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This work has included a review of the most relevant aspects of measurement techniques and mathematical models proposed in the literature to assess the equilibrium and mass transfer data of metal extraction by the use of chelating agents. The limitations of these techniques and models have been highlighted. Three chelating extractants diluted in EscaidllO were used to study the extraction equilibrium of copper. The extractants are 5-nonylacetophenone oxime (LIX84®), 5- dodeylsalicylaldoxime (LIX860®) and 50/50 v/v mixture of both oximes (LIX984®). The copper concentration changes in the aqueous and the organic phases were monitored by using atomic absorption spectrophotometer. Two mathematical models (a chemical model and a semi-empirical model) have been developed in this study to predict the equilibrium data of copper sulfate/hydroxyoxime system. The chemical model was found to fit all the three equilibrium systems (CuSO4/LIX84®, LIX860®and LIX984®) equally. The semi-empirical model based on Freundlich's adsorption equation was also found to fit the three systems but with less accuracy. The mass transfer characteristics and properties of copper extraction and recovery from an aqueous solution using LIX984® were studied using dispersion-based (rising drops) and dispersion-free techniques. In the dispersion-based technique the organic phase was dispersed in form of drops at the tip of hypodermic needle while the aqueous solution was used as a continuous phase. The extraction process was carried out in four different height columns under wide range of conditions. The effects of the columns' height, the dispersed and the continuous phases concentrations on the metal rate of mass transfer were investigated. It has been found in that the metal's rate of mass transfer and system's overall mass transfer coefficient have remained constant in all four columns. A model utilising the two-film theory, some of the dimensionless groups and the experimental results has been proposed in this work to calculate the local mass transfer coefficients in the dispersed phase and the continuous phase. The overall mass transfer coefficient and the calculated local coefficients were used to account for the reaction rate constant at the interface from the sum of the individual resistances to mass transfer. A dispersion-free technique consisting of a microporous hollow fibre module was used in this study to examine the mass transfer properties of the extraction and stripping processes of copper across an immobilised interface system. The extraction and re-extraction (stripping) processes in this system were conducted under a wide range of operating conditions and produced satisfactory results. In general it has been found that counter current flow arrangement gave higher concentration driving forces which were reflected in form higher metal concentrations at the extract phase. A generalised mathematical model was developed in this study which utilised Wilson's method, the experimental data, some dimensionless groups and the two-film theory to account for local resistances and predict the system's overall mass transfer coefficient. A correlation was established first to calculate mass transfer coefficients using a form of Leveque's equation which relates the two phase's physical properties and the system's parameters. The membrane mass transfer coefficient was calculated from the structural properties of the membrane material. While the resistance at the reaction interface was calculated under set of experimental conditions. The individual coefficients were then used to predict the overall mass transfer coefficient under any set of conditions by using the aditivity approach of the individual resistances to mass transfer. However, further checks and investigations are necessary to validate this model over variety of extraction systems and membrane configurations.

Objectives: The objectives of this study were to establish the extent of dermal and respiratory exposure at selected locations at a South African platinum mine. The study included exposure to lead oxide fumes in an assay laboratory, nickel sulfate powder at a nickel sulfate crystallizer circuit and packing site and metallic copper dust whilst executing copper stripping. Methods: In an availability study, the dermal metal exposures were measured before, during and at the end of shifts. Dermal exposure samples were taken with GhostwipesTM from the dominant hand, wrist and forehead. Wipes were analyzed using Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES). Wipe samples were taken from surfaces in the workplace and analyzed according to NIOSH 9102, using ICP-AES. Personal and static inhalable dust samples were taken and the dust samples were analyzed according to NIOSH 7300, using ICP-AES. A validated questionnaire was used to evaluate self reported dermatological complaints of the workers at the fire assay laboratory and base metal recovery plant. Results: 100% of the nickel respiratory exposures and 36.8% of the lead respiratory exposures were above the occupational exposure limits (OEL). Copper respiratory exposure was present but less significant with a geometric mean of 0.071 mg m-3. All of the dermal lead measurements and the majority of the nickel and copper dermal measurements were below the limit of detection. Nickel surface contamination was the most significant and ranged between 8.430 μg cm-2 and 387.488 μg cm-2. Only 30% of the copper surface sample results were below the detection limit with a maximum surface sample of 14.41 μg cm-2. Lead surface contamination was low with 90% of the samples below the limit of detection. All of the workers at the nickel crystallizer circuit and packing site had a Dalgard score above 1.3 and therefore are at a higher risk of developing a skin disease. None of the workers at the copper stripping site had a significant Dalgard score and only one worker at the fire assay laboratory had a score above 1.3 and therefore is at a higher risk of developing a skin disease. Conclusions: Recommendations were made to lower the exposure to inhalable lead and nickel. The low lead dermal measurements may be due to adequate personal protective equipment usage and hygiene practices. Although the ethnicity of the workers may be the reason for the low incidence of dermatological complaints, the Dalgard score indicated that five workers are at risk of developing skin diseases. / Thesis (M.Sc. (Occupational Hygiene))--North-West University, Potchefstroom Campus, 2011

