The South African mining industry is a major contributor to South Africa’s Gross Domestic product (GDP). The negative consequences of mining include toxic effluents from mineral processing and decanting streams, even after mine closure. Large volumes of Acid Mine Drainage (AMD) are expected to increase as the mining industry grows. Currently, biological treatment of mine waters are preferred to chemical methods, due to various advantages offered such as low operational cost and small environmental footprint. Biological treatment of AMD primarily rely on the activity of sulphate reducing bacteria which reduce sulphate to sulphide in the presence of organic matter thus allowing the precipitation of the metals and increase in pH. However, excess of sulphide remains in the system and if not removed, can be oxidized to sulphate. A sustainable AMD management plan could entail development of treatment technologies to remove total sulphur (sum of sulphur species) from the system. Production of elemental sulphur, which involves partial oxidation of sulphide, has been a recent subject of interest. The use of colourless sulphide oxidizing bacteria, especially Thiobacillus species has been widely reported. Six isolates of sulphide oxidizing microorganisms, of which 4 bacterial and 2 filamentous fungal species from a gold mine (Johannesburg, South Africa) were tested in this study to achieve partial oxidation of sulphide to sulphur. The microbial species were selected for high sulphide oxidation in the presence of carbon sources (glucose and lactate). Lysinicibacillus fusiformis was observed to be the most suitable microorganism for sulphide oxidation. In iiorder to investigate optimal conditions for sulphur recovery, L. fusiformis bacterial activity was tested under different conditions of pH and redox potential. It resulted that at a pH of 8 and Eh of -80mV up to 95% of sulphur was recovered. / Dissertation (MEng)--University of Pretoria, 2014. / tm2015 / Chemical Engineering / MEng / Unrestricted

In this thesis Antjie Krog’s ‘transformation trilogy’ consisting of three nonfiction texts, Country of My Skull (1998), A Change of Tongue (2003) and Begging to Be Black (2009) is analysed with specific focus on conceptions of identity in the trilogy. This is done from numerous angles, namely a postcolonial approach to the trilogy, an analysis of Krog’s exploration of an ‘African worldview’, an in-depth inquiry into Krog’s preoccupation with ‘race’ and the assertion that Krog is essentially asking the National Question. The overarching approach that is followed in the thesis is to read all three texts of the trilogy in conjunction with each other and to highlight examples of repetition, progression and/or change with regard to the issues that have been identified. The translated nature as well as the form and content of the transformation trilogy are singled out as important signposts for the interpretation of the trilogy. Several instruments are identified that will be used in analysing the texts, including the importance of questioning, the concept of gesturing as articulated by Terry Eagleton, and Krog’s pedagogical attitude. The trilogy is situated within postcolonial theory: the importance of postcolonial theory in general and whiteness studies specifically for the study of the trilogy is highlighted. Krog’s explicit and implicit references to colonialism and postcolonialism in the trilogy are discussed as an important postcolonial gesture. Another meaningful gesture is Krog’s exploration of what can be termed an ‘African worldview’. This exploration takes place through her incorporation of African orality in the trilogy, and through her extensive enquiry into African humanism. Her use of the term ubuntu is examined, as well as her explicit interaction with formal African philosophy. It is averred that Krog’s focus on an ‘African worldview’ necessitates a thorough investigation into the role of ‘race’ in the trilogy. The place that is given to ‘whiteness’ and ‘blackness’ in the trilogy is analysed in part by engaging with whiteness studies. The conclusion in reached that the concept of complicity is essential for correctly interpreting Krog’s preoccupation with ‘race’, and the way that her trilogy engages with international discourses on restitution is equally important. Finally all the above issues come together when it is stated that Krog is essentially asking the National Question: to whom does South Africa belong? Can ‘white’ people belong to the South African nation? Krog’s conceptions of identity are evaluated in this context and identity-as-becoming is identified as a central concept emerging in the course of the trilogy. / In hierdie proefskrif word Antjie Krog se ‘transformasie-trilogie’ bestaande uit drie niefiksie tekste, Country of My Skull (1998), A Change of