ABSTRACT We describe here the formulation of a new synergistic extractant system for the extracti... more ABSTRACT We describe here the formulation of a new synergistic extractant system for the extraction of rare earth elements from aqueous phosphoric acid solution containing large quantities of impurities currently found in urban mines and secondary deposits. This new synergistic system is original in its concept as it contains the association of the bifunctional extractant amido-phosphonate, known for its high efficiency in the recovery of uranium from phosphate rocks, with the(Bis(2-ethylhexyl) sulfosuccinate sodium) (AOT) surfactant molecule known to form reverse micelles in aliphatic diluents. The mixture was found to extract synergistically rare earth elements with high distribution coefficients (D), and exhibits a high separation factor (S.F.) toward iron (III) from phosphoric acid solution. A complete thermodynamic study of its extraction properties is also presented, showing this system has the ability to extract Rare Earth Elements (REEs) from a wide range of phosphoric acid concentrations, which is often the case in industrial processes.
In situalpha radiolysis andex situgamma radiolysis of monoamide extractant: proposition of a degr... more In situalpha radiolysis andex situgamma radiolysis of monoamide extractant: proposition of a degradation scheme.
Abstract The redox potential of the Ce(IV)/Ce(III) DOTA is determined to be 0.65 V versus SCE, po... more Abstract The redox potential of the Ce(IV)/Ce(III) DOTA is determined to be 0.65 V versus SCE, pointing out a stabilization of ~13 orders of magnitude for the Ce(IV)DOTA complex, as compared to Ce(IV)aq. The Ce(III)DOTA after electrochemical oxidation yields a Ce(IV)DOTA complex with a t1/2 ~3 h and which is suggested to retain the “in cage” geometry. Chemical oxidation of Ce(III)DOTA by diperoxosulfate renders a similar Ce(IV)DOTA complex with the same t1/2. From the electrochemical measurements, one calculates logK (Ce(IV)DOTA2−) ~ 35.9. Surprisingly, when Ce(IV)DOTA is obtained by mixing Ce(IV)aq with DOTA, a different species is obtained with a 2 : 1(M : L) stoichiometry. This new complex, Ce(IV)DOTACe(IV), shows redox and spectroscopic features which are different from the electrochemically prepared Ce(IV)DOTA. When one uses thiosulfate as a reducing agent of Ce(IV)DOTACe(IV), one gets a prolonged lifetime of the latter. The reductant seems to serve primarily as a coordinating ligand with a geometry which does not facilitate inner sphere electron transfer. The reduction process rate in this case could be dictated by an outer sphere electron transfer or DOTA exchange by S2O32−. Both Ce(IV)DOTA and Ce(IV)DOTACe(IV) have similar kinetic stability and presumably decompose via decarboxylation of the polyaminocarboxylate ligand.
HAL (Le Centre pour la Communication Scientifique Directe), Jun 5, 2016
International audienceIn nuclear fuel reprocessing, the organic ligands in solution are subjected... more International audienceIn nuclear fuel reprocessing, the organic ligands in solution are subjected to radiolysis. The resulting effects of radiolysis can lead to modifications of the solution composition. These changes can alter the extraction properties of the ligands, specifically, their extraction efficiency and selectivity. Therefore, it is important to study the effect of radiolysis on the speciation of the complexes in solution to identify the weak points in the molecular structure of the ligands. This identification can facilitate the design of more stable molecules and of molecules that generate innocuous degradation products. The aim of this work is to increase the understanding of ligand behavior when exposed to ionizing radiation. The dialkyl monoamide class of extractants has been chosen for this study. The formation of simple carboxylic acids as well as amine degradation products of some dialkyl monoamides have been characterized by potentiometry, FTIR and/or GC-MS [1]. While these techniques are useful in identifying the main families or lower molecular weight products, electrospray ionization mass spectrometry is a powerful technique that can be used to identify products through both charge and mass characterization. This is especially useful when trying to determine complex formation between degradation products and metal ions. This work aims to characterize the degradation products formed as a result of alpha radiolysis of monoamide extractants involved in plutonium complexes by electrospray ionization mass spectrometry. In addition to in-situ alpha irradiation, non-complexed extractants have been irradiated by a gamma source allowing direct comparisons to be made between the type of irradiation and the resulting degradation products that form. To investigate the effect of the structure on the stability of the ligand, in particular, the effect of the alkyl group on the carbonyl function, three extractants were chosen, N, N-di-(2-ethylhexyl)butryamide (DEHBA), N, N-di-(2-ethyhexyl)isobutyramide (DEHiBA), and N, N-di-(2-ethylhexyl)-3, 3-methylbutyramide (DEHDMBA)
ABSTRACT In order to understand the mechanisms involved in the extraction processes developed to ... more ABSTRACT In order to understand the mechanisms involved in the extraction processes developed to separate minor actinides, the "ligand/metallic cation" complexes formed in the organic phases are characterized by electrospray ionization-mass-spectrometry (ESI-MS). This paper deals with the application of the ESI-MS technique to analyze americium complexes in organic solutions. Two extractant systems are investigated : 1/ organic solutions of nitrogen polydentate extractants such as 6,6'-bis(5,6-dialkyl-1,2,4-triazin-3-yl)-2,2'-bipyridines (BTBPs) and 2/ organic solutions composed of mixture of a malonamide and a dialkylphosphoric acid.
