RSS export of vacancies - Seulement les offres à la une : No / Profil : Physique de l'état condensé, chimie et nanosciences / Site : Marcoule

SL-DES-24-0167 - Physico-chemical coupling between a bubbles population and the oxido-reduction of glass-forming liquid

Wed, 11 Oct 2023 02:15:11 Z

Category : Condensed Matter Physics, chemistry, nanosciences
Contract : Thèse
Thesis topic details :
The calcination-vitrification process is the solution used in France for more than 30 years for the conditioning of high-level nuclear waste resulting from the reprocessing of spent fuel. During the vitrification process, the waste is incorporated into a borosilicate glass-forming liquid at more than 1000°C. The glass-forming liquid is homogenized in temperature and composition by stirring and gas bubbling. The incorporation of waste into glass-forming liquid can also lead to gas releases, including those of oxygen resulting from redox reactions between species dissolved in the liquid. It is important to properly control the impact of these gases on the glass and the process. The redox state of glass-forming liquid at equilibrium between the dissolved species has been the subject of various studies at the CEA in the context of the vitrification of nuclear waste [1, 2]. On the other hand, few studies have been devoted to the kinetics of gas reactions in glass-forming liquid [3, 4]. The objective of this thesis aims to study and model the impact of gas bubbles, whatever their nature, on the redox of melting and the kinetics of associated reactions. An approach combining experimentation and digital modeling will be adopted. A taste for experimentation, characterization and interpretation of results addressing different scientific fields is important to carry out this work. All experiments will be carried out on non-radioactive elements and will involve processing by digital modeling.

Physico-chemical coupling between a bubbles population and the oxido-reduction of glass-forming liquid

SL-DES-24-0110 - Direct precipitation of mixed oxides by reductive hydrothermal conversion

Wed, 11 Oct 2023 02:15:11 Z

Category : Condensed Matter Physics, chemistry, nanosciences
Contract : Thèse
Thesis topic details :
The development of new technologies of nuclear reactors implies to consider innovative methods for manufacturing (U,Pu)O2 MOx fuels. In this context, recent works focused on the hydrothermal conversion of tetravalent actinide carboxylates, in particular oxalates. This process enables hydrated actinide oxides to be obtained directly by using 'mild' conditions. The characteristics of the powders obtained can also be controlled by adjusting the experimental conditions. However, no study involving the uranyl cation UO22+ has been reported, although several studies have highlighted the reduction of U(VI) by organic matter in geological environments. The aim of this PhD thesis is therefore to address the direct precipitation, under reductive hydrothermal conditions, of UO2+x and associated solid solutions from uranyl-based solutions. The study of simple systems containing only U(VI) will first be undertaken by considering different sources of organic matter. A multiparametric study will specify the experimental conditions for the reduction of U(VI) to U(IV) and the quantitative formation of UO2+x, while the reduction mechanism will be studied using in situ XANES analyses on ESRF FAME and FAME-UHD beamlines. The second part of the work will concern the study of mixed systems initially containing uranium (VI) and a tetravalent cation. The U(VI)-Th and U(VI)-Ce(IV) systems will be studied as a first approach, in order to progressively increase the complexity of the redox behaviour of the samples. Finally, the study will be transposed to the U(VI)-Pu(IV) system at CEA Marcoule's ATALANTE facility, in collaboration with the DES/DMRC/SPTC/LSEM. Regardless of the chemical system studied, a complete physico-chemical characterisation of the solids obtained will be undertaken. The sintering of the powders prepared will also be studied. The aim of this thesis work is therefore to propose an alternative route for manufacturing/remanufacturing future-generation nuclear fuels, by offering the original possibility of reducing uranium(VI) in situ in the reactor, which constitutes a direct route from ions in solution to the final solid. The successful candidate will have a master's or engineering degree in radiochemistry, separative chemistry or materials chemistry. In the course of his/her work, he/she will be required to master numerous techniques relating to materials chemistry, microscopy and solution chemistry, which will enable him/her to develop skills not only in the nuclear field, but also more broadly in the field of ceramic materials development.

