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The aim of this investigation was to extend the knowledge of the bacterial leaching of copper and zinc sulphides into the area of nickel sulphide leaching. By far the major portion of both theoretical and practical expertise which is available in the field of bacterial leaching is based on the treatment of copper and zinc sulphides. As yet there is little information available on the bacterial leaching of nickel sulphides to meet the growing interest in this field both in South Africa and elsewhere. To a large degree, it was necessary to start from basic principles in this novel extension of bacterial leaching technology so that the work covers a fairly wide field in general rather than one particular aspect in detail. A strain of 'nickel adapted' Thiobacillus ferrooxidans was isolated from the tailings dam of a disused nickel mine. The growth characteristics of this strain were studied in some detail on sulphur using both batch and continuous techniques. This was done as it was considered that growth on sulphur would provide useful information which could be correlated with the mineral leaching results. The mineral pentlandite (NiFeS2) was chosen as the one with which to work because of its economic importance. This was prepared in a highly purified form from a concentrate of the Rhodesian Shangani deposit. Bacterial leaching tests in both batch and continuous operation were then carried out in order to define the effects of various physico-chemical parameters on the leaching of nickel from this mineral. As a preliminary to these tests, a detailed chemical kinetic study in the absence of bacteria of the leaching of nickel was carried out using similar physico-chemical conditions. The results of the bacterial and chemical leaching tests were then compared and used to postulate a mechanism and model for the process. It was found that the rate of leaching of nickel from pentlandite in acid ferric sulphate solutions was directly proportional to the concentration of ferric ions and speed of agitation of the stirrer and to the square root of the oxygen concentration. The form of the rate expression was interpreted in terms of a mixed diffusive and chemical rate controlling mechanism. Bacterial growth rates on flowers of sulphur were found to be controlled by the rate of dissolution of oxygen from the gas bubbles into the bulk solution. When this latter condition was made non-rate limiting, it was found that growth rates were still dependent on the rate of agitation, implying mass transport control by another mechanism. The batch bacterial leaching results showed a linear pattern of nickel leaching and bacterial growth, with a marked dependence on oxygen concentration and rate of agitation. A mechanism in accordance with the batch data was postulated, which proposed that the rate of bacterial leaching was proportional to the concentration of bacteria attached at the mineral surface and to the square of the oxygen concentration. The rates of bacterial leaching were computed by taking the difference between the overall measured leach rate and the chemical leach rate based on the chemical kinetic data. The leach rates in continuous bacterial leaching were higher than those predicted from the batch data. This effect was interpreted in terms of higher specific growth rates being achieved in continuous operation. An economic assessment was made of the process based on the optimum leach rates obtained in continuous leaching and found to show some promise. / Thesis (Ph.D.)-University of Natal, Durban, 1974.

