Thesis (PhD)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: A new membrane based affinity separation system that is bio-specific, biocompatible, well characterised and capable of being regenerated or re-used is described. The amphiphilic non-ionic surfactant Pluronic® F108, was covalently derivatised to form two novel bioligands (Pluronic-Biotin and Pluronic-DMDDO) for the bio-specific immobilisation of avidin conjugated proteins and histidine tagged proteins respectively. Pluronic was also used to non-covalently functionalise nonporous membranes for ligand attachment and to simultaneously shield the surfaces from non-specific protein adsorption. Each component of this bioaffinity system (from the membrane matrix to the elution/desorption of the ligate/ligand system) was studied with the aim of producing a well characterised system and key quantitative data for the development of a robust, reliable, re-usable and scalable technology. Specifically, this study describes: 1. The fabrication and partial characterisation of nonporous planar and capillary membranes as model affinity matrices. 2. The development and evaluation of a robust protocol for solvent desorption and accurate colorimetric quantification of Pluronic® F108 and its derivatives. 3. Interfacial analysis of Pluronic adsorption onto nonporous affinity membranes, including the direct solid-state analysis of model, halogenated Pluronic derivatives using nuclear microprobe analysis. 4. Development of a surfactant based protocol for affinity membrane regeneration and re-use. 5. Specific bioaffinity immobilisation of avidin conjugated peroxidase onto biotinylated membranes in the presence of model protein foulants. 6. Cloning and expression of C-terminal hex-histidine tagged human cytochrome b5 into the bacterial expression system E. coli BL-21 DE3. 7. Development and characterisation of an immobilised metal affinity membrane system for metal chelation (Ni2+, Cu2+ and Zn2+) using a new chelator Pluronic- N,N-dicarboxymethyl-3,6-diazaoctanedioate and the bio-specific immobilisation of N-terminal hex-histidine tagged pantothenate kinase. / AFRIKAANSE OPSOMMING: 'n Nuwe membraan-gebaseerde affiniteitskeidingsisteem word beskryf wat biospesifiek, bioversoenbaar en goed gekarakteriseer is, en geregenereer of hergebruik kan word. Die amfifiliese nie-ioniese surfaktant Pluronic is kovalent gederivatiseer om twee nuwe bioligande (Pluronic-Biotien en Pluronic-DMDDO) te vorm vir biospesifieke immobilisering van proteïnligate. Pluronic is ook gebruik om nie-poreuse membrane niekovalent te funksionaliseer vir ligandaanhegting en om hulle oppervlaktes teen niespesifieke proteïen-adsorbsie af te skerm. Elke komponent van hierdie bioaffiniteitsisteem (van die membraanmatriks tot die uitwas/desorpsie van die ligaat/ligand sisteem) is ondersoek met die doel om 'n goed-gekarakteriseerde sisteem te produseer en om kwantitatiewe data te genereer vir die ontwikkeling van 'n robuuste, betroubare, herbruikbare en opskaleerbare tegnologie. Hierdie studie beskryf spesifiek: 1. Die fabrisering en gedeeltelike karakterisering van nie-poreuse planêre en kapillêre membrane as model affiniteitsmatrikse. 2. Die ontwikkeling en evaluering van 'n robuuste protokol vir oplosmiddel desorpsie en akkurate kolorimetriese kwantifikasie van Pluronic® F108 en afgeleides daarvan. 3. Intervlakanalises van Pluronic adsorpsie op nie-poreuse affiniteitsmembrane, insluitend die direkte vastetoestand analise van model ligand-gemodifiseerde Pluronic deur die gebruik van kern-mikrosonde analise. 4. Ontwikkeling van 'n surfaktant-gebaseerde protokol vir affiniteitsmembraan regenerering en hergebruik. 5. Spesifieke bioaffiniteitsimmobilisering van avidien-gekonjugeerde peroksidase op gebiotinileerde membrane in die teenwoordigheid van model bevuilende proteïne. 6. Klonering en uitdrukking van C-terminaal hex-histidien geëtiketeerde menslike sitochroom b5 in die bakteriële uitdrukkingsisteem E. coli BL-21 DE3. 7. Ontwikkeling en karakterisering van 'n geïmmobiliseerde metaalaffiniteitsmembraansisteem vir metaalchelering (Ni2+, Cu2+ en Zn2+) met behulp van die nuwe cheleerder Pluronic-N,N-dikarboksimetiel-3,6- diasaoktaandioaat en die bio-spesifieke immobilisering van N-terminaal hexhistidiengeëtiketerde pantotenaatkinase.

