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International audience; Evidence of a changing environment in the catchment area of a small pond (Lansquenet, Lorraine, France) during the last millennium was provided by coupling palynology data and organic ratios [terrestrial to aquatic ratio: TAR(HC); the C29 vs. C27 sterols, C29/C27(ST); average chain length, ACL and aquatic/macrophytes ratio, Paq]. The depositional and alteration conditions of organic matter (OM) were provided by the 5α(H)-stanols/Δ5-sterols ratio. This study shows that quite simple organic ratios clearly allow identification of the different evolution steps of a watershed, from a swamp to the progressive settlement of a pond. During the swampy period, the C/N(at) (ca. 11.1), TAR(HC) (ca. 36.8), C29/C27(ST) (ca. 8.7) and Paq (

International audience; We present a theoretical and experimental investigation of the titratable charge of 2:1 clays with various structural charge ('b): pyrophyllite ('b = 0 e. nm(2), montmorillonite ('b = -0.7 e. nm(2) and illite ('b = -1.2 e. nm(2). The calculations were carried out using a Monte Carlo method in the Grand Canonical ensemble and in the framework of the primitive model. The clay particle was modeled as a hexagonal platelet, with an ‘ideal' crystal structure. The only fitting parameters used are the intrinsic equilibrium constants for the protonation/deprotonation reactions of the broken-bond sites on the lateral faces. Simulations are found to give a satisfactory description of the acid-base titration of 2:1 clays without any additional fitting parameter. In particular, combining the electrostatics from the crystal substitutions with the protonation constants, the simulations satisfactorily catch the shift in the point of zero net proton charge (PZNPC) of 2:1 clays according to the ionic strength, in good qualitative agreement with experimental observations following the sequence: pyrophyllite < montmorillonite < illite.

We present a theoretical investigation of the titratable charge of clays with various structural charge (sigma(b)): pyrophyllite (sigma(b) = 0 e x nm(-2)), montmorillonite (sigma(b) = -0.7 e x nm(-2)) and illite (sigma(b) = -1.2 e x nm(-2)). The calculations were carried out using a Monte Carlo method in the Grand Canonical ensemble and in the framework of the primitive model. The clay particle was modeled as a perfect hexagonal platelet, with an "ideal" crystal structure. The only fitting parameters used are the intrinsic equilibrium constants (pK(0)) for the protonation/deprotonation reactions of the broken-bond sites on the lateral faces of the clay particles, silanol, =SiO(-) + H(+) --=SiOH, and aluminol, =AlO(-1/2) + H(+) --=AlOH(+1/2). Simulations are found to give a satisfactory description of the acid-base titration of montmorillonite without any additional fitting parameter. In particular, combining the electrostatics from the crystal substitutions with ionization constants, the simulations satisfactorily catch the shift in the titration curve of montmorillonite according to the ionic strength. Change in the ionic strength modulates the screening of the electrostatic interactions which results in this shift. Accordingly, the PZNPC is found to shift toward alkaline pH upon increasing the permanent basal charge. Unlike previous mean field model results, a significant decrease in PZNPC values is predicted in response to stack formation. Finally, the mean field approach is shown to be inappropriate to study the acid-base properties of clays.

International audience; In deep geological repositories for high-level nuclear wastes, interactions between steel canisters and clay-rich materials may lead to mineralogical transformations with a loss of the confining properties of the clays. Experiments simulating the conversion of smectite to Fe-rich clay phases in contact with Fe metal have been carried out to evaluate such a possibility by taking into account the effects of a series of critical parameters, including temperature, pH, and Fe/clay (Fe/C) and liquid/clay (L/C) ratios. The mineralogical and chemical transformations observed in these experiments have been compared with data from the literature, and subsequently used to propose a conceptual model for the main mineralogical transformations which can be expected in clay formations surrounding high-level nuclear waste repositories. In the presence of Fe metal and under low oxygen fugacity ( 5: dioctahedral smectite (di-sm) ? 7 A˚ Fe-rich phase (berthierine, odinitecronstedtite) for large Fe/C ratios (>0.5), or di-sm ? Fe-rich di-sm + Fe-rich trioctahedral smectite (tri-sm) for small Fe/C ratios (0.1); (2) up to 150ºC, under alkaline pH (1012), and L/C > 5: di-sm ? Fe di-sm (Npalygorskite) for a small Fe/C ratio (0.1); (3) at 300ºC, Fe/C = 0.1, and L/C > 5: di-sm ? Fe-rich saponite ? trioctahedral chlorite + feldspar + zeolite (near-neutral pH); di-sm ? Fe-rich vermiculite + mordenite (pH 1012). Low temperatures (

International audience

International audience; The study of the transformation of smectite to illite, chlorite or vermiculite via interstratified clay minerals needs precise qualitative and quantitative determinations of the different layers in the mixed- layer clays and is generally based on X-ray diffraction (XRD) patterns after specific treatments of the clay samples. Saturation with K or Mg followed by ethylene glycol (EG) solvation are classical methods used to identify high-charge smectite and vermiculite. These procedures have been applied to two experimental clays, one composed of smectite layers and the second, a mixture of vermiculite and smectite layers. Different methods of glycolation (EG vapor or liquid EG) produce significant differences in the XRD patterns. Comparison with literature data indicates that K-saturated, high-charge smectite (~0.8 < total charge

BACKGROUND: We have previously observed associations of the T-allele of the exon 18 variant (ACC --> ACT; Thr759Thr) of the sulfonylurea receptor 1 (SUR1) gene with type 2 diabetes mellitus (T2DM). Here we assess beta-cell function and insulin sensitivity in carriers of different genotypes at this locus. METHODS: Pre-hepatic insulin secretion rates (ISR) derived by deconvolution of circulating C-peptide levels, and glucose clearance were assessed during graded infusions of intravenous glucose in CC-homozygous (n=6) and CT-heterozygous (n=6) nondiabetic relatives of CT-heterozygous type 2 diabetic subjects. RESULTS: Average ISR over the duration of the study, adjusted for sex, age, BMI and prevailing glucose levels, were lower in CT-heterozygous subjects as compared with CC-homozygous subjects (3.91 +/- 0.40 vs. 4.84 +/- 0.28 pmol/kg x min(-1); p=0.048). The correlation curves relating ISR to glucose levels were significantly different in the two groups (analyses of covariance p=0.029). Glucose clearance was similar in both groups. CONCLUSIONS: Insulin secretion rates, but not insulin sensitivity, assessed during graded infusion of glucose were mildly decreased in nondiabetic relatives of type 2 diabetic subjects, who carry the at risk T-allele of exon 18 variant of the SUR1 gene. These results suggest that the at-risk allele might have a small effect on pancreatic B-cell function and contribute to the development of T2DM in these families.