Tongue (2003) en Begging to Be Black (2009) ondersoek met spesifieke fokus op konsepsies van identiteit in die trilogie. Dit vind vanuit verskeie invalshoeke plaas, naamlik ’n postkoloniale benadering tot die trilogie, ’n analise van Krog se verkenning van ’n ‘Afrikawêreldbeeld’, ’n indringende ondersoek na Krog se preokkupasie met ‘ras’, en die bewering dat Krog die Nasionale Vraagstuk betrek. Die oorkoepelende benadering wat in die proefskrif gevolg word, is om al drie tekste van die trilogie saam te lees en voorbeelde van herhaling, progressie en/of verandering ten opsigte van die geïdentifiseerde kwessies aan te toon. Die vertaalde aard asook die vorm en inhoud van die transformasie-trilogie word as belangrike rigtingswysers vir die interpretasie van die trilogie belig. Enkele instrumente word geïdentifiseer met behulp waarvan die tekste telkens ontleed word, insluitende die belangrikheid van vraagstelling, die konsep van gebare wat van Terry Eagleton ontleen is, en Krog se pedagogiese ingesteldheid. ’n Postkoloniale situering van die trilogie vind plaas waarin die belangrikheid van die teorie van postkoloniale studies in die breë en witheidstudies in besonder ten opsigte van die trilogie kortliks uitgelig word. Die wyses waarop Krog eksplisiet na kolonialisme en postkolonialisme verwys, word as ’n veelseggende postkoloniale gebaar bespreek. ’n Verdere belangrike gebaar is Krog se verkenning van wat as ’n ‘Afrikawêreldbeeld’ omskryf kan word. Hierdie verkenning vind plaas deur haar inkorporasie van Afrika-oraliteit in die trilogie, en deur haar uitgebreide ondersoek na Afrikahumanisme. Krog se gebruikmaking van die term ubuntu geniet aandag, asook haar eksplisiete interaksie met formele Afrikafilosofie. Daar word beweer dat Krog se fokus op ’n ‘Afrikawêreldbeeld’ ’n deeglike ondersoek na die plek van ‘ras’ in die trilogie noop. Die plek van ‘witheid’ en ‘swartheid’ in die trilogie word ontleed deur onder andere met witheidstudies in gesprek te tree. Uiteindelik word beweer dat die konsep van medepligtigheid noodsaaklik is om Krog se preokkupasie met ‘ras’ na behore te interpreteer, en daarmee saam is dit belangrik dat Krog deelneem aan internasionale diskoerse oor restitusie. Uiteindelik val al die genoemde kwessies saam wanneer beweer word dat Krog in wese die Nasionale Vraagstuk opper: aan wie behoort Suid-Afrika? Mag ‘wit’ mense tot die ‘Suid-Afrikaanse nasie’ behoort? Krog se konsepsies van identiteit word binne hierdie konteks beoordeel en identiteit-as-wordingproses word as ’n belangrike konsep geïdentifiseer. / Thesis (DLitt)--University of Pretoria, 2014. / tm2015 / Afrikaans / DLitt / Unrestricted

An indigenous mixed culture of bacteria collected from a Wastewater Treatment Plant (Brits, North West Province, South Africa), biocatalytically reduced Cr(VI) in the presence of As(III). Both the reduced chromium (Cr(III)) and the oxidised arsenic (As(V)) readily form amorphous hydroxides that can be easily separated or precipitated from the aqueous phase as part of the treatment process. Treatment of Cr(VI) and As(III) before disposal of wastewater is critical since both compounds are known to be carcinogenic and mutagenic at very low concentrations, and acutely toxic at high concentrations. Batch experiments were conducted to evaluate the rate of Cr(VI) reduction under anaerobic condition in the presence of its co-contaminant As(III) typically found in the groundwater and mining effluent. Results showed near complete Cr(VI) reduction under initial Cr(VI) concentrations up to 70 mg/L in a batch amended with 20 mg/L As(III). However, increasing Cr(VI) concentrations up to 100 mg/L resulted in the inhibition of Cr(VI) reduction activity. Further investigation was conducted in a batch reactor amended with 70 mg/L Cr(VI) concentration at different As(III) concentrations ranging from 5-70 mg/L to evaluate the effect of varying As(III) concentration on Cr(VI) reduction efficiency. Results showed that Cr(VI) reduction efficiency increased as As(III) concentrations increased from 5-40 mg/L. However, further increase in As(III) concentration up to 50 mg/L resulted in incomplete Cr(VI) reduction and decrease in Cr(VI) reduction efficiency. These results suggest that the rate of Cr(VI) reduction depends on the redox reaction of As(III) and As(V) with Cr(VI). Moreover, the inhibitory effect observed at high Cr(VI) and As(III) concentration may also be attributed to the dual toxicity effect of Cr(VI) and As(III) on microbial cell. From the above batch kinetic studies lethal concentration of Cr(VI) and As(III) for these strains was evaluated and established. Initial evaluation of the bacteria using 16S rRNA partial sequence method showed that cells in the mixed culture comprised predominantly of the Gram-positive species: Staphylococcus sp., Enterobacter sp., and