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International audience; The purpose of this research is to fill knowledge gaps on the relevance of solvent substitution from a life cycle perspective and to put forth relevant operating conditions for possible process optimisation and eco-design. Solvents commonly used to prepare ultrafiltration membranes for drinking water applications are indeed identified by the European REACH regulation for their potential reproductive toxicity and are the subject of research as regards their substitution. Coupling Life Cycle Assessment (LCA) with process modelling allowed to compare conventional membranes (cellulose triacetate as polymer, NMP as solvent) to biosourced membranes (cellulose diacetate as polymer, methyl lactate as solvent). Although methyl lactate fabrication leads to lower environmental scores than NMP fabrication (32% and 10% less GWP100 and ReCiPe Endpoint, respectively), LCA scores for membrane fabrication are similar (1.9 points ReCiPe for 1 m(2) membrane) or slightly different, i.e. 11 kg CO2-eq and 9.4 kg CO2-eq for 1 m(2)& nbsp;of conventional and biosourced membrane, respectively. From an environmental point of view, solvent substitution has little influence on impacts. Rather, environmental hotspots lie in the operation stage, with impact scores about 10,000 times higher than those of membrane fabrication, which holds out considerable prospects for the optimisation of operating conditions on drinking water plants.

Membrane filtration performances can be enhanced by the deposition of a selective thin layer on the surface of a porous substrate. Our simulation focus on the deposition of nanometric bicontinuous microemulsions onto hollow-fibre membranes and its polymerisation using UV modules. To that end, the laws governing the deposition of linear liquids have been extended to the study of the deposition of microemulsions. Our simulation highlights the difficulty of depositing a thin liquid coating on the fibre without causing its capillary penetration into the porosity of the substrate, due to the very low surface tension of microemulsions.

International audience; The purpose of the research is to make a first step towards rationalizing green polymeric membrane preparation. A holistic methodological approach based on metrics that consider technical, environmental, health and safety issues have been suggested to assess sustainability of membrane preparation. Metrics have been applied to solvent substitution in a non-solvent induced phase separation process. The flammability hazard of three shortlisted alternative solvents has substituted the reprotoxicity hazard of common solvents. The ultrafiltration cellulose diacetate membranes prepared with methyl lactate as solvent have a greater renewable intensity and require a lower number of solvents for their preparation. Trade-offs between use of resources (polymer, solvent, energy…) and membrane properties are inevitable. Further socio-economic, risk and life cycle analysis are crucial to fully integrate ecodesign in membrane preparation.

International audience; The purpose of the research is to elaborate and implement a decision-making tool for greener membrane fabrication. The scientific novelty put forth in this study is the generic process modelling – LCA approach applied to the field. The resulting parameterized model allows to obtain material and energy flows as a function of operating conditions for ultrafiltration hollow fibers prepared by non-solvent induced phase separation. Its modular configuration allows for flexibility and adaptation to various membrane materials and industrial practices. Contributions of inputs on environmental impacts can be assessed, as well as the influence of operating conditions. Results for cellulose acetate membranes show major contributions of NMP (i.e. solvent) and glycerol (i.e. pre-conditioning liquid). Improvement strategies for environmental mitigation include acting on glycerol-related operating conditions and are to be considered within the geographic context of membrane fabrication; further technical and economic feasibility studies would embed these strategies in a full eco-design approach. Such a methodology and results should be taken into account for the elaboration of “green membranes” whatever the application and coupled with the impact of membrane use and end-of-life.

International audience; Polymeric flat-sheet membranes and hollow fibers were prepared via UV photo-initiated polymerization of acrylic acid at the surface of commercial polyether sulfones (PES) membranes. These polymeric materials permitted to immobilize efficiently palladium nanoparticles (PdNP), which exhibited a mean diameter in the range of 4−6 nm. These materials were synthesized by chemical reduction of Pd(II) precursors in the presence of the corresponding support. We successfully applied the as-prepared catalytic materials in hydrogenation reactions under continuous flow conditions. Flat sheet membranes were more active than hollow fibers due to the flow configuration and defavorable operating conditions. Actually, various functional groups (i.e. CC, CC and NO2) were reduced in flow-through configuration, under mild conditions (between 1.4 and 2.2 bar H2 at 60 °C, using 3.2 mol% of Pd loading), archiving high conversions in short reaction times (12−24 s).

International audience; Researchers and industrials need decision-making tools to make informed decisions on environmental mitigation strategies and proceed with the overall ecodesign of processes. In this study, a tool that couples membrane filtration process modelling and life cycle analysis has been developed, for which material and energy flows are calculated for variable operating conditions and are the basis for environmental impact assessment. The resulting generic model has been applied to dead-end ultrafiltration of ground and surface waters for drinking water production with cellulose triacetate hollow fibers. Operating strategies have been investigated to mitigate environmental impacts of the two major hotspots (electricity and backwash cleaning chemical consumptions). Adjusting filtration cycle duration and filtration flux has shown to be a promising lever. The developed model is sufficiently flexible and modular for its adaptation to other membrane materials, filtration configurations (i.e. cross-flow) as well as to other applications. Highlights-Novel decision-making tool for filtration developed at a unit operation level.-Extensive operating conditions and input water categories as model variables.-Environmental impacts as sensitive to operating conditions as to electricity mix.-Easy combination possible with existing fabrication model for cradle-to-grave LCA.

