Cm(III) sorption onto γ-Al2O3: New insight into sorption mechanisms by time-resolved laser fluorescence spectroscopy and extended X-ray absorption fine structure
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Thomas Rabung
Sorption of trivalent Cm onto γ-Al2O3 is investigated by time-resolved laser fluorescence spectroscopy (TRLFS). The pH dependent sorption of Cm(III) is followed at constant ionic strength of 0.1 M NaClO4 under argon atmosphere in the pH range between 3.5 and 13.2 at a total Cm(III) concentration of 2.5×10-7 mol/L. Three different surface-sorbed Cm(III) species appearing at different pH are identified by their emission spectra with peak maxima at 600.6 nm, 602.5 nm, and 605.7 nm using an excitation wavelength of λex=396.6 nm. No variation of the emission decay is observed for the three sorbed species (constant lifetimes of 110 μs). The pH dependent species distribution obtained from peak deconvolution of emission spectra is in agreement with earlier Eu/Cm sorption studies and sorbed species are assigned to >Al−O−Cm(OH)x(2-x)(H2O)5-x inner-sphere complexes. Indirect Cm excitation via energy transfer from the solid to the metal ion at λex=355 nm yields emission bands significantly shifted compared to spectra obtained at λex=396.6 nm. We interpret this observation as a hint for the existence of Cm inner-sphere complexes bound to different γ-Al2O3 surface sites. The exact nature of those species is presently not known, but they likely involve Cm interaction with Al(OH)3 phases at the solid surface which may even dominate the solid surface chemistry. Complementary EXAFS measurements are performed with Lu and Gd, taken as chemical homologues of the trivalent actinides. EXAFS for Gd/Lu(III) sorbed onto γ-Al2O3 at pH=6 identifies a single oxygen coordination shell with a high degree of disorder. For Gd this shell consists of 9±1.5 atoms at a 2.45±0.02 Å distance. A coordination number of 7±1.5 and a Lu−O distance of 2.28±0.02 Å is found in the Lu-samples. Those values are quite close to what is known for the respective aquo ions. The large asymmetry in the coordination shell, however, suggests inner-sphere complexation. This is in agreement with TRLFS results showing clearly the existence of inner-sphere surface complexes where the first coordination shell of the trivalent metal ions consists of 5H2O/OH- entities. Together with EXAFS data, a metal ion coordination to four oxygen atoms belonging to the γ-alumina surface is concluded. Both spectroscopic studies indicate a certain variability of surface binding sites for trivalent metal ions.
© Oldenbourg Wissenschaftsverlag
Artikel in diesem Heft
- Preface Migration 2005
- Solubility measurement of zirconium(IV) hydrous oxide
- Solubility of ThO2·xH2O(am) and the formation of ternary Th(IV) hydroxide-carbonate complexes in NaHCO3-Na2CO3 solutions containing 0−4 M NaCl
- Ion interaction (SIT) coefficients for the Th4+ ion and trace activity coefficients in NaClO4, NaNO3 and NaCl solution determined by solvent extraction with TBP
- Leaching of neptunium from garnet- and murataite-based ceramics
- Coprecipitation of thorium and lanthanum with UO2+x(s) as host phase
- Rare Earth element (REE) incorporation in natural calcite: Upper limits for actinide uptake in a secondary phase
- Protonation of D-gluconate and its complexation with Np(V) in acidic to nearly neutral solutions
- Complexing properties of α-isosaccharinate: thorium
- Determination of the thermodynamic quantities of complexation between Eu(III) and carboxylic acids by microcalorimetry
- Potentiometric investigations on the interaction of humic acid with Cu(II) and Eu(III) ions
- Investigation of complexation of thorium by humic acid using chemically immobilized humic acid on silica gel
- Correlation between X-ray chemical shift and partial charge in Tc(IV) complexes: Determination of Tc partial charge in TcnOy(4n-2y)+
- Oxidation and dissolution rates of UO2(s) in carbonate-rich solutions under external alpha irradiation and initially reducing conditions
- On the stability of Pu(III) at different pH under non-inert conditions
- Reduction behavior of uranium in the presence of citric acid
- Leaching of zirconolite ceramics under H+ and He2+ irradiation
- Reduction of plutonium(VI) in brine under subsurface conditions
- Theoretical first step towards an understanding of the uranyl ion sorption on the rutile TiO2(110) face: A DFT periodic and cluster study
- Cm(III) sorption onto γ-Al2O3: New insight into sorption mechanisms by time-resolved laser fluorescence spectroscopy and extended X-ray absorption fine structure
- Modelling sorption data for the actinides Am(III), Np(V) and Pa(V) on montmorillonite
- Sorption of Cs, Ni, Pb, Eu(III), Am(III), Cm, Ac(III), Tc(IV), Th, Zr, and U(IV) on MX 80 bentonite: An experimental approach to assess model uncertainty
- The uptake of radium by calcium silicate hydrates and hardened cement paste
- Np(V)O2+ sorption on hydroxyapatite-effect of calcium and phosphate anions
- Uranium(VI) interaction with pyrite (FeS2): Chemical and spectroscopic studies
- Interaction of U(VI) with pyrite, galena and their mixtures: a theoretical and multitechnique approach
