Modelisation thermodynamique et cinetique de la formation des bauxites et des cuirasses ferrugineuses

Available from INIST (FR), Document Supply Service, under shelf-number : TD 83469 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc

Les Radionucléides dans l'environnement. Enjeux sociétaux et défis scientifiques.

https://new.societechimiquedefrance.fr/numero/n460-461-mars-avril-2021/International audienceLes recherches sur le comportement des radionucléides naturels et artificiels (RN) dans l'environnement visent à évaluer, prévoir ou réduire leurs transferts et effets dans les milieux naturels (en lien avec leur spéciation), et recoupent des enjeux sociétaux : sureté des futurs sites de stockage des déchets radioactifs, gestion de sites à radioactivité naturelle renforcée. Dans ce contexte, la communauté académique se positionne sur la recherche amont autour de grandes questions (base de données sur la chimie des RN en solution et aux interfaces, évaluation des effets des faibles doses, procédés de remédiation) et de questions transverses (modélisation, instrumentation de pointe). Des défis pour le futur sont de développer des études multi-échelles et interdisciplinaires, ce qui est illustré dans cet article par des études du devenir des RN sur le site d'une ancienne mine d'uranium (Rophin, Puy-de-Dôme) et du rôle des matières organiques naturelles. Mots-clés Radionucléides, environnement, spéciation, effets, interdisciplinarité

Chemical fractionation of a terrestrial humic acid upon sorption on alumina by high resolution mass spectrometry

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Trace Level Uranyl Complexation with Phenylphosphonic Acid in Aqueous Solution: Direct Speciation by High Resolution Mass Spectrometry

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Les Radionucléides dans l'environnement. Enjeux sociétaux et défis scientifiques.

https://new.societechimiquedefrance.fr/numero/n460-461-mars-avril-2021/International audienceLes recherches sur le comportement des radionucléides naturels et artificiels (RN) dans l'environnement visent à évaluer, prévoir ou réduire leurs transferts et effets dans les milieux naturels (en lien avec leur spéciation), et recoupent des enjeux sociétaux : sureté des futurs sites de stockage des déchets radioactifs, gestion de sites à radioactivité naturelle renforcée. Dans ce contexte, la communauté académique se positionne sur la recherche amont autour de grandes questions (base de données sur la chimie des RN en solution et aux interfaces, évaluation des effets des faibles doses, procédés de remédiation) et de questions transverses (modélisation, instrumentation de pointe). Des défis pour le futur sont de développer des études multi-échelles et interdisciplinaires, ce qui est illustré dans cet article par des études du devenir des RN sur le site d'une ancienne mine d'uranium (Rophin, Puy-de-Dôme) et du rôle des matières organiques naturelles. Mots-clés Radionucléides, environnement, spéciation, effets, interdisciplinarité

Molecular Level Description of the Sorptive Fractionation of a Fulvic Acid on Aluminum Oxide Using Electrospray Ionization Fourier Transform Mass Spectrometry

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Effect of mineral surface properties (alumina, kaolinite) on the sorptive fractionation mechanisms of soil fulvic acids: Molecular-scale ESI-MS studies

International audienceWe addressed the effects of mineral surface properties (kaolinite versus Al-oxide) on the sorption-driven fractionation of asoil fulvic acid (FA) at acidic pH, mainly by means of ESI(-)-FTMS analysis of initial and supernatant solutions of FA sorptionbatch experiments. The MS data provided clear molecular-scale evidence of distinct mechanisms and molecular parameterscontrolling the FA fractionation upon its sorption on clay and oxide surfaces, respectively.Identification of sorbing and not-sorbing FA compounds in kaolinite-solution systems revealed a weak fractionationamong members of ACO2 series of aliphatics or not-condensed aromatics (NCAs) at pH 3.8, and almost no sorption ofpoorly-oxygenated polycyclic aromatic compounds (PACs) and NCAs. This first molecular-scale description of a FA fractionationin a clay-solution system suggests that H-bonding with low affinity sites (aluminol/silanol) on the basal planes ofthe clay particles is the main mechanism of sorption. Due to the predominance of such weak and poorly-selective mechanism,the sorption of aliphatic and NCA molecules bearing oxygenated functionalities was prevented at pH 5, due to dissolved Alcompeting successfully for their coordination.In contrast, a strong FA fractionation was observed onto alumina, with a preferential retention of PACs and highlyoxygenatedaliphatics and NCAs. The major part of the poorly oxygenated aliphatics was left in solution. The sorption degreeof NCAs and aliphatics was strongly correlated with molecular acidity. For PACs and poorly-oxygenated NCAs, the sorptionwas driven by reactions of surface ligand exchange (for the most oxygenated compounds) or by hydrophobic interactions (forthe least oxygenated compounds)

Molecular fractionation of a soil fulvic acid (FA) and competitive sorption of trace metals (Cu, Zn, Cd, Pb) in hematite–solution systems: effect of the FA-to-mineral ratio

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Surface precipitation at the Al2O3 / uranyl phosphate solution interface. Goldschmidt Abstracts 2010 – D. pp 221.

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Trace Level Uranyl Complexation with Phenylphosphonic Acid in Aqueous Solution: Direct Speciation by High Resolution Mass Spectrometry

The complexation of U­(VI) by organic P-containing ligands in humic substances (HS) is an important issue of uranyl mobility in soil. We have investigated the complexation of uranyl by a model ligand for aromatic phosphorus functionalities in HS, phenylphosphonic acid, by using ultrahigh resolution electrospray ionization-mass spectrometry (ESI-MS). The high sensitivity permitted to investigate the complexation of trace level uranyl and to explore directly in the native aqueous solutions the nature of the uranyl-phenylphosphonate complexes. Positive identification of the complexes coexisting in solutions with low pH and varying ligand-to-metal ratio was achieved thanks to the high resolving power, high mass accuracy, and reliability of ion abundance of the technique. The positively charged and neutral uranyl species were detected simultaneously on negative ion mass spectra, evidencing formation of three types of U­(VI)-phenylphosphonate complexes. Two complexes with a metal-to-ligand stoichiometry of 1:1 (in the monoprotonated and nonprotonated forms) existed in solutions at pH 3–5, and a 1:2 complex was additionally formed at relatively high ligand-to-metal ratio. A strategy based on the use of uranyl-phosphate solution complexes as internal standards was developed to determine from the ESI­(-)­MS results the stability constants of the complexes, which were calculated to be log <i>K</i>₁₁₁ = 3.4 ± 0.2 for UO₂(HPhPO₃)⁺, log <i>K</i>₁₀₁ = 7.1 ± 0.1 for UO₂PhPO₃, and log <i>K</i>₁₁₂ = 7.2 ± 0.2 for UO₂(HPhPO₃)₂. The speciation model presented here suggests that organic P existing at low concentration in HS is involved significantly in binding by humic and fulvic acids of trace level uranyl in soil