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Currently, the only cure for liver failure is orthotopic liver transplantation. However, there are insufficient donor organs available to treat every patient on the transplant list and many die before they are able to receive a liver transplant. The bioartificial liver (BAL) device is a potential extracorporeal treatment strategy utilising hepatocytes or hepatocyte-like cells (HLCs) within a bioreactor to recapitulate normal liver function and therefore ‘bridge’ a patient with liver failure until they receive a transplant. The work in this thesis utilised tissue engineering methods to develop novel approaches to BAL device design through development and characterisation of a polymer membrane scaffold (“PX”) for hollow fibre bioreactor (HFB) culture and a HLC source generated from the transdifferentiation of pancreatic AR42J-B13 (B13) cells. A flat sheet membrane model was used for the development of asymmetrical, hydrophobic polystyrene (PS) phase inversion membranes. Oxygen plasma significantly increased PS membrane surface wettability through addition of oxygen functional groups to create an environment conducive for cell culture. The treated membrane was henceforth referred to as “PX”. The culture medium HepatoZYME+ was investigated for its ability to induce transdifferentiation of B13 cells to HLCs and maintain the hepatic phenotype. Overall, HepatoZYME+-cultured cells experienced viability loss. A diluted version, “50:50”, showed induction of the hepatic markers carbamoylphosphate synthetase-1 (CPS-1) and HNF4α, as well as a change towards a HLC morphology. When using 50:50 as a maintenance medium, transdifferentiated HLCs retained loss of pancreatic amylase and also induction of hepatic markers, with comparable serum albumin secretion to the established Dex + OSM treatment. However, culture viability in 50:50 was still compromised. Therefore, HepatoZYME+ based media were deemed unsuitable for induction and maintenance compared to Dex-based protocols. PX flat sheet membranes were able to support culture of B13 cells and also the human osteosarcoma cell line, MG63, demonstrating improved cell attachment over non-surface treated PS membranes. PX membranes supported transdifferentiation of B13 cells to HLCs, presenting with loss of pancreatic amylase, induction of the hepatic markers transferrin, GS and CPS-1 and serum albumin secretion. Furthermore, PX showed no change in mass or loss of culture surface area over 15 days in culture conditions. Together, the novel membrane material and the media formulation and feeding regime developed have strong potential to be translated to a HFB setting and guide future BAL device design.

Durch verschiedene Modifizierungen an der Blutkontaktseite von Hohlfasermembranen sollte eine Verbesserung der Bio- und Blutkompatibilität erreicht werden. Zur Modifizierung wurden verschiedene biologisch wirksame Moleküle verwendet. Weiterhin wurden zwei Modifizerungsstrategien verfolgt. Zum einen eine Modifizierung, bei welcher das Material der Hohlfasermembran vor deren Herstellung verändert wird. Und zum anderen eine selektive Modifizierung der Blutkontaktseite nach der Herstellung der Hohlfasermembran.

Durch verschiedene Modifizierungen an der Blutkontaktseite von Hohlfasermembranen sollte eine Verbesserung der Bio- und Blutkompatibilität erreicht werden. Zur Modifizierung wurden verschiedene biologisch wirksame Moleküle verwendet. Weiterhin wurden zwei Modifizerungsstrategien verfolgt. Zum einen eine Modifizierung, bei welcher das Material der Hohlfasermembran vor deren Herstellung verändert wird. Und zum anderen eine selektive Modifizierung der Blutkontaktseite nach der Herstellung der Hohlfasermembran.