In the design of a solvent extraction plant for metals it is necessary to treat the equilibrium data either graphically or analytically. This enables stagewise calculations to be performed to explore solvent usage and feed conditions and so optimise on the cost of recovery of the metal. The present study reviews the methods of presenting and correlating equilibrium data for solvent extraction systems involving metals; the limitations of each approach are highlighted. The most important example of metal extraction which has been studied falls into that class involving a metal species, in acid aqueous media, which displaces protons from the organic extractant during the mass transfer process. In the typical case of copper extracted by hydroxyoximes the equilibrium problem reduces to one of modelling a surface. The concentration of copper in the organic phase is a function of the concentrations of copper and sulphuric acid in the aqueous phase. Empirical models seem to be as satisfactory to the engineer as chemical ones provided the model is used between restricted regions of data. Practical work has involved the measurement of equilibrium data for the extraction of zinc and copper by di- (2-ethylhexyl) phosphoric acid (D2EHPA) in a kerosene diluent. Both the single and binary metal systems have been studied. The data reported are for feeds between 2-40 g/l zinc, 2-60 g/l copper and 20% V/v D2EHPA. A limited number of results are also presented for 10% V/v D2EHPA. Specific chemical and empirical models have been developed to correlate these data. Because the extractant has a high affinity for zinc in the presence of copper the binary data can be modelled making the assumption that the interaction of copper on zinc is negligible. However the effect of zinc on the limited extraction of copper is significant, the zinc reducing the copper loading markedly. In this way zinc can be decontaminated of copper. The methods for presentation of equilibrium data are discussed and a computer program is given which displays three dimensional equilibrium surfaces. Classical design procedures for stagewise. calculations are used against these three dimensional data plots. Computer programs which allow the investigation of a variety of operating conditions have also been written.

Student Number : 9400913V - MSc (Eng) dissertation - School of Chemical and Metallurgical Engineering - Faculty of Engineering and the Built Environment / Natural zeolites are finding applicability in a broad range of industrial processes. This study assesses the potential applications of a South African natural zeolite, Clinoptilolite, and develops a methodology to quickly screen and assess these applications. Zeolites are known to have ion exchange and adsorption properties. Wastewater treatment has been identified as a potentially important opportunity in South Africa, since South Africa - and particularly Gauteng - is a water scarce region. The wastewater treatment industry in this region can be divided into two main categories of effluent: namely chemicals from coal and the metal recovery and finishing related to the mining industry. The focus of this work was to find a method to screen for potential uses of Clinoptilolite in these industries. The major effluent treatment issue in respect of the effluents from coal-based processes was identified to be the removal of oxygenate organics that are highly soluble in water, such as ethanol and acetone. This problem cannot be solved using vapour-liquid equilibrium based processes due to high energy costs, and liquid-liquid equilibrium based processes inherently introduce new contaminants into the wastewater. We therefore screened the zeolite for application in the removal of soluble organics via adsorption. The zeolite was found to be unsuitable for the adsorption of acetone and ethanol due to the preferential adsorption of water. As a result we tested the potential of the zeolite as a drying agent for ethanol and acetone. It was found that this zeolite could find application in the dehydration of ethanol, but not acetone. In effluent from the mining and metals based industries, heavy metals frequently occur and are usually toxic, such as lead, zinc and nickel. Such contaminated water must be disposed of as toxic waste, and this is very costly. Thus being able to selectively remove these metals allows for the possible recovery and recycling of a potentially valuable metal. If no application can be found for the recovered metal, the loaded zeolite would need to be disposed of as toxic waste, but the volume of this waste is significantly smaller than that of the original effluent due to the concentration effect of ion exchange processes. All of the metals were ion exchanged onto the zeolite successfully. The zeolite exhibited exceptional selectivity for the removal of lead, and reduced the concentration of lead in the water to levels below detection by Atomic Adsorption. The selectivity for the uptake of the metals in decreasing order was lead, zinc and lastly nickel. Therefore, provided the zeolite can be regenerated, it could be used for effluent treatment in mining activities that have traces of lead in the ore body, such as zinc and silver deposits, and in the battery industry. As a result of the work presented in this dissertation, a further project was undertaken to investigate the regeneration of the zeolite. Preliminary findings indicate that although it can be regenerated, the zeolite capacity decreases with each successive regeneration cycle. More work is required on regeneration to improve the lifespan of the zeolite.

