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This contribution is a comparison study between synthetic hydroxyapatite (Sy-HAP) and commercial hydroxyapatite (C-HAP) for the removal of Pb2+ and Cd2+ ions present in wastewater from industrial effluents. The obtained results show that the equilibrium time required for complete adsorption of Pb2+ and Cd2+ ions on C-HAP and Sy-HAP is 15 min for both. The obtained removal efficiencies for Sy-HAP are 95.52% and 90.91% for Pb2+ and Cd2+ ions, respectively. Whereas, C-Hap presents lower removal efficiencies of 86.53% and 81.43% for Pb2+ and Cd2+ ions, respectively. Maximum adsorption was observed at pH 5; at lower pH levels adsorption was less. The experimental kinetic data fitted with the second order kinetic model. Thermodynamically, the adsorption process was endothermic and spontaneous in nature. Isotherm adsorption studies indicated that Langmuir, Freundlich and Temkin are the most valid models to describe and evaluate the adsorption process. The EDX results also confirmed the presence of lead and cadmium in adsorbents after adsorption. Finally, the HAP porous materials possess great potential for the removal of Pb2+ and Cd2+ ions from aqueous solutions and wastewater from industrial effluents.

A novel chitosan/kaolin composite membrane with high flux and enhanced hydrophilicity was prepared by solvent casting and evaporation process in the presence of polyethylene glycol (PEG). The characterization of the as-fabricated membranes indicated that the combined effect of kaolin as reinforcing agent and PEG as porogen into a chitosan matrix showed significant influence on the morphology and hydrophilicity. Highly porous membranes with finger-like structure were obtained. Both size and density of the pores increased with increasing the PEG content from 0 to 3 wt%. The incorporation of the hydrophilic polymeric additive constructed a water channel network and increased the free volume within the composite matrix, contributing to the enhanced filtration performance of the resulting membrane. Additionally, their mechanical, thermal and chemical stability showed a large improvement compared to the unmodified one.

International audience; This work is aimed at developing a new process to separate alpha-cyclodextrin (CD) from binary alpha-CD/beta-CD mixtures. To achieve this objective, a membrane process was designed with water as solvent and using the selective accommodation of a guest Igepal Co-890 (IG) within the beta-CD cavity. In the first part, host-guest inclusion study suggested the formation of IG(2)/beta-CD complex in presence of IG excess. Moreover, increasing IG/CD molar ratio to 1.5 leads to the complete complexation of beta-CD while alpha-CD remains free. The second part was devoted to the separation of alpha- and beta-CD using UF membranes (GH and GK from GE-Osmonics). The influence of parameters including membrane molecular weight cut-off (MWCO), transmembrane pressure (Delta P), IG/beta-CD and alpha-CD/beta-CD molar ratios, was investigated. MWCO, Delta P, IG/beta-CD and alpha-CD/beta-CD molar ratios respectively of 1000 Da, 2 bar, 1.5 and 11:89 are the optimized values to reach an alpha-CD separation factor as high as 38. The experimental data fits very well with predicted values calculated using the parameters found in the complexation study and rejection of single solutions indicating that selectivity predominantly originates from steric exclusion of species by membrane GH.

International audience; Poly(ether imide) (PEI) membrane with enhanced antifouling property was successfully prepared in a mild and simple procedure. The virgin membrane was firstly functionalized with an aqueous solution of diamino-terminated poly(ethylene oxide) block copolymer (PEG-diamine). Glutaraldehyde was used in a second step as a linker to chemically attach additional PEG-diamine to the primary amine groups grafted on PEI membrane surface. Immobilization of PEG segments was confirmed using Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and atomic force microscopy. Ultrafiltration experiments revealed that the enhancement of a PEG coverage on the membrane surface provided superior anti-protein-fouling property. Cycles of protein filtration also demonstrated that the antifouling surface was stable over time and excellent ultrafiltration performance could be maintained without the need of harsh cleansing operation.

Sweeping gas membrane distillation (SGMD) is a useful option for dehydration of aqueous solvent solutions. This study investigated the technical viability and competitiveness of the use of SGMD to concentrate aqueous solutions of 1,3-dimethyl-2-imidazolidinone (DMI), a dipolar aprotic solvent. The concentration from 30% to 50% of aqueous DMI solutions was attained in a bench installation with Liqui-Cel SuperPhobic&reg, hollow-fiber membranes. The selected membranes resulted in low vapor flux (below 0.15 kg/h&middot, m2) but were also effective for minimization of DMI losses through the membranes, since these losses were maintained below 1% of the evaporated water flux. This fact implied that more than 99.2% of the DMI fed to the system was recovered in the produced concentrated solution. The influence of temperature and flowrate of the feed and sweep gas streams was analyzed to develop simple empirical models that represented the vapor permeation and DMI losses through the hollow-fiber membranes. The proposed models were successfully applied to the scaling-up of the process with a preliminary multi-objective optimization of the process based on the simultaneous minimization of the total membrane area, the heat requirement and the air consumption. Maximal feed temperature and air flowrate (and the corresponding high operation costs) were optimal conditions, but the excessive membrane area required implied an uncompetitive alternative for direct industrial application.

International audience; AB(2)-type amphiphilic (HPMC)(2)-PLA copolymers with various hydrophilic block lengths were synthesized using a three step procedure: ring-opening polymerization of L-lactide initiated by propynol, amination reduction of the aldehyde endgroup of HPMC, and thiol-click reaction. The resulted copolymers were characterized by NMR, DOSY-NMR, SEC and FT-IR. The cloud point (CP) was determined by UV-vis spectrometer. Data show that the HPMC block length has little effect on the Cp of the copolymers which is lower than that of HPMC. The self-assembly behavior of the copolymers was investigated from DLS, TEM, and critical micelle concentration (CMC) measurements. Spherical micelles are obtained by self-assembly of copolymers in aqueous solution. The micelle size and the CMC of copolymers increase with increasing HPMC block length. It is concluded that biobased and biodegradable (HPMC) 2-PLA copolymers could be promising as nano-carrier of hydrophobic drugs.