International audience; A new coupling of ultrasound device with membrane process has been developed in order to enhance cross-flow ultrafiltration of colloidal suspensions usually involved in several industrial applications included bio and agro industries, water and sludge treatment. In order to reduce mass transfer resistances induced by fouling and concentration polarization, which both are main limitations in membrane separation process continuous ultrasound is applied with the help of a vibrating blade (20 kHz) located in the feed channel all over the membrane surface (8 mm between membrane surface and the blade). Hydrodynamic aspects were also taking into account by the control of the rectangular geometry of the feed channel.Three colloidal suspensions with different kinds of colloidal interaction (attractive, repulsive) were chosen to evaluate the effect of their physico-chemical properties on the filtration.For a 90W power (20.5 W cm(-2)) and a continuous flow rate, permeation fluxes are increased for each studied colloidal suspension, without damaging the membrane. The results show that the flux increase depends on the initial structural properties of filtered dispersion in terms of colloidal interaction and spatial organizations.For instance, a Montmorillonite Wyoming-Na clay suspension was filtered at 1.5 x 10(5) Pa transmembrane pressure. Its permeation flux is increased by a factor 7.1, from 13.6 L m(-2) h(-1) without ultrasound to 97 L m(-2) h(-1) with ultrasound. (C) 2013 Elsevier B.V. All rights reserved.

An appropriate monitoring program proving CO2 can be stored safely for a long time is a key factor in controlling long term storage efficiency of CCS projects. A site in the Paris basin near Claye-Souilly area was identified for a future CCS pilot project. Baseline acquisition is deeply complex due to the presence of multi CO2 sources (biogas, vehicles, industrial operations, natural sources). Campaigns of measurement have demonstrated the feasibility of such strategy to detect gas transfers from subsurface equipment. Survey of CO2 storage is greatly affected by site activity and requires the development of efficient sensors in deep boreholes.

International audience; This study reports the ability of the coupled Raman-FTIR/completion system to establish continuous measurements of soil gases for the monitoring of the CO2 sequestration sites. The method was deployed in the first French CCS pilot at Lacq-Rousse, in France during the injection operation. In this study, the continuous recording of the N-2, O-2, H2O and CO2 concentrations in soil allowed by the coupled Raman/FTIR completion system appears as a first step to decipher CO2 abnormal variations at the surface of the CCS site.

International audience; The valorization of precipitated carbonates is envisaged for industrial gases treatment in order to avoid waste disposal in landfills. In this paper, the valorization focuses on the desulfurization of fumes by carbonate materials through the semi-wet way. Three carbonated materials are tested: two industrial residues and a limestone of reference. Their composition and size distribution are comparable. Infrared spectroscopy and electron microscopy are used to identify the evolution of mineral and surface composition. Multi-scale study highlights different behaviors between carbonate samples. Laboratory dissolution tests reveal that two industrial residues were clearly more soluble and have a final dissolution degree >= 90 %. The same carbonate materials were then tested at pilot scale. The unit can treat around 1,000-2,000 m(3)/h of industrial fumes enriched in SO2 in semi-wet desulfurization process. Injection of H2O was tested at constant temperature and Ca/S ratios to optimize the process. Origin of CaCO3 particles and hydration properties appear as the main factors controlling desulfurization efficiency. Calcium carbonates precipitated in brines show higher efficiency in SO2 conversion rate (40-70 %) in comparison with other carbonate materials in semi-wet way, i.e. limestone or leached wastes (25-35 %). The combination of high dissolution rate of CaCO3 particles with surface hydration appears as responsible for this performance.

Damage of Advanced High Strength Steel resistance spot welds is investigated in Tensile Shear by means of coupled microtomography, metallography and fractography. Two main failure mechanisms and failure zones are identified: (i) strain localization in the base metal/subcritical Heat Affected Zone (HAZ), (ii) ductile shear at the interface in the weld nugget. A finite element model is developed in order to illustrate these competing failure mechanisms leading to distinct macroscopic failure types. The local constitutive behavior is obtained from tensile tests on simulated HAZ microstructures and an estimation of the Rice integral ( J ) at the notch tip is provided for the assessment of interfacial failure. The model enables capturing the main trends in failure type transition as a function of weld geometry as well as a reliable estimation of the load bearing capacity.

Analytical scanning and transmission electron microscopy, sequential chemical extraction, and pyrolysis–gas chromatography on solvent-extractable organic matter are used to provide both direct and indirect speciation of heavy metals and organic matter in sewage-suspended solids and in biofilms taken from an urban sewer in an emerging country. Compared to developed countries where the domestic activities represent the main source of heavy metal pollution in wastewater, the combined sewer system of an emerging country also integrates significant contributions originating from the private drinking water supply system (Zn, Cu, Cr, and Ni), industrial discharges (Cu, Mn), and road dust transported by street washing (Pb). The relative importance of those sources changes drastically over time as evidenced by the difference in metal levels recorded between weekday and weekend effluents. Nevertheless, sewer biofilms are found to provide a good averaging of contaminant loads and they can be used as environmental archives. The speciation study reveals the predominance of neoformed minerals such as sulfides and phosphates and highlights the strong biogeochemical dynamics that takes place within the sewer system. Electron microscope observations of heavy metal-bearing phases proved to be necessary to provide a consistent interpretation of chemical extraction results. The molecular characterization of the solvent-extractable organic matter from biofilms reveals the presence of classical fingerprints of domestic activity such as fecal sterols and detergents but also confirms a major contribution of petroleum by-products consistent with a traffic-related pollution.

Ultra-rapid annealing (URA) cycles were performed on a low-carbon, Al-killed steel coiled at a high temperature. The parameters (heating and cooling rates, and annealing temperature) of these cycles were varied to analyze their impact on the microstructure and the tensile properties of the steel. It was established that the final microstructure of the steel is governed by an interaction between the growth of the primary ferrite grains (resulting from the recrystallization) and the development of the austenite grains formed above AC1, and that the heating rate strongly influences this interaction. A microstructure favorable to deep drawability (leading to a mean plastic strain ratio of 1.8) was obtained by adjusting the parameters of the URA cycles. The current work showed that three conditions have to be fulfilled to produce this optimized microstructure: (1) Intercritical annealing should lead to the formation of about 20 pct of austenite, (2) the heating rate has to be rapid to minimize the carbon content in solution during recrystallization, and (3) the cooling rate must be relatively slow (≈50 K/s).