A produção de ferroníquel está intimamente ligada à indústria siderúrgica. Todas as operações pirometalúrgicas pertencentes à rota de processo (calcinação, redução e refino) visam o melhor aproveitamento energético e a menor quantidade de impurezas no produto final. A etapa de refino pirometalúrgico produz escória rica em ferro e níquel, que normalmente é processada para recuperação destes metais e reinserção no processo, na própria etapa de refino ou no forno de redução, dependendo da quantidade de impurezas. Ensaios realizados com a escória granulada da Mineração Morro Azul mostram que é possível recuperá-los por processos físicos, de maneira similar à existente no local, porém com resultados superiores, mediante algumas alterações propostas para o circuito. / Ferronickel production is intimately connected to the steel industry. All pyrometallurgical operations which comprise the process route (calcining, smelting, refining) aim at better energetic usage and smaller amount of impurities in the final product. The pyrometallurgical refining stage produces slag rich in iron and nickel, which is usually further processed for metal recovery and reinsertion back into the process, in the refining or smelting stages, depending on the amount of impurities. A series of tests carried out on the Mineração Morro Azul granulated refining slag shows that it is possible to recover the metallic particles through physical processing, similarly to the existing facility, but with improved results due to some alterations proposed for the circuit.

Objectives: The objectives of this study were to establish the extent of dermal and respiratory exposure at selected locations at a South African platinum mine. The study included exposure to lead oxide fumes in an assay laboratory, nickel sulfate powder at a nickel sulfate crystallizer circuit and packing site and metallic copper dust whilst executing copper stripping. Methods: In an availability study, the dermal metal exposures were measured before, during and at the end of shifts. Dermal exposure samples were taken with GhostwipesTM from the dominant hand, wrist and forehead. Wipes were analyzed using Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES). Wipe samples were taken from surfaces in the workplace and analyzed according to NIOSH 9102, using ICP-AES. Personal and static inhalable dust samples were taken and the dust samples were analyzed according to NIOSH 7300, using ICP-AES. A validated questionnaire was used to evaluate self reported dermatological complaints of the workers at the fire assay laboratory and base metal recovery plant. Results: 100% of the nickel respiratory exposures and 36.8% of the lead respiratory exposures were above the occupational exposure limits (OEL). Copper respiratory exposure was present but less significant with a geometric mean of 0.071 mg m-3. All of the dermal lead measurements and the majority of the nickel and copper dermal measurements were below the limit of detection. Nickel surface contamination was the most significant and ranged between 8.430 μg cm-2 and 387.488 μg cm-2. Only 30% of the copper surface sample results were below the detection limit with a maximum surface sample of 14.41 μg cm-2. Lead surface contamination was low with 90% of the samples below the limit of detection. All of the workers at the nickel crystallizer circuit and packing site had a Dalgard score above 1.3 and therefore are at a higher risk of developing a skin disease. None of the workers at the copper stripping site had a significant Dalgard score and only one worker at the fire assay laboratory had a score above 1.3 and therefore is at a higher risk of developing a skin disease. Conclusions: Recommendations were made to lower the exposure to inhalable lead and nickel. The low lead dermal measurements may be due to adequate personal protective equipment usage and hygiene practices. Although the ethnicity of the workers may be the reason for the low incidence of dermatological complaints, the Dalgard score indicated that five workers are at risk of developing skin diseases. / Thesis (M.Sc. (Occupational Hygiene))--North-West University, Potchefstroom Campus, 2011

A produção de ferroníquel está intimamente ligada à indústria siderúrgica. Todas as operações pirometalúrgicas pertencentes à rota de processo (calcinação, redução e refino) visam o melhor aproveitamento energético e a menor quantidade de impurezas no produto final. A etapa de refino pirometalúrgico produz escória rica em ferro e níquel, que normalmente é processada para recuperação destes metais e reinserção no processo, na própria etapa de refino ou no forno de redução, dependendo da quantidade de impurezas. Ensaios realizados com a escória granulada da Mineração Morro Azul mostram que é possível recuperá-los por processos físicos, de maneira similar à existente no local, porém com resultados superiores, mediante algumas alterações propostas para o circuito. / Ferronickel production is intimately connected to the steel industry. All pyrometallurgical operations which comprise the process route (calcining, smelting, refining) aim at better energetic usage and smaller amount of impurities in the final product. The pyrometallurgical refining stage produces slag rich in iron and nickel, which is usually further processed for metal recovery and reinsertion back into the process, in the refining or smelting stages, depending on the amount of impurities. A series of tests carried out on the Mineração Morro Azul granulated refining slag shows that it is possible to recover the metallic particles through physical processing, similarly to the existing facility, but with improved results due to some alterations proposed for the circuit.