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Cette thèse présente une approche originale du procédé de distillation membranaire avec balayage gazeux pour la concentration des solutions thermosensibles (SGMD). Pour ce faire, un nouveau contacteur membranaire avec des fibres creuses métalliques a été conçu afin réaliser le procédé de distillation à basse température. La chaleur nécessaire au procédé est produite au niveau des fibres par effet Joule, plutôt qu'à partir de chaleur latente de la phase aqueuse. La génération localisée de la chaleur a comme conséquence une réduction du phénomène de polarisation de la température. Des fibres creuses en acier inoxydable ont été synthétisées avec les propriétés structurales appropriées et une bonne résistance mécanique. La surface des pores des fibres a été rendue hydrophobe par le dépôt d'une fine couche d'un élastomère. En outre, une nouvelle méthode « verte » a été développée pour fabriquer des fibres creuses en alumine et acier inoxydable. Cette méthode est basée sur la gélification ionique des bio-polymères et ne n'utilise pas des solvants nocifs. L'étude expérimentale détaillée du SGMD a permis de déterminer l'influence de différents paramètres opérationnels sur les performances du procédé. Il a été démontré que l'effet Joule permet d'améliorer le flux et l'efficacité de la séparation non seulement pour le SGMD mais aussi pour la pervaporation. / This thesis presents an original approach for the concentration of thermo-sensitive solutions: the Sweep Gas Membrane Distillation (SGMD) process. A new membrane contactor with metallic hollow fibers has been designed and allows the distillation process to be operational at low temperature. Heat is generated in the fibers by the Joule effect, rather than being supplied as latent heat in the liquid bulk. The localized generation of heat results in a reduction of temperature polarization phenomena. The stainless-steel hollow fiber membranes have been synthetized with appropriate structural properties and sufficient mechanical strength. The pore surface of the fibers has been made hydrophobic by the deposition of a thin layer of an elastomer. Moreover, a novel and green method is presented to fabricate alumina and stainless-steel hollow fibers. This method is based on ionic gelation of a biopolymer and completely avoids the use of harmful solvents. By a detailed experimental study of the SGMD the influence of different operational parameters on the process performance has been investigated. The improvements in the flux and the separation efficiency using Joule effect have been successfully demonstrated, even in the case of pervaporation.

La capture du dioxyde de carbone (CO2) en postcombustion est une stratégie importante pour la limitation de l’effet de serre. Le procédé de référence est l’absorption du CO2 dans des solutions aqueuses aminées, suivie par une étape de stripage du solvant. La technologie mature associée à ce procédé est la colonne à garnissage. Toutefois, afin de rendre le procédé plus attractif, il convient de l’intensifier en réduisant le volume des équipements et le coût énergétique associé. Les contacteurs membranaires à fibres creuses (CMFC) constituent une alternative aux colonnes à garnissage. Les CMFC permettent de développer d’importantes aires spécifiques conduisant potentiellement à une intensification des transferts gaz-liquide. Ainsi, l’utilisation des CMFC réduirait la taille des installations, mais aussi diminuerait la consommation énergétique par la diminution de la quantité de vapeur de stripage. Cependant, l’utilisation de CMFC dans les étapes d’absorption et de stripage dans des conditions industrielles a été peu étudiée. Afin de combler cette lacune, des modèles à différents niveaux de complexité : monodimensionnel, bidimensionnel, isotherme et adiabatique ont été développés, comparés et validés. Ceci afin d’identifier le niveau de complexité approprié. Les résultats de simulation ont mis en évidence le potentiel d’intensification des CMFC dans l’étape d’absorption et aussi de stripage, se traduisant par une réduction en volume de 4 à 10 fois par rapport aux colonnes à garnissage. Néanmoins, les CMFC peuvent difficilement réduire le coût énergétique du procédé étant donné que l’étape de stripage fonctionne dans des conditions très proches de la limite thermodynamique / Post-combustion CO2 capture (PCC) is an important strategy in mitigating greenhouse effect. The reference process in PCC is the CO2 absorption into amine aqueous solutions, followed by the regeneration (or stripping) of the solvent. The robustness of packed columns makes it the standard technology for both absorption and stripping steps. However, the treatment of large quantities of flue gases requires itself equipment of a large size. Hollow fibre membrane contactors (HFMC) are considered as one of the most promising strategies for intensified CO2 absorption process, due to their significantly higher interfacial area than that of packed columns, allowing to reduce the equipment size. In addition, this would reduce the energy penalty of the process by reducing the required amount of stripping steam. However, despite the potential advantages of HFMC, very few investigations have studied implementing this technology for PCC within an industrial framework. To fill this lack, the performances of both absorption and stripping steps using HFMC under industrial conditions were estimated by modelling and simulation. To identify the optimal modelling strategy, transfer models with different levels of complexity were developed ranging from one-dimensional isothermal single-component to two-dimensional adiabatic multi-component. Simulation results of both absorption and stripping steps revealed that, compared to traditional packed columns, contactor volume reduction factors comprised between 4 and 10 might be achieved using HFMC. However, since the stripping operating conditions are very close to thermodynamic equilibrium, HFMC can hardly reduce the energy consumption of the process

