The role of nitrogen on the flotation performance of a complex sulphide ore
Master Thesis
2000
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University of Cape Town
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Abstract
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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Bibliography: leaves 94-99.
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Bacus, I. 2000. The role of nitrogen on the flotation performance of a complex sulphide ore. University of Cape Town.