Zugl.: Hamburg, Techn. Univ., Diss., 2007

Thèse (Ph.D.)--Université Laval, 2004. / Titre de l'écran-titre (visionné le 29 novembre 2004). Bibliogr.

Thèse (M.Sc.)--Université Laval, 2004. / Titre de l'écran-titre (visionné le 18 janvier 2005). Bibliogr.

>Magister Scientiae - MSc / Over the last decade polysulfone membranes have been demonstrated to be one of the best membrane types in wastewater treatment, especially in ultrafiltration, owing to its mechanical robustness, structural and chemical stability. Regrettably these membranes are mostly hydrophobic by nature and therefore highly vulnerable to fouling due to chemosorptive mechanisms. Fouling may be caused by cake formation on the surface of the membrane or by surface assimilation of the foulants. Many studies have been directed at improving hydrophilic properties of polysulfone membranes by introducing different types of nanoparticle composite such as TiO2, ZnO2, Au and Ag nanoparticles to the polymer matrix, in order to reduce fouling potential and increase membrane performance. In the present investigation a hydrogel material was developed by crosslinking polyvinyl alcohol (PVA) with polysulfone (PSF), using glutaraldehyde as crosslinker. PVA has excellent film formation, emulsifying and adhesive properties, it is highly flexible and has high tensile strength. Introducing PVA into the PSF polymer matrix was expected to impart its advantageous properties onto the resulting membrane and enhance hydrophilic characteristics of the membrane. The cross linking of PVA and PSF was controlled at three different ratios to evaluate the effect of the PSF contribution i.e. 25:75, 50:50 and 75:25. The crosslinked polymer composites produced three unique hydrogel materials, which were evaluated for the separation of selected small organic molecules, under hydrodynamic conditions, using rotating disk electrochemistry. The hydrogel thin film behaved as a chemical sensor for the oxidation of tannic acid in aqueous solution, with negligible shift in peak potential as a function of concentration. The nanomaterials prepared were characterised using spectroscopic, morphological and electrochemical techniques. Hydrogel performance in the presence of analyte molecule was evaluated by hydrodynamic voltammetry and electrochemical impedance spectroscopy. From calibration curves based on cyclic voltammetry, hydrodynamic, macroscopic and spectroscopic techniques, the 75% polysulfone and 25 % polyvinyl alcohol hydrogel (75:25 PSF-PVA) presented the best performance for quantitative detection and best sensitivity toward alginic acid and tannic acid than the corresponding composites (50:50 and 25:75 PSF-PVA). Optical results (contact angle) show an agreement with spectroscopic (EC) and microscopic (AFM) result. A decrease in contact angle gives an increase in roughness and diffusion coefficient. High surface roughness was linked to improved hydrophilicity of the polysulfone.

Epoxy nanofiltration membranes were synthesized using a diamine and a diepoxide in a one-pot step polymerization. These membranes were stable in organic solvents and used for chemical separations in dichloromethane. The epoxy membranes showed excellent selectivities in chemical separations of over 100:1. The selectivity of the membrane was optimized by adding in a triepoxide to the polymerization to increase the cross-link density. Optimization of the membranes increased the selectivity up to 250:1 for select chemical separations. These epoxy membranes are some of the first nanofiltration membranes used in the separation of important fatty acids such as omega-3 fish oil fatty acid ethyl esters, and saturated fatty acid methyl esters. The epoxy membranes can separate eicosahexaenoic acid ethyl ester from docosahexenoic acid ethyl ester with selectivities up to 1.4:1. The selectivity of saturated fatty acid methyl esters with epoxy membranes were as high as 100:1 for the separation of methyl butyrate from methyl stearate. Epoxy membranes are also the first stimulus-responsive membranes with a disulfide-bond dependent mechanism. The labile disulfide bond is cleaved upon exposure to a chemical stimulus, which cleaves the cross-links within the membrane, and increases the pore size. The flux and selectivity of chemicals through the membrane was controlled before and after exposure to a chemical stimulus. The membranes were implemented in a multicomponent chemical separation to produce three-purity enriched fractions from a three-component mixture. The purity of chemicals improved from 33% up to 82%, with recovery yields as high as 88%.

