A5053924711- Radioactive element chemistry and processing
- Nuclear Materials and Properties
- Chemical Synthesis and Characterization
- Nuclear materials and radiation effects
- Radioactive contamination and transfer
- Rare-earth and actinide compounds
- Crystallization and Solubility Studies
- Extraction and Separation Processes
- Nuclear Physics and Applications
- Nuclear reactor physics and engineering
- Chemical and Physical Properties in Aqueous Solutions
- Advanced Materials Characterization Techniques
- Molten salt chemistry and electrochemical processes
- X-ray Diffraction in Crystallography
- Nuclear and radioactivity studies
- Advanced Chemical Sensor Technologies
- Fusion materials and technologies
- Geological and Geochemical Analysis
- Layered Double Hydroxides Synthesis and Applications
- X-ray Spectroscopy and Fluorescence Analysis
- Analytical chemistry methods development
- Geochemistry and Geologic Mapping
- Metallurgical Processes and Thermodynamics
- Metal Extraction and Bioleaching
- Environmental Toxicology and Ecotoxicology
Karlsruhe Institute of Technology
2015-2025
Joint Research Centre
2011-2013
Abstract One of the long standing debates in actinide chemistry is level localization and participation 5 f valence orbitals covalent bonds across series. Here we illuminate role uranium, neptunium plutonium chemical bonding using advanced spectroscopies: M 4,5 HR-XANES 3 d 4 RIXS. Results reveal that are active for uranium neptunium, shown by significant variations their evidenced spectra. In contrast, appear localized surprisingly insensitive to different environments. We envisage this...
Due to their redox reactivity, surface sorption characteristics, and ubiquity as corrosion products or minerals in natural sediments, iron(II)-bearing control a large extent the environmental fate of actinides. Pu-LIII-edge XANES EXAFS spectra were used investigate reaction aqueous 242Pu(III) 242Pu(V) reacted with magnetite, mackinawite, chukanovite under anoxic conditions. As Pu concentrations liquid phase rapidly below detection limit, oxidation state local structure determined for...
Abstract Redox behaviour of Tc(VII)/Tc(IV) was investigated in 0.1 M NaCl solutions containing different reducing agents the pH range 2 to 13 at 22 ºC under inert Ar atmosphere. In several samples, 1 × 10 5 mol/dm 3 (M) initially added TcO 4 - reduced form a Tc(IV) oxide solid phase with low solubility. The observed Tc redox transformation processes are systematized according E h -pH conditions solution, indicating that borderline for reduction Tc(VII) Tc(IV), + 3e 4H ⇔TcO · x H O(coll, hyd)...
In actinide chemistry, the formal number of open‐shell 5f electrons, n(open), is a well‐defined quantity with an integer value. The effective occupation, n(f), additionally takes donation and back‐donation into account, generally has non‐integer value, varying numerical definitions. present study explores important distinction between n(f) n(open) in chemistry example PuO2, by using electronic structure methods relativistic Hamiltonian combination experimental Pu M5‐edge high energy...
The actinides possess a complex electronic structure, making their chemical and physical properties among the least understood in periodic table. Advanced spectroscopic tools, able to obtain deep insights into structure binding of actinides, are highly desirable. Here, we introduce two sensitive tools: one determines number localized 5f electrons on an actinide atom, another assesses covalent character actinide-ligand bonding. Both tools based multiplet present M4 edge core-to-core resonant...
In actinide chemistry, the formal number of open‐shell 5f electrons, n(open), is a well‐defined quantity with an integer value. The effective occupation, n(f), additionally takes donation and back‐donation into account, generally has non‐integer value, varying numerical definitions. present study explores important distinction between n(f) n(open) in chemistry example PuO2, by using electronic structure methods relativistic Hamiltonian combination experimental Pu M5‐edge high energy...
Abstract The aqueous chemistry of Np(V) in alkaline 0.01 to 5.5 M CaCl 2 solutions at T = 23 ± ℃ was thoroughly studied by long-term batch solubility experiments from both over- and undersaturation. Applying a comprehensive set experimental spectroscopic techniques including Vis/NIR Np L3-edge EXAFS, the controlling solid phases predominant species were identified. results demonstrate that behavior differs completely one reported for NaCl NaClO 4 solutions: as limiting phases, three so far...
Pu L3 HR-XANES and FEFF9 computations provide evidence for band-like 6d states in colloidal contrasting to narrow molecular Pu(iv). is valuable bond length estimation plutonyl, whereas M5 an advanced tool analysing redox 5f unoccupied density of states.
