Masters Degrees (DMME)

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Browsing Masters Degrees (DMME) by Title

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    Assessment of copper recovery from leaching of microwave pre-treated tailing from the Otjihase mine
    (University of Namibia, 2020) Amuthenu, Victoria L
    Copper forms one of the world 's most important metals, with vital properties such as high malleability, toughness, and is an excellent conductor of heat and electricity. These properties make copper su itable for a vast range of industrial applications, and predominantly electrical applications. Currently, Namibia has a limited number of active copper mines, and hence a means to recover copper from secondary sources would positively impact Namibia's copper production and would also be beneficial to the Namibian economy. In this study, the assessment of copper dissolution efficiency by microwave-assisted leaching is considered. XRD analysis of the as-received mine tailings revealed that copper is present in the tailings material in the form of sulphide minerals only, covellite (CuS) and chalcopyrite (CuFeS2). Dry mine tailings of particle size -75μm were subjected to microwave pre-heating for 6 minutes in a domestic microwave oven for varying microwave intensities. This was followed by leaching with 0.5M Sulphuric Acid at varying temperatures and leaching times, in a water bath at atmospheric pressure. Results of the effect of leaching time, leaching temperature and microwave irradiation intensity are provided in this work. The results suggest that increasing leaching time and leaching temperature has a slight positive impact on copper leaching efficiency, with the highest recovery of 36.13% obtained at a leaching time of 50 minutes, leaching temperature of 80°C and microwave pre-treatment power of 700W. It was also observed that increasing microwave power from 100 to 700W had no significant impact on the efficiency of copper dissolution. Shrinking core models revealed that diffusion through the product layer, as governed by the equation kdt = 1 - 2x8 - (1 - X8 ) 2!3 was found to 3 be the rate-determining step, and hence the dissolution reaction mechanism. Arrhenius plots were used to determine the activation energy, which was calculated to be in the range of 7.7- 22.69kJ/mol. Multiple linear regression revealed that microwave power, leaching time and leaching temperature were related to percentage copper recovery by the following equation: Rcu = 4.8525 * 10-4 i + 4.8325 * 10-2 t + 1.11565 * 10-1r + 23.92999
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    Development and characterization of sintered porous bioactive glass scaffolds for medical application
    (University of Namibia, 2024) Angula, Linus Tshiimi; Johnson, Oluwagbenga T.
    There is an ongoing effort to innovate engineering materials that are used in medical applications to support, enhance, or replace damaged tissue or perform a biological function. This study focuses on researching bioactive glass scaffolds resembling natural trabecular bone tissues that are widely used in medical applications. The research investigates the relationship between processing parameters and the resulting microstructures of borosilicate, borophosphate, and phosphate bioactive glass scaffolds. The study developed glass ceramics using traditional melt-quench methods; silicate composition S53B50 was processed at 1200 °C, while the P40B10 and Sr phosphate glasses were heated to 1100 °C. The sintering ability of the three types of glasses with a NaCl sacrificial pore-generating agent was achieved via spark plasma sintering technology at a rapid heat rate of 100 °C/min and temperatures ranging from 490- to 610- °C. The research work employed analytical techniques of thermogravimetric analysis (TGA), particle size analysis (PSD), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) to gather data and characteristic results. It was observed that producing the glass ceramics by fritting the melts produced more desirable amorphous microstructures with less than 50% crystallization over casting and annealing. Also, the S53B50 scaffolds had the highest strength at 1.7 MPa and Sr glass had the most deformation at 1.62 mm. The findings are attributed to the partially crystallized microstructures, with indexes varying between 47 % and 58 %. Sintering increased scaffold density, compressive strength, and crystallinity while decreasing the porosity in this way demonstrating an ability to control scaffold properties for different applications through the sintering process. This research study contributes to the improvement of bioactive glass scaffolds and their potential applications in the clinical sciences of drug delivery systems