Amphiphilic diblock copolymer containing randomly distributed positive and negative charged monomers are synthesized using RAFT polymerization technique to be used as anti-bioadhesion coatings for hydrophobic surfaces. Quaternized 2-(dimethylamino) ethyl methacrylate and potassium 3-sulfopropyl methacrylate (P[qDMAEMA-co-KSPMA]) are randomly polymerized to yield an anti-bioadhesion block which is, in one pot, copolymerized with styrene as an anchoring block. This copolymer has demonstrated high anti-bioadhesion properties to avoid the blood clotting in medical devices through a simple and facile approach to preparation of pseudozwitterionic copolymers.

International audience; Control of film structures made from a polystyrene-polystyrene sodium sulfonate-polystyrene (PS-PNaSS-PS) copolymer micellar solution is investigated in a THF/water mixture. Four different copolymers (varying molecular weights) are synthesised via RAFT (Reversible Addition Fragmentation chain Transfer) polymerisation. Depending on parameters such as copolymer molecular weight, solvent composition and copolymer concentration, the PS-PNaSS-PS triblock self-assembles into different morphologies in solution and dry state. The effect of each parameter is investigated using characterization techniques such as AFM, TEM, Cryo-TEM, SEM and SAXS. The morphologies obtained for PS-PNaSS-PS are found to be extremely sensitive when the water content of the micellar solution is low. Among the structures observed, a highly ordered nano-porous film is obtained using a PS10k-PNaSS6k-PS10k triblock copolymer solution containing 3.0 wt% of water. This micellar solution is used to prepare a porous membrane for filtration applications. Pure water filtration data suggest a pore size in the range of ultrafiltration, making these membranes attractive for applications in the food industry, for bacteria, virus and protein removal.

An ABA triblock amphiphilic copolymer is synthesized using RAFT chemistry. The self-assembled micelles of this copolymer are then used to prepare nano-organized porous films that could be used as filtration membranes. In this work a novel strategy is developed to build the nanostructures and perform their self-assembly using reversible and non-covalent interactions to create free volume between the micelles, thus giving tuneable porosity to the film. The self-assembly of poly(styrene)-b-poly(phenylboronic acid)-b-poly(styrene) block copolymer, occurs at high concentration through solvent evaporation, which induces a progressive decrease of the inter-micellar distance, and results in the formation of an in situ network of micelles and the final porous film. Subsequent permeability tests were conducted under different stimuli (pH and UV), generating cross-linking and chemical exchange reactions, to ensure the best balance between permeability and mechanical strength. This work highlights an original strategy for pore size control, and provides new insights towards the design of stimuli-responsive materials.

Low molar mass (LMM) biopolymers are highly required to design functional nanomaterials, which mainly find application in biomedical fields. However, the synthesis of LMM polymer is a challenging task. In this work, we report a partial enzymatic depolymerization process which allows to produce a series of LMM hydroxypropylmethyl cellulose (HPMC) polymer, with a weight average molar mass (M w) under and over 10,000 g mol −1 and low dispersity (Ɖ < 1.5). Variation of the starting HPMC grade, reaction time, and enzyme concentration were the key parameters to control the M w and yield of the target molecules. This approach provides a versatile way of producing LMM HPMCs with varying degrees of substitution, and having a single reactive aldehyde function at one chain extremity. LMM HPMC can find for instance application as building blocks for the development of new functional molecular architectures.

An accurate control of the pore size has been demonstrated with poly(ether imide) (PEI) membranes by using a chemical post-treatment with amino oligomers. Jeffamine M-2070, a mono aminated poly(propylene oxide)- co -poly(ethylene oxide) copolymer (PEG-amine, 2 kDa), and poly(ethyleneimine) (Pei), with molecular weight ranging from 0.8 to 2 kDa, were used as molecular weight cut-off ( MWCO ) modifying agents. PEI membranes having a MWCO of 120±10 kDa (measured by PEG/PEO rejection) and a pure water permeability of 180±30 l h −1 m −2 bar were prepared from a 16 wt% PEI solution in NMP by coagulation into a water bath. Modification with the mono-functionalized PEG-amine leads to a pore opening owing to the dissolution of the overreacted PEI chains. PEGylated UF membranes with increasing MWCO up to 500 kDa were thus prepared by varying the reaction time. Beyond this value, the mechanical strength of self-standing membranes decreased. In contrast, use of a poly-amino reagent prevented the dissolution by the cross-linking of PEI chains. Positively charged membranes with decreasing MWCO down to the NF range were prepared by using Pei oligomers. A plateau was reached after ca 3 h of reaction. Longer reaction times only gave rise to a decline of the permeate rate due to an increase of the dense top layer thickness. A mechanism involving a dynamic rearrangement of the PEI chains was proposed to account for the experimental observations.

The aim of this work is to develop a two-step membrane separation process enabling the fractionation of protein hydrolysates obtained from enzymatic hydrolysis of tuna by-products. A screening of the more appropriate UF and NF membranes was first performed in dead-end and tangential filtration cells with a model solution prepared from a commercial fish hydrolysate (Prolastin®). Optimization of UF and NF steps was then investigated through the impact of operating parameters including pressure, peptide concentration and pH of the solution on performance of two selected membranes. Finally, the coupling of UF and NF steps was investigated for the fractionation of a raw hydrolysate prepared from tuna by-products. Three different operation modes coupling UF and NF steps in batch and diafiltration configurations were tested. A fraction rich in peptides of molar mass between 1 and 4 kg mol −1 was isolated and the positive effect of diafiltration on peptide purification process was underlined.

