3. Electronic Theses and Dissertations (ETDs) - All submissions
Permanent URI for this communityhttps://wiredspace.wits.ac.za/handle/10539/45
Browse
5 results
Search Results
Item The rhizobiome of Vachellia (Acacia) woodlands surrounding Witwatersrand gold and uranium mine tailings(2018) Buck, Michelle ToniPhytoremediation of mine tailings and surrounding areas provide the most cost-effective means of alleviating their pollutant effects. Research has shown that successful revegetation of mine tailings and surrounding areas can be optimised by providing appropriate microbial symbionts for the plants. Microorganisms are beneficial to plant growth and health which is essential for revegetation and phytoremediation of contaminated sites. The aim of this study was to assess the microbial status of Vachellia karroo rhizosphere currently growing on the surrounding areas of two mining operations, namely Vaal River (VR) and West Wits (WW) Operations. Metataxonomy is the study/use of genetic material isolated from field/environmental samples. It has been reported from metataxonomy studies that a large amount of microbial biodiversity had been missed by cultivation-based methods. Metataxonony allows for an unbiased genetic analysis from all members of the sampled community since it is a PCR directed sequencing approach for identification. Root and soil samples were collected in spring, roots were removed and physio-chemical analyses were preformed on the soil, including pH, conductivity, cation exchange capacity and XRF analysis. The soil samples were then prepared for DNA extraction by mixing/bulking 5 g of soil for each niche site and control. Then 500 mg of soil was used to extract DNA using the DNeasy® PowerSoil® Kit (Qiagen). Target genes, namely the 16S rRNA V1-V3 hypervariable region and the ITS2 hypervariable region, were sequenced at Molecular Research LP MR DNA (http://www.mrdnalab.com), Texas. The rhizosphere bacterial communities of V. karroo from VR Operations was predominantly comprised of Acidobacteria, Actinobacteria, Bacteroidetes, Verrucomicrobia, Firmicutes, Planctomycetes, Gemmatimonadetes, (between 1 % and 47 % depending on the niche sites and controls) and the remainder of the phyla (Chloroflexi, Armatimonadetes, Nitrospirae, Candidatus Saccharibacteria, candidate division WPS-1 and candidate division WPS-2) were less than 1 %. The numbers all represent the average percentage of sequences across 14 phyla. For WW Operations the bacterial communities were predominantly comprised of Actinobacteria, Acidobacteria, Planctomycetes, Verrucomicrobia, Proteobacteria, Bacteroidetes, Chloroflexi, Firmicutes, Gemmatimonadetes, (between 0.7 % and 41.4 % depending on the niche sites and controls) and the remainder of the phyla (candidate division WPS-1, candidate division WPS-2, Armatimonadetes, Candidatus Saccharibacteria, Nitrospirae and Cyanobacteria/Chloroplast) were around 1 %. The numbers all iii represent the average percentage of sequences across 15 phyla. The rhizosphere fungal communities of V. karroo from VR Operations was predominantly comprised of Ascomycota (Sordariomycetes, Dothideomycetes, Eurotiomycetes, Ascomycota_unidentified, Leotiomycetes and Incertae_sedis_14); Zygomycota (Incertae_sedis_10); Basidiomycota, Agaricomycetes, Atractiellomycetes, Tremellomycetes (between 0.01 % and 77.1 % depending on the niche sites and controls) and to a lesser degree Glomeromycota (Glomeromycetes) and Fungi_unidentified (between 0.2-6 % depending on the niche sites and controls). The numbers all represent the average percentage of sequences across 12 classes. For WW Operations the fungal communities were predominantly comprised of Ascomycota (Sordariomycetes, Dothideomycetes, Eurotiomycetes, Ascomycota_unidentified, Leotiomycetes and Archaeorhizomycetes), Zygomycota (Incertae_sedis_10), Basidiomycota, Agaricomycetes, Tremellomycetes, Atractiellomycetes, Basidiomycota_unidentified, Fungi_unidentified and Glomeromycota (Glomeromycetes) (between 0.01 % and 91.42 % depending on the niche sites and controls). The numbers all represent the average percentage of sequences across 13 classes. The study represents a first report utilising metataxonomic tools in the analysis of the rhizobiome of V. karroo from areas around mine tailings. The results will assist in making decisions about future microbial surveys and applying microbial inoculum in revegetation of mine waste sites and the affected areas.Item The distribution and quantities of radioactive trace elements, in particular uranium and thorium, within the Waterberg Coalfield(2018) Murdoch, ShaunIn an uncertain future with regards to coal utilisation due to environmental regulations, coal mining, and particularly the future of coal mining located in the Waterberg Coalfield of the Ellisras Basin in South Africa, needs to be aware of all the risks and possible pitfalls that could hamper its further development. The radioactive elements, U and Th, which are typically associated with sedimentary environments where coal is formed, if found in elevated quantities, would be one of the risks that needs to be quantified. Based on the impact elevated U levels has had on the development of the Springbok Flats Basin, this study was instigated to evaluate if there was a similar risk to the coal resources and reserves in the Waterberg Coalfield, which lies 