International audience; In this paper, we developed membrane scaffolds to mimic the biochemical and biophysical properties of human mesenchymal stem cell (hMSC) niches to help direct self-renewal and proliferation providing to cells all necessary chemical, mechanical and topographical cues. The strategy was to create three-dimensional membrane scaffolds with double porosity, able to promote the mass transfer of nutrients and to entrap cells. We developed poly (Ɛ-caprolactone) (PCL)/chitosan (CHT) blend membranes consisting of double porous morphology: (i) surface macrovoids (big pores) which could be easily accessible for hMSCs invasion and proliferation; (ii) interconnected microporous network to transfer essential nutrients, oxygen, growth factors between the macrovoids and throughout the scaffolds. We varied the mean macrovoid size, effective surface area and surface morphology by varying the PCL/CHT blend composition (100/0, 90/10, 80/20, 70/30). Membranes exhibited macrovoids connected with each other through a microporous network; macrovoids size increased by increasing the CHT wt%. Cells adhered on the surfaces of PCL/CHT 100/0 and PCL/CHT 90/10 membranes, that are characterized by a high effective surface area and small macrovoids while PCL/CHT 80/20 and PCL/CHT 70/30 membranes with large macrovoids and low effective surface area entrapped cells inside macrovoids.The scaffolds were able to create a permissive environment for hMSC adhesion and invasion promoting viability and metabolism, which are important for the maintenance of cell integrity. We found a relationship between hMSCs proliferation and oxygen uptake rate with surface mean macrovoid size and effective surface area. The macrovoids enabled the cell invasion into the membrane and the microporosity ensured an adequate diffusive mass transfer of nutrients and metabolites, which are essential for the long-term maintenance of cell viability and functions.

International audience; Tissue engineering is an interdisciplinary field, wherein scientists from different backgrounds collaborate to address the challenge of replacing damaged tissues and organs through the in vitro fabrication of functional and transplantable biological structures. Because the development and optimization of tissue engineering strategies rely on the complex interaction of cells, materials, and the physical–chemical tissue microenvironment, there is a need for experimental models that allow controlled studies of these aspects. Organs-on-chips (OOCs) have recently emerged as in vitro models that capture the complexity of human tissues in a controlled manner, while including functional readouts related to human organ physiology. OOCs consist of multiple microfluidic cell culture compartments, which are interfaced by porous membranes or hydrogels in which human cells can be cultured, thereby providing a controlled culture environment that resembles the microenvironment of a certain organ, including mechanical, biochemical, and geometrical aspects. Because OOCs provide both a well-controlled microenvironment and functional readouts, they provide a unique opportunity to incorporate, evaluate, and optimize materials for tissue engineering. In this study, we introduce a polymeric blend membrane with a three-dimensional double-porous morphology prepared from a poly(ɛ-caprolactone)–chitosan blends (PCL–CHT) by a modified liquid-induced phase inversion technique. The membranes have different physicochemical, microstructural, and morphological properties depending on different PCL–CHT ratios. Big surface pores (macrovoids) provide a suitable microenvironment for the incorporation of cells or growth factors, whereas an interconnected small porous (macroporous) network allows transfer of essential nutrients, diffusion of oxygen, and removal of waste. Human umbilical vein endothelial cells were seeded on the blend membranes embedded inside an OOC device. The cellular hydraulic resistance was evaluated by perfusing culture medium at a realistic transendothelial pressure of 20 cmH2O or 2 kPa at 37°C after 1 and 3 days postseeding. By introducing and increasing CHT weight percentage, the resistance of the cellular barrier after 3 days was significantly improved. The high tuneability over the membrane physicochemical and architectural characteristics might potentially allow studies of cell–matrix interaction, cell transportation, and barrier function for optimization of vascular scaffolds using OOCs.

Optimization of the backwash operating conditions for a specific membrane-feed system can become an initial step to reduce energy and ultrafiltrated water consumption. In this work, fouling removal mechanisms of bentonite cakes were investigated on ultrafiltration Kynar® polyvinylidene fluoride (PVDF) hollow fibre membranes having different dimensions, mechanical and surface properties and water permeability. The study on different bentonite cake structures, formed in dead-end filtration at constant pressure and in outside-in mode, has demonstrated that cake removal mechanism was mainly governed by the backwash flux and not by the intrinsic membrane properties. We define a critical backwash flux, from which backwash becomes efficient. The critical backwash is related to a critical inter cake-membrane pressure which occurs at the cake-membrane interface during backwash, which really acts on the deposit. A fouling removal mechanism is thus proposed involving three steps related the critical inter cake-membrane pressure. The critical inter cake-membrane pressure required for an efficient backwash was independent of the membrane properties and bentonite hydraulic resistance. The critical backwash flux can be used to optimize the energy efficiency of the ultrafiltration process.