<p>Over the past 40 years, research pertaining to membrane technology has lead to the development of a wide range of applications including beverage production, water purification and the separation of dairy products. For the separation of gases, membrane technology is not as widely applied since the production of suitable gas separation membranes is far more challenging than the production of membranes for eg. water purification. Hydrogen is currently produced by recovery technologies incorporated in various chemical processes. Hydrogen is mainly sourced from fossil fuels via steam reformation and coal gasification. Special attention will be given to Underground Coal Gasification since it may be of great importance for the future of South Africa. The main aim of this study was to develop low temperature CsHSO4/SiO2 composite membranes that show significant Idea selectivity towards H2:CO2 and H2:CH4.</p>

Steady state crossflow microfiltration (CMF) is an important and often necessary means for varying sized particle separation. It has been widely used in both industrial and biomedical processes, including a wearable water removal device intended to maintain end stage renal disease (ESRD) patients euvolemic. For kidney replacement therapies, there are few options available. Kidney transplantation still represents the optimal treatment for ESRD patients, even though it often requires daily post-transplant medication including immunosuppressant drugs to avoid rejection of the transplanted organ. The transplanted kidney itself has an average lifespan of only 10 years. The biggest engineering contribution to the cited problem was made about 60 years ago with the invention of dialysis machines (or some variation thereof). Dialysis still represents the optimal and most widely used therapeutic approach to renal replacement during long waits on a transplant list. The present-day dialysis system is bulky, totally mechanical, and extracorporeal, leading to a widely used therapy that is only effective in extracting water and toxins out of the blood-stream, but still with major drawbacks (i.e. intermittent treatments, 5-hours thrice-weekly, and forcing clinic-centered therapy) that are permanently costly. These drawbacks pose a major impediment to rehabilitation or any other lifestyle activity such as working or studying. Of all the vital organs, the kidney is both the most subtle in its homeostatic action and the most complex in terms of the structures it uses to accomplish its action. This thesis proposes a single facet of the multiple complexity of this vital organ: filtration. To that effect, CMF of blood suspensions through a microsieve were studied. Experiments, reported here, have correlated macroscopic measurements - filtration rates, transmembrane pressures (TMP), shear rates - during filtration through a photolithographically pored semiconductor membrane with direct observation of erythrocyte behavior at the filtering surface. Erythrocytes, the preponderant particles in blood, are believed to dominate filtration resistance. At low filtration rates (low TMP), erythrocytes roll along the filter, but at higher rates (higher TMP), there is an increasing probability of their sticking to the sieve. The design of membrane separation processes requires quantitative expressions relating the separation performance to material properties. The factors controlling the performance of CMF have been and continue to be extensively reviewed. There have been a number of influential approaches in CMF. Most have been based on the rate limiting effects of the concentration polarization of rejectate at the sieving surface. Various empirical and intuitive models exist which have been critically assessed in terms of their predictive capability and applicability to CMF from a microfluidic channel. Chapter 1 summarizes this assessment. Chapter 2 takes a closer look at how erythrocytes behave in a microfiltration environment. Maximum steady-state filtration flux has been observed to be a function of wall shear rate, as predicted by any conventional cross-flow filtration theory, but to show weak dependence on erythrocyte concentration, contrary to theory based on convective diffusion. Flux is known to be directly proportional to the TMP; however, since the pressure drop across a channel decreases along the direction of flow, TMP must modulate along the channel (highest at the leading edge of the membrane and lowest at the trailing edge). As a consequence, an area of stuck particles growing from the inlet (regimen of high TMP) has been observed, leading to a “fouling cascade.” Post-filtration scanning electron micrographs revealed significant capture and deformation of erythrocytes in all filter pores in the range 0.25 to 2 m diameter. This was then found to form a self-assembled partially complete monolayer. Filtration rates through these filters were reported and a largely unrecognized mechanism was proposed, which allows for stable filtration in the presence of substantial cell layering. Chapter 3 proposes a microfiltration model that pertains to non-deformable particles that are large enough to intrude significantly into the shear layer of a microchannel. A stable, stationary multilayer of particles was studied, whose thickness is shear-limited. The structure and parameters in that limit of steady filtration in this environment was then identified. A steady cake-layer thickness was observed and because of the simple geometry afforded by uniform spheres, the force balance, cake resistance, and filtration rate were derived from first principles. The good fit of the data to the proposed mechanism, provides a firm basis for the semi-quantitative analysis of the behavior of more complex suspensions. Finally, in Chapter 4, a design methodology was imposed to maintain the TMP constant throughout the whole sieving surface by introducing a flow chamber beneath and parallel to the sieve’s main flow. Co-current filtration was found to allow the TMP to remain stable along the membrane surface, enabling the entire sieve to perform optimally, and thus allowing greater stable filtration rates to be achieved. Co-current flow conditions allowed for twice as much filtration flux compared to a conventional CMF modality.

