La présente étude a été consacrée à l'étude du potentiel du PDMS pour l'élaboration d'un procédé de séparation membranaire à sélectivité variable et contrôlée. La nanofiltration se base une théorie relativement jeune. Les mécanismes impliqués dans les performances des membranes sont encore sujet à controverse au vu des données de la littérature. La caractérisation du gonflement solvo-dépendant du polymère, ainsi que de ses propriétés de compressibilité à l'état gonflé, ont permis de relier directement les propriétés de perméation et de tamisage moléculaire d'une membrane de PDMS à son état physico-chimique. L'étude de l'influence des paramètres opératoires a dans un premier temps permis d'apporter des éléments de compréhension significatifs concernant les propriétés de perméation résultant de la variabilité de l'agencement structural et géométrique du réseau polymérique. Degré de gonflement, compressibilité de la membrane lorsque soumise à la pression transmembranaire, affinités solvant/membrane et viscosité du solvant ont été mise en avant pour décrire le flux de solvant à travers la membrane. Au vu des résultats, ce dernier résulterait davantage d'un transport de type hydraulique à travers les interstices du PDMS gonflé, qui se comporte analogiquement à un système poreux dans cet état. Les mécanismes de transport impliqués ont pu être confirmés et agrémentés au cours d'une étude de la rétention de molécules modèles : les polyéthylèneglycols. Il a alors été montré, via l'étude de leur rétention individuelle, la faisabilité d'un procédé membranaire dont les performances sont variables et peuvent être ciblés par un choix adéquat des conditions opératoires. Deux types majeures d'influences ont alors pu être soulignée : celles liées à la structure du système solvant/PDMS et celles attribuées aux propriétés physico-chimique de la solution à traiter, présentant des effets synergique pour certains d'entre eux. Après avoir démontré la flexibilité contrôlée des performances de filtration, l'application du système de NF a été concrétisée par l'étude de la purification et du fractionnement de peptides : une purification d'un milieu issu d'une synthèse par voie chimique (un hydrazynopeptide) et le fractionnement ciblé d'un hydrolysat de protéines en provenance de ressources agroalimentaires. Cette étude prospective a alors permis de conclure à de prometteuses capacités du système de NF pour la mise en oeuvre de séparations membranaire dont la sélectivité et la productivité peut être appréhendée et ciblée par des conditions opératoires adaptées / The present study aimed to study the ability to build an adaptative and controlled separation process using PDMS membranes for organic solvent nanofiltration (OSN). Despite the well understanding of mechanisms implied in the performances of nanofiltration in aqueous media, the ones conditioning OSN productivity and sieving properties remains unclear. The characterization of the PDMS swelling when put in contact with several solvent and submitted under pressure allowed for correlating the structural conformation of the PDMS membrane to its permeation properties. The study of the influence of different operating parameters on the solvent fluxes has brought significant insights in the understanding of permeation mechanisms. Swelling degree (SL), membrane compressibility under transmembrane pressure (TMP), solvent/membrane affinity and solvent viscosity were pointed out as major parameters governing the filtration through PDMS membranes. The results concluded on a molecular transport attributed to hydraulic transport through the swollen PDMS, which behavior in this state was similar to a porous material. The transport mechanisms were confirmed and deepened with a study of solute retention using homologous series of polyethylenglycols as « model » molecules. The results have shown the ability to build a separation process with targeted performances when using the appropriate operating conditions (TMP, SL, temperature...). Two main categories of impact were shown to condition the selectivity and the productivity of the membrane: the ones attributed to the polymer/solvent layout and the ones concerning the physico-chemical properties of the filtrated solution. Both categories have in addition presented synergetic effects on the process performances. After the demonstration of the ability to vary and control the sieving properties of the PDMS membranes, the nanofiltration system was applied to two concrete case studies: a purification of a hydrazynopeptide after its production via a chemical synthesis and a fractionation of a protein hydrolyzate originating from renewable resources. In both cases, the prospection of the PDMS ability in terms of targeted selectivity and productivity showed interesting results that confirmed a promising development of a separation process among the sieving properties can be regulated by the application of suitable operating conditions

