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Microparticles play a role in cardiovascular disease pathology. The flavanol-like epicatechin is increasingly considered due to its cardioprotective effects. The aim of this study was to investigate the impact of epicatechin on microparticle generation, phenotype and procoagulant properties. Plasma samples from 15 healthy subjects were incubated with increasing concentrations of epicatechin (1 to 100 μM). Then, the expression of glycoprotein IIb, phosphatidylserine (PS), glycoprotein Ib (GPIb) and P-selectin was assessed by flow cytometry analysis after (or not) platelet stimulation. Microparticle procoagulant activity was determined using ZymuphenTM MP and ZymuphenTM MP-TF for phospholipid and tissue factor content, and with thrombin generation (TG) assays for procoagulant function. Platelet microparticles that express GPIb (/µL) decreased from 20,743 ± 24,985 (vehicle) to 14,939 ± 14,333 (p = 0.6), 21,366 ± 16,949 (p = 0.9) and 15,425 ± 9953 (p < 0.05) in samples incubated with 1, 10 and 100 µM epicatechin, respectively. Microparticle concentration (nM PS) decreased from 5.6 ± 2.0 (vehicle) to 5.1 ± 2.2 (p = 0.5), 4.5 ± 1.5 (p < 0.05) and 4.7 ± 2.0 (p < 0.05) in samples incubated with 1, 10 and 100µM epicatechin, respectively. Epicatechin had no impact on tissue factor-positive microparticle concentration. Epicatechin decreased TG (endogenous thrombin potential, nM.min) from 586 ± 302 to 509 ± 226 (p = 0.3), 512 ± 270 (p = 0.3) and 445 ± 283 (p < 0.05). These findings indicate that epicatechin affects microparticle release, phenotype and procoagulant properties.

The molecular organization of N,N'-dimethyl-N,N'-dioctylhexylethoxymalonamide (DMDOHEMA), the current reference extractant for the DIAMEX (DIAMide EXtraction) process, is correlated with its water extraction properties from neutral media. The aggregation of DMDOHEMA in n-heptane was investigated by vapor pressure osmometry (VPO) and the aggregate speciation characterized by combined small-angle neutron and X-ray scattering (SANS and SAXS, respectively). Two approaches were taken to model the aggregation of the diamide and the water extraction as a function of the diamide concentration by taking into account a single aggregation equilibrium with an average aggregation number N equal to 4.28 ± 0.05; and a competition between two types of aggregates in the organic phase, namely, aggregates of the reverse micelle type with 4 diamides per aggregate, and an oligomeric structure composed of about 10 diamide molecules which appears at high extractant concentration (>1 mol/L). In both cases, the supramolecular speciation representing the monomers/aggregates distribution was determined, and for each supramolecular organization, a solubilization parameter was calculated using the Sergievskii-Dannus relationship. Thus, the correlation between the two types of micellization of the diamide and the extraction of water into the organic phase was demonstrated. The larger aggregates can extract about five times more water than monomers. [ABSTRACT FROM AUTHOR]

A thermodynamic model that allows one to determine the number and the stoichiometry of the complexes formed between nitric acid, neodymium nitrate (Nd(NO3 ) 3), and octyl(phenyl)-N,N-diisobutylcarbamoylmethyl phosphine oxide (CMPO) diluted in nitrophenylhexyl ether (NPHE) also called 1-(hexyloxy)-2- nitrobenzene, is presented in this work. The Mikulin-Sergievskii-Dannus' model was used to model the extraction at 25°C of the HNO3-H2O-NPHE, HNO3-H2O-CMPO 0.2 mol kg-1-NPHE, Nd(NO3)3-H3O-CMPO 0.2 mol kg-1-NPHE and Nd(NO3)3-HNO3-H2O-CMPO 0.2 mol kg-1-NPHE systems. The stoichiometric mean activity coefficients of components in the binary aqueous phases were determined by interpolation from the experimental data published in the literature. For mixtures, they were calculated from experimental data using the Mikulin's equation, whereas the activity coefficients of the species in the organic phase were calculated from the Sergievskii-Dannus' equation. A satisfactory description of the distribution of neodymium nitrate, nitric acid, and water was then obtained over a wide range of neodymium and nitric acid concentrations in the aqueous phase by taking into account the formation of the following complexes: (HNO3)(NPHE), (HNO3)(H2O)(NPHE), (HNO3)(H2O(CMPO)2, (HNO3)(CMPO) (HNO3)2(CMPO), (HNO3)3(CMPO) (Nd(NO3)3(CMPO)3 (1 : 3), (Nd(NO3)3(CMPO)2 (1 : 2) (Nd(NO3)3(CMPO) (1 : 1), (Nd(NO3)3(CMPO)3 (1 : 1 : 3), (Nd(NO3)3(HNO3(CMPO)2 (1 : 1 : 2) and (Nd(NO3)3)(HNO3)(CMPO) (1 : 1 : 1). [ABSTRACT FROM AUTHOR]

