Wuppertal, Univ., Diss., 2000. / Computerdatei im Fernzugriff.

Wuppertal, Univ., Diss., 2000. / Computerdatei im Fernzugriff.

Wuppertal, Universiẗat, Diss., 2000.

Membrane technology plays a crucial role in different separation processes such as biotechnology, pharmaceutical, and food industries, drinking water supply, and wastewater treatment. However, there is a growing concern that solvents commonly used for membrane fabrication, such as dimethylformamide (DMF), dimethylacetamide (DMAc), and 1-methyl-2-pyrrolidone (NMP), are toxic to the environment and human health. To explore the possibility of substituting these toxic solvents by less toxic or safer solvents, polymers commonly used for membrane fabrication, such as polyacrylonitrile (PAN), cellulose acetate (CA), polyethersulfone (PES), and poly(ether imide sulfone) (EXTEMTM), were dissolved in ionic liquids. Flat sheet and hollow fiber membranes were then fabricated. The thermodynamics of the polymer solutions, the kinetics of phase inversion and other factors, which resulted in significant differences in the membrane structure, compared to those of membranes fabricated from more toxic solvents, were investigated. Higher water permeance with smaller pores, unique and uniform morphologies, and narrower pore size distribution, were observed in the ionic liquid-based membranes. Furthermore, comparable performance on separation of peptides and proteins with various molecular weights was achieved with the membranes fabricated from ionic liquid solutions. In summary, we propose less hazardous polymer solutions to the environment, which can be used for the membrane fabrication with better performance and more regular morphology.

Neste trabalho, foram adicionadas diferentes concentrações de polianilina (PANI) a uma solução polimérica de poliétersulfona (PES) e N-metil-pirrolidona (NMP), com o intuito de sintetizar membranas de ultrafiltração a partir do método de inversão de fases. O desafio consistem em combinar alta condutividade elétrica, boas propriedades mecânicas e oxidação eletroquímica, permitindo assim que a oxidação de possíveis contaminantes ocorra ao mesmo tempo em que a membrana atua como uma barreira de filtração seletiva. O efeito da adição de PANI foi avaliado quanto à morfologia da membrana, capacidade de separação e desempenho, em termos de permeabilidade e condutividade. As membranas modificadas apresentaram uma morfologia muito singular quando analisadas pelo Microscópio Eletrônico de Varredura (MEV), poros maiores foram identificados, ausência da camada seletiva, diminuição da camada inferior e grandes fases aglomeradas ao longo da seção transversal. Devido ao aumento do tamanho dos poros, a seletividade das membranas modificadas foi comprometida. Os resultados de porosidade para as membranas modificadas variaram entre 53 e 66%. A permeabilidade e a condutividade das membranas modificadas aumentaram à medida que a concentração de PANI também aumentou. O fluxo mediano obtido para a membrana com concentração de 40% de PANI foi de 835 L.m-2.h-1, cerca de 5 vezes maior do que o fluxo mediano obtido para a membrana controle. Já a condutividade mediana obtida para a mesma membrana modificada foi de 1,7x10-6 S, cerca de 15 vezes maior do que a membrana controle. Durante o teste de voltametria cíclica não foram observadas reações de oxidação-redução, nem da solução de ferro-cianeto nem da própria polianilina, ao aplicar uma tensão variando entre -0,2 V e 0,8 V. Desta forma, a partir dos resultados, pode-se afirmar que a adição de Polianilina alterou a morfologia e o desempenho das membranas modificadas, destacando o incremento na permeabilidade, hidrofilicidade e condutividade, mantendo sua característica de ser uma barreira de filtração seletiva. / In this work, different concentrations of Polyaniline (PANI) were added to a polymer solution made of Polyethersulfone (PES) and N-methylpyrrolidone (NMP), in order to synthesize ultrafiltration membranes by the phase inversion method and the challenge of combine high electrical conductivity, good mechanical properties and electrochemical oxidation, thus allowing the oxidation of matter to occur at the same time that the membrane acts as a selective and reliable filtration barrier. The effect of PANI addition was evaluated regarding the membrane morphology, separation capacity and performance in terms of permeability and conductivity. The modified membranes presented a very unique morphology when analyzed by the Scanning Electron Microscope (SEM), larger pores were identified, absence of the selective layer, decrease of the lower layer and large agglomerated phases with phase contour characterization along the cross section. Due to the increase in pore size, the selectivity of the modified membranes was compromised. The porosity results for the modified membranes are only reflections of the morphology obtained, and the median porosities varied between 53 and 66%. The permeability and conductivity of the modified membranes increased as the PANI concentration also increased. The median flow obtained for the membrane with 40% PANI concentration was 835 L.m-2.h-1, about 5 times higher than the median flow obtained for the control membrane. The median conductivity obtained for the same modified membrane was 1.7x10-6 S, about 15 times higher than the control membrane. During the cyclic voltammetry test, no oxidation-reduction reactions were observed, neither the iron-cyanide solution nor the polyaniline itself, when applying a voltage ranging from -0.2 V to 0.8 V. From the results, it can be affirmed that the addition of polyaniline particles altered the morphology and performance of the modified membranes, highlighting the increase in permeability, hydrophilicity and conductivity, maintaining its characteristics of being a selective filtration barrier.