A theory is developed to evaluate the electrostatic correction for the rate of reaction between a small ion and a charged ligand nanoparticle. The particle is assumed to generally consist of an impermeable core and a shell permeable to water and ions. A derivation is proposed for the ion diffusion flux that includes the impact of the equilibrium electrostatic field distribution within and around the shell of the particle. The contribution of the extra- and intraparticulate field is rationalized in terms of a conductive diffusion factor, f(el), that includes the details of the particle geometry (core size and shell thickness), the volume charge density in the shell, and the parameters defining the electrostatic state of the particle core surface. The numerical evaluation of f(el), based on the nonlinear Poisson-Boltzmann equation, is successfully complemented with semianalytical expressions valid under the Debye-Hückel condition in the limits of strong and weak electrostatic screening. The latter limit correctly includes the original result obtained by Debye in his 1942 seminal paper about the effect of electrostatics on the rate of collision between two ions. The significant acceleration and/or retardation possibly experienced by a metal ion diffusing across a soft reactive particle/solution interphase is highlighted by exploring the dependence of f(el) on electrolyte concentration, particle size, particle charge, and particle type (i.e., hard, core/shell, and entirely porous particles).

International audience; The aim of the present paper is to clarify previous results [1] showing that selectivity coefficients determined for the exchange of Na+ for Ca2+ in montmorillonite were dependent on the solid/solution ratio. The organization of montmorillonite suspensions upon Na+/Ca(II) exchange was analyzed by combining optical microscopy, small-angle X-ray scattering and X-ray diffraction. All samples displayed flocculated characteristics, eliminating the possibility of contrasting accessibility of sorption sites with the solid/ solution ratio. Modeling of experimental X-ray diffraction patterns was used to quantify the relative proportions of interlayer Ca2+ and Na+ cations along the exchange isotherm. The results further confirmed the influence of the solid/solution ratio on the degree of interlayer Ca(II)-for-Na+ exchange, and specific selectivity coefficients for interlayer sites were determined. The effect of the solid/solution ratio was finally interpreted by the resulting local changes in the solution chemistry. We demonstrated that by accounting for the Donnan effect, the different data can be interpreted using a single selectivity coefficient. The obtained Kc constant was successfully applied to interpret existing hydrogeochemical data on a natural aquitard. This most likely represents a more constrained and valid approach for the modeling of reactive element transport in natural media than does the poorly defined Kd parameter.

Two divalent cation-based coagulants, magnesium chloride and manganese chloride, were used to treat synthetic textile wastewaters containing the azo-dye pigment Levafix Brilliant Blue EBRA. The jar-tests were performed in the presence or absence of auxiliary dyeing chemicals. They proved that (i) both divalent cation-based coagulants were effective in the treatment of those alkaline effluents, (ii) better performances in terms of color removal, residual turbidity, and settled volume, were achieved with manganese chloride, and (iii) the presence of dyeing auxiliaries significantly increases the required coagulant demand for treating the textile effluent. The dye removal mechanisms were investigated by combining observations of freeze-dried sediments with transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy and selected area electron diffraction, Fourier transform infrared spectroscopy, adsorption experiments, and aggregates size measurements with a laser sizer under cyclic shear conditions. The results show that brucite (Mg(OH)(2)) particles are formed when applying MgCl(2) to the textile wastewaters, whereas a mixture of feitknechite (β-MnOOH) and hausmannite (Mn(3)O(4)) is obtained when using MnCl(2). More poorly crystallized particles are formed in presence of auxiliary dyeing chemicals. The adsorption experiments suggested that the azo-dye pigment adsorbs onto the surface of precipitating phases, whereas the aggregation dynamics indicated that a charge-neutralization mechanism underlies the formation of aggregates. The dye removal is then consistent with a precipitation/adsorption mechanism.

International audience; The influence of Erythromycin, Roxithromycin, Amoxicillin, Tetracycline and Sulfamethoxazole on municipal sludge in batch reactors was investigated. The study was focused on extracellular polymeric substances (EPS) as indicator of bacteria sensitivity to toxic agents. The EPS were analysed by UV-Vis and FT-IR spectroscopies and by size exclusion chromatography. It was found that Erythromycin and Roxithromycin induced a significant increase of bound EPS in flocs. This was attributed to a protection mechanism of the bacteria. Erythromycin was the only antibiotic which inhibited COD and nitrogen removal.

A simple theoretical model is proposed to describe the limiting size of aggregates attained at steady state under given shear conditions. The stable size is assumed to be the result of a dynamic equilibrium between simultaneous aggregate growth and breakup that are represented as first-order processes. The theory establishes that the evolution of steady-state aggregate size versus shear rate is written as the sum of two exponential laws. The validity of the model is verified by direct observation of the coagulation behavior of latex particles in the stagnant plane of a counter-rotating Couette reactor. The influence of latex elementary particle size, initial particle volume fraction, and inner gap spacing of Couette reactor, are investigated. In all cases, the model shows good agreement with the experimental results. Aggregate growth proceeds with a monomodal size distribution that exhibits a scaling behavior. Such monomodal distribution evolves toward broad and even bimodal steady-state distributions at both low and high shear rates, whereas a narrow monomodal pattern is observed at intermediate shear gradients. The aggregate cohesive force F(C) can be calculated from the critical shear rate of dislocation defined by the model. In contrast to the broadly accepted view that larger flocs should be more fragile than smaller aggregates, we find that F(C) scales as D(3/2) where D is the aggregate characteristic diameter. The latter relationship may be derived by assuming linear elasticity of aggregates.

The present paper describes detailed kinetics investigations on some selected chlorine-solid reactions through thermogravimetric measurements. The solids studied in this article include chemical pure oxides and sulfides as well as their natural bearing materials. The chlorinating agents employed are gaseous mixtures of Cl2+N2 (chlorination), Cl2+O2 (oxychlorination), and Cl2+CO (carbochlorination). Results are presented as effects of various parameters on the reaction rate of these solids with these chlorinating agents. It was observed that the reactivity of these solids towards different chlorinating agents varied widely. Sulfides could be chlorinated at room temperature, while carbochlorination of chromium (III) oxide was possible only above 500 °C. The variation of the chlorination rate of these complex materials with respect to gas velocity, composition and temperature enabled us to focus some light on the plausible reaction mechanisms and stoichiometries. The obtained results were used for selective removal of iron from chromite concentrates, extraction of valuable metals from sulfide materials, purification of MgO samples, etc.Este trabajo describe detalladas investigaciones cinéticas en algunas reacciones seleccionadas de cloro-sólido a través de medidas termogravimétricas. Los sólidos estudiados en este artículo incluyen óxidos químicos puros y sulfuros, así como sus materiales naturales de soporte. Los agentes de cloración empleados son mezclas de gases de Cl2+N2 (cloración), Cl2+O2 (oxicloración) y Cl2+O2 (carbocloración). Los resultados se presentan como efecto de varios parámetros en el porcentaje de reacción de estos sólidos con los agentes de cloración. Se ha observado que la reactividad de estos sólidos a través de diferentes agentes de cloración varía ampliamente. Los sulfuros se pudieron clorar a temperatura ambiente mientras que la carbocloración del óxido de cromo (III) sólo fue posible por encima de los 500 °C. La variación del porcentaje de cloración de estos materiales complejos con respecto a la velocidad del gas, composición y temperatura permitió arrojar alguna luz en los posibles mecanismos de reacción y estequiometrías. Los resultados obtenidos se han usado para la eliminación selectiva del hierro de concentrados de cromo, extracción de metales valiosos de materiales sulfhídricos, purificación de muestras de MgO, etc.