A thermodynamic model that allows one to determine the number and the stoichiometry of the complexes formed between trivalent lanthanide(Ln) nitrates—Pr(NO3)3, Nd(NO3)3, Sm(NO3)3, Eu(NO3)3, Gd(NO3)3, and Yb(NO3)3—and octyl(phenyl)-N,N-diisobutylcarbamoylmethyl phosphine oxide(CMPO) diluted in nitrophenylhexyl ether(NPHE) is presented in this work. The Mikulin–Sergievskii–Dannus'model was used to model the extraction at 25°C of the Ln(NO3)3–H2O–CMPO 0.2 mol kg−1–NPHE system with or without a salting-out agent. The stoichiometric mean activity coefficients of components in the aqueous phase were calculated from experimental data using the Mikulin's equation, whereas the activity coefficients of the species in the organic phase were calculated from the Sergievskii–Dannus'equation. A satisfactory description of the distribution of lanthanide nitrate and water was then obtained over a wide range of lanthanide concentration in the aqueous phase by taking into account the formation of the following complexes:[Ln(NO3)3](CMPO)3(1:3),[Ln(NO3)3](CMPO)2(1:2), and[Ln(NO3)3](CMPO)(1:1). [ABSTRACT FROM AUTHOR]

Extraction mechanisms of two bifunctional extractants which differ only by the grafting of an alkyl chain between their two functions were investigated at molecular and supramolecular scales to investigate the origin of their very different separation factors toward uranium and zirconium. Investigation of the complex structure with spectroscopic analysis (Fourier Transform Infra-Red (FTIR), ElectroSpray Ionization Mass Spectroscopy (ESI-MS) and Extended X-Ray Absorption Fine Structure (EXAFS)) demonstrated that alkylation does not affect the chelation mechanism of uranium and zirconium. Stoichiometries of complexes remain identical for both extractants: UO2L2(NO3)2 and zirconium polynuclear complexes are formed after extraction into the organic phase. The origin of selectivity was therefore investigated by considering the supramolecular self-assembly of the two bifunctional molecules. Small-Angle X ray and Neutrons Scattering (SAXS and SANS) showed that the highest separation factors between U and Zr are obtained when smaller aggregates are formed. The results of this study therefore suggests that the selectivity is controlled by the supramolecular self-assembly of the two extractant molecules. Thanks to a smaller packing parameter, the non-alkylated molecule forms bigger aggregates analogous to reverse micelles that can extract additional polar species in their polar core through a solubilization effect, thus decreasing the separation factor between uranium and zirconium. [ABSTRACT FROM AUTHOR]

We consider here the extraction of metals in the form of salts transferred from an aqueous to a solvent phase. Extraction is triggered by complexation and quenched by the associated necessary reorganization of the structured solvent phase. The extraction of ions changes the relative fraction of extractant molecules that is not part of the highly curved surfactant monolayer and is dispersed molecularly in the oil, and also the polar volume fraction including co-extracted water. The free energy and corresponding microstructures of the water-poor microemulsions are modelled in the frame of the Gaussian random fields (GRF) model. The curvature frustration energy significantly contributes to the free energy of extraction. A typical example of predicted isotherm using the GRF model is compared to the classically considered supramolecular complex formation, together with a minimal Langmuir model and an explicit monomer-to-film equilibrium of amphiphilic extractant. The corresponding small-angle scattering spectra and morphology changes are shown. One implication is that selectivity between a hydrated and a non-hydrated species is concentration dependent and cannot be considered as a constant as a function of the extractant concentration. [ABSTRACT FROM AUTHOR]

