Browsing by Author "Laskowski, Janusz"

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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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    Surface properties of New York talc as a function of pH, polymer adsorption and electrolyte concentration
    (2007) Burdukova, Elizaveta; Laskowski, Janusz
    Talc is a common siliceous gangue mineral found in ore bodies beneficiated by flotation. Talc is a layered anisotropic mineral, with a mineral structure comprising of basal planes and edges. The basal planes of talc are considered completely neutral, while the edges of talc are thought to undergo a change from positive to negative at a highly acidic pH. Talc is highly floatable, requiring polymeric depressants to be added to flotation pulps in order to prevent it from entering the concentrate and reducing its grade. Various polymers such as non-ionic guar gums and anionic Carboxymethyl cellulose (CMC) depressants are employed for this purpose. However, the industrial use of these reagents is still inefficient. One of the factors affecting the performance of these polymers as depressants is the water quality of the flotation medium, specifically the concentration and type of electrolyte present. The objective of this thesis was to investigate of the surface properties and structure talc, and its effect on the adsorption mechanisms of different types of polymeric depressants in the presence of varying types of metal cations in solution in the context of mineral flotation. The surface potential of talc was investigated using rheological, titration and electron microprobe analyses. It was found that the rheological behaviour of talc is inconsistent with the premise that the talc basal planes carry no electrical charge. Furthermore, potentiometric titration measurements showed that the point of zero charge of talc does not correspond to the electrophoretic isoelectric point of talc. The discrepancy was attributed to the unsuitability of zeta potential measurements for evaluation of anisotropic plate-like minerals.