Direct precipitation of mixed oxides by reductive hydrothermal conversion

SL-DES-24-0080 - The Pd-Rh-Ru-Te-O system in nuclear glasses and its impact on the glass melt conductivity

Wed, 11 Oct 2023 02:15:11 Z

Category : Condensed Matter Physics, chemistry, nanosciences
Contract : Thèse
Thesis topic details :
In France, the high-level nuclear waste is vitrified. The components of the waste are integrated in a vitreous borosilicate network and form a homogeneous glass. However, platinum group metals (PGM) Pd, Rh and Ru are very poorly soluble in the glass melt and they form particles, combined or not with oxygen or tellurium. These PGM particles may modify the physical properties of the glass melt and especially its electrical conductivity wich is paramount for the process control. Hence, the knowledge of the speciation and the morphology of the PGM elements is essential for the control of the vitrification process. Thereby, this PhD will be split in 2 interdependent approaches: the first one by thermodynamic Calphad calculations and the other one by experimentations. First, the experimental approache will aim to understand and quantify the reduction of (Ru,Rh)O2 and the solubilisation of Ru and Rh in Pd-Te thanks to elaborations and characterizations (SEM-EDS-WDS and XRD mainly) of glasses with PGM particles. The results will complete a Calphad database. Calculations will help to discuss experimental results and will enable to predict the PGM state in the glass melt during the industrial vitrification. Secondly, electrical conductivity measurements at high temperature will be implemented on the glasses previously made to determine the impact of Ru and Rh speciation on the global conductivity of the melt.

The Pd-Rh-Ru-Te-O system in nuclear glasses and its impact on the glass melt conductivity

SL-DES-24-0067 - Development of mixed oxide-based catalysts for the valorization of bioethanol into butanol

Wed, 11 Oct 2023 02:15:11 Z

Category : Condensed Matter Physics, chemistry, nanosciences
Contract : Thèse
Thesis topic details :
The production of biobutanol from bioethanol via the Guerbet reaction is an important process for improving the valorization of biomass into new generation biofuels. The objective of this thesis is to develop new catalysts based on mixed oxides which allow this reaction in the liquid phase. The starting formulation is the CuMgAl mixed oxide of hydrotalcite type. Partial or total substitutions in the Cu and Al sites by Ni and/or Co and Ce and/or La respectively will be studied. A modulation of the microstructure will also be studied by synthesizing these oxides using different synthesis routes (NPG, alginate, etc.). Once synthesized, the oxides will be characterized by classic XRD, SEM, BET/BJH, ATG, high-resolution TEM methods, but also by TDP of NH3 and CO2 in order to determine the quantity of acidic and basic sites. The synthesized catalysts will then be tested in the Guerbet reaction of ethanol in the liquid phase, in a batch reactor, the products being analyzed by gas chromatography coupled with high resolution mass spectrometry to determine the ethanol conversion rates. but also the selectivity of the conversion to butanol. After an initial screening, complete kinetic studies will be carried out on the 2 or 3 most promising formulations by varying all the parameters (temperature, quantity of catalysts, moisture absorber, etc.). Post-reaction characterizations will be carried out to study possible deactivation of the catalysts by coking phenomena. Finally, it will be considered to develop a continuous process in order to overcome the disadvantages of a discontinuous batch process.

