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International audience; The control of biofouling is required to improve membranes performances for water filtration. In this context, developing bioinspired approaches to modify membranes and give them antifouling properties is an interesting alternative. In this study, we elaborated new anti-biofouling membranes by coating them with vanillin, a natural bioactive molecule acting as a Quorum Sensing Inhibitor (QSI). First, the adsorption of vanillin by filtration was optimized to obtain homogeneous surface modifications. The modified membranes were then characterized in terms of physical-chemical properties: the results showed that they were more hydrophobic and exhibited a 14% decrease in pure water flux. Then, their anti-fouling properties were evaluated using complementary multiscale characterization methodologies; AFM single-cell experiments showed that vanillin adsorption had an effect on both the probability of bacterial cells to adhere to the surface, and on the force of adhesion. Direct EFM and SEM observation and adhesion assays further confirmed the effect of vanillin-modified membranes at the population-scale which showed a decrease in the bacterial coverage rate up to 50%. Altogether, it confirms the multifunctionality of vanillin-coated membranes against biofouling: reduction of bacterial initial adhesion by changing the membranes surface properties and reduction of biofilm formation by quorum sensing inhibition

International audience; The behavior of a particle mixture composed of short fibers and silicon carbide powder in variable proportions has been experimentally investigated. The study shows that the hydrodynamic behavior of a bed initially composed of powder is affected as soon as a few percent of short fibers are added. The minimum fluidization velocity (Umf) is globally lowered and the intrinsic properties of the porous medium (equivalent particle diameter, porosity, flow coefficients…) are altered. Several hydrodynamic equations describing Umf as a function of the pressure are considered and the intrinsic properties of the bed such as the hydraulic diameter or the Darcy and Knudsen coefficients are fitted. The Darcy-Klinkenberg equation on one hand and a semi-empirical correlation based on Ergün’s equation on the other hand, are both adapted to describe the Umf behavior as a function of a limited number of initial parameters. The semi-empirical correlation leads to the best Umf prediction, with an absolute error of less than 10%, using only the temperature, pressure and percentage of fibers in the mixture as input parameters.

Photocatalysis and Plasma are widely considered as efficient and eco-friendly methods for the air treatment at domestic and industrial scales. In fact, the respective application of titanium dioxide (TiO2) and Dielectric-Barrier-Discharge(DBD) drew increasing attention in the last decades for their, flexible, non-selective and high efficiencies for the mineralization and the degradation of large selection of molecules. Nevertheless, the application of these techniques in separate conditions might generate undesired by-products that might hinder their treatment efficiencies. In this study, the effect of combining photocatalysis and Dielectric-Barrier-Discharge (DBD)techniques was investigated for the treatment of livestock building air at laboratory and industrial scale.. of Experiments were conducted in separate (i.e., Photocatalysis or plasma) and combined (i.e., Photocatalysis and plasma) systems to assess the degradation efficiency of two molecules, namely (NH3) and Propionaldehyde (ProPA) under various operating conditions. Studies onducted on laboratory scale showed a interesting level of treatment when applying either photocatalysis or plasma, with degradation yields reaching 29 and 36% for NH3 and 37 and 42% for ProPA, respectively. These degradation efficiencies were further enhanced when combining the processes, thus reaching 72 and 83% for NH3and ProPA, respectively. Moreover, investigations conducted on the generation of ozone during photocatalysis / Plasma treatment showed a decrease in the O3 concentration when compared to separate Plasma treatment. The photocatalytic degradation of ozone under UV radiation and in presence of TiO2 led to Low concentrations of ozone were detected at joint processas a consequence ofits catalytic decomposition under UV-light into HO2°, OH°,O2°-radicals at high humid conditions. The synergetic effect during the pollutant degradation was explained by the association of discharge plasma, presence of O3, UV-light and TiO2..Additionally,The implementation of the photocatalytic-plasma discharge reactor was performed to treat livestock sector air effluent loaded with ammonia.The effect of airflow and relative himidity were assessed. Results showed a significant NH3 removal efficiency in real conditions where it varied between59 and 75% for a flowrate of 2 m2/h and a relative humidity of 100%. Additonnlay, chemical and olfactometric studies were conducted to assess the performance of cimined sytem with real efflluent of livestock building air.

International audience; Freshwater supply is declining in the context of climate change, pollution, and soil salinization, calling for sustainable methods to produce drinking water. For instance, salt water can be converted into pure water by steam generation. Interfacial solar steam generation involves photoabsorbers consisting of a photothermal material with broad solar absorption and a porous substrate with a thermal insulating character. Nonetheless, scaling up of classical devices for interfacial solar steam generation is actually limited by cost, biofilm formation, salt fouling, complicated fabrication processes, and toxicity. Alternatively, wood-based devices are cheap, biodegradable, abundant, and display high fluxes of evaporation compared with other non-biodegradable photoabsorbers. Here we review the design and applications of wood-based solar steam generation devices, with focus on wood structure and properties, different types of devices, and factors controlling the evaporative performance.

International audience; Cyclohexane oxidation chemistry was investigated using a near-atmospheric pressure JSR at 570 K and ϕ = 0.8. Numerous intermediates including hydroperoxides and highly oxygenated molecules were detected using synchrotron vacuum ultraviolet photoelectron photoion coincidence spectroscopy. Supported by high-level quantum calculations the analysis of photoelectron spectra allowed the firm identification of molecular species formed during the oxidation of cyclohexane. Besides, this work validates recently published gas chromatography and synchrotron vacuum ultraviolet photoionization mass spectrometry data. Unambiguous detection of characteristic hydroperoxides (e.g. γ-ketohydroperoxides) and their respective decomposition products provide support for the conventional O2-addition channels up to the third addition and their relative contribution to the cyclohexane oxidation.The results were also compared to the predictions of a recently proposed new detailed kinetic model of cyclohexane oxidation. Most of the predictions are in line with the current experimental findings highlighting the robustness of the kinetic model. However, the analysis of the recorded slow photoelectron spectra indicating the possible presence of C5 species in the kinetic model provides hints that substituted cyclopentyl radicals from cyclohexyl ring opening might play a minor role in cyclohexane oxidation. Potentially important missing reaction are discussed.

International audience; Autothermal operation is a big challenge for a chemical looping combustion (CLC) demonstration plant. One of the key points of CLC autothermal operation is to achieve a high solid circulation rate and enough solid residence time. To address this challenge, a dedicated lifter is proposed to control the solid circulation rate and residence time in the dual fluidized bed reactor system. This dedicated lifter is integrated into a 1.5 MWth CLC cold flow model to evaluate the control of the solid circulation rate and residence time of this new CLC scheme. Continuous and stable circulation of solid particle operation is achieved in the cold flow model, and it has been demonstrated that the dedicated lifter can effectively control the solid circulation rate. The effect of gas velocity, bed inventory, and particle size on the fluidization in the whole loops is studied. The dedicated lifter can control the solid circulation rate in the range of 20–68 kg m–2 s–1, and residence time in the fuel reactor is maintained in the range of 180–610 s. The solid circulation rate and residence time obtained in this work satisfy the theoretical requirements of CLC autothermal and char gasification, respectively, which indicates that the autothermal operation of the CLC unit as well as high carbon capture efficiency can be realized in this new CLC scheme.

International audience; Macroscopic models for diffusion and heterogeneous reversible reaction of two species in porous media are developed by using coupled homogenization technique and spectral approach. Three representative cases related to the order of magnitude of the macroscopic Damköhler number DaL, namely predominating reaction, diffusion-reaction of the same order and dominating diffusion, are considered. The concentrations are developed as time series in an eigenfunctions basis associated with periodic spectral problems formulated in the unit-cell, thus forming a new microscopic problem to be homogenized. Such an approach represents a powerful tool to upscale diffusion-reaction microscopic problems, especially for high Damköhler number values where classical asymptotic development fails. It enables to capture the physics at very short times, when the characteristic time of reaction involved is much faster than the diffusion one. This work allows us to formulate the complex macroscopic laws describing the heterogeneous diffusion/reaction problem for two species in high Damköhler number regime.

International audience; Syngas biomethanation is a promising technology for waste to energy conversion. However, it had not yet been tested at high syngas flow rates. The aim of this study was to assess the possibility for syngas biomethanation to reach high methane productivity at higher syngas inflow rate. A pressurized stirred column was implemented. The syngas inflow rate was gradually increased, and two different increase strategies were compared. The highest methane productivity achieved yet with syngas-biomethanation was obtained, with 23.2 LCH4/L/d, with high conversion efficiencies of 89% for H2 and 82% for CO. The mass transfer performances of the process were investigated, and the existence of a biological enhancement factor was observed. Considering an enhancement factor in bioprocesses is a pioneering concept that could change the way we design bioreactor to improve mass transfer. The high methane productivity obtained in this study paves the way for the process industrialization.

Capturing and utilising carbon dioxide (CO2) is a major challenge for developing a low- carbon economy. In addition, the reduction of CO2 allows the synthesis of platform molecules for the chemical and energy industry. Anaerobic mixed cultures contain homoacetogenic microorganisms (HAC) capable of reducing CO2 to acetate. However, one of the obstacles to their use is the understanding and control of their functional diversity. In particular, managing the competition between HAC and hydrogenotrophic methanogens (HM) that convert CO2 into methane is crucial to selectively produce acetate.This study contributes to bring new knowledge on the competition between HAC and HM. In this sense, mass transfer between the gas phase where the substrates are located, and the liquid phase which contains the microbial catalysts, as well as kinetic and thermodynamic aspects of biological reactions have been integrated in this work. The microbial competition between HM and HAC was studied in successive batches. The effect of temperature between 25 °C and 35 °C was investigated, as well as the time of each batch, leading to different states of mass transfer limitation in the system. A clear effect of temperature between 25 °C and 35 °C on the outcome of the competition between HM and HAC was highlighted, as well as the effect of mass transfer limitation. This study contributes to identify specific process parameters influencing the selection of HAC over HM and should help in the design of experiments depending on the target product from H2/CO2.In successive batches, lifting of mass transfer limitation, as well as lowering of the temperature to 25 °C made it possible to select HAC in mixed anaerobic cultures for acetate production by eliminating the methanogens, after four successive batches of 4 to 6 days each.