Cationic vectors are ideal candidates for gene delivery thanks to their capability to carry large gene inserts and their scalable production. However, their cationic density gives rise to high cytotoxicity. We present the proper designed core-shell polyplexes made of either poly(ethylene imine) (PEI) or poly(2-dimethylamino ethyl methacrylate) (PDMAEMA) as the core and zwitterionic poly(acrylic acid)-block-poly(sulfobetaine methacrylate) (PAA-b-PSBMA) diblock copolymer as the shell. Gel retardation and ethidium bromide displacement assays were used to determine the PEI/DNA or PDMAEMA/DNA complexation. At neutral pH, the copolymer serves as a protective shell of the complex. As PSBMA is a nonfouling block, the shell reduced the cytotoxicity and enhanced the hemocompatibility (lower hemolysis activity, longer plasma clotting time) of the gene carriers. PAA segments in the copolymer impart pH sensitivity by allowing deshielding of the core in acidic solution. Therefore, the transfection efficiency of polyplexes at pH 6.5 was better than at pH 7.0, from β-galactosidase assay, and for all PAA-b-PSBMA tested. These results were supported by more favorable physicochemical properties in acidic solution (zeta potential, particle size, and interactions between the polymer and DNA). Thus, the results of this study offer a potential route to the development of efficient and nontoxic pH-sensitive gene carriers.

Mixed matrix membranes (MMMs) provide an exciting alternative to traditional membranes due to their favorable properties from both building blocks which are essential for certain separation applications. Block copolymer directed synthesis of MMMs is an innovative approach for the preparation of porous materials. In the current work the syntheses of mixed matrix membranes from a PMAA-b-PMMA block copolymer and functionalized iron oxide magnetic nanoparticles are demonstrated. The block copolymers were synthesized using a RAFT polymerization technique, along with three different types of magnetic nanoparticles with various surface properties. The thin film membranes were prepared by mixing different ratios of diblock copolymer in THF and iron oxide nanoparticles in water followed by tape casting or spin coating. The particles and the membranes were characterized using TEM, DLS, and SEM. The permeation behavior of the membranes was assessed using filtration tests in the presence and absence of a magnetic field.

Nombreuses sont les personnes exposées à une concentration excessive de fluor dans l’eau qu'ils boivent. C’est le cas de la population vivant dans le sud algérien. L'excès de fluor provoque des affections invalidantes : la fluorose dentaire, la fluorose osseuse. L’objectif principal de ce travail est d’étudier l’effet de la pression et de la concentration des sels sur leur rétention par nanofiltration. Pour cela, nous avons déterminé les paramètres de performance de flux et de rétention vis-à-vis des solutés ioniques NaF, NaBr, NaCl et NaI par la membrane de nanofiltration NF 270. Cette présente étude examine aussi la défluoruration d’eaux saumâtres réelles du sud algérien. Des essais en nanofiltration ont montré que la rétention des anions se fait dans l’ordre suivant : F‑ > Cl‑ > Br‑ > I‑. La membrane NF 270 retient mieux les ions à une pression de 10 bar. Au-delà de cette dernière, la rétention des ions monovalents se stabilise aux différents pH étudiés puis diminue. À faible concentration (10‑3 M) la rétention limite des solutés étudiés est plus élevée qu’à plus forte concentration (10‑2 M). Il a été démontré que les ions fluorures peuvent être retenus sélectivement d’une eau naturelle saumâtre hyperfluorée à pH naturel à plus de 82 % en présence d'autres ions., Many people are exposed to excessive fluoride in their drinking water. This is the case of the population living in southern Algeria. Excess fluoride causes disabling conditions: dental and skeletal fluorosis. The main objective of this work is to study the effect of pressure and solute concentration of salts on their retention by nanofiltration. In a first step, we determined flow and retention performance parameters for the ionic solutes NaF, NaBr, NaCl and NaI using the nanofiltration membrane NF 270. Secondly, defluorination of natural brackish waters from southern Algeria was carried out. The nanofiltration tests show that the retention of anions following the order: F‑ > Cl‑ > Br‑ > I‑. The NF 270 membrane retains the ions better at a pressure of 10 bar. Beyond this value, the retention of ions leveled off at the different studied pH values and then decreased. At low concentrations (10‑3 M), the retention limit of the solutes studied was greater than that at a higher concentration (10‑2 M). It was finally shown that fluoride ions can be selectively retained from hyper-fluorinated natural brackish water (at a rate over 82%) in the presence of other ions.

International audience; Herein, a novel polymeric porous membrane was developed, without the use of any organic solvent in the initial dope solution and using a biobased polymer derived from cellulose: Hydroxypropylcellulose (HPC). HPC was dissolved in water (20 wt%) and the phase separation was induced by increasing the temperature above the Lower Critical Solution Temperature (LCST) of the polymer solution, around 40 °C in the concentration range concerned in this study. To fix the membrane morphology and to prevent any resolubilization in water during filtration tests, a chemical crosslinking was performed using Glutaraldehyde. The phase diagram of HPC/water system was first studied and not only the cloud point but also the spinodal curves were determined using optical transmission techniques. It was exhibited that HPC phase diagram is very weakly dependent on concentration up to large concentrations and that the metastable region is very small, i.e. the cloud point and the spinodal curves are very close in a large range of concentration. The membrane stability was tested in water and some organic solvents, thus demonstrating the efficiency of the chemical crosslinking during membrane formation. The swelling and mechanical properties of HPC membranes were also investigated depending on the operating condition during membrane formation, showing that the temperature ramp during the membrane formation, from initial to final temperature, have a significant effect on the crosslinking efficiency and hence on the swelling properties. Finally, adding a porogen (PEG200) into the collodion, filtration tests were performed and exhibited that the membrane filtration properties depend on the temperature ramp as well, showing higher water flux for the highest temperature ramp tested.

Mixed matrix membranes having combined properties of both polymeric and inorganic materials have become the principal focus on separation technology. This work insights an original strategy of mixed matrix membrane preparation incorporating positively charged inorganic nanoparticles (INPs) with negatively charged polymeric nanoparticles (PNPs) using spin coating technique. The PNPs with different morphologies (spheres, worms, and vesicles) made of poly(methacrylic acid)-b-(methyl methacrylate)) diblock copolymer were synthesized using RAFT dispersion polymerization in ethanol at 70 °C. The inorganic counterpart, iron oxide nanoparticles coated with poly(methacrylic acid)-b-poly(quaternized 2-(dimethylamino)ethyl methacrylate) were synthesized and incorporated into the membrane acting as a bridge between the negatively charged polymeric particles (due to the presence of opposite electrostatic charges). Permeability tests were carried out using the feed of different pH at various pressures.