- Technetium sorption by stibnite from natural water
- Mechanisms of cesium sorption onto magnetite
- Sorption of cesium on granite under aerobic and anaerobic conditions
- Comparative study of cesium sorption on crushed and intact sedimentary rock
- The INE-Beamline for actinide research at ANKA
- Evaluation of the reversibility of iodide uptake by argillaceous rocks by the radial diffusion method
- Thermal diffusion of chlorine in uranium dioxide
- Effects of ionic strength on the coordination of Eu(III) and Cm(III) to a Gram-negative bacterium, Paracoccus denitrificans
- Interaction mechanisms of bacterial strains isolated from extreme habitats with uranium
- Biotransformation of plutonium complexed with citric acid
- Iodination of humic acid samples from different origins
- The fate of the epsilon phase (Mo-Ru-Pd-Tc-Rh) in the UO2 of the Oklo natural fission reactors
- Rhenium migration at the Maqarin natural analogue site (Jordan)
- Classic adsorption isotherms incorporated in modern surface complexation models: Implications for sorption of actinides
- Use of thermodynamic sorption models to derive radionuclide Kd values for performance assessment: selected results and recommendations of the NEA sorption project
- Modeling spent nuclear fuel alteration and radionuclide migration in disposal conditions
Artikel in diesem Heft
- Preface Migration 2005
- Solubility measurement of zirconium(IV) hydrous oxide
- Solubility of ThO2·xH2O(am) and the formation of ternary Th(IV) hydroxide-carbonate complexes in NaHCO3-Na2CO3 solutions containing 0−4 M NaCl
- Ion interaction (SIT) coefficients for the Th4+ ion and trace activity coefficients in NaClO4, NaNO3 and NaCl solution determined by solvent extraction with TBP
- Leaching of neptunium from garnet- and murataite-based ceramics
- Coprecipitation of thorium and lanthanum with UO2+x(s) as host phase
- Rare Earth element (REE) incorporation in natural calcite: Upper limits for actinide uptake in a secondary phase
- Protonation of D-gluconate and its complexation with Np(V) in acidic to nearly neutral solutions
- Complexing properties of α-isosaccharinate: thorium
- Determination of the thermodynamic quantities of complexation between Eu(III) and carboxylic acids by microcalorimetry
- Potentiometric investigations on the interaction of humic acid with Cu(II) and Eu(III) ions
- Investigation of complexation of thorium by humic acid using chemically immobilized humic acid on silica gel
- Correlation between X-ray chemical shift and partial charge in Tc(IV) complexes: Determination of Tc partial charge in TcnOy(4n-2y)+
- Oxidation and dissolution rates of UO2(s) in carbonate-rich solutions under external alpha irradiation and initially reducing conditions
- On the stability of Pu(III) at different pH under non-inert conditions
- Reduction behavior of uranium in the presence of citric acid
- Leaching of zirconolite ceramics under H+ and He2+ irradiation
- Reduction of plutonium(VI) in brine under subsurface conditions
- Theoretical first step towards an understanding of the uranyl ion sorption on the rutile TiO2(110) face: A DFT periodic and cluster study
- Cm(III) sorption onto γ-Al2O3: New insight into sorption mechanisms by time-resolved laser fluorescence spectroscopy and extended X-ray absorption fine structure
- Modelling sorption data for the actinides Am(III), Np(V) and Pa(V) on montmorillonite
- Sorption of Cs, Ni, Pb, Eu(III), Am(III), Cm, Ac(III), Tc(IV), Th, Zr, and U(IV) on MX 80 bentonite: An experimental approach to assess model uncertainty
- The uptake of radium by calcium silicate hydrates and hardened cement paste
- Np(V)O2+ sorption on hydroxyapatite-effect of calcium and phosphate anions
- Uranium(VI) interaction with pyrite (FeS2): Chemical and spectroscopic studies
- Interaction of U(VI) with pyrite, galena and their mixtures: a theoretical and multitechnique approach
- Technetium sorption by stibnite from natural water
- Mechanisms of cesium sorption onto magnetite
- Sorption of cesium on granite under aerobic and anaerobic conditions
- Comparative study of cesium sorption on crushed and intact sedimentary rock
- The INE-Beamline for actinide research at ANKA
- Evaluation of the reversibility of iodide uptake by argillaceous rocks by the radial diffusion method
- Thermal diffusion of chlorine in uranium dioxide
- Effects of ionic strength on the coordination of Eu(III) and Cm(III) to a Gram-negative bacterium, Paracoccus denitrificans
- Interaction mechanisms of bacterial strains isolated from extreme habitats with uranium
- Biotransformation of plutonium complexed with citric acid
- Iodination of humic acid samples from different origins
- The fate of the epsilon phase (Mo-Ru-Pd-Tc-Rh) in the UO2 of the Oklo natural fission reactors
- Rhenium migration at the Maqarin natural analogue site (Jordan)
- Classic adsorption isotherms incorporated in modern surface complexation models: Implications for sorption of actinides
- Use of thermodynamic sorption models to derive radionuclide Kd values for performance assessment: selected results and recommendations of the NEA sorption project
- Modeling spent nuclear fuel alteration and radionuclide migration in disposal conditions
