A5049206261- Radioactive element chemistry and processing
- Mercury impact and mitigation studies
- Heavy metals in environment
- Geochemistry and Elemental Analysis
- Mine drainage and remediation techniques
- Iron oxide chemistry and applications
- Metal Extraction and Bioleaching
- Heavy Metal Exposure and Toxicity
- Electron and X-Ray Spectroscopy Techniques
- Clay minerals and soil interactions
- Plant Micronutrient Interactions and Effects
- Catalytic Processes in Materials Science
- Adsorption and biosorption for pollutant removal
- Radioactive contamination and transfer
- Advanced Electron Microscopy Techniques and Applications
- Zeolite Catalysis and Synthesis
- Electrocatalysts for Energy Conversion
- Groundwater flow and contamination studies
- Geological and Geochemical Analysis
- Nuclear Physics and Applications
- Graphene research and applications
- Nanomaterials for catalytic reactions
- Electrochemical Analysis and Applications
- CO2 Sequestration and Geologic Interactions
- Analytical chemistry methods development
Illinois Institute of Technology
2014-2024
University of Leeds
2017-2022
Argonne National Laboratory
2010-2018
University of Notre Dame
2005-2010
Princeton University
2008-2009
Indian Institute of Technology Kharagpur
2009
Brookhaven National Laboratory
2008
Microbial reduction of ferric iron [Fe(III)] is an important biogeochemical process in anoxic aquifers. Depending on groundwater pH, dissimilatory metal-reducing bacteria can also respire alternative electron acceptors to survive, including elemental sulfur (S(0)). To understand the interplay Fe/S cycling under alkaline conditions, we combined thermodynamic geochemical modeling with bioreactor experiments using Shewanella oneidensis MR-1. Under these S. enzymatically reduce S(0) but not...
Uranium (U) poses a significant contamination hazard to soils, sediments, and groundwater due its extensive use for energy production. Despite advances in modeling the risks of this toxic radioactive element, lack information about mechanisms controlling U transport hinders further improvements, particularly reducing environments where UIV predominates. Here we establish that mineral surfaces can stabilize majority as adsorbed species following reduction UVI. Using X-ray absorption...
Hydrothermal carbonisation (HTC) has been demonstrated to be a sustainable thermochemical process, capable of producing functionalised carbon materials for wide range applications. In order better apply such materials, the local chemistry and reaction pathways governing hydrothermal growth must understood. We report use scanning transmission X-ray microscopy (STXM) observe chemical changes in functionality between interface bulk regions HTC. Spatially-resolved, element-specific...
Abstract Atomically dispersed transition metal‐nitrogen‐carbon catalysts are emerging as low‐cost electrocatalysts for the oxygen reduction reaction in fuel cells. However, a cost‐effective and scalable synthesis strategy these is still required, well greater understanding of their mechanisms. Herein, iron, nitrogen co‐doped carbon spheres (Fe@NCS) have been prepared via hydrothermal carbonization high‐temperature post carbonization. It determined that FeN 4 main form iron existing obtained...
This article investigates a facile one-pot method for the synthesis of Fe and Ag core/shell nanoparticles by aqueous reduction under ambient conditions. We have shown that injection time silver nitrate into reaction vessel containing ferrous salt, sodium borohydride, citrate is vital parameter precise control desired structure. For example, if injected one minute after borohydride added to vessel, will nucleate first followed Fe, creating monodisperse Ag/Fe nanoparticles. In contrast,...
Abiotic reduction of inorganic mercury by natural organic matter and native soils is well-known, recently there evidence that reduced iron (Fe) species, such as magnetite, green rust, Fe sulfides, can also reduce Hg(II). Here, we evaluated the Hg(II) magnetites with varying Fe(II) content in both absence presence chloride. Specifically, whether magnetite stoichiometry (x = Fe(II)/Fe(III)) influences rate formation products. In chloride, to Hg(0) observed over a range stoichiometries (0.29 <...
Magnetite and green rust have been shown to reduce aqueous Hg(II) Hg(0). In this study, we tested the ability of magnetite sorbed 2 g · L(-1) biomass (Bacillus subtilis), at high (50 μM) low (5 Hg loadings pH 6.5 5.0. At Hg:biomass loading, where binding is predominantly through carboxyl functional groups, L(III)-edge X-ray absorption spectroscopy showed reduction Hg(0) by magnetite. Reduction occurred within h d 5.0, respectively. binds via sulfhydryl was not reduced or 5.0 after months...