Microbial leaching plays a significant role in the natural weathering of silicate containing ores such as diamond-bearing kimberlite. Harnessing microbial leaching processes to pre-treat mined kimberlite ores has been proposed as a means of improving diamond recovery efficiencies. The biomineralization of kimberlite is rarely studied. Therefore, this study investigated the feasibility of exploiting both chemolithotrophic and heterotrophic leaching processes to accelerate the weathering of kimberlite. Preliminary investigations using mixed chemolithotrophic leaching cultures were performed on four finely ground kimberlite samples (<100μm) sourced from different mines in South Africa and Canada. Mixed chemolithotrophic cultures were grown in shake flasks containing kimberlite and inorganic basal media supplemented either with iron (Fe2+, 15g/l) or elemental sulfur (10g/l) as energy sources. Weathering due to dissolution was monitored by Inductive Coupled Plasma (ICP) analyses of Si, Fe, K, Mg and Ca in the leach solutions at known pH. Structural alterations of kimberlite after specified treatment times were analyzed by X-ray Powder Diffraction (XRD). The results of the preliminary investigation showed that weathering can be accelerated in the presence of microbial leaching agents but the degree of susceptibility and mineralogical transformation varied between different kimberlite types with different mineralogical characteristics. In general, the results showed that the kimberlite sample from Victor Mine was most prone to weathering while the sample from Gahcho Kue was the most resistant. It was therefore deduced that kimberlite with swelling clays as their major mineral component weathered relatively more easily when compared to kimberlite that consisted of serpentine and phlogopite as their major minerals. Gypsum precipitates were also distinguished indicating that a partial alteration in the kimberlite mineralogical structure occurred. Both energy sources positively influenced the dissolution process, with sulfur producing superior results. This was attributed to the generation of sulfuric acid which promotes cation dissolution and mineral weathering. Success in the preliminary investigations led to further experimental testing performed to determine the effect of particle size and varying energy source concentrations on the biotransformation of kimberlite. It was observed that although weathering rates of the larger kimberlite particles (>2mm<5mm) were lower than that of the finer particles, slight changes in their mineralogical structures represented by the XRD analyses were seen. Optimisation studies of energy source concentration concluded that although the highest concentration of elemental sulfur (20% w/w) and ferrous iron (35% w/w) produced the most pronounced changes for each energy source tested, the leaching efficiency at these concentrations were not drastically greater than the leaching efficiency of the lower concentrations, as expected. Following the success of batch culture shake flasks weathering tests, the effect of continuous chemolithotrophic cultures on the biotransformation of larger kimberlite particles (>5mm<6.7mm) was investigated. A continuous plug-flow bioleach column was used to model the behaviour of chemolithotrophic consortia in a dump- or heap leaching system. Two sequential columns were setup, in which the first consisted of kimberlite mixed with sulfur and the second purely kimberlite. Inorganic growth medium was pumped to the first column at a fixed dilution rate of 0.25h-1 and the leachate from the first column dripped into the second. After an 8 week investigation period, the ICP and XRD data showed that weathering did occur. However, the pH results showed that the leaching process is governed by the amount of acid produced by the growth-rate independent chemolithotrophic consortia. Data from pH analyses also showed that the leaching bacteria reached ‘steady state’ conditions from day 45 onwards. The pH also remained higher in the second column than in the first column highlighting the alkaline nature of the kimberlite ores and its ability to act as a buffering agent and resist weathering. This important factor, as well as further optimisation studies in process operating conditions and efficiency, needs to be considered when establishing heap-leaching technology for these kimberlite ores. In the preliminary heterotrophic investigation, Aspergillus niger was used to produce organic metabolites to enhance kimberlite mineralization. The results demonstrated that the organic acid metabolites generated caused partial solubilization of the kimberlite minerals. However, it was deduced that for more significant changes to be observed higher amounts of organic acids need to be produced and maintained. The results obtained in this study also showed that the type of kimberlite presents a different susceptibility to the dissolution process and the presence of the fungal cells may improve the leaching efficiency. The results in this study provided an optimistic base for the use of microbial leaching processes in accelerating the weathering of kimberlite. These findings may also serve to supply data to formulate recommendations for further and future column microbial leach tests as well as validation and simulation purposes. / Thesis (M.Sc.) - University of KwaZulu-Natal, Pietermaritzburg, 2008.

Goonbarrow, a China Clay pit situated within the St. Austell granite China Clay region, is the subject of a varied geochemical and isotopic study to determine the mode of genesis of the kaolinite and associated tin/tungsten mineralisation. Detailed geological mapping in conjunction with a geochemical study of the micas indicated that Goonbarrow is situated at the junction of the petrographically distinct phases of the St. Austell granite. An unusual assymmetric curved-feldspar-crystal pegmatite is found at the junction. Elvans at Goonbarrow and three other locations within the St. Austell granite are shown to be intruded during hydrothermal activity and in some cases after major vein formation. Three main types of vein were recognised in Goonbarrow, the major ones being spatially associated with zones of kaolinised granite. A potassium/ argon age study showed that the granites, pegmatite and greisens (and by inference tin/tungsten mineralisation) were formed at about 280 ±10 m.y. Four elvans, including Goonbarrow, were dated at around 272 m.y. Three of these elvans crosscut major vein, swarms. Age determinations on fine grained muscovite produced predominantly during kaolinisation and several kaolinised potassium feldspars also gave Hercynian eges. Scanning electron microscopy studies on daughter minerals in fluid inclusions indicated the presence of Al, As, Ca, Cl, Cu, Fe, K, Kg, Mn, Na, S, Sn and Zn although many of these elements were not present in minerals in the pit. Temperatures, pressures and salinities of vein fluids were determined by conventional fluid inclusion studies, which also indicated that the veins vere boiling. Hydrogen and oxygen isotope studies on vein quartz and greisen muscovites coupled with a re-interpretation of previous work and the fluid inclusion study produced a new model for the genesis of Cornish China Clay. Kaolinite genesis from the vapour phase of hot boiling fluids intimately associated with greisen bordered quartz/tourmaline veins of Hercynian age is favoured.