150 km to the northwest of the Springbok Flats Basin. Due to limitations related to access to samples it was not possible to sample the entire Karoo Supergroup sequence within the Waterberg Coalfield. However, a database of downhole wireline geophysical logs was compiled and used as a first order study to identify the most suitable horizons for sampling for geochemical analysis. A total of 34 exploration holes and 7,451 blast holes were used to compile the geophysical database. Trends related to gamma anomalies were determined where gamma values, here measured in American Petroleum Institute (API) values, are greater than 300. These were associated with the Eendragtpan (Beaufort) and Swartrant (Vryheid) Formations. The 54 anomalies (where API values greater than 300) within the Eendragtpan (Beaufort) Formation did not appear to follow any apparent trend. The 118 anomalies within the Swartrant (Vryheid) Formation conformed to two trends – the first was associated with a gradual increase in gamma values towards the base of the interburden between the coal zones 3 and 4A, Grootegeluk Bench 8. The second trend identified was that the anomalies were not associated with the coal seams, but instead with the interburden. The largest anomalies occurred in the interburden between the coal zones 2 and 3, at Grootegeluk Bench 10. Geochemical analysis of the Bench 10 interburden yielded only two anomalous U and Th values (compared to U and Th values reported by Swaine (1994)), with the mean values for U and Th being 2.89 ppm and 2.47 ppm respectively. Various classifications and analysis were applied to the geochemical results to help ascertain if there was any correlations or trends within the results; 1) Th/U ratios indicate that Bench 10 was deposited under reducing conditions; and 2) the samples with anomalous U and Th values also report elevated values for Y, Zr, Nb and Ag, and are depleted in Na and Al. The overall conclusion of the study was that while there was some U and Th, as would be expected in such an environment, there was not significant quantities found for exploitation purposes and it is unlikely that the radioactive elements will pose a health risk within the region. As such there is little cause for concern regarding the mining of coal within the Waterberg Coalfield, in particular pertaining to U or Th.Item Primary uranium mineralisation of the central Damara Orogen, Namibia: a petrographic, geochemical and mineralogical account of the granite - hosted uranium deposits situated along the Swakop- and Khan River valleys(2017) Freemantle, Guy GeorgeNamibia, the 6th largest producer of uranium globally, has produced uranium from Pan African granite-hosted (primary) deposits since 1976, and from palaeochannel deposits since 2007; exporting 3 472 tonnes U in 2016. The large granite-hosted deposits at the Husab Mine are expected to add over 5 700 tonnes U/year at peak, while three large primary-hosted deposits remain in various stages of development at Goanikontes, the Ida Dome, and Valencia. This study presents a comprehensive geological, geochemical and uranium mineralogical appraisal of four of the major primary-hosted uranium deposits, all situated within the southern Central Zone (sCZ) of the polydeformational (D1-D3) Damara Belt. The sCZ comprises highly deformed Neoproterozoic sediments, unconformably draped over rheologically competent granite-gneiss domes and inliers of a Palaeoproterozoic basement. A suite of fractionated sheeted leucogranites (SLGs) are a characteristic of the final stages of Orogenic deformation; while most SLGs appear to precede D3 deformation and metamorphism (ca. 510 Ma); most of the mineralised SLGs across the region invade reduced-facies sediments in pressure shadows formed in the hinges and limbs of upright D3 antiforms, proximal to basement inliers. A pre-existing, six-fold, alphabetised SLG classification scheme is revised and extended to categorise distinctive and consistent field and petrographic characteristics of the SLGs across the region. Discriminating SLG sub-types is less consistent in standard geochemical diagrams, except where high field-strength (HFS) and rare-earth elements (REE) are concerned. REE profiles in pre-D3 SLGs reflect abundances, or paucities, of characteristic accessory mineral assemblages; while REE profiles show relative REE enrichment, prominent REEfractionation and -ve Eu anomalies in the uraniferous SLGs, reflecting lower-percentage partial melts in the more uraniferous samples. The overwhelming majority of primary uranium mineralisation is in magmatic uraninite, followed by coffinite which predominate as a replacement phase of uraninite, and more rarely as solid solution with thorite. The refractory minerals betafite and brannerite are rare, but are locally abundant in discrete, magmatic textures within uraniferous SLGs of some deposits. Hydrated uranyl silicates predominate in the supergene portions of the orebodies across the region. An electron microprobe study presents the first comprehensive assessment of uraninite compositions in the region, while Husab deposit betafite and brannerite compositions allow for a well-rounded comparison with refractory minerals from the Rössing deposits. Key Words Primary Uranium, Granite, Orogenic, Damara, Namibia, Rare Earth Elements, Mineralisation, Fractionation, High-grade