Unraveling the Np(V) sorption on ZrO: A batch, spectroscopic and modeling combined approach.

The interactions of the long-lived actinide neptunium with the corrosion product zirconia (ZrO) have to be considered in the safety assessment of a repository for radioactive waste. The sorption of Np(V) on ZrO was investigated in the absence of carbonate at the macroscopic and molecular scale. At the macroscopic level, the Np(V) uptake was independent of ionic strength and the isoelectric point of the pristine zirconia was increased, both suggesting the presence of inner-sphere Np(V) surface complexes.

Europium(III) Meets Etidronic Acid (HEDP): A Coordination Study Combining Spectroscopic, Spectrometric, and Quantum Chemical Methods.

Etidronic acid (1-Hydroxyethylidene-1,1-diphosphonic acid, HEDP, HL) is a proposed decorporation agent for U(VI). This paper studied its complex formation with Eu(III), an inactive analog of trivalent actinides, over a wide pH range, at varying metal-to-ligand ratios (M:L) and total concentrations. Combining spectroscopic, spectrometric, and quantum chemical methods, five distinct Eu(III)-HEDP complexes were found, four of which were characterized.

Thermodynamic and structural aspects of the aqueous uranium(iv) system - hydrolysis vs. sulfate complexation.

The aquatic species of U(iv) in acidic aqueous solution in the presence of sulfate were studied in the micromolar range by a combined approach of optical spectroscopy (UV/vis and mid-IR), quantum-chemical calculations (QCC), and thermodynamic modelling. The number of species occurring in solution within the pH range 0-2 was assessed by decomposition and fitting of photometric spectra using HypSpec and Geochemist's Workbench software. Single component spectra of U, UOH, USO and U(SO) were obtained and extinction coefficients ε were calculated to be 61.

Interdisciplinary Round-Robin Test on Molecular Spectroscopy of the U(VI) Acetate System.

A comprehensive molecular analysis of a simple aqueous complexing system-U(VI) acetate-selected to be independently investigated by various spectroscopic (vibrational, luminescence, X-ray absorption, and nuclear magnetic resonance spectroscopy) and quantum chemical methods was achieved by an international round-robin test (RRT). Twenty laboratories from six different countries with a focus on actinide or geochemical research participated and contributed to this scientific endeavor. The outcomes of this RRT were considered on two levels of complexity: first, within each technical discipline, conformities as well as discrepancies of the results and their sources were evaluated.

Recovery of gallium from wafer fabrication industry wastewaters by Desferrioxamine B and E using reversed-phase chromatography approach.

Gallium (Ga) is a critical element in developing renewable energy generation and energy efficient systems. The supply of Ga is at risk and needed recycling technologies for its availability in future. This study demonstrated the recovery of Ga from low gallium concentrated wafer fabrication industry wastewaters using the siderophores desferrioxamine B (DFOB) and desferrioxamine E (DFOE).

Thermodynamic and Structural Studies on the Ln(III)/An(III) Malate Complexation.

The complexation of the trivalent lanthanides Nd(III) and Eu(III) and of the actinide Am(III) with malate was studied using a multi-method approach. The combination of structural and thermodynamic studies was required for the interpretation of the stoichiometry and thermodynamic data (log β, Δ H, Δ S, Δ G) of the lanthanide/actinide malate complexes leading to a profound molecular understanding of the system. The structure-sensitive methods vibrational spectroscopy and extended X-ray absorption fine structure spectroscopy complemented with quantum-mechanical ab initio molecular dynamics calculations revealed a tridentate ring structure of the respective metal complexes.

Removal and recovery of uranium(VI) by waste digested activated sludge in fed-batch stirred tank reactor.

This study demonstrated the removal and recovery of uranium(VI) in a fed-batch stirred tank reactor (STR) using waste digested activated sludge (WDAS). The batch adsorption experiments showed that WDAS can adsorb 200 (±9.0) mg of uranium(VI) per g of WDAS.

Comparative analysis of uranium bioassociation with halophilic bacteria and archaea.

Rock salt represents a potential host rock formation for the final disposal of radioactive waste. The interactions between indigenous microorganisms and radionuclides, e.g.

Selenium(IV) Sorption Onto γ-AlO: A Consistent Description of the Surface Speciation by Spectroscopy and Thermodynamic Modeling.

The sorption processes of Se(IV) onto γ-AlO were studied by in situ Infrared spectroscopy, batch sorption studies, zeta potential measurements and surface complexation modeling (SCM) in the pH range from 5 to 10. In situ attenuated total reflection fourier-transform infrared (ATR FT-IR) spectroscopy revealed the predominant formation of a single inner-sphere surface species at the alumina surface, supporting previously reported EXAFS results, irrespective of the presence or absence of atmospherically derived carbonate. The adsorption of Se(IV) decreased with increasing pH, and no impact of the ionic strength was observed in the range from 0.