For approximately five decades, bulk niobium resonators have been the best RF accelerating cavities available for accelerators. Thanks to the huge research efforts made by the SRF community, niobium cavities provide today reliably exceptional performances with accelerating gradient up to 40 MV/m. Nonetheless, niobium cavities still witness performance limitations when exposed to high fields which are essentially due to current vortices that appear in the superconductors when a magnetic field is applied. These vortices start dissipating energy and creating heat as soon as they are set to motion by the RF field. Moreover, their interactions with native oxides and the material defects drastically demeans superconducting performances. This work aims at exploring a new technological pathway to enhance the performances of SRF cavities through functionalizing their inner surface with thin film coatings. Due to its complex shape, coating an SRF cavity demands a finetuning of the film’s chemical and structural properties and a thickness uniformity down to the nanometric scale. To our knowledge, atomic layer deposition is a very well suited deposition technique to fulfill these requirements. This Project is a synergistic approach between synthesis, characterization and performance tests of the most effective ALD deposited thin films to address some of the most detrimental phenomena to RF cavities operation and to explore new technological routes to boost their performances.; Depuis environ cinq décennies, les résonateurs en niobium massif ont été les meilleures cavités radiofréquences disponibles pour les accélérateurs. Grâce aux énormes efforts de recherche fournis par la communauté SRF, les cavités en niobium offrent aujourd'hui des performances exceptionnelles et fiables avec des gradients accélérateur allant jusqu'à 40 MV/m. Néanmoins, les cavités en niobium connaissent encore des limitations de performances lorsqu'elles sont exposées à des champs élevés qui sont essentiellement dus aux tourbillons de courant qui apparaissent dans les supraconducteurs lorsqu'un champ magnétique est appliqué. Ces tourbillons commencent à dissiper de l'énergie et à créer de la chaleur dès qu'ils sont mis en mouvement par le champ radiofréquence. De plus, leurs interactions avec les oxydes natifs et les défauts du matériau dégradent considérablement les performances supraconductrices. Ce travail vise à explorer une nouvelle voie technologique pour améliorer les performances des cavités SRF en fonctionnalisant leur surface interne avec des revêtements en couches minces. En raison de sa forme complexe, le revêtement d'une cavité SRF nécessite un contrôle fin des propriétés chimiques et structurelles du film et une uniformité d'épaisseur jusqu'à l'échelle nanométrique. Le dépôt par couche atomique (ALD) est une technique de dépôt particulièrement adaptée pour répondre à ces exigences. Ce projet est une approche synergique entre la synthèse, la caractérisation et les tests de performance sur cavités recouvertes par ALD de couches minces les plus efficaces pour traiter certains des phénomènes les plus limitants au fonctionnement des cavités RF et pour explorer de nouvelles voies technologiques pour améliorer leurs performances.

International audience; Biological methanation is an emerging Power-to-Gas technology that provides a flexible, efficient, and long-term storage system to address the renewable energy intermittency issue. However, scaling-up a biological methanation plant requires overcoming the bottleneck of H2 gas–liquid mass transfer. The current work demonstrates analytically, experimentally and numerically the importance of H2 mass transfer on CH4 purity and productivity. The influence of sparger design was investigated in a pilot-scale bubble column bioreactor. An increase of 265 % in kLa and subsequently 81 % in CH4 purity is obtained when a uniform porous plate is used over a 4-points porous sparger. Numerical simulation of the bioreactor was performed using a multiscale modeling approach coupling 1D and CFD models. The numerical simulations were validated satisfactorily by the experimental data. Parametric studies were also performed using the 1D model to reveal the impact of operating conditions on the bioprocess. An analytical solution for the productivity of biomethanation reactors at steady-state is proposed based on mass balances and provides new insights into biological methanation. It is found that any modification of operating parameters that improve H2 mass transfer, such as higher gas recirculation rate and smaller bubble size, leads to a better bioreactor performance.

International audience; All-solid-state lithium metal batteries (ASSLMBs) have received much attention because of their potential for high energy density and high safety performance. However, the poor compatibility of the lithium/solid electrolytes (SEs) interface and the penetration of lithium dendrites during cycling prevent them from achieving current densities that are capable of commercialization. In this work, a lithium-metastable solid electrolyte and a lithium-unstable solid electrolyte have been mixed to obtain mix-structured solid electrolyte. In particular, Li5.5PS4.5Cl1.5 acts as a lithium-compatible matrix, and Li10SnP2S12 as a dendrite-scavenger. The synergy between the two generates a stable interface with the Li anode and effectively suppresses the penetration of lithium dendrites. Li symmetric cells can operate stably for 160 h at a current density of 0.5 mA cm-2 at room temperature. The critical current density can reach 5 mA cm-2 and the overpotential is less than 0.5 V. The Li/SEs/Li4Ti5O12 all-solid-state cells show a high capacity of 174 mAh g-1 at 0.2 C and 148 mAh g-1 at 2 C. High-capacity retentions of 97.3% and 94.4% are shown after 75 cycles at 1 C and 2 C at room temperature, respectively. This work highlights the advantages of the electrolyte with mixed structure and provides a new strategy to resist lithium dendrites and improve the critical current density and cycle life of ASSLMBs.

International audience; The fluidization of short Hi Nicalon S fibers was investigated before considering CVD coatings with controlled composition and thicknesses. The fluidization of a short fiber batch alone being delicate and not reproducible, the study consisted in comparing the hydrodynamic behavior of a powder alone, to that of a short fiber/powder mixture. The fluidization behavior of the particle beds was studied by following their pressure drop as a functionof pressure and temperature. The minimum fluidization velocity (U$_{mf}$) was evaluated at room temperature (T$_{amb}$) at different reduced pressures, and at 200 mbar as a function of temperature. The results are in good agreement with the theoretical equations. At low pressures and T$_{amb}$, U$_{mf}$ increases rapidly. In contrast, U$_{mf}$ varies only slightly with temperature. While the pressure does not seem to affect the fluidization behavior of the powder alone, it displays a clear optimum at 200 mbar for the short fiber/powder mixture.

International audience; The prediction of solvation quantities is an important issue in several fields of chemical and process engineering. In this regard, this work was conducted to increase the prediction power of the equation-of-state (EoS) approach by coupling the tc-PR (translated-consistent Peng-Robinson) EoS with COSMO-RS (Conductor-like Screening Model for Real Solvents) as gE model through an advanced mixing rule. Since the only input parameter of the COSMO-RS model is the charge density (σ) profile of each molecule, the resulting EoS (called tc-PR/COSMO-RS) does not require any binary interaction parameter contrary to other predictive cubic EoS, such as VTPR, PPR78, PSRK, and UMR-PRU. This feature allows the quantification of solvation data of a great number of systems from readily available pure-component properties (critical temperature and pressure, acentric factor and σ -profile). Satisfactory results were obtained for the prediction of solvation Gibbs energy data that were extracted from the extensive CompSol database (the average absolute deviation is 0.30 kcal/mol). The proposed model represents a very flexible alternative for the prediction of solvation data, since it can deal with a large variety of solutes in either a pure or mixed solvent, and for the entire phase diagram (including the supercritical region).

International audience; The capability of supercritical CO2 to extract edible oil from handmade Argan press cake was investigated. The aim is to enable Moroccan cooperatives to improve their economic situation by valuing the handmade argan press cake, which is nowadays considered as a waste, applying a clean extraction process. Extraction experiments were conducted at 300 and 400 bar, 333 K and 0.14 kg/h on dried biomass. The fatty acids and tocopherols compositions of the extracted oil were found similar to previous studies and correspond to a commercial edible oil. The air flow dried biomass exhibits a higher extraction yield compared to the freeze-dried biomass. A pressure of 300 bar seems to be suffcient to allow the extraction of oil with a satisfactory extraction kinetic.

The objective of this study was to evaluate the antioxidant (AA), antibacterial, and antifungal activity of fresh and pre-treated apricot extracts, dried by microwave at different powers (200, 400, and 800 W), extracted by the cold soaking method, and ultrasound-assisted extraction (UAE). Biological activity (bacterial and fungal) was estimated by agar disk diffusion test against four bacterial strains (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Streptococcus sp.), and two fungal strains (Candida spp. and Geotrichum capitatum). Methanolic extracts of apricot fruits: fresh, dried processed, and apricot dough extracted by cold soaking showed a higher AA ranging from 34.22 to 96 % than the other extracts extracted by UAE with values ranging from 14.37 to 66.88 %. The results of tested extracts from fruits (Prunus armeniaca L.) extracted by both extraction methods showed the highest inhibitory activity against most of the tested bacterial and fungal strains with inhibition zones ranging from 4 to 45 mm. The biological activity (antibacterial and antifungal activity) has been improved using different treatments and microwave powers for drying apricots. In addition, the results of the biological activity of the extracts obtained by UAE are the best compared to cold soaking. However, it was determined that the UAE extraction method of cold soaking and drying of apricot fruits was more appropriate for the food industry due to the obtaining of extracts with good antibacterial and antioxidant potential, and their incorporation in foods would increase their production and uses, thus leading to the development of superior biofunctional foods, and the use of bio-solvent, such as methanol, which is easily available in high purity, highly safe, and completely biodegradable., Cilj ovog istraživanja bio je procijeniti antioksidativno, antibakterijsko i antifungalno djelovanje ekstrakata svježih i obrađenih marelica (Prunus armeniaca L.), sušenih u mikrovalnoj pećnici pri različitim snagama (200, 400 i 800 W), dobivenih metodom hladnog namakanja i ekstrakcijom potpomognutom ultrazvukom. Biološka aktivnost (antibakterijska i antifungalna) procijenjena je difuzijskim testom na agar disku koristeći četiri bakterijska soja (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus i Streptococcus sp.) i dva gljivična soja (Candida spp. i Geotrichum capitatum). Metanolni ekstrakti svježih i sušenih plodova te tijesta marelice dobiveni hladnim namakanjem pokazali su antioksidativno djelovanje u rasponu od 34,22 do 96 %, što je više od ekstrakata dobivenih ekstrakcijom potpomognutom ultrazvukom s vrijednostima u rasponu od 14,37 do 66,88 %. Ekstrakata iz plodova marelice dobiveni objema ekstrakcijskim metodama pokazali su najveću inhibitornu aktivnost prema većini ispitivanih sojeva bakterija i gljiva sa zonama inhibicije u rasponu od 4 do 45 mm. Biološka aktivnost (antibakterijska i antifungalna) poboljšana je primjenom različitih intenziteta sušenja marelica. Osim toga, rezultati biološke aktivnosti ekstrakata dobivenih ekstrakcijom potpomognutom ultrazvukom bolji su u usporedbi s hladnim namakanjem.

