An investigation was conducted on the dissolution of copper metal in aqueous solutions of ethylenediamine, glycine, α-alanine and β-alanine, under oxygen pressure. The kinetics of these reactions were investigated over a wide concentration range of the corresponding ionized species. The rate of dissolution of copper, in all solutions, has been found to be independent of the initial copper concentration, the volume of the solution and the area of the copper sample. No intermediate products, i.e., cuprous ions, were observed. Two regions were observed, having different dependence on oxygen pressure. In one, the rate depends on the first power of the oxygen pressure, and is independent of the concentration of the chelating agent. In the other region, the reaction is first order in chelating agent and independent of oxygen pressure. The rate of the reaction in this second region appears to be chemically controlled at the copper surface. The neutral and charged species of the chelating agent were found to have independent rates. These two dissolution reactions were found to be first order with respect to the concentration of the respective complexing species. The mechanism proposed by Halpern previously for the ammonia system was found to be applicable to the systems studied in the present work. The rate constants for each chelating agent have been computed and appear to be related to the stability constants. No steric effect was observed. / Applied Science, Faculty of / Mining Engineering, Keevil Institute of / Graduate

Physical and mathematical modelling studies have been performed to investigate liquid flow driven by a horizontally injected gas. The experimental work consisted of water velocity measurements made at 100 locations within a plexiglass tank. Air was introduced into the tank through a series of side-mounted tuyeres, and the effect of air flowrate on water recirculation velocity was observed. The results of the experiments indicate that the maximum water velocity occurs at the water surface. The effect of bubbles coalescing from adjacent tuyeres was observed with increasing air flowrate, and was found to diminish the water recirculation rate. The mathematical model employed a variant of the Marker and Cell (MAC) technique to compute fluid flow with a free surface. The model predictions indicate that the flow in the experimental tank is largely driven by water flowing across the free surface. Based on this knowledge, qualitative predictions of the flow regimes in a Peirce-Smith copper converter and a zinc slag fuming furnace were made. / Applied Science, Faculty of / Mining Engineering, Keevil Institute of / Graduate

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Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, Cape Town, 2006 / During recent years, the use of liquid membranes has gained general interest in the treatment of effiuents where solute concentrations are low and large volumes of solutions should be processed, and, if possible, without generating any secondary waste. Liquid membrane processes have been proposed as a clean technology, owing to their characteristics, i.e. high specificity, low energy and utilization. Two liquid membrane processes have been used in metal recovery, which are the liquid surfactant membrane (LSM), which corresponds to double water-in-oil emulsion and solid . supported liquid membranes (SLM), which are made by dispersing or impregnating the extractant within the pores of in.ert solid support. Previously, the recovery of eu (IT) in a SLM system was conducted by other membrane models such as hollow fibre, spiral and flat sheet. Only a small measure of success on scale-up and industrialization of these models has been attained. One of the disadvantages of the hollow fibre system was the small lumen size through which the feed needed to pass. Pores became clogged by suspended particles because the pressure drop over the small diameter augments lower flow rates and therefore, pre-filtering is necessary (Rathore, et al., 2001). In this study the behaviour of a tubular SLM reactor with an inner diameter of the lumen approximately fifty times bigger than that of the hollow fibre are used in order to solve the problem of clogging. This tubular reactor was incorporated in to a bench scale plant and proved successful in copper extraction. By observing transient data, mass transport coefficients were determined and compared to published values.

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