Efficient formulations used in hydrometallurgy are often based on synergistic action of two oil-soluble extractants at an optimized mole fraction. In this series of two papers, we describe the N,N'-dimethyl-N,N'-dioctylhexylethoxymalonamide (DMDOHEMA)/di(2-ethylexyl) phosphoric acid (HDEHP) system, and how expression of the synergistic effect varies with acidity, using the three common representations: distribution ratios, yields, and free energies of transfer. The experimental results are detailed in this first part (Part I) with the so-called supramolecular approach, which considers the reverse micelle-like aggregates formed by the lipophilic extractant molecules. It shows that no specific aggregation state is observed at the maximum of synergism and antagonism. Besides, the critical aggregation concentration that characterizes the micellization free energy appears to follow some synergistic trends but cannot explain how acid tunes synergism to antagonism of this mixed system. Based on these results, Part II proposes a theoretical model based on the ienaic approach to interpret acid effect on synergism and antagonism. [ABSTRACT FROM AUTHOR]

The structure of complex organic solutions based on N,N,N',N'-tetraoctyldiglycolamide (TODGA) used in actinide separation processes were characterized after water and neodymium extraction. The organic phases were characterized using FTIR spectroscopy, ESI-MS spectrometry, Small and Wide Angle X-ray Scattering (SWAXS) and molecular dynamic simulations. The role of the "phase modifier" like 1-octanol (used in the innovative SANEX process) or the "co-extractant" like DMDOHEMA (used, for example, in the EURO-GANEX process) added to the organic phase to avoid third-phase formation was investigated at molecular and supramolecular scales. Without metallic cations in 0.2 mol/L TODGA solution in n-heptane, TODGA molecules are organized in monomers and small aggregates containing mainly two or three TODGA molecules. After Nd(NO3)3 extraction, complexes or aggregates are formed in which each neodymium cation is surrounded in average by 2 to 4 TODGA, 3 nitrate ions and 1 to 2 water molecules. Polymetallic species (aggregates) may also be formed. Adding 5%Vol 1-octanol or 0.5 mol/L DMDOHEMA to 0.2 mol/L TODGA solution in n-heptane leads to the formation of mixed aggregates containing TODGA and octanol molecules or TODGA and DMDOHEMA molecules. These molecules both interact directly with the extracted metallic cation in the organic phase, modifying the structure of the neodymium species, and improving their solubility in this organic phase. At least one TODGA molecule remains in the cation first coordination sphere in both cases and preserves its significant role in the complexation/selectivity of the cations. But it is clear that both 1-octanol and DMDOHEMA have a role in the speciation of the cations in the organic phase: 1-octanol replaces water molecules in the first coordination sphere of Nd, acting as a co-surfactant; DMDOHEMA drives the organization and DMDOHEMA molecules partially replace TODGA in the first coordination sphere of Nd. [ABSTRACT FROM AUTHOR]

Liquid-liquid distribution data were determined for the extraction of nitric acid, Am(III), Cm(III), and lanthanides(III) from 0.1–7 mol/L nitric acid into 0.5–1 mol/L N,N'-dimethyl-N,N'-dioctyl-2-[2-(hexyloxy)ethyl]-malonamide (DMDOHEMA) dissolved in kerosene. Nitric acid extraction was accurately modeled accounting for the adducts (HNO3)L2, (HNO3)L, and (HNO3)2L. To model Am(III) extraction, the following complexes were taken into account, Am(NO3)3L4, Am(NO3)3(HNO3)L3, and a third complex, Am(NO3)3(HNO3)2L3 (considering spectroscopic results) or Am(NO3)3(HNO3)2L2 (considering slope-analysis results). Separation factors for Am(III) over Cm(III) and the lighter lanthanides(III) are practically independent of nitric acid concentration. Am(III)/Ln(III) separation factors decrease with increasing nitric acid concentration for the heavier lanthanides(III). [ABSTRACT FROM AUTHOR]