Disposal of NaCl-containing cuttings is a major environmental concern due to the high solubility of chlorides. The present work aims at reducing the solubility of chloride by encapsulation in low permeability matrix as well as lowering its solubility by trapping into low-solubility phases. Both the studied materials were cuttings from an oil-based mud in oil drillings containing about 50% of halite, and cuttings in water-based mud from gas drilling containing 90% of halite. A reduction in the amount of dissolved salt from 41 to 19% according to normalized leaching tests was obtained by addition of potassium ortho-phosphate in the mortar formula of oil-based cuttings, while the aluminium dihydrogeno-phosphate is even more efficient for the stabilization of water-based cuttings with a NaCl content of 90%. Addition of ortho-phosphate leads to form a continuous and weakly soluble network in the cement matrix, which reduces the release of salt. The formed mineralogical phases were apatite and hydrocalumite. These phases encapsulate the salt grains within a network, thus lowering its interaction with water or/and trap chloride into low-solubility phases. The tested approaches allow to develop a confinement process of NaCl-containing waste of various compositions that can be applied to wastes, whatever the salt content and the nature of the drilling fluids (water or oil).

We studied the adsorption of bovine serum albumin (BSA) from phosphate-buffered saline (pH 7.4) to hydrophilic and hydrophobic surfaces. Attenuated total reflection Fourier transform infrared spectroscopy, supported by spectral simulation, allowed us to determine with high precision the amount of BSA adsorbed (surface coverage) and its structural composition. The adsorbed BSA molecules had an alpha-helical structure on both hydrophobic and hydrophilic surfaces but had different molecular conformations and adsorption strengths on the two types of surface. Adsorption of BSA was saturated at around 50% surface coverage on the hydrophobic surface, whereas on the hydrophilic surface the adsorption reached 95%. The BSA molecules adsorbed to the hydrophilic surface with a higher interaction strength than to the hydrophobic surface. Very little adsorbed BSA could be desorbed from the hydrophilic surface, even using 0.1 M sodium dodecyl sulfate, a strong detergent solution. The formation of BSA-phosphate surface complexes was observed under different BSA adsorption conditions on hydrophobic and hydrophilic surfaces. The formation of these complexes correlated with the more efficient blocking of nonspecific interactions by the adsorbed BSA layer. Results from the molecular modeling of BSA interactions with hydrophobic and hydrophilic surfaces support the spectroscopic findings.

The present magnetic levitation facility offers an alternative to space means for studying fluids and especially liquid oxygen that exhibits important safety requirements. The station has great use flexibility. Thus it enables us to study hydrodynamic instabilities (acceleration and deceleration phase) and also to focus on thermal exchanges (nuclear and film boiling) and transition phase of fluids under reduced gravity such as Lunar, Martian or micro-gravity. The volume of liquid oxygen levitated is about two litres with a resulting acceleration less than 0.1 m/s2. Besides the aspect ratio of the working cell can be changed.

Three clays from Gounioube deposits were used for the manufacture of floor tiles. The strength distributions by the Weibull statistical model are interpreted in relation to clay chemical and mineralogical compositions and particularly to the iron role by Mossbauer spectroscopy. With clays without additions, results of mechanical strength of sintered materials show that clays alone are not really suitable for the manufacture of ceramics. But clay calcite mixes (10 wt% of CaCO 3 ) favor a significant increase of mechanical resistance, which are similar to used standards. This behavior is due to the formation of a three-dimensional network of anorthite crystals within the silico-aluminate materials. Beside the anorthite role, the iron oxide content of the clays influences the mechanical strength. With Gounioube clays, it is shown that the increase of iron content in clays causes a decrease of the ceramic strength. This behavior is related to the clay compositions, which contain iron in the form of goethite. During the thermal transformations, part of the iron is involved in both the structural transformations and the densification phenomenon of the silico-aluminate phase. But the most part of iron readily transforms into hematite crystallites, which are embedded within the silico-aluminate. They accentuate the heterogeneous nature of the material and favor the decrease of the mechanical strength.

The theory for metal speciation dynamics in dilute, monodisperse suspensions of spherical core-shell colloidal ligand particles is extended with the impact of the electric double layer (EDL) field and inhomogeneous site distribution inside the particle. The latter is defined by a diffuse, radial distribution for the density of charged polymer segments supporting the ligands L. The site distribution at the scale of the particle suspension and within the colloidal shell results in association/dissociation rate constants (denoted as k(a)* and k(d)*, respectively) that may significantly differ from their homogeneous solution counterparts (k(a) and k(d)). The differences arise from intertwined kinetics of metal-ligand (ML) complex formation/dissociation in the particle shell and diffusive transport of free metal ions M within/outside the shell in the electric field set up by the EDL at the core-shell/electrolyte interphase. The relationship between k(a,d)* and k(a,d) is derived from the numerical evaluation of the spatial, time-dependent distributions of free and bound metal as governed by coupled Nernst-Planck equations corrected by appropriate chemical source term and written in a Kuwabara cell geometry. The average interphasial electrostatic field stemming from the formation of the EDL at the complexing colloidal interphase is obtained from the solution of the nonlinear Poisson-Boltzmann equation. The EDL composition is exclusively governed by ions from indifferent background electrolyte present in large excess over free metal species M. The dependences of k(a,d)* on rate constants k(a,d), geometrical details of particle, particle charge, concentration of indifferent background electrolyte, and ligand distribution within the shell are thoroughly discussed within the context of dynamic features for colloidal complex systems. Examination of the chemical equilibrium regime allows addressing explicitly the impact of electrostatics on colloidal complex stability (polyelectrolyte effect). The numerical study is further supported by an approximate analytical expression based on Donnan partitioning and valid under the quasi-steady-state approximation (nonequilibrium chemical regime). The analysis covers the limiting cases of charged rigid particles where binding sites are located at the very surface of the core (e.g., functionalized latex colloids) and polyelectrolyte particles devoid of a hard core (e.g., polysaccharide macromolecules, gel particles).

