Zincor's average zinc recovery was 90.29 % (for the period of 1 January 2009 to 30 September 2011), which was well below the industry standard of 96 %. Due to limitations in Zincor's iron removal technology, the maximum achievable recovery was 94 %. The zinc loss through the iron residue was the second biggest contributor to the overall zinc losses, so that there was much room for improvement. The calcine used for neutralisation in the Iron Removal Stage contained a portion of insoluble zinc ferrite. The insoluble zinc loss through the iron residue was associated with the presence of the insoluble zinc ferrite, as well as the phenomenon of coating of unleached neutralising agent by iron precipitate. The soluble zinc loss was a function of the dewatering characteristics of the precipitate. The work included the evaluation of alternative neutralising agents to supplement or replace calcine, as well as the implementation of a seed recycle. A review of literature found that the use of an alternative neutralising agent that contained little or no zinc could potentially reduce the insoluble portion of the zinc loss. Secondly, the presence of seed could potentially reduce both the soluble and insoluble zinc losses by promoting agglomeration growth and providing additional surface area for precipitation to occur (thereby reducing coating of zinc-rich neutralising agents). The laboratory work evaluated a number of alternative neutralising agents, but focused on the use of DRC oxide and limestone for neutralisation. These were evaluated separately and in combination, with and without a seed recycle.

South Africa has large low-grade coal reserves. With the prospect of expanding its coal demands for exports and power generation, it is important that the beneficiation and transport of coal in the country are economical. The current mode of transporting coal has some drawbacks, which include inefficient rail infrastructure, long distances, and several environmental concerns related to air pollution, water pollution, and traffic risks. It is, therefore, important to investigate efficient means of coal transportation, which will also reduce environmental impacts. The transport of highly concentrated coal-water slurries through pipelines has attracted the attention of many researchers as an efficient and economical means of fine coal utilization. The primary objectives of this study are to investigate the importance of surface charge, solids concentration and particle size on the stability and rheological behaviour of Witbank coal. This work was carried out to arrive at a sounder discernment of the function of dispersion addition on coal-water mixtures rheology and stability.

SYNOPSIS Energy/power input in a flotation cell is an important parameter which, if optimised, can increase the flotation rate. The optimum energy/power input within a flotation cell is still a matter of conjecture and there is a need for a better understanding of the effect of energy input on flotation kinetics. This study investigates the effect of energy/power input on flotation kinetics in an oscillating grid flotation cell (OGC). The OGC decouples the processes of solid suspension and bubble generation as well as producing relatively isotropic and homogeneous turbulence with zero mean flow. Due to this, oscillating grids provide a potentially ideal environment for investigating the effects of energy input on flotation kinetics, which cannot be achieved in a mechanical flotation cell. The first objective of this thesis was to determine the effect of energy/power input on the flotation kinetics of sulphide minerals (galena, pyrite & pentlandite) and oxide minerals (apatite & hematite) in a laboratory scale oscillating grid flotation cell. The second objective was to compare the results from the laboratory OGC to comparative studies in the flotation literature and to fundamental models for particle-bubble contacting. The third objective was to determine whether the experimental results from the laboratory OGC are consistent with those from a pilot-scale OGC operating on a platinum ore. Galena, pyrite, pentlandite (-150 μm), apatite (-650 μm) and hematite (-75 μm) were floated in the laboratory OGC at energy inputs from 0.1 to 5.0 W/kg, using 0.13, 0.24, 0.58 and 0.82 mm bubble sizes (d₁₀), and at three collector dosages. Platinum ore (-75 μm) was floated in the pilot-scale OGC at energy inputs from 0 to 2.5 W/kg, using 0.71 and 1.47 mm bubble sizes (d₁₀). The effect of energy input on flotation kinetics was interpreted through trends in experimental flotation rate constants, simulated flotation rate constants and attachment-detachment flotation rate constants. Here, simulated flotation rate constants were calculated using a literature fundamental model for flotation in turbulent systems. This model is based on suitable expressions for the collision frequency, collision efficiency, attachment efficiency and stability efficiency, Attachment-detachment flotation rate constants were calculated using a kinetic model which allows for the two separate processes of