The behavior of three symmetrical sulphoxides, R2SO, where R = Di-(2-ethylhexyl) (DEHSO), R = dihexyl (DHSO) or R = diisoamyl (DIASO) in ionic liquid diluent, 1-methyl-3-octylimidazolium hexafluorophosphate (C8mimPF6) were examined for the extraction of uranyl ion from nitric acid medium. The extraction efficiency is found to be higher for sulphoxides with branched-chain alkyl substituents (DEHSO and DIASO) as compared to the one with linear chain (DHSO). Between branched chain analogues, the one with longer alkyl chain showed better extraction. The stoichiometry of the uranyl species extracted and its redox characteristics were probed by slope analysis, and cyclic voltammetry respectively. The aggregation behavior of the extractant, DEHSO in ionic liquid was examined by small-angle X-ray scattering and is compared with that of DEHSO in dodecane. The extractant remains as aggregates in ionic liquid while in non-polar diluent like dodecane, no aggregates were formed. [ABSTRACT FROM AUTHOR]

Solvents based on malonamides have been described to be very efficient and selective for liquid-liquid extraction of Pd(II) from nitrate media. The present study details the possibility to selectively extract Pd(II) over common metallic cations, Cu(II), Ni(II), Co(II), Zn(II), Nd(III), Fe(III) and Al(III) using N,N'-dimethyl,N,N'-dibutyltetradecylmalonamide (DMDBTDMA) in toluene. The lowest selectivity was obtained considering Fe(III) and Nd(III), the extraction of all other cations being negligible. Pd(II) distribution and selectivity regarding Fe(III) have been fine-tuned using the aqueous HNO3 concentration as the sole parameter, so that extraction, scrubbing and stripping steps can be simply designed without the need for other specific metal chelating reagents and/or aqueous media and without the extensive generation of aqueous effluents. DMDBTDMA was also benchmarked with other classical Pd(II) extractants such as tributylphosphate (TBP), dihexylsulfide (DHS), tetraoctyl diglycolamide (TODGA) and bis(2-ethylhexyl)sulfoxide (BESO) in toluene and in n-heptane. Overall, this study reveals that malonamides are very well positioned and should be considered for further processing of aqueous nitrate wastes containing Pd contaminated with common base metals. [ABSTRACT FROM AUTHOR]

The extraction mechanism of Po(IV) from hydrochloric acid (HCl) solution by tributylphosphate (TBP) and trioctylamine (TOA) was investigated as a function of acid (0.1–12 mol/kg) and extracting agent (0.36–3.64 M) concentrations. Experimental data were modeled to determine the extraction mechanisms as well as the associated thermodynamic constants. Preliminary extraction experiments were carried out using tri-n-octylamine (TOA) in order to determine the activity-corrected Ringbom coefficient in concentrated HCl. The results showed the existence of a species involving two TOA molecules,, which dominated organic polonium speciation in concentrated HCl (9–12 mol/kg). Then, we determined the complexation coefficient ofas a function of HCl concentration in order to calculatemolality for a known total concentration of polonium. The obtained information was used to determine the extraction mechanism occurring in the presence of TBP. The theoretical model agrees with the experimental results considering the existence of the following extracted polonium species:andin the acidic ranges of 0.1–1 and 2–9 mol/kg, respectively. Another extracted species seems to exist in intermediate HCl molality. However, the number of TBP molecules and the associated thermodynamic extraction constant could not be determined. Taken together, the data enable us to propose that the extraction scheme of polonium by TBP corresponds to the following two reactions: [ABSTRACT FROM AUTHOR]