This study was carried out to verify the influence of drying parameters on phenolic and flavonoid compounds of apricots (Prunus armeniaca L.) treated with sucrose, NaCl, and sodium bisulphite solutions dried by microwave at different powers (200, 400, and 800 W). We used two extraction methods, namely, cold soaking and ultrasound-assisted extraction (UAE). Total phenolics and flavonoids in fresh and dried apricots and apricot dough were estimated using the Folin-Ciocalteu reagent and the aluminium trichloride method, respectively. Fresh apricot contained considerable amounts of polyphenols and flavonoids by the cold soaking and UAE (285.43 and 165.49 mg GAE/100 g DM and 48.57 and 12.11 mg QE/100 g DM, respectively). Analysis of the data showed that the decrease in polyphenol and flavonoid contents of the dried treated apricots compared to the fresh material was significant. The greatest losses of these nutrients were recorded when applying the ultrasonic extraction method., U ovom radu ispitan je utjecaj parametara sušenja na fenolne i flavonoidne spojeve marelica (Prunus armeniaca L.) tretiranih otopinama saharoze, natrijeva klorida i natrijeva bisulfita te sušene u mikrovalovoj pećnici pri različitim snagama (200, 400 i 800 W). Primijenjene su dvije metode ekstrakcije, hladno namakanje i ekstrakcija potpomognuta ultrazvukom (UAE). Ukupni fenoli u svježim i suhim marelicama te tijestu marelica određeni su primjenom Folin-Ciocalteu reagensa, dok su flavanoidi određeni metodom s aluminijevim(III) kloridom. Obje metode ekstrakcije pokazale su da je svježa marelica sadržavala znatne količine polifenola i flavonoida. U suženim marelicama zabilježene su znatno manje količine polifenola i flavanoida. Najveći gubici tih nutrijenata zabilježeni su prilikom primjene ekstrakcije potpomognute ultrazvukom.

International audience; To address the problem of pollution caused by antibiotics in black water, we synthesized membranes containing the g-C3N4/TiO2 photocatalysts and tested them for the removal of sulfamethoxazole and tetracycline in pure water conditions and black water. We compared the basic membrane filtration and photocatalytic performance of the g-C3N4/TiO2 and the PVDF membranes, and investigated the influencing factors and application aspects of membrane filtration-photocatalytic systems for antibiotic removal. The anti-fouling performance and re-usability of g-C3N4/TiO2 membranes were investigated by evaluating the fouling reversibility of photocatalytic membranes. The results showed that g-C3N4/TiO2 improved the porosity, hydrophilicity and permeability of the membranes significantly. PgT-3 (PVDF/g-C 3 N 4 /TiO 2) membrane with 0.03 wt% of g-C3N4/TiO2 has the best overall performance with 72.8 % and 63.9 % removal efficiency for sulfamethoxazole and tetracycline respectively. Neutral or weakly acidic solution (pH = 5.0-7.0) is favorable for the removal of both study antibiotics. The complex composition of black water increased the adsorption load on the membrane and caused the inhibition of the photocatalysis of the g-C3N4/TiO2 membrane. The absorption of visible light by g-C3N4 accelerates the electron transfer rate and promotes the separation of electrons from holes. The oxidation-active substance h + produced in the system plays an important role in the removal of sulfamethoxazole and tetracycline.

International audience; Switchable solvents are changing properties when exposed to an external stimulus. As example, for thermomorphic multiphasic system (TMS), temperature changes can induce phase separations. Aqueous systems presented here are formulated with a carboxylic acid (weak acid) and an amphiphilic tertiary amine (weak base). They show thermo-switchable hydrophobicity and after separation, the weak acid and base are mainly found in the organic phase while the aqueous phase is mostly composed of water, up to 99 wt%. The phase separation temperature (cloud point) can be tuned from 20 to 80 °C depending on the choice of the carboxylic acid and on the acid: base molar ratio. A collection of saturated aliphatic carboxylic acids and benzoic acid derivatives have been investigated to evaluate the impact of different physico-chemical properties on the cloud point. The octanol/water partition coefficient (log P) and acidic constant (pKa) were identified as key physico-chemical properties to adjust the phase separation temperature. Finally, as illustration of the efficiency of these systems to remove a chemical from water, it has been shown that 99 % extraction of an anionic dye, methyl orange, could be achieved with most of the tested TMS.

International audience

The current work studies the reductive catalytic depolymerization (RCD) of lignin from a novel semi-industrial process. The aim was to obtain aromatic mono-, di-, tri-, and tetramers for further valorization. The substrate and products were characterized by multiple analytical methods, including high pressure size-exclusion chromatography (HPSEC), gas chromatography-mass spectrometry, GC-flame ionization detector (FID), GC-FID/thermal conductivity detector (TCD), and NMR. The RCD was studied by exploring the influence of different parameters, such as lignin solubility, reaction time, hydrogen pressure, reaction temperature, pH, type and loading of the catalyst, as well as type and composition of the organic/aqueous solvent. The results show that an elevated temperature, a redox catalyst, and a hydrogen atmosphere are essential for the depolymerization and stability of the products, while the reaction medium also plays an important role. The highest obtained mono- to tetramers yield was 98% and mono- to dimers yield over 85% in the liquid phase products. The reaction mechanisms influenced the structure of the aliphatic chain in the monomers, but left the phenolic structure along with the methoxy groups largely unaltered. The current work contributes to the development and debottlenecking of the novel and sustainable overall process, which utilizes efficiently all the fractions of wood, in line with the principles of green engineering and chemistry.

The future of combustion processes lies on a significant reduction of pollutant emissions, as well as increased efficiencies. The control of the ignition phase is a critical step towards this goal, in many different configurations. Whatever the application, reproductible initiation of the combustion phase is sought. It is well known that the fuel ignition is largely dependent on low-temperature combustion (LTC) mechanisms, responsible for the occurrence of cool flames. These mechanisms involve the formation and decomposition of highly reactive intermediates, peroxides, whose structure reflect the initial fuel structure. Therefore, the fuel structure strongly influences its reactivity. Furthermore, the widespread use of bio-based or synthetic fuels requires a detailed understanding of their reaction pathway in this temperature domain, which may differ from those of fossil fuels. Finally, following the recent demonstration of easier cool flame ignition through the use of dielectric barrier plasma discharge or ozone-seeding stresses the need for fundamental studies on these low-temperature combustion kinetics. Within this work performed at the PC2A laboratory, a stagnation plate burner dedicated to the low-temperature combustion kinetics studies of fuels inside stabilized cool flames was developed and characterized.The detailed chemical structures of cool flames were established by coupling different analytic and optical techniques, namely formaldehyde Planar Laser Induced Fluorescence (CH2O-PLIF), excited formaldehyde chemiluminescence, temperature measurements by thermocouple, (micro-) gas chromatography and mass spectrometry. Three different fuels were selected in this work: dimethyl ether (DME), diethyl ether (DEE) and oxymethylene ether-2 (OME-2). Cool flames were generally stabilized under lean conditions (varying between 0.2 and 0.5) by means of ozone-seeding (varying between 1 and 2% mol. of the mixture), except for diethyl ether, for which a stoichiometric self-sustaining cool flame was investigated without ozone-addition. Comparing measured and simulated cool flames chemical structures, using various detailed kinetic mechanisms from the literature, allowed to assess the performance of these models in these specific conditions. Furthermore, the ozone influence as in-situ radical provider was investigated. While its use only slightly affects the products distribution downstream of the cool flame, this species highly impacts some reaction pathways in the cool flame, promoting chain-propagating over chain-branching reactions.Finally, Particle Image Velocimetry (PIV) technique was used in the stagnation plate burner configuration, allowing the measurement of cool flames laminar burning velocities (LBVs) at atmospheric pressure for the first time. The LBV is an intrinsic data of the fuel, depending on the initial mixture composition, temperature and pression. This data is particularly valuable for kinetic studies, but was almost never investigated in the case of cool flames. Its measurement was successfully achieved inside lean, ozone-seeded dimethyl ether cool flames, the experimental propagation speeds varying between 14 and 18 cm.s-1. This study notably allowed to highlight the most important reactions for the prediction of cool flames LBVs.The newly acquired data in this work constitute a strong foundation to further work on the low-temperature combustion mechanisms in the presence of ozone, in novel experimental conditions complementary to those met in typical kinetic reactors.; L'avenir des processus de combustion est tributaire d'une réduction significative des émissions polluantes, ainsi que de l'augmentation des rendements énergétiques. Le contrôle de l'initiation de la combustion est une étape critique dans cette direction, et ce dans de nombreuses configurations. Quelle qu'en soit l'application, l'initiation reproductible de la phase de combustion est recherchée. Cependant, l'initiation de l'inflammation des carburants est largement dépendante des mécanismes chimiques de basses températures, dits LTC (Low-Temperature Combustion), responsables de la formation de flammes froides. Ces mécanismes impliquent la formation et décomposition de composés hautement oxygénés instables, des peroxydes, dont la structure reflète celle du carburant initial. Celle-ci conditionne donc fortement sa réactivité. De plus, la généralisation de carburants biosourcés ou de synthèse nécessite une compréhension fine de leurs chemins réactionnels, ceux-ci pouvant être spécifiques aux fonctions chimiques absentes des carburants fossiles. Enfin, les récentes démonstrations de la facilitation de l'initiation d'une flamme froide par interaction avec un plasma froid ou par ensemencement d'ozone souligne le besoin d'études fondamentales de ces mécanismes chimiques de combustion de basses températures. Dans le cadre de cette thèse effectuée au laboratoire PC2A, un brûleur à plan de stagnation dédié à l'étude de la cinétique des flammes froides a été conçu et caractérisé.La structure chimique détaillée de flammes froides est obtenue par la mise en commun de différentes techniques analytiques et optiques, respectivement la fluorescence induite par plan laser du formaldéhyde, la chimiluminescence du formaldéhyde excité, la mesure de température par thermocouple, l'analyse chimique par (micro-)chromatographie en phase gaz et spectrométrie de masse. Trois carburants ont été sélectionnés, respectivement le diméthyl éther (DME), le diéthyl éther (DEE) et l'oxyméthylène éther-2 (OME-2). Les flammes froides étudiées sont généralement stabilisées à basse richesse (0.2 < E.R. < 0.5) à l'aide d'ajout d'ozone (variant entre 1 et 2% mol. du prémélange), à l'exception du diéthyl éther, où une flamme froide a été stabilisée à la stœchiométrie sans ozone. L'établissement de structures détaillées de ces flammes froides a notamment permis, lorsque comparées aux prédictions de divers modèles cinétiques, de constater les manques de certains de ces modèles quant à la prédiction de la réactivité dans ces conditions spécifiques. De plus, l'influence de l'ozone comme générateur de radicaux in-situ a été étudié. Bien que son utilisation n'affecte que marginalement la composition chimique après la flamme froide, son influence est importante sur certains branchements de réactions primordiaux à basses températures, favorisant les réactions de propagation par rapport à celles de branchement.Finalement, l'utilisation de la Vélocimétrie par Imagerie de Particules (PIV - Particle Image Velocimetry) dans le brûleur à plan de stagnation a permis, pour la première fois, la mesure de la vitesse de propagation de flammes froides à pression atmosphérique. Cette donnée, intrinsèque au carburant étudié, dépendant des composition, température et pression du mélange initial, est particulièrement importante pour la modélisation cinétique de systèmes réactifs. L'utilisation de flammes froides de DME ensemencées à l'ozone a permis sa mesure à basse richesse, les vitesses de propagation mesurées variant entre 14 et 18 cm.s-1. Cette étude a notamment permis de mettre en lumière les réactions les plus importantes pour la prédiction d'une telle grandeur.Les nouvelles données expérimentales obtenues dans le cadre de ces travaux de thèse constituent les fondations de travaux plus larges sur l'influence de l'ozone sur la chimie de basses températures, dans des conditions expérimentales originales et complémentaires de celles généralement étudiées en laboratoire.

