3. Electronic Theses and Dissertations (ETDs) - All submissions

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    Galvanic interactions between minerals during dissolution
    (1994) Holmes, Paul Richard
    A quantitative description of galvanic interactions between sulphide minerals based on thermodynamic and kinetic parameters has been developed. The basis for quantitative description involves conducting a voltage balance over the galvanic couple. The contributions to the voltage balance include the galvanic couple cell emf, kinetic descriptions of the anodic and cathodic half reactions, the voltage characteristics 'of mineral-mineral contacts and solution voltage losses. The rates of the anodic and cathodic half' reactions were modelled by the Butler-Volmer equation and ti1ediffusion equation. A potentiostat was used to vary the voltages losses across mineral-mineral contacts. TIle galvanic couples were constructed. as rotating ring disc electrodes and hence electrolyte voltage losses were negligible. Three galvanic couples, copper-platinum, copper-pyrite and galena-pyrite, were electrochemically characterised under different conditions of ferric concentration, electrode rotation rate and temperature. The effect of illumination on the anodic dissolution of galena was investigated. The electrochemical model is in good agreement with experimentally measured galvanic currents. Galvanic interaction is a dynamic function and various models are developed which account for dynamic behaviour in galvanic cells.
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    Modelling the performance of Manganese electrowinning cells
    (2015) Rodrigues, Jose Carlos Pereira
    A comprehensive literature survey was conducted to obtain the available information on the manganese electrodeposition process.Using this information and measurments obtained from an industrial electrowinning plant,a modal was developed where the Interrelations between the most important parameters ware taken into account.Fundamental concepts were used wherever possible,except in a small section where no theoretical data was available. In this case empirical fitting of parameters was resorted to. The trends experienced in practice were all confirmed by the mode1,namely$ (i) the increase of cathodic currant efficiency with increased pH,which la limited by the precipitation of manganese hydroxide t (li) the increased current efficiency with decreased ammonium sulphate concentration; (ill) the existence of an optimum operating temperature for a given current density; (iv) the existence of an optimum current density for a given temperature; (v) the effect of total impurity level on current efficiency, the latter decreasing with increasing impurity level (vi) the steep increase of current efficiency with inorease of feed flow rata,to an upper limit condition at which point manganese hydroxide starts precipitating.
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    Modelling and optimisation of a manganese electrowinning plant
    (2015-01-15) Cronje, Brett Stephen
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