Charles University, Faculty of Pharmacy in Hradec Králové, Department of Pharmaceutical Chemistry and Pharmaceutical Analysis Nanofiltration Diploma thesis Candidate: Hana Heidrová Supervisor: doc. PharmDr. Radim Kučera, Ph.D. Consultant: PharmDr. Tomáš Holas, Ph.D. Nanofiltration is a pressure-driven membrane process which is characterized by using semipermeable membranes with approximately 1 nm pores. This method is used abundantly for the separation of substances with low molecular weight. It is used for example in the process of product isolation in pharmaceutical industry. This diploma thesis is focused on the description of the behaviour of three commercially produced nanofiltration membranes and also on testing of their potential use in the production of ergot alkaloids. The theoretical part is focused especially on the description of pressure-driven membrane processes, the use of nanofiltration in various areas and also on current and historical use of ergot alkaloids in therapy and on the description of their properties. The practical part is oriented particularly on examination of effect of various experimental parameters on the retention of selected ergot alkaloids (primarily of lysergic and isolysergic acid). The results are compared and critically analysed. Keywords: pressure-driven...

Industrial wastewater treatment using conventional treatment technologies is becoming challenging day-by-day due to presence of ‘newer’ refractory compounds, lower treatment efficiencies and stricter environmental laws. Combination of conventional treatment techniques with modern treatment technologies like membrane filtration or advanced oxidation processes (AOPs) has shown promise in achieving high efficiencies. In this work we have worked towards development of a membrane nanofiltration unit to treat coagulation-flocculation pretreated IWW from a specialized treatment facility. More specifically, state-of-the-art TiO2 ceramic NF membranes with low molecular weight cut off (MWCO) (200, 450, 750, 8500 Da) purchased from Inopor Gmbh were tested on 6 different IWW samples due to their superior chemical stability, higher flux and high fouling resistance along with 3 commercial polymer NF membranes (NF90, NFX, NFS) for comparison purposes. Additionally, wastewater characterization dataset including composition analysis using Gas-chromatography Mass-spectroscopy (GC-MS) is leveraged to build data driven models for membrane performance prediction. ‘200 Da’ ceramic NF membrane was able to reject significant COD with an average rejection of 77% and 60% for two IWW samples with permeate flux between 5-15 LMH at 100-120 psi trans-membrane pressure (TMP). ‘200-Da’ membrane was also found to achieve more flux than ‘450 Da’ membrane while rejecting more COD at the same time. ‘200 Da’ membrane also showed lower flux decline than polymer membranes. Additionally, the ceramic NF membranes were found to be easily chemically cleanable restoring wastewater flux after fouling. Since polymer NF membranes were found to reject at higher COD rejection efficiencies (60-90%) and permeate flux, further improvement in ceramic membranes is needed to treat at higher efficiencies. 200 Da, NF90 and NFX membranes were found to be promising to reduce COD below target (600 mg/L) and should be studied further for this application. / Thesis / Master of Applied Science (MASc) / Conventional technologies for Industrial wastewater (IWW) treatment include biological treatment, coagulation, flocculation, adsorption and filtration. Many industries produce IWW with high concentration of biologically toxic organics ruling out the option of biological treatment. Moreover, with stricter regulatory laws in place for effluent discharge, adoption of new treatment technologies is needed. Nanofiltration (NF) is one such treatment technology that has seen a lot of growth in the past decade since its advent in 1980s. Polymer nanofiltration has been successfully used in applications such as dye removal in textile industry, as a pre-treatment method in desalination plants, for organic solvent nanofiltration in pharmaceutical industry and many more. More recent development of ceramic nanofiltration membranes has seen a lot of interest from researchers around the world due to their superior physical and chemical robustness, fouling resistant properties and higher permeability as compared to polymer NF membranes, though only a small amount of ceramic NF membranes are applied in industrial projects. To this end, we have conducted laboratory scale testing of 4 state of the art ceramic NF membranes on multiple real industrial wastewater samples collected from a specialized IWW treatment plant, along with 3 polymer NF membranes for comparison purposes. Additionally, a data-driven modeling approach leveraging the wastewater composition dataset is shown. The models can be used to predict % rejection of an unseen compound based on its chemical properties and provide insights into complex interactions between compounds and the membrane.

