3. Electronic Theses and Dissertations (ETDs) - All submissions
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Item South African platinum group metals: possibility of beneficiation(2018) Skinner, Gary WilliamSouth Africa has an immense Platinum Group Metals (PGM) resource and with such a mineral rich comparative advantage, as opposed to other nations, it would be expected that this windfall could be manipulated to create substantial economic benefit. Sheer comparative advantage does contribute to the economy but added revenue and job creation could be achieved by further processing the metals into higher saleable products by using beneficiation. As the resource is located, close in proximity to the manufacturing industry, the movement of metals from the PGM refineries to the manufacturing facilities should be an advantage. However, circumstances and nuances, related to PGMs, make this sequence irrelevant due to the low transport costs of refined PGMs to processing facilities outside of South Africa. The global auto catalyst industry was, by far, the largest consumer of PGMs in 2016. This single industry consumed 12 million ounces and this aspect of a dominant downstream application makes PGMs unique. The Beneficiation Strategy for the Mineral Industry of South Africa from the Department of Mineral Resources (DMR) main value proposition was to translate the comparative advantage of the country’s mineral wealth into a related industrial competitive advantage and also to create employment. This mechanism was to be achieved through industrial diversification to produce upgraded, higher value products from raw or semi processed mineral products. Fundamentally, this notion is flawed with the downstream PGM industry as the location of the deposit compared to the processing zone has no bearing on the position of the auto catalyst manufacturer. The stimulus for this industry does not have the same drivers as compared to the extractive industry. The auto catalyst industry is dominated by a handful of multinational catalytic converter companies. These companies base their strategy on locality of competitive advantage, incentive policies are a major consideration as to the position of manufacturing facilities. The South African catalytic converter manufacturing industry has a global reach and is considered a trade policy success story. South Africa has an incentive policy which attracted these companies, but South Africa is not geographically located near to major automotive manufacturing hubs. In 2016, South Africa accounted for 1% of the global passenger car and commercial vehicle production and remarkably, produced 15% of the world’s auto catalysts. The incentive policy which drives the local auto catalyst industry uses local content addition to qualify for 65% export rebate certificates. Refined PGMs form part of the local content addition and South African refined PGMs are used in local auto catalyst manufacturing facilities. The driver for the auto catalyst industry is to qualify for the export rebate, local PGMs add to this qualification but the reality is that there is no real other advantage to use local PGMs. The South African auto catalyst sector is a R 20 billion South African industry, however, the primary PGM source, or the extractors, are struggling to maintain financial stability. The downstream beneficiation value chain is loaded in favour of the auto catalyst manufacturer and not advantageous to the extractor. South Africa supplied 56% of the global PGM demand in 2016 but this was overshadowed by the poor financial health of the PGM extraction industry which was subjected to a 47% platinum price plunge from 2010-2017. To leverage the maximum financial advantage through downstream beneficiation of the South African PGM supply is not possible. This would be a considerable risk to the multi-national auto catalyst manufactures who would have all of their investment in South Africa. Considering the remarkable progress of the South African auto catalyst industry, opportunities exist to re-evaluate the PGM value chain to benefit all stakeholders.Item Biosynthesis and characterization of metallic nanoparticles produced by paenibacillus castaneae(2017) Hiebner, Dishon WayneNanomaterials (NMs) have been shown to exhibit unique physical and chemical properties that are highly size and shape-dependent. The ability to control synthesis of nanoparticles (NPs) with particular shapes and sizes can lead to exciting new applications or enhancements of current systems in the fields of optics, electronics, catalytics, biomedicine and biotechnology. Due to increased chemical pollution as well as health concerns, biological synthesis of NMs has quickly emerged