Membrane structure modification is a common approach to enhance membrane properties and performance. For example, the addition of dopants to the membrane casting solution has been observed to increase hydrophilicity, alter surface and internal pore structure, increase thermal and mechanical resistance, and impart anti-fouling properties. In this study, it was evaluated how the addition of individual and simultaneous nanoclay and polyethylene oxide (PEO) dopants affected the structure and performance of polysulfone (PSU) ultrafiltration membranes. Membrane performance was evaluated in the cross-flow configuration. The pure water permeability of the neat PSU membrane was 15 L/m².h.bar and at the optimal dosage of the individually doped membranes was 1.5% weight nanoclay to PSU and 5% weight PEO to PSU resulting in permeability of 56 and 237 L/m².h.bar, respectively. Simultaneous doping using the optimal individual weight percentages had a lower effect resulting in a permeability of 192 L/m².h.bar, in contrast the simultaneous addition of 4.5% nanoclay and 5% PEO had a higher effect resulting in a permeability of 319 L/m².h.bar. The control membrane was compared to the referred membranes and with the 4.5% nanoclay membrane (best permeability only when combined with PEO). These membranes were further examined to determine dopant effects on pore microstructure, superficial charge, separation performance, and fouling susceptibility. In general, doping with nanoclay improved membrane thermal/mechanical resistance and permeability with minimal loss in rejection. Doping with PEO resulted in a greater permeability as compared to nanoclay; however, PEO doping decreased rejection, mechanical resistance, and increased irreversible fouling. Thus, both advantageous and disadvantageous effects should be considered when selecting a dopant to optimize membrane performance. / A modificação da estrutura de membranas é uma abordagem utilizada para melhorar as propriedades de membranas e desempenho de um sistema. Por exemplo, a adição de dopantes na solução de síntese da membrana permite aumentar a hidrofilicidade, alterar a estrutura de poros superficiais e internos e conferir propriedades anti-depósitos. Neste estudo, foi avaliada como a adição de óxido de polietileno e de nano-argila afetam a estrutura e desempenho de membranas de ultrafiltração de polisulfona (PSU). O desempenho da membrana foi avaliado na configuração de fluxo paralelo (cross-flow). A permeabilidade média à água pura da membrana de PSU pura foi de 15 L/m2.h.bar. As dosagem ótimas das membranas dopadas individualmente foram de 1,5% em massa de PSU para nano-argila e 5% em massa de PSU para PEO, resultando em permeabilidades médias de 56 e 237 L/m2.h.bar, respectivamente. A dopagem simultânea usando ambas as percentagens individuais ótimas teve um efeito menor do que o esperado, resultando em uma permeabilidade média de 192 L/m2.h.bar. Em contraste, verificou-se que a adição simultânea de 4,5% de nano-argila combinada com 5% de PEO teve um efeito maior do que o uso isolado dos aditivos, resultando em uma permeabilidade média de 319 L/m2.h.bar. Desta forma, a membrana de controle foi comparada com as referidas membranas e com membranas compostas somente por nano-argila a 4,5. Estas membranas foram ainda examinadas em detalhes para determinar os efeitos dos dopantes na microestrutura dos poros, cargas superficiais, desempenho da separação, sensibilidade à formação de depósitos, rugosidade superficial e propriedades térmicas e mecânicas. Verificou-se que a dopagem com nano-argila melhora a resistência térmica e mecânica e a permeabilidade das membranas, com uma perda mínima na rejeição. A dopagem com PEO resultou em um aumento notável de permeabilidade em comparação com a adição individual de nano-argila. No entanto, a capacidade de rejeição e resistência térmica e mecânica destas membranas diminuem e a formação de depósitos irreversíveis aumenta. Desta forma, avalia-se que para a utilização de mais de um tipo de dopante os efeitos vantajosos e desvantajosos devem ser considerados individualmente e em conjunto no esforço de se otimizar o desempenho de sistemas de membranas.