Enzymatic activity of the CaM-PDE1 system upon addition of actinyl ions.

The threat of a dirty bomb which could cause internal contamination has been of major concern for the past decades. Because of their high chemical toxicity and their presence in the nuclear fuel cycle, uranium and neptunium are two actinides of high interest. Calmodulin (CaM) which is a ubiquitous protein present in all eukaryotic cells and is involved in calcium-dependent signaling pathways has a known affinity for uranyl and neptunyl ions.

Multistage bioassociation of uranium onto an extremely halophilic archaeon revealed by a unique combination of spectroscopic and microscopic techniques.

The interactions of two extremely halophilic archaea with uranium were investigated at high ionic strength as a function of time, pH and uranium concentration. Halobacterium noricense DSM-15987 and Halobacterium sp. putatively noricense, isolated from the Waste Isolation Pilot Plant repository, were used for these investigations.

The Sorption Processes of U(VI) onto SiO in the Presence of Phosphate: from Binary Surface Species to Precipitation.

The ternary system containing aqueous U(VI), aqueous phosphate and solid SiO was comprehensively investigated using a batch sorption technique, in situ attenuated total reflection Fourier-transform infrared (ATR FT-IR) spectroscopy, time-resolved luminescence spectroscopy (TRLS), and surface complexation modeling (SCM). The batch sorption studies on silica gel (10 g/L) in the pH range 2.5 to 5 showed no significant increase in U(VI) uptake in the presence of phosphate at equimolar concentration of 20 μM, but significant increase in U(VI) uptake was observed for higher phosphate concentrations.

In situ spectroscopic identification of neptunium(V) inner-sphere complexes on the hematite-water interface.

Hematite plays a decisive role in regulating the mobility of contaminants in rocks and soils. The Np(V) reactions at the hematite-water interface were comprehensively investigated by a combined approach of in situ vibrational spectroscopy, X-ray absorption spectroscopy and surface complexation modeling. A variety of sorption parameters such as Np(V) concentration, pH, ionic strength, and the presence of bicarbonate was considered.

Extracellular polymeric substances govern the surface charge of biogenic elemental selenium nanoparticles.

The origin of the organic layer covering colloidal biogenic elemental selenium nanoparticles (BioSeNPs) is not known, particularly in the case when they are synthesized by complex microbial communities. This study investigated the presence of extracellular polymeric substances (EPS) on BioSeNPs. The role of EPS in capping the extracellularly available BioSeNPs was also examined.

Spectroscopic identification of binary and ternary surface complexes of Np(V) on gibbsite.

For the first time, detailed molecular information on the Np(V) sorption species on amorphous Al(OH)3 and crystalline gibbsite was obtained by in situ time-resolved Attenuated Total Reflection Fourier-Transform Infrared (ATR FT-IR) and Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy. The results consistently demonstrate the formation of mononuclear inner sphere complexes of the NpO2(+) ion irrespective of the prevailing atmospheric condition. The impact of the presence of atmospheric equivalent added carbonate on the speciation in solution and on the surfaces becomes evident from vibrational data.

Formic acid interaction with the uranyl(VI) ion: structural and photochemical characterization.

Complex formation between the uranyl(VI) ion and formic acid was studied by infrared absorption (IR) and X-ray absorption (EXAFS) spectroscopy as well as density functional theory (DFT) calculations. In contrast to the acetate ion which forms exclusively a bidentate complex with uranyl(VI), the formate ion binds to uranyl(VI) in a unidentate fashion. The photochemistry of the uranyl(VI)-formic acid system was explored by DFT calculations and photoreduction of uranyl(VI) in the presence of formic acid was found to occur via an intermolecular process, that is, hydrogen abstraction from hydrogenformate by the photo-excited uranyl(VI).

Structural characterization of the aqueous dimeric uranium(VI) species: (UO2)2CO3(OH)3-.

A combined theoretical and spectroscopic approach was used to refine structural data of the aqueous dimeric U(VI) species, (UO2)2CO3(OH)3(-). Several isomer structures of this complex were already derived from previous X-ray absorption and NMR experiments (Szabó, Z. et al.

Aqueous uranium(VI) complexes with acetic and succinic acid: speciation and structure revisited.