Hollow fiber membrane contactors with ionic liquids are promising alternatives to traditional spray towers and amines for carbon dioxide absorption. Ionic liquids have emerged as new alternative solvents because of their zero emission features compared with amines. The aim of this work was to compare fibers based on PVDF and different additives, as well as fibers including two different ionic liquids. On the one hand, 1-ethyl-3-methylimidazolium ethyl sulfate [emim][EtSO4] presents physical absorption, and on the other hand, 1-ethyl-3-methylimidazolium acetate [emim][Ac] presents chemical absorption. To compare the fibers under study, the thickness of the composite fiber was examined using scanning electron microscopy (SEM). The mechanical properties and the bubble point were also evaluated. Permeability tests were conducted, and the gas permeation of the composite hollow fibers was measured using pure CO2. Laboratory-made stainless steel modules were used for the tests. All of the above tests were performed with the fibers in both wet and dry conditions. It was determined that the fibers with the ionic liquid immobilized would be promising for CO2 capture because the CO2 permeance significantly increased. Namely, D+[emim][EtSO4] achieved a 43% increase compared with the fibers without the addition of the ionic liquid, resulting in a CO2 permeance value of 57040NL/(hm2bar), which is higher than the values reported in the literature for PVDF. Moreover, the overall mass transfer coefficient for CO2 capture using the D+[emim][Ac] fibers also presented highly competitive values. This research has been funded by the Spanish Ministry Economy and Competitiveness (Projects ENE2010-14828 and CTQ2013-48280-C3-1-R).

International audience; Polymer blend made from poly( - caprolactone)/chitosan (PCL/CHT) offers interesting opportunities for biological applications. The paper presents a new way to fabricate PCL/CHT double-porosity (macrovoids with interconnected microporosity) membrane materials from a chemical optimization of the solvent and non-solvent phases and from a modified phase inversion technique. By varying the PCL/CHT proportion, it is shown that it is possible to improve the chemical and physical properties of the CHT carbohydrate polymer. The PCL/CHT membranes are fully characterized in term of physico-chemical properties (ATR-FTIR, XRD and DSC) to understand the miscibility of the two-polymer blend. Morphological characterization by SEM shows that by increasing CHT wt% in the blend, the size of the macrovoids was increasing. Rapid enzymatic degradation of PCL from all the blend was found by using lipase (from P. cepacia). The mechanisms at the origin of the morphological structuration of the material is also discussed. To test the ability to operate these materials as small diameter vascular scaffolds, cell culture with human umbilical vein endothelial cells (HUVECs) were carried out on the membrane and the results analyzed with laser scanning confocal microscopy (LSCM). Data suggest that the blend membrane with higher concentration of CHT polymer wt% have suitable properties that promote high number of cells on the surface by maintaining cellular cytoskeleton integrity within 3 days. The blend membrane with a double porous morphology could be potentially applicable in future for small diameter vascular graft application. The surface macrovoids (20–90 μm) could be useful for three-dimensional cellular adhesion and proliferation and interconnected microporous spongy network (7–20 μm) is expected to transfer essential nutrients, oxygen, growth factor between the macrovoids and the supernatant.

International audience; Membranes consisting of a semi-interpenetrating network of polysulfone (PSU) and cross-linked polyacrylate were synthesized via non-solvent induced phase inversion followed by UV-treatment. Tetrahydrofuran (THF) or 1,4-dioxane (DIO) was added as co-solvent to the N,N-dimethylformamide (DMF)-based polymer solutions and cast films were subjected to evaporation prior to coagulation. Effects of synthesis variables on the membrane morphology and solvent resistant nanofiltration (SRNF) performance were investigated by using a Rose Bengal solution in isopropanol. By increasing the evaporation time from 0 to 100 s for the membranes prepared with THF and DIO as co-solvent respectively, rejections increased from 65.3% to 94.2% and 60.1–89.1%, while permeances decreased from 0.29 to 0.01 l/m2 h bar and 0.41–0.08 l/m2 h bar. A similar effect was observed when the co-solvent/solvent ratio was increased from 0/100 to 100/0: rejections increased from 63.1% to 94.9% and 59.2–90.6%, while permeances decreased from 0.43 to 0.01 l/m2 h bar for THF-based membranes and to 0.07 l/m2 h bar for DIO-based membranes respectively. A post-treatment was performed to increase the flux by immersing UV-cured PSU-based films in DMF for 48 h. The resultant membranes showed higher permeances and lower rejections, making them especially useful as potential candidates for stable supports to apply selective layers upon, such as e.g. in thin film composite (TFC) membranes. As observed in scanning electron microscopy, higher evaporation times and lower initial co-solvent concentrations resulted in less or even no macrovoids.