In France, High-level nuclear wastes are vitrified. The resulting packages will eventually be stored in a deep geological formation. After corrosion of the canister and overpack, the groundwater will interact with the glass, resulting in the mobilization of soluble radionuclides. Therefore, researchers must design the glass with an optimal composition and durability to limit the radionuclides release in the environment. Al is an important constituent of nuclear waste glasses; however, its role on glass durability remains somewhat of a mystery! During the initial dissolution regime, at low concentration in the glass, it increases the resistance to hydrolysis of the glass, whereas at high concentration, an opposite effect is observed. To understand this phenomenon, we performed a large number of Molecular Dynamics simulations coupled with the potential mean force technique (PMF) to estimate the activation barriers for hydrolysis of cation-oxygen bonds in pure silica and in alumino silicate glasses. In parallel, experiments were performed to validate the simulation results. This study revealed that the Al-O bonds are easier to dissociate than the Si-O bonds. However, Al increases the glass chemical durability by significantly increasing both the strength of the Si-O bonds and network connectivity in alumino silicate glass.In contrast, at high Al concentration, preferential dissolution of Al weakens the silicate network because of the percolation of the weak Al-O bonds, so the glass resistance becomes poor. Through PMF calculations, we evaluated the activation barriers for dissociating bonds around Al as 0.49 eV, which is less than half of the energy to dissociate bonds around Si in pure silicate (1.22 eV) and around Si in aluminosilicate glass (1.34 eV). We have shown that these energy differences are statistically significant. Molecular structural investigation revealed that Si with Al as a second neighbor in the glass network has significantly higher activation energy for dissociation than Si in pure silicate glass. Then the strengthening of the Si-O bonds when Al is present in the glass is mainly a local effect. The role of Al in strengthening the Si is qualitatively validated by ReaxFF calculations, another molecular modelling technique but more precise. Then we have continued the investigations with glasses containing Ca or Na. Mixing both Ca and Na in aluminosilicate glass made the strengthening effect of Si by Al insignificant because the strengthening effect is compensated by an increase of the structural disorder.Finally we have investigated the role of Al during the residual alteration rate. For this, we designed six sodium borosilicate glasses with varying concentrations of Al2O3 from 0% up to 9.6 wt%. Three glasses have small to no Al content, and the three other glasses have higher Al contents. It is observed that glasses with small quantities of Al2O3 quickly released a large amount of Si into the solution. On the other hand, glasses with a larger quantity of Al2O3 released less amount of Si. This is because the Al content controls Si release into the solution under dilute conditions. Eventually, the solution is saturated with Si, and the glass develops a protective layer on its surface.A new Monte Carlo model was developed to reproduce and better understand these experimental results. Glasses releasing more Si into the solution favored the formation of a thick Si-enriched layer on the gel surface in contact with water. By investigating experimentally the alteration layer of one of the six glasses by ToF-SIMS, we observed that B begins to be retained in the young gel developed during one month. This retention is correlated to the decrease of the residual alteration rate. By coupling Monte Carlo simulations and experiments, it is proposed that the formation of an external layer enriched in Si induces B retention in the gel, which, in turn, could limit further glass alteration.; En France, les déchets nucléaires de haute activité sont vitrifiés. Ils seront à terme stockés en formation géologique profonde. Après corrosion des enveloppes métalliques, l’eau souterraine arrivera au contact du verre et interagira chimiquement avec ce dernier, conduisant à la mobilisation des radionucléides solubles. Il est donc important de définir des verres avec des compositions et des durabilités optimales pour limiter ce relâchement. L’aluminium est un constituant majeur des verres nucléaires. Mais son rôle sur l’altération est encore mal compris. Pendant la phase de régime initial, à faible concentration, il conduit à accroître la résistance du verre à l’hydrolyse, alors qu’à plus forte concentration, un effet opposé est observé. Pour comprendre ce phénomène, nous avons réalisé un grand nombre de simulations de dynamique moléculaire, couplées à la technique de “Potential Mean Force” (PMF) pour estimer les barrières d’activation pour l’hydrolyse dans la silice pure et dans des verres d’alumino-silicates. En parallèle, des expériences ont été faites pour valider les simulations. Cette étude a révélé que les liaisons Al-O sont aisément dissociables comparées aux liaisons Si-O. Cependant la présence de Al augmente significativement la durabilité du verre en renforçant les liaisons Si-O et en augmentant la connectivité du réseau vitreux.Au contraire, à plus forte concentration, la dissolution préférentielle des Al affaiblit le réseau silicaté en raison de la percolation des liaisons faibles Al-O. La résistance du verre à l’altération s’affaiblit. Grâce à la technique PMF, nous avons évaluer à 0.49eV l’énergie d’activation moyenne pour l’hydrolyse des liaisons autour des Al, ce qui représente moins de la moitié de l’énergie nécessaire pour dissocier les liaisons autour des Si dans la silice pure (1.22eV) ou dans un verre alumino-silicaté (1.34eV). Nous avons montré que ces différences d’énergie sont statistiquement significatives. Cet effet est un processus principalement local. Des calculs de dynamique moléculaire par la méthode ReaxFF ont permis de valider les résultats. Nous avons poursuivi les investigations avec des verres contenant du Ca et du Na. Le mélange Ca/Na dans un verre alumino-silicaté conduit à rendre insignifiant le renforcement des liaisons Si-O par le Al du fait de la compensation de cet effet par l’accroissement du désordre structural.Finalement, nous avons étudié le rôle du Al pendant la phase d’altération résiduelle, c’est-à-dire quand un gel passivant se forme. Pour cela, six verres d’alumino-borosilicate avec des teneurs variables en Al2O3 (de 0% à 9.6% massiques) ont été préparés. Trois verres contiennent une concentration en Al2O3 faible voire nulle et les trois autres ont des concentrations en Al2O3 plus élevées. Les verres avec de faibles quantités de Al2O3 relâchent rapidement une grande quantité de Si en solution. En revanche, les verres avec une quantité plus importante de Al2O3 relâchent moins de Si. Ceci confirme le contrôle du relâchement des Si en solution en conditions diluées par le Al. Au final, quand la solution devient saturée en Si, une couche protectrice se forme à la surface du verre.Un nouveau modèle Monte Carlo a été développé pour reproduire et mieux comprendre ces résultats expérimentaux. Les verres relâchant davantage de Si en solution forment une couche épaisse enrichie en Si à la surface du gel en contact avec l’eau. En analysant expérimentalement le couche d’altération de l’un des six verres par Tof-SIMS, nous avons observé que le B, élément soluble et généralement traceur de l’altération est partiellement retenu dans le gel formé après un mois de réaction. Cette rétention est corrélée à la décroissance de la vitesse d’altération. En couplant les simulations Monte Carlo et les expériences, il a été proposé que la formation d’une couche externe enrichie en Si conduit à la rétention du B dans le gel, ce qui, à son tour, pourrait limiter la poursuite de l’altération.

The formation of soot particles in combustion is a major research issue due to their negative impact on our health and our environment. The link between the inhalation of these particles and certain pathologies affecting mainly the respiratory tract is indeed well established and it is also proven that these particles have an impact on climate change. For these reasons, their emission rate from devices involving combustion processes (aircraft engines, thermal or hybrid engines of land or sea vehicles, wood boilers...) is increasingly regulated. However, the state of the art concerning the formation mechanisms of soot particles reveals many deficiencies, notably regarding the nature of the chemical species and reaction pathways involved. The nucleation step, which is the crucial step of these mechanisms since it corresponds to the transformation of gaseous precursors into soot particles, raises many questions and interrogations. Currently, several hypotheses are considered in the literature involving in particular the formation of polycyclic aromatic hydrocarbons (PAHs) and potentially that of intermediate species (PAH dimers, resonantly stabilized radicals of PAHs) between PAHs and soot particles. However, there is very little direct experimental evidence in the literature on the formation of these compounds in flames.The work carried out in this thesis focused on the characterization of the key species involved in the soot nucleation process in a methane diffusion flame. In that context, we have implemented a set of in situ and ex situ experimental methodologies (ToF-SIMS, Raman, LII, LIF and EPR) which have allowed us to obtain a large panel of experimental data able to provide relevant and innovative information on the main molecular species and reaction pathways involved in the nucleation process. The coupling of these different methods and the analysis of the obtained data, in particular by means of multivariate data analysis, reveals important correlations between the nucleation process and the successive formation of different species (PAHs, resonance stabilized radical of PAHs, incipient soot particles, mature particles). This work brings crucial information on the size, mass, structure and nature of the species involved and their evolution in the nucleation process, which will allow the development of kinetic models and significantly improve our knowledge of this complex physicochemical process.; La formation des particules de suie dans les processus de combustion est une problématique de recherche majeure du fait de l'impact négatif de ces composés sur notre santé et notre environnement. Le lien entre l'ingestion de ces particules et certaines pathologies touchant principalement les voies respiratoires est en effet bien établi et il est également avéré que ces particules ont un impact sur le changement climatique. C'est pourquoi leur taux d'émission au sortir de dispositifs mettant en jeu des processus de combustion (réacteurs d'avions, moteurs thermiques ou hybrides des véhicules terrestres ou maritimes, chaudières à bois…) est de plus en plus règlementé. Or, l'état de l'art concernant ces mécanismes chimiques fait apparaître de nombreuses carences notamment dans la nature des espèces chimiques impliqués et des voies réactionnels mises en jeu. Plus particulièrement, l'étape de nucléation, qui est l'étape cruciale de ces mécanismes puisqu'elle correspond à la transformation des précurseurs gazeux en particules de suie, soulèvent de nombreuses questions et interrogations. Actuellement, plusieurs hypothèses sont envisagées dans la littérature mettant notamment en jeu la formation d'hydrocarbures aromatiques polycycliques (HAPs) et potentiellement celle d'espèces intermédiaires (dimères de HAPs, HAPs radicalaires stabilisés par résonance) entre les HAPs et les particules. Cependant, il n'existe que très peu de mesures directes ou de preuves expérimentales de la formation de ces composés dans les flammes.Le travail de cette thèse a porté sur la mise en évidence et la caractérisation des espèces clefs impliquées dans le processus de nucléation des particules de suie dans une flamme de diffusion de méthane. Dans le cadre cette étude, nous avons mis en œuvre un ensemble de dispositifs expérimentaux in situ et ex situ (ToF-SIMS, Raman, LII, LIF et RPE) qui ont permis l'obtention d'un large panel de données expérimentales à même d'apporter des informations pertinentes et novatrices sur les principales espèces moléculaires et voies réactionnelles impliquées dans le processus de nucléation. Le couplage de ces différentes méthodes et l'analyse des données obtenues, notamment au moyen de la méthode PCA, fait apparaître un séquençage du processus de nucléation corrélé à la formation successive de différentes espèces (HAPs, HAPs radicalaires stabilisés par résonance, particules de suie naissantes, particules matures). Ce travail apporte des informations cruciales sur la taille, la masse, la structure et la nature des espèces impliquées et leur évolution dans le processus dans le processus de nucléation, de nature à permettre le développement de modèles cinétiques et améliorer sensiblement nos connaissances de ce processus physicochimique complexe.