bubble-particle collision/attachment and detachment. This model is based on kinetic expressions using empirical correlations for the attachment and detachment rate constants. Experimental flotation results show that the effect of energy input on the flotation rate is strongly dependent on the particle size and particle density and less dependent on bubble size and contact angle. Flotation rates generally increase with increasing particle size, decreasing bubble size and increasing contact angle, as is commonly found in the literature. Increasing energy input generally leads to an increase in the flotation rate for fine particles, an optimum flotation rate for intermediate particles and a decrease in the flotation rate for coarse particles. The optimum in the flotation rate for minerals with higher density is at a lower energy input than that for lower density minerals. The changes (increases/decreases) in the flotation rate with increasing energy input are very large for most of the conditions, indicating that this is an important parameter in flotation. Pilot scale results generally support the trends observed in the laboratory OGC. These findings are attributed to the effect of energy/power input on bubble-particle collection which is a balance between two competing effects, those of bubble-particle collision/attachment and those of bubble-particle detachment. Increasing energy input generally leads to significant increases in the flotation rate of fine particles, due to increased bubble-particle collision/attachment. Increasing energy input generally leads to an optimum flotation rate for intermediate particles, due to a combination of increased bubble-particle collision/attachment and detachment. For coarse particles, increasing energy input leads to significant increases in bubble-particle detachment. The relationship between the flotation rate and energy input is often described as k  ɛᴺ, in the absence of significant bubble-particle detachment. The typical values of N are in the range of 0.44-0.75 for theoretical studies and 0.7-1 for experimental studies. The values of N found in the current study are in the range of 0.7-1, which suggests that bubbleparticle collision/attachment has a stronger dependence on energy input than theory suggests. Simulated flotation results for fine particles compare well to the experimental data in terms of both trends and magnitude. This suggest that the turbulent collision model used is appropriate for fine particles. For intermediate particles there are differences between the simulated flotation rate constants and the experimental data, primarily in terms of trends. For coarse particles there are very large differences between simulated flotation rate constants and the experimental data. This is attributed to under prediction of the collision frequency/efficiency and incorrect prediction of the stability efficiency. Here, the stability efficiency is considered to be under predicted at low energy inputs and over predicted at high energy inputs. This suggests that the stability efficiency has a much stronger dependence on energy input than theory suggests. Attachment-detachment results show that the attachment rate constant has a stronger dependence on energy input than theory suggest, supporting finding from the experimental results and simulated results for coarser particles. In addition, the detachment rate constant has a much stronger dependence on energy input than theory suggests, supporting findings from both the experimental and simulated results. Based on the objectives of this study and literature reviewed, the following hypotheses were made at the outset 1) Increasing energy/power input will increase the rate of flotation of fine particles but will result in an optimum for intermediate and coarse particles. The position of this optimum will depend on the particle density, bubble size and contact angle. 2) Fundamental models based on the RMS turbulent velocity will be appropriate for describing flotation kinetics as turbulence in the oscillating grid cell is relatively homogeneous and isotropic and 3) Trends in flotation results for a laboratory and pilot-scale oscillating grid flotation cell will be comparable as the distribution of turbulence in OGCs at equivalent specific power inputs is scale independent. Hypothesis 1 was found to be valid for both fine and intermediate particles, but for coarse particles increasing energy input resulted in sharp decreases in the flotation rate. In addition, the increase in the flotation rate with increasing energy input was found to be more dependent on the particle size and particle density than the bubble size and contact angle. Hypothesis 2 was found to be valid for fine particles but not for intermediate or coarse particles. Here, it was found that the processes of bubble-particle collision/attachment and detachment have a stronger dependence on energy input than theory suggests. Hypothesis 3 was supported by general trends in results for the laboratory and pilot-scale oscillating grid flotation cells, but was not convincingly demonstrated.

