Radiolyse alpha du ligand DOTA en solution aqueuse

International audienc

Molecular Dynamics Studies of Concentrated Binary Solutions of Lanthanide Salts: Structural and Exchange Dynamics

International audienceConcentrated binary aqueous solutions of lanthanide (Nd3+ and Dy3+) salts (ClO4−, Cl−, and NO3−) have been studied by means of classical molecular dynamics (MD) simulations with explicit polarization and UV−visible spectroscopy. Pair interaction potentials, used for the MD simulations, have been developed in order to reproduce experimental hydration properties. Nd3+ and Dy3+ have been chosen because of their position in the lanthanide series: Nd3+ being a light lanthanide and Dy3+ a heavy one. They are respectively coordinated to nine and eight water molecules, in pure water, involving changes in their salt hydration structures. Both MD simulations and UV−visible experiments highlight the stronger affinity of nitrate anions toward Ln3+ compared to perchlorates and chlorides. Dissociation/association processes of Nd3+−Cl− and Nd3+−NO3− ion pairs in aqueous solution have been analyzed using potential of mean force profile calculations. Furthermore, from MD simulations, it appears that the affinity of anions (perchlorate, chloride, and nitrate) is stronger for Nd3+ than Dy3+

La nécropole du site de Pont-l'Evêque à Autun (71)

International audienc

Sonochemical Behaviour of Pu(III), Pu(IV), and Pu(VI) in Aqueous Nitric Solutions

International audienceReprocessing of spent nuclear fuel is currently carried out via the well-established PUREX process which is a hydrometallurgical treatment performed in nitric acid and based upon redox operations followed by selective solvent extraction of U and Pu. In order to adapt this reprocessing technology to the future nuclear reactors but also to reply to the society concerns, new alternatives are nowadays under investigation to minimise the quantity of generated radioactive wastes, replace obsolete chemicals, increase safety and propose new routes of treatments also supposed resistant against proliferation. Sonochemistry uses the propagation of ultrasonic waves in liquid media to generate physico-chemical transformations in homogeneous solutions and heterogenous systems. The effects generally attributed to ultrasound do not result from direct interactions of acoustic waves with molecules but rather from acoustic cavitation, which is the nucleation, growth and rapid implosive collapse of vapour filled micro-bubbles. At collapse, these bubbles lead to extreme transient conditions of several thousands of degrees and hundreds of atmospheres while keeping the solution at ambient temperature and pressure

Sonochemical redox reactions of Pu( iii ) and Pu( iv ) in aqueous nitric solutions

International audienceThe behavior of Pu(IV) and Pu(III) was investigated in aqueous nitric solutions under ultrasound irradiation (Ar, 20 kHz). In the absence of anti-nitrous reagents, ultrasound has no effect on Pu(IV), while Pu(III) can be rapidly oxidized to Pu(IV) due to the autocatalytic formation of HNO$_2$ induced by HNO$_3$ sonolysis. In the presence of anti-nitrous reagents (sulfamic acid or hydrazinium nitrate), Pu(IV) can be sonochemically reduced to Pu(III). The reduction follows a first order reaction law and leads to a steady state where Pu(IV) and Pu(III) coexist in solution. The reduction process is attributed to the sonochemical generation of H$_2$O$_2$ in solution. The kinetics attributed to the reduction of Pu(IV) are however higher than those related to the formation of H$_2$O$_2$ which, after several hypotheses, is explained by the sonochemical erosion of the titanium-based sonotrode. Titanium particles thereby generated can be solubilized under ultrasound and generate Ti(III) as an intermediate species, a strong reducing agent able to react with Pu(IV)

Development and characterization of composite chitosan/active carbon hydrogels for a medical application

International audienceComposite chitosan/active carbon (AC) hydrogels were elaborated by a novel route, consisting in exposing the chitosan solution to ammonia vapors. This vapor-induced gelation method was compared with the conventional elaboration process, a direct immersion of the chitosan solution in liquid ammonia. The hydrogels were characterized to evaluate their potential application as wound-dressings, mostly regarding their morphology, mechanical properties, swelling behavior, and sorption capacities for malodorous compounds emitted from wounds as diethylamine (DEA). The influence of elaboration route, chitosan concentration, and AC incorporation was studied. The results show that freeze-dried hydrogels have a porous asymmetric structure dependent on the chitosan concentration and which promotes exudates drainage. The nanostructure of the parent hydrogel is semi-crystalline and slightly dependent on the gelation conditions. It confers on hydrogel an acceptable mechanical behavior (compressive modulus up to 1.08 center dot 105 Pa). Hydrogels including AC display enhanced sorption kinetics for DEA, with sorption capacities up to 49 mg g1

Anion selectivity in ion exchange reactions with surface functionalized ionosilicas

International audienceMesoporous imidazolium functionalized surface functionalized ionosilicas have been investigated as anion exchange materials for the adsorption of oxo-anions in aqueous media. We studied particularly pertechnetate adsorption and could show that solids bearing long chain substituted imidazolium groups are highly efficient anion exchange materials often displaying high distribution coefficients between solid and liquid phases. We observed that the distribution coefficient of pertechnetate is a function of the presence of competing anionic species. As a consequence, our experiments allowed reproducing experimentally Hofmeister's series. However, pertechnetate adsorption on the material can completely be inhibited in the presence of highly fluorinated anions such as bis(trifluoromethylsulfonyl) amide (NTf2). This behaviour indicates a particularly imidazophilic behaviour of these anions, which have a particular importance due to their use in water immiscible ionic liquids. Finally, the adsorption process has been shown to be reversible. This feature is of importance in view of the regeneration of the anion exchange material

Investigation of Plutonium(IV) peroxide-based complexes, syntheses and structural characterization

International audienc

Synthèse et caractérisation structurale de complexes de plutonium à base de ligands peroxyde et peroxo-oxalate

National audienc