The overall focus of this thesis is on the development and understanding of nanoporous layered silicates and membranes, particularly for potential applications in gas separations. Nanoporous layered materials are a rapidly growing area of interest, and include materials such as layered zeolites, porous layered oxides, layered aluminophosphates, and porous graphenes. They possess unique transport properties that may be advantageous for membrane and thin film applications. These materials also have very different chemistry from 3-D porous materials due to the existence of a large, chemically active, external surface area. This feature also necessitates the development of innovative strategies to process these materials into membranes and thin films with high performance.

This project was specifically aimed at using increased acceleration separation, as a method to optimize the recovery of gold in an ore body mainly consisting of hematite. The specific gravity of gold is much higher in comparison to the carrying material, making it possible to separate gold from other materials such as silica, base metals and their oxides, usually associated with gravitation–gold–recovery processes. The ore body investigated in this project originated from a mined gold reef containing a large proportion of gold locked inside the gold pyrite complexes. In the mine's processing plant a gold pyrite concentrate was produced by means of a flotation process. The roasting process that followed, oxidized the pyrite to iron oxide (hematite) and sulphur dioxide. The gold particles which were locked up inside the pyrite gold complex were exposed or liberated, allowing the chemicals to penetrate the complex and dissolve the gold. After the cyanide gold extraction process, the material was pumped on to a mine reserve dump, referred to as tailings or tailings reserve dump. The tailings usually contain iron oxides, free gold, gold associated with iron oxides and gold associated with silica, and free silica, commonly referred to as calcine. The gold content on the calcine dump was significantly lower than the flotation concentrate before the extraction of the gold and it was no longer viable for the mine to process the tailings further. As the volume of the mine reserve dump increased over the years, it became viable to recover the gold in a high volume low grade plant. Several attempts were made to recover the gold in this dump, but due to the high cost of processing and milling the material, it was not done. The norm in the mining industry is that it is impossible to concentrate the gold by means of gravity separation techniques where the average particle sizes are smaller than 50 um in diameter and upgrading with inexpensive gravity separation techniques was ruled out by the mine, because the average particle sizes were too small. The dump investigated in this project differed from other reserve dumps in that the main phase of material in this dump was hematite and not silica. A suspension of this material would have different fall–out properties than other mine reserve dumps, because of the hematite's high specific gravity compared to silica. This property of the material birthed the idea that the material will respond positively to high acceleration separation, although the particle sizes were too small for effective upgrading according to the norm in the mining industry. Using acceleration concentration as a first stage in the gold recovery process the production cost per gram of gold produced could be reduced significantly. Firstly, the volume of concentrated material to be treated in the chemical extraction process was reduced ninety percent and secondly, the gold concentration was increased significantly. If the gold could be concentrated to more than twenty grams of gold per ton, it could be extracted economically with an aggressive chemical processes. This was not possible with low grade material contained in the dump. The theoretical principle, on which this project was based, was to make use of high acceleration separation to establish separation between the particles associated with the gold, and the particles not associated with gold. Applying a high gravitational force would have an influence on the velocity by which the particles would fall–out in a suspension. As the acceleration force increased the fall–out velocity would also be increased and the particles with higher specific gravity would be affected more. A factor that was equally important was the particle size and weight distribution. A large hematite particle would compete with a small gold particle due to the similarity in weight. This could cause loss in small gold particles or retention of hematite particles with no gold content. Very little scientific information was available on the material investigated and in order to assemble a concentration plant setup, the head grade and particle size distribution for both the dump and bulk sample were determined accurately. Thereafter, chemical analyses and mineralogical examination were done on a representative sample of the bulk sample, determining the chemical composition of the material. The results obtained thereof were evaluated and used to configure a pilot plant. A large bulk sample was processed in the pilot plant and from the analytical results the efficiency could be evaluated. The results at optimum acceleration forces applied, resulted in a recovery of 5% of the mass, with a gold concentrate of 90 g/t Au, which represented 58% recovery of the gold. The hematite with high specific gravity as main phase positively influenced the high acceleration separation process. It proved that if the specific gravity of particles in a suspension were increased, high acceleration separation could be applied effectively to separate much smaller particle sizes. / Thesis (M.Sc. Engineering Sciences (Chemical and Minerals Engineering))--North-West University, Potchefstroom Campus, 2012.