We employed density functional theory (DFT) calculations, and ultraviolet-visible (UV-vis), extended X-ray absorption fine-structure (EXAFS), and attenuated total reflection Fourier-transform infrared (IR) spectroscopy analyzed with iterative transformation factor analysis (ITFA) to determine the structures and the pH-speciation of aqueous acetate (ac) and succinate (suc) U(VI) complexes. In the acetate system, all spectroscopies confirm the thermodynamically predicted pH-speciation by Ahrland (1951), with the hydrated uranyl ion and a 1:1, a 1:2 and a 1:3 U(VI)-ac complex. In the succinate system, we identified a new 1:3 U(VI)-suc complex, in addition to the previously known 1:1 and 1:2 U(VI)-suc complexes, and determined the pH-speciation for all complexes.

Curium(III) citrate speciation in biological systems: a europium(III) assisted spectroscopic and quantum chemical study.

Citrate complexes are the dominant binding form of trivalent actinides and lanthanides in human urine at pH < 6. Hence, an accurate prediction of the speciation of these elements in the presence of citrate is crucial for the understanding of their impact on the metabolism of the human organism and the corresponding health risks. We studied the complexation of Cm(III) and Eu(III), as representatives of trivalent actinides and lanthanides, respectively, in aqueous citrate solution over a wide pH range using time-resolved laser-induced fluorescence spectroscopy.

Structural study on 2,2'-(methylimino)bis(N,N-dioctylacetamide) complex with Re(VII)O4- and Tc(VII)O4- by 1H NMR, EXAFS, and IR spectroscopy.

The structures of the complex of 2,2'-(methylimino)bis(N,N-dioctylacetamide) (MIDOA) with M(VII)O(4)(-) (M = Re and Tc), which were prepared by liquid-liquid solvent extraction, were investigated by using (1)H nuclear magnetic resonance (NMR), extended X-ray absorption fine structure (EXAFS), and infrared (IR) spectroscopy. The (1)H NMR spectra of the complex of MIDOA with Re(VII)O(4)(-) prepared in the organic solution suggest the transfer of a proton from aqueous to organic solution and the formation of the H(+)MIDOA ion. The EXAFS spectra of the complexes of H(+)MIDOA with Re(VII)O(4)(-) and Tc(VII)O(4)(-) show only the M-O coordination of the aquo complexes, suggesting that the chemical state of M(VII)O(4)(-) was unchanged during the extraction process.

The complexation of uranium(VI) and atmospherically derived CO2 at the ferrihydrite-water interface probed by time-resolved vibrational spectroscopy.

The sorption reactions of uranium(VI) at the ferrihydrite(Fh)-water interface were investigated in the absence and presence of atmospherically derived CO(2) by time-resolved in situ vibrational spectroscopy. The spectra clearly show that a single uranyl surface species, most probably a mononuclear bidentate surface complex, is formed irrespective of the presence of atmospherically derived CO(2). The character of the carbonate surface species correlates with the presence of the actinyl ions and changes from a monodentate to a bidentate binding upon sorption of U(VI).

Coordination of uranium(VI) with functional groups of bacterial lipopolysaccharide studied by EXAFS and FT-IR spectroscopy.

The complexation of uranyl ions with lipopolysaccharide (LPS), the main component of the cell wall of Gram-negative bacteria, was investigated on a molecular level with U L(III)-edge extended X-ray absorption fine structure (EXAFS) and attenuated total reflection Fourier transform infrared (ATR-FT-IR) spectroscopy over a wide pH range (2.6 to 7.0).

Uranium sorption on various forms of titanium dioxide--influence of surface area, surface charge, and impurities.

Titanium dioxide (TiO(2)) has often served as a model substrate for experimental sorption studies of environmental contaminants. However, various forms of Ti-oxide have been used, and the different sorption properties of these materials have not been thoroughly studied. We investigated uranium sorption on some thoroughly characterized TiO(2) surfaces with particular attention to the influence of surface area, surface charge, and impurities.

Complexation of U(VI) with highly phosphorylated protein, phosvitin A vibrational spectroscopic approach.

The complexation of uranium(VI) to variant functional groups of the highly phosphorylated protein phosvitin in aqueous solution was investigated by attenuated total reflection Fourier transform infrared (ATR FT-IR) spectroscopy. For the verification of the affinity of the actinyl ions to carboxyl and phosphate groups of the amino acid side chains, samples with different phosphate to uranium(VI) (P/U) ratios were investigated under denaturing conditions as well as in aqueous medium. From a comparative study with other heavy metal ions, i.

Sorption of Np(V) onto TiO2, SiO2, and ZnO: an in situ ATR FT-IR spectroscopic study.

The migration of hazardous neptunium is strongly affected by sorption processes at the solid-water interface. Up to now, almost no spectroscopic data are available to characterize Np(V) species on a molecular level. For the first time, at a micromolar concentration level the Np(V) speciation in aqueous solution and the sorption of Np(V) onto metal oxides were studied using NIR and in situ attenuated total reflection Fourier-transform infrared (ATR FT-IR) spectroscopy.