A study has been undertaken of an advanced wastewater treatment approach using polymer nanofiltration membranes, in an attempt to obtain water of sufficient quality to allow it to be reused in the same production process or, alternatively, to be discharged without any problems. The study has initially focused on the removal of organic matter (reduction of COD) and the most representative ions present in the wastewater, such as Na+, Mg2+, Cl- y SO42-. In a first part of the study, with a view to optimising the experimental phase, a simulation has been performed of the nanofiltration process using the NanoFlux software. Among other things, the simulation allows the most suitable membranes to be selected as a function of the permeate flow rate and desired level of retention in the substances to be removed. The subsequent experimentation was carried out in a laboratory tangential filtration system that works with flat membranes. It was found that retention values of about 90% were obtained for the studied substances, with a good permeate flow rate, using low operating pressures. These results demonstrate the feasibility of the studied technology and its potential as a treatment for improving ceramic industry wastewater quality.Este estudio ha sido emprendido con el fin de acercar la nanofiltración a través de membranas poliméricas al tratamiento de las aguas residuales industriales de la industria cerámica, esperando obtener un agua con la suficiente calidad como para ser reutilizada en el propio proceso productivo o, alternativamente, poder verterla. El estudio se ha centrado en la eliminación de materia orgánica (reducción de D.Q.O) y algunos iones presentes en las aguas residuales, tales como Na+, Mg2+, Cl- y SO42-. En primer lugar, se ha realizado una simulación del proceso de nanofiltración usando el software NanoFlux. Entre otras cosas, la simulación permite seleccionar las membranas más apropiadas en función del caudal de permeado obtenido y en función del nivel de retención de la sustancia que se desea eliminar. En una segunda parte, se realizaron los ensayos experimentales en un sistema de laboratorio de filtración tangencial que trabaja con membranas planas. La retención obtenida para las sustancias estudiadas es de aproximadamente el 90%. Todo ello, con un buen caudal de permeado y usando bajas presiones de trabajo. Estos resultados demuestran la viabilidad de la tecnología y su potencial como tratamiento para mejorar la calidad de las aguas residuales de esta industria.

Hydrophobic mesostructured organosilica-based thin films with tunable mesoporosity offer promising opportunities for ultra low k applications. They are presently prepared by spin-on solutions and evaporation-induced self-assembly method (EISA) using polystyrene- b -polyethylene oxide block copolymers as structure-directing agents and methyltriethoxysilane (MTES) as organosilica precursor. With PS(1600)- b -PEO(1800) (between brackets is the molecular weights for blocks), different types of ordered mesostructures can be achieved by controlling the PS- b -PEO/MTES weight ratio, i.e. with Fm3m symmetry (evidenced for the first time in a organosilica film) and also with Im3m and P6mm space groups. Mesostructural ordering is characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and atomic force microscopy (AFM). The thin film porosity is analyzed using ellipsometric porosimetry (EP). Porogen removal and crosslinking of the organosilica network are followed by Fourier transform infrared spectroscopy (FTIR) and 29 Si magic angle spinning nuclear magnetic resonance (MAS NMR). The effect of the molecular weight and the hydrophilic lipophilic balance (HLB) of the used block copolymers on the mesostructure ordering is finally investigated using different types of polystyrene- b -polyethylene oxide block copolymers.

Homemade Cellulose Acetate nanofiltration membranes elaborated by phase inversion were surface modified by adsorption of alternated layers of sodium alginate (ALG) and chitosan (CHI). The membranes were characterised by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Energy Dispersive X-ray analysis (EDX) and by contact angle measurements. Separation performances of the prepared membranes are studied with 2 g/L synthetic aqueous solutions in frontal mode, under 15 bar pressure. Morphological characterization showed a formation of a lamellar structure till 15 bilayers followed by a transition to a granular structure. We observed an increase in water and salt fluxes till 20 bilayers. More adsorbed bilayers decrease fluxes. Retention rates of monovalent salts decrease and remain constant by reaching 15 bilayers. However, we observed a constant increase in the retention rate for salts containing divalent ions. Contact angle values showed a decrease till 15 bilayers followed by an increase till 30 bilayers. The correlation of the morphological characterization, contact angle measurements and the separation performances allowed as a better understanding of all the results. The layer-by-layer surface treatment makes CA membranes less sensitive to protein fouling with 15 adsorbed bilayers.

This research describes a simple approach for attaching poly(ethylene glycol) chains onto the surface of asymmetric ultrafiltration poly(etherimide) (PEI) membranes. Jeffamine ® M-2070, an amino terminated poly(propylene oxide)/poly(ethylene oxide) block copolymer (PEG-amine) was used as a surface modifying agent. PEI membranes prepared by conventional immersion precipitation were treated in an aqueous solution of PEG-amine and characterized by attenuated total reflectance FTIR, X-ray photoelectron spectroscopy, scanning electron microscopy and tensile tests. The effects of the PEG-amine concentration (2 and 10 wt%), modification time (0.5, 1, 3, and 5 h) and treatment temperature on the morphology, hydrophilicity, permeability, and anti-fouling property of the membrane were investigated. The water contact angle measurement and water absorbance ratio demonstrated that the treatment with PEG-amine for only 0.5 h resulted in a better wettability of the modified PEI membrane. An enlargement of the pore size was observed for the longer reaction times and the higher PEG-amine concentration accounted for a breaking of the PEI chains by over grafting. The best compromise in terms of morphology integrity, rejection and permeability performances, was obtained by using 2 wt% PEG-amine and reaction time lower than 5 h. Based on protein filtration experiments, the anti-fouling properties of the obtained membrane were evaluated, and the results showed a large improvement of resistance to protein fouling for the modified PEI membrane with respect to the unmodified one.