This project was specifically aimed at using increased acceleration separation, as a method to optimize the recovery of gold in an ore body mainly consisting of hematite. The specific gravity of gold is much higher in comparison to the carrying material, making it possible to separate gold from other materials such as silica, base metals and their oxides, usually associated with gravitation–gold–recovery processes. The ore body investigated in this project originated from a mined gold reef containing a large proportion of gold locked inside the gold pyrite complexes. In the mine's processing plant a gold pyrite concentrate was produced by means of a flotation process. The roasting process that followed, oxidized the pyrite to iron oxide (hematite) and sulphur dioxide. The gold particles which were locked up inside the pyrite gold complex were exposed or liberated, allowing the chemicals to penetrate the complex and dissolve the gold. After the cyanide gold extraction process, the material was pumped on to a mine reserve dump, referred to as tailings or tailings reserve dump. The tailings usually contain iron oxides, free gold, gold associated with iron oxides and gold associated with silica, and free silica, commonly referred to as calcine. The gold content on the calcine dump was significantly lower than the flotation concentrate before the extraction of the gold and it was no longer viable for the mine to process the tailings further. As the volume of the mine reserve dump increased over the years, it became viable to recover the gold in a high volume low grade plant. Several attempts were made to recover the gold in this dump, but due to the high cost of processing and milling the material, it was not done. The norm in the mining industry is that it is impossible to concentrate the gold by means of gravity separation techniques where the average particle sizes are smaller than 50 um in diameter and upgrading with inexpensive gravity separation techniques was ruled out by the mine, because the average particle sizes were too small. The dump investigated in this project differed from other reserve dumps in that the main phase of material in this dump was hematite and not silica. A suspension of this material would have different fall–out properties than other mine reserve dumps, because of the hematite's high specific gravity compared to silica. This property of the material birthed the idea that the material will respond positively to high acceleration separation, although the particle sizes were too small for effective upgrading according to the norm in the mining industry. Using acceleration concentration as a first stage in the gold recovery process the production cost per gram of gold produced could be reduced significantly. Firstly, the volume of concentrated material to be treated in the chemical extraction process was reduced ninety percent and secondly, the gold concentration was increased significantly. If the gold could be concentrated to more than twenty grams of gold per ton, it could be extracted economically with an aggressive chemical processes. This was not possible with low grade material contained in the dump. The theoretical principle, on which this project was based, was to make use of high acceleration separation to establish separation between the particles associated with the gold, and the particles not associated with gold. Applying a high gravitational force would have an influence on the velocity by which the particles would fall–out in a suspension. As the acceleration force increased the fall–out velocity would also be increased and the particles with higher specific gravity would be affected more. A factor that was equally important was the particle size and weight distribution. A large hematite particle would compete with a small gold particle due to the similarity in weight. This could cause loss in small gold particles or retention of hematite particles with no gold content. Very little scientific information was available on the material investigated and in order to assemble a concentration plant setup, the head grade and particle size distribution for both the dump and bulk sample were determined accurately. Thereafter, chemical analyses and mineralogical examination were done on a representative sample of the bulk sample, determining the chemical composition of the material. The results obtained thereof were evaluated and used to configure a pilot plant. A large bulk sample was processed in the pilot plant and from the analytical results the efficiency could be evaluated. The results at optimum acceleration forces applied, resulted in a recovery of 5% of the mass, with a gold concentrate of 90 g/t Au, which represented 58% recovery of the gold. The hematite with high specific gravity as main phase positively influenced the high acceleration separation process. It proved that if the specific gravity of particles in a suspension were increased, high acceleration separation could be applied effectively to separate much smaller particle sizes. / Thesis (M.Sc. Engineering Sciences (Chemical and Minerals Engineering))--North-West University, Potchefstroom Campus, 2012.