Development of mixed oxide-based catalysts for the valorization of bioethanol into butanol

SL-DES-24-0059 - Study of molten chloride salt fast reactor fuel synthesis and purification

Wed, 11 Oct 2023 02:15:11 Z

Category : Condensed Matter Physics, chemistry, nanosciences
Contract : Thèse
Thesis topic details :
Among a large variety of innovative reactor concepts used to decarbonize industry, a French fast reactor using molten chloride salts as fuel and primary coolant has been developed with a CEA-Orano collaboration. The reactor operates at temperature up to 600 °C in which actinides (An) are homogeneously dissolved in the liquid phase containing alkaline and alkaline earth chlorides. To feed it, an essential step is to produce the NaCl-MgCl2-AnCl3 fuel salt system without impurities to avoid corrosion and precipitations issues. The main aim is to study a way of producing molten salt fuel with a high purity level (as low contaminants content as possible). The first step is to synthesize and characterize actinide chlorides by a multi-scale approach (XRD, SEM, TGA-DSC, WDS…). Actinide chlorides are hygroscopic and easily absorb moisture from the environment. The reference synthesis route is a gas-solid reaction by hydrochlorination of actinide oxalate. The investigation of other synthesis methods is also planned in order to obtain less hygroscopic material. Synthesized products will studied by electrochemistry after dissolution in the molten salt phase to determine actinides purity and contaminants nature and content. A purification process is used as the last step to remove most of impurities from the molten salt. Purification issues are impurity content determination and the definition of salt purity criterion. Some physicochemical properties measurements could be performed with purified salts.

Study of molten chloride salt fast reactor fuel synthesis and purification

SL-DES-24-0049 - New cyclic extractant molecules for uranium/plutonium separation

Wed, 11 Oct 2023 02:15:11 Z

Category : Condensed Matter Physics, chemistry, nanosciences
Contract : Thèse
Thesis topic details :
This thesis subject is dedicated to the optimization of the uranium/plutonium separation process (PUREX) for spent nuclear fuels reprocessing. New extractant molecules based on cyclic monamide functions will be studied for targeted elements separation by liquid-liquid extraction from nitric acid medium. They should be soluble in industrial aliphatic diluents, adaptable to extraction technologies actually used in terms of density, viscosity, solubility and extraction kinetics. Their affinity and selectivity towards U and Pu should be adjusted to allow process flowsheet optimization. In order to help in the target molecules selection, theoretical DFT calculations (Density Functional Theory) will be investigated to make a comparative estimate of their affinity towards U and Pu elements. Then the student will have to determine the feasibility of organic synthesis and to propose and optimize synthesis pathways. Once the molecules will be purified and their structures and purity characterized, their separation performances will be assessed by liquid-liquid batch extraction tests involving radioelements of interest in active laboratories of ATALANTE facility. Their resistance towards hydrolysis and radiolysis will be evaluated after batch gamma irradiation tests. Finally, the structures of metallic complexes formed in organic phases with those new extractant molecules will be studied to better understand extraction mechanisms and propose new orientations for future synthesis.

New cyclic extractant molecules for uranium/plutonium separation

SL-DES-24-0037 - Development of lipophilic aminopoly(carboxylic) or hydroxamic acid ligands for ion separation

Wed, 11 Oct 2023 02:15:11 Z

Category : Condensed Matter Physics, chemistry, nanosciences
Contract : Thèse
Thesis topic details :
The subject of this thesis has been defined with the aim of proposing new liquid-liquid extraction (LLE) processes applicable to the recycling of lanthanides and actinides at downstream of the nuclear fuel cycle. The proposed methodology relies essentially on the availability of lipophilic ligands derived from highly polar chelating agents such as poly(aminocarboxylic) acids (PACA) or hydroxamic acids (HA). As a first step, the PhD student will be involved in a major organic synthesis project, building up a library of several of these different derivatives. During the first phase of the thesis, the candidate will be allowed to develop his activity based on knowledge and results already acquired in this field at LTSM. In subsequent phases, he or she will be asked to develop new, more efficient and, in some cases, stereoselective (enantio- and/or diastereoselective) synthesis strategies when several stereoisomers can be obtained. Concomitantly to this, the candidate will be asked to characterize the extraction properties (affinity and selectivity) of the yielded ligands towards valuable lanthanides and actinides. This will be carried out using well proven approaches, enabling quantitative and qualitative monitoring of ELL performed on a scale of a few milliliters. The PhD student will be supervised throughout his thesis by two co-directors and a supervisor, who will provide him with multidisciplinary expertise.

