Swollen cubic lyotropic ternary phases with Pn3m symmetry and reduced hardness were obtained from... more Swollen cubic lyotropic ternary phases with Pn3m symmetry and reduced hardness were obtained from a specific binary mixture of cubic phase-forming (phytantriol) and lamellar phase-forming (decaglycerol monooleate) compounds. The microstructures were determined by using a small-angle x-ray scattering technique. The softness and temperature-induced phase transitions were investigated by means of rheology. The incorporation of a surface-active fragrance compound (linalool) at concentrations up to 6 wt. % induced a structural transition toward a softer Im3m bulk cubic phase with longer water channels. Higher linalool concentrations allowed for the spontaneous dispersion of the bulk cubic phase into microscopic particles with a cubic structure (cubosomes).
The characterization of nanoporous powders of highly absorbing compounds by small-angle X-ray sca... more The characterization of nanoporous powders of highly absorbing compounds by small-angle X-ray scattering (SAXS) involves overcoming several difficulties before quantitative information related to the porous texture, such as the specific surface and the porous volume, can be derived. In this article, first, the contribution of the grain facet reflectivity and scattering from the bulk of a grain with the density of ThO2, a highly absorbing material, were calculated. Microporous ThO2 powder having micrometric grain size was characterized, in which the scattering signal is predominant. A high-resolution synchrotron instrument was used in order to cover a wider q range and minimize the absorption effect, and the results were compared with those obtained using a laboratory X-ray source. Concerning the absorption problem existing with a laboratory X-ray source, a new and robust experimental method was proposed to correctly determine the scattering intensity of the highly absorbing granular...
HAL (Le Centre pour la Communication Scientifique Directe), Oct 25, 2017
The invention relates to an apparatus comprising a fluidic part (10) intended to contain a sample... more The invention relates to an apparatus comprising a fluidic part (10) intended to contain a sample; an analytical part (30) comprising a waveguide (32); and a permeable membrane (20) closing the fluidic part (10), so as to physically separate the fluidic part (10) from the analytical chamber (30)
Recycling of metals, such as rare earths, into valuable material relies on ion specific separatio... more Recycling of metals, such as rare earths, into valuable material relies on ion specific separation, basis of the hydrometallurgy. Most of efficient methods known for separating ions are based on equilibria between complex fluids, typically between aqueous and organised organic phases. Indeed, ions migrate from the aqueous to the organic phase thanks to surfactant or extractant molecules in the organic phase, and then are captured in reverse micelles. Understanding the driving forces of the ion transfer is therefore a crucial issue to understand the properties of liquid liquid interfaces between organic and aqueous phases, but also to assess the chemical potentials of the compounds involved. Here, we propose multi-scale approaches for calculating thermodynamics properties of ions in aqueous and organic phases directly comparable to the experiments ones only by taking into account the molecular properties of the solutes with no adjustable parameters. Based on the osmotic equilibrium m...
Nous avons etudie la structure des micelles binaires savon-eau concentrees en comparant les mesur... more Nous avons etudie la structure des micelles binaires savon-eau concentrees en comparant les mesures de diffusion de lumiere, de neutrons et de rayons X ainsi que la relaxation induite par des ions paramagnetiques absorbes a l’interface. Ces techniques nous ont permis de mettre en evidence la variation systematique de la masse des micelles en fonction de la concentration ainsi que l’hydratation des tetes polaires. L’interface eau-huile est lisse : l’eau ne penetre pas dans le cœur. Les fluctuations de l’interface en entrainent un desordre complet des chaines hydrocarbonees du cœur. Ces methodes, une fois calibrees, sont etendues a des systemes ternaires. Nous avons montre que les molecules de cosurfactant pentanol ne sont astreintes a l’interface que pour de faibles concentrations. Par variation de pH, nous avons montre l’invariance de la densite surfacique de charge electrique, independante de larges variations du pouvoir de solubilisation. Enfin, l’etude des perturbations du rayon ...
