Browsing by Author "Kuipa, Olga"

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    Imaging Ellipsometry Study on the effect of Electrolyte on the drainage of an Aqueous Film trapped between a Plane Hydrophilic Silica Surface and an approaching Organic droplet
    (Sadguru publications, 2014) Kuipa, Olga; Kuipa, Pardon K.
    An imaging ellipsometer is used to study the drainage of an aqueous film trapped between a hydrophilic silica equilateral prism surface and a heptane or butylacetate droplet. The interfacial droplet profile on approach to the hydrophilic silica surface is such that the droplet is dimpled at its center with the periphery of the droplet (the barrier ring) being the region of closest approach to the hydrophilic silica surface. The time it takes for these drops to either achieve an equilibrium film thickness at the barrier ring or to coalesce with the macroscopic hydrophilic silica surface was experimentally determined; drainage time increases whilst equilibrium film thickness decreases with increasing salt concentration in the continuous phase. The increase in drainage time is attributed to hindered drainage of the aqueous film due probably to an increase in the aqueous film viscosity, which should translate into a decrease in the film elasticity. Compression of the double layer may also qualitatively explain the observed decrease in equilibrium film thickness at the barrier ring as the salt concentration increases. When aluminum chloride is used as the electrolyte the equilibrium film thickness is relatively constant (around 90 ± 10 nm) for the range of concentrations studied. This may be due to the fact that the aluminum ion has a valence of three and may screen electrostatic interactions between the oil droplet and the hydrophilic silica surface at relatively lower aluminum chloride concentrations.
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    Recovery of Lead from Lead Laden Cupels by a Simultaneous Leaching and Electrowinning Process in a Methanesulphonic acid bath
    (Sphinx Knowledge House, 2014) Mangunda, Cledwyn T.; Kuipa, Olga; Sithole, Tapuwa R.; Kuipa, Pardon K.
    Cupels are generated by mines during the fire assaying of precious group metals. The cupels contain lead which is a known environmental hazard hence the need to recover it. This work illustrates how leaching and electrowinning processes can be combined to produce a hybrid lead recovery process. Bench scale tests were conducted for the hybrid leaching and electro winning process using Methane Sulfonic Acid (MSA) as a leaching solvent at a concentration of 200g MSA per litre of water. A glass electrowinning cell fitted with a 9cm × 4cm pure lead cathode and 9cm × 4cm graphite anode with inter electrode gap of 15cm and a magnetic stirrer bar was used. Lead laden cupels (containing 30g lead) were subjected to simultaneous leaching and electrowinning and lead recovery after a period of 80 minutes was found to be 98%. The hybrid process was found to require about 20% less solvent than that required for the convectional leaching process which requires multiple stages to reduce the concentration of the solute in the raffinate to the same extent.
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    Recovery of Lead from Lead Laden Cupels by a Simultaneous Leaching and Electrowinning Process in a Methanesulphonic acid bath
    (Sphinx Knowledge House, 2014-07) Mangunda, Cledwyn T.; Kuipa, Olga; Sithole, Tapuwa R.; Kuipa, Pardon K.
    Cupels are generated by mines during the fire assaying of precious group metals. The cupels contain lead which is a known environmental hazard hence the need to recover it. This work illustrates how leaching and electrowinning processes can be combined to produce a hybrid lead recovery process. Bench scale tests were conducted for the hybrid leaching and electro winning process using Methane Sulfonic Acid (MSA) as a leaching solvent at a concentration of 200g MSA per litre of water. A glass electrowinning cell fitted with a 9cm × 4cm pure lead cathode and 9cm × 4cm graphite anode with inter electrode gap of 15cm and a magnetic stirrer bar was used. Lead laden cupels (containing 30g lead) were subjected to simultaneous leaching and electrowinning and lead recovery after a period of 80 minutes was found to be 98%. The hybrid process was found to require about 20% less solvent than that required for the convectional leaching process which requires multiple stages to reduce the concentration of the solute in the raffinate to the same extent.
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    Removal of Cr(VI) from Aqueous Solutions Using Powder of Potato Peelings as a Low Cost Sorbent
    (Hindawi Publishing Corporation, 2014-06) Mutongo, F.; Kuipa, Olga; Kuipa, Pardon K.
    Potato peels which are a low cost, renewable agroindustry by-product were used for the removal of hexavalent chromium from aqueous effluents. Batch experiments were carried out with an artificial effluent comprising of potassium dichromate in deionised water. The effects of the initial hexavalent chromium concentration, dose of biosorbent, and removal kinetics were explored. An adsorbent dosage of 4 g/L was effective in complete removal of the metal ion, at pH 2.5, in 48 minutes. The kinetic process of Cr(VI) adsorption onto potato peel powder was tested by applying pseudo-first-order and pseudo-second-order models as well as the Elovich kinetic equation to correlate the experimental data and to determine the kinetic parameters. The adsorption data were correlated by the Langmuir and Freundlich isotherms. A maximum monolayer adsorption capacity of 3.28 mg/g was calculated using the Langmuir adsorption isotherm, suggesting a functional group limited adsorption process. The results confirmed that potato peels are an effective biosorbent for the removal of hexavalent chromium from effluent.
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    Removal of Pyrethrin from Aqueous Effluents by Adsorptive Micellar Flocculation
    (Hindawi Publishing Corporation, 2015-01-06) Kuipa, Olga; Kuipa, Pardon K.
    The equilibrium adsorption of pyrethrin onto aggregates formed by the flocculation of micelles of the surfactant sodium dodecyl sulphate (SDS) with aluminium sulphate is reported.The experimental results were analysed using different adsorption isotherms (Langmuir, Freundlich, Redlich-Peterson, Sips, Radke-Prausnitz, Temkin, linear equilibrium, and the Dubin-Radushkevich isotherms). The Freundlich and linear equilibrium isotherms best describe the adsorption of pyrethrin onto SDS micellar flocs, with the Freundlich adsorption constant, 𝐾 𝐹, and the mass distribution coefficient, 𝐾 𝐷, of 64.266 ((mg/g)(L/mg)1/𝑛) and 119.65 L/g, respectively. Applicability of the Freundlich adsorption model suggests that heterogeneous surface adsorption affects the adsorption. The mean free energy value estimated using the Dubinin-Radushkevich isotherm was 0.136 kJ/mol indicating that physisorption may be predominant in the adsorption process.