Membrane structure modification is a common approach to enhance membrane properties and performance. For example, the addition of dopants to the membrane casting solution has been observed to increase hydrophilicity, alter surface and internal pore structure, increase thermal and mechanical resistance, and impart anti-fouling properties. In this study, it was evaluated how the addition of individual and simultaneous nanoclay and polyethylene oxide (PEO) dopants affected the structure and performance of polysulfone (PSU) ultrafiltration membranes. Membrane performance was evaluated in the cross-flow configuration. The pure water permeability of the neat PSU membrane was 15 L/m².h.bar and at the optimal dosage of the individually doped membranes was 1.5% weight nanoclay to PSU and 5% weight PEO to PSU resulting in permeability of 56 and 237 L/m².h.bar, respectively. Simultaneous doping using the optimal individual weight percentages had a lower effect resulting in a permeability of 192 L/m².h.bar, in contrast the simultaneous addition of 4.5% nanoclay and 5% PEO had a higher effect resulting in a permeability of 319 L/m².h.bar. The control membrane was compared to the referred membranes and with the 4.5% nanoclay membrane (best permeability only when combined with PEO). These membranes were further examined to determine dopant effects on pore microstructure, superficial charge, separation performance, and fouling susceptibility. In general, doping with nanoclay improved membrane thermal/mechanical resistance and permeability with minimal loss in rejection. Doping with PEO resulted in a greater permeability as compared to nanoclay; however, PEO doping decreased rejection, mechanical resistance, and increased irreversible fouling. Thus, both advantageous and disadvantageous effects should be considered when selecting a dopant to optimize membrane performance. / A modificação da estrutura de membranas é uma abordagem utilizada para melhorar as propriedades de membranas e desempenho de um sistema. Por exemplo, a adição de dopantes na solução de síntese da membrana permite aumentar a hidrofilicidade, alterar a estrutura de poros superficiais e internos e conferir propriedades anti-depósitos. Neste estudo, foi avaliada como a adição de óxido de polietileno e de nano-argila afetam a estrutura e desempenho de membranas de ultrafiltração de polisulfona (PSU). O desempenho da membrana foi avaliado na configuração de fluxo paralelo (cross-flow). A permeabilidade média à água pura da membrana de PSU pura foi de 15 L/m2.h.bar. As dosagem ótimas das membranas dopadas individualmente foram de 1,5% em massa de PSU para nano-argila e 5% em massa de PSU para PEO, resultando em permeabilidades médias de 56 e 237 L/m2.h.bar, respectivamente. A dopagem simultânea usando ambas as percentagens individuais ótimas teve um efeito menor do que o esperado, resultando em uma permeabilidade média de 192 L/m2.h.bar. Em contraste, verificou-se que a adição simultânea de 4,5% de nano-argila combinada com 5% de PEO teve um efeito maior do que o uso isolado dos aditivos, resultando em uma permeabilidade média de 319 L/m2.h.bar. Desta forma, a membrana de controle foi comparada com as referidas membranas e com membranas compostas somente por nano-argila a 4,5. Estas membranas foram ainda examinadas em detalhes para determinar os efeitos dos dopantes na microestrutura dos poros, cargas superficiais, desempenho da separação, sensibilidade à formação de depósitos, rugosidade superficial e propriedades térmicas e mecânicas. Verificou-se que a dopagem com nano-argila melhora a resistência térmica e mecânica e a permeabilidade das membranas, com uma perda mínima na rejeição. A dopagem com PEO resultou em um aumento notável de permeabilidade em comparação com a adição individual de nano-argila. No entanto, a capacidade de rejeição e resistência térmica e mecânica destas membranas diminuem e a formação de depósitos irreversíveis aumenta. Desta forma, avalia-se que para a utilização de mais de um tipo de dopante os efeitos vantajosos e desvantajosos devem ser considerados individualmente e em conjunto no esforço de se otimizar o desempenho de sistemas de membranas.