Membrane separations are rapidly growing alternatives to traditionally expensive gas separation processes. For natural gas purification, membranes are used to remove carbon dioxide to prevent pipeline corrosion and increase the heating value of the natural gas. The robust chemical and physical properties of polyimide membranes make them ideal for the numerous components and high pressures associated with natural gas production. Typically, the performance of membranes changes over time as a result of physical aging of the polymer. Previous work shows that the thin selective layer of an asymmetric hollow fiber membrane, the morphology of choice for gas separations, ages differently than a thick dense film of the same material. Also, carbon dioxide, which is highly soluble in most polymers, can actively swell and plasticize polymer membranes at higher pressures. In this work, free acid groups present in the model polyimide are covalently crosslinked to stabilize the matrix against plasticization. Physical aging of two different crosslinked derivatives are compared to the free acid polyimide through gas permeation, gas sorption, and refractive index measurements. Thick (~50 m) and thin (~650 nm) films are examined to determine the effects of sample dimension on physical aging. The crosslinking mechanism employs diol substituents to form ester linkages through the free acid group. However, the annealing treatment, above the glass transition temperature, used to "reset" the thermal history of the films is found to form a new crosslinked polymer. Characterization of this new crosslinking mechanism reveals a high-temperature decarboxylation of the free acid creates free-radical phenyl groups which form covalent crosslinks through other portions of the polymer structure. Since ester crosslinks may be vulnerable to hydrolysis in aggressive gas feed streams, this new mechanism of crosslinking may create a more robust membrane for aggressive separations. In addition to the physical aging study, supercritical carbon dioxide conditioning of the two glycol crosslinked polyimides is compared to the free acid polymer. In this case, the free acid polymer is not crosslinked since the esterification crosslinking reaction occurs at much lower temperature than the decarboxylation mechanism. The free acid polymer displays an atypical permeation response under supercritical carbon dioxide conditions which suggests a structural reorganization of the polymer occurs. The crosslinked polymers do not exhibit this type of response. Mixed gas permeation confirms a substantial decrease in the productivity of the free acid polyimide and reveals the enhanced stability of the crosslinked polyimides following the supercritical carbon dioxide conditioning. Finally, examination of structurally similar fluorine-containing polyimides following approximately 18 years of aging allows the study of polymer structure on physical aging. A 6FDA-based polyimide is compared to a BPDA-based polyimide to understand the effects of bulky, CF3 groups on physical aging, and polyimides with diamine isomers reveal the effects of structural symmetry on physical aging.

Microfibers, textile fibres shorter than 5 mm, and are shed from fabrics during wear and released into the laundry effluent during washing. When passed through the wastewater treatment plant (WWTP), they adsorb toxins, heavy metals and pathogens before being released into the environment. Synthetic microfibers persist for long periods of time in aquatic environments and very little is known about the degradation of processed natural fibres. Hydrocyclonic separation was studied as a way to separate the microfibers from the effluent before being they get additionally contaminated at the WWTP. A hydrocyclone has no moving parts and functions by utilizing centrifugal force and the difference in specific gravity between the fluid and the particles that are to be separated. The separation efficiency is dependent on its dimensional and operation parameters. No previous studies on hydrocyclonic separation of microfibres were found. Polyester fleece blankets were washed. The effluent was filtered, and the filters weighed to determine the mass of the separated fibres. Sampling of the inhomogeneous effluent presented a challenge and larger sample volumes would be needed to adequately represent the population. Using a Büchner funnel, filter fouling led to filtration times of up to 6 h for 1 l of effluent. Dividing the 1 l samples into two 0.5 l samples, filtering separately and adding the weight reduced filtration time to 2 h and the results were not significantly different from filtering the whole 1 l sample with one filter. The hydrocyclones tested separated around 11% of the total weight of microfibers in the effluent, too low to be deemed viable. As only a few dimensional variables were tested, it could possible that a higher fraction could be separated with this method. Given that the commercially available filtration systems separate 30-80%, refining existing methods may yield better results.