Bacillus sp. The biokinetic parameters of these strains were estimated using a non-competitive inhibition model with a computer programme for simulation of the Aquatic System “AQUASIM 2.0”. Microbial reduction of Cr(VI) in the presence of As(III) was further investigated in continuous-flow bioreactors (biofilm reactor) under varying Cr(VI) loading rates. The reactor achieved Cr(VI) removal efficiency of more than 96 % in the first three phases of continuous operation at lower Cr(VI) concentration ranging from 20-50 mg/L. However, 20 % decrease in Cr(VI) removal efficiency was observed as Cr(VI) concentration increase up to 100 mg/L. The reactor was able to recover from Cr(VI) and As(III) overloading phase after establishing the resilient nature of the microorganism. Similarly to the batch reactor studies the overall performance of the reactor also demonstrated that the presence of As(III) greatly enhance Cr(VI) reduction in a bioreactor. This was evident by near complete removal of Cr(VI) concentration up to 50 mg/L. The basic mass balance expressions on Cr(VI) along with the non-competitive inhibition model were used to estimate the biokinetic parameters in the continuous flow bioreactor system. Cr(VI) reduction efficiency along the longitudinal column was also evaluated in this study. Results showed that Cr(VI) efficiency increased as Cr(VI) concentration travels along the longitudinal column. Other important factors such as oxygen and pH during biological Cr(VI) reduction in the presence of As(III) oxidation were also evaluated. / Dissertation (MEng)--University of Pretoria, 2014. / tm2015 / Chemical Engineering / MEng / Unrestricted

This work details research on the semi-continuous copolymerisation of tetrafluoroethylene (TFE) and hexafluoropropylene (HFP) in aqueous medium using different monomer ratios. A main objective of this dissertation was to understand the influence of changing parameters, such as monomer feed ratio and initiator concentration, on the properties of the polymer. The copolymerisation of TFE and HFP was carried out in ultra-pure water using a 300 mL Parr 316 stainless steel high-pressure reactor. The experiments were done at 85 and 100 °C with pressures in the range of 11 - 20 bar using ammonium persulfate as the free radical initiator. Different monomer feed compositions were studied: 10, 19, 20, 22, 26, 38, 39, 40, 44 and 46 mol % HFP. The pressure of the reaction was found to be dependent on the amount of HFP in the feed stream. The following techniques were used to provide a comprehensive understanding of the as-polymerised FEP: FTIR, TGA-FTIR, SEM, DSC, XRD and 19F NMR. Solid state 19F NMR spectroscopy was used to elucidate the structure and determine the composition of FEP copolymers. The results revealed a successful incorporation of the HFP monomer in the copolymers by peaks at -67.44, -70.46 and -112.10 ppm due to –CF3 and –CF2 units of the HFP monomer and also by a peak at -183.42 ppm due to –CF unit of the HFP monomer. Results from DSC indicated that the melting temperature (determined by the highest peak of the first heating observed in the thermograms) and heat of fusion decreased from 324.28 to 278.71 °C and 73.05 to 36.60 J/g respectively as the mol % HFP increases in the copolymer. The XRD analysis showed that the FEP polymers are semi-crystalline with increase in the amorphous region as the concentration of HFP increases from 0.96 to 3.80 mol % HFP. SEM analysis showed that the FEP samples consists of spheres and rods at low HFP concentration in the monomer feed and spheres at high HFP. The TG analysis revealed that the copolymers are thermally stable up to 460 °C; after that they start to decompose. The decomposition can be resolved into a two-step process by taking the first derivative of the TGA curve. The evolved gas analysis using FTIR indicated that the first step corresponded to the elimination of HFP species (weak peak intensity at 1391 and 1790 cm-1 corresponding to C-F of CF3 in C3F6 and C=C of C2F6) in addition to strong bands at 1032, 1184 and 1328 cm-1 attributed to the CF2 moiety. The second corresponded to the degradation of the PTFE backbone chain to monomer component or unit. / Dissertation (MSc)--University of Pretoria, 2014. / tm2015 / Chemical Engineering / MSc / Unrestricted