L’objectif de cette étude était d’améliorer les performances de séparation OSN de membranes commerciales en vue d’applications en métathèse dans laquelle des catalyseurs hautement dilués sont utilisés. Dans ce travail, des membranes polymères commerciales ont d'abord été étudiée pour caractériser leurs performances dans des milieux organiques en utilisant des mélanges binaires très dilués solute-solvant. Sur la base d'une revue de la littérature, il a été montré que la membrane PERVAP4060, dont le PDMS est la couche active dense était un candidat prometteur pour la nanofiltration milieu organique (OSN). En tant que membrane poreuse, les supports commerciaux AMS et PAN ont également été pris en compte. Dans cette étude, nous avons considéré la modification sur la surface pour conserver les propriétés de matrice polymère. Les multicouches de plasma Ar/O2 et/ou de polyélectrolytes ont été utilisées pour la préparation de membranes prototypes. Les membranes non modifiées et modifiées ont été testées dans des conditions OSN en utilisant des mélanges d'alimentation biniares. Plusieurs solutés très dilués, le ligand organophosphoré R-BINAP, un catalyseur de transfert de phase (ToABR) et des alcanes linéaires ont été étudiés. Le R-BINAP et le ToABR ont tous deux été utilisés dans la plage de 0,0001 à 0,5% en masse et la plupart des expériences ont été réalisées ensuite avec des concentrations de 0,05% en masse de soluté dans le toluène. Il a été montré que le PDMS était capable de retenir 80% de R-BINAP et environ 93% de ToABr dans du toluène. Après modification par les dépôt LBL, le taux de rejet est amélioré avec les membranes modifiées PERVAP4060, conduisant à une rétention de 88% du R-BINAP avec un dépôt de 10 bicouches de polyélectrolytes PAH / PSS en surface, ce taux de rejet pouvant atteindre 95% lorsque le nombre de bicouches est de 20. Le taux de rejet de ToABr augmente à 97%. Les performances de la membrane ont été étudiées sous différentes pressions comprises entre 1 et 40 bars; le haut rejet, encore observé dans ces conditions OSN, plaide résolument en faveur d'un mécanisme de transfert de type solution-diffusion à travers le PDMS. On a également étudié le traitement des mélanges ternaires mimant le mélange catalyseur / solutés / solvant, correspondant à l'hydroformylation ; aucun signe de couplage n’a été détectée et le taux rejet du soluté de masse molaire la plus forte est resté inchangé. D'autre part, l'amélioration du taux de rejet a également observée à partir des membranes poreuses après modification. Le taux de rétention du C44 dans l'AMS a été atteint 75% après modification par 10 bicouches de PDDA / PSS, alors qu’il n'était que de 25% avant modification. Dans le PAN modifié, le taux de rejet des solutés obtenus est dans la plage de 37 à 50%, alors qu’il n'était que de 3 à 7% en masse avant modification. L'inconvénient de la membrane poreuse est toutefois la forte diminution du flux après le dépôt des couches multiples. / The objective of this study was to improve the OSN separation performance of commercial membranes for metathesis applications in which highly diluted catalysts are used. In this work, commercial polymeric membranes were first studied to characterize their performance in organic media using very dilute solute-solvent binary mixtures. Based on a literature review, it was shown that the PERVAP4060 membrane, of which PDMS is the dense active layer, was a promising candidate for organic solvent nanofiltration (OSN). As a porous membrane, the AMS and PAN commercial supports have also been taken into account. In this study, we considered the modification on the surface to improve the separation properties of polymeric OSN membranes. Ar/O2 plasma and/or polyelectrolytes multilayers were used for the preparation of new prototype membranes. Unmodified and modified membranes were tested under OSN conditions using binary feed mixtures. Several highly dilute solutes, organophosphorus ligand R-BINAP, phase transfer catalyst ToABR, and linear alkanes have been studied. Both R-BINAP and ToABR were used in the range of 0.0001 to 0.5% by weight, and most experiments were subsequently performed with 0.05% solute concentrations in toluene. It has been shown that PDMS can retain 80% R-BINAP and about 93% ToABr in toluene. After modification by the LBL deposition, the rejection is improved with the modified PERVAP4060 membranes, leading to an 88% rejection of R-BINAP with a deposit of 10 PAH / PSS polyelectrolyte bilayers at the surface and this rejection being able to reach 95% when the number of bilayers is 20. ToABr rejection