Neste trabalho, foram adicionadas diferentes concentrações de polianilina (PANI) a uma solução polimérica de poliétersulfona (PES) e N-metil-pirrolidona (NMP), com o intuito de sintetizar membranas de ultrafiltração a partir do método de inversão de fases. O desafio consistem em combinar alta condutividade elétrica, boas propriedades mecânicas e oxidação eletroquímica, permitindo assim que a oxidação de possíveis contaminantes ocorra ao mesmo tempo em que a membrana atua como uma barreira de filtração seletiva. O efeito da adição de PANI foi avaliado quanto à morfologia da membrana, capacidade de separação e desempenho, em termos de permeabilidade e condutividade. As membranas modificadas apresentaram uma morfologia muito singular quando analisadas pelo Microscópio Eletrônico de Varredura (MEV), poros maiores foram identificados, ausência da camada seletiva, diminuição da camada inferior e grandes fases aglomeradas ao longo da seção transversal. Devido ao aumento do tamanho dos poros, a seletividade das membranas modificadas foi comprometida. Os resultados de porosidade para as membranas modificadas variaram entre 53 e 66%. A permeabilidade e a condutividade das membranas modificadas aumentaram à medida que a concentração de PANI também aumentou. O fluxo mediano obtido para a membrana com concentração de 40% de PANI foi de 835 L.m-2.h-1, cerca de 5 vezes maior do que o fluxo mediano obtido para a membrana controle. Já a condutividade mediana obtida para a mesma membrana modificada foi de 1,7x10-6 S, cerca de 15 vezes maior do que a membrana controle. Durante o teste de voltametria cíclica não foram observadas reações de oxidação-redução, nem da solução de ferro-cianeto nem da própria polianilina, ao aplicar uma tensão variando entre -0,2 V e 0,8 V. Desta forma, a partir dos resultados, pode-se afirmar que a adição de Polianilina alterou a morfologia e o desempenho das membranas modificadas, destacando o incremento na permeabilidade, hidrofilicidade e condutividade, mantendo sua característica de ser uma barreira de filtração seletiva. / In this work, different concentrations of Polyaniline (PANI) were added to a polymer solution made of Polyethersulfone (PES) and N-methylpyrrolidone (NMP), in order to synthesize ultrafiltration membranes by the phase inversion method and the challenge of combine high electrical conductivity, good mechanical properties and electrochemical oxidation, thus allowing the oxidation of matter to occur at the same time that the membrane acts as a selective and reliable filtration barrier. The effect of PANI addition was evaluated regarding the membrane morphology, separation capacity and performance in terms of permeability and conductivity. The modified membranes presented a very unique morphology when analyzed by the Scanning Electron Microscope (SEM), larger pores were identified, absence of the selective layer, decrease of the lower layer and large agglomerated phases with phase contour characterization along the cross section. Due to the increase in pore size, the selectivity of the modified membranes was compromised. The porosity results for the modified membranes are only reflections of the morphology obtained, and the median porosities varied between 53 and 66%. The permeability and conductivity of the modified membranes increased as the PANI concentration also increased. The median flow obtained for the membrane with 40% PANI concentration was 835 L.m-2.h-1, about 5 times higher than the median flow obtained for the control membrane. The median conductivity obtained for the same modified membrane was 1.7x10-6 S, about 15 times higher than the control membrane. During the cyclic voltammetry test, no oxidation-reduction reactions were observed, neither the iron-cyanide solution nor the polyaniline itself, when applying a voltage ranging from -0.2 V to 0.8 V. From the results, it can be affirmed that the addition of polyaniline particles altered the morphology and performance of the modified membranes, highlighting the increase in permeability, hydrophilicity and conductivity, maintaining its characteristics of being a selective filtration barrier.