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An 18-day balance study was designed to test the hypothesis that the use of oral contraceptive agents would change the metabolic balance of copper and zinc in young women. The subjects were divided into two treatment groups based on the use or non-use of oral contraceptive agents, The mean age was 21 years and 6 months for the non-oral contraceptive group and 21 years and 2 months for the oral contraceptive group. The mean weight was 57.2 kg for the non-oral contraceptive group and 59.7 kg for the group on oral contraceptive therapy. The study was composed of three 6-day periods. The subjects of both groups consumed identical diets for the three experimental periods. The diet contained approximately 2 mg of copper, 9 mg of zinc, 50 g of protein, 181 mg of cholesterol, and 2000 kcal per day. The first experimental period served as an adjustment period with the latter two periods serving as the balance periods. Subjects were given a multi-vitamin supplement daily. All urine and feces were collected and assayed for copper, zinc, and nitrogen. Food samples were measured for content of copper, zinc, and nitrogen. Blood samples were taken and the plasma fraction analyzed for copper, zinc, and cholesterol content. Urinary copper was measured as an organic chelate by atomic absorption spectrophotometry. Copper and zinc content of the other samples were assayed in wet ashed samples by atomic absorption spectrophotometry. Food and fecal nitrogen was assayed by Kjeldahl analysis. Urine nitrogen and creatinine was measured by standard automated techniques. No significant differences were found in the metabolic balances of copper, zinc, and nitrogen. Oral contraceptive users were found to have significantly (p<0.01) higher plasma cholesterol and copper levels, but plasma zinc concentrations were not significantly different. No difference was found in hemoglobin or hematocrit for the two groups. The urinary excretion of zinc was similar for the two groups. The excretion of copper and creatinine was significantly (p<0.01) higher for the oral contraceptive group. The urinary and fecal excretion of copper and zinc was not significantly different for the two groups. While the balance data was not different for the two groups, it is of interest that both groups maintained negative balance states on intakes similar to projected intakes for the general population. This indicated that both groups needed more copper and zinc than they received, It therefore appears that consideration should be given to a possible suboptimal nutritional state existing for copper and zinc nutrition for at least this sex-age group. / Ph. D.

The Old Hickory is the largest of a series of Pliocene (?) age heavy mineral sand deposits in Virginia and North Carolina. The high density of heavy minerals allows for selective concentration during transport and deposition. Under the right conditions, placers of considerable size can be formed. The elliptically shaped ore body of the Old Hickory Deposit extends in a North - South direction and is approximately 13 km (8 miles) long and up to 2.5 km (1.5 miles) wide, with an average thickness of 6.5 m (20 feet). The deposit lies along the Fall Zone, where a thin wedge of Cenozoic Coastal Plain sediments unconformably overlies the older rocks of the Piedmont. The principal minerals of economic interest found in the heavy mineral sands at the site are ilmenite (FeTiO₃), leucoxene (Fe<SUB>2-x</SUB>Ti<SUB>3+x</SUB>O<SUB>9+x/2</SUB>) where x is less than or equal to 2, rutile (TiO₂), and zircon (ZrSiO₄). An important focus of this study is the alteration of ilmenite by leaching away of iron, which results in enrichment in titanium. Titanium metal is highly valued for its light weight and high strength. In terms of total economic value, however, the use of titanium dioxide pigments for paint, coated paper, and other products is far more important. As the value of the ore is heavily dependent on the titanium content, the weathering process is a matter of considerable interest to the mineral industry. Analysis of ilmenite grains using reflected light microscopy revealed a wide range of alteration textures. Quantitative analysis and mapping of trace elements showed altered areas with enrichment in Ti and depletion in Fe, Mn, Mg, and Cr. It is believed that the weathering process took place in a reducing environment prior to final deposition according to the reaction: Fe²⁺TiO₃ + 2H⁺ --> Fe²⁺ (aq) + TiO₂ + H₂O Reducing environments are found in water-logged soils such as floodplains and other low-lying areas. Repeated cycles of burial and exhumation during transport would have created conditions ideal for the removal of iron from the ilmenite. / Master of Science