increases to 97% with the ten bilayered membranes. The performance of the membrane was studied under different pressures of between 1 and 40 bar; the high rejection, still observed in these OSN conditions, strongly supports a solution-diffusion transfer mechanism through the PDMS. The treatment of ternary mixtures mimicking the catalyst/solute/ solvent mixture corresponding to the hydroformylation has also been studied; no evidence of coupling was detected, and the highest retention remained unchanged. On the other hand, the improvement of the rejection also observed from the porous membranes after modification. The rejection of C44 in the AMS was reached 75% after modification by tention10 bilayers of PDDA / PSS, whereas it was only 25% before modification. In the modified PAN, the rejection of the solutes obtained is in the range of 37 to 50%, whereas it was only 3 to 7% by weight before modification. The disadvantage of the porous membrane, however, is the sharp decrease in flux after the deposition of the multiple layers.

The integration of organic solvent nanofiltration in processes of fine chemistry involving homogeneous metal catalysts has a great potentiel because this eco-friendly process, efficient at molecular scale, does not desactivate the catalyst contrary to conventionnal distillation. The aim of this study is to integrate organic solvent nanofiltration in the process of 10-undecenitrile hydroformylation in toluene. A one-step nanofiltration does not permit to fulfill the goals of the separation, which are to extract the product and to recycle the catalytic system (Rh, biphephos). Simulations of membrane cascades based on experimental data of flux and retention according to the concentration (acquired in the first part of the thesis) highlighted that a four stages cascades with recycling is realistic and competitive for an industrial plant. / L'intégration de la nanofiltration organique dans les procédés de chimie fine impliquant des catalyseurs organométalliques solubles a un fort potentiel car ce procédé éco-efficace de séparation à l'échelle moléculaire ne désactive pas les catalyseurs contrairement à la distillation classiquement utilisée. L'objectif de cette thèse est d'intégrer la nanofiltration organique dans le procédé d'hydroformylation du 10-undecenitrile dans le toluène. Un procédé en une étape de nanofiltration ne permet pas de remplir les objectifs de séparation qui sont l'extraction du produit et le recyclage du système catalytique (Rh, biphephos). Des simulations de cascades de membranes basées sur les données expérimentales de flux et de rétentions variables en fonction de la concentration, acquises en première partie de thèse, ont permis d'identifier un design de cascade à 4 étages avec recyclages réaliste et compétitif pour une conception industrielle.

Among the next generation materials being investigated for membrane development, partially reduced Graphene Oxide (rGO) has received increasing attention from the membrane community. rGO-based nanofiltration membranes have shown promising results in applications such as partial desalination, organic contaminant removal, gas-phase separations, and separations from solvent media. rGO offers a unique platform compared to common polymeric membranes since it can be used for separation applications in both aqueous and organic solvent media. An rGO-based platform could also be utilized to synthesize reactive membranes, giving rGO membranes the additional capability of reactively removing organic contaminants. This research focuses on the synthesis of rGO and nanocomposite membranes for applications including the separation of high-value phenolic compounds from a solvent-water mixture, removal of organic contaminants, and treatment of refinery wastewater. First, the behavior of a rGO membrane in water and isopropanol was investigated along with its ability to separate high-value, lignin-derived oligomeric compounds from a solvent-water mixture. This study revealed the formation of stable sorbates of water in the GO channels that resulted in declined membrane permeance and improved size-exclusion cutoff. Through controlled reduction of GO by heat treatment, it was demonstrated that physicochemical properties of the GO membrane could be modulated and separation performance tuned based on the extent of reduction. A varying degree of interlayer spacing was attained between the GO laminates by controlling the O/C ratio of GO. This allowed the rGO membrane to achieve tunable molecular separation of lignin-derived model oligomeric compounds from a solvent-water mixture. Second, the mechanism of ionic transport through the rGO membrane was studied as well as its application in partial desalination and removal of persistent organic contaminants