Liquid fuel lubricity testing is known to be sensitive to the humidity of the surrounding atmosphere. The effect reported does however not seem to be universal for all diesel types according to available literature. This study was limited to the use of n-hexadecane as base fluid with addition of between 100 - 2000 ppm of palmitic acid (PA) as lubricity enhancer. The fuel spectrum was kept simple to allow a more fundamental approach by limiting the extent of possible chemical reactions. Both wear and seizure load testing were performed. The effect of water on both tests was found to be:  Wear and friction increased with higher soluble water content. Water therefore interferes with the action of the lubricating additive leading to decreased performance.  It is known that hydroxyl groups, from dissociative chemisorption of water, act as active sites for adsorption. It is however postulated that the associative chemisorption and/or physisorption of water interferes by either reducing the active site availability or reducing activity to ligand exchange.  No iron oxyhydroxides (FeOOH) were detected on the wear scars or tracks using Raman spectroscopy. The adsorbed water therefore likely only interact with the surface due to their low concentrations (10 ~ 50 ppm).Liquid fuel lubricity testing is known to be sensitive to the humidity of the surrounding atmosphere. The effect reported does however not seem to be universal for all diesel types according to available literature. This study was limited to the use of n-hexadecane as base fluid with addition of between 100 - 2000 ppm of palmitic acid (PA) as lubricity enhancer. The fuel spectrum was kept simple to allow a more fundamental approach by limiting the extent of possible chemical reactions. Both wear and seizure load testing were performed. The effect of water on both tests was found to be:  Wear and friction increased with higher soluble water content. Water therefore interferes with the action of the lubricating additive leading to decreased performance.  It is known that hydroxyl groups, from dissociative chemisorption of water, act as active sites for adsorption. It is however postulated that the associative chemisorption and/or physisorption of water interferes by either reducing the active site availability or reducing activity to ligand exchange.  No iron oxyhydroxides (FeOOH) were detected on the wear scars or tracks using Raman spectroscopy. The adsorbed water therefore likely only interact with the surface due to their low concentrations (10 ~ 50 ppm). For wear testing the following additional observations were made:  The electric contact resistance (ECR) took longer to increase at higher soluble water content, for all PA concentrations. The equilibrium values attained were also lower, when values were within the measurement range. This again highlights the reduced lubricity performance at higher soluble water content.  Wear scar appearance and colour were uniquely affected at each concentration of PA  Similar trends were observed at 60 °C and 80 °C. At the higher temperature:  Wear scar diameters increased.  Friction coefficients decreased and had less variance.  ECR values were similar, but took longer to increase to a steady value. For seizure load testing the following additional observations were made:  At higher water content, the oscillation-stroke on the test machine used tended to deviate more, before the actual seizure point was reached.  The effects of soluble water were more noticeable at lower PA concentrations. / Dissertation (MEng)--University of Pretoria, 2014. / tm2015 / Chemical Engineering / MEng / Unrestricted

The processing of minerals containing tantalum and niobium is a challenge that has most modern researchers focused on optimising the processes that have already reached scientific maturity. Ore digestion in aqueous mixtures of sulfuric and hydrofluoric acid, followed by selective liquid-liquid extraction, is the method of choice for recovery of tantalum and niobium from the parent minerals. As this method has significant environmental and practical drawbacks, there is a need for a new process to beneficiate these minerals. The Advanced Metals Initiative (AMI) programme of the Department of Science and Technology (DST) proposes that no tantalum or niobium values should leave South Africa without some degree of local beneficiation. A significant strategic advantage may be gained from developing a process which is economically viable and more environmentally friendly. This thesis proposes a technology which would circumvent many of the drawbacks of wet chemical systems. The proposed technology would use anhydrous fluorinating gases (HF(g) and F2) to convert the oxidic minerals to oxyfluorides and/or fluorides, followed by thermal separation. Since little is known about the reaction between the fluorinating agents mentioned and the ores containing Ta/Nb, a detailed study of these reactions and possible products for the current concept is realised. Oxyfluorides are the most probable intermediates during the fluorination process. As part of the research, the most likely oxyfluoride intermediates were synthesised. The details of their spectral and crystallographic properties are discussed. Their thermal properties were investigated; this showed that oxyfluorides can be used to develop a thermal separation