Thesis (B.S.)--University of Missouri, School of Mines and Metallurgy, 1909. / The entire thesis text is included in file. Typescript. Illustrated by authors. Ralph W. Watson determined to Ralph Wilheim Watson from "Thirty-Eighth Annual Catalogue. School of Mines and Metallurgy, University of Missouri". Ralph W. Watson is not listed in "University of Missouri, School of Mines and Metallurgy, Thirty-Eighth Annual Commencement" program. Title from title screen of thesis/dissertation PDF file (viewed February 23, 2009)

Thesis (B.S.)--University of Missouri, School of Mines and Metallurgy, 1910. / The entire thesis text is included in file. Typescript. F. E. Riede determined to be Frederick Edward Riede and E. F. Boland determined to be Earl Frederick Boland from "Forty-First Annual Catalogue. School of Mines and Metallurgy, University of Missouri". F. E. Riede received a Bachelor of Science degree in Metallurgical Engineering and E. F. Boland received a Bachelor of Science degree in Mining Engineering. Both degrees determined from "1874-1999 MSM-UMR Alumni Directory". Title from title screen of thesis/dissertation PDF file (viewed February 27, 2009)

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A gradual depletion of high-grade ores, coupled with the growing demand for mineral commodities across the world has culminated in the increased exploitation of lean-grade ores with complex mineralogy. The mineral processing industry commonly uses an extensive range of inorganic, naturally derived or synthetic organic reagents in the separation of valuable minerals from the ore. Froth flotation is a commonly used separation technique to float or depress different sulfide minerals from the ore, based on their surface properties. In recent times, biological processes have been attracting attention in mineral processing and metal recovery operations due to a number of factors, especially lower operating costs, lesser energy consumption and their environment friendly nature. The use of microorganisms and their direct derivatives in mineral processing, hydrometallurgy and in the bioremediation of mineral industry discharges has led to the emerging area of “Mineral Bioprocessing”. In this study, a family of four microorganisms belonging to the Bacillus species, viz., Paenibacillus polymyxa, Bacillus circulans, Bacillus megaterium and Bacillus subtilis was used to ascertain the selective floatability of sphalerite from a sphalerite-galena mineral mixture. These bacteria are Gram positive, mesophilic, neutrophilic, aerobic and spore forming. The major objectives of the investigation include: a) Identification and characterization of bioreagents derived from Bacillus species for the flotation of sphalerite from a sphalerite-galena mixture b) Optimization of the flotation process for the enhanced recovery of sphalerite using specific bioreagent combinations c) Modes and mechanisms of bacterial adaptation to minerals and their consequent effects on the flotation of sphalerite and galena d) Elucidation of the mechanisms of microbe-mineral interactions and the role of extracellular secretions in sphalerite flotation column and their N-terminal residues were identified using Edmann N-terminal sequencing. Additionally, sequences of several internal peptides from both the proteins were determined using Tandem Mass Spectrometric techniques. A database search revealed that the sequences of these peptides are unique and have not been reported earlier. It was established that the bacterial cells give high flotation recovery of sphalerite under buffered conditions and that it took place only in the presence of anionic buffers. Additionally, the viability of the bacterial cells was not required for the flotation of minerals. A major finding of this study was that other than extracellular DNA (eDNA), none of the other bacterial surface components like teichoic acids, surface proteins, polysaccharides played a positive role in the flotation process. Nucleic acids, more particularly single stranded DNA (ssDNA), facilitated sphalerite flotation relative to double stranded DNA (dsDNA). A probable mechanism of ssDNA -mediated selective flotation of sphalerite has been presented. A negative role for non-DNA surface components was also observed. This led to the realization of the need for an optimum ratio of DNA to non-DNA components in the selective flotation of sphalerite from a sphalerite-galena mixture. It was found that the surface physiochemical properties of the mineral adapted bacteria differed significantly from that of the unadapted bacteria. Adaptation enhanced the flotation recoveries of the corresponding mineral vis-à-vis the unadapted bacteria. Sphalerite adapted bacteria secreted more extracellular proteins while the galena adapted bacteria secreted more polysaccharides compared to the unadapted bacteria. Sphalerite adapted bacteria selectively floats more sphalerite from the mineral mixture than the galena adapted as well as the unadapted bacteria. It was evident from the electrokinetic studies that the surface charge of the chosen sulfide mineral adapted bacteria was less negative relative to the unadapted bacteria. This phenomenon was observed with all the four bacterial species used in this study. A noteworthy finding was that the bacteria especially B.circulans induce a change in morphology from rod to sphere as a strategy during adaptation to a toxic mineral such as galena. This phenomenon has been shown to involve changes in crucial cell wall components as well as changes in the levels of expression of bacterial cytoskeleton elements involved in the maintenance of the rod shape. This aspect of the study involved the partial sequencing of the B.circulans homolog of the key cytoskeleton gene, mreB (B gene in murien cluster e), using the Polymerase Chain Reaction (PCR) followed by DNA sequencing. A Genbank search indicated that this is the first report of the sequence of B.circulans mreB gene. This was followed by measuring the hypothesized downward changes in the levels of expression of the mreB gene by Reverse Transcriptase Polymerase Chain Reaction (RT-PCR). The possible mechanisms of the adaptive morphological changes and of the interaction of the chosen sulfide minerals with the family of microorganisms studied have been discussed with respect to their bioflotation efficiency.