Yes / We present here a quantification of the sorption process and molecular conformation involved in the attachment of bacterial cell wall lipopolysaccharides (LPSs), extracted from Escherichia coli, to silica (SiO2) and alumina (Al2O3) particles. We propose that interfacial forces govern the physicochemical interactions of the bacterial cell wall with minerals in the natural environment, and the molecular conformation of LPS cell wall components depends on both the local charge at the point of binding and hydrogen bonding potential. This has an effect on bacterial adaptation to the host environment through adhesion, growth, function, and ability to form biofilms. Photophysical techniques were used to investigate adsorption of fluorescently labeled LPS onto mineral surfaces as model systems for bacterial attachment. Adsorption of macromolecules in dilute solutions was studied as a function of pH and ionic strength in the presence of alumina and silica via fluorescence, potentiometric, and mass spectrometry techniques. The effect of silica and alumina particles on bacterial growth as a function of pH was also investigated using spectrophotometry. The alumina and silica particles were used to mimic active sites on the surface of clay and soil particles, which serve as a point of attachment of bacteria in natural systems. It was found that LPS had a high adsorption affinity for Al2O3 while adsorbing weakly to SiO2 surfaces. Strong adsorption was observed at low pH for both minerals and varied with both pH and mineral concentration, likely in part due to conformational rearrangement of the LPS macromolecules. Bacterial growth was also enhanced in the presence of the particles at low pH values. This demonstrates that at a molecular level, bacterial cell wall components are able to adapt their conformation, depending on the solution pH, in order to maximize attachment to substrates and guarantee community survival. / The authors thank the Libyan Ministry of Education for financial support during the experimental study. We thank the EPSRC funded consortium “Hard-soft matter interfaces: from understanding to engineering” (EP/I001514/1) for financial support. Emily Caseley, who assisted in the preparation and characterization of AmNS-LPS particles as an MRC Confidence in Concept funded postdoctoral researcher at the University of Bradford, (MC_PC_16038).

Master of Science / Department of Animal Sciences and Industry / Christopher Reinhardt / Crossbred bull calves at high risk for morbidity (n = 190; BW = 159 ± 68 kg) were received at a commercial stocker operation to evaluate the effects of meloxicam administered at the time of castration on performance and health through d 30 post-arrival. Calves were assigned randomly to receive either a whey-powder placebo (CON), 0.5 mg/kg BW meloxicam (LOW), or 1.0 mg/kg BW meloxicam (HIGH) administered orally. Calves were vaccinated, knife-castrated, and received experimental treatments on d 0. Meloxicam had no effect on ADG (P ≥ 0.63), morbidity (P = 0.66), or mortality (P = 0.62). A second study was conducted using crossbred calves from the southeastern US and Mexico (n = 472; BW = 227 ± 45 kg) to evaluate effects of an injectable trace-mineral solution administered at time of arrival at a commercial stocker operation on animal performance, health, and serum concentrations of Cu, Mn, Se, and Zn on d 0 and d 45. Calves were assigned randomly to receive saline (CON; 1.0 mL/45 kg BW) or injectable trace mineral (ITM; 1.0 mL/45 kg BW) on d 0. Average daily gain from d 0 to d 42, overall ADG from d 0 to d 139, mortality, and morbidity were not different (P ≥ 0.31) between treatments. Calves originating from the Southeastern US had greater (P < 0.01) overall ADG from d 0 to 139. There were no source effects (P ≥ 0.21) on initial serum mineral concentrations for Mn or Zn; however, cattle originating in Mexico had lesser serum Cu (P < 0.01) and cattle originating in the Southeastern US tended to have lesser serum Se (P = 0.06). On d 45, there were no treatment differences (P ≥ 0.20) in serum concentrations of Cu, Mn, or Zn but cattle that received ITM tended (P = 0.09) to have elevated serum Se concentrations compared to those that received CON.