This thesis explores the application of passive sampling as a novel monitoring technique capable of quantifying aquatic pollutants at low environmental concentrations, and in a form that is directly applicable to risk assessment. Two passive samplers, namely polyethersulfone (PES) and silicone rubber (SR), were used to monitor some endocrine disruptors (EDCs) and hydrophobic organic chemicals (HOCs) in freshwater and sediments of a tropical river in Kenya. PES was applied for the first time for time-integrative sampling of these compound classes and was able to quantify the target compounds at low concentrations that were not significantly different to those obtained using the well-established SR, despite differences in uptake mechanisms with both sampler materials. This study demonstrated that passive samplers are versatile tools that can be applied in remote locations, and with proper storage, they can be transported and analyzed far afield.

Mixed matrix membranes (MMM) offer one potential path toward exceeding the Robeson upper bound of selectivity versus permeability for gas separation performance while maintaining the benefits of solution processing. Many inorganic materials, such as zeolites, metal-organic frameworks, or carbon nanotubes, can function as molecular sieves, but as stand-alone membranes are brittle and difficult to manufacture. Incorporating them into a more robust polymeric membrane matrix has the potential to mitigate this issue. In this work, phase inversion polymer solution processing for the fabrication and testing of asymmetric flat sheet mixed matrix membranes was employed with CVD-derived multiwall carbon nanotubes (MWCNTs) dispersed in a polyethersulfone (PES) matrix. The effect of MWCNT loading on membrane separation performance was examined. Notably, a distinct enhancement in selectivity was measured for several gas pairs (including O2/N2) at relatively low MWCNT loading, with a peak in selectivity observed at 0.1 wt% loading relative to PES. In addition, no post-treatment (e.g. PDMS caulking) was required to achieve selectivity in these membranes. In contrast, neat PES membranes and those containing greater than 0.5 wt.% MWCNT showed gas selectivity characteristic of Knudsen diffusion through pinhole defects. These results suggested that at low loading, the presence of MWCNTs suppressed the formation of surface defects in the selective layer in flat sheet mixed matrix membranes. Additionally, a bench-scale, single-filament hollow fiber membrane spinning line was designed and purpose-built at the University of Kentucky Center for Applied Energy Research (CAER). Hollow fiber membrane spinning capability was developed using polyethersulfone (PES) solution dopes, and the process was expanded to include polysulfone (PSf) as well as mixed matrix membranes. The effects of key processing parameters, including the ratio of bore to dope velocities, the spinning air gap length, and the draw-down ratio, were systematically investigated. Finally, direct hollow fiber analogues to flat sheet mixed matrix membranes were characterized. Consistent with the flat sheet experiments, the mixed matrix hollow fiber membranes showed a local maximum in selectivity at a nominal loading of 0.1 wt.% MWCNT relative to the polymer, suggesting that the pinhole suppression effect introduced by MWCNTs was not limited to flat sheet membrane casting. The development of asymmetric hollow fiber mixed matrix membrane processing and testing capability at the UK Center for Applied Energy Research provides a platform for the further development of gas separation membranes. Using the tools developed through this work, it is possible to further push the frontiers of mixed matrix gas separation by expanding the capability to include more polymers, inorganic fillers, and post treatment processes which previously have been focused primarily on the flat sheet membrane geometry.

Membrane based separation techniques have been widely used and developed over decades. Generally polymeric membranes are used in membrane based gas separation / however their gas separation performances are not sufficient enough for industrial feasibility. On the other hand inorganic membranes have good separation performance but they have processing difficulties. As a consequence mixed matrix membranes (MMMs) which comprise of inorganic particles dispersed in organic matrices are developed. Moreover, to enhance the interaction between polymer and zeolite particles ternary mixed matrix membranes are introduced by using low molecular weight additives as third component and promising results were obtained at 35 &deg / C. Better understanding on gas transport mechanism of these membranes could be achieved by studying the effect of preparation and operating parameters. This study investigates the effect of operation temperature and annealing time and temperature on gas separation performance of MMMs. The membranes used in this study consist of glassy polyethersulfone (PES) polymer, SAPO-34 particles and 2- v hidroxy 5-methyl aniline (HMA) as compatibilizer. The membranes fabricated in previous study were used and some membranes were used as synthesized while post annealing (at 120&deg / C, 0.2atm, N2 atm, 7-30 days) applied to some membranes before they are tested. The temperature dependent gas transport properties of the membranes were characterized by single gas permeation measurements of H2, CO2, and CH4 gases between 35 &deg / C-120 &deg / C. The membranes also characterized by scanning electron microscopy (SEM), thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). Annealing time and temperature affected the reproducibility and stability of the mixed matrix membranes and by applying post annealing step to mixed matrix membranes at higher temperatures and longer times, more stable membranes were obtained. For pure PES membranes thermally stable performances were obtained without any need of extra treatment. The permeabilities of all studied gases increased with increasing operation temperature. Also the selectivities of H2/CO2 were increased while CO2/CH4, H2/CH4 selectivities were decreased with temperature. The best separation performance belongs to PES/SAPO-34/HMA mixed matrix membrane at each temperature. When the temperature increased from 35 &deg / C to 120 &deg / C H2/CO2 selectivity for PES/SAPO- 34/HMA membrane was increased from 3.2 to 4.6 and H2 permeability increased from 8 Barrer to 26.50 Barrer. This results show that for H2/CO2 separation working at higher temperatures will be more advantageous. The activation energies were found in the order of / CH4 &gt / H2&gt / CO2 for all types of membranes. Activation energies were in the same order of magnitude for all membranes but the PES/SAPO-34 membrane activation energies were slightly lower than PES membrane. Furthermore, PES/SAPO-34/HMA membrane has activation energies higher than PES/SAPO-34 membrane and is very close to pure membrane which shows that HMA acts as a compatibilizer between two phases.