International audience; On the basis of particle size distributions, bulk chemical and mineralogical compositions and firing properties, this paper outlines an assessment of the industrial suitability of Mayouom kaolin deposit for sustainable development. The characteristics of the studied samples compared to some standards indicate that these kaolins are high quality industrial clays. Firing yielded good results for white firing ceramics and for refractory ceramics. For other industrial uses, a treatment by purification and titanium removal is necessary to improve their suitability.

The Fensch River (FR) is one of the most contaminated rivers in France due to the population density and the concentration of industrial activities in this small watershed area. From upstream to downstream, the organic matter extracted from sediments has been analyzed by gas chromatography–mass spectrometry and molecules have been quantified and classified into natural, petrogenic, pyrogenic and sewage water (SW) markers. Upstream the river, anthropogenic molecules are already predominant and represent 87.1% of the molecules quantified. This proportion increases from upstream to downstream and rises to 96.8% at the confluence of the FR with the Moselle River. In the upper part of the FR the contamination is mainly due to human waste (coprostanol: 36.44 µg/g; 42.1% of anthropogenic markers). In the lower part, the contribution of SW markers decreases from 42.1 to 2.4% and the proportion of pyrogenic molecules increases from 29.6 to 59.6%. The major sources of pyrogenic organic matter have been determined by calculation of specific ratios on polycyclic aromatic hydrocarbons and by comparison with reported data. Coal tar, road runoff and atmospheric depositions of urban particles seem to be the major pyrogenic sources. Along the river, the proportion of petrogenic molecules remains constant and those molecules seem to be mainly inherited from road runoff, in the upper part of the FR. Industrial lubricants that occur in steel plant sludge are an additional source in the lower part of the river.

In order to assess the evolution of the confinement properties of clay engineered barriers (EBS) when in contact with metallic canisters containing radioactive wastes, Fe(0)-bentonite interactions need to be assessed. "45 days-80 °C" tests were performed using powdered FoCa7 bentonite and metallic iron. Since one fundamental parameter may be the available quantity of Fe(0), a wide range of Iron/Clay mass ratios (I/C) from 0 to 1/3 is used. The confinement power of clay material results from the swelling properties and the retention capacity. Thus, the major criterion which is chosen to assess the evolution of the confinement properties in this study is the variation of Cation Exchange Capacity (CEC). In parallel, the physico-chemical evolution of bentonite is studied using XRD and EDS-TEM microanalyses. The evolution of the distribution of iron environments is obtained by 57Fe Mössbauer spectroscopy. This study evidences that both kaolinite and smectite from the bentonite are altered into SiAlFe gels when in contact with Fe(0). These gels maturates into Fe-rich di-trioctahedral phyllosilicates, whose composition is bounded by the one of odinite and greenalite in a Fe-M+-4Si diagram when I/C = 1/3. Most of all, it is evidenced that the reaction depends on the available quantity of Fe(0). When the I/C ratio is between 1/30 and 1/7.5, the exchange capacity of FoCa7 bentonite starts decreasing, the consumption of Fe(0) becomes significant, the alteration of smectites occurs and secondary oxides are formed. The crystallization of Fe-rich phyllosilicates is observable when I/C ratio is higher, from a threshold between 1/7.5 and 1/5. Above I/C = 1/3.75, initial iron oxides are strongly consumed and participate in the incorporation of Fe2+ and Fe3+ in gels or new phyllosilicates octahedra. These experimental results were used as input data for the prediction of the long-term evolution of the EBS using Crunch reaction-transport model. © 2007 Elsevier B.V. All rights reserved.

Since 1996, experimental and modeling approaches have led to the understanding of the main mechanisms controlling the Opalinus Clay pore water composition. By 2003, one of the main remaining uncertainties concerned the carbonate system. Consequently, to reduce this uncertainty, an innovative device for pore water sampling was implemented in 2004 in the Mont Terri Rock Laboratory. An ascending borehole was dry-drilled, using only N 2 gas and aseptic tools to avoid rock oxidation and microbiological perturbation. The borehole equipment allowed the circulation of gas, initially pure argon, in contact with the rock in a closed circuit and the sampling of formation water produced in the test interval. This experiment made it possible to monitor the composition of the circulating gas over several months and to collect seepage water at a flow rate close to 3 mL/day over more than 3 years. The sampled water composition remained stable over time and coherent with the previous understanding. CO 2 partial pressures calculated from water analyses are between 10 −2.4 and 10 −1.7 bar. Modeling of the evolution of CO 2 concentration in the circulating gas involved advection, diffusion, calcite precipitation and proton buffering surface processes. CO 2 partial pressure deduced from water analyses is a few mbars higher than that measured on the gas. Calcium carbonate precipitation and capillary effects could explain this discrepancy.

The lipidic fraction from 8 sediments sampled at the confluence between the Fensch River (FR) and the Moselle River (MR) have been analyzed by gas chromatography-mass spectrometry (GC-MS) in order to investigate the transfer of organic micropollutants from the FR to the MR. Molecular markers have been quantified and classified into five categories: natural, petrogenic, pyrogenic and sewage water markers and non-specific molecules. This classification coupled with the quantification of the molecules allows the comparison between anthropogenic and natural inputs and the source apportionment of anthropogenic molecules that are not covalently bound to sedimentary organic macromolecules. The transfer and the fate of organic micropollutants in river sediments seem to be controlled by the water flow. Low water flow conditions induce the settling of fine particles, which could limit the biodegradation. This leads to the preservation of the original anthropogenic fingerprint that is rich in low molecular weight molecules. In high water flow conditions, sediments are mainly composed of coarse particles, limiting the preservation of organic matter, which leads to a persistent anthropogenic fingerprint, mainly composed of high molecular weight compounds.