This work uses small angle neutron scattering and electrochemical characterizations to study the structure and properties of ionomer in proton exchange membrane fuel cell (PEMFC) electrodes. The final objective of this thesis is to establish the link between ionomer degradation and the decrease of electrochemical performances. Small Angle Neutron Scattering (SANS) allows to study the electrode structure for characteristic sizes ranging from the nanometre to several hundreds of nanometres. The analysis method developed in this thesis gives access to the distribution of the ionomer, the size of the primary carbon particles and their porous structure as well as the adsorption and localization of water in the electrode. The analysis of SANS profiles shows that the ionomer disperses as a thin film of 1.5 to 2.5 nm thickness on the surface of the Pt/C catalyst, or forms aggregates (>50 nm) depending on the electrode fabrication process. Electrochemical characterizations are developed to study the role of the ionomer in the electrode operation. Measurements of performance, electrochemical impedance spectroscopy, double layer capacitance, CO oxidation and proton desorption are carried out. These measurements underline the importance of adsorbed water on the surface of the Pt/C catalyst for proton transport and show that the ionomer allows to keep water in the vicinity of active sites at low relative humidity. However, ionomer limits the accessibility of platinum to the gas, or even prevents it completely. SANS and electrochemical measurements are applied to new and aged electrodes to study the impact of aging on the properties and structure of the ionomer. The degradation of protonic conductivity in the electrode contributes to the drop in performance and seems to be related to the degradation of the chemical structure of the ionomer.; Ce travail de thèse utilise la diffusion de neutrons aux petits angles et les caractérisations électrochimiques pour étudier la structure et les propriétés du ionomère dans les électrodes de pile à combustible à membrane échangeuse de protons (PEMFC). L'objectif final de cette thèse est de faire le lien entre la dégradation du ionomère et la diminution des performances électrochimiques. La diffusions de neutrons aux petits angles, ou SANS pour Small Angle Neutron Scattering, permet d'étudier la structure de l'électrode pour des tailles caractéristiques allant du nanomètre à plusieurs centaines de nanomètres. La méthode d'analyse développée dans cette thèse permet d'accéder à la distribution du ionomère, aux taille des particules primaires de carbone et à leurs porosités ainsi qu'à l'adsorption et à la localisation de l'eau dans l'électrode. L'analyse des profils met en évidence que le ionomère se disperse en film fin de 1,5 à 2,5 nm d'épaisseur à la surface du catalyseur Pt/C, ou forme des agrégats (>50 nm) en fonction du procédé de fabrication des électrodes. Des caractérisations électrochimiques sont développées pour étudier le rôle du ionomère dans le fonctionnement de l'électrode. Des mesures de performances, de spectroscopie d'impédances électrochimiques, de capacité de double couche, d'oxydation de CO et de désorptions de protons sont mises en œuvres. Ces mesures soulignent l'importance de l'eau adsorbé à la surface du catalyseur Pt/C pour le transport des protons et montrent que le ionomère permet de conserver de l'eau à proximité des sites actifs aux faibles humidités relatives mais qu'il limite l'accessibilité du platine au gaz, voir l'empêche complétement. Les mesures SANS et électrochimiques sont appliquées à des électrodes neuves et vieillis pour étudier l'impact du vieillissement sur les propriétés et la structure du ionomère. La dégradation de la conduction protonique dans l'électrode contribue à la chute des performances et semble reliée à la dégradation de la structure chimique du ionomère.

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The multiple aims of this thesis fall within the implementation of a new HT-SMART-FORMU technological platform dedicated to formulation science. The focus is set on the development of reliable experimental methods, theoretical and predictive tools, so as to establish relations between chemical composition, physicochemical properties and applicative properties.The first type of systems investigated in this work consists of solid dispersions. Their stability has long been approached by the DLVO theory, but more recent studies suggest the use of Hansen Solubility Parameters to describe their stability in non-aqueous media. In the first chapter, a systematic analytical method based on zeta potential measurement and light scattering stability monitoring allows deducing a complementarity of both theories to describe the stability of TiO2 dispersions in non-aqueous solvents.The problematic of oil hydrophobicity prediction through EACN values modelling, which is a key parameter to design surfactant/oil/water (SOW) dispersed systems, is addressed in the second chapter. Two mathematical models, designed using machine-learning methods, are proposed for the rapid prediction of the EACN of oils, namely Neural Networks (NN) and Graph Machines (GM). While the GM model is implemented from the SMILES codes, the NN model is fed with σ-moments descriptors computed with the COSMOtherm software. The prediction reliability of both models is discussed based on a complex 10-molecule test set.In chapters 3 and 4, the scope of applicative properties of a nonionic glycerol-based surfactant are investigated. Firstly, chapter 3 focuses on its aggregation behavior in aqueous solutions and the formation of liquid crystals (LC) at low concentration, in comparison with the benchmark polyethoxylated fatty alcohols and alkyl polyglucosides. The influence of its physicochemical properties, in particular the air / water interface dilational viscoelasticity, is put in relation with the observed poor foamability and long-lasting foam stability.Finally, C12Gly2 properties in SOW systems are investigated in chapter 4. The Normalized Hydrophilic-Lipophilic Deviation (HLDN), a powerful theoretical tool, is regarded as a way to rationalize the characteristics of both emulsions and microemulsions. In this way, a thorough quantification of surfactants amphiphilicity, temperature sensitivity and salt-tolerance are presented. The potential use of C12Gly2 as O/W and W/O emulsifier is then investigated: the granulometry and stability of emulsions obtained by varying the oil concurs with HLDN values. A minimum is observed at HLDN = 0 and increases for negative and positive HLDN values.; Les objectifs de la thèse sont multiples et s'inscrivent dans le cadre de la mise en place d'une nouvelle plateforme technologique HT-SMART-FORMU dédiée à la formulation. L'accent est mis sur le développement de méthodes expérimentales fiables et d'outils théoriques et prédictifs, afin d'établir des relations entre la composition chimique, les propriétés physicochimiques et les propriétés applicatives.Les dispersions de particules sont le premier type de systèmes étudiés. Leur stabilité a longtemps été abordée par la théorie DLVO, mais des études plus récentes suggèrent l'utilisation des Paramètres de Solubilité de Hansen pour décrire leur stabilité en milieu non aqueux. Dans le premier chapitre, une méthode analytique systématique basée sur la mesure du potentiel zêta et le suivi de la stabilité par diffusion de la lumière permet de déduire une complémentarité des deux théories pour décrire la stabilité des dispersions de TiO2 en solvants non aqueux.La problématique de la prédiction de l'hydrophobie des huiles par la modélisation d'EACN, qui est un paramètre clé pour concevoir des systèmes dispersés tensioactif/huile/eau (SOW), est abordée dans le deuxième chapitre. Deux modèles mathématiques, conçus à l'aide de méthodes de machine-learning, sont proposés pour la prédiction rapide de l'EACN des huiles, à savoir les réseaux de neurones (NN) et les machines graphiques (GM). Alors que le modèle GM est implémenté à partir des codes SMILES, le modèle NN est alimenté par des descripteurs σ-moments calculés avec le logiciel COSMOtherm. La fiabilité des prédictions des deux modèles est discutée sur la base d'un ensemble de test de 10 molécules complexes.Dans les chapitres 3 et 4, l'étendue des propriétés applicatives d'un tensioactif non ionique à base de glycérol (C12Gly2) est étudiée. Le chapitre 3 se porte sur son agrégation en solution aqueuse et la formation de cristaux liquides (CL) à faible concentration, en comparaison avec les alcools gras polyéthoxylés et les alkyl polyglucosides. L'influence de ses propriétés physico-chimiques, en particulier la viscoélasticité de dilatation de l'interface air/eau, est mise en relation avec la faible moussabilité et la stabilité de mousse durable observées.Enfin, les propriétés du C12Gly2 en systèmes SOW sont étudiées dans le chapitre 4. La déviation hydrophile-lipophile normalisé (HLDN), un outil théorique puissant, est considéré comme un moyen de rationaliser les caractéristiques des émulsions et des microémulsions. Ainsi, une quantification approfondie de l'amphiphilie des tensioactifs, de leur sensibilité à la température et de leur tolérance au sel est présentée. L'utilisation du C12Gly2 comme émulsifiant H/E et E/H est ensuite étudiée : la granulométrie et la stabilité des émulsions obtenues en faisant varier l'huile concordent avec les valeurs du HLDN. Un minimum est observé à HLDN = 0, puis la granulométrie et la stabilité augmentent pour des valeurs de HLDN négatives et positives.