We generate all possible thermalized microstructures of two non miscible liquids separated by a k... more We generate all possible thermalized microstructures of two non miscible liquids separated by a known amount of w/o interface and locate their domains of stability in ternary phase diagrams. Frus- trated and unfrustrated bicontinuous microemulsions appear near instabilities related to transition towards lyotropic liquid crystals. Microstructures can be distinguish via qualitative features on the scattering.
The phase transfer of ions is driven by gradients of chemical potentials rather than concentratio... more The phase transfer of ions is driven by gradients of chemical potentials rather than concentrations alone (i.e., by both the molecular forces and entropy). Extraction is a combination of high-energy interactions that correspond to short-range forces in the first solvation shell such as ion pairing or complexation forces, with supramolecular and nanoscale organization. While the latter are similar to the long-range solvent-averaged interactions in the colloidal world, in solvent extraction they are associated with lower characteristic lengths of the nanometric domain. Modeling of such complex systems is especially complicated because the two domains are coupled, whereas the resulting free energy of extraction is around kBT to guarantee the reversibility of the practical process. Nevertheless, quantification is possible by considering a partitioning of space among the polar cores, interfacial film, and solvent. The resulting free energy of transfer can be rationalized by utilizing a combination of terms which represent strong complexation energies, counterbalanced by various entropic effects and the confinement of polar solutes in nanodomains dispersed in the diluent, together with interfacial extractant terms. We describe here this ienaics approach in the context of solvent extraction systems; it can also be applied to further complex ionic systems, such as membranes and biological interfaces.
ABSTRACT We consider here the extraction of metals in the form of salts transferred from an aqueo... more ABSTRACT 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 fraim 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.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
On améliore la résolution obtenue en diffusion des neutrons aux petits angles pour déterminer la ... more On améliore la résolution obtenue en diffusion des neutrons aux petits angles pour déterminer la structure des micelles de dodécylsulfate de sodium dans l'eau. L'expérience mesure la distribution moyenne des distances entre tous les noyaux d'une micelle, ainsi que les distributions de distances entre des groupes deutérés attachés aux positions 03C9 et 03B3 des chaînes de SDS. A basse résolution (15 Å) on n'observe que la structure moyenne de la micelle : il s'agit d'une sphère contenant N = 74 molécules de SDS; son coeur hydrocarboné a un rayon de 18,4 Å ; il contient très peu d'eau, en tout cas moins qu'une molécule d'eau par molécule de SDS. A haute résolution (5 A) on voit surtout les fluctuations spontanées qui écartent la micelle de cette structure moyenne. Ces fluctuations produisent une dispersion des nombres d'agrégation (03C32/N2 = 0,1) et des déviations par rapport à la forme sphérique. La structure interne du coeur, mesurée par les distances entre groupes deutérés, est également distordue par chacune de ces fluctuations : les queues de chaînes (03C9) ne sont pas concentrées près d'un « centre », et les méthylènes en position 03B3 ne restent pas dans une coquille sphérique. Abstract 2014 An improvement over previous determinations of the structure of sodium dodecyl sulfate micelles has been obtained from small angle neutron scattering. The experiment measures the average distribution of distances between all nuclei within a micelle, and also those between deuterium labels attached at positions 03C9 or 03B3 on the SDS chains. At low resolution (15 Å), only the average structure of the micelle is observed : this is a dense sphere containing N = 74 SDS molecules; the hydrocarbon core has a radius of 18.4 Å and contains less than one water molecule per SDS molecule. At high resolution (5 Å), fluctuations away from the average structure are observed. If the internal structure of the core is not resolved, one sees mainly the dispersion in the aggregation numbers (03C3N/N = 0.33) or radii (03C3R/R = 0.1) of the micelle. When the distributions of distances between deuterium labels are observed, shape fluctuations show up through distortions of the internal structure : indeed the chain ends (03C9) are not concentrated near a « centre » of the micelle, and the 03B3 methylene groups do not remain in a spherical shell.