The proton exchange membrane fuel cell (PEMFC) is a potential electrochemicalpower device for vehicles, auxiliary power units and small-scale power plants. In themembrane electrode assembly (MEA), which is the core of the PEMFC single cell,oxygen in air and hydrogen electrochemically react on separate sides of a membraneand electrical energy is generated. The main challenges of the technology are associatedwith cost and lifetime. To meet these demands, firstly, the component expensesought to be reduced. Secondly, enabling system operation at elevated temperatures,i.e. up to 120 °C, would decrease the complexity of the system and subsequentlyresult in decreased system cost. These aspects and the demand for sufficientlifetime are the strong motives for development of new materials in the field.In this thesis, MEAs based on alternative materials are investigatedwith focus on hydrocarbon proton-conducting polymers, i.e. ionomers, and newcatalyst supports. The materials are evaluated by electrochemical methods, such ascyclic voltammetry, polarisation and impedance measurements; morphological studiesare also undertaken. The choice of ionomers, used in the porous electrodes andmembrane, is crucial in the development of high-performing stable MEAs for dynamicoperating conditions. The MEAs are optimised in terms of electrode compositionand preparation, as these parameters influence the electrode structure andthus the MEA performance. The successfully developed MEAs, based on the hydrocarbonionomer sulfonated polysulfone (sPSU), show promising fuel cell performancein a wide temperature range. Yet, these membranes induce mass-transportlimitations in the electrodes, resulting in deteriorated MEA performance. Further,the structure of the hydrated membranes is examined by nuclear magnetic resonancecryoporometry, revealing a relation between water domain size distributionand mechanical stability of the sPSU membranes. The sPSU electrodes possessproperties similar to those of the Nafion electrode, resulting in high fuel cell performancewhen combined with a high-performing membrane. Also, new catalystsupports are investigated; composite electrodes, in which deposition of platinum(Pt) onto titanium dioxide reduces the direct contact between Pt and carbon, showpromising performance and ex-situ stability. Use of graphitised carbon as catalystsupport improves the electrode stability as revealed by a fuel cell degradation study.The thesis reveals the importance of a precise MEA developmentstrategy, involving a broad methodology for investigating new materials both as integratedMEAs and as separate components. As the MEA components and processesinteract, a holistic approach is required to enable successful design of newMEAs and ultimately development of high-performing low-cost PEMFC systems. / QC 20100922

L’application de la biosorption à l’analyse inorganique est un sujet en plein essor. Dans cette étude, un support à base de cellules de boulanger Saccharomyces cerevisiae a été développé pour la spéciation et la préconcentration des espèces inorganiques de l’antimoine Sb(III) et Sb(V). Nous avons tout d’abord montré qu’il était possible de fixer de manière sélective Sb(III) en présence de Sb(V) sur les cellules dans une large gamme de pH (5-9) et de force ionique (0-0,1M). Un prétraitement thermique de la biomasse (80°C, 30min) permet d’augmenter significativement la cinétique de fixation de Sb(III) sans nuire à la séparation. L’élution de Sb(III) par l’acide thioglycolique à pH 10 est rapide et quantitative, permettant d’obtenir un facteur de préconcentration proche de 9. Nous avons mis en évidence que la rétention de Sb(V) observée à bas pH était due à des complexation avec les groupements sulfhydryle de la paroi cellulaire. La modélisation des isotherme de sorption de Sb(III) (qmax = 450µg.g-1) ont permis de définir 3 types de sites d’affinité et de coordination différentes. Parmi les matrices testées pour l’immobilisation des cellules, le polysulfone s’avère être le plus performant, alliant perméabilité, faible affinité vis-à-vis de l’antimoine et préservation des sites de fixation. Des colonnes remplies de levures immobilisées ont été couplées à un spectromètre ICP-AES et appliquées avec succès à la spéciation de l’antimoine dans l’eau minérale dopée à faible concentration. Les limites de quantification de Sb(III) ont été améliorées d’un facteur 5 par préconcentration / The application of biosorption to inorganic