The grain-size control of aluminum alloys ensures good mechanical properties. In presence of are inforcing phase such as TiB2, these properties are directly influenced by the coherent interfaces respecting specific orientation relationships. In this context, the objectives of our work were (i) to achieve a sufficiently reliable description of the Al|TiB2 interfaces including an evaluation of their energies, (ii) to specify the bulk characteristics of the various Al-B-Ti phases which can influence the interfacial properties. The understanding of the underlying mechanisms being difficult by experimental techniques at atomic scale, we have opted for an approach based on numerical simulations at this scale, mainly using ab initio methods.The first part of this work deals with the study of the properties of heterophase Al|TiB2 interfaces. By focusing on basal Al|TiB2 interfaces, our analysis allowed to clarify various uncertainties found in the bibliography. Firstly, we have taken care to rigorously consider the role of elasticity, whose effect has been mostly neglected in previous works on Al|TiB2. Moreover, another critical point concerns the uncertainties of these previously calculated interface energies, due to the insufficient knowledge of the chemical potentials of the elements present in the involved ordered phases. We have also clarified this point by a rigorous analysis ensuring the stability of TiB2 and the absence of other undesirable phases. Finally, the comparison of the different systems used for the simulation of heterophase interfaces allowed us to conclude that periodic boundary conditions should be preferred, since free surface boundary conditions, mostly used in previous works, lead to less reliable results. Under these conditions, the interface energies obtained using our methodology recover a satisfactory agreement with the range of values expected for coherent interfaces. Our approach could be fruitfully applied to other systems currently suffering from the same deficiencies (Al|SiO2, Mg|TiB2, Al|Mg5Si6).In the second part of this thesis, we have investigated the bulk properties of the various Al-B-Ti phases relevant for the previous interfaces, in particular TiB2 and AlB2. To this end, we have determined the thermodynamic properties of these phases via the IPDA (independent point defect approximation). We first performed a detailed study of the TiB2 compound, including the effects of temperature, interstitials, and aluminum. We have shown that Ti and B vacancies are the major defects, that interstitials have no effect on the thermodynamic properties of this compound, and that Al is present in substitution in TiB2, this presence being limited to B-rich compounds. After completing this study of metal borides by a brief analysis of the solid solution of Ti and B in Al, we were able to partially build the Al-B-Ti ternary phase diagram at 1000 K, in particular in the two-phase domain (Al)+TiB2. In this domain, we have highlighted a characteristic "double fan" tie-line structure, thus providing complementary information to those previously obtained byphenomenological thermodynamic simulations (CALPHAD approach).; Le contrôle granulométrique des alliages d'aluminium permet de garantir de bonnes propriétés mécaniques. En présence d'une phase de renfort telle que TiB2, ces propriétés sont directement influencées par les interfaces cohérentes respectant certaines relations d'orientations. Dans ce contexte, les objectifs de notre travail étaient (i) de parvenir à une description suffisamment fiable des interfaces Al|TiB2 incluant une évaluation de leurs énergies, (ii) de préciser les caractéristiques volumiques des phases Al-B-Ti qui peuvent influencer les propriétés interfaciales. La compréhension des mécanismes sous-jacents restant difficile par les techniques expérimentales à l'échelle atomique, nous avons opté pour une approche reposant sur des simulations numériques à cette échelle, essentiellement avec des calculs ab initio.La première partie de ce travail porte sur l'étude des propriétés des interfaces hétérophases Al|TiB2. En se concentrant sur les interfaces basales Al|TiB2, notre analyse a permis de clarifier diverses ambiguïtés présentes dans la bibliographie. Tout d'abord, nous avons pris soin de prendre rigoureusement en compte le rôle de l'élasticité, dont l'effet a été le plus souvent négligé dans les travaux antérieurs sur Al|TiB2. De plus, un autre point critique concerne les incertitudes des énergies d'interfaces ainsi calculées, en raison de la connaissance insuffisante des potentiels chimiques des éléments présents dans les phases ordonnées impliquées. Nous avons également clarifié ce point par une analyse rigoureuse assurant la stabilité de TiB2 et l'absence d'autres phases indésirables. Enfin, la comparaison des divers systèmes utilisés pour la simulation des interfaces hétérophases a permis de conclure que les conditions aux limites périodiques doivent être préférées, puisque les conditions aux limites en surfaces libres, surtout utilisées dans les travaux précédents, ont conduit à des résultats moins fiables. Dans ces conditions, les énergies d'interfaces obtenues à l'aide de notre méthodologie retrouvent un accord satisfaisant avec la gamme de valeurs attendue pour des interfaces cohérentes. Notre approche pourrait être appliquée avec fruit à d'autres systèmessouffrant actuellement des mêmes déficiences (Al|SiO2, Mg|TiB2, Al|Mg5Si6).Dans la deuxième partie de ce mémoire, nous avons étudié les propriétés volumiques des phases Al-B-Ti pertinentes pour les interfaces précédentes, notamment TiB2 et AlB2. À cette fin, nous avons déterminé les propriétés thermodynamiques de ces phases via l'ADPI (approximation des défauts ponctuels indépendants). Nous avons d'abord réalisé une étude détaillée du composé TiB2, incluant les effets de la température, des interstitiels et de l'aluminium. Nous avons montré que les lacunes de Ti et de B sont les défauts majoritaires, que les interstitiels n'ont aucun effet sur les propriétés thermodynamiques de ce composé, et que Al est présent en substitution dans TiB2, cette présence étant limitée aux composés riches en B. Après avoir complété cette étude des borures métalliques par une brève analyse de la solution solide de Ti et B dans Al, nous avons pu construirepartiellement le diagramme de phases ternaire Al-B-Ti à 1000 K, notamment dans le domaine biphasé (Al)+TiB2. Dans ce domaine, nous avons mis en évidence une structure caractéristique de conodes en "double éventail", fournissant ainsi des informations complémentaires à celles obtenues précédemment par des simulations thermodynamiques phénoménologiques (approche CALPHAD).

A semi-automated and fully integrated millifluidic platform has been developed for rapid development and study of Solid-phase extraction (SPE) processes. In this instrumented setup, the fluid coming out of the extraction mini-column is analysed directly using on-line X-ray fluorescence, enabling a real-time, fast and accurate measurement of the elemental concentrations within the flowing liquid. This platform aims at enhancing and facilitating the development of SPEs whose numerous experimental parameters make it time consuming to optimize and upscale. Hence, this approach solves the labour intensity issue and is as accurate as off-line Inductively Coupled Plasma, for instance. This is exemplified with a system, typical of the electronic wastes recycling industry, comprising of a mixture of Rare-Earth Elements (REEs) and Iron, whose separation is investigated as a function of various experimental parameters. It enabled us to study the performance of the newly released METALICAPT® commercial materials and to determine an optimized path towards the almost total separation of Iron from the initial mixture. Overall, the original SPE process reported herein demonstrates the platform's reliability, performance and range of applicability. National Environmental Agency (NEA) National Research Foundation (NRF) Submitted/Accepted version FO, SC and J.C.G. acknowledge financial support from SCARCE project, which is supported by the National Research Foundation, Singapore, and National Environment Agency, Singapore under its Closing the Waste Loop Funding Initiative (Award No. USS-IF-2018-4). J.C.G. acknowledges funding for the platform from the European Research Council under the European Union’s 7th Framework Program (FP/2007-2013)/ERC Grant Agreement N◦ [320915] “REE-CYCLE”: Rare Earth Element reCYCling with Low harmful Emissions. BK ac- knowledges financial support from the European Research Council under the European Union’s 7th Framework Program (FP/2007-2013)/ ERC Proof of Concept Grant Agreement N◦ [768722] “SYNEXTRACT”: All Aqueous, continuous, Solid-Liquid SYNergistic EXTRACTion of rare earth elements. FO thanks CEA’s program “Mat ́eriaux et Proc ́ed ́es” for a PhD grant support (project MICROPRO).

For several decades, the race towards the miniaturization and the complexification of electronic functions have led to the integration of innovative materials to maintain the required performance in terms of response time and power consumption. The development of biosensors which is the subject of an intensive research activity does not make exception to the rule. Indeed, the coupling of chemical functionalization and nanomaterials (Si nanowires, MoS2 for example) open exciting new opportunities for the realization of miniature sensors, ultrasensitive and selective, used for the detection of chemical or biological species. In this context, the project of this thesis aims the development of a bio-detection platform through a multidisciplinary approach. Two applications are targeted: the measurement of pH and the detection of the hybridization of two complementary DNA strands. The demonstration of a first proof of concept based on innovative materials will allow a better understanding of the contribution of new materials (the duo transducer / bio-receiver), with the objective to improve our biosensors features, such as selectivity, sensitivity, stability, response time, and the ease of use.; Depuis plusieurs dizaines d'années, la course vers la miniaturisation et la complexification des fonctions électroniques suscitent l'intégration de matériaux innovants pour conserver les performances requises en termes de temps de réponse et de consommation électrique. Le développement des biocapteurs qui fait l'objet d'une activité de recherche intensive n'échappe pas à la règle. En effet, le couplage de la fonctionnalisation chimique et des nanomatériaux (nanofils de Si, MoS2 par exemple) ouvre de nouvelles perspectives enthousiasmantes pour la réalisation de capteurs miniatures, très sensibles et sélectifs pour la détection d'espèces chimiques ou biologiques. Dans ce contexte, le projet de cette thèse vise, par une approche pluridisciplinaire, le développement d'une plateforme de bio-détection. Deux applications sont ciblées : la mesure de pH et la détection de l'hybridation de deux brins complémentaires d'ADN. La démonstration d'une première preuve de concept à partir de matériaux innovants permettra de mieux comprendre l'apport des nouveaux matériaux (couple transducteur/bio-récepteur) pour améliorer la sélectivité, la sensibilité, la stabilité, la rapidité, et la simplicité d'utilisation des biocapteurs.

We present several new major features added to the Monte Carlo (MC) simulation code Brick-CFCMC for phase- and reaction equilibria calculations (https://gitlab.com/ETh_TU_Delft/Brick-CFCMC). The first one is thermodynamic integration for the computation of excess chemical potentials (μex). For this purpose, we implemented the computation of the ensemble average of the derivative of the potential energy with respect to the scaling factor for intermolecular interactions ⟨(∂U/∂λ)⟩. Efficient bookkeeping is implemented so that the quantity ∂U/∂λ is updated after every MC trial move with negligible computational cost. We demonstrate the accuracy and reliability of the calculation of μex for sodium chloride in water. Second, we implemented hybrid MC/MD translation and rotation trial moves to increase the efficiency of sampling of the configuration space. In these trial moves, short Molecular Dynamics (MD) trajectories are performed to collectively displace or rotate all molecules in the system. These trajectories are accepted or rejected based on the total energy drift. The efficiency of these trial moves can be tuned by changing the time step and the trajectory length. The new trial moves are demonstrated using MC simulations of a viscous fluid (deep eutectic solvent).

International audience; We have investigated the solubility of methanethiol and ethanethiol (methyl and ethyl mercaptans in an aqueous methyldiethanolamine solution (25 wt%) by using static-analytic method at 333 and 365K. The measurements were done for different pressure of methane in the absence of acid gas with individual acid gas present, and with mixture of acid gases present (CO2 and/with H2S). Additional measurement of Henry's law constant were realized by considering gas stripping method. Effect of total pressure (realized by addition of methane) and effect of acid gas loading for a constant total pressure around 7 MPa were studied. The increasing of pressure and acid gas loading increase the apparent Henry's law constant of the mercaptan, highlighting a drop out effect of the mercaptans.

A cross‐laboratory study on microbial fuel cells (MFC) which involved different institutions around the world is presented. The study aims to assess the development of autochthone microbial pools enriched from domestic wastewater, cultivated in identical single‐chamber MFCs, operated in the same way, thereby approaching the idea of developing common standards for MFCs. The MFCs are inoculated with domestic wastewater in different geographic locations. The acclimation stage and, consequently, the startup time are longer or shorter depending on the inoculum, but all MFCs reach similar maximum power outputs (55±22 μW cm−2) and COD removal efficiencies (87±9 %), despite the diversity of the bacterial communities. It is inferred that the MFC performance starts when the syntrophic interaction of fermentative and electrogenic bacteria stabilizes under anaerobic conditions at the anode. The generated power is mostly limited by electrolytic conductivity, electrode overpotentials, and an unbalanced external resistance. The enriched microbial consortia, although composed of different bacterial groups, share similar functions both on the anode and the cathode of the different MFCs, resulting in similar electrochemical output., The famous five: A cross‐laboratory study involving five institutions is presented. Each team runs a triplicate identical single chamber microbial fuel cell for 6 weeks varying only the inoculum. Electrochemical and operational parameters are collected. Microbiological analysis is carried out on the influent and effluent and on the electrodes. All the data collected are correlated by using robust statistics.