International audience; Optical microscopy, confocal Raman micro-spectrometry, X-ray photoelectron micro-spectroscopy (XPS) and synchrotron based micro-X-ray fluorescence (XRF), micro-X-ray absorption near edge spectroscopy (XANES) and micro-extended X-ray absorption fine structure (EXAFS) were used to investigate the reduction of aqueous Cr(VI) by pyrite. Special emphasis was placed on the characterisation of the solid phase formed during the reaction process. Cr(III) and Fe(III) species were identified by XPS analyses in addition to non-oxidised pyrite. Optical microscopy images and the corresponding Raman spectra reveal a strong heterogeneity of the samples with three different types of zones. (i) Reflective areas with Eg and Ag Raman wavenumbers relative to non-oxidised pyrite are the most frequently observed. (ii) Orange areas that display a drift of the Eg and Ag pyrite vibration modes of −3 and −6 cm−1, respectively. Such areas are only observed in the presence of Cr(VI) but are not specifically due to this oxidant. (iii) Bluish areas with vibration modes relative to a corundum-like structure that can be assigned to a solid solution Fe2−xCrxO3, x varying between 0.2 and 1.5. The heterogeneity in the spatial distribution of chromium observed by optical microscopy and associated Raman microspectroscopy is confirmed by μ-XRF. In agreement with both solution and XPS analyses, these spectroscopies clearly confirm that chromium is in the trivalent state. XANES spectra in the iron K-edge pre-edge region obtained in rich chromium areas reveal the presence of ferric ion thus revealing a systematic association between Cr(III) and Fe(III). In agreement with Raman analyses, Cr K-edge EXAFS can be interpreted as corresponding to Cr atoms involved in a substituted-type hematite structure Fe2−xCrxO3.

The Moselle river flows in the north-east of France, from Vosges Mountains to neighboring countries Luxembourg and Germany. One of its tributaries, the Fensch river, drains a highly industrialized watershed, strongly impacted by mining, smelting and surfacing activities. The objective of this work, part of a general research program on Moselle watershed (Zone Atelier Moselle) was to assess the impact of the polluted Fensch river on the global quality of the Moselle river. For that purpose, water, sediments and suspended particulate matter were sampled in both rivers, upstream and downstream the junction. Four main sampling campaigns were carried out, in winter during a flood event and in spring at low water level. On a first step, mineralogical analyses (XRD and FTIR) and chemical analyses (ICP-MS, ICP-AES), were performed on sediments, suspended particulate matters and filtered waters. Major and trace elements concentrations were obtained on two different granulometric fractions (0–2 mm and 0–50 μm) revealing the enrichment in heavy metals of fine particles. From one collecting campaign to another, seasonal variations could be evidenced on suspended matter composition even though major minerals (calcite, quartz and kaolinite) were always present. Furthermore, spatial variations were evidenced for Fensch and Moselle downstream sediments. Thus, very fine-grained sediments, poorly crystallized, displaying at the same time higher metal concentrations and higher organic matter content than in Fensch river material, were collected downstream, in a low hydrodynamic conditions zone, assumed as a preferential sedimentary zone or even as a placer. Strong correlations could be revealed between iron content and contaminant concentrations, confirming the origin of polluted material.

International audience; Smectite hydration strongly influences dynamical properties of interlayer cations and thus the fate of H2O and pollutants in surficial systems where smectite-based materials are often used as a major barrier component. Smectite crystal chemistry is known to rule its hydration, although the influence of specific parameters such as the amount and location of layer charge deficit remains poorly understood. A set of tetrahedrally charged trioctahedral smectites, with a common structural formula (inter)[Na-x](oct)[Mg-6](tet)[Si(8.0-x)Alx(])O(20)(OH,F)(4) and a layer charge (x) varying from 0.8 to 3.0, were thus synthesized to assess the influence of layer charge on smectite hydration and interlayer structure. Both hydroxylated and fluorinated samples were synthesized because of the increasing use of the latter varieties in recent spectroscopic studies aiming at the determination of interlayer H2O dynamical properties. The distribution of charge-compensating cations and of associated H2O molecules was determined both experimentally from the modeling of X-ray diffraction patterns and numerically from Monte Carlo molecular simulations performed in the grand canonical ensemble. The consistency of both approaches for hydroxylated samples allowed gaining insights into the specific influence of smectite crystal chemistry. For a given hydration state, H2O content is about constant in hydroxylated saponites, independent of layer charge, whereas smectite layer-to-layer distance decreases with increasing layer charge because of the enhanced cation-layer electrostatic attraction. As a result, positional disorder of interlayer H2O molecules is reduced because of stronger steric constraints and of the increased density of electronegative sites at the surface of the clay layer. Fluorine-for-hydroxyl isomorphic substitutions likely increase further electronegativity of the clay layer surface leading to further reduction of the interlayer H2O content and to the formation of Na+ inner sphere complexes at the clay layer surface. When normalized to the number of interlayer cations, the number of interlayer H2O molecules decreases with increasing layer charge, and the proportion of these H2O molecules hydrating interlayer cations increases, thus increasing the stability of most hydrated states toward lower relative humidity conditions. Smectite hydration evolution appears as a steady process with no tendency to interlayer cation ordering at the smectite-to-vermiculite limit of similar to 1.3 charge per O-20(OH,F)(4).

Long-range electrostatic forces substantially influence bacterial interactions and bacterial adhesion during the preliminary steps of biofilm formation. The strength of these forces depends strongly on the structure of the bacterium surfaces investigated. The latter may be addressed from appropriate analysis of electrophoretic mobility measurements. Due to the permeable character of the bacterium wall and/or surrounding polymer layer, bacteria may be regarded as paradigms of soft bioparticles. The electrophoretic motion of such particles in a direct-current electric field differs considerably from that of their rigid counterparts in the sense that electroosmotic flow takes place around and within the soft surface layer. Recent developments of electrokinetic theories for soft particles now render possible the evaluation of the softness degree (or equivalently the hydrodynamic permeability) from the raw electrokinetic data. In this article, the electrophoretic mobilities of three Shewanella strains (MR-4, CN32, and BrY) presenting various and well-characterized phenotypes of polymer fringe are reported over a wide range of pH and ionic strength conditions. The data are quantitatively analyzed on the basis of a rigorous numerical evaluation of the governing electrostatic and hydrodynamic equations for soft particles. It is clearly shown how the peculiar surface structures of the bacteria investigated are reflected in their electrohydrodynamic properties.