Development of lipophilic aminopoly(carboxylic) or hydroxamic acid ligands for ion separation

SL-DES-24-0077 - X-ray Emission spectroscopy: an alternative to X-ray emission spectroscopy for studying the actinide’s p

Wed, 11 Oct 2023 02:15:11 Z

Category : Condensed Matter Physics, chemistry, nanosciences
Contract : Thèse
Thesis topic details :
Optimal exploitation of nuclear fuels is essential to maintain low-carbon energy production for decades to come. To this end, fuels such as mixed oxides U1-yPuyO2-x are being considered. However, the safety of their future use, requires an exhaustive multi-scale understanding of their behavior during both their manufacturing and their irradiation in reactor, as well as their compatibility with the dissolution processes necessary for their recycling. X-ray Absorption Spectroscopy (XAS) is a key technique for fuel characterization that is extensively employed at CEA Marcoule. A complementary approach to the latter is X-ray Emission Spectroscopy (XES). However, while XES studies are numerous in the context of 3d elements, only very few are available for actinides. Those studies suggest the possible access to new knowledge on the properties of fuels, while being characterized by a lower detection limit compared to XAS. The main objective of this thesis work is therefore the development of the methodology and instrumentation necessary for XES analyzes at the lab scale as well as the realization of experimental campaigns dedicated to the understanding of the links between experimental observations and the intrinsic properties of actinides. The thesis will be carried out in collaboration between CEA Marcoule and the University of Helsinki and will begin with a 1.5-year period in Helsinki before continuing at CEA Marcoule.

X-ray Emission spectroscopy: an alternative to X-ray emission spectroscopy for studying the actinide’s physico-chemistry ?

SL-DES-24-0038 - Comportement d’un bloc de verre fracturé en phase vapeur

Wed, 11 Oct 2023 02:15:11 Z

Category : Condensed Matter Physics, chemistry, nanosciences
Contract : Thèse
Thesis topic details :
L’altération du verre au cours du temps est largement étudiée dans de multiples domaines d’application, dont un majeur : le stockage des déchets radioactifs en couche géologique profonde. En effet, ces déchets sont vitrifiés en vue d’un stockage à très long terme dans des galeries à 500 m de profondeur. Il est prévu que l’eau liquide n’atteigne pas les colis de verre avant une centaine de milliers d’années. Néanmoins, durant cette période, une certaine humidité relative est attendue dans l’espace de stockage. Ainsi, l’impact de la vapeur d’eau sur le verre doit être pris en compte pour prédire le comportement du colis de verre sur toute la période de décroissance radioactive des radionucléides. Le colis est intrinsèquement fracturé ; en cause : des gradients thermiques lors du refroidissement après coulée. Les fissures développées accroissent la surface réactive du matériau. Mais à quel point ? Quelle est la contribution des fissures dans l’altération globale du bloc en phase vapeur ? Est-ce que de l’eau condense au sein du réseau de fissures, induisant l’altération du matériau en milieu liquide ultra-confiné ? Si oui, dans quelles proportions ? De ces questions découlent d’autres problématiques à aborder telles que l’évolution de l’altération au cours du temps dans ce système potentiellement biphasique, ainsi que le comportement du bloc de verre lors de l’arrivée de l’eau liquide. Cette thèse se propose donc de répondre à ces questions en menant des études sur des verres simulants non radioactifs. Des systèmes de fissures modèles ainsi que des blocs de verre fracturés seront utilisés. Au cours de ce travail, le doctorant sera donc amené à élaborer des verres au laboratoire et à réaliser des expériences en exposant des échantillons à la vapeur d’eau dans des chambres atmosphériques. La thèse comportera trois parties constituées de 1) l’étude de la condensation au sein du réseau de fissures, 2) l’étude de l’altération et de son évolution au cours du temps et 3) le comportement de ces systèmes lors de la remise en eau liquide. Un large panel de techniques d’analyse sera déployé pour caractériser les échantillons solides et liquides. Au sein même du service, le doctorant pourra être formé à la manipulation du DVS (études de sorption de l’eau), du MEB-EDS, de la DRX, du spectromètre Raman ainsi qu’au spectromètre UV-Visible. Des collaborations sont envisagées pour mener des analyses par MET, de la tomographie, de l’AFM ou encore de la RMN. Pour ce travail, le candidat devra présenter des compétences solides dans le domaine de la science des matériaux. Il devra être curieux, ouvert et dynamique car il sera amené à interagir avec de nombreuses personnes, voire potentiellement à collaborer avec des intervenants dans un cercle plus élargi que le domaine du verre (concernant les milieux fissurés d’autres matériaux). Cette thèse apportera au doctorant de larges compétences techniques au vu du nombre d’outils analytiques prévus. Par ailleurs, ce travail lui fournira une connaissance poussée du matériau qui pourra être valorisée dans de nombreux domaines d’activités.