La part des technologies membranaires en tant que technique de séparation a rapidement augmenté au cours de ces dernières années grâce à leur large gamme d'applications. Le marché en pleine expansion nécessite des matériaux polymères avancés qui montrent une résistance accrue vis-à-vis du gonflement et de la plastification en séparation de gaz (GS) ou vis-à-vis de solvants forts et des conditions de pH extrême en nanofiltration en milieu organique (SRNF). Aujourd'hui, la réticulation apparait comme une technologie prometteuse pour répondre à ces nouveaux besoins. La réticulation chimique est l'une des techniques les plus couramment utilisées et est basée sur une réaction chimique entre un polymère (par exemple un polyimide) et un réticulant (par exemple une diamine ou un diol). Cependant pour des polymères, tels que les polysulfones (PSU), qui ne contiennent pas de groupes fonctionnels chimiquement réactifs dans leur squelette, cette technique n'est pas viable. Enfin la réticulation chimique implique plusieurs étapes de traitement et induit des flux de déchets nocifs. La recherche d'une technique de traitement rapide et verte généralement applicable est donc d'une première importance. Deux nouvelles techniques de réticulation, que sont les traitements par rayons ultraviolets (UV) pour par faisceaux d'électrons (EB), ont donc été explorées dans cette thèse afin d'obtenir des membranes stables chimiquement et thermiquement, ce qui est intéressant pour les applications SRNF. Des membranes asymétriques, composées d'un réseau polymère semi-interpénétrant (SIPN), ont été préparées par séparation de phase induite par un solvant (NIPS). Le PSU a été choisi comme polymère grâce à ses caractéristiques intrinsèques suivantes : propriétés thermiques et mécaniques importante, photosensibilité et absence de groupes réactifs. Les membranes réticulées à structure SIPN ont été obtenues par traitement UV et EB. Ces techniques possèdent plusieurs avantages par rapport à la réticulation chimique : une réduction de la production de déchets, des besoins énergétiques plus faibles et des temps de traitement rapides. Dans une première partie, nous avons étudié l'influence de la fonctionnalité du réticulant, de l'énergie du rayonnement et du rapport polymère / réticulant sur l'efficacité de la réticulation par EB. Des agents de réticulation à base d'acrylate ont été utilisés. Les membranes obtenues ont été caractérisées par des expériences en ATR-FTIR, SEM et de filtration, ainsi que des essais de stabilité contre des solvants forts. Le meilleur type de réticulant et sa concentration optimale sous une dose d'EB optimale ont ensuite été sélectionnés pour les études suivantes. Dans la seconde partie, nous avons exploré les effets du rapport solvant / co-solvant et du temps d'évaporation avant la précipitation des membranes en PSU réticulées par la suite soit par UV et soit par EB; le tétrahydrofurane (THF) ou le 1,4-dioxane (DIO) étant utilisés comme solvant. Dans les deux cas, les morphologies membranaires différent en fonction des paramètres étudiés de l'inversion de phase. L'augmentation du temps d'évaporation réduit la formation de macrovides et permet l'apparition de structures spongieuses. Les flux de solvant sont généralement restés trop faible pour que les membranes soient vraiment utiles en SRNF. Un post-traitement a été effectué pour augmenter le flux en immergeant les membranes réticulées dans du dimethylformamide (DMF) pendant 48 h. Les membranes résultantes ont des perméances plus élevées et des taux de rejets plus faibles. / The importance of membrane technology as a separation technique has increased rapidly over the past decades thanks to its broad range of applications. The expanding market brings along the requirement of advanced polymeric materials, which show resistance towards swelling and plasticization in gas separation (GS) and towards harsh solvents and extreme pH conditions in solvent resistant nanofiltration (SRNF). At this stage, cross-linking has emerged as a promising technology to overcome these issues. Chemical cross- linking is one of the most commonly used techniques and is based on a chemical reaction between a polymer (e.g. polyimide) and a cross-linker (e.g. diamine or diol). However, for polymers which do not contain chemically reactive groups in their backbone, such as polysulfones (PSU), this technique is not feasible. Additionally, chemical cross-linking involves several processing steps and causes harmful waste streams, triggering the quest for a generally applicable, fast and green curing technique. Two new curing techniques, namely ultraviolet (UV) and electron beam (EB) curing, were explored in this thesis, in order to obtain chemically and thermally stable membranes, hence being attractive for SRNF applications. Asymmetric membranes, composed of a semi-interpenetrating polymer network (SIPN), were prepared via non-solvent induced phase separation (NIPS). PSU was chosen as polymer because of its robust thermal and mechanical properties, photosensitivity and lack of reactive groups. Cross-linked membranes with SIPN structure were obtained via UV and EB-curing. In the first part, the influence of cross-linker functionality, radiation energy dose and polymer/crosslinker ratio on the EB-curing efficiency was investigated. Acrylate-based cross-linkers were employed. The obtained membranes were characterized with ATR-FTIR, SEM and filtration experiments, together with stability testing against harsh solvents. The best type of cross-linker and its optimum concentration under optimum EB-dose were then selected for further studies. In the second part, the effects of solvent/co-solvent ratio and the evaporation time before precipitation of UV and EB-cured PSU SRNF-membranes were explored, using tetrahydrofuran (THF) or 1,4-dioxane (DIO) as co-solvent. Both UV and EB-cured PSU membrane morphologies differed as function of the studied phase inversion parameters. Increasing evaporation time reduced macrovoid formation with appearance of spongy structures. The flux generally remained too low for membranes to become really useful in SRNF. A post treatment was performed to increase the flux by immersing UV-cured PSU-based membranes in dimethylformamide (DMF) for 48 h. The resultant membranes showed higher permeances and lower rejections, making them especially useful as potential candidates as stable supports in the preparation of thin film composite membranes. In a third part, the mechanical characteristics, the effect of casting thickness and the surface properties of the membranes cross-linked by both irradiation methods were further studied. Additionally, the swelling behavior of UV-cured thin PSU films as function of different curing parameters (i.e. radiation dose and cross-linker functionality) was analyzed with ellipsometry. In conclusion, solvent stable asymmetric PSU membranes were developed by two simple, environmentally friendly and highly effective methods. The performance and enhanced chemical resistance of the cured membranes show high potential for implementing both cross-linking procedures in adequate industrial applications after further optimization.