as potentially being an eco-friendly, scalable, and clean alternative to chemical and physical synthesis. In this study, the inference that the heavy metal-resistant bacteria, Paenibacillus castaneae, has the propensity to synthesize metal NPs was validated. NP formation was achieved after the exposure of bacterial cell biomass or cell-free extracts (CFE) to excess metal ion precursors in solution. These include lead nitrate and calcium sulphate dehydrate, gold (III) chloride trihydrate and silver nitrate, respectively. All reactions were incubated at 37 °C for 72 h at 200 rpm and observed for a colour change. UV–visible (UV-Vis) spectral scans (200 nm – 900 nm) were measured on a Jasco V-630 UV-Vis spectrophotometer. For scanning electron microscopy (SEM), samples were fixed, dehydrated and loaded onto carbon-coated aluminium stubs. The stubs were then sputter-coated with either Au/Pd or Cr and analysed on the FEI Nova Nanolab 600 FEG-SEM/FIB. Size distribution analysis was done using transmission electron microscopy (TEM) using the FEI Tecnai T12 TEM and Image J software. Powder X-ray diffraction measurements were carried out on a Rigaku Miniflex-II X-ray diffractrometer. Colour changes indicative of the synthesis of PbS, Au and Ag NPs were observed as a white precipitate (PbS), purple (Au) and yellow-brown (Ag) colour, respectively. This was confirmed by absorbance peaks at 325 nm and 550 nm (PbS), 595 nm (Au) and 440 nm (Ag) from UV-Vis analyses. Exposure of P. castaneae biomass and CFE to PbS ions in solution resulted in the production of nanospheres, irregularly-shaped NPs, nanorods, nanowires as well as large nanoflowers. Exposure of P. castaneae biomass to Au3+ ions in solution produced Au nanospheres, nanotriangles, nanohexagons, nanopentagons and nanopolyhedrons. Ag/AgCl NP production occurred using both the P. castaneae biomass and CFE, and resulted in the synthesis of nanospheres only. This is the first report of the biosynthesis of such a diverse set of anisotropic NPs by P. castaneae. It is also the first instance in which anisotropic PbS nanorods and nanowires, 3-D Au nanoprisms as well as “rough” Ag/AgCl nanospheres were bacterially produced. This study serves as an eco-friendly approach for the synthesis of NPs that is a simple yet amenable method for the large-scale commercial production of nanoparticles with technical relevance. This in turn expands the limited knowledge surrounding the biological synthesis of heavy metal NMs.Item The relationship between the metal dusting mechanism and the synthesis of carbon nanofilaments using toluene and a nickel based alloy(2016) Ramalall, Dawlall ShahilMetal dusting (MD) is a severe type of corrosion that occurs mainly in petrochemical industries. The occurrence of MD is mainly due to syngas attacking Fe-, Ni- and Co-based alloys at elevated temperatures. More recently, literature has shown that apart from syngas, liquid hydrocarbon sources have been causing problems on platformer units in refineries. In the first part of this study a highly corrosion resistant Ni-based alloy (Hastelloy C276), in its polished form, was subjected to MD conditions at 800 °C using a liquid hydrocarbon (toluene) and helium (carrier gas) for 1 h. Exposure to these conditions revealed the formation of carbon nanofilaments and graphite layers which were confirmed by laser Raman spectroscopy, scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). Burning off the carbon nanofilaments and the graphite layers in laboratory air for 1 h at 800 °C revealed that pits were formed on the Hastelloy C276. These same pits were not evident when Hastelloy C276 was exposed to either the carrier gas (helium) or laboratory air alone. Besides MD being a continuous problem in industry, this mechanism has been shown to be beneficial in the synthesis of carbon nanofilaments viz., carbon nanofibers (CNTs) and nanotubes (CNFs). In the second part of this study, unpolished Hastelloy C276 blocks (as opposed to polished blocks) were used to synthesize carbon nanofilaments. This was done as prior studies had shown that carbon nanofilaments were produced with better quality and greater yields this way. Here the flow rate (80, 160 and 240 mL/min) and reaction duration (10, 15, 30, 45, 60, 120 and 240 min) were studied using toluene (a liquid hydrocarbon). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to assess the quality and quantity of the carbon nanofilaments synthesized. Besides the formation of carbon nanofilaments, a less important material known as graphite particle structures (GPSs) were also synthesized. These studies collectively showed that MD had taken place on the surface of Hastelloy C276 when exposed to toluene at 800 °C.