analysis is an expanding research area. In this study, an analytical support based on baker’s yeast Saccharomyces cerevisiae was developed for the speciation and the preconcentration of inorganic antimony species Sb(III) and Sb(V). It was shown that Sb(III) can be retained selectively by the cells in the presence of Sb(V) in a wide range of pH (5-9) and ionic strength (0-0,1M). Heat pretreatment of the biomass (80°C, 30min) significantly increased the kinetics of Sb(III) uptake without degrading the separation. The elution of Sb(III) by thioglycolic acid at pH 10 was rapid and quantitative, allowing to achieve a preconcentration factor close to 9. Interactions between Sb(V) and the cells, as observed at lower pH, were found to be purely electrostatic, while Sb(III) retention was attributed to the complexation of the species with sulfhydryl groups of the cell walls. Three kinds of sites with different affinities and coordinations were identified by modeling Sb(III) sorption isotherms (qmax = 450µg.g-1). Among the different materials tested, polysulfone was found to be the most suitable matrix for yeast immobilization, combining a good permeability to a low affinity for antimony species and preservation of the sorption sites. Columns filled with immobilized cells were coupled with ICP-AES and successfully applied to antimony speciation in mineral waters samples spiked at low concentration level. The limit of quantification was improved by a factor of 5 by preconcentration

The effects of the dialysis membranes, hemodialysis (HD) session, and dialyzer reuse on markers of oxidative stress were studied. Patients with end stage renal disease who have undergone regular HD treatment three times a week were randomized in two study groups according to the type of HD membrane (cellulose acetate membrane (CA) vs. polysulfone membrane (PS)). All the patients participated of the two study groups and used the two different membranes. To analyze the parameters, the blood samples were colleted before and after HD sessions, in the irst use, 6th, 12th reuse of the membranes. The indicator parameters of oxidative stress analyzed were thiobarbituric acid reactive species (TBARS) and dichlorofluorescein reactive species (DRS) levels, carbonyl groups, antioxidant enzyme (catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px)), and non-enzymatic antioxidant (protein (PSH) and non-protein thiol groups (NPSH) and vitamin C). The results demonstrated that there was no significant difference in the markers of oxidative stress between the two membranes used. However, HD session contributed to the increase in TBARS (1st use and the 6th reuse), DRS (6th and 12th reuse), protein (all uses) and NPSH (1st use and 6th reuse) levels, GSH-Px activity (12th reuse) and to the decrease in vitamin C levels (all uses). The dialyzer reuse practice contributed to the increase in the PSH levels, to the decrease in the NPSH levels and to the reduction of the effects of the HD session on the TBARS levels. Therefore, the results obtained from this study revealed that regular HD with CA or PS membranes did not interfere with the oxidative status in the patients. However, HD session may contribute to the increase of oxidative stress and the dialyzer reuse practice appears to be efficient in the reduction of the peroxidation lipidic in these patients / Neste trabalho, foram investigados os efeitos do tipo de membrana de hemodiálise (HD) e da sua reutilização, bem como os efeitos da sessão de HD nos marcadores de estresse oxidativo. Pacientes com insuficiência renal crônica que realizavam HD três vezes por semana foram divididos em dois grupos, de acordo com o tipo de membrana usada (membrana de acetato de celulose (AC) X membrana de polisulfona (PS)). Todos os pacientes participaram dos dois grupos e usaram os dois tipos de membrana. Para análise dos parâmetros, amostras de sangue foram coletadas antes e após a sessão de HD, no 1º uso, 6º e 12º reuso das membranas. Os parâmetros indicadores de estresse oxidativo analisados foram: espécies reativas ao ácido tiobarbitúrico (TBARS), espécies reativas a diclorofluoresceína (DRS), carbonilação de proteínas, antioxidantes enzimáticos (catalase, superóxido dismutase e glutationa peroxidase (GSH-Px)) e antioxidantes não-enzimáticos (grupos tióis protéicos (PSH), grupos tióis não-protéicos (NPSH) e vitamina C). Os resultados demonstraram que não houve diferença significativa nos marcadores do estresse oxidativo