Metamorphism, Economic Geology, Mining, Processing, Uraninite, Coffinite, Etango, Goanikontes, Husab, Ida Dome, Rössing, ValenciaItem Sorption of uranium and arsenic onto iron hydroxide/oxide modified zeolite(2017) Nekhunguni, Pfano MathewsMining is an integral sector of most developing countries and it is a highly lucrative industry that has been in existence for centuries, and assumes an essential part in their economies. However, the legacy of mining in these countries has posed a threat to underground and surface water as a result of contamination arising from Acid Mine Drainage (AMD). Bearing in mind the environmental and ecological impairment posed by AMD there is a need for innovation in the treatment of AMD, to enable financially savvy treatment of the contaminated waters. This research is focused on the extraction of U(VI), As(III) and As(V) from synthetic metal solutions as well as field removal of these metal ions by application of iron hydroxide/oxide-modified zeolite. Batch experiments were performed to evaluate the effectiveness of iron hydroxide/oxide-modified zeolite as a potential low-cost sorbent for extracting As(III), U(VI) and As(V) from AMD. The research approach was based on the possible changes that can occur to a zeolite surface that has been in contact with an iron-laden solution. Zeolite is a commonly used adsorbent, but fewer studies have explored changes that it undergoes as an adsorbent on contact with iron solutions. Thus, the study involved modifying zeolite with iron hydroxide/oxide, which are the main precipitates of iron in the environment and which can possibly alter the adsorption properties of zeolite. Batch extraction studies were performed using the modified zeolite. In paper I, the synthesis of iron (hydr) oxide modified zeolite was achieved through precipitation of iron on the zeolite. The kinetic data for As(V) adsorption by iron (hydr) oxide-modified zeolite model fit well into pseudo second-order and the adsorption capacity was obtained as 0.080 mg g-1. The application of iron (hydr) oxide modified zeolite on AMD for As(V) recovery showed that > 99% of As(V) was extracted from the solution. The high removal efficiency of oxyanionic arsenic species was attributed to arsenic forming complexes with iron oxyhydroxide surface on the surface of the sorbent. Paper II dealt with adsorption of U(VI) from aqueous solution by application of iron hydro (oxide)-modified zeolite in a single-component system. Parameters such as: solution pH, contact time, adsorbent dosage, initial concentration and temperature were optimized before field application to real acid mine drainage. The optimum parameters for U(VI) adsorption were: adsorbent dosage (3.0 g), solution pH (6 ±0.1) and contact time (30 min). Optimum parameters where then applied to acid mine drainage were the effluent was found to be cleaner than the influent. In Paper III, iron oxide-coated zeolite (IOCZ) nanocomposite was prepared and fully characterized. This sorbent was then used for extraction of U(VI) and As(III) from aqueous solutions by application of batch techniques. Batch study results were modelled best by the pseudo second-order kinetic model and Freundlich isotherm. The adsorption capacity of both U(VI) and As(II) was dependent on the temperature. The presence of Cd2+, Co2+ and Cr3+ ions enhance the adsorption of As(III) whereas the opposite trend was observed for U(VI) sorption onto IOCZ nanocomposite.Item Numerical and theoretical modelling of uranium carbonate leaching(2014-09-19) Kamati, Messag KamatiThis research involved development of leaching models which characterise the carbonate leaching of a carnotite uranium ore from an industrial uranium processing facility. For confidentiality purposes, the name of the uranium processing facility was not explicitly stated. Fundamental, empirical, and linear multi-variable leaching models were developed. The fundamental model was developed from first principles and resulted in a differential equation governing the rate of disappearance of uranium from ore particles. This differential equation was solved by expressing the amount of uranium present in the particles in terms of fractional conversion. Empirical models were developed by fitting leaching data to four different exponential functions of forms analogous to the actual leaching profiles from the industrial plant. The multi-variable linear leaching model was constructed using a Microsoft excel linear regression statistical tool. All three types of models developed were found to predict the performance of a leaching process with reasonable accuracy. From the multi-variable leaching model it was found that even though the carbonate leaching of uranium is highly temperature driven, it is possible to operate the leaching process at low temperatures and still attain high leach efficiencies. This is achieved by adjusting other leach variables to compensate for reduced leach temperatures which has a potential of reducing energy costs by half, obtain high leach efficiencies and produce 20% more uranium. A mobile phone application based on the linear multi-variable model was developed as a portable process management tool. The mobile application was developed using a Livecode software and enabled easy visualisation of the effects of different values of leach variables on leaching process efficiency.