Comportement d’un bloc de verre fracturé en phase vapeur

SL-DES-24-0166 - Kinetics and mechanisms of corium leaching

Wed, 11 Oct 2023 02:15:11 Z

Category : Condensed Matter Physics, chemistry, nanosciences
Contract : Thèse
Thesis topic details :
During a severe nuclear accident, significant quantities of 'volatile' fission products are released during core degradation. A further significant proportion of radionuclides (RN) from degraded nuclear fuels are incorporated into solidified materials (corium and fuel debris), and their medium- to long-term stability is of major importance for accident site safety. Depending on the progress of the accident and subsequent interactions with different materials (cladding, internal structures, vessel materials and concrete), corium may have different structures and compositions. Generally speaking, it is a highly heterogeneous, multiphase material within which the distribution of radionuclides is poorly understood. In this context, the aim of this thesis is to improve our understanding of the mechanisms of corium leaching and radionuclide release into water, through parametric studies on model materials. This work, carried out with a view to increasing the complexity of the materials studied, will enable us to prioritize the influence of different parameters (temperature, solution composition, presence of oxidizing radiolytic species) on the transfer of RNs into solution. Taken together, these results will improve our understanding of the evolution of the RN inventory contained in a corium in an underwater cooling scenario, and our knowledge of the chemical durability of the different phases it contains.

Kinetics and mechanisms of corium leaching

SL-DES-24-0143 - Study of rheological phenomena occurring during thermal treatment for waste encapsulation into a glassy

Wed, 11 Oct 2023 02:15:11 Z

Category : Condensed Matter Physics, chemistry, nanosciences
Contract : Thèse
Thesis topic details :
Operations of decontamination and dismantling generate highly diverse waste in terms of chemical composition and physical form. It can take the form of solid deposits, powders, sludges or liquid solutions. To condition them, encapsulation with a glassy binder seems promising because of its lower working temperature than conventional vitrification processes. The process involves heating mixtures of waste and vitreous adjuvant between 800 and 1200°C, which requires a deep understanding of the rheological behavior of the system at temperature. Three research directions will be explored during the thesis: the influence of waste loading and nature of the adjuvant on the flow behavior, the behavior of volatile species in mixtures made of wet waste and adjuvant, and the impact of potential reactivity between the waste and the adjuvant on the system properties. Final objective will be, on one hand, to optimize the container filling rate while maximizing the waste loading rate, on the other hand, to guide the choice of the most suitable vitreous adjuvant. The PhD student will benefit from the recognized skills of the host laboratory in the field of rheology of complex systems from low temperature (slurries, bitumens, cements) to high temperature (homogeneous and crystallized glass melts), and from all the characterization resources required for the successful completion of the thesis. The entire thesis will be carried out in a non-nuclear environment, using inactive simulants.