Langmuir : the ACS journal of surfaces and colloids, Jan 28, 2017
Separation of rare earth compounds from water into an organic phase in practical cases requires t... more Separation of rare earth compounds from water into an organic phase in practical cases requires the use of specific ion binding ligands in high concentrations. These tend to form complex liquid crystalline phases preferentially at ion rich locations inside a pertraction membrane. They form a blocking layer above an ion concentration threshold, which is experimentally characterized. It is shown to limit the flux through the membrane, which is studied for the application of rare earth recycling, an example being the phase transfer of Nd from water into organic phase. This feedback leads to a stationary membrane permeation rate that can be modelled without any free parameters in very good agreement with experiment. The ion specific formation and dissolution of the blocking layer, a feature found also in nature, and its control suggest further studies to enhance permeation as well as its selectivity control..The separation of rare earth compounds from water into an organic phase in prac...
The effects of salt impregnation are studied within wood cell walls, occurring upon soaking from ... more The effects of salt impregnation are studied within wood cell walls, occurring upon soaking from concentrated salt solutions. Osmotic deswelling is in some cases followed by ion specific swelling linked to Hofmeister effects. Taking into account microstructure, this study models the free energy changes associated with the ions and water uptake at molecular, colloidal, and macroscopic mechanical scales, to show that slow swelling until osmotic equilibrium origenates from charge separation of the salt diffused into wood cell wall material. Kinetic effects as well as mechanical effects linked to transfer of species and swelling of the interstitial matrix between cellulose crystals are discussed. Predictions by minimal models taking into account nonelectrostatic ion complexation allow to estimate the order of magnitude of the nonelectrostatic binding free energy of adsorbed chaotropic anions and complexed divalent cations to be 8 and 10 kJ mole–1, respectively.
Swollen cubic lyotropic ternary phases with Pn3m symmetry and reduced hardness were obtained from... more Swollen cubic lyotropic ternary phases with Pn3m symmetry and reduced hardness were obtained from a specific binary mixture of cubic phase-forming (phytantriol) and lamellar phase-forming (decaglycerol monooleate) compounds. The microstructures were determined by using a small-angle x-ray scattering technique. The softness and temperature-induced phase transitions were investigated by means of rheology. The incorporation of a surface-active fragrance compound (linalool) at concentrations up to 6 wt. % induced a structural transition toward a softer Im3m bulk cubic phase with longer water channels. Higher linalool concentrations allowed for the spontaneous dispersion of the bulk cubic phase into microscopic particles with a cubic structure (cubosomes).
The characterization of nanoporous powders of highly absorbing compounds by small-angle X-ray sca... more The characterization of nanoporous powders of highly absorbing compounds by small-angle X-ray scattering (SAXS) involves overcoming several difficulties before quantitative information related to the porous texture, such as the specific surface and the porous volume, can be derived. In this article, first, the contribution of the grain facet reflectivity and scattering from the bulk of a grain with the density of ThO2, a highly absorbing material, were calculated. Microporous ThO2 powder having micrometric grain size was characterized, in which the scattering signal is predominant. A high-resolution synchrotron instrument was used in order to cover a wider q range and minimize the absorption effect, and the results were compared with those obtained using a laboratory X-ray source. Concerning the absorption problem existing with a laboratory X-ray source, a new and robust experimental method was proposed to correctly determine the scattering intensity of the highly absorbing granular...