The present investigation revealed how the morphology and crystalline forms of a poly(vinylidene fluoride) (PVDF) membrane, prepared by using the vapor-induced phase separation (VIPS) method, were affected by the temperature at which PVDF was dissolved to form the casting solution. The results showed that there existed an important transition dissolution temperature, being referred to as the “critical dissolution temperature”, across which the morphology and crystalline forms of membranes drastically changed. With a dissolution temperature above the critical dissolution temperature, the prepared membranes were composed of nodules and the size of nodules decreased as the dissolution temperature decreased. And, with a dissolution temperature below the critical, membranes with lacy (bi-continuous) structure were obtained. In addition, the α-crystalline form of PVDF grew faster than the β-form when the dissolution temperature was below the critical, and the β-form became faster and dominant as the dissolution temperature increased to be above the critical. The existence of the critical dissolution temperature was observed for all the three solvents used in the present study, N-methyl-2-pyrrolidone (NMP), dimethylacetamide (DMAc), and N,M-dimethylformamide (DMF), indicating that the phenomena are general and not limited to a specific solvent. Also, it was observed that the two PVDF/NMP solutions, prepared with dissolution temperatures above and below the critical temperature, responded in different ways when water was added into the solutions. Though both solutions gelled, the solution with higher dissolution temperature started the gelation with a crystallization-initiation gelling process, while the other with a non-crystallization-initiation gelling. We propose that the competition between the two gelling processes play an important role in determining the PVDF membrane morphology and crystalline polymorphs, and the dissolution temperature can change the competition. And the critical dissolution temperature can be interpreted as a dissolution temperature across which the dominant gelling process switched.

A morphological study of polymeric membranes elaborated by VIPS process with the poly(etherimide) (PEI)/1-methyl-2-pyrrolidone (NMP)/water system was conducted using both experimental and numerical approaches. The mass transfer model is non-isothermal and integrated multicomponent diffusivities. The self-diffusion coefficients were estimated from the Vrentas and Duda free-volume theory and various formalisms that make a link between the self- and mutual-diffusion coefficients were tested. At different initial polymer concentration, the Dabral formalism also leaded to the best agreement between membrane morphology (determined by SEM analysis) and the predicted concentration profiles. The influence of the process parameters (RH and temperature) was then investigated on the membrane morphology. Reducing the relative humidity induced a longer delay in term of demixing time, leading to reduce the polymer concentration gradient near the air/solution interface, and therefore to prevent the cell size gradient in this region. Between 25 °C and 40 °C, the influence of the temperature on the concentration profiles was shown to be weaker. Lastly, the asymmetric membrane structures characterized by cell size gradients observed at the lowest polymer concentrations were prevented when doping the initial solution with a small amount of non-solvent. In such cases, the model predictions exhibited that the demixing time and the polymer concentration gradient were reduced, leading to more symmetric membranes.

This work describes the surface grafting control of poly(vinylidene fluoride) (PVDF) membrane with poly(ethylene glycol) methacrylate (PEGMA) via three different modification approaches of surface-initiated radical graft copolymerization, including thermal-induced radical polymerization, surface-initiated atom transfer radical polymerization (ATRP), and low pressure plasma-induced graft-polymerization. Two different surface grafting structures of PEGylated layer, brush-like PEGMA and network-like PEGMA, on PVDF membrane surface were achieved in this study. The chemical composition and microstructure of the various surface-modified PEGylated PVDF membranes were characterized by Fourier transform infrared spectroscopy (FT-IR), contact angle, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) measurements. Antifouling property of the modified PVDF membranes was evaluated according to the amount of protein adsorption and the filtration test for BSA solution in this study. Results show that the amount of adsorbed proteins on the modified PVDF membranes not only depends on the surface hydrophilicity and hydration capacity but also associates with the surface grafting structures of PEGylated layers on PVDF membrane surface. This study not only introduces different practical modification approaches to achieve a hydrophobic PVDF membrane grafting hydrophilic PEGMA, but also provides a fundamental understanding of various PEGylated grafting structures governing the performance of antifouling properties.

International audience; By extrapolation of the extensive use of cyclodextrin (CD)-modified materials in chromatography techniques, we study CD-containing membranes as contactors having facilitated transport properties in liquid/liquid extraction. Our main interest lies in the understanding and modelling of the mass transport mechanism for the development of pertraction applications using these membranes. The sorption and diffusion processes of xylenes as model molecules were studied through sorption experiments in membranes containing alpha-CD. The presence of highly pronounced induction times on sorption curves makes it impossible to use standard models, like the solution-diffusion one, to describe the experimental data. A generalized dual mode model has therefore been developed to account for three distinct regimes of strong facilitated transport membranes: (i) one controlled by diffusion within a membrane, (ii) one controlled by a kinetic retardation of solute entry into and out of a membrane, and (iii) one controlled by the kinetics of complexation formation. The permeant species are divided into two populations: one diffusing in the membrane and one forming immobile inclusion complexes with fixed CD sites. The model fits, which agree well with the experimental data using a limited number of adjustable parameters, indicate that the kinetics of interfacial transfer depends on the CD content.

The formation of a surface liquid layer on the top of membrane forming systems made of poly(ether-imide) (PEI) and N-methylpyrrolidone (NMP) was clearly demonstrated during water vapor-induced phase separation (VIPS) through several in situ investigation methods including optical microscopy and dynamic water contact angle measurements for a qualitative approach, and Raman confocal and FTIR microscopy for a quantitative one. A mechanism involving the shrinkage from the polymer-rich phase consecutively to the surface phase separation is proposed to account for the significantly high concentration of PEI in the surface liquid layer. The emergence of a surface liquid layer during the phase separation process is discussed in terms of implications on morphology of membrane fabricated using VIPS and how it contrasts with liquid-induced phase separation.