Compacted shales cause problems because they tend to degrade with time due to weathering. Degradation results in the shale deteriorating from a hard rock-like material to a soft fine-grained soil mass with lower shear strength and high deformability. Consequently, common problems that occur in embankments constructed with compacted shales include settlement and instabilities. Therefore, accelerating weathering prior to compaction by wetting and breaking down the shales before placement can reduce the deterioration during the service life of the construction. Extensive laboratory testing was performed in order to characterize the mechanical behavior of compacted shales. Critical State theory is a clever framework that describes the mechanical behavior of soils with a simple system of equations that explains all the aspects of compression and shear of soils. NorSand is a model constructed in the framework of the Critical State theory that decouples the yield loci from the normally consolidated line. This characteristic made this model suitable for compacted shales. Also, empirical evidence showed that the plastic behavior of compacted shales is controlled by a Nova type flow rule that is a function of the mineralogical characteristics of the shales. This finding has implications in the shape of the yield loci and the hardening rule.

The initial study herein assessed mineral digestibility in situations when reducedamounts of inorganic and organic (proteinates) trace minerals (TM) were fed in finishingpigs, and their long-term effects on body mineral status. The second study was aslaughter-investigation that tested the impact of lean growth potential on phosphorusbody accretion from 30 to 110 kg.Organic TM exhibited neither improvement in digestibility nor in total retention;fecal excretion responded quantitatively to mineral intake independently of the source.Contents of copper in kidney and zinc in liver were higher for pigs fed the organic form.Phosphorus content was linearly related to live weight, empty body weight, andnitrogen content. Phosphorus accretion was very similar for both genetic backgrounds,with gilts retaining more mineral (Pandlt;0.05) than barrows. A N/P deposition ratio of 5.14was determined for pigs of both genders and genetic backgrounds to further predictphosphorus requirements based on protein accretion.Reduction of TM waste from growing-finishing pigs may be best addressed bylimiting their dietary inclusion rather than by using organic forms. Data from the secondstudy may be useful for an accurate estimation of phosphorus requirements, whichaccounts for variations in lean accretion rate.

Twenty-five animals that were randomly selected on the basis of sex and age from among the animals feeding exclusively on communal grazing in Mogosane village and were used to investigate the mineral (P, Ca and Mg) status, especially P, based on blood and faecal P and to estimate the quantity of P they consumed from the pasture they were grazing. The project was conducted in the same area each month for one year, and no supplement was given. Months were blocks and seasonal changes were factors and the animals were experimental units within a block. Faecal, blood and grass samples were used as indicators of P, Ca and Mg minerals within experimental units, and Analysis of Variance was done to determine whether the P status of native pastures had a significant effect on the total P, Ca and Mg utilization and movement in and out of the blood and throughout the faeces during different periods the year. Body mass, condition scores and rainfall were also recorded during this trial. When the mineral status was investigated in this trial, it was found that mineral content in blood and faeces was directly related to the minerals in the pasture since these indicators were curvilinear increasing from winter months to spring months peaking in summer months with highly (P< 0.05) significant values when grazing was best and declining as the grazing became worse during autumn and winter months. The values of the body condition of the animals increased and declined with the values of body mass. Blood P .. concentration was very inconsistent and varied greatly and did not follow the same increasing and decreasing pattern followed by faeces and the grass. This emphasizes the fact that the P content of blood is not always good indicator of the P status in the animal. The mean faecal P concentration during winter was lower with the value of 1.23 ± 0.13 mg/g, during spring was low with the value of 1.8 ± 0.06 mg/g, during summer was higher with the value of 3.22 ± 0.12 mg/g and -( during autumn was high with the value of 1.98 ± 1.04 mg/g. The mean concentration of P in the grass during winter was lower with the value of 0.92 ± 0.04 mg/g, during spring was low with the value of 1.16 ± 0.08 mg/g, during summer was higher with the value of 1.68 ± 0.06 mg/g and during autumn was high with the value of 1.22 ± 0.09 mg/g. The seasonal rainfall correlated with the faecal and grass P values vary much with the value of 0 mm in the winter season, with the value of 26.33 mm in the spring, the value of 90.4 mm during summer and the value of 44.83 mm during autumn. Condition scores and body masses had the values of 2.08 units/20 1.4 Kg during winter season, had the values of 3.07 units/272.29 Kg in spring season, had the values of 3.88 units/371 Kg during summer season and the values of2.75 units/286.65 during autumn season, respectively. / Thesis (M.Sc. (Agric.) North-West University, Mafikeng Campus, 2005