entre as duas membranas usadas. Entretanto, houve um aumento dos níveis de TBARS após a sessão de HD (no 1º uso e no 6º reuso), de DRS (6º e 12º reuso), de PSH (em todos os usos), de NPSH (1º uso e 6º reuso), da atividade da GSH-Px (no 12º reuso) e uma diminuição dos níveis de vitamina C após a sessão de HD (em todos os usos). A reutilização das membranas contribuiu para o aumento dos níveis de PSH, para a diminuição dos níveis de NPSH e diminuiu os efeitos da sessão de HD sobre os níveis de TBARS. Portanto, os resultados obtidos neste estudo sugerem que HD com membrana de AC ou de PS não interfere de forma diferente nos marcadores de estresse oxidativo. Entretanto, a sessão de HD pode contribuir para o aumento da geração de estresse oxidativo e a reutilização dos dialisadores parece ser eficiente como forma de redução da peroxidação lipídica nos pacientes em HD

Este trabalho teve por objetivo a preparação e caracterização de membranas de polissulfona (PSU) e a imobilização da enzima lipase nestes filmes, para a produção de membranas enantiosseletivas, visando utilização futura em separação de misturas quirais. Membranas de PSU foram preparadas pelo processo de inversão de fase, utilizando clorofórmio como solvente e água como agente coagulante para a inversão. Foram preparadas membranas com diferentes espessuras e os seguintes parâmetros para a inversão de fase foram definidos: concentração das soluções, tempo de evaporação do solvente, secagem e tratamento térmico. As membranas foram caracterizadas, visando a utilização em processo de eletrodiálise (ED) e imobilização da enzima lipase PS. Para a imobilização foi utilizado o glutaraldeído como agente bifuncional para ligação da enzima ao polímero. Na imobilização foram determinados os parâmetros cinéticos velocidade máxima (Vmáx) e constante de Michaelis-Menten (Km), a quantidade de enzima imobilizada nas membranas pelo método de Bradford e a atividade da enzima livre e imobilizada através da hidrólise do acetato de p-nitrofenila (PNPA). As membranas de PSU preparadas por inversão são hidrofóbicas, e apresentaram características de permesseletividade e capacidade de troca iônica inferiores às apresentadas pelas membranas comerciais Selemion®; CMT e CMV e resistência elétrica superior à destas membranas. O diâmetro dos poros nas membranas é menor que 100 nm. . A quantidade máxima de enzima imobilizada foi de 2,35 mg .g-1 de polímero em 18 horas de imobilização com um rendimento de 61,2%. A atividade da enzima decai após a imobilização, de 14780 U.g-1 (enzima livre) para 1184 U.g-1 (enzima imobilizada). / Submitted by Marcelo Teixeira (mvteixeira@ucs.br) on 2014-05-13T17:21:10Z No. of bitstreams: 1 Dissertacao Jadison Fabricio de Souza.pdf: 3168334 bytes, checksum: ec62af877268ce2e7d357db5c8c5e372 (MD5) / Made available in DSpace on 2014-05-13T17:21:10Z (GMT). No. of bitstreams: 1 Dissertacao Jadison Fabricio de Souza.pdf: 3168334 bytes, checksum: ec62af877268ce2e7d357db5c8c5e372 (MD5) / Preparation and characterization of polysulfone (PSU) membranes and the immobilization of lipase enzyme in these membranes to produce enantioselective membranes, in order to separate chiral compounds, is the subject of the present work. PSU membranes were prepared by phase inversion, using chloroform as solvent and water as nonsolvent. Membranes with different thickness were prepared and phase inversion parameters such as (solution concentrations, solvent evaporation time, drying and thermal treatment) were investigated. Membranes were characterized, in order to use them in electrodialysis process (ED) and in the lipase PS enzyme immobilization. For immobilization, bifunctional agent glutaraldehyde was used to link the enzyme to the polymer. On immobilization, the kinetic constants (Km e Vmax), the amount of immobilized enzyme with Bradford method and the activity of free and immobilized enzyme with p-nitrophenyl acetate (PNPA) hydrolysis, were determined. PSU membranes prepared by phase inversion are hydrophobic and, when compared with Selemion®; CMT and CMV commercial membranes, present lower permeselectivity, lower ion exchange capability and higher resistance. Membranes pore diameter is lower than 100 nm. The maximum amount of immobilized enzyme in the membranes reached 2.35 mg per gram of polymer after 18 hours of immobilization with a 61,2% yield . Enzyme activity decays after immobilization , from 14780 U.g-1 (free enzyme) to 1184 U.g-1 (immobilized enzyme).