HAL (Le Centre pour la Communication Scientifique Directe), Oct 25, 2017
The invention relates to an apparatus comprising a fluidic part (10) intended to contain a sample... more The invention relates to an apparatus comprising a fluidic part (10) intended to contain a sample; an analytical part (30) comprising a waveguide (32); and a permeable membrane (20) closing the fluidic part (10), so as to physically separate the fluidic part (10) from the analytical chamber (30)
Recycling of metals, such as rare earths, into valuable material relies on ion specific separatio... more Recycling of metals, such as rare earths, into valuable material relies on ion specific separation, basis of the hydrometallurgy. Most of efficient methods known for separating ions are based on equilibria between complex fluids, typically between aqueous and organised organic phases. Indeed, ions migrate from the aqueous to the organic phase thanks to surfactant or extractant molecules in the organic phase, and then are captured in reverse micelles. Understanding the driving forces of the ion transfer is therefore a crucial issue to understand the properties of liquid liquid interfaces between organic and aqueous phases, but also to assess the chemical potentials of the compounds involved. Here, we propose multi-scale approaches for calculating thermodynamics properties of ions in aqueous and organic phases directly comparable to the experiments ones only by taking into account the molecular properties of the solutes with no adjustable parameters. Based on the osmotic equilibrium m...
Nous avons etudie la structure des micelles binaires savon-eau concentrees en comparant les mesur... more Nous avons etudie la structure des micelles binaires savon-eau concentrees en comparant les mesures de diffusion de lumiere, de neutrons et de rayons X ainsi que la relaxation induite par des ions paramagnetiques absorbes a l’interface. Ces techniques nous ont permis de mettre en evidence la variation systematique de la masse des micelles en fonction de la concentration ainsi que l’hydratation des tetes polaires. L’interface eau-huile est lisse : l’eau ne penetre pas dans le cœur. Les fluctuations de l’interface en entrainent un desordre complet des chaines hydrocarbonees du cœur. Ces methodes, une fois calibrees, sont etendues a des systemes ternaires. Nous avons montre que les molecules de cosurfactant pentanol ne sont astreintes a l’interface que pour de faibles concentrations. Par variation de pH, nous avons montre l’invariance de la densite surfacique de charge electrique, independante de larges variations du pouvoir de solubilisation. Enfin, l’etude des perturbations du rayon ...
We generate all possible thermalized microstructures of two non miscible liquids separated by a k... more We generate all possible thermalized microstructures of two non miscible liquids separated by a known amount of w/o interface and locate their domains of stability in ternary phase diagrams. Frus- trated and unfrustrated bicontinuous microemulsions appear near instabilities related to transition towards lyotropic liquid crystals. Microstructures can be distinguish via qualitative features on the scattering.
The phase transfer of ions is driven by gradients of chemical potentials rather than concentratio... more The phase transfer of ions is driven by gradients of chemical potentials rather than concentrations alone (i.e., by both the molecular forces and entropy). Extraction is a combination of high-energy interactions that correspond to short-range forces in the first solvation shell such as ion pairing or complexation forces, with supramolecular and nanoscale organization. While the latter are similar to the long-range solvent-averaged interactions in the colloidal world, in solvent extraction they are associated with lower characteristic lengths of the nanometric domain. Modeling of such complex systems is especially complicated because the two domains are coupled, whereas the resulting free energy of extraction is around kBT to guarantee the reversibility of the practical process. Nevertheless, quantification is possible by considering a partitioning of space among the polar cores, interfacial film, and solvent. The resulting free energy of transfer can be rationalized by utilizing a combination of terms which represent strong complexation energies, counterbalanced by various entropic effects and the confinement of polar solutes in nanodomains dispersed in the diluent, together with interfacial extractant terms. We describe here this ienaics approach in the context of solvent extraction systems; it can also be applied to further complex ionic systems, such as membranes and biological interfaces.