Salt marshes are one of the most difficult environments to remediate due to their sensitive and important ecosystems. Traditional cleanup methods can do more harm to the marsh than the oil itself. Bioremediation is the preferred cleanup approach for these delicate environments. Typically bioremediation has been carried out by the addition of nutrients but the results have been inconsistent. Previous laboratory studies conducted in oiled seawater demonstrated that clay minerals enhanced microbial growth and hence oil degradation. However, this had not been tested at field sites or on oiled marine sediments where oil is known to persist. The main objectives of this research were to test clay minerals as a bioremediation alternative for enhancing degradation of oiled salt marsh sediments and evaluate the geochemistry of sediment profiles for heavy metal enrichment. Laboratory experiments were carried out to evaluate the application of montmorillonite or kaolinite clay minerals on salt marsh sediments impacted by diesel oil. Oil biodegradation in control experiments was significantly more successful than in clay amended experiments. Clay minerals may have caused an increase in pH which inhibited enzyme-catalyzed processes required for metabolism. Field experiments were carried out in control and clay treatment plots in Louisiana salt marshes impacted by the Deepwater Horizon oil spill. In this research it was demonstrated for the first time that biodegradation of n-alkanes and PAHs was significantly enhanced by the addition of montmorillonite compared to controls. Vegetated treatment plots were slightly more effective than non-vegetative treatment areas. It is suggested that bivalent cations adsorbed to montmroillonite’s surface suppressed the diffuse double layer. This allowed the oil along the clay’s surface to be accessible to the bacteria where oil could be readily consumed. Clay minerals may serve as a new and unique bioremediation strategy for oiled salt marsh sediments. Geochemical sediment profiles from Louisiana salt marshes showed elevated concentrations of selected heavy metals (Zn > Cu > Pb > V > Cr > Fe > Ni). The Deepwater Horizon oil spill is a likely source of metal enrichment as many of these same metals are also constituents of the Deepwater Horizon oil.

Leaf and associated soil samples from 15 locations in Quebec showed that grey tobacco contained less N, P, K, Ca, B, nicotine, total alkaloids, organic acids, fatty acids, but more Fe and Al than non-grey (normal) tobacco. Soils producing grey tobacco had less N, Ca, organic matter, a lower cation exchange capacity but more Cl. / Fe('55) fed to tobacco plants grown in soil known to produce grey tobacco was translocated to vascular and associated tissue in leaves. The grey disorder symptoms were duplicated in hydroponically grown plants. / In a two-year field study, grey tobacco had 20% less dry weight and 30% less leaf area. Relative growth rate and net assimilation rate decreased less rapidly during growth in grey than in non-grey tobacco. N and K content in leaves was lower in grey tobacco but higher in Fe and Mn. / The grey effect was decreased or eliminated in tobacco plants grown in pots with manure and lime. The leaf contents of Fe, Mn and Mg were associated with grade index ((CENTS)/kg) and dollar value/ha of tobacco. Fertilizer and manure reduced leaf Ca. Fertilizer alone increased the leaf content of N, P and K while manure increased leaf dry weight. The ratio of K/Ca and K/(Ca + Mg) increased with increasing levels of manure relative to each level of lime while the percent grey tobacco decreased dramatically.

Potential protein supplements to grazing cattle were evaluated in two projects. In the first project, Karanja seedcake samples were prepared and ruminally incubated using the in situ method to measure nutrient disappearance in cattle consuming low-quality forage. Organic matter and CP were fractionated by degradability into A, B, and C fractions. Organic matter fraction A degradability ranged from 59.6 to 89% (P < 0.05) for all the karanja seedcake samples. Fraction A of CP ranged from 61.6 to 96.2% degradability for all the samples (P < 0.05). Karanja seedcake samples were observed to contain highly degradable nutrients and our results indicate karanja seedcake may possibly be utilized in grazing cattle protein supplements, consequently increasing economic sustainability of biofuel production. In the second experiment, four non-protein nitrogen supplements were ruminally infused in steers consuming low-quality forage. Supplements included a 40% CP mineral mix (40MM), 60% CP mineral mix (60MM), 25% CP liquid (25L), or 35% CP liquid (35L). Protein provision stimulated forage OM intake and total OM intake for both liquid supplements. Forage OM intake tended to be greater for the liquid supplements; 25L (P = 0.06) and 35L (P = 0.08), then control. Total OM intake significantly increased (P < 0.01) for both liquid supplements, when compared to the control treatment. Total digestible OM intake was greater (P < 0.01) for 25L (3.4 kg/d) and 35L (3.36 kg/d) than control (2.94 kg/d). Forage and total OM intake were not significantly affected by 40MM or 60MM treatments. Total tract digestions (OM and NDF) were not observed to be significantly different (P ≥ 0.11) between supplements and control. Ruminal ammonia was greater (P < 0.01) for all supplements then control and total ruminal VFA concentrations increased from 84.7 to 98.7 mM for control versus supplemented. Supplementation with liquids had a significant effect on intake. Our results indicate of the four supplements, liquid supplements improved the utilization of low-quality forage by cattle, thus improving nutrient stewardship.