The present research is focused on investigating particle interactions between valuable and gangue materials, and the effect of these interactions on selectivity in flotation. This is a very important issue to operations at several mines across the world (e.g., at Century Mine operated by Zinifex Ltd in Australia). Particle interactions between valuable and gangue minerals with subsequent aggregation have significant impact on flotation performance. Valuable minerals may be depressed if heavily covered with hydrophilic gangue minerals and/or gangue minerals may misreport to the concentrate.

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Four sphalerites (synthetic, high grade natural, moderately impure flotation concentrate and highly impure flotation concentrate) were leached in acid sulphate media without and with ferric ions present under the following conditions :- Case (i) [Fe3+]o : [H2S04]o = 0,0 Case ( ii) [Fe3+]o : [H2S04]o = 1,8 Case (iii) [Fe3+]o : [H2S04]o = 0,1 Extensive data for leaching under these conditions are tabulated. Kinetic mechanisms based on Langmuir-Hinschelwood adsorption theories were proposed, and leaching models were developed for different assumed rate limiting steps. The initial rate and overall forms of the models were tested using experimental data.Leaching under case (i) conditions Non-oxidative dissolution took place with Zn2+ and H2S the predominant reaction products. The H2S partial pressure was monitored continuously and solution samples were taken for analysis at discrete time intervals. Vibratory (i.e. attrition) milling eliminated very large differences observed in the leaching characteristics of course size fractions of the natural sphalerites. The initial rate form of a model based on a dual site reaction mechanism and on either H+ adsorption or reaction product desorption rate control was found to fit the data for the synthetic and vibratory milled forms of sphalerite. The most impure vibratory milled sphalerite adsorbed Zn2+ and H2S very strongly, and this resulted inproduct desorption rate control. Vibratory milled forms of the high grade natural sphalerite and the moderately impure flotation concentrate, exhibited virtually identical initial rate dissolution kinetics, despite large differences in their chemical compositions. Leaching under case (ii) conditions Oxidative dissolution took place with Zn2+ and elemental sulphur the predominant reaction products. Scanning electron microscope photographs of leached and unleached particles showed the sulphur present on the particle surface. These photographs, and optical microscope photographs of etched polished sections, showed that dissolution took place in a complex way. A model based on ferric ion adsorption as the rate limiting step was proposed and confirmed experimentally. The model demonstrated a proportional dependency of the rate on the area and ferricion concentration, and an inverse dependency on the hydrogen ion concentration. For a -90,0 + 63,0 um size fraction, the three natural sphalerites exhibited virtually identical dissolution rates per unit area. The effect of ball milling or vibratory milling the sphalerites fine, was to increase the rate per unit area for the most impure natural sphalerite but decrease the rate per unit area for the high grade natural sphalerite.It was shown that for course size fractions of sphalerite, the most impure sphalerite which leached slowest under case (i) conditions (i.e. adsorbed H+ poorly) leached fastest under case (ii) conditions (i.e. adsorbed Fe3+ strongly). The reverse was true for the high grade natural sphalerite. Except in the case of synthetic sphalerite leaching under case (i) conditions, no correlation was shown to exist between the way the B.E.T. measured area changed, and the way the calculated active area changed during leaching. Leaching under case (iii) conditions Oxidative and non-oxidative dissolution, as well as H2S oxidation by Fe3+ occured simultaneously. The extents to which oxidative or non-oxidative dissolution occured could be explained in terms of the hydrogen ion and ferric ion adsorption characteristics of the sphalerites.The ferric ion oxidation of H2S was studied in the absence and presence of solids, and the presence of sphalerite or activated charcoal catalysed this reaction. No advantage was gained by leaching in the presence of activated charcoal with or without Fe3+ present, unless conditions were such that H2S was formed as a product of reaction. / Thesis (Ph.D.)-University of Natal, Durban, 1977.