Browsing by Author "Harris, Peter"

Now showing 1 - 7 of 7
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    The effect of polysaccharides and inorganic dispersants on the surface characteristics of talc and the effect on the flotation performance of a Merensky ore
    (2001) Dalvie, Maqbool Ahmed; Bradshaw, Dee; Harris, Peter
    This dissertation describes an investigation into the combined effect of polysaccharides and an inorganic dispersant on the surface characteristics of talc and how this relates to the flotation performance of Merensky ore. The rationale in investigating the talc changes are due to its naturally flotable nature and the downstream problems that result from its reporting to the concentrate causing difficulties disproportionate to its average concentration of less than 2% in Merensky Ore.
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    An evaluation of sulfidisation in the flotation recovery of heavily oxidised sulfide minerals : with particular reference to oxidised Merensky ores
    (2007) Newell, Andrew James Haigh; Bradshaw, Dee; Harris, Peter
    Includes bibiographical references (p. 165-180).
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    Investigating depressant behaviour in the flotation of selected Merensky ores
    (2009) Wiese, Jennifer Gael; Bradshaw, Dee; Franzidis, Jean-Paul; Harris, Peter
    This study utilised laboratory batch flotation tests to characterise the flotation performance, with respect to sulfide and gangue minerals, of two Merensky ores with different mineralogy, in the presence of depressants; and contributes to the increased understanding of depressant behaviour in the flotation of Merensky ores. The ores were obtained from the southern section of the Merensky reef in the Bushveld Igneous Complex.
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    An investigation into chemical factors that affect the behaviour of Gangue minerals in the flotation of PGM ores
    (2004) Mailula, Tshepo Desmond; Bradshaw, Dee; Harris, Peter
    Flotation is one of the key steps in the beneficiation of Platinum Group Elements (PGE) from the Bushveld Complex in South Africa. This process aims to optimise the recovery of valuable PGE and sulphide minerals and the rejection of unwanted gangue minerals. The major reefs are exploited in South Africa i.e. Merensky reef and UG-2 reef. Gangue minerals, pyroxene and feldspar constitute more than 80% of the Merensky reef and chrornite up to 60% of the UG-2 reef. Although these minerals are considered to be hydrophilic and thus not floatable, these gangue minerals are known to report to the concentrate in large quantities during froth flotation. This results in lower grades and increased difficulties in downstream processing. Some Platinum Group Mineral (PGM) concentrators report that 2/3 of the gangue collected on the concentrate is by true flotation and only 1/3 by entrainment [Malysiak et ai, 2001]. This also suggests that mechanisms other than entrainment are responsible for this phenomenon. The behaviour of these minerals is selected for investigation in this thesis. During flotation of PGM ores, reagents such as copper sulphate and sodium isobutyl xanthate (SIBX) are added to enhance the recovery of valuable minerals. Copper sulphate, although added as an activator for valuable minerals, as the conditions used has been shown to also activate gangue minerals, thus its activation is non-selective [Shackleton, 2003 and Wesseldijk et ai, 1999]. Wesseldijk et ai, (1999), showed that copper sulphate could activate chromite and the subsequent addition of collector resulted in high recoveries of chromite in contrast to the low recoveries obtained in the absence of copper sulphate.
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    Investigation of the surface properties of gangue minerals in PGM bearing ores
    (2005) Martinovic, Jasmina; Bradshaw, Dee; Harris, Peter; Laskowski, Janusz
    The recovery of Platinum Group Minerals (PGM) and associated sulphides by froth flotation from the Bushveld Igneous Complex is complicated by the presence of naturally floatable gangue minerals such as talc. Although talc is present in small quantities it has a disproportionate effect on concentrate grade by enhancing froth stability and increasing the entrainment of other gangue minerals. However, there is an indication that some of the other gangue minerals, which are normally considered to be hydrophilic, such as chromite and pyroxene, report to the concentrate as floatable particles. Polysaccharide depressants, such as carboxymethyl cellulose (CMC) and modified guar gums are used to reduce the floatability of naturally floatable gangue and may also be able to reduce the floatability of activated gangue. This study examines the copper activation of a range of minerals found in the Bushveld Complex (namely pyroxene, feldspar, chromite and talc as well as the classical oxide, quartz) using zeta potential measurements, adsorption and microflotation tests. The effect on floatability is evaluated after activation and collector adsorption in the presence of a modified guar and a CMC depressant. Although quartz is not a major gangue component in PGM ores it was selected since it is a strongly negatively-charged mineral in the alkaline range and therefore likely to respond to copper activation. Steenberg and Harris, (1984) found that polymers such as guar and CMC did not appear to adsorb to a significant level on quartz.
