| Summary: | Bibliography: leaves 90-95. === 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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