This article aims to study the interest of spent coffee grounds (SCG) valorization through caffeine recovery. In an original way, this study takes into account all the parameters such as (i) the brewing coffee methods (household, coffee shops, etc.), (ii) the storage conditions, in particular the drying step, (iii) the solid/liquid extraction parameters such as the nature of solvent, the temperature, the extraction time and the solid/liquid ratio, and (iv) the liquid/liquid purification parameters such as the nature, the volume and the pH of extraction medium. Results have shown that spent coffee grounds from coffee-shops obtained by percolation contain a higher amount of caffeine than spent coffee grounds from households obtained from spent pods or filters. A drying treatment is not required when extraction is performed under one week after the spent coffee grounds collection with 96.4% of not degraded caffeine. Solid/liquid extraction performed with 25 mL.g−1SCG of hydroalcoholic solvent (water/EtOH, v/v 60/40) at 60 °C during 15 min have given a caffeine yield up to 4.67 mg.g−1SCG. When using ethyl acetate, 93.4% of the caffeine has been selectively recovered by liquid/liquid extraction. Finally, the extraction of caffeine for the valorization of spent coffee grounds is a promising and easy way, which fits with an already important and well established market.

Striving towards a circular economy has led to the re-investigation of many existing processes, with the target of developing more sustainable variants. In our present economy, plastics form an important and omnipresent material affecting our daily lives. They are inexpensive, durable, corrosion resistant, and light weight leading to their use in a wide variety of applications.Within the plastic chemical recycling scheme, Fischer-Tropsch synthesis (FTS) could play a key role as the syngas feedstock that is converted in it, can be generated via the gasification of the considered plastics. This syngas is then chemo-catalytically converted into hydrocarbons such as paraffins and light olefins. Typical FTS catalysts are based on supported cobalt or iron species.Among the mechanistic kinetic models, the comprehensive variant based on the Single Event MicroKinetics (SEMK) concept has been widely applied in the field of oligomerization, autoxidative curing, etc. and has proven to be a versatile tool to simulate Fischer-Tropsch synthesis. However, developing mechanistic models for every chemical engineering challenge is not always feasible due to their complexity and the in-depth knowledge required to build such models.A detailed evaluation on the potential of using machine learning approaches to match the performance of results obtained using the Single-Event MicroKinetic model was carried out. Initially, the focus was on a single dominant output scenario (methane selective catalyst). The current work thus shows that more widely applied techniques in data science can now be applied for systematic analysis and interpretation of kinetic data. Similar analysis using experimental data can also help experimenters in their preliminary analysis, to detect hidden trends in the data, and thus to identify importance features. After gaining confidence on the investigated interpretation techniques, for the FTS reaction with single dominant output, a similar investigation on the potential of iron based catalysts with enhanced light olefin selectivity is carried out next.; En vue de promouvoir l’économie circulaire, de nombreux procédés chimiques sont actuellement réexaminés afin de développer des variantes plus durables. Cela a mené à une forte augmentation de production au cours des 60 dernières années, entraînant une production totale de 367 millions de tonnes en 2020.La méthodologie a ensuite été généralisée à l’aide d’apprentissage automatique non supervisé, ce qui a permis de dépasser les trois dimensions et de réduire le besoin d’intervention humaine. L’espace des descripteurs généré à partir de données microcinétiques (catalyseurs virtuels) est exploré en utilisant la méthode systématique du regroupement (clustering) et du classement (labelling) non supervisés. L’espace de la performance du catalyseur est regroupé en clusters et le nombre minimale de clusters est identifié. Chaque catalyseur virtuel (représenté par une certaine combinaison de descripteurs) est identifié du point de vue du cluster auquel il appartient. Il est ainsi possible d’obtenir l’étendue des valeurs des descripteurs dans le cluster ayant le meilleur rendement d’alcènes légers. Il est observé que les valeurs obtenues sont conformes à celles du catalyseur virtuel optimal identifié dans l’inspection visuelle précédente. On peut donc conclure qu’une méthode combinant la microcinétique et l’apprentissage automatique a été présentée pour le développement des catalyseurs et pour l’investigation détaillée de leurs propriétés, tout en diminuant le besoin d’intervention humaine.Finalement, la méthode d’apprentissage automatique a été étendue dans l’intention de pouvoir réaliser des prédictions de plusieurs sélectivités en se concentrant sur la production des alcènes légers à différentes conditions opérationnelles. Afin d’atteindre cet objectif, 4 modèles d’apprentissage automatique alternatifs ont été employés, i.e. la méthode lasso (lasso regression), la méthode des k plus proches voisins (k nearest neighbor regression ou KNN), la méthode de la machine à vecteurs de support (support vector machine regression ou SVR) et le réseau de neurones artificiels (Artificial Neural Network ou ANN). Les capacités de ces techniques sont évaluées par rapport à la reproduction du comportement linéaire de la conversion et la sélectivité en fonction des variables du procédé comme cela a été simulé par le modèle SEMK. Il est constaté que les modèles à base d’un réseau de neurones artificiels correspondent le plus aux résultats de référence du modèle SEMK. Une analyse supplémentaire utilisant la technique d’interprétation de la valeur SHAP a été appliquée aux modèles à base d’un réseau de neurones artificiels ayant la meilleure performance, en vue de mieux expliquer le fonctionnement des modèles.L’ensemble de l’étude a rapporté des connaissances essentielles, telles que les descripteurs de catalyseur optimales : les enthalpies de chimisorption atomique de l’hydrogène (QH ≈ 234 kJ/mol), du carbone (QC ≈ 622 kJ/mol) et de l’oxygène (QO ≈ 575 kJ/mol), pour la conception de catalyseurs ayant une sélectivité en alcènes légers élevée en utilisant un modèle SEMK mécaniste. De plus, l’étendue des conditions opérationnelles menant à la meilleure sélectivité en alcènes légers a été déterminée en adoptant plusieurs stratégies de modélisation (le concept des SEMK et l’apprentissage automatique). Il a été constaté que les effets de la température (580-620K) et la pression (1-2 bar) étaient les plus importants. Ensuite, une investigation est réalisée dans le but d’évaluer à quel point les résultats des modèles d’apprentissage automatique correspondent à ceux du modèle SEMK. Par exemple, une analyse préliminaire a pu être réalisée en utilisant un modèle d’apprentissage automatique pour l’analyse des données obtenues à l’aide d’expérimentation à haut débit. Ensuite, le modèle mécaniste a permis d’acquérir une compréhension chimique approfondie

International audience

Several hybridization strategies of a solar-autothermal biomass gasifier were examined for stable andcontinuous operation under variable solar irradiation. The ultimate objective was to demonstrate thefeasibility of controlled syngas production, through the modification of oxygen, water, and biomassinjection rates. Various hybridization strategies were probed by thermodynamic analysis andexperimentally validated. Thermodynamic equilibrium calculations detailed the impact of both H2Oand O2 injection rates on the produced syngas composition under constant wood feeding. Oxygeninjection decreased the H2:CO molar ratio, while reducing the solar thermal power required to carryout the gasification reaction. Meanwhile, the total H2+CO production dropped by 1.36 mole of H2 and0.64 mole of CO per mole of O2 added, independently of the quantity of water provided. Validationexperiments were then carried out under real concentrated solar flux in a directly-irradiated conicalspouted-bed reactor, following distinct hybridization paths. Maintaining constant the H2:CO ratioabove 1 during hybridization required to provide high amounts of water steam with oxygen, whichpenalized the gasifier efficient heating. In contrast, minimizing the water injection rate throughouthybridizationstrongly altered the H2:CO ratio but decreased the CO2 production and the solar thermal power requirement. Finally, the successful control of the outlet H2+CO volume flow rate with simultaneous oxygen and wood injection was demonstrated (under constant water feeding rate). Solarto- fuel efficiencies were kept around 20%, while hybridization decreased the cold-gas efficiency below 80%.

International audience; High energy consumption during harvesting is one of the main bottlenecks for sustainable microalgae production. Membranes can efficiently separate microalgae from liquids with low energy consumption, but membrane fouling remains an important issue. Flocculation prior to membrane filtration can increase membrane fluxes and decrease fouling, thus offering a low-cost and efficient solution to harvest microalgae. Biobased cationic cellulose nanocrystals were successfully used as flocculants for microalgae and were effective over a wide pH-range and for both freshwater and marine microalgae. Such flocculation was for the first time combined with vibration-assisted filtration using a charged, surface patterned membrane, enabling operation at very high flux (95 L/m2 h) using a vibration frequency of only 1 Hz, and even under sub-optimal flocculation conditions. Intermittent vibration decreased energy consumption further while keeping excellent filtration performance to finally achieve a record-low energy consumption for the membrane filtration of only 6.7 Wh/m3, which is andgt;25-times lower than that of normal membrane filtration. Interaction forces revealed that increasing particle size through flocculation prior to membrane filtration can significantly prevent microalgae attachment on the vibrating membrane surface. This work opens a new direction for sustainable microalgae harvesting with an ultra-low energy consumption, combined with a very high microalgae recovery, reduced use of chemicals, and lower membrane investment cost.

International audience; The main obstacle to the aqueous carbonation of non-serpentinised magnesium silicates is the formation of surface passivation layers, which severely limits the reaction rate and thus the overall efficiency of the process. A technological solution to overcome this problem is to perform the carbonation process inside a stirred bead mill, which aims to continuously remove the surface by-product layers by attrition. In this work, the aqueous carbonation of ferronickel slag, a mineralogically complex mining waste composed of a Mg/Si rich amorphous phase and a crystalline ferrous forsterite, was studied at 150°C and under 10 bar of CO 2 with different operating configurations: carbonation alone (C mode), attrition followed by carbonation (A-C mode) and concomitant attrition and carbonation (AC mode). By careful observation of the mineralogy and the surface of the secondary phases formed using complementary analytical techniques, the article allows a better understanding of the passivation phenomenon inherent to the carbonation of magnesium silicates, and confirms the effectiveness of continuous surface mechanical depassivation for reaching high carbonation rates with this type of material. Comparative analysis of the products obtained with the three operating modes shows that a true synergy takes place between attrition and carbonation due to the combined effect of continuous exfoliation and mechanical activation of particle surface, which goes far beyond the simple increase in surface area due to particle size reduction. While mechanical depassivation is here substantiated by several evidence, the additional mechanochemical activation effect cannot be delineated from experiment; however its beneficial contribution to carbonation is inferred from its observation in A-C mode. The work finds that the synergy between attrition and carbonation also yields very characteristic products. They consist in micrometric agglomerates formed by bound spherical particles a few tens of nanometers in size. These particles themselves contain an entanglement of nanometric grains of carbonates and amorphous silica dispersed inside a magnesium-depleted alumino-siliceous matrix. These results confirm that concomitant attrition and carbonation offers one of the most promising pathways for developing direct aqueous carbonation processes with non-thermally activatable magnesium silicates.