Commercial pure terephthalic acid (PTA) manufacturing generates process streams mainly containing acetic acid (HAc) and water. A large financial incentive exists to replace the costly and energy intensive distillation column used to recycle HAc-water mixtures. This work focuses on the development of pervaporation technology to separate HAc-water mixtures using a hollow fiber-based membrane unit. Currently a 250 m outer diameter Matrimid® hollow fiber is used in industry for gas separation. Due to the difference between gas and liquid separations, the fiber performance associated with high flux in pervaporation is limited by a pressure change inside the bore along the axial direction of the fiber. A mathematical model was developed to describe the bore pressure change in pervaporation in this work, which demonstrated that spinning a large bore size fiber was a good solution to minimize the bore pressure change. Spinning technology has been adapted to obtain a large bore size defect-free Matrimid® hollow fiber. In addition to a large bore size, the asymmetric fiber exhibits an intrinsically defect-free selective layer supported on an open porous substrate. This eliminates the post-treatment with a caulking layer and has a special advantage for aggressive liquid separation. A proof of concept was provided by testing both small and large bore size defect-free fibers with a model 20% wt HAc feed in a pervaporation system at 101.5oC. The membrane selectivity (~ 25) and water flux (~ 4.5 kg/m2hr) were increased by about 150% with a diameter (O.D. ~ 500 m) twice as large as the regular fiber. Further, a decrease in the HAc flux was observed with the increased bore size due to the reduction in HAc-induced plasticization. Sub-Tg thermal annealing was used to stabilize the fiber by suppressing HAc-induced plasticization. This improves the polymer discrimination of shape and size for penetrants although no chemical reaction occurs with thermal annealing. The resulting membrane selectivity was increased from 10 to about 95 using a large bore size defect-free annealed fiber with acceptable water flux (~ 1.5 kg/m2hr) for 20% wt HAc concentration feed streams. These improvements make Matrimid® hollow fiber membranes very attractive for future scale-up and commercial development.

Mixed matrix hollow fiber membranes maintain the ease of processing polymers while enhancing the separation performance of the pure polymer due to inclusion of molecular sieve filler particles. This work shows the development process of high loading mixed matrix hollow fiber membranes for butane isomer separation, from material selection and engineering of polymer-sieve interfacial adhesion to mixed matrix hollow fiber spinning. The matching of gas transport properties in polymer and zeolite is critical for forming successful mixed matrix membranes. The nC4 permeability in glassy commercial polymers such as Ultem® and Matrimid® is too low (< 0.1 Barrer) for commercial application. A group of fluorinated (6FDA) polyimides, with high nC4 permeability and nC4/iC4 selectivity, are selected as the polymer matrix. No glassy polymers can possibly match the high permeable MFI to make mixed matrix membranes with selectivity enhancement for C4s separation. Zeolite 5A, which has a nC4 permeability (~3 Barrer) and nC4/iC4 selectivity (essentially ∞), matches well with the 6FDA polymers. A 24% nC4/iC4 selectivity enhancement was achieved in mixed matrix membranes containing 6FDA-DAM and 25 wt% treated 5A particles. A more promising mixed matrix membrane contains 6FDA-DAM-DABA matrix and 5A, because of a better match of gas transport properties in polymer and zeolite. Dual layer hollow fibers, with cellulose acetate core layer and sheath layers of 6FDA polyimides, were successfully fabricated. Successive engineering of the 6FDA sheath layer and the dense skin is needed for the challenging C4s separation, which is extremely sensitive to the integrity of the dense skin layer. The delamination-free, macrovoid-free dual layer hollow fiber membranes provide the solution for the expensive 6FDA polyimides spinning. Mixed matrix hollow fiber membranes are spun base on the platform of 6FDA/Cellulose acetate dual layer hollow fibers. Preliminary results suggest that high loading mixed matrix hollow fiber membranes for C4s is feasible. Following research is needed on the fiber spinning with well treated zeolite 5A nanoparticles. The key aspect of this research is elucidating the three-step (sol-gel-precipitation) mechanism of sol-gel-Grignard treatment, based on which further controlling of Mg(OH)2 whisker morphologies is possible. A Mg(OH)2 nucleation process promoted by acid species is proposed to explain the heterogeneous Mg(OH)2 growing process. Different acid species were tried: 1) HCl solution, 2) AlClx species generated by dealumination process and 3) AlCl3 supported on zeolite surfaces. Acids introduced through HCl solution and dealumination are effective on commercial 5A particles to generate Mg(OH)2 whiskers in the sol-gel-Grignard treatment. Supported AlCl3 is effective on both commercial and synthesized 5A particles (150 nm-1 µm) during the sol-gel-Grignard treatment, in terms of promoting heterogeneous Mg(OH)2 whiskers formation. But the byproduct of Al(OH)3 layer separates the Mg(OH)2 whiskers from zeolite surface, and leads to undesirable morphologies for polymer-zeolite interfacial adhesion. The elucidation of sol-gel-Grignard mechanism and importance of zeolite surface acidity on Mg(OH)2 formation, builds a solid foundation for future development towards ''universal'' method of growing Mg(OH)2 whiskers on zeolite surfaces.