Surface mean pressures, oil flow visualization, and 3-velocity-component laser-Doppler velocimeter measurements are presented for a turbulent boundary layer of momentum thickness Reynolds number, 7300 and thickness delta over two circular based axisymmetric bumps of height H = delta and 2delta and one rectangular based symmetric bump of H = 2delta. LDV data were obtained at one plane x/H ¥ 3.26 for each case. Complex vortical separations occur on the leeside and merge into large stream-wise mean vortices downstream for the 2 axisymmetric cases. The near-wall flow (y+ < 90) is dominated by the wall. For the axisymmetric cases, the vortices in the outer region produce large turbulence levels near the centerline and appear to have low frequency motions that contribute to turbulent diffusion. For the case with a narrower span-wise shape, there are sharper separation lines and lower turbulence intensities in the vortical downstream flow. Fine-spatial-resolution LDV measurements were also obtained on half of the leeside of an axisymmetric bump (H/delta = 2) in a turbulent boundary layer. Three-dimensional (3-D) separations occur on the leeside with one saddle separation on the centerline that is connected by a separation line to one focus separation on each side of the centerline. Downstream of the saddle point the mean backflow converges to the focal separation points in a thin region confined within about 0.15delta from the local bump surface. The mean backflow zone is supplied by the intermittent large eddies as well as by the near surface flow from the side of the bump. The separated flow has a higher turbulent kinetic energy and shows bimodal histograms in local and U and W, which appear to be due to highly unsteady turbulent motions. By the mode-averaged analysis of bimodal histograms, highly unsteady flow structures are estimated and unsteady 3-D separations seem to be occurring over a wide region on the bump leeside. The process of these separations has very complex dynamics having a large intermittent attached and detached flow region which is varying in time. These bimodal features with highly correlated local u and w fluctuating motions are the major source of large Reynolds stresses local u2, w2 and -uw. Because of the variation of the mean flow angle in the separation zones, the turbulent flow from different directions is non-correlated, resulting in lower shearing stresses. Farther from the wall, large stream-wise vortices form from flow around the sides of the bump. / Ph. D.

Att lämna ett våldsamt förhållande innebär inte alltid att kvinnan frigörs. Kvinnor som väljer att separera möter ofta allvarliga konsekvenser i form av hot och kränkningar. Det våld som sker efter separation definieras som eftervåld. Syftet med studien är att undersöka fenomenet eftervåld med hjälp av befintlig forskning. Den frågeställning som kommer att besvaras under studiens gång är: genom vilka former tar sig eftervåldet uttryck i kvinnornas liv? Studien baseras på en litteraturöversikt med 20 artiklar. Undersökningen av artiklarna genomfördes utifrån en tematisk analys som gav sju teman. Föreliggande studies resultat visar att eftervåldet tar sig uttryck genom ekonomi, barn, sabotage, manipulation, kontroll, hot och stalking. Resultatet tyder på att kvinnan utsätts för olika våldshandlingar efter separation. Ett återkommande fynd som litteraturstudien uppmärksammade var hur makt och kontroll återspeglats i samtliga teman som presenterats. Sammanfattningsvis konstateras den ojämlikhet mellan könen som Bourdieu (1999) redogör utifrån könsuppdelning, mannens dominans och det symboliska våldet. / To leave a violent relationship does not always result in the woman being liberated. Women who choose to leave the relationship often receive serious consequences (e.g., threats and violations). The violence that occurs after separation is defined as post-separation violence. The purpose of the study is to examine the phenomenon post-separation violence by using existing research. The research question that the study will be addressing is: in what forms does the post-separation violence manifest itself in the women’s lives? The present study is based on a literature review containing 20 articles. The examination of the articles was done by using a thematic analysis which resulted in seven themes. The results of the present study show that the post-separation violence manifests itself through economy, children, sabotage, manipulation, control, threat and stalking. The results indicate that the woman is exposed to various acts of violence after separation. A recurring finding that the literature study draws attention to was how power and control were the underlying factor to the post-separation violence. In summary, the inequality between the sexes that Bourdieu (1999) reports based on gender division, male dominance and symbolic violence is noted.

Vita. / Digitized by Kansas Correctional Industries

Call number: LD2668 .T4 1957 C48 / Master of Science

Call number: LD2668 .T4 1978 H75 / Master of Science