BACKGROUND: Water sorption by polymer solutions during film fabrication may affect the film morphology and thereby the film properties. RESULTS: Water vapour sorption isotherms at 40 °C of poly(ether imide) (PEI)/N-methyl pyrrolidinone (NMP) solutions were experimentally determined. Considering PEI concentrations ranging from 0 to 20 wt%, results obtained from gravimetric measurements and near-infrared (NIR) spectroscopy, indicative of the total weight uptake and the local water concentration in the bulk solution, respectively, showed that a first stage occurred featuring a quasi-linear time dependence of the weight fraction of absorbed water. Deviations from linearity dependent on the PEI concentration were afterwards observed, this behaviour being more marked for concentrations higher than 14 wt%. To achieve good predictions, the mathematical description of the sorption results must take into consideration both the classical approach using diffusion equations and the possible time dependence of the surface concentration of water at the air-facing interface. CONCLUSION: This paper presents an analysis of water vapour sorption in PEI/NMP solutions combining local and global quantifications of the water content through NIR and gravimetric methods. The development of a mathematical model suggests a possible surface layer formation at the air-facing interface. Copyright © 2008 Society of Chemical Industry

This work concerns to the development and characterization of support and ultrafiltration membranes from naturally occurring- kaolin clays as principal components. The preparation and characterization of porous tubular supports, using kaolin powder with corn starch as poreforming agent, were reported. It has been found that the average pore size was about 1 μm while the pore volume was 44% for supports sintered at 1150°C with a flexural strength of about 15 MPa. The deposition of the active layer was performed by slip casting method. The rheological study of various coatings with different concentration of kaolin powder, polyvinyl alcohol (PVA) and water under different conditions regarding temperature and stirring time was done. After drying at room temperature for 24 h, the membrane was sintered at 650°C. The average pore diameter of the active layer was 11 nm and the thickness was around 9 μm. The determination of the water permeability shows a value of 78 l/h.m2.bar. This membrane can be used for crossflow ultrafiltration. The application of the cuttlefish effluent treatment shows an important decrease of turbidity, inferior to 1.5 NTU and chemical organic demand (COD), retention rate of about 87%. So, it seems that this membrane is suitable to use for wastewater treatment.

This work aims to evaluate the potential of reverse micelles prepared from amphiphilic polylactide-b-poly(ethylene glycol) (PLA-b-PEG) block copolymers for controlled release of hydrophilic drugs. Different PLA-b-PEG diblock and triblock copolymers were synthesized by ring-opening polymerization of D- or L-lactide in the presence of a PEG macroinitiator. Reverse micelles were prepared by self-assembly of copolymers in a solvent/co-solvent/water system. Toluene was used as solvent, and ethanol as co-solvent to solubilize appropriate amount of water. The resulting nano-sized reverse micelles were able to encapsulate heparin in the hydrophilic core. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) were used to determine the size and morphology of reverse micelles. The results show that reverse micelles are spherical in shape with sizes below 100 nm. Drug loaded reverse micelles were embedded in biocompatible membranes by mixing with 10% PLA solution in toluene with 1:3 volume ratio. In vitro release studies were realized in phosphate buffer saline (PBS) at 37°C. Heparin was almost totally released within 24h. Triblock copolymer reverse micelles exhibited faster drug release than diblock ones probably due to the more compact micelle structure of the latter. Therefore, PLA-b-PEG reverse micelles could be promising for applications as carrier of hydrophilic drugs when embedded in biocompatible membranes.

The very recent developments in preparation of filtration membranes from self-assembled block copolymers (BCPs) are reviewed in this paper. We look into membranes with very sharp pore size distribution and the approaches for manufacture of nanoporous films, including etching and templating, the advantages of the new process based on micelle assembly and phase inversion. The paper is divided in two main sections. In the first part different strategies to prepare membranes from block copolymers are summarized. The second part looks into the different factors affecting the pore formation, morphology and the characteristics of the membranes made from self-assembly of block copolymers.

According to the environmental protection regulations, fluoride concentration is considered as a substance of priority for assessment of drinking water quality to determine their impacts on the environment and public health. Saharan groundwater (Algeria) contains an excess of fluoride ions. Regular consumption of this water by the population of the region may cause endemic fluorosis. To solve this problem, we propose to treat this water by adsorption on different materials, such as activated alumina (AA), sodium clay (SC), and hydroxyapatite (HAP) in order to enhance its quality by reducing its fluoride concentration. The maximum adsorption is achieved with an adsorption capacity of the order of 0.9, 0.667, and 0.370 mg/g and with a percentage of 90, 83.4, and 73.95% for AA, HAP, and SC, respectively. Indeed, the acidity and alkalinity of the medium significantly affect the adsorption of fluoride ions. Results deduced from the curves of adsorption isotherms of fluoride ions showed that the retenti...

Symmetric porous membranes were prepared from concentrated poly(ether-imide) (PEI) solutions using vapor-induced phase separation (VIPS) coupled with a drying pretreatment. Moderately concentrated solutions of PEI in N-methylpyrrolidinone (NMP) (14–16 wt%) were first cast on glass plates and the solvent was then allowed to evaporate under a dry air flow up to the desired concentration (16–38 wt%) before forming the membrane structure by VIPS. The polymer concentration profiles (confocal Raman microscopy) and model predictions were in good agreement to show that the evaporation stage did not induce a polymer gradient concentration with PEI/NMP systems. These results were confirmed by examination of the final membrane morphology (SEM).

Polysulfone hollow fiber membranes were fabricated by a dry/wet spinning process, with N-methyl pyrrolidinone (NMP) and water as solvent and coagulant, respectively. The results indicate that air-gap length and ambient humidity have dramatic effect on the membrane morphology. Macrovoids in the membranes disappeared, reappeared, and redisappeared with increasing air-gap length. Evidence was obtained showing that, because of the high affinity of NMP for water, water vapor was drawn to the dope to induce phase separation, resulting in a nascent structure in the dope before it was immersed in the coagulation bath. We proposed that, shortly after the onset of its phase separation in the air gap, the dope behaved as a transient gel, which can reasonably explain the disappearance and reappearance of macrovoids. On the other hand, when the air gap was long enough to allow phase separation of the entire dope before it reached the coagulation bath, macrovoids redisappeared. In addition, we observed that the air-gap length required for the disappearance and redisappearance of macrovoids decreased with increasing ambient humidity, which can be well reasoned by the decreasing contact time with the humid air needed to bring about phase separation of the dope in the air gap.