International audience; We report on a new class of metamaterials, which consists of meta-foams, optimized for high performance in enhanced solar steam generation. The design of these meta-foams involves precise dimensional control of a periodic two-dimensional micro-pore array. Proof-of-concept of meta-foams efficiency is demonstrated using two fabrication technologies. The first one involves microscale plasma etching onto a nanostructured black silicon substrate. As an alternative low-cost technique, we also use 3D printing of a graphene-containing polymer material. The experimental validation shows that the best evaporation rate reaches 1.34 kg/(h·m2) under 1 sun illumination, in open-air conditions under normal temperature and relative humidity conditions of 20 °C and 58%, an unmatched value so far under similar conditions, while the theoretical limit is estimated at 1.5 kg/(h·m2). This corresponding to a 89% conversion efficiency. Experimental data concur well with the predicted performance obtained by numerical simulations. The proposed model simultaneously accounts for both heat and mass transfer, including photothermal conversion and water phase change, to guide the optimization towards the maximization of the evaporation rate, an important figure of merit in many applications, including solar heat harvesting and solar water purification.

International audience

International audience; Copper and cobalt demand is projected to be increased from here to 2050 and the challenge is to find treat economically minerals which contains those metals. Several tailings from oxide ores throughout the word contain good grades of copper and cobalt that should be recovered by froth flotation. This paper investigates the recovery of copper and cobalt through reprocessing of spiral classifier tailings by determination of specific reagents dosage. The flotation behaviours of malachite and heterogenite were studied through many roughing and cleaning flotation tests in order to recovery most of copper and cobalt. The effect of specific reagents was be varied and others parameters were kept constant. The highest recoveries of both copper and cobalt in rougher concentrate were respectively 82.51% and 72.51% with grades of 12.52% and 0.99% respectively. However, the cleaner concentrate was 24.54 Cu% and 1.38% Co with recoveries of 69.26 % and 40.7% respectively. It was concluded that the reprocessing of spiral classifier tailings through froth flotation is benefit because it recovers most of desired metal and reduces the risk of their presence on environment through.; La demande de cuivre et de cobalt devrait augmenter d'ici 2050 et le défi consiste à trouver des minéraux à traiter économiquement qui contiennent ces métaux. Plusieurs résidus de minerais oxydés à travers le monde contiennent de bonnes teneurs en cuivre et en cobalt qui devraient être récupérés par flottation par mousse. Cet article étudie la récupération du cuivre et du cobalt par le retraitement des résidus de classificateurs en spirale par la détermination du dosage de réactifs spécifiques. Les comportements de flottation de la malachite et de l'hétérogénite ont été étudiés à travers de nombreux tests de dégrossissage et de flottation de nettoyage afin de récupérer la majeure partie du cuivre et du cobalt. L'effet de réactifs spécifiques a été varié et d'autres paramètres ont été maintenus constants. Les récupérations les plus élevées de cuivre et de cobalt dans les concentrés bruts étaient respectivement de 82,51 % et 72,51 % avec des teneurs de 12,52 % et 0,99 % respectivement. Cependant, le concentré de nettoyage était de 24,54 % Cu et 1,38 % Co avec des récupérations de 69,26 % et 40,7 % respectivement. Il a été conclu que le retraitement des résidus du classificateur en spirale par flottation par mousse est avantageux car il récupère la plupart des métaux souhaités et réduit le risque de leur présence dans l'environnement.

International audience; The chemical vapor deposition (CVD) of silicon carbide from vinyltrichlorosilane (VTS) was studied to identify a range of conditions leading to pure crystalline SiC. The deposition rate was recorded to evidence the various deposition regimes. Gas phase, elemental analyses and infiltration tests were also performed. Three distinct chemical reaction regimes were identified. In CVD conditions, carbon is co-deposited at low temperature while VTS is only partially decomposed. In infiltration conditions, the composition switches to pure SiC inside the porous substrate because of a depletion of reactive hydrocarbon species. Competing heterogeneous reactions are responsible for a hysteresis versus temperature, in both deposition rate and composition of the deposit. The high temperature domain is the most suitable to deposit pure crystalline SiC in CVD conditions. Hydrogen dilution strongly accelerates the homogeneous decomposition of VTS as compared to argon. Assumptions on the reaction mechanism were proposed describing the chemistry of this precursor.

Cyclic and aromatic hydrocarbons are important components of usual commercial fuels, with C6-rings being among the most abundant cyclic structures. The combustion chemistry of C6-rings involves different levels of unsaturation, either as initial fuels (aromatics, naphtenes, …) or as intermediates formed during their combustion. In this work the ignition delays of cyclohexane, cyclohexene, 1,3-cyclohexadiene and 1,4-cyclohexadiene are systematically studied using experiments and kinetic modeling. Shock tube experiments were performed at high-temperature (above 1200 K) and for mean pressures of 6 atm. A detailed chemical kinetic model was developed that includes the combustion chemistry of the four cyclo-C6 fuels. Electronic structure calculations were performed at the CCSD(T)/CBS//B2PLYP-D3 level of theory on the pericyclic reactions of the unsaturated fuels. Pressure-dependent rate coefficients were computed by solving the master equation, and included in the mechanism. The model was validated against the new ignition data and against data of the literature. It was able to reproduce the experimental ranking of reactivity: cyclohexene > 14-CHD > cyclohexane > benzene ≈13-CHD. Kinetic analyses were performed to explain this difference of reactivity. It is shown that pericyclic reactions play a major role in the initial decomposition of the unsaturated fuels.

International audience; Urea is used in Selective Catalytic and Non Catalytic Reduction (SCR and SNCR) methods for NOx abatement in post-combustion processes. The decomposition of urea-water solution in exhaust systems leads to the formation of NH3, which is the NOx reducing agent. However, the decomposition of urea can also lead to the formation of unwanted pyrolysis by-products, particularly in region where the temperature and pressure conditions are not optimal or via wall-spray interactions. In this study, a gas phase kinetic model for urea pyrolysis is proposed to explain the growth of pyrolysis by-products of urea, and in particular, the route of formation of the major product: isocyanuric acid. Systematic theoretical calculations, using electronic structure calculations and transition state theory, were performed to explore all the possible unimolecular and bimolecular reactions of the initial species. Kinetic modeling was used to select the relevant reaction pathways at each growing step, and their rate constants were refined using CCSD(T)/CBS//B2PLYP-D3/cc-pvTZ calculations. Quantum calculations showed that the postulated growing schemes of the literature, based on the successive urea + HNCO ⇆ biuret, biuret + HNCO ⇆ triuret followed by the cyclization of triuret into isocyanuric acid are not energetically favored. It is observed that the most favored reaction route to isocyanuric acid involves carbamimidic acid, the urea tautomer, that first yields biuret in a reaction with HNCO and then is involved in the formation of triuret by reacting with a decomposition product of biuret. Isocyanuric acid is produced from the reaction between HNCO and the same decomposition product of biuret. This new mechanism of formation of isocyanuric acid is tested at different conditions to explore its most favored conditions of formation in the gas phase. Exploratory simulations of a pseudo condensed phase are also performed to qualitatively simulate condensed phase experiments and explain the observed pyrolysis yields.

International audience; Numerous studies on the understanding of extraction mechanisms and complex structures have been carried out for hydrometallurgical processes. However, the influence of extractant stereochemistry on extraction performance has not been fully understood or even studied at all. In the present study, promising results for the extraction of actinides have been obtained using different stereoisomers of the extractant di-2-ethylhexylbutyramide (DEHBA), which highlights the importance of the extractant chirality.

International audience

International audience; A multi-analytical methodology is implemented to characterize several sieving fractions of industrial samples of Black Mass (BM) powders originating from the thermo-mechanical treatment of cylindrical and prismatic-type spent nickel metal-hydride (Ni-MH) batteries. Elemental analyses of 17 elements (including C and O) indicate that the elemental composition of the powders (greater than93 %wt) does not depend on the battery type nor on the sieving fraction. XRD analyses evidence several phases (including Ni, NiO, CeO2 and C) but their quantification is not possible. Beyond these standard characterisations, magnetic susceptibility measurements demonstrate that the amount of metallic nickel versus nickel oxide increases with the sieving fraction, and that powders from prismatic-type batteries contain twice as much metallic nickel than cylindrical ones. Thanks to statistical analysis (based on clustering algorithms) of an electron probe µ-analysis (EPMA) compositional map, the complete methodology allows us to propose a full phase distribution for the BM particles. Three types of particles are identified and quantified. They originate from the partial oxidation of the battery components (anode active mass, anode current collector, cathode active mass and cathode current collector). The whole picture highlights the joint importance of battery ageing mechanisms, thermal deactivation and BM sieving steps on powder composition

International audience; Membrane processes are extensively used in the food industry, especially in the dairy, wine and beer, fruit juice, and sugar industries. In the dairy industry, removal of bacteria and spores from skim milk (cold pasteurization), separation of casein micelles, separation and fractionation of fat globules from whole milk, concentration and demineralization of whey and milk ultrafiltration permeate, fractionation of whey proteins, and desalination of whey membrane processes are realized by membrane processes. In the wine and beer industry, cross-flow of wines and beer clarification and stabilization of wines by electrodialysis are of common use. Fruit juice processing involves clarification, concentration, and deacidification. In the sugar industry, purification and demineralization are realized by membrane processes. This review presents these membrane processes by focusing on the main parameters and phenomena like permeation flux, selectivity, and fouling of membranes. Innovative pilot designs and cleaning methods are presented. The potentials of more unusual techniques like membrane emulsification and electrodialysis of organic acids from fermentation broth are also underlined. A specific attention is paid to the recent development of membrane processes in the food industries

Predicting and controlling the liquid dynamics in a porous medium is of large importance in numerous technological and industrial situations. We derive here a general analytical solution for the dynamics of a flat liquid front in a porous medium, considering the combined effects of capillary imbibition, gravity and evaporation. We highlight that the dynamics of the liquid front in the porous medium is controlled by two dimensionless numbers: a gravity–capillary number G and an evaporation–capillary number E. We analyze comprehensively the dynamics of the liquid front as functions of G and E, and show that the liquid front can exhibit seven kinds of dynamics classified in three types of behaviors. For each limiting case, a simplified expression of the general solution is also derived. Finally, estimations of G and E are computed to evidence the most common regimes and corresponding liquid front dynamics encountered in usual applied conditions. This is realized by investigating the influence of the liquid and porous medium properties, as well as of the atmospheric conditions, on the values of the dimensionless numbers., SCOPUS: ar.j, info:eu-repo/semantics/published