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Préparation et étude de Membranes Asymétriques Polyalcoxyétherimides (PEI) pour la séparation de composés organiques de l'eau

Abstract : The work aimed to prepare co-polyalkylether-imide (PEI) asymmetric membranes in order to get high flux water selective polymeric membranes suitable for the separation of organic molecules from aqueous mixtures by membrane processes. The separation of liquid mixtures (i.e. toluene heptane, water ethanol and low concentrated organic solute in aqueous solutions) was studied by pervaporation (PV) and by nanofiltration (NF) using homemade integrally skinned asymmetric PEI membranes. These membranes were prepared under controlled experimental conditions from DMF-H2O solutions of the corresponding polyamic acid (PAA) with respect to the ternary phase diagram; after the wet phase inversion in a water bath, the PAA membranes were imidized by thermal treatment. The membrane physical properties (IR, TGA) were characterized and the related morphologies, recorded by SEM, were used to optimize the asymmetric membrane preparation to improve the separation properties by tuning the thickness of the dense top layer. The performances of the pervaporation and nanofiltration separations were examined in the light of the influence of three sets of parameters, i.e. membrane elaboration parameters (dope composition, inversion bath temperature), experimental permeation conditions (temperature, applied pressure) and solute molecular properties (molecular weight, radius, polarity). The PV results showed that tight asymmetric PEI membranes could well be obtained, giving rise to a molecular selectivity in agreement with the solution-diffusion model. The NF results obtained with diluted organics in water (500ppm) have shown that the degree of rejection of the organic solutes was strongly linked to the PEI elaboration conditions and to the solute properties. The molecular cutoff values (MWCO) of the membranes were determined with a series of polyethyleneglycol (400 < Mw (g/mole) <6000) for an applied NF pressure up to 10 Bar; it was shown that the PEI membrane MWCO could be ranged between 400 and 1000g/mol at 30°C. It was also found with some PEI membranes that high permeation fluxes together with good separation selectivity could be obtained leading to interesting performances compared to literature data. Thus, it is expected that the development of these new asymmetric block copolyimide rubbery membranes might give rise to high performance membrane systems for applications in liquid-liquid separations, in particular in nanofiltration separations
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Ayman Taha Elgendi. Préparation et étude de Membranes Asymétriques Polyalcoxyétherimides (PEI) pour la séparation de composés organiques de l'eau. Autre. Institut National Polytechnique de Lorraine, 2010. Français. ⟨NNT : 2010INPL046N⟩. ⟨tel-01748804⟩



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