from water. Through comprehensive experimental investigations and mathematical analysis, along with the aid of the extended Nernst Planck equation, the impacts of steric hindrance and charge interactions on the underlying ion transport mechanism were quantified. Charge interactions were observed to be the dominant exclusion mechanism for the rGO membranes. The application of rGO membranes for treatment of high TDS produced water was investigated with the goal of partial hardness and dissolved oil removal. In addition, this study demonstrated the removal of emerging organic contaminants, specifically perfluorooctanoic acid, by rGO membranes and elucidated a charge interaction-dominated exclusion mechanism for this contaminant, as well. Finally, rGO-based and microporous polyvinylidene fluoride (PVDF)-based catalytic membrane platforms were synthesized for removal of organic contaminants via an oxidative pathway. Herein, an advanced oxidation process was integrated with membrane technology by the in-situ synthesis of Fe-based nanoparticles. The unique capability to oxidatively remove contaminants in a continuous mode of operation was explored in addition to the separation performance of the membrane. The rGO-based platform achieved high oxidative removal of trichloroethylene via a sulfate-free, radical-mediated pathway, while simultaneously removing humic acids from water and potentially eliminating undesired side reactions. A PVDF-based microporous catalytic membrane platform was shown to effectively remove organic impurities, such as Naphthenic acids, from high TDS produced water by the same pathway. The enhancement of reaction extent for elevated temperatures and longer residence times was also quantified in this study. These studies benefit the membrane community in the following ways: 1) The work identifies the critical role of the physicochemical properties of GO, such as the O/C ratio and water sorption, for determining the permeability-selectivity of rGO membranes for solvent nanofiltration. 2) Investigations of ion transport through rGO membranes led to an understanding of a charge-dominated separation mechanism for ion retention. The Nernst-Planck equation-based approach employed in this study would enable further assessment and comparison of rGO membranes under a wide set of parameters. 3) Catalytic membrane platforms (rGO and microporous PVDF-based) were synthesized for conducting advanced oxidation reactions in the porous membrane domain, demonstrating potential applications in environmental remediation of organic contaminants.

Membrane technology has great potential to complement traditional energy-intensive molecular separation processes such as distillation, with the advantage of low footprint generation. However, this would only be achieved with the development of better membranes able to operate in challenging conditions, including combinations of organic solvents, high temperatures, extreme pHs, and oxidative environments. This dissertation aims to use high-performance polymeric materials that can withstand temperatures of 120 °C in polar aprotic solvents like N,N-dimethylformamide as separation membranes, using different crosslinking strategies and alternative routes for commercially available material processing. The thesis will be divided into two main approaches. The first approach will start from soluble polyimides as precursors, with designed functionalities that allow post-membrane modifications, such as chemical crosslinking, thermal crosslinking, and thermal rearrangement to enhance the material's chemical resistance. The focus will be on the polyimide synthesis by an alternative one-step room-temperature polyhydroxyalkylation reaction. The chemical and thermal crosslinking take place without involving the imide bond, by incorporating a highly tunable functional group (isatin) in the synthesis of the materials. Propargyl as a pendant group will be used for the thermal crosslinking, and hydroxyl group for the thermal rearrangement. In all cases, the obtained membranes were stable in common organic solvents at 120 °C. The second approach will start from intrinsically solvent-resistant and commercially available poly(aryl ether ketone)s, turned into membranes by a closed-loop modification-regeneration strategy, to address long-term separations in organic solvents at high temperatures. We present for the first time porous poly(aryl ether ketone) flat-sheet and hollow fiber membranes prepared without the use of strong acids or high temperatures. Two methodologies are proposed. The developed strategies shall contribute toward avoiding the regular consumption of new materials and waste generation since the polymer used does not require crosslinking for its stability under organic solvents.