Este trabalho teve por objetivo a preparação e caracterização de membranas de polissulfona (PSU) e a imobilização da enzima lipase nestes filmes, para a produção de membranas enantiosseletivas, visando utilização futura em separação de misturas quirais. Membranas de PSU foram preparadas pelo processo de inversão de fase, utilizando clorofórmio como solvente e água como agente coagulante para a inversão. Foram preparadas membranas com diferentes espessuras e os seguintes parâmetros para a inversão de fase foram definidos: concentração das soluções, tempo de evaporação do solvente, secagem e tratamento térmico. As membranas foram caracterizadas, visando a utilização em processo de eletrodiálise (ED) e imobilização da enzima lipase PS. Para a imobilização foi utilizado o glutaraldeído como agente bifuncional para ligação da enzima ao polímero. Na imobilização foram determinados os parâmetros cinéticos velocidade máxima (Vmáx) e constante de Michaelis-Menten (Km), a quantidade de enzima imobilizada nas membranas pelo método de Bradford e a atividade da enzima livre e imobilizada através da hidrólise do acetato de p-nitrofenila (PNPA). As membranas de PSU preparadas por inversão são hidrofóbicas, e apresentaram características de permesseletividade e capacidade de troca iônica inferiores às apresentadas pelas membranas comerciais Selemion®; CMT e CMV e resistência elétrica superior à destas membranas. O diâmetro dos poros nas membranas é menor que 100 nm. . A quantidade máxima de enzima imobilizada foi de 2,35 mg .g-1 de polímero em 18 horas de imobilização com um rendimento de 61,2%. A atividade da enzima decai após a imobilização, de 14780 U.g-1 (enzima livre) para 1184 U.g-1 (enzima imobilizada). / Preparation and characterization of polysulfone (PSU) membranes and the immobilization of lipase enzyme in these membranes to produce enantioselective membranes, in order to separate chiral compounds, is the subject of the present work. PSU membranes were prepared by phase inversion, using chloroform as solvent and water as nonsolvent. Membranes with different thickness were prepared and phase inversion parameters such as (solution concentrations, solvent evaporation time, drying and thermal treatment) were investigated. Membranes were characterized, in order to use them in electrodialysis process (ED) and in the lipase PS enzyme immobilization. For immobilization, bifunctional agent glutaraldehyde was used to link the enzyme to the polymer. On immobilization, the kinetic constants (Km e Vmax), the amount of immobilized enzyme with Bradford method and the activity of free and immobilized enzyme with p-nitrophenyl acetate (PNPA) hydrolysis, were determined. PSU membranes prepared by phase inversion are hydrophobic and, when compared with Selemion®; CMT and CMV commercial membranes, present lower permeselectivity, lower ion exchange capability and higher resistance. Membranes pore diameter is lower than 100 nm. The maximum amount of immobilized enzyme in the membranes reached 2.35 mg per gram of polymer after 18 hours of immobilization with a 61,2% yield . Enzyme activity decays after immobilization , from 14780 U.g-1 (free enzyme) to 1184 U.g-1 (immobilized enzyme).

Membrane processes can cover a wide range of separation problems [with a specific membrane (membrane structure) required for every problem]. Thus, there are membranes available that differ in their structure and consequently in the functionality. Therefore membrane characterization is necessary to ascertain, which membrane may be used for a certain separation. Membranes of pore size ranging from 100nm to 1μm with a uniform pore size are very important in membrane technology. An optimum performance is achieved when the membrane is as thin as possible having a uniform pore size. Here in this thesis, membranes were synthesized by particle assisted wetting using mono-layers of silica colloids as templates for pores along with polymerizable organic liquids on water surface. The pore size reflects the original shape of the particles. Thus it is possible to tune the pore size by varying the particle size. This method is effective to control pore sizes of membranes by choosing silica particles of suitable size. This approach gives a porous structure that is very thin, but unfortunately limited in mechanical stability. Thus there is a need for support which is robust and can withstand the various mechanical stresses. A small change in the membrane or defect in the layered structure during the membrane formation can have drastic effect on the assembly. Lateral homogeneity of the layer generated by the particle assisted wetting can be judged by examination of its reflectivity, but once it is transferred on any solid support this option is no more. So a method is needed to detect the cracks or the inhomogenity of the membrane which can be detected even after the transfer. To tackle this problem a very simple and novel technique for characterizing the membrane by fluorescence labeling and optical inspection was developed in this thesis. The idea was to add a fluorescent dye which is poorly water soluble to the spreading solution comprising of the particles and the monomer. If the dye survived the photo-cross linking, then it would be embedded in the cross-linked polymer and would serve as a marker. Defects and inhomogenity would show up as cracks and spots. By the method that we have developed, we can detect our membrane from the support and spot defects.