process in either the high temperature (600-900 ºC) or low temperature region (150-200 ºC). Thermogravimetric analysis also suggests a difference in the decomposition pathways for niobium and tantalum oxyfluorides. Dioxyfluoride is the most stable of the oxyfluorides and is a necessary byproduct, regardless of which other oxyfluoride is synthesised, and may occur even during the synthesis of the pentafluorides. It was therefore considered imperative to understand the decomposition kinetics of the dioxyfluoride compounds, to calculate the decomposition activation energies, and to construct physical decomposition models for these compounds. By means of mechanistic methods, it is shown that the decomposition of the oxyfluorides occurs via Avrami-Erofeev A2 or A3 models and that for this process the activation energy for TaO2F (320 kJ.mol-1) is roughly double that for NbO2F (156 kJ.mol-1). Once the characterisation of the possible reaction intermediates had been completed, the reaction and interaction of F2 and anhydrous HF with pure metal oxides of Ta and Nb were investigated. To this end, both thermogravimetric and differential scanning calorimetry were employed. Thermodynamic calculations indicated that for both these fluorinating agents, the corresponding pentafluorides were the preferred (indeed the only) reaction products, though the experimental results showed that a whole range of oxyfluorides form. The data collected showed no evidence of a two-step mechanism, as has been observed for Nb2O5, for the fluorination of Ta2O5 with elemental fluorine. However, in both cases the rate-limiting step is governed by the contracting volume (R3) mechanistic. The activation energy for the Ta2O5 + F2 reaction is 63-67 kJ.mol-1, and leads to the formation of the pentafluoride without detectable oxyfluoride formation. A single ore containing tantalum and niobium was selected for study and characterised prior to evaluating its reaction with the chosen fluorinating gases. As the reaction products have a substantially more complex matrix, they were shown to be far less self-evident than in the studies conducted on the pure oxides. Nevertheless, it is shown that separation using this methodology is indeed feasible. Aided by techniques such as SEM and ICP-OES, it could be shown that physical and chemical changes occur in the mineral during the fluorination reaction. The concluding chapter considers the information assimilated during this study and provides likely scenarios for a process based on the selective volatilisation of tantalum and niobium fluorides and oxyfluorides. Two likely processes are postulated, the first one involving partial fluorination and sublimation, the second one complete fluorination to the pentafluoride. / Thesis (PhD)--University of Pretoria, 2014. / tm2015 / Chemical Engineering / PhD / Unrestricted

The Council for Scientific and Industrial Research (CSIR) is developing a novel process to produce titanium metal at a lower cost than the current Kroll process used commercially. The technology initiated by the CSIR will benefit South Africa in achieving the long-term goal of establishing a competitive titanium metal industry. A bubble column reactor is one of the suitable reactors that were considered for the production of titanium metal. This reactor will be operated with a molten salt medium. Bubble columns are widely used in various fields of process engineering, such as oxidation, hydrogenation, fermentation, Fischer–Tropsch synthesis and waste water treatment. The advantages of these reactors over other multiphase reactors are simple construction, good mass and heat transfer, absence of moving parts and low operating costs. High heat transfer is important in reactors when high thermal duties are required. An appropriate measurement of the heat transfer coefficient is of primary importance for designing reactors that are highly exothermic or endothermic. An experimental test facility to measure wall heat transfer coefficients was constructed and operated. The experimental setup was operated with tap water, heat transfer oil 32 and lithium chloride–potassium chloride (LiCl–KCl) eutectic by bubbling argon gas through the liquids. The column was operated at a temperature of 40 oC for the water experiments, at 75, 103 and 170 oC for the heat transfer oil experiments, and at 450 oC for the molten salt experiments. All the experiments were run at superficial gas velocities in the range of 0.006 to 0.05 m/s. Three heating tapes, each connected to a corresponding variable AC voltage controller, were used to heat the column media. Heat transfer coefficients were determined by inducing a known heat flux through the column wall and measuring the temperature difference between the wall and the reactor contents. In order to balance the system, heat was removed by