The conversion of inorganic mercury (Hg(II)) to methylmercury (MeHg) is central the understanding Hg toxicity in environment. methylation occurs cytosol certain obligate anaerobic bacteria and archaea possessing hgcAB gene cluster. However, processes involved Hg(II) biouptake are not well understood. Here, we examined role cell surface thiols, cellular ligands with highest affinity for that located at interface between outer membrane external medium, on sorption by Geobacter sulfurreducens....
We report studies of bimetallic nanoparticles with 15%–16% atomic crystal parameters size mismatch. The degree alloying was probed in a 2-nm Pt core (smallest attainable size) Pt–Ag (completely immiscible bulk) and 20-nm-diameter Pd–Ag nanowires miscible bulk). Particles were synthesized radiolytically, depending on the initial parameters, they assume spherical or cylindrical (nanowire) morphologies. In all cases, metals are seen to follow their bulk characteristics. Ag segregate both wire...
Despite being thermodynamically less stable, small ferrous colloids (60 nm to 3 μm in diameter) remain an important component of the biogeochemical cycle at Earth's surface, yet their composition and structure reasons for persistence are still poorly understood. Here we use X-ray-based Fe L-edge carbon K-edge spectromicroscopy address speciation organic–mineral associations ferrous, ferric, Fe-poor particles collected from sampling sites both marine freshwater environments. We show that...
The biological reduction of uranium from soluble U(VI) to insoluble U(IV) has shown potential prevent migration in groundwater. To gain insight into the extent that can occur during biostimulation and what degree reoxidation will under field relevant conditions after is terminated, X-ray absorption near edge structure (XANES) spectroscopy was used monitor: (1) speciation situ a flowing column while active occurring; (2) postbiostimulation stability when exposed incoming oxic water. Results...
Abstract Analyses of sulphur isotope compositions in sedimentary pyrites from the Vindhyan, Chattisgarh and Cuddapah basins show heavy δ 34 S (> +25 ‰) values during Mesoproterozoic. The data provide evidence support a hypothesized global Proterozoic sulphidic anoxic ocean where very low concentrations marine sulphate, bacterially reduced closed systems, produced similar to or even heavier than sulphate. extreme environmental conditions induced by these oceans could have been responsible...
Sorption-desorption experiments show that the majority (ca. 80-90%) of U(VI) presorbed to mesoporous and nanoporous alumina could not be released by extended (2 week) extraction with 50 mM NaHCO(3) in contrast non-nanoporous α alumina. The extent reduction aluminum oxides was semiquantitatively estimated comparing percentages uranium desorbed anoxic sodium bicarbonate between AH(2)DS-reacted unreacted control samples. X-ray absorption spectroscopy confirmed rapidly completely reduced...
Abstract. Mercury (Hg) bioavailability and geochemical cycling is affected by its partitioning between the aqueous particulate phases. We applied a synchrotron-based X-ray fluorescence (XRF) microprobe to visualize quantify directly spatial localization of Hg correlations with other elements interest on suspended particles from Hg-contaminated freshwater system. Up 175 μg g−1 found particles, but less than 0.01% in form methylmercury. heterogeneously distributed among phytoplankton (e.g.,...
Abstract Aberration‐corrected (AC) STEM, AC TEM and in situ X‐ray absorption fine structure spectroscopy (XAFS) were used to characterize the Pt clusters present on a 0.35 wt % γ‐alumina support after reduction hydrogen at 700 °C. STEM high‐angle annular dark field imaging shows that cluster formation takes place temperatures up approximately 350 °C, this is followed by gradual growth size for heat treatments The data show °C are narrow distribution centered 0.88 nm, using method involving...
Heavy metal accumulation in edible plants grown contaminated soils poses a major environmental risk to humans and grazing animals.This study focused on the concentration speciation of Zn different with smelter wastes (Spelter, WV, USA) containing high levels metals Zn, Cu, Pb, Cd.Their was examined parts (roots, stem, leaves) as function growth stage (dry seed, sprouting cotyledon, root vegetables radish, leafy vegetable spinach legume clover.Although varied significantly plant species,...