The EXAm (extraction of americium) process was developed for americium recycling in future nuclear fuel cycles. In this solvent extraction system, a combination of two extractants,N,N′-dimethyl-N,N′-dioctyl-hexylethoxy malonamide (DMDOHEMA) and di-2-ethylhexyl phosphoric acid (HDEHP), in TPH (hydrogenated tetrapropylene) is used to extract americium in the first step of the process at high acidity (HNO35–6 M). Americium is co-extracted with light lanthanides and other fission products like molybdenum, iron, ruthenium, etc.. Molybdenum is selectively scrubbed during the second step at low acidity using citric or glycolic acid as a buffer and complexing agent. The speciation of Mo(VI) in aqueous solutions is highly dependent on acidity and Mo concentration. In this article, a simple thermodynamical model is proposed for Mo(VI) scrubbing based on batch extraction experiments (with pH and cation concentration variations) and stoichiometries of complexes formed in the organic phase according to electrospray ionization mass spectrometry (ESI-MS) experiments and published data on Mo(VI) speciation. At high acidity ([HNO3] > 1 M), the MoO22+species is strongly extracted by the solvent DMDOHEMA–HDEHP according to a solvate mechanism. At lower acidity ([HNO3] < 1 M), cation exchange mechanisms become predominant and DMDOHEMA does not participate to the extraction Mo(VI) anymore. During Mo scrubbing at pH higher than 1, the extraction of Mo as neutral species (like MoO3) and anionic species (like MoO42–) has to be taken into account in the model to predict the “bell-shape” of Mo distribution ratio evolution as a function of pH. This model was then implemented in the PAREX simulation code developed by the CEA to build the flowsheet for the “Mo scrubbing” section of EXAm process and predict Mo concentrations profiles in batteries of mixer-settlers during pilot-scale tests. [ABSTRACT FROM PUBLISHER]

The tridentate diglycolamide ligandN,N,N′,N′-tetraoctyl diglycolamide (TODGA) shows many interesting properties and is a very good extractant for the minor actinides (MAs) and lanthanides but, due to its low loading capacity, requires a phase modifier when used in a solvent extraction process. Consequently, applications of TODGA in conjunction with tri-butyl phosphate (TBP) in novel DIAMEX and SANEX processes for recovering MAs have been reported. However, TODGA and TBP also extract nitric acid and this has a significant influence on process performance. Here new distribution data for the extraction of nitric acid into solvent phases containing TODGA and TBP have been collected and modeled using an equilibrium-based approach accounting for nitric acid activities in the aqueous phase. Models for the extraction of nitric acid using the individual extractants were obtained using a variety of complexes and these were then combined to give the extraction of the mixed TODGA and TBP solvent. Using this approach, the nitric acid extraction of the mixed TODGA/TBP system can be reliably reproduced indicating that no significant synergistic or antagonistic complexes are formed in solution. [ABSTRACT FROM PUBLISHER]

Several hydrometallurgical processes studied in France for lanthanide/minor actinide separation use a combination of DMDOHEMA and HDEHP as extractants. Although these processes have proved to be reliable, the modeling of their extraction properties remains a difficult task due to a lack of knowledge about the behavior of the mixed DMDOHEMA-HDEHP organic phase. In the present work, it was found that the solvent extraction of Ln(III) ions by a mixture of these extractants exhibits a complex behavior involving a synergistic effect at either 1 M HNO3or high metal concentration, and an antagonistic effect on extraction of metal traces at higher pH (> 2). To understand these effects, Ln(III) complexes formed after extraction by DMDOHEMA and/or HDEHP were characterized by several spectroscopic techniques (FT-IR, UV-Vis, ESI-MS, TRLIFS). Results suggested formation of DMDOHEMA-HDEHP adducts and ternary mixed complexes involving both extractants and possibly a nitrate ion. [ABSTRACT FROM PUBLISHER]

In a solvent extraction process, the compositions of the phases in thermodynamic equilibrium (described as a Winsor-II regime) must be determined to obtain the extraction isotherms of ions as well as co-extracted water. By comparing the extractions of a series of acids by the malonamide DMDOHEMA (N,N’-dimethyl-N,N’-dioctyl hexylethoxy malonamide) in n-heptane, the specific anion effects regarding third phase formation and the strength of the acid-extractant interaction were investigated. It is shown that third phase formation is driven by hydration enthalpy of acid, while the polar core microstructure is controlled by the pKa of the acids. Upon acid extraction, the promotion of third phase formation follows the series H2SO4≈ H3PO4≈ HClO4> HNO3> HCl > HCOOH, which correlates to hydration enthalpy of acid in the case of monoacids. The combination of IR spectroscopy and DFT calculations revealed two different modes of acid extraction, either by hydrogen bonding (extraction of non-dissociated acid: HA) or by protonation of the extractant (extraction of dissociated acid: H+A−). The strength of the amide-acid interaction (protonation vs. hydrogen bonding) is correlated to the pKa of the acid and is responsible for the microstructure of the solution. [ABSTRACT FROM PUBLISHER]

