mechanisms of mercury sequestration by the iron sulfide mineral mackinawite Bone, S., Sposito, G., Bargar, J. AMER CHEMICAL SOC. 2010