This thesis reports on the synthesis and characterisation of various types of oxidised multiwalled carbon nanotubes (O-MWCNTs) modified polymeric membranes. These OMWCNT modified polymeric membranes were then assessed in terms of their remediation potential, in particular for the removal of estrogenic hormones, dissolved proteins and salts from brackish water sources. The fabricated O-MWCNT-based polyethersulfone (PES) membranes were applied as (i) adsorptive membranes, (ii) molecular-sieving membranes and (iii) as membrane substrates for thin-film composite nanofiltration (NF) membrane preparation. The research work commences with the preparation of MWCNTs via a facile catalytic chemical vapour deposition method and their chemical oxidation with strong acids in order to introduce hydrophilic carboxylic (–COOH) and hydroxyl (–OH) surface functional group moieties on the MWCNT outer walls. Intrinsically, MWCNTs are chemically inert and tend to form agglomerated nanoclusters (due to van der Waals interaction forces), which induce further difficulties in their homogenous dispersion in polar solvents (such as N-methyl-2- pyrrolidone and dimethylacetamide) employed to dissolve the polymers in the study. The introduction of these oxygen-containing moieties was therefore necessary to aid the dispersion of MWCNTs in organic solvents and for their enhanced interaction with PES and sulfonated polysulfone (SPSf). The PES/O-MWCNT ultrafiltration (UF) membranes were produced via a non-solvent induced phase separation (NIPS) method and employed in the adsorptive removal of natural hormone estrone (E1). The PES/O-MWCNT UF membranes thus prepared were characterised using SEM, AFM, zeta potential measurements and MWCO experiments. It was found that the adsorption of E1 initially increased with an increase in O-MWCNT content followed by a constant decline on further increments. Moreover, the inclusion of OMWCNTs (0.5 wt.%) in the PES membrane matrix resulted in an increase in the maximum adsorption capacity for E1 compared to pristine PES membrane, i.e., 31.25 mg/g adsorption capacity was achieved for PES/O-MWCNT compared to 23.81 mg/g for bare PES UF membrane. Based on the correlation coefficients, the Freundlich isotherm provided a better fit for the adsorption data and the adsorption kinetics followed the pseudo-second order kinetic model. Interestingly, after five regeneration cycles, the PES/O-MWCNT membranes were found to maintain similar adsorption efficiencies. The PES/O-MWCNT membranes thus prepared, present a viable approach for the removal of natural hormones and other endocrine disruptors present in water systems compared to the use of common adsorbents such as activated carbon, which end up generating large amounts of chemical sludge that require disposal in the environment. The third part of the study focused on the controlled formation of macrovoid-free polyethersulfone/sulfonated polysulfone (PES/SPSf) UF membranes with high water permeabilities, mechanical strength and antifouling properties, in the presence of O-MWCNTs. To date, the majority of polymeric nanocomposite membranes modified with O-MWCNTs as nanofillers, generally have finger-like structures and macrovoids in the membrane sublayer. While the presence of finger-like structures is favoured for the reduction in mass flow resistance, their presence induces mechanically weak points in the membrane and reduces the nanocomposite membranes’ mechanical strength properties and long-term performance stability. As such macrovoid-free PES/SPSf/O-MWCNT membranes were fabricated via the NIPS techniques, using H2O and polyethylene glycol (PEG 20 kDa) as non-solvent additives. The SEM cross-sectional images showed that a fully sponge-like morphology of the PES/SPSf membrane can be achieved in the presence of different loadings of O-MWCNTs. This was attributable to the formation of stronger hydrogen bonds between the SPSf polymer and non-solvent additives i.e., H2O, PEG 20kDa and OMWCNTs. The combination of the macrovoid-free morphology and homogenous distribution of high mechanical strength O-MWCNTs in the membrane matrix provided excellent mechanical strength enhancements for PES/SPSf/O-MWCNT membranes. Additionally, pure water flux initially increased from 598 L/m2 .h to 713 L/m2 .h followed by a decline to 578 L/m2 .h upon further increments in O-MWCNT contents, due to agglomeration of O-MWCNTs at higher loadings. The fabricated PES/SPSf/O-MWCNT membranes also displayed superior antifouling properties (FRR > 90%) and antibacterial properties (99% bacterial killing ratio) against E. coli bacteria. The fabricated support fabricfree PES/SPSf/O-MWCNT