A polymeric catalytic membrane was previously prepared that showed remarkable efficiency for Suzuki-Miyaura C-C cross-coupling in a flow-through configuration. A mathematic model was developed and fitted to the experimental data to understand the significant apparent reaction rate increase exhibited by the catalytic membrane reactor compared to the catalytic system under batch reaction conditions. It appears that the high palladium nanoparticles concentration inside the membrane is mainly responsible for the high apparent reaction rate achieved. In addition, the best performance of the catalytic membrane could be achieved only in the forced flow-through configuration, that, conditions permitting to the reactants be brought to the catalytic membrane by convection. © 2016 American Institute of Chemical Engineers AIChE J, 63: 698–704, 2017

Among the available membranes, dense polymer composite hollow-fiber membranes are promising for gas permeation applications coupled with the use of gas/liquid contactors, but they are also used in other membrane processes such as pervaporation. This study focuses on a coating process, starting from a polymer solution, to control the thickness and regularity of the coated polymer. The thickness of the liquid film coated onto a fiber is related to the coating velocity, the physical and chemical properties of the liquid, and the coating geometry. Depending on the dominating forces, several regimes are defined: two unstable regimes, in which a thin and regular polymer layer cannot be produced, and two stable regimes, which are of interest for reaching our objectives at the laboratory or industrial scale. The theoretical laws were compared to experimental coatings with solutions of poly(trimethylsilyl)propyne (PTMSP) dissolved in cyclohexane coated onto poly(ether sulfone) (PES) hollow fibers. The viscosities, surface tensions, and densities of the solutions used were measured. The experimental thicknesses of coated polymer layers were compared to values calculated from Landau’s law, which describes the thickness behavior in the viscocapillary regime. The results showed good behavior agreement, but the experimental thickness was underestimated by the calculations. Four different kinds of composite membranes were prepared using two different porous supports (MicroPES and Oxyphan) and two different permeable polymers (PTMSP and Teflon AF2400) for coating. The obtained composites hollow fibers were characterized. All four presented low-energy surfaces with no wetting phenomena. They also exhibited high CO2 and N2 permeabilities with CO2/N2 selectivities between 3.4 and 2.5. The mechanical properties of the composites remained stable except for composites based on PES affected by the drying step during the coating process.

International audience; We present experimental results of mass transfer of a non reactive tracer gas (neon)measured in aerobic heterotrophic biofilm developed from activated sludge. Biofilms are grown in various hydrodynamic conditions and the effective diffusivity is used to quantify the mass transfer through the biofilm. Beyond some cross-flow conditions, the effective diffusivity through the biofilm seems larger than in the bulk. This can be explained by a dispersion generated by convection inside the biofilm, as supported by an analytical flow model and in accordance to the numerical simulation proposed by Aspa et al. (2011).

Poly(vinylidene fluoride) (PVDF) hollow fiber membranes were obtained by the phase inversion technique. The influence of internal coagulant viscosity (0.001 to 3 Pa s) and air gap (0.6 to 86.4 cm) on the structure and mechanical resistance of the fibers was studied. A “sponge-like” structure free of macrovoids was obtained by using polyvinyl alcohol (PVA) with N-methyl pyrrolidinone and water as internal coagulant (viscosity 3 Pa s). The effect of the air-gap was studied in order to control the structure and obtain mechanically resistant membranes with tensile strength at break between 2.2 and 54.3 N/mm2 and pure water permeability ranging from 4 to 199 Lh−1m−2bar−1. CO2 permeability of these membranes was measured and found to be in the range of 365 to 53200 NLh−1m−2bar−1. The “Dusty Gas” model (DGM) was used to calculate the pore size of the membranes from CO2 permeability experiments, obtaining pore radius values going from 0.6 to 10.8 µm. Results from modeling were compared with pore sizes observed in...

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International audience; Membrane contactors based on microporous hydrophobic materials already offer remarkable performances for different separation applications at industrial scale, especially for gas-liquid mass transfer operations. Impressive process intensification effects can indeed be achieved in certain cases, due to the large interfacial area provided by hollow fiber membranes. Nevertheless, depending on the membrane and fluid properties, great differences in mass transfer can be obtained; undesirable effects due to liquid contact such as gradual changes in membrane structure and/or partial wetting of the pores can dramatically affect mass transfer performances. Numerous studies have addressed these difficulties for one of the most attracting and challenging application of membrane contactors: the absorption of CO2 in a chemical solvent in order to achieve post-combustion CO2 capture from flue gases. For this application, given the fast chemical reaction which takes place in the liquid phase, a highly permeable membrane material is absolutely necessary. Additionally, the membrane material has to withstand long term contact with a chemically reactive solvent (typically an amine such as monoethanolamine: MEA) and has to remain non wetted. A possible solution which prevents wetting problems together with a minimal impact on the membrane mass transfer coefficient is reported in this study; the key idea is to make use of a composite membrane based on a thin dense skin, based on a highly permeable glassy polymer, coated on a microporous support. In a first step, screening tests have been performed in order to identify potential polymer candidates for the thin skin, combining a high CO2 permeability and solvent (MEA) compatibility on long time scales. In a second step, composite hollow fibers with a thin skin (Teflon AF®, PTMSP) coated on a porous support (PP) have been prepared and tested. The concept has been finally tested and validated at lab scale for CO2 capture from a gas mixture into aqueous solutions of MEA with hollow fiber modules. Remarkably, the overall mass transfer performances of the composite fibers compete with the most permeable microporous membranes classically proposed for membrane contactor applications. The possible use of these novel composite fibers for other applications and the extension of the concept to different industrial situations are discussed.