Due to the complexity of the humic substances (HS), mathematical models have often been employed to understand their roles in the environment. Since no consensus exists with respect to the structure and conformation of the HS, models have alternatively given them properties corresponding to impermeable hard spheres or fully permeable polyelectrolytes. In this study, the hydrodynamic permeability of standard HS (Suwannee River fulvic, humic, and peat humic acids) are evaluated as a function of pH and ionic strength. A detailed theoretical model is used to determine the softness parameter (lambda0), which characterizes the degree of flow penetration into the HS on the basis of measured values of electrophoretic mobilities, diffusion coefficients, and electric charge densities. Their motion in an electric field is evaluated by a rigorous numerical evaluation of the governing electrokinetic equations for soft particles. The hydrodynamic impact of the polyelectrolyte chains is accounted for by a distribution of Stokes resistance centers and partial dissociation of the hydrodynamically immobile ionogenic groups distributed throughout the polyelectrolyte. The results demonstrate thatthe studied HS are small (radius ca. 1 nm), highly charged (500-650 C g(-1) when all sites are dissociated), and very permeable (typical flow penetration length of 25-50% of the radius, depending on pH). The HS also coagulate slightly when lowering the pH of the solution. Modeling of the HS as hard spheres with a charge and slip plane located at the surface is thus physically inappropriate, as are a number of analytical theories for soft particles that hold for low to moderate electrostatic potentials and large colloids. The shortcomings of these simpler approaches, when interpreting the electrophoretic mobilities of HS, are highlighted by comparison with rigorous theoretical predictions.

The theory based on the 1-pK triple layer model of the oxide/electrolyte interface is used to obtain the derivative of a proton adsorption isotherm. The present approach is much more rigorous and complex from a physical point of view compared to our previous paper [J. Phys. Chem. B. 106 (2002) 13280]. In the present work we take into account adsorption of inert electrolyte ions. Also, the present approach takes into consideration the local surface heterogeneity. The aim of this work is not to propose new surface model, but to develop a theoretical basis for obtaining of proton affinity distribution from the derivatives of a potentiometric titration curve. We demonstrate how including of electrolyte ion adsorption influences on the shape and behavior of the local derivatives of potentiometric titration curves. The influence of the other parameters is also thoroughly investigated. It was found that complete description of the derivative of surface charging curve requires a high number of parameters. Therefore, it is difficult to adopt the obtained peaks for unambiguous decomposition of experimental derivative of a titration curve onto the parts coming from different patches of the surface.

A novel method for the quantitative evaluation of the amount of interstitial elements in solid solution in a ferritic matrix was developed. It is based on thermoelectric power measurements and uses the segregation of the free interstitial elements to the dislocations occurring during the static strain ageing of a cold-rolled steel.

FTIR spectroscopy has been applied to NH4+-exchanged dioctahedral clay minerals to determine the molecular environment of NH4+ and to quantify N concentration. FTIR under vapourpressure control, coupled with heating and freezing treatments has shown that NH4+ ion symmetry varies with the nature of clay minerals. NH4+ has a perfect tetrahedral symmetry in hydrated or dehydrated smectites and belongs to the Td symmetry group. The NH4+-bending vibration is centred at 1450 and 1425 cm–1.The Si4+-Al3+ substitution in dioctahedral clay minerals induces the loss of symmetry elements of the NH4+ tetrahedron which acquires a C2v symmetry. As a consequence, the Td –C2v transition can be used to characterize the smectite–illite transition. Quantification of NH4+ content per half unit cell is provided by nNH4 = k[NH4]/[OH] where [NH4]/[OH] is the band area ratio of the NH4+-bending vibration to the OH-stretching vibration. k = 1.1 for hydrated smectite, 0.9 for dehydrated smectite and 0.8 for illite or tobelite. The bending vibration of NH4+ is chosen for the calculation because it is not affected by superimposed contributions.

International audience; The theory based on the complexation model has been used to derive the adsorption isotherm equation describing proton adsorption at the solid/electrolyte interface. The present equation applies to the 1-pK theory developed by Hiemstra and co-workers to describe oxide/electrolyte interfaces. Development has also been performed to take into account the local surface heterogeneity (i.e., the local pK distribution). It has then been shown that whatever the assumption, all the equations degenerate into a single derivative isotherm equation as the local surface potential and the heterogeneity parameters merge into one parameter. The obtained derivative equation has been used to model experimental high-resolution titration curves realized on anatase and goethite by using the titration derivative isotherm summation (TDIS) method proposed by Prelot and co-workers. The comparison between the fits obtained with this model and the Bragg−Williams−Temkin model shows that very similar quantitative results (peak position, adsorbed amounts) can be obtained. The present approach is, however, considered to be more realistic from a physical point of view.

A good knowledge of powder flow properties is necessary to consider industrial application of a system. Flowability is a complex combination of different parameters like size, shape or surface properties of particles. The goal of this study is to compare the impact of two drying techniques (freeze-drying and spray drying) on powder flowability in order to choose the most appropriate device. Powder is first studied at the particle level with size measurements and shape description. Then, the global behaviour is characterised by water content, water up-take and physicochemical analysis. Finally, the influences of two additives and of coating on powder flow properties have been investigated. The two powders obtained by spray and freeze-drying vary principally by the shape of the particles. Residual water content, moisturising capacity and surface properties are similar. In both cases, powder flowability is bad. Results obtained with the two additives show no improvement of powder flow properties. However, coating reduces the number of fine particles and, as a consequence, improves powder flowability with furthering particle motion.

Adsorption processes are extensively used for the selective removal of trace elements from drinking water. They must be designed not only with equilibrium data but also with mass-transfer data. Indeed, this paper investigates the transport of arsenate in natural manganese oxide columns. Column experiments were run at different conditions of particle sizes and flow rates, including an interrupted-flow experiment. The breakthrough curve analysis showed that transport was affected by nonlinear adsorption and intraparticle diffusion. Nonconventional features were observed, such as the variation of the total adsorption capacity with the flow rate and with the particle size. They were attributed to the complex porous structure of the grains. Results were interpreted by means of a transport model including Langmuir adsorption and mass transfer, with a single adjustable parameter: the effective diffusivity of arsenate in the grain. This parameter included both adsorption and diffusion. In a second step, diffusivities including intraparticle diffusion alone were calculated. Values between 0.6 and 7.0 x 10(-11) m(2) s(-1) were found; they were close to published data of the pore diffusivity of arsenate in activated alumina grains. Moreover, the model, despite its simplicity, succeeded in predicting the breakthrough points of arsenate at different flow rates with a single value of the effective diffusivity. This modeling approach is of great importance for the design of adsorption processes for arsenate removal from drinking water.