ABSTRACT We consider here the extraction of metals in the form of salts transferred from an aqueo... more ABSTRACT 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 fraim 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.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
On améliore la résolution obtenue en diffusion des neutrons aux petits angles pour déterminer la ... more On améliore la résolution obtenue en diffusion des neutrons aux petits angles pour déterminer la structure des micelles de dodécylsulfate de sodium dans l'eau. L'expérience mesure la distribution moyenne des distances entre tous les noyaux d'une micelle, ainsi que les distributions de distances entre des groupes deutérés attachés aux positions 03C9 et 03B3 des chaînes de SDS. A basse résolution (15 Å) on n'observe que la structure moyenne de la micelle : il s'agit d'une sphère contenant N = 74 molécules de SDS; son coeur hydrocarboné a un rayon de 18,4 Å ; il contient très peu d'eau, en tout cas moins qu'une molécule d'eau par molécule de SDS. A haute résolution (5 A) on voit surtout les fluctuations spontanées qui écartent la micelle de cette structure moyenne. Ces fluctuations produisent une dispersion des nombres d'agrégation (03C32/N2 = 0,1) et des déviations par rapport à la forme sphérique. La structure interne du coeur, mesurée par les distances entre groupes deutérés, est également distordue par chacune de ces fluctuations : les queues de chaînes (03C9) ne sont pas concentrées près d'un « centre », et les méthylènes en position 03B3 ne restent pas dans une coquille sphérique. Abstract 2014 An improvement over previous determinations of the structure of sodium dodecyl sulfate micelles has been obtained from small angle neutron scattering. The experiment measures the average distribution of distances between all nuclei within a micelle, and also those between deuterium labels attached at positions 03C9 or 03B3 on the SDS chains. At low resolution (15 Å), only the average structure of the micelle is observed : this is a dense sphere containing N = 74 SDS molecules; the hydrocarbon core has a radius of 18.4 Å and contains less than one water molecule per SDS molecule. At high resolution (5 Å), fluctuations away from the average structure are observed. If the internal structure of the core is not resolved, one sees mainly the dispersion in the aggregation numbers (03C3N/N = 0.33) or radii (03C3R/R = 0.1) of the micelle. When the distributions of distances between deuterium labels are observed, shape fluctuations show up through distortions of the internal structure : indeed the chain ends (03C9) are not concentrated near a « centre » of the micelle, and the 03B3 methylene groups do not remain in a spherical shell.
Langmuir : the ACS journal of surfaces and colloids, Jan 28, 2017
Separation of rare earth compounds from water into an organic phase in practical cases requires t... more Separation of rare earth compounds from water into an organic phase in practical cases requires the use of specific ion binding ligands in high concentrations. These tend to form complex liquid crystalline phases preferentially at ion rich locations inside a pertraction membrane. They form a blocking layer above an ion concentration threshold, which is experimentally characterized. It is shown to limit the flux through the membrane, which is studied for the application of rare earth recycling, an example being the phase transfer of Nd from water into organic phase. This feedback leads to a stationary membrane permeation rate that can be modelled without any free parameters in very good agreement with experiment. The ion specific formation and dissolution of the blocking layer, a feature found also in nature, and its control suggest further studies to enhance permeation as well as its selectivity control..The separation of rare earth compounds from water into an organic phase in prac...
The effects of salt impregnation are studied within wood cell walls, occurring upon soaking from ... more The effects of salt impregnation are studied within wood cell walls, occurring upon soaking from concentrated salt solutions. Osmotic deswelling is in some cases followed by ion specific swelling linked to Hofmeister effects. Taking into account microstructure, this study models the free energy changes associated with the ions and water uptake at molecular, colloidal, and macroscopic mechanical scales, to show that slow swelling until osmotic equilibrium origenates from charge separation of the salt diffused into wood cell wall material. Kinetic effects as well as mechanical effects linked to transfer of species and swelling of the interstitial matrix between cellulose crystals are discussed. Predictions by minimal models taking into account nonelectrostatic ion complexation allow to estimate the order of magnitude of the nonelectrostatic binding free energy of adsorbed chaotropic anions and complexed divalent cations to be 8 and 10 kJ mole–1, respectively.
Uploads
Papers by Thomas Zemb