Summary: The n-hexylamine-initiated polymerization of Ne-trifluoroacetyl-L-lysine N-carboxyanhydride in N,N-dimethyformamide was studied by nonaqueous capillary electrophoresis. A polypeptide with a broad molecular weight distribution was obtained and side reactions were clearly identified for polymerization at room temperature. The possibility of living polymerization at 0 °C was demonstrated. Synthesis of living polypeptides by primary amine initiated polymerization of NCA at low temperatures.

Composite cellulose acetate (CA) based membranes having a hydrophobic top layer made of polymethylhydrosiloxane (PMHS) were prepared with the aim of desalination of brackish waters from the Sahel region of Tunisia having a total dissolved salt content (TDS) of about 4100 g.m-t-3. The porous substructure made of CA was obtained by a phase separation process from acetone/formamide ( 2 1 wt wt ) casting solutions. Two polymer concentrations (20 and 22 wt. %) were used with a heat post-treatment temperature going from 60 to 90°C in order to produce membranes with pore sizes responding to nanofiltration needs. Overcoating the CA substructure with a PMHS thin layer gave rise to the composite membranes. Scanning electron microscopy analysis showed the asymmetric and composite feature of the CA-PMHS membrane morphology. Contact angle measurements clearly pointed out a marked hydrophobic character of the composite membranes due to the PMHS surface modification. When compared to the corresponding unmodified CA membranes, the salt rejection determined by conductivity in the range of 78–93% was strongly enhanced whereas the pure water permeability of the composite membranes was reduced by a factor of 15–50% depending on the starting pore size. It results in the same salt retention — an improvement factor of 50–100% for the permeation rate when using the composite membranes. The ion rejection in decreasing order was SO42− > Cl− > NO32− and Mg2+ ≥ Ca2+ > Na+ for anions and cations, respectively.

The formation of polymer films produced by the phase separation process occurring when a cast poly(etherimide)/N-Methyl-2-Pyrrolidone solution was exposed to humid air was studied. It was found that above a relative humidity value of 27%, the films presented a cell-like structure. The size of the cells was shown to decrease when the relative humidity increased. This effect was more pronounced at the film/substrate interface than near the surface. A cell-size gradient from one face of the film to the other was also clearly observed. A phenomenological model has been proposed to explain the morphology obtained by a phase separation induced by the water vapor in the studied system, taking into account thermodynamics and kinetics considerations. In this model, the cell-like structure setting up is shown to result from a nucleation and growth process accompanied by a coalescence coarsening. It was illustrated by a composition path on the ternary phase diagram. It was shown how the relative humidity influenced the film composition leading to the preferential nucleation compared to the growth and coalescence of the cells. Finally, it was found that the cell-size anisotropy resulted in the solvent and non-solvent mass transfers in the film, bringing to the fore the determining role of kinetics.

International audience; This paper presents a new technique for making porous polymer membrane without using organic solvent from a nontoxic and biodegradable polymer, polyvinyl alcohol (PVA). This method consists first in inducing a phase separation in water – 10 wt% PVA solution, by increasing the temperature above the polymer cloud point temperature. A PVA with a degree of hydrolysis of 72% was selected according to its low cloud point temperature (47 1C for 10 wt% polymer) allowing saving energy. The second step of the preparation procedure corresponds to the stabilization of the structure by jointly cross-linking the polymer to stabilize the porous morphology and drying to evaporate the dilute phase. A chemical cross-linking reaction was performed using glutaraldehyde with a molar proportion (GA/monomer alcohol) of 0.04. Results showed that the cross-linking control was the key step to obtain porous membrane morphology. Consequently, the temperature and the catalyst volatility of the cross-linking reaction act directly on the final membrane morphology. Additionally, it was shown that the control of the relative humidity during the elaboration process had an effect on the porosity of the membrane skin layer as depicted by SEM pictures and filtration tests.

Structure formation of poly(ether-imide) films using vapor induced phase separation was studied in relation with the elaboration process. Dense and cellular structure can be obtained depending on the processing parameters. When the solvent evaporation took place under humidified air, kinetic data from gravimetric measurements showed that the overall mass of the film was first increasing before decreasing to a plateau. An analysis in terms of drying rate revealed that mass transfers were occurring as if there was a thin layer of volatile molecule at the top of the forming film. Solvent and non-solvent transfers were demonstrated to be closely dependent on the relative humidity.

The focus of this work is to assess the quality of porous membranes prepared from naturally occurring kaolin clays and to evaluate the performance of tubular ceramic membranes treating integrated raw effluents from seafood industry. This material has been chosen due to its natural abundance, its non-toxicity, low cost and its valuable properties. The preparation and characterization of porous tubular ceramic membranes, using kaolin powder with and without corn starch as poreforming agent, were reported. SEM photographs indicated that the membrane surface was homogeneous. The effects of material compositions, additives and the relatively lower sintering temperature, ranging from 1100° to 1250°C, on porosity, average pore size, pore-size distribution and mechanical strength of membranes have been investigated. A correlation between microstructure and mechanical properties of membranes has been discussed. The performance of the novel ceramic membranes thus obtained was determined by evaluating both the water permeability and rejection. The obtained membrane was used to treat cuttlefish effluents generated from the conditioning seawater product industry which consumes a great amount of water. Cross-flow microfiltration was performed then, in order to reduce the turbidity and chemical oxygen demand (COD).

International audience; As a result of numerous advantages such as high surface areas, rapid sorption rates and lowhydrodynamic resistances, activated carbon felts (ACF) are interesting materials for applications inwastewater treatment. This paper studies the use of a polyacrylic acid grafted and a non grafted ACF inthe sorption of Co2+, Ni2+ and Sr2+ from a synthetic solution (high NaNO3 concentration) representing anuclear wastewater. Scanning electron microscopy and surface area analysis were employed tophysically characterize bothmaterials. Experimental results for the sorption of ternary mixtures allowedus to uncover a selectivity among the three cations that could not be deducted directly from the sorptionisotherms of individual cations. In all cases, differences in the sorption capacity could be related to theelectronegativity of the metal cations. Complementarily, removal of Co2+, Ni2+ and Sr2+ by a fixed bedcolumn containing non grafted ACF was studied by means of monoelement and ternary sorptionexperiments. Only breakthrough curves of individual metals could be fitted by the Thomas model.Overshot of Sr2+ and Co2+ was observed on ternary sorption experiments. The set of results obtainedindicate that ACF can potentially be employed in the treatment of nuclear effluents where a selectiveseparation of Sr2+ from Ni2+ and Co2+ is required.