cooling water flowing through a copper tube on the inside of the column. Temperature differences between the column wall and the liquid were measured at five axial locations. A mechanistic model for estimating the kinematic turbulent viscosity and dispersion coefficient was developed from a mechanism of momentum exchange between large circulation cells. By analogy between heat and momentum transfer, these circulation cells also transfer heat from the wall to the liquid. There were some challenges when operating the bubble column with molten salt due to leakages on the welds and aggressive corrosion of the column. The experimental results were obtained when operating the column with water and heat transfer oil. It was found that the heat transfer coefficient increases with superficial gas velocity. The values of the heat transfer coefficient for the argon–water system were higher than those for the argon–heat transfer oil system. The heat transfer coefficients were also found to increase with an increase in temperature. Gas holdup increased with the superficial gas velocity. It was found that the estimated axial dispersion coefficients are within the range of those reported in the literature and the ratios of dispersion coefficients are in agreement with those in the literature. The estimated kinematic turbulent viscosities were comparable with those in the literature. / Dissertation (MEng)--University of Pretoria, 2014. / tm2015 / Chemical Engineering / MEng / Unrestricted

Concentrations of diesel particulate matter (DPM) and polycyclic aromatic hydrocarbons (PAHs) in platinum mine environments are likely to be higher than in ambient air due to the use of diesel machinery in confined environments. PAHs may be present in gaseous or particulate phases each of which have different human health impacts due to their ultimate fate in the body. The sampling of both phases was made possible by means of small, portable denuder sampling devices consisting of two polydimethylsiloxane multi-channel traps connected in series and separated by a quartz fibre filter. Thermal desorption coupled with two dimensional gas chromatography with mass spectrometric detection (TD-GCxGC-ToFMS) was employed to analyse samples from three different platinum mines. The underground environments revealed that PAHs were predominantly found in the gaseous phase with naphthalene and mono-methylated derivatives being detected in the highest concentrations ranging from 0.15 – 8.73 μg.m-3. Similarly higher gas phase PAH loading was found in the Daspoort Tunnel. The particle bound PAHs underground were found in the highest concentrations at the Load Haul Dump (LHD) vehicle exhaust with dominance of fluoranthene and pyrene and concentrations ranged from 0.52-109.60 ng.m-3. This work highlighted the need to characterise both gaseous and particulate phases of PAHs in order to assess occupational exposure and demonstrated the successful application of these portable denuders in the mining environment. / Dissertation (MSc)--University of Pretoria, 2014. / tm2015 / Chemistry / MSc / Unrestricted

The food-away-from-home (FAFH) sector in South Africa has continued to increase in popularity. This is illustrated by the increased presence of FAFH in the diets of the country’s citizens. However, the sector in South Africa remains un-researched with regard to understanding household preferences and the composition of consumer expenditure. This study analyses the effects of income and socio-demographic variables on FAFH expenditure for South Africa. These results will be useful to the foodservice sector and policy makers in order to identify potential customers, respond to current customers’ changing demands and develop marketing and operational strategies, and address important nutrition and health consequences, respectively. Data from Income and Expenditure Surveys (IESs) of 2005/2006 and 2010/2011 of StatsSA (Statistics South Africa) were used to estimate the responsiveness of household FAFH expenditure in South Africa to income and a number of socio-demographic variables. The IESs contain a large number of households with zero FAFH expenditure observations which means that the use of ordinary least squares (OLS) would result in biased and inconsistent results. Furthermore, omitting households with zero FAFH expenditure, and applying OLS reduces the sample size and consequently the efficiency of estimation. Previous studies made use of the univariate and multivariate an adjustment factor and a two-stage process where the second stage is a Generalised Method of Moments (GMM) Within-Group estimator. The majority of studies suggest that double-hurdle models are appropriate for applications where zero expenditure observations are due to abstention or economic factors. The double-hurdle model is more flexible than