Effects of ultrasound (US) on the structural organization within concentrated particle layers during cross-flow ultrafiltration of Laponite dispersions have been characterized for the first time by in-situ time-resolved small-angle X-ray scattering (SAXS). A novel ‘SAXS Cross-Flow US-coupled Filtration Cell’ has been developed to, on one hand, apply ultrasonic waves close to the flat membrane by embedding in the feed compartment a thin titanium vibrating blade connected to a 20 kHz ultrasonic generator and on the other hand, to monitor in-situ the colloidal organization of the concentrated layer by SAXS. Thanks to this cell, concentration profiles have been measured as a function of the distance z from the membrane surface with a 20 µm accuracy and simultaneously linked to the permeate flux, cross-flux and transmembrane pressure. In-situ ultrasonication leads to a significant increase of permeate flux arising from the break-up of the concentrated layer. Results also suggest that ultrasonication could be considered as an additional force of an effective range on the order of micrometers or smaller. It is capable to completely remove the particles from the membrane surface when the feed dispersions are dense and aggregated, and is more efficient than classical procedures based on an increase of the cross-flow flux.

International audience; Prior to the CO2 injection in the Rousse pilot operated by TOTAL Exploration Production France, baseline monitoring has been performed in near surface environments in order to characterize soil gas concentrations and soil gas fluxes behavior along with time. The baseline measurements were conducted in 2008 and 2009 on a quarterly basis. All investigations were performed under weather conditions representative of temperate climate yearly cycles. CO2 fluxes and CO2 soil concentrations followed an annual cycle with enhanced emissions during high season (summer) and lower emissions during low season (winter) corresponding with the annual cycle of biological activity in soil. The CO2 is predominantly of organic origin with atmospheric dilution during low season times with an absence of an upward gas flux as suggested by nearly constant helium concentrations in soils and depleted carbon-13 isotope ratios. Even considering quite long baseline monitoring, it is not possible to find a significant correlation between the flux measured at the soil/atmosphere interface and the concentration measurements at 1 m depth. From the knowledge gained at the site, a monitoring strategy is proposed in order to match both scientific and operator requirements.

International audience; Unravelling details of charge, structure and molecular interactions of functional polymer coatings defines an important analytical challenge that requires the extension of current methodologies. In this article we demonstrate how streaming current measurements interpreted with combined self consistent field (SCF) and soft surface electrokinetic theories allow the evaluation of the segment distribution within poly(ethylene oxide) (PEO) brushes beyond the resolution limits of neutron reflectivity technique.

International audience; The goal of the present study was to investigate the interfacial phenomena that govern the interactions between Cryptosporidium parvum oocysts and synthetic filtration media, in order to define guidelines to improve the choice of appropriate materials and filtration-elution conditions. Three frequently used filtration media were studied: polycarbonate and cellulose-ester membranes, and a polyethersulfone cartridge. The electrokinetic potential of Cryptosporidium oocysts and of the filtration media were measured by electrophoresis and streaming potential, respectively. Aqueous media such as dilutions of a phosphate buffer (PBS), NaCl, CaCl2 at various concentrations and pH, were tested. The highest recovery rates, close to 100%, were obtained in conditions where the electrokinetic potentials of both the membrane and the oocysts were at maximum negative values. This condition was met using a polycarbonate membrane and low concentrations of monovalent salt. The media generally used in microbiology, such as phosphate buffer or 8 g l−1 KCl or NaCl, caused irreversible adhesion and dramatic decrease in recovery rates.

The effect of temperature on the oxychlorination of Cr 2 O 3 and MgO using Cl 2 +O 2 was evaluated using non-isothermal conditions. A mathematical treatment of the experimental data was performed. Results were compared with those obtained using isothermal conditions. The oxychlorination of Cr 2 O 3 up to 650°C was characterized by an apparent activation energy ‘ E a ’ of ca. 83 kJ/mol. Beyond 650°C, the reaction proceeded with an E a of ca. 51 kJ/mol. Between 850 and 1025°C, the reaction of MgO with Cl 2 +O 2 was strongly dependent on temperature and its E a was equal to ca. 215 kJ/mol. The values of the apparent activation energies, found for the oxychlorination of both oxides using non-isothermal conditions, were comparable to those obtained during isothermal treatment.

Applications based on cantilever sensor technology like atomic force microscopy, mass spectroscopy, magnetic resonance force microscopy, and other physical or chemical sensing techniques demand theoretical understanding of sensing and actuation mechanism. Moreover reliable calibration of any instrumentation is necessary in order to enable comparison of obtained results between various laboratories. When mass or force investigations are performed in nanoscale the reliable system calibration is even more difficult due to the lack of appropriate references and established metrological techniques. In this article we present the calibration methodology of thermally driven piezoresistive cantilevers which were used for mass and force measurements. We adapt the mass loading spring constant calibration method and compare the results obtained in this way with the method which was based on the resonance frequency detection. Additionally we will present results of the cantilever deflection sensitivity measurement and low-frequency noise properties.

International audience; The carbochlorination of a chromite concentrate was studied between 500 °C and 1000 °C using boat experiments. The reaction products were analyzed by scanning electron microscopy (SEM), x-ray diffraction (XRD), and chemical analysis. The carbochlorination of a chromite concentrate at about 600 °C led to the partial selective elimination of iron, thus increasing the Cr/Fe ratio in the treated concentrate. Total carbochlorination of the chromite concentrates and volatilization of the reaction products was achieved at temperatures higher than 800 °C. The kinetics of the chromite carbochlorination was studied between 750 °C and 1050 °C using thermogravimetric analysis (TGA). The results were discussed in terms of the effects of gas flow rate, temperature, partial pressure of Cl2+CO, and Cl2/CO ratio on the carbochlorination process. It was observed that the temperature effect changed significantly with the progress of the reaction. The initial stage of the carbochlorination was characterized by an apparent activation energy of about 135 and 74 kJ/mol below and above 925 °C, respectively, while a value of about of 195 kJ/mol was found for the remainder of the carbochlorination process.

International audience; The reactivities of olivine and serpentine towards mixture of chlorine in air, nitrogen and carbon monoxide were studied in non-isothermal conditions up to 1000°C. The samples were also chlorinated in a horizontal reactor over 2 h between 500° and 1000°C, under oxidizing and reducing atmospheres. The chlorination products were examined by XRD and SEM.The iron-bearing compounds contained in the natural olivine and serpentine samples can be eliminated through chlorination or oxychlorination of these solids at temperatures lower than 900°C. Carbochlorination of olivine and serpentine is incomplete even at 1000°C for a reaction time of 2 h. Pure magnesium chloride can be recovered by cooling the gas phase at ca. 500°C.

International audience; Synthetic saponites with various Cationic Exchange Capacities were aggregated at pH 8.0 in a stirred vessel by hydrolyzed aluminum species. Floc growth was followed by Fraunhoffer laser diffraction and the efficiency of clarification was assessed from conventional residual turbidity and sediment volume measurements. We show that the aggregation mechanisms are layer-charge dependent and can not be described by the widely accepted sweep flocculation model.