Masters Degrees (DMME)

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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