Study of rheological phenomena occurring during thermal treatment for waste encapsulation into a glassy matrix

SL-DES-24-0142 - Rheology of partially-crystallized glass melts: from experimental data acquisition to modeling

Wed, 11 Oct 2023 02:15:11 Z

Category : Condensed Matter Physics, chemistry, nanosciences
Contract : Thèse
Thesis topic details :
The formulation of a radioactive waste packaging glass is the result of a compromise between waste loading, technological feasibility and chemical durability. Maximizing the waste loading rate allows us to reduce the number of vitrified packages produced, and consequently the volume and cost of the underground disposal. On the other hand, increasing this loading rate beyond a certain threshold is likely to lead to the presence of crystals in the vitrification furnaces. However, such an evolution of glass formulations requires, among other things, verification of the impact of the presence of these crystals on the properties of the glass during its production (at 1100-1200°C), in particular its rheology, a key property for the good operation of vitrification furnaces. The aim of the proposed thesis is therefore to measure and then model the effect of crystals on rheology, as a function of time, temperature, and nature and morphology of the crystals, and to take into account the risk of sedimentation. To do this, experimental data will have to be acquired, then modelled using models proposed in the literature, which may need to be adapted.

Rheology of partially-crystallized glass melts: from experimental data acquisition to modeling

SL-DES-24-0128 - Simulations of radiolysis in organic phases with plutonium

Wed, 11 Oct 2023 02:15:11 Z

Category : Condensed Matter Physics, chemistry, nanosciences
Contract : Thèse
Thesis topic details :
Molecular simulations of ionizing irradiation of plutonium extractant solutions The CEA is developing separation processes for the multi-recycling of plutonium in spent nuclar fuel. The preferred technology for separating plutonium is solvent extraction. In solvents, radiolysis phenomena generated by the presence of alpha radiation emitters such as plutonium are numerous. A better understanding of these phenomena is essential to develop and control these processes. The aim of this thesis will be to understand the mechanisms by which organic solutions are damaged by radiolysis, using numerical simulations. On a microscopic scale, the irradiation of matter by alpha particles begins with a deposition of energy in the electron cloud, leading to the excitation or ionization of the molecules in the medium. This process takes place on the attosecond time scale. The energy thus deposited is then dissipated in nuclear vibration modes, leading to the localization of charges on certain molecular fragments, the weakening of chemical bonds or even their rupture, and the production of reactive chemical species. The latter are the precursors of chemical reactions occurring at later times. To simulate these ultrafast processes on the basis of first principles, we will adopt the Time-Dependent Density Functional Theory (TD-DFT) methods [1]. TD-DFT simulations consist in explicitly propagating in time the evolution of the electronic cloud subjected to a perturbation such as a collision by an alpha particle. These simulations give access to the amount of energy delivered to the system at atomic resolution, and to the dynamics of the electron cloud. Coupling the TD-DFT simulations with the Newtonian molecular dynamics simulations of atomic nuclei, then gives access to the simulation of ultrafast chemistry taking place on femto- and picosecond timescales. Hybrid QM/MM (Quantum Mechanics/Molecular Mechanics) schemes will be used to account for environmental effects (solvent, counter-ions)[1,2]. The PhD student will be trained in a wide range of methods in the field of theoretical chemistry. The successful candidate will have a good background in physical and/or quantum chemistry, be motivated and hard-working. Previous experience in numerical simulation, acquired for example during Master's research internships, will be an advantage. The thesis will be carried out under the joint supervision of D. Guillaumont (CEA) and A. de la Lande (Université Paris Sud), requiring the PhD candidate to be located for long periods on each of the two sites of CEA Marcoule and Université Paris Sud. [1] X Wu, JM Teuler, F Cailliez, C Clavague´ra, DR Salahub, A de la Lande, J. Chem. Theor. Comput. 2017,13, 3985-4002. [2] K. A. Omar, F. A. Korsaye, R. Tandiana, D. Tolu, J. Deviers, X. J. Wu, A. Parise, A. Alvarez-Ibarra, F. Moncada, J. N. Pedroza-Montero, D. Mejía-Rodriguez, N. T. Van-Oanh, F. Cailliez, C. Clavaguéra, K. Hasnaoui, A. de la Lande, European Physical Journal-Special Topics 2023.