Hydrogen sulfide is toxic by-product of many petroleum, petrochemical and mineral treatment operations. Due to the increasing stringent environment regulations, toxic H2S must be completely removed from industrial waste gases before venting to the atmosphere. The H2S decomposition reaction is a well known thermodynamically limited reaction. Alumina membrane fixed bed catalytic reactors offer the potential for improved conversions at reduced operating temperature due to product separation and catalyst activity. A theoretical and experimental work dealing with a packed bed membrane reactor is the subject of this thesis. A tubular alumina membrane reactor possessing thermal and corrosion resistance has been developed. A multicomponent permeation study indicated that the fluxes of gases could be quantitatively described as a combination of Knudsen diffusion and viscous flow through the porous alumina membrane. The catalytic decomposition of hydrogen sulfide to hydrogen and sulfur was conducted in membrane reactor incorporating a commercial porous alumina membrane in combination with catalytic function of bimetallic RuMo sulfide catalyst. The obtained results demonstrate the possibility of achieving conversion above the equilibrium conversion. The reaction rate is equal to the intrinsic rate since both internal/external mass transfer and heat transfer resistance are negligible for the size of catalyst particles considered. Results obtained with this system have shown a maximum of 2.3 times the equilibrium conversion at the operating temperature 983K, which was equivalent to the conversion at operating temperature 1200K in a conventional fixed bed reactor. The conversion enhancement was significant for the operation with high sweep to feed molar ratio. The reactor configuration of membrane reactor appeared to have an influence on its performance. Comparative experimental and simulation study showed that the cocurrent mode gave slightly higher conversion over counter-current mode. Mathematical models were developed for the reactor, based on plug flow behavior. Simulation had been performed in order to validate the model against experimental data. Reactor optimization was carried out using the validated model. The simulation results from the non-isothermal model were in reasonable agreement with the experimental data. On the other hand, the isothermal model which neglected heat effects that took place in the reactor, has leaded to over-predicted conversion. This study also illustrated that predictive simulations could be used to explore the effects of recycle operation; the optimization study showed that the alumina membrane reactor permitting retentate recycle, could achieve up to 48.6% conversion, corresponding to 6 folded of the equilibrium conversion. The simulations provide a logical methodology for experimental planning and design. To further elucidate the effect of reactor configuration, operation conditions and permeation parameters on the performance of membrane reactors, a high permselective Pt-composite MR model was developed. Comparison of alumina MR and Pt-composite MR was carried out via computer simulation. Porous membrane reactor with higher permeability but lower Permselectivity can attain comparable conversion as the composite membrane reactor with higher permselectivity but lower permeability. Ptcomposite MR was more superior to alumina MR without recycle. Retentate recycle in alumina MR is shown to outperform the Pt-composite MR. Alumina MR was therefore considered as potential candidate for industrial H2S treatment.