The solution properties (proton uptake and viscosity) and the adsorption of poly(vinylimidazole) (PVI) and partially quaternized poly(vinylimidazoles) (PQPVI 0 to 52%) onto silica are studied at pH 3, 5 and 7, at ionic strengths of 10 −3 to 10 −1 M. For all pH values, adsorption peaks for PQPVI are between 2 and 4%, where electrophoretic mobility is minimum. Adsorption decreases with pH and increases with salinity. Results compare well with previous data at pH 10 [Bohmer et al., Colloids Surf. A 99 (1995) 53]. Polymer uptake results from specific bonds between acidic silica and basic imidazole. However, polymer uptake is strongly altered by electrostatic interactions. The charge balance at the isoelectric point shows that the adsorbed layer enhances surface ionization through charge compensation.

Water soluble β-cyclodextrin polymers were prepared from β-cyclodextrin crosslinked with epichlorohydrin under basic conditions. The influence of preparation conditions on the molecular weight distribution has been investigated. The knowledge of this relationship allows for the choice of reaction parameters according to the desired weight distribution of the β-cyclodextrin polymer. A procedure was developed for the preparation of high molecular weight water soluble polymer ( M w higher than 10 4 ).

A zipper-assembly of micelles into 2D/3D coatings is reported. Block copolymer micelles that incorporate a poly(n-octadecyl methacrylate) block are zipped and unzipped on demand onto a PMMA surface. The mechanism implies an interdigitation of molecular brushes enabling 15 nm micelles to be assembled into monolayers or multilayers.

International audience

The concept of self-healing has created a paradigm shift in the development of a new kind of responsive polymeric materials, which have traditionally been used in a passive role. Inspired by nature, the advancements made in this nascent field of research have given materials the ability of not only sensing damage but also responding and mending themselves in an appropriate manner. Self-healing in polymers can be autonomous, without the need for human intervention, or nonautonomous, requiring some form of external stimulus. The latter type involves the incorporation of dynamic bonds within the polymeric system, giving the ability to heal multiple times. This minireview discusses some of the prominent self-healing polymeric systems that harness different dynamic bond chemistries, with the aim of highlighting the potential of dynamic bonds to prepare such advanced materials.

International audience; The use of nanofiltration as a pretreatment step in a zero rejection process was investigated. Nanoflux, a nanofiltration simulation software, was used to predict the rejection of Co2+ and Ni2+ from a salty multi-element matrix whose concentration is similar to seawater. Orientation simulations prior to filtration experiments were made with Nanoflux in order to predict ionic rejections. Previously, the multi-element matrix solution speciation was studied by JChess. It was shown that the effective membrane charge and the effective membrane thickness, adjusted through the filtration of a single salt NaNO3 solution, could be used to predict the ionic rejections of the multi-element solution for two commercial nanofiltration membranes. The elevated concentration of NaNO3 in the multi-electrolyte solution did not reduce the high ionic selectivity of divalent ions. Predicted values were in good agreement with experimental results at neutral pH of the multi-electrolyte solution.

A combined fluorescence analysis, involving the use of steady-state fluorescence and fluorescence anisotropy was used, allowing eliciting information about the structural changes induced on trypsin after exposure to membrane surfaces with diverse chemistry, designed through a layer-by-layer methodology. Using this monitoring strategy it was possible to understand the influence of the surface chemistry on the structural characteristics of the attached proteins and how they relate to changes of their activity resulting from the adsorption process. This knowledge may be used to direct the development of surfaces with suitable chemistry, leading enzymatic-based processes with improved performance. The results obtained show clearly that trypsin exposed to different membrane surfaces, changes its conformation, either if it adsorbs to the membrane or if it remains in solution. A significant loss of enzymatic activity was observed upon the adsorption process, for the adsorbed and non-adsorbed protein. This loss of the trypsin activity was correlated with the presence of molecular unfolding events that mediate trypsin-membrane surface interactions and the decrease of the molecular mobility of the adsorbed trypsin, which was shown to be dependent on the chemical characteristics of the membrane surface. Changes on the selectivity of the adsorbed trypsin were also observed, and may be ruled by the strength of the enzyme-surface interactions established.

When pressure is applied to dynamic interactive membranes consisting of micelles composed of a triblock copolymer, their morphologies can be fine-tuned. Membranes with a range of porosities are accessible which can regulate and thereby control filtration performance and also display effective autonomous healing.

The aim of our researches is to study the interplay between membrane morphology and elaboration parameters during non-solvent induced phase separation (NIPS) processes. The present investigation is to correlate the solvent-nonsolvent mass transfer kinetics with the structural morphology and properties of polymeric membranes obtained via water vapour induced phase separation (VIPS) process. For the first time, we have monitored and quantified mass transfer kinetics during VIPS process on homogeneous solution of poly-(vinylidene fluoride) (PVDF) dissolved at two different temperatures in NMP, using near IR spectroscopy (NIR) with chemometric model. A significant change in mass transfer rate (i.e., water penetration) has been observed much earlier than the liquid demixing of the polymer solution occurs for two studied dissolution temperatures. Consecutively to the water penetration, modifications in the physical state (gelation) of the polymer started to occur prior to reaching demixing process. This phenome...

Plasma-enhanced (PE)CVD is used to create, in a single step, a superhydrophobic (SH) (water contact angle over 150°) layer starting from hexamethyldisiloxane (HMDSO) vapor (i.e., without fluorine) in a low-frequency, capacitively coupled plasma reactor under low pressure. Several SH microstructures are obtained, depending on experimental parameters (gas pressures, substrate rotation, pulsed glow discharge, plasma duration) deposited on various substrate types. The presented technique can produce thin SH transparent films (below 1 µm) or thicker ones (above 10 µm) to modify the surface of a macroporous hydrophilic membrane in order to render it SH with a water transmembrane pressure close to 2 bar.