Conductive microporous membranes were fabricated by the phase inversion technique from pristine multiwalled carbon nanotubes (MWCNT)–polysulfone mixtures. A sonication-assisted method was used to disperse MWCNT in the polysulfone matrix without a covalent modification of the MWCNT or the use of surfactants. Electron Microscopy (SEM) and conduction tests were used to characterize the membranes. SEM pictures indicated that a concentration of 3% of MWCNT allowed a good dispersion of the nanotubes inside the hydrophobic polysulfone matrix. Current–voltage tests showed efficient electron percolation pathways across the membrane as a result of the successful dispersion of pristine MWCNT. These membranes will be applied in separation of charged species where microfiltration together with application of electric fields is needed.

International audience; The absorption of CO2 from a CO2/N2 mixture is investigated using a membrane gas absorption process. In order to avoid any wetting problem and maintain optimal the removal efficiency, composite membranes, with a porous support coated by a dense layer, are used. Two composite membranes are studied: Oxyplus® and a polypropylene (PP) porous fiber coated by poly(1trimethylsilyl-1-propyne) (PTMSP). The influence of some parameters on the CO2 removal efficiency is explored. A lower removal efficiencies is obtained with a PP-PTMSP fiber compared with Oxyplus® because of a PTMSP layer thickness four times larger than the dense layer of Oxyplus® fibers. Indeed, this dense layer is the key parameter which controls the membrane resistance. Experiments achieved validate the resistance of the membrane to the wettability. Increasing the liquid flow raises the removal efficiency of at least 5%. This one is higher than 90%. In the Oxyplus® module case, similar removal efficiencies are obtained, around 99%, with the blend of methyldiethanolamine and triethylene tetramine (MDEA +TETA) and with monoethanolamine (MEA) for gas velocities lower than 0.84 mdot operators−1. A 363 K regeneration temperature of liquid phase and 2 bar is sufficient to maintain a 90% CO2 removal efficiency.

Hollow-fiber membranes, made of polysulfone and originally having ultrafiltration properties, were modified in their outer surface layer by UV photografting. The monomer that was grafted onto the membrane surface was diallyl dimethyl ammonium chloride (DADMAC): it makes the surface hydrophilic, closes membrane pores and adds positively charged sites to the surface. The different UV doses were obtained by changing the light intensity. The membrane permeability was reduced with respect to the untreated membrane and high retentions of the calcium ion were obtained even though the MWCO remained high. The retention of ions is controlled by the electrostatic repulsion betweens the ions and the membrane charges. Increasing the UV dose at a constant line speed reduces membrane permeability and increases selectivity. This is the first step towards production of hollow-fiber membranes for nanofiltration.

Metal nanoparticles (MNPs) have unique physico-chemical properties advantageous for catalytic applications which differ from bulk material. However, the main drawback of MNPs is their insufficient stability due to a high trend for aggregation. To cope with this inconvenience, the stabilization of MNPs in polymeric matrices has been tested. This procedure is a promising strategy to maintain catalytic properties. The aim of this work is the synthesis of polymer-stabilized MNPs inside functionalized polymeric membranes in order to build catalytic membrane reactors. First, the polymeric support must have functional groups capable to retain nanoparticle precursors (i.e. sulfonic), then, nanoparticles can grow inside the polymeric matrix by chemical reduction of metal ions. Two different strategies have been used in this work. Firstly, polyethersulfone microfiltration hollow fibers have been modified by applying polyelectrolyte multilayers. Secondly, polysulfone ultrafiltration membranes were modified by UV-photografting using sodium p-styrene sulfonate as a vinyl monomer. The catalytic performance of developed hollow fibers has been evaluated by using the reduction of nitrophenol to aminophenol by sodium borohydride. Hollow fiber modules with Pd MNPs have been tested in dead-end and cross-flow filtration. Complete nitrophenol degradation is possible depending on operation parameters such as applied pressure and permeate flux.

