[en] The Am(III) adsorption isotherms on natural hematite, on a red earth and on three kinds of treated red earth samples were determined and compared. The treatment was performed to remove iron oxides, organic matter (OM) and both. The batch technique and aqueous Am(III) solutions with molarities less than 3 x 10^-9 mol/l were used. A very high adsorbability of Am(III) on hematite was found, and in order to decrease the adsorption percentage, stable Eu³⁺ as a hold back carrier was added to the aqueous solution. All the isotherms were found to be linear. The strong effects of pH, ionic strength and fulvic acid (FA) on the Am(III) adsorption on natural hematite were demonstrated. A positive contribution of OM and an unexpectedly high negative influence of iron oxides on the Am(III) adsorption by the untreated red earth were found too. The average distribution coefficients of Am(III) adsorption on natural hematite, on red earth and on three kinds of treated red earth samples were determined, respectively, from these linear isotherms. The very high adsorbability of Am(III) on hematite and the very strong negative influence of iron oxides on the Am(III) adsorption on untreated red earth were distinctly demonstrated as well. It appears that the adsorbability of composed natural materials cannot be predicted from the adsorbabilities of each of the mineral components alone, due to possible interactions between the mineral components and the different characteristics of the composite. (author)

No abstract available

[en] The actinides are chemical poisons and radiological hazards. One challenge to better appraise their toxicity and develop countermeasures in case of exposure of living organisms is to better assess pathways of contamination. Because of the high chemical affinity of those actinide elements for phosphate groups and the ubiquity of such chemical functions in biochemistry, nucleotides and in particular adenosine triphosphate nucleotide (ATP) may be considered critical target building blocks for actinides. Combinations of spectroscopic techniques (Fourier transformed Infra Red [FTIR], Electro-spray Ionization Mass Spectrometry [ESI-MS], and Extended X-ray Absorption Fine Structure [EXAFS]) with quantum chemical calculations have been implemented in order to assess the actinides coordination arrangement with ATP. We describe and compare herein the interaction of ATP with thorium and americium; thorium(IV) as a representative of actinide(IV) like plutonium(IV) and americium(III) as a representative of all heavier actinides. In the case of thorium, an insoluble complex is readily formed. In the case of americium, a behavior identical to that described previously for lutetium has been observed with insoluble and soluble complexes. The comparative study of ATP complexation with Th(IV) and Am(III) shows their ability to form insoluble complexes for which a structural model has been proposed by analogy with previously described Lu(III) complexes. (authors)

[en] The formation constants of thiocyanate complexes of Eu(III) and Am(III) in trace concentrations were investigated in mixed solvent (CH₃OH+H₂O) solutions of different ionic strength. Furthermore, in paper electrophoresis, the moving velocities of the species of Eu(III) and Am(III) were investigated in 1.1M (H, Na)(SCN, ClO₄) mixed solvent (CH₃OH+H₂O) solutions. The results showed that the difference between the velocities of Eu(III) and Am(III) is explained by the difference of the mean charges calculated by the formation constants of thiocyanate complexes of Eu(III) and Am(III) in the solution. (author)

[en] With the aid of the earlier suggested criterion of separating ability of complexing systems it has been shown that efficiency of the complexing agents decreases in the series: OH^- > ethylenediaminetetramethylphosphonic acid > β-hydroxyethyliminodiacetic acid > ethylenediamino-bis-isopropylphosphonic acid > 1,2-cyclohexanediaminetetraacetic acid > ethylenediaminetetraacetic acid > ethylenediaminetetraacetic acid, nitriletriacetic acid. The optimum conditions have been found for separating system by electromigration. The relationship is considered between the criteria of separating ability and selectivity of the complexing agents

No abstract available

[en] The fate of radionuclides in the environment is a cause of great concern for modern society, seen especially in 2011 after the Fukushima accident. Among the environmental compartments, seawater covers most of the earth's surface and may be directly or indirectly impacted. The interaction between radionuclides and the marine compartment is therefore essential for better understanding the transfer mechanisms from the hydrosphere to the biosphere. This information allows for the evaluation of the impact on humans via our interaction with the biotope that has been largely undocumented up to now. In this report, we attempt to make a link between the speciation of heavy elements in natural seawater and their uptake by a model marine organism. More specifically, because the interaction of actinides with marine invertebrates has been poorly studied, the accumulation in a representative member of the Mediterranean coralligenous habitat, the sponge Aplysina cavernicola, was investigated and its uptake curve exposed to a radiotracer ²⁴¹Am was estimated using a high-purity Ge gamma spectrometer. But in order to go beyond the phenomenological accumulation rate, the speciation of americium(III) in seawater must be assessed. The speciation of ²⁴¹Am (and natural europium as its chemically stable surrogate) in seawater was determined using a combination of different techniques: Time-Resolved Laser-Induced Fluorescence (TRLIF), Extended X-ray Absorption Fine Structure (EXAFS) at the LIII edge, Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy and Scanning Electron Microscopy (SEM) and the resulting data were compared with the speciation modeling. In seawater, the americium(III) complex (as well as the corresponding europium complex, although with conformational differences) was identified as a ternary sodium bis carbonato complex, whose formula can be tentatively written as NaAm(CO₃)₂.nH₂O. It is therefore this chemical form of americium that is accumulated by the sponge A. cavernicola. (authors)

[en] In order to study the volatility of the dipivaloylmethanato complexes of Cf in tracer scale, the authors used either Sc or La as a carrier for the preparation of these transplutonium complexes. The syntheses of Am(dpm)₃ and Cf(dmp)₃ could be proved by isolating them in carrier free state by applying sublimatographical separation and comparing the deposition zone with those of other lanthanoide dipivaloylmethanato complexes. The detection of these tracer amounts of actinoide elements was made either by solid state track detectors for alpha particles or fission fragment, or by alpha ray spectrometry. (Auth.)

[en] Thermodynamics and structural data were assessed in solution for the same chemical conditions to finally describe the speciation of the Am(III)-citrate system. A focus was done on the role played by the hydroxyl group: does it coordinate the actinide? Is it protonated? To better understand its role, the Am-citrate system was compared to the Am-tricarballylate system (analogue to citric acid without the hydroxyl group). The two systems were studied at pH = 1 and 3. The complexation constants have been determined and, different complexes were characterized using X-ray absorption, NMR, TRLFS and capillary electrophoresis.

[en] The rates of formation and dissociation of AmDCTA^- (DCTA=trans 1,2 diaminocyclohexanetetraacetate) were measured respectively by stopped-flow and conventional spectrophotometric methods. A mechanism is proposed which involves coordination of Am(III) to three acetate groups of H/sub n/(DCTA)/sup n-4/ to form the relatively long-lived intermediate AmHDCTA which subsequently loses the proton. The slow step of the formation reaction is postulated to be associated with the formation of an americium-donor nitrogen bond