The focus of this dissertation was the development, synthesis and modification of polymers for the preparation of membranes for organic solvent nanofiltration. High chemical stability in a wide range of solvents was a key requirement. Membranes prepared from synthesized polymers as well as from commercial polymers were designed and chemically modified to reach OSN requirements. A solvent stable thin-film composite (TFC) membrane is reported, which is fabricated on crosslinked polythiosemicarbazide (PTSC) as substrate. The membranes exhibited high fluxes towards solvents like THF, DMF and DMSO ranging around 20 L/m2 h at 5 bar with a MWCO of around 1000 g/mol. Ultrafiltration PTSC membranes were prepared by non-solvent induced phase separation and crosslinked with GPTMS. The crosslinking reaction was responsible for the formation of an inorganic-type-network that tuned the membrane pore size. The crosslinked membranes acquired high solvent stability in DMSO, DMF and THF with a MWCO above 1300 g/mol. Reaction Induced Phase Separation (RIPS) was introduced as a new method for the preparation of skinned asymmetric membranes. These membranes have two distinctive layers with different morphologies both from the same polymer. The top dense layer is composed of chemically crosslinked polymer chains while the bottom layer is a porous structure formed by non-crosslinked polymer chains. Such membranes were tested for vitamin B12 in solvents after either crosslinking the support or dissolving the support and fixing the freestanding membrane on alumina. Pebax® 1657 was utilized for the preparation of composite membranes by simple coating. Porous PAN membranes were coated with Pebax® 1657 which was then crosslinked using TDI. Crosslinked Pebax® membranes show high stability towards ethanol, propanol and acetone. The membranes were also stable in DMF once crosslinked PAN supports were used. Sodium alginate polymer was investigated for the preparation of thin film composite membranes. Composite membranes were prepared using PAN and crosslinked PAN supports; these membranes were tested for methanol and DMF. Freestanding nanofilms fixed on alumina were also tested for methanol and DMF as well as many other harsh solvents. The alginate composite membranes showed excellent solvent stability and good permeances and a MWCO of around 1300 g/mol.

Several attempts have been made to combine the unique characteristics of graphene oxide (GO) and commercial polymers for successfully designing and fabricating next-generation membranes in filtration and separation technologies. The first part of the work develops a high flux polyethersulfone ultrafiltration membranes, by embedding GO sheets, starting from the polymer/GO solutions in ionic liquid and N, N dimethylformamide as co-solvents and promoting the pore formation via non-solvent induced phase separation. In the second part of the work, a protic ionic liquid was introduced as a solvent to disperse GO sheets and fabricate GO liquid crystal membranes for nanofiltration. The third part addresses the stability enhancement. GO membranes frequently disintegrate in aqueous environments due to swelling. Ethylenediamine was then used as a crosslinker, and the membranes were tested for organic solvent nanofiltration. Additionally, overcoming the permeation-rejection trade-off is challenging. Hence, the fourth work involved the intercalation of silica nanoparticles to form dual-sized nanochannels. In the final work, GO membranes were fabricated on the surface of hollow fibers to overcome scalability issues, by using a feasible spray coating method for efficient nanofiltration. Hollow fibers were crosslinked with hexamethylene diamine and GO was spray-coated on the crosslinked polymeric fibers for organic solvent nanofiltration. Overall, this study demonstrates the potential of GO in developing high-performance membranes for liquid separations relevant for industrial applications, such as wastewater treatment, food, chemical, petrochemical, and pharmaceutical processing.