International audience; The elaboration of a polymeric catalytic membrane containing palladium nanoparticles is presented. The membrane was prepared using a photo-grafting process with imidazolium-based ionic liquid monomers as modifying agent and microPES® as support membrane. Ionic liquid serves as a stabilizer and immobilizer for the catalytic species, i.e. palladium nanoparticles. The Suzuki–Miyaura cross-coupling reaction was carried out on the catalytic membrane in flow-through configuration. Complete conversion was achieved in 10 s through one single filtration, without formation of byproducts. The apparent reaction rate constant was three orders of magnitude greater than in a batch reactor. No catalyst leaching was detected. This membrane offers the possibility of continuous production with no need for a separation step of the catalyst from the reaction medium.

International audience; The aim of this work is the synthesis of polymer-stabilized Pd nanoparticles (PdNP) inside a functionalized polymeric porous membrane in order to develop hybrid catalytic membrane reactors and to test them in model metal-catalyzed organic reactions. For this goal, a polymeric membrane support (Polyethersulfone hollow fibershaped) was firstly functionalized with an ionogenic polymer (i.e. poly(styrenesulfonate) capable to retain PdNP precursors using an UV photo-grafting method. PdNP were then generated inside the polymeric matrix by chemical reduction of precursor salts (intermatrix synthesis). The catalytic performance of the PdNP catalytic membranes was evaluated using reduction of nitrophenol by sodium borohydride (NaBH4)in water.

International audience; The objective of the present work is to correlate the evolution of membrane characteristics due to contact with hypochlorite used as cleaning agent to its selectivity towards model solutes. Accelerated ageing experiments were performed by soaking the membrane at ambient temperature in hypochlorite solutions. The total free chlorine concentration of these solutions was fixed at 350 ppm and the pH at 8. The model solute selected was T500 Dextran. The experimental results demonstrated that hypochlorite induced membrane degradation, on one hand modified the solutes–membrane interactions increasing irreversible fouling and, on the other hand, lowered the selectivity. These results have been correlated with the modification of the pore size distribution following a protocol in which fouling did not affect membrane characterization. The most probable scenario of distribution evolution over degradation process was an increase of the pore radius of the initial population, accompanied by a decrease in their number, coupled with the appearance of defects, whose radius increased with the progress of the degradation.

International audience; The main objective of this study is to develop a new formula for a diet mayonnaise-like sauce without cholesterol. Emulsifying power is provided by the use of soy lecithin and the total fat content was limited to 16%. Droplet size measurement of employed mayonnaise samples at different times show that the largest diameter of fat does not exceed 18.5 µm with a yield stress of 56.1 Pa. Results of stability to centrifugation reveal that the absence of the supernatant oily layer ensures the stability of the emulsion. Using the experimental design method, the number of trials can be limited to a number of 16 experiments, and best formulation of the mayonnaise (without cholesterol) was obtained.

New nanofiltration membranes have been developed by UV-photografting. Sodium p -styrene sulfonate (NaSS) and [2-(acryloyloxy)ethyl]trimethyl ammonium chloride (AC) were used for the modification of a polysulfone ultrafiltration membrane. The membrane cut-off was estimated. The grafted membranes were evaluated for the removal of six different dyes according to their charge in the aim of reusing the water in the process house. The effects of various parameters such as dye class, pressure, pH and the presence of salt were evaluated. It was observed that the newly developed membranes showed acceptable performance both in terms of flux and rejection. Dye retention was higher than 96% and hydraulic permeability was 0.48–0.56 m 3 m −2 day −1 at 0.4 MPa. The influence of pH and salt on the performance of membranes in terms of fouling and retention was established and compared to a commercial membrane (Desal 5 DK).

A new way to prepare nanofiltration membranes, consisting of in-line external modification of the skin of a polysulfone ultrafiltration hollow fibre skin, is described. The paper presents a continuous process (dip-coating followed by photografting) and the influence of the operating conditions on the membrane characteristics. This study is focused on a simplified model based on the evaluation of the two sources of monomer available for grafting: one is monomer contained in the thin film drawn from the dip bath, second is contained in the pores of the membrane. The results show that two extreme types of modification can be produced, depending on the experimental conditions: a high rate coupled with a short dip contact time leads essentially to an external grafting whereas a low rate coupled with a long dip residence time leads essentially to an “in pore” grafting.

Recent progress in membrane technology, combined with increasing concern about environment protection, led industrialists and researchers to the development of advanced treatments for domestic wastewater. Membrane bioreactor technology seems to be promising. This study is performed in the context of a regional program for design and optimization of membrane bioreactors for domestic water reuse. We focused on the management of membrane fouling by alternative period of filtration, backflushing, or static state. Moreover, we show how the membrane initial permeability is important in such systems. The experiments were performed on sludge.

A nanofiltration membrane has been developed by UV-photografting. Sodium p-styrene sulfonate was used for the modification of a polysulfone ultrafiltration membrane. The membrane cut-off was estimated. The grafted membranes have been evaluated for the removal of five different dyes with an aim to reuse water in the process house. The effect of different parameters such as dye class, pH and the presence of salt was evaluated. It is observed that the newly developed membranes show acceptable performance both in terms of flux and rejection. Dye retention was higher than 97% and hydraulic permeability 0.23–0.28 m3.m−2.d−1 at 0.4 MPa. The influence of pH on the performance of membranes in terms of fouling and retention was established and compared to a commercial membrane (Desal 5DK).