Simulations of radiolysis in organic phases with plutonium

SL-DES-24-0061 - Synthesis and shaping of Metal-Organic Frameworks for the capture of noble gas (Xe, Kr)

Wed, 11 Oct 2023 02:15:11 Z

Category : Condensed Matter Physics, chemistry, nanosciences
Contract : Thèse
Thesis topic details :
The design of new nuclear reactors named MSR, for Molten Salt Reactor, is currently being studied at the CEA, but also internationally. During their operation, gaseous fission products are generated and must be extracted, in particular Xe and Kr. For this purpose, adsorption on solid support in fixed bed columns are considered, but such processes require the development of very selective materials with high sorption capacities. Recently, Metal-Organic Framework (MOF) materials have demonstrated exceptional selectivity for noble gas trapping. However, such materials are generally synthesized in a fine powder form, which is not compatible with an application in fixed bed processes. This PD works aims to synthesize MOFs and develop a shaping technique, so that they can be used in columns for the trapping and separation of noble gases. Firstly, the most promising MOF structures will be identified in the literature and synthesized in laboratory. Then a process allowing their granular shaping will be developed. This shaping will optimize the application of MOFs in a fixed bed column process and their capture performances will be determined using a gas separation pilot. The student must have a strong interest in experimentation. He/she will develop skills in synthesis and characterization of materials (SEM, XRD, nitrogen adsorption-desorption, etc.). More generally, the student will have the opportunity to address the complexities linked to a gas treatment process using fixed bed columns.

Synthesis and shaping of Metal-Organic Frameworks for the capture of noble gas (Xe, Kr)

SL-DES-24-0033 - Eutectic solvents for leaching and separation of lanthanides and actinides

Wed, 11 Oct 2023 02:15:11 Z

Category : Condensed Matter Physics, chemistry, nanosciences
Contract : Thèse
Thesis topic details :
The separation of chemical elements is at the heart of the mining, the recycling of nuclear and electronic waste and water decontamination. However, hydrometallurgical processes such as liquid-liquid extraction and leaching use considerable volumes of solvents and organic compounds that are often polluting and volatile. Today, the environmental challenges of reducing the use of volatile organic compounds represent a key challenge for hydrometallurgy. Hydrophobic eutectic solvents have recently been considered for liquid-liquid extraction[1], offering a number of advantages such as lower volatility and higher flash point, as well as improved extraction performance in some cases associated with different extraction mechanisms compared with the diluents conventionally used in liquid-liquid extraction. [2,3] Our laboratory has also carried out promising preliminary tests to apply these hydrophobic eutectic solvents to the leaching of metallic powders. Although very promising, eutectic solvents are still not widely applied in hydrometallurgy because they need to be optimised and better understood. The aim of this thesis will therefore be to prepare and test hydrophobic eutectic solvents (HES) based on conventional extractant molecules known in the laboratory and to study their liquid-liquid extraction and leaching properties with respect to various metals of interest such as lanthanides and actinides. The mechanisms of extractions in these unconventional solvents will be addressed by closely observing the effects of complexation and structuring, in order to optimise performance. The extraction properties of various metals will be evaluated by ICP-OES and compared with the physico-chemical and structural properties of the systems (density and viscosity measurements, acid-base and Karl Fisher titration, NMR and IR spectroscopies, tensiometry, X-ray and small-angle neutron scattering (SAXS, SANS), etc.).

Eutectic solvents for leaching and separation of lanthanides and actinides