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    The role of nitrogen on the flotation performance of a complex sulphide ore
    (2000) Bacus, Imraan; Harris, Peter
    This thesis focuses on the role of nitrogen on flotation performance of a sulphide PGM ore. Merensky ore obtained from Impala Platinum mine, Rustenburg, was used in laboratory batch flotation tests. Nitrogen addition was implemented during the conditioning and / or flotation stages of the test. In order to further evaluate the consistency of the role of nitrogen, tests were conducted using both stainless steel and mild steel as the milling media during the milling step prior to batch flotation. Specifically, the objectives of this thesis were as follows: To investigate the effect of nitrogen on the metallurgical flotation performance of the complex sulphide ore, as measured by mineral recoveries and grades of the major sulphide elements, copper, nickel and iron. These represent the major sulphides present in the ore; chalcopyrite (Cu), pentlandite (Ni) and pyrrhotite (Fe, as an approximate representative since Fe occurs in pyrrhotite, chalcopyrite, pentlandite as well as nonsulphide gangue). Secondly, to develop an understanding of the mechanisms of nitrogen addition on the relevant sub processes and interactions in froth flotation. The elucidation of these mechanisms was carried out with aid of complementary investigative studies which focused on the issues relating to the mechanistic role of nitrogen in flotation, as identified by the literature review. The first of these involved the evaluation of the role of nitrogen on the pulp chemical environment. The pulp chemical environment is defined here as the water - ore - reagent medium in which the valuable particle resides during the froth flotation process. Profiles of pH, temperature, dissolved oxygen (DO) and oxidation reduction potential (ORP, measured with a Pt - Ag/AgCI electrode) were recorded for each flotation test so as to monitor the changes in the pulp chemical environment, as a response to changes in milling media, reagent addition and gas addition. The second complimentary investigation involved the evaluation of the role of nitrogen on mineral surface oxidation. This involved the measurement of the level of metal hydroxide on the minerals' surface with a technique employing EDTA (ethylene diamine tetra acetic acid) for the purposes of extraction. This was to ascertain whether the addition of nitrogen during flotation tests resulted in reduced mineral surface oxidation either as a result of the direct effect of nitrogen or an indirect effect via galvanic interaction protection mechanisms. The final complimentary investigation involved an evaluation of the role of nitrogen on the collector-mineral and collector-mineral-activator interactions. This entailed the measurement of residual xanthate by UV spectroscopy. This was to ascertain whether any change in flotation response with nitrogen addition was attributable to a shift in the collector-activator-mineral interaction scheme.
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    The influence of polymeric charge and structure, molecular weight and ionic conditions on depressant ability to reduce the natural floatability of talc
    (2002) Shortridge, Paul Graham; Harris, Peter; Bradshaw, Dee
    Talc is a naturally floatable gangue material common in South African platinum bearing (PGM) ore bodies. Long chain polysaccharide depressants are effective in depressing talc flotation and improving the grade of the concentrates of those ores with talc as a gangue constituent. This thesis describes an investigation into the surface interactions of two types of long chain polysaccharide depressants (carboxymethylcellulose and guar gum) with pure talc and with Merensky PGM ore (which is known to contain talc as a gangue constituent). Specifically, the objectives of this thesis were as follows: 1. To characterize the differences in the depressants selected. 2. To examine the effects that polymeric structure and molecular weight of the depressant have on the hydrophobicity of talc. 3. To extrapolate the findings from highly controlled laboratory conditions to batch flotation tests with Merensky PGM ore. During the course of the experiments, it became clear that ionic conditions were an important factor in this system and they were therefore incorporated into the work done. Overall, the molecular weight of the depressants was not seen to be an important factor in their ability to depress talc. The molecular structure did appear to impact depressant efficiency, but only under conditions oflow ionic strength in the microflotation system. III Ionic conditions were found to be a pivotal factor in the performance of the CMC depressants in reducing the flotation of talc. It was also found that the ions adsorbed onto the talc surface in the absence of depressants - leading to a reduction in talc floatability. Divalent cations were more effective than monovalent cations in enhancing the effectiveness of the CMC depressants - suggesting stronger adsorption under these conditions. Guar depressants appeared to be unaffected by varying ionic conditions. The batch flotation tests, and the microflotation tests at the higher ionic strengths, showed that similar depressing ability was obtained for the CMCs and the guars. However, the batch floats indicated that increasing dosage led to improved depressant performance while the microflotation tests indicated that a maximum level of depression was achieved at fairly low dosages