Experiments were run with seven dyes and a Desal 5DK membrane (cut-off, 150–300 g/mole). The effects of concentration, pH and salt on flux and retention were studied. The cut-off of the membrane explains that the retention of the relative high molecular weight dyes (as direct red 80 or direct yellow 8) is always almost 100%. For anionic dyes as acid orange 10 or acid red 4, the amphoteric nature of polyamide explains the lower retention at pH 3 than 6. This effect is more pronounced and reversed for basic blue 3, a cationic dye. The membrane is sensitive to fouling since most of the dyes are used for polyamide textile dying. Moreover, the presence of salt leads to a further decrease in flux.

International audience; This paper reports innovative coupling for the development of catalytic membrane reactors. Photografting for the modification of membrane surfaces has been extensively studied and we used the results to optimize metal nanoparticle loading. Polyethersulfone hollow fibers were modified by poly(acrylic acid) grafting and the impact of a cross-linked network and a polymer gel grafted layer on metal loading was examined. Transmission electron microscopy images showed well dispersed metal nanoparticles close to the surface. The catalytic activity of the different hollow fibers was assessed by the reduction of p-nitrophenol into p-aminophenol and a conversion yield of close to 100% was found. We demonstrated the possibility of obtaining various reactors by varying the residence time through alteration of the grafted layer.

International audience; Due to its low regeneration energy demands relative to MEA, ammonia is one of the most attractive solvents for post-combustion CO2 capture processes. Nevertheless, additionally to a lower kinetic constant, a high ammonia slip takes place when the absorption process is performed in a packed column. In this study, the feasibility of an ammonia based CO2 capture process using hollow fiber membrane contactors is investigated. CO2 absorption experiments in ammonia have been performed with porous polypropylene membranes (Oxyphan) and with two different dense skin composite hollow fibers: tailor made (Teflon AF2400) and commercial (TPX). It is shown that microporous membranes do not offer stable performances, due to salt precipitation and pore blocking. Contrarily however, dense skin membranes show stable and attracting performances, whatever the operating conditions: reduced ammonia slip and intensified CO2 mass transfer are obtained compared to packed column. The potentialities of dense skin membrane contactors, particularly based on fluorinated polymers, are discussed with regard to both increased CO2 mass transfer performances and mitigation of ammonia volatilization compared to conventional gas/liquid contactors.

A novel route to the preparation of nanofiltration membranes has been proposed. The method consists of the photografting of polymer on to the surface of porous membranes. The method was tested with polysulfone ultrafiltration membranes and poly(acrylic acid) in water solution. It has been shown that the surface modification is stabilised by crosslinking with N, N′-methylene bis acrylamide and that the grafting does not require any photoinitiator and any purification of the reactants. Moreover, by the proper choice of the wavelengths, the UV irradiation does not induce any significant copolymerisation of the reactants inside the aqueous solution. The irradiation conditions, the monomer concentration and the permeability of the support membrane were examined. The water softening properties of the novel membranes were measured in dead-end mode and at a 95% recovery. A large range of performances has been obtained which demonstrates the feasibility of the UV irradiation as an environmentally friendly and versatile (flexible) technology to prepare nanofiltration membranes.

This article presents a method which allows one to find the Hansen solubility parameters by means of data processing. In the first part, we present the thermodynamical principle of Hansen parameters, and then we explain the model used to find parameters from experimental data. We validate the method by studying the solubility parameters of CFC-12 (dichlorodifluoromethane), HFC-134a (1,1,1,2-tetrafluoroethane), neopentylglycol esters, trimethylolpropane esters, dipentaerythritol esters, and pentaerythritol esters. Then, the variation of Hansen parameters are studied as well as the relation between the miscibility temperature (the temperature at which a blend passes from the miscible state to the immiscible state) and the interaction distance. We establish the critical interaction distance of HFC-134a which determines the solubility limit and we study its variation with temperature.

A study of polyolester oils (POE) for compressors using an ozone-friendly refrigerant is presented here. The effect of the chemical structure of POE was studied in relation to three lubricant properties: miscibility with HFC-134a (CF3-CH2F), lubricity (steel-on-steel and aluminium-on-steel contacts), and viscosity. The paper shows the strong structure effect of POE on miscibility and lubricity. Based on the data obtained, some model lubricants were blended, and the performance of these lubricants was assessed on refrigeration test rigs.

The stability of four components emulsions - oil, water, surfactant and cosurfactant - is examined. From a series of stable formulations, prepared with one surfactant family, the correlations between different characteristic parameters - solubility parameters of the oil and of the cosurfactant, surfactant HLB, required HLB of the oil - are checked. The experimental study displays linear relations between some of these parameters. The results allow to predict that the choice of the oil induces the choice of an HLB range for the surfactant and a solubility parameter range for the cosurfactant.