ABSTRACT We describe here the formulation of a new synergistic extractant system for the extracti... more ABSTRACT We describe here the formulation of a new synergistic extractant system for the extraction of rare earth elements from aqueous phosphoric acid solution containing large quantities of impurities currently found in urban mines and secondary deposits. This new synergistic system is original in its concept as it contains the association of the bifunctional extractant amido-phosphonate, known for its high efficiency in the recovery of uranium from phosphate rocks, with the(Bis(2-ethylhexyl) sulfosuccinate sodium) (AOT) surfactant molecule known to form reverse micelles in aliphatic diluents. The mixture was found to extract synergistically rare earth elements with high distribution coefficients (D), and exhibits a high separation factor (S.F.) toward iron (III) from phosphoric acid solution. A complete thermodynamic study of its extraction properties is also presented, showing this system has the ability to extract Rare Earth Elements (REEs) from a wide range of phosphoric acid concentrations, which is often the case in industrial processes.
In situalpha radiolysis andex situgamma radiolysis of monoamide extractant: proposition of a degr... more In situalpha radiolysis andex situgamma radiolysis of monoamide extractant: proposition of a degradation scheme.
Abstract The redox potential of the Ce(IV)/Ce(III) DOTA is determined to be 0.65 V versus SCE, po... more Abstract The redox potential of the Ce(IV)/Ce(III) DOTA is determined to be 0.65 V versus SCE, pointing out a stabilization of ~13 orders of magnitude for the Ce(IV)DOTA complex, as compared to Ce(IV)aq. The Ce(III)DOTA after electrochemical oxidation yields a Ce(IV)DOTA complex with a t1/2 ~3 h and which is suggested to retain the “in cage” geometry. Chemical oxidation of Ce(III)DOTA by diperoxosulfate renders a similar Ce(IV)DOTA complex with the same t1/2. From the electrochemical measurements, one calculates logK (Ce(IV)DOTA2−) ~ 35.9. Surprisingly, when Ce(IV)DOTA is obtained by mixing Ce(IV)aq with DOTA, a different species is obtained with a 2 : 1(M : L) stoichiometry. This new complex, Ce(IV)DOTACe(IV), shows redox and spectroscopic features which are different from the electrochemically prepared Ce(IV)DOTA. When one uses thiosulfate as a reducing agent of Ce(IV)DOTACe(IV), one gets a prolonged lifetime of the latter. The reductant seems to serve primarily as a coordinating ligand with a geometry which does not facilitate inner sphere electron transfer. The reduction process rate in this case could be dictated by an outer sphere electron transfer or DOTA exchange by S2O32−. Both Ce(IV)DOTA and Ce(IV)DOTACe(IV) have similar kinetic stability and presumably decompose via decarboxylation of the polyaminocarboxylate ligand.
HAL (Le Centre pour la Communication Scientifique Directe), Jun 5, 2016
International audienceIn nuclear fuel reprocessing, the organic ligands in solution are subjected... more International audienceIn nuclear fuel reprocessing, the organic ligands in solution are subjected to radiolysis. The resulting effects of radiolysis can lead to modifications of the solution composition. These changes can alter the extraction properties of the ligands, specifically, their extraction efficiency and selectivity. Therefore, it is important to study the effect of radiolysis on the speciation of the complexes in solution to identify the weak points in the molecular structure of the ligands. This identification can facilitate the design of more stable molecules and of molecules that generate innocuous degradation products. The aim of this work is to increase the understanding of ligand behavior when exposed to ionizing radiation. The dialkyl monoamide class of extractants has been chosen for this study. The formation of simple carboxylic acids as well as amine degradation products of some dialkyl monoamides have been characterized by potentiometry, FTIR and/or GC-MS [1]. While these techniques are useful in identifying the main families or lower molecular weight products, electrospray ionization mass spectrometry is a powerful technique that can be used to identify products through both charge and mass characterization. This is especially useful when trying to determine complex formation between degradation products and metal ions. This work aims to characterize the degradation products formed as a result of alpha radiolysis of monoamide extractants involved in plutonium complexes by electrospray ionization mass spectrometry. In addition to in-situ alpha irradiation, non-complexed extractants have been irradiated by a gamma source allowing direct comparisons to be made between the type of irradiation and the resulting degradation products that form. To investigate the effect of the structure on the stability of the ligand, in particular, the effect of the alkyl group on the carbonyl function, three extractants were chosen, N, N-di-(2-ethylhexyl)butryamide (DEHBA), N, N-di-(2-ethyhexyl)isobutyramide (DEHiBA), and N, N-di-(2-ethylhexyl)-3, 3-methylbutyramide (DEHDMBA)
ABSTRACT In order to understand the mechanisms involved in the extraction processes developed to ... more ABSTRACT In order to understand the mechanisms involved in the extraction processes developed to separate minor actinides, the "ligand/metallic cation" complexes formed in the organic phases are characterized by electrospray ionization-mass-spectrometry (ESI-MS). This paper deals with the application of the ESI-MS technique to analyze americium complexes in organic solutions. Two extractant systems are investigated : 1/ organic solutions of nitrogen polydentate extractants such as 6,6'-bis(5,6-dialkyl-1,2,4-triazin-3-yl)-2,2'-bipyridines (BTBPs) and 2/ organic solutions composed of mixture of a malonamide and a dialkylphosphoric acid.
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Papers by Laurence Berthon