Os processos de separação com membranas estão presentes nas mais diversas aplicações industriais. Em especial, a microfiltração e a ultrafiltração vêm sendo extensivamente utilizadas no tratamento de água e de efluentes. Com o aumento da demanda, muitos estudos têm sido feitos para melhorar o desempenho dos processos com membranas, porém a escolha apropriada da membrana é um fator crucial para atingir esse objetivo. As membranas à base de polietersulfona (PES) estão entre as mais utilizadas industrialmente para esse tipo de aplicação devido às suas excelentes propriedades mecânicas, estabilidade térmica e resistência química. No entanto, por serem pouco hidrofílicas, essas membranas apresentam baixos fluxos de água e elevada tendência ao fouling e ao biofouling. A fim de melhorar essas propriedades, muitos autores têm proposto modificações nas membranas para torná-las mais hidrofílicas e, portanto, aumentar o fluxo de água e diminuir o fouling. Dentro desse contexto, o presente trabalho teve como objetivo preparar membranas de ultrafiltração de PES, utilizando a ftaloil-quitosana (FQ) como aditivo, a fim de se obter membranas com propriedade antifouling. Membranas de PES e PES/FQ foram preparadas pelo processo de inversão de fases e caracterizadas quanto à morfologia, à estrutura química, à estabilidade térmica, ao caráter hidrofílico, à permeância hidráulica, à massa molar de corte (MMC) e ao desempenho em ultrafiltração de solução proteica. As membranas modificadas com o aditivo apresentaram estrutura mais heterogênea e com macrovazios maiores, maior caráter hidrofílico e maior permeância hidráulica. Os resultados de MMC não foram conclusivos. No teste de ultrafiltração, essas membranas apresentaram maiores fluxos e menor tendência ao fouling, indicando que o aditivo utilizado foi adequado na melhoria das propriedades desejadas. A retenção proteica, a perda de fluxo e a recuperação de fluxo após limpezas não apresentaram diferenças significativas. / In recent years, membrane separation processes have been widely used in all kinds of industries and applications. Particularly microfiltration and ultrafiltration have been extensively used for drinking water and wastewater treatments. With the increasing demand, many efforts have been done in order to enhance the process performance, but the choice of the appropriate membrane is a crucial factor to achieve this goal. Polyethersulfone (PES) based membranes are among the most commonly used for such applications due to their excellent chemical resistance, thermal stability and mechanical properties. However, because of its low hydrophilicity, these membranes have low water flux and high fouling and biofouling tendency. In order to improve these properties, many authors have proposed membrane modifications to make them more hydrophilic and thus increase the water flux and reduce fouling. Within this context, this work aimed to prepare PES ultrafiltration membranes using phthaloyl-chitosan (FQ) as an additive in order to obtain membranes with antifouling property. PES and PES/FQ membranes were prepared by phase inversion process and their morphology, chemical structure, thermal stability, hydrophilicity, hydraulic permeance, molecular weight cutoff (MWCO) and performance in ultrafiltration of protein solution were characterized. The membranes modified with additives showed more heterogeneous structure with larger macrovoids, higher hydrophilicity and higher hydraulic permeance. The MWCO results were inconclusive. In the ultrafiltration test, these membranes exhibited higher fluxes and lower fouling tendency, indicating that the additive used was adequate in improving the desired properties. The protein retention, flux reduction and flux recovery after cleaning showed no significant differences.