Non-electrostatic ion-specific effects are strong for anions when water is involved. We study here the thermodynamic equilibrium of a water-in-oil microemulsion stabilized by a surface-active extractant in a Winsor-II regime. Acid extraction isotherms for different anions located differently in the Hofmeister series have been investigated. A Langmuir like model was written for the specific case of acids treated as electrolytes, describing acid extraction as the adsorption of extracted electrolytes on the polar/apolar interface of the aggregates. Except for sulfate, isotherms can be described at first approximation as simple Langmuir-type isotherms when plotted as a function of the acid activity in the aqueous phase. The validity of the model being hence demonstrated, acid extraction free energies could be derived and compared, taking into account the effect of the anion position in the Hofmeister series. The case of phosphate, chloride, and sulfate as kosmotropes can be distinguished. They are significantly extracted, only above a threshold since the sphere-to-rod transition of the reverse aggregates has to be triggered by high chemical potential of the acid required to compensate anion dehydration. [ABSTRACT FROM PUBLISHER]

Liquid-liquid extraction of palladium(II) from nitric media was carried out using,N,N’–dimethyl,N,N’-dioctylhexylethoxymalonamide (DMDOHEMA) inn-heptane. To this purpose, various experimental parameters such as reaction time, extractant concentration, pH, and nitrate concentration were investigated in detail. Efficient extraction of palladium can then be achieved, with good distribution coefficients (D up to 10) and performing kinetics (equilibration timeca. 30 min). In some cases, a solid phase appears at the interface between aqueous and organic layers. It was characterized as a palladium(II) complex with DMDOHEMA with appropriate techniques, and the conditions of its formation are discussed. [ABSTRACT FROM AUTHOR]

During treatment of nuclear fuel in the Plutonium/URanium EXtraction (PUREX) process, the extractant tri-n-butyl phosphate (TBP) is known to degrade to dibutylphosphoric acid (HDBP), which increases the extraction of metal ions, thereby inhibiting their stripping from the organic phase. To better understand this phenomenon, we investigated how mixtures of TBP and HDBP influenced the extraction of metal, nitric acid, and water, and correlated the results to aggregated structures in the organic phase. The mole ratios of TBP-HDBP mixtures had a non-linear effect on the extraction of Dy3+and water from 0.2 M HNO3, indicating synergism. In 2 M HNO3, the TBP:HDBP mole ratio had a more linear relation to Dy3+and water extraction, so the synergistic effect was less pronounced than in the low acid system. The extraction of nitric acid showed no synergistic effect and follows closely what would be expected in a system using TBP only. The small-angle X-ray scattering (SAXS) data of the 0.2 M acid system showed maximum contrast at a TBP:HDBP mole ratio of 0.25, so that the synergistic mixture is also the most aggregated at 0.2 M acid. The 2 M acid system also showed that the mixed system is more aggregated than the end members, although this does not result in peak extraction. Previous studies of synergistic extraction of metal cations explain the enhanced extraction by increased dehydration of the metal ion. Although our data do not rule out the formation of mixed complexes according to the classical mechanism of synergism, our evidence of increased water extraction and aggregate formation in systems combining TBP and HDBP are complementary to the metal-centric dehydration aspects of the process. The findings in this study give insights into the complex chemistry of solvent extraction, providing a possible link between formation of aggregates in the organic phase and synergistic extraction. [ABSTRACT FROM AUTHOR]