International audience; The presence of pores larger than a micron, known as macrovoids, in polymeric membranes is particular lydetrimental for membrane structural integrity and mechanical properties. The theoretical modelling and physical understanding of the mechanisms of initiation and growth of the macrovoids, notably in order to determine processing conditions that would allow to make macrovoids free membranes, have been the subject of a vast literature and a restill controversial. However, experimental data on macrovoids, that could help to discriminate between several ideas are scarce and have been essentially obtained using 2D imaging systems. A very large number of observations are then needed to obtain statistically significant results and the limitation to 2D images does not permitto access to an accurate description of the macroporous structure. In this work, anX-raytomography system was used to image the 3D porous structure of hollow fibre membranes with a spatial resolution of one micron. Image analysis tools have been developed to accurately characterise them acrovoid shapes and spatial distribution on the membrane outer and inner skins as a function of some of the spinning process conditions (concentration of solvent into the bore and airgap length). The main purpose is there fore to quantify effects of some processing conditions on the macroporous structure of a hollow fibre membrane. Also, such an accurate characterisation of the macrovoids spatial distribution and 3D shape, as well as their variations with the process experimental conditions, help to shed light on macrovoids initiation and growth mechanisms.

International audience; Polysulfone (PSU) was chemically modified to prepare new molecular imprinted membranes (MIMs). Several amounts of amine and sulfonyl groups were introduced into the PSU chemical structure in order to create interactions with acid or base templates, such as biomolecules or biomacromolecules. A fluorescent dye, Acridine Orange base (AO), was used as a model template and its complexation with the prepared PSUs was monitored by spectroscopic techniques. This study showed an absence of complexation with the native PSU and a strong complexation with the aminated and the sulfonated PSUs. Partially allylated PSU bearing amine or sulfonyl groups were also synthesized. These compounds are expected to be used as precursors for designing new crosslinked molecular imprinting membranes (MIMs), exhibiting high stability of the template memory.

In the membrane-based bioartificial livers developed up to now, the hepatic cells were located either in the fibers′ lumen or in the cartridge, with limited capacity for cell hosting. Here, we designed a polysulfone (PSU) membrane with a double porosity level: (i) surface macroporosity emerging in macrochambers accessible to hepatic cell colonization; (ii) microporosity to ensure gas and molecule transfers between macrochambers and supernatant, as well as potential immune barrier. ESEM and X-ray tomography confirmed that macrochambers accessed the membrane surface and were interconnected. Biocompatibility and performances of this PSU membrane with double porosity level were compared to classical semi-permeable structures, following cell organization, cell proliferation and liver specific activities over a 9 days incubation. Macrochambers were colonized by hepatic cells, leading to higher albumin synthesis compared to control. Therefore, this membrane with double porosity appeared as a promising support to offer an inner 3D environment adequate to cell proliferation to form a liver-like tissue.

International audience; Ultrafiltration membranes were prepared using cellulose acetate (CA) as a polymer, LiCl and CaCl2 as porogens and methyl-(S)-lactate as a solvent. CA, methyl lactate and the porogens used in this work are obtained from renewable resources; they are biodegradable, non-toxic and non-volatile organic compounds. Flat sheet ultrafiltration membranes were prepared by the phase inversion technique. A molecular weight cut-off between 15 and 35 kDa (polyethylene glycol) and pure water permeability between 13 and 177 litres h21m22 bar21 were obtained. These parameters are in the ideal range for water treatment industry. Improvement of pollutant degree and ecotoxicity of the process was evaluated by ‘green’ metrics by the P (pollutants, persistent and bioaccumulative) and E (ecotoxicity) parameters. Both of these variables were recorded as zero using our method. This study represents a step ahead towards the production of ultrafiltration polymeric membranes by a‘greener’ process than current methods.

International audience; Most commercial polymeric membranes are prepared by phase inversion. The performance of the membranes depends greatly on the morphology of the porous structure formed during the different steps of this process. Researchers in this field have found it extremely difficult to foresee how a change in the composition of the polymer solution will affect pore formation without a set of methods designed to yield detailed knowledge of the morphological structure. This paper reports the new potential associated with X-Ray synchrotron microtomography to characterize the 3D structure of a PvDF hollow fibre microfiltration membrane prepared by phase inversion. 3D morphological data obtained from the ID19 line at the ESRF are presented. The membrane actually appears as a complex three-dimensional bi-continuum of interconnected pores. Within the hollow fibre structure, different regions with various thicknesses and pore size distributions have been identified and well characterized. Transversal views show the anisotropic finger-like structure of pores, while longitudinal sections reveal a honeycomb structure which resembles the structure of highly concentrated water in oil emulsion or dispersion. This typical structure might be obtained during the phase inversion process. How the phase inversion process may result in these morphologies is finally discussed.