the tobit model because it allows for the possibility that zero and positive values are generated by different mechanisms. The model used assumes independence between the two hurdles. The first hurdle determines the probability of purchasing FAFH, while the second hurdle determines the amount spent on FAFH. The double-hurdle models estimated for the IESs of 2005/2006 and 2010/2011 illustrate that households headed by younger White females with a small household size and living in an urban settlement are most likely to purchase FAFH. However, households headed by younger White males with a small household size and living in an urban formal settlement are likely to have the highest expenditure on FAFH. An increase in income positively affects the decision to buy FAFH and the amount spent by participating households. The APE (average partial effect) was calculated for the income variable. The APE determines the probability of purchasing FAFH and the income elasticities (conditional and unconditional) of expenditure on FAFH by households. The estimated conditional income elasticity of expenditure is 0,27 and the unconditional income elasticity of expenditure is 0,611 for the IES of 2005/2006. While the estimated conditional income elasticity is 0,171 and the unconditional income elasticity is 0,472 for the IES of 2010/2011. The probability of purchasing FAFH is 0,0905 and 0,0568 for the IESs of 2005/2006 and 2010/2011 respectively. The income elasticity of expenditure on FAFH is inelastic and FAFH is a normal good for the average South African household. The small size of the participation elasticities mean that growth in the FAFH sector will be driven by households with existing expenditure. Future studies should focus on per capita FAFH expenditure, the effect of the lifestage of the individual, rather than age, on FAFH expenditure, FAFH expenditure for different meals (breakfast, lunch and dinner) and facility types (quick- and full-service restaurants) and the effect of income and socio-demographic factors on FAFH expenditure on different food types (for example beef, chicken, lamb, potatoes and salads). / Dissertation (MScAgric)--University of Pretoria, 2014. / tm2015 / Agricultural Economics, Extension and Rural Development / MScAgric / Unrestricted

The synthesis and structure elucidation of fourteen novel Fischer ethoxy- and amino carbene complexes of molybdenum and chromium metals of the type [(CO)3L2M=C(X)R] were performed. Substitution of the parent pentacarbonyl complex [(CO)5M-C(OEt)(R)]; M = Mo, Cr; R = 2-thienyl, 2-furyl; with mono- and bidentate phosphine ligands yielded the corresponding tetracarbonyl complexes [(CO)4(PR’3)M-C(OEt)R] with M = Mo, Cr, R = 2-thienyl, 2-furyl and R’ = Ph, Cy or tricarbonyl complexes [(CO)3(DPPE)Mo-C(OEt)(2-furyl)], respectively. Aminolysis of these novel complexes resulted in substitution of the ethoxy substituent with an amino group. Full characterisation of these novel complexes included infrared spectroscopy, NMR (1H, 13C, 31P) spectroscopy, x-ray crystallography and mass spectral analyses. From the characterisation data, it was found that the cis isomer was dominant for the tetracarbonyl carbene complexes whereas the mer isomer was favoured in most cases for the tricarbonyl carbene complexes. Structural elucidation of nine of the novel complexes was confirmed with x-ray crystallography. The amino carbene complexes showed preference for a syn conformation of the oxygen atom of the furyl moiety and the nitrogen atom of the amino moiety in the crystal form. The ethoxy carbene complexes showed a preference for the anti conformation in the crystal form. The NMR analysis showed that resonance between the metal-carbene carbon-heteroatom stabilisation is more prevalent in the case of the amino carbene complexes. DFT calculations were performed for eleven of these complexes and their isomers. The infrared stretching modes were calculated and compared to experimental data. The HOMO and LUMO position and energy gaps were calculated. It was observed that the HOMO in all calculated complexes lay on the metal centre, while the LUMO was centred on the carbene carbon. It was found that the HOMO-LUMO gap was larger for the amino Fischer carbene complexes than for the ethoxy Fischer carbene complexes. From frontier orbital considerations, it is concluded that ligand substitution of carbonyls by phosphines as well as carbene substituent alterations does not seem to improve the reactivity of the novel complexes of this study particularly for the potential application as metathesis catalysts. The performed DFT calculations, in the future, can help determine which type of catalytic reactions these fourteen complexes would be most effective for. / Dissertation (MSc)--University of Pretoria, 2014. / tm2015 / Chemistry / MSc / Unrestricted