Plutonium nitrate solutions contain a large number of chemical species and they exhibit significant deviations from ideal behavior. Modeling this system is challenging. A model that includes all known chemical species and accounts for nonideal solution behavior could contain several hundred unknown parameters, but insufficient published data exists for evaluating large numbers of parameters. A practical model of plutonium nitrate solutions, therefore, must be a compromise between the number of chemical species included and the number of parameters that can be evaluated from available data. A practical model of acidic plutonium nitrate was developed. The model, which was based on an extended UNIQUAC-Debye-Hückel equation, captures the essential behavior of the system with a minimum number of chemical species. It is capable of representing the vapor-liquid equilibrium data for the nitric acid-water system, the activity of water in the plutonium nitrate-nitric acid-water system, the distribution of plutonium-nitrate complexes in aqueous nitric acid solution, and plutonium adsorption on an anion exchange resin. [ABSTRACT FROM AUTHOR]

The Grouped Actinide Extraction (GANEX) process is being developed for actinide recycling within future nuclear fuel cycles. Interactions between potential solvents and macro-concentrations of plutonium are one of the most important issues in defining the GANEX process. Surprisingly, plutonium loading of diglycolamide (DGA) based solvents such as tetra-octyl DGA (TODGA) causes precipitation rather than a conventional third phase, in direct contrast to results with U(VI), Th(IV) or lanthanide ions. Various DGA based solvent systems have been screened for their plutonium loading capacity and 0.2 M TODGA with 0.5 M DMDOHEMA in a kerosene diluent is selected as the optimum solvent formulation of those tested. Plutonium can be relatively easily stripped from this solvent using aqueous acetohydroxamic acid but this is very acid dependent in the low acidity region. [ABSTRACT FROM PUBLISHER]

Extraction of europium(III) from nitric acid medium by a solution of tri- n-butylphosphate (TBP) and n-octyl(phenyl)- N, N-diisobutylcarbamoylmethylphosphine oxide (CMPO) in the room temperature ionic liquid, 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (amimNTf where a = butyl or hexyl or octyl), was studied. The distribution ratio of Eu(III) in TBP-CMPO/bmimNTf was measured as a function of various parameters such as the concentrations of nitric acid, CMPO and NaNO. Remarkably large distribution ratios were observed for the extraction of europium(III) when bmimNTf acted as diluent. The stoichiometry of metal-solvate in organic phase was determined by the slope analysis of extraction data. [ABSTRACT FROM AUTHOR]

In the framework of nuclear waste reprocessing, the separation processes of minor actinides from fission products are developed using liquid-liquid extraction. To gain an understanding of the mechanism involved in the extraction process, a complex formation of actinides and lanthanides with BTBPs (6,6'-bis(5,6-dialkyl-1,2,4-triazin-3-yl)-2,2'-bipyridines) was characterized using the Electrospray Ionization Mass Spectrometry (ESI-MS) technique. This study was carried out to compare the influence of diluents and side groups of the extractants on complex formation. Three different diluents, nitrobenzene, octanol and cyclohexanone, and two extractants, C5-BTBP and CyMe4-BTBP, were selected for this experiment. It was found that the change of the diluent and of the substituent on the BTBP moiety does not modify the stoichiometry of the complexes which is L2M(NO3)3. It is proposed that one nitrate is directly coordinated to the metal ion, the two other anions probably remaining in the outer coordination sphere. The difference observed in extracting properties is probably due to the solvation of the complexes by the diluent. The noncovalent force that holds complexes together are likely to be largely governed by electrostatic interactions even if the hydrophobic exterior of the complexes plays an important role in the complexation/extraction mechanism. The study of the stability of the ions in the gas phase shows that the C5-BTBP ligand has a labile hydrogen atom, which is a fragility point of C5-BTBP. [ABSTRACT FROM AUTHOR]

The results obtained from the extraction of As(V) by 1-(2,6-dimethylheptyl-4-oxy)-3 methyl-1-oxo-Δ3-phospholen (NMPL) are presented in this paper. The conditions of extraction as a function of the extractant and H2SO4 concentrations have been determined. The influence of the extraction of water and sulfuric acid in the extraction process of As(V) has been analyzed. A model of extraction based on the Sergievskii-Dannus' equation has been developed. This model considers the variation of activity coefficients in the aqueous phase and in the organic phase. Thanks to this model its has been possible to predict the theo- retical curves of distribution of H2O, H2SO4 and H3AsO4, in accord with the experimental data. [ABSTRACT FROM AUTHOR]