The effects of sodium bisulphate on the xanthate-induced flotation of chalcopyrite, copper-activated sphalerite and copper-activated pyrite have been studied. These investigations were conducted in two steps: 1) single mineral studies with varying experimental conditions; and 2) a mixed mineral chalcopyrite-pyrite-sphalerite study. A number of solution and surface spectroscopic techniques were used, which allowed simultaneous investigation of the mechanisms of interaction of sulphite ions with the mineral surfaces, and with the xanthate species in solution and its adsorbed state. Based on the results obtained, the following depressing mechanisms have been proposed. / It was found that sulphite ions had no depressing effect on chalcopyrite flotation under the experimental conditions studied. It was suggested that the main species responsible for chalcopyrite floatation were the hydrophobic sulphur-like species, such as an iron deficient chalcopyrite and polysulphide, and to some extent the adsorbed collector species. Sodium bisulphite did not decompose these hydrophobic phases on the chalcopyrite surface. It was also found that the chalcopyrite surface was not heavily oxidised either in the presence or absence of sulphite ions. / From the single mineral studies it was concluded that sodium bisulphite had a complex effect on the xanthate-induced floatation of copper-activated pyrite and sphalerite. These results demonstrated that under the experimental conditions tested, the following processes contribute to the selective depression of pyrite and sphalerite: (i) Xanthate decomposition in solution by sulphite ions, hence reducing the xanthate adsorption on the mineral surfaces. (ii) Collector removal from the mineral particles, rendering the mineral surfaces more hydrophilic. (iii) Sulphite oxidation to sulphate, accompanied by consumption of dissolved oxygen in solution, thus limiting collector adsorption (accompanied by a drop of pulp redox potential). (iv) Decomposition of hydrophobic sulphur-like species on the sphalerite and pyrite surfaces, rendering the mineral particles less floatable. (v) Surface oxidation of pyrite and sphalerite particles to produce hydroxide and oxy species, also rendering the mineral surfaces hydrophilic and preventing collector adsorption. As expected, these effects were more pronounced in the floatation experiments with air purging. / The mixed mineral study demonstrated that sodium bisulphate acted as an effective depressant for pyrite and sphalerite in the mineral mixture, while the chalcopyrite floatability was almost un-affected by sulphite ions. It was found that the mechanisms proposed for single mineral systems could satisfactorily explain the effect of sodium bisulphite on the floatation results obtained with the chalcopyrite-sphalerite-pyrite mineral mixture. Chalcopyrite floatation was not depressed by sulphite, due to the high stability of adsorbed xanthate species, and also due to the natural floatability of the chalcopyrite particles. At the same time, a reduction in the adsorbed collector concentration and a commensurate increase in surface hydrophilicity were responsible for the depression of pyrite and sphalerite from the mineral mixture in the presence of sulphite ions. / Thesis (PhDAppliedEngineering)--University of South Australia, 2003.
| Identifer | oai:union.ndltd.org:ADTP/267709 |
| Creators | Khmeleva, T. N. |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | copyright under review |
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