UF membranes with macrovoid-free sublayer morphologies displayed attractive features for use as UF membranes in the pre-treatment stages of water treatment and as support substrates for the preparation of TFC membranes. In general, sponge-like and macrovoid-free membrane structures are regarded as unfit for use as support membranes for TFC membrane preparation since they increase the membrane’s resistance to water flow, thereby reducing the overall TFC membrane permeability. This assumption has largely been based on sponge-like and macrovoid-free membranes structures achieved through the use of extremely high polymer concentrations, particularly using polysulfone (PSf) polymer. Hence, the sponge-like structures formed are very dense and less porous. Nevertheless, the macrovoid-free PES/SPSf/O-MWCNT membranes produced in this study, consisted of open cellular network microstructures within the membrane sublayer, which could be visualised at higher SEM magnifications. This part of the work therefore investigated the role of hydrophilic, macrovoid-free PES/SPSf and PES/SPSf/O-MWCNT as support membranes on the performance of TFC NF membranes. The TFC NF membranes were prepared via an efficient interfacial polymerization reaction between piperazine (PIP) and trimesoyl chloride (TMC). The deposition of the polyamide thin-film layer was confirmed by ATR-FTIR, SEM, AFM, contact angle and zeta potential measurements. Membrane performance results showed that TFC NF membranes fabricated on PES/SPSf/O-MWCNT support membranes displayed a 35% improvement in pure water flux with comparable salt rejections from those prepared on bare PES/SPSf support membranes. Salt rejection followed the order of Na2SO4 > MgSO4 > NaCl, which is typical for negatively charged NF membranes. It was established that the presence of hydrophilic O-MWCNTs in the support membrane allowed for the formation of a thin polyamide layer on the top surface of the support membrane, which gave rise to enhanced water permeability of the TFC NF membrane and the possibility of polyamide rejection layer within the support membrane pore channels. To further improve the performance of the TFC NF membranes, in particular, the monovalent/bivalent salt selectivity, a mixture of PIP and 2,4-diaminobenzene sulfonic acid (2,4-DABSA) at different weight ratios was prepared in the aqueous solution and reacted with TMC in the organic phase solution. It was found that the addition of low monomer weight ratio of 2,4-DABSA in the amine mixture, lead to the generation of a sulfonated TFC NF membrane with superior membrane performance in terms of pure water permeability (30.2 L/m2 .h), monovalent/bivalent salt selectivity (𝛼NaCl/Na2SO4 = 25.0) at low operating pressures (3 bar) and salt concentrations in the range of brackish waters. This was attributable to the combined presence of sulfonic acid groups on the membrane surface and the formation of the thin polyamide layer. Moreover, sulfonated TFC NF membranes exhibited good antifouling properties against bovine serum albumin (BSA), with FRR of 96.4% after three cycles of fouling and cleaning, with a fairly stable membrane performance over a 10-day period of pure water flux and Na2SO4 rejection testing. Indeed, the use of a macrovoid-free PES/SPSf/O-MWCNT support membrane did not only provide the mechanical strength for the deposition of TFC NF membrane, but also their open, cellular network microstructure, combined with high hydrophilicity and large surface pore sizes were beneficial in the reduction of polyamide layer thickness, and subsequently in the enhancement of TFC NF membrane performance. The study provided insightful information on lesser known aspects of O-MWCNT incorporated polymeric membranes, with regards to membrane structural configurations in relation to the membrane structure-performance relationships. It has been deduced that (i) the right combination of membrane surface characteristics and adsorbate solution chemistry is necessary for an open UF membrane to display reasonable removal efficiencies for low molecular-weight solutes, (ii) the combination of macrovoid-free membrane morphology with good dispersion of O-MWCNTs in the polymer matrix is necessary to realise significant enhancements in the mechanical properties of sulfonated membrane and (iii) formation of a thin sulfonated polyamide layer on top of the hydrophilic PES/SPSf/O-MWCNT support membrane is necessary to achieve high salt selectivity, and allow for the sulfonated TFC NF membrane to be operated at low pressures. / College of Engineering, Science and Technology

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