Abstract The solubility and redox behavior of hydrous Pu(IV) oxide was comprehensively investigated by an experimental multi-method approach as a function different conditions in 0.1 M NaCl solutions, allowing detailed characterization Pu(III) solid phase stability these systems. Samples were prepared at ~3≤pH m ≤~6 (pH =–log <m:math xmlns:m="http://www.w3.org/1998/Math/MathML"> <m:mrow> <m:msub> <m:mtext>m</m:mtext> <m:msup> <m:mtext>H</m:mtext> <m:mtext>+</m:mtext> </m:msup> </m:mrow>...
For more than 120 years, systematic studies of X-ray interaction with matter have been the basis for our understanding materials—both natural or man-made origin—and their structure-function relationships. Beginning simple radiographic imaging at end 19th century, based analytical tools such as diffraction, fluorescence and photoemission absorption techniques are indispensable in almost any field chemical material sciences—including basic applied actinide radionuclide studies. The advent...
Abstract The solubility of Np(V) was investigated at T =22±2°C in alkaline NaCl solutions different ionic strength (0.1–5.0 M). solid phases controlling the –log 10 m H +(pH ) and concentration were characterized by XRD, quantitative chemical analysis, SEM–EDS XAFS (both XANES EXAFS). Aqueous equilibrium with solids for selected samples within 8.9≤pH ≤10.3 UV-vis/NIR absorption spectroscopy. In 0.1 M NaCl, experimental initial greenish NpO 2 OH(am) phase is good agreement previous results...
Neptunium(V) and uranium(VI) are precipitated from an aqueous potassium–sodium-containing carbonate-rich solution, the solid phases investigated. U/Np M4,5-edge high-energy resolution X-ray absorption near edge structure (HR-XANES) spectroscopy Np 3d4f resonant inelastic scattering (3d4f RIXS) applied in combination with thermodynamic calculations, L3-edge XANES, extended fine (EXAFS) studies to analyze local atomic coordination oxidation states of uranium neptunium. The XANES/HR-XANES...
Pu(III), Pu(IV), and a higher oxidation state of Pu, likely Pu(VI), are for the first time characterized simultaneously present in borosilicate glass using Pu M5 edge high energy resolution X-ray absorption near structure (HR-XANES) technique. We illustrate that method can be very efficiently used to determine states, which control solubility limit matrix. HR-XANES results show addition excess Si3N4 is not sufficient complete reduction has relatively (9–22 wt % Pu) due its network-modifying...
Abstract The results of comprehensive solubility experiments with Np(V) in dilute to concentrated CaCl 2 solutions which included the spectroscopic investigation predominant aqueous species and thorough analysis controlling solid phases [1](Fellhauer, D., Rothe, J., Altmaier, M., Neck, V., Runke, Wiss, T., Fanghänel, Th., solubility, speciation phase formation alkaline solutions. Part I: Experimental (Radiochim. Acta, DOI 10.1515/ract-2015-2489), following referred as “Part I”), showed that...
Abstract The solubility of Np(IV) and Pu(IV) hydrous oxides was studied at 22±2 °C under reducing conditions in alkaline CaCl 2 solutions. Redox were adjusted either with mM Na S O 4 or additions iron powder. In 2.0 4.5 M pH c =11–12, the neptunium plutonium concentrations increase a slope +4 (log[An] vs . ) as expected for formation complex Ca [An(OH) 8 ] 4+ recently identified Th(IV). At ≤1.0 this effect is negligible both Pu(IV). conditional equilibrium constants log * K s,(4,1,8)...
The solubility of Np(VI) was investigated in carbonate-free NaCl solutions (0.1 M &le; I 5.0 M) at T = 22 &plusmn; 2 &deg;C to derive thermodynamic properties aqueous species and solid compounds formed under alkaline conditions. experimentally derived curves can be divided into four main regions: (I) ~7 pH m ~9, showing a steep decrease Np with slope (log [Np] vs. ) &ndash;3 or &ndash;2 (depending on concentration); (II) ~9 ~10.5, nearly pH-independent [Np]; (III) ~10.5...
The reliable prediction of possible plutonium migration into the geological environment is crucial for safety assessment radioactive waste repositories. Fe(II)-bearing corrosion products like magnetite, which form on surface steel containers, can effectively contribute to retardation potential radionuclide release by sorption and redox reactions, eventually followed formation secondary precipitates. A process even more efficient—especially when considering required long time scales nuclear...
Combined advanced spectroscopy and solubility studies provide evidence for the formation of novel calcium-containing hydrolyzed (Cm,Pu)( iii )–EDTA complex(es).
Thermodynamic description of complex sulfate systems relevance for nuclear waste disposal. Pitzer and SIT models including aqueous complexes derived the Eu( iii )–Mg/Na–SO 4 –H 2 O system based on solubility experiments TRLFS measurements.