Macromolecular components, including protein and polysaccharides, are viewed as one type of major foulants in the complex feed membrane filtration systems such as membrane bioreactor (MBR). In this thesis, the mechanisms of macromolecular fouling including protein and polysaccharide in the complex feed solution are explored by using Bovine serum albumin (BSA) and alginate as model solution. During the filtration of BSA and washed yeast with 0.22 ????m PVDF membrane, it was found that the critical flux of mixture solution was controlled by washed yeast concentration while the existence of BSA significantly changed the cake reversibility of much larger particles. The fouling mechanisms of alginate, as a model polysaccharide solution, were investigated both in dead end and crossflow membrane filtration. In the dead end experiments, it was found that the cake model appears to fit the entire range of the ultrafiltration data while the consecutive standard pore blocking model and cake model are more applicable to microfiltration membranes. The alginate was featured with high specific cake resistance and low compressibility despite some variations between different membranes. The specific cake resistance ( c ) is similar to c of BSA and actual extracellular polymer substance (EPS) in MBR systems reported in the literature, and higher than that of many colloidal particles. In a system contained alginate-particles mixture, it was found that the existence of alginate dramatically increased the cake specific resistance and decreased the cake compressibility. The fouling mechanism of alginate was also studied using long term cross flow filtration under subcritical flux. A two-stage TMP profile similar to that typically observed in MBR was obtained, confirming the important role of EPS during membrane fouling in MBR. In addition to adsorption, trace deposition of alginate also contributed to the initial slow TMP increase during the subcritical filtration. TMP increase during the long-term filtration was found not only due to the increase of the amount of deposition, but also the increase of specific cake resistance. A combined standard pore blocking and cake filtration model, using a critical pore size for the transition time determination, was developed and fit the experimental results well.

More than 1.2 million people worldwide require regular hemodialysis therapy to treat end stage renal failure. In the United States alone, there are 300,000 patients and the National Kidney Foundation predicts that this number will double in the next 10 years. Currently most dialysis patients receive treatment at a dialysis center and need three 4-5 hour treatments each week. While these treatments are useful, more frequent and longer duration dialysis better simulates natural kidney function. Consequently, at-home hemodialysis is expected to provide patients a better quality of life. Current hemodialysis systems are too expensive to support at-home hemodialysis. Cost drivers include the capital costs of the hemodialysis equipment and the raw material costs of expensive hemodialysis membranes. Microchannel hemodialysers have smaller form factors requiring significantly less membrane while enabling reductions in the size and cost of capital equipment. Microchannel devices are typically made by microchannel lamination methods involving the patterning, registration and bonding of thin laminae. Findings in this paper show that membrane utilization is highly dependent on registration accuracy with membrane utilization often dropping below 25%. Efforts here focus on the development of a self-registration method for assembling microchannel hemodialysers capable of supporting registration accuracies below 25 ��m over a 50 mm polycarbonate lamina. Using these methods, registration accuracies below 13 ��m were measured over a 50 mm scale. A mass transfer test article was produced with measured average one dimensional misregistration below 19 ��m with a demonstrated membrane utilization of 44.9% when considering both microchannel and header regions. Mass transfer results suggest that the device performed with a mass transfer area of 90.59 mm��. A design is proposed describing membrane utilization of over 79%. / Graduation date: 2013 / Access restricted to the OSU Community at author's request from 9-17-2012 - 9-17-2013

Thesis (M. Ing.)--University of Stellenbosch, 1997. / Bibliography. Also available via the Internet.

Thesis (M.S.)--University of Hawaii at Manoa, 2005. / Includes bibliographical references (leaves 63-67). Also available via World Wide Web.

Thesis (Ph.D)--Chemical Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Koros, William; Committee Member: Beckham, Haskell; Committee Member: Eckert, Charles; Committee Member: Henderson, Cliff; Committee Member: Meredith, Carson. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Thesis (Ph. D.)--Institute of Paper Chemistry, 1980.