Chalcopyrite (CuFeS2) is the most abundant of the copper sulfides and also one of the most refractory for leaching. Several processing routes have been proposed to overcome drawbacks associated with environmental problems related to copper extraction from this mineral. Atmospheric leaching in acidic ferric sulfate is regarded as being particularly attractive over other hydrometallurgical systems. However, the challenge has been to overcome the problem of slow extraction rates due to passivity encountered at high solution potentials in this system. This highlights the need to investigate better operating conditions to optimize copper extraction and prevent the problem of passivation, and to develop suitable modeling tools to assess and diagnose leaching performance. In this work, a dissolution rate expression for chalcopyrite leaching in acidic ferric sulfate media is proposed accounting for effects in the active and passive regions under potentials from 415 to 550 mV (Ag/AgCl). A model of chemical speciation in the bulk solution elucidates the idea of passivation caused by precipitation of ferric species and their consequent adsorption onto the chalcopyrite surface. Electrochemical studies on massive samples of chalcopyrite involving characterization and modeling of the anodic and cathodic half-cell reactions of chalcopyrite leaching together with mixed potential considerations lead to the development of the mathematical expression for dissolution rate. The mathematical model was calibrated with electrochemical parameters and results are in good agreement with real leaching data from batch tests for solution potential regions where passivity is not observed. On the other hand, the passive region was modeled by means of adjusting parameters related to adsorption energies of the passivating species. Results of the model for this region deviate from real data as potential becomes higher probably due to diffusion resistance through a layer composed of ferric complexes.

The abiotic leaching behavior of a chalcopyrite ore, from Asarco’s Ray-Mine, was conducted in shake flasks and miniature columns at elevated temperatures. The shake flask tests, with an ore particle size of 1.18mm-2.38mm, found the highest Cu extraction was obtained using 1M NaCl in a 9.8g/L sulphuric acid solution at 60°C, with 69% Cu extracted in 16 days. The next highest extraction, 59% Cu extracted in 16 days, was achieved by adding fine pyrite at a 4:1wt ratio with the chalcopyrite content, in a 9.8g/L sulphuric acid solution at 60°C. Flask tests using other lixiviants and additions found copper extractions in the range of 30-40% Cu after 16 days. In the mini-column tests, the rates of copper extraction were similar for all test conditions. The rate of Cu extraction, even with a small particle size of 1.18mm-2.38mm and an elevated temperature of 50°C, was slow for all test conditions with an average rate of ~0.15% Cu per day. The conceptual engineering of a hot, abiotic heap-leach for low-grade chalcopyrite ore, including hypothetical heat and mass balances was conducted. The leaching time for a commercial operation was estimated from published data on laboratory column leaching of chalcopyrite ores and extrapolated to a commercial heap-leach by analogy with known leaching times for chalcocite ores. In commercial abiotic heap-leaches of chalcopyrite ore, the partial oxidation reactions generate insignificant heat to maintain an elevated heap temperature therefore the heat required to maintain the elevated temperature must be provided externally. In commercial biotic chalcopyrite heap-leaches, the in-situ total oxidation reaction generates more heat than the abiotic reactions but is still insufficient to rapidly raise and maintain an elevated heap temperature. For a low-grade Chalcopyrite heap-leach the most practical method of providing this heat is by injecting steam into the base of the heap using current air injection pipes. An external oxidant is required and for an abiotic heap-leach external ferric generation will be required. / Thesis (Master, Mining Engineering) -- Queen's University, 2011-02-15 15:59:38.15

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This study was carried out to investigate the flotation and leaching behaviour of bornite and chalcopyrite when they are together as principal sulphide minerals. Bench scale flotation performance was examined both in the absence and in the presence of a collector, PEX. In the absence of a collector, chalcopyrite floated significantly better than bornite. In the presence of a collector there was a reversal in selectivity, with bornite recovery presiding over that of chalcopyrite. Chalcopyrite recovery was marginally improved from the collectorless flotation case while bornite experienced vastly improved recoveries in the presence of a collector to surpass the recovery of chalcopyrite. The gap between floatability of bornite and chalcopyrite became more prominent under oxygen-deficient conditions induced by nitrogen flotation, which significantly decreased flotation rate of both minerals, but the floatability of bornite was still much higher than that of chalcopyrite. It is suggested that galvanic interactions promote the interaction of bornite with a collector while retarding interactions of chalcopyrite with the collector. Collectorless flotation of chalcopyrite observed under oxidizing conditions using air is thought to be prevalent even in the presence of a collector obscuring the selectivity of the process. Leaching of the mixtures of bornite and chalcopyrite at mass ratios of 1:1, 1:3 and 3:1 are performed under various conditions to investigate the possible changes in leaching behaviour in relation to galvanic interactions. Leaching at 90°C in the presence of 0.1 M ferric ions in 0.1 M sulphuric acid provided the best results with 90% copper extraction from the mixtures in 6 hours. Observed copper extractions suggested increased copper extraction from chalcopyrite with this approach. The introduction of cupric and ferrous ions into solution, together with variation of solution potential made it difficult to assess in details on the effects of galvanic interactions due to these parameters being known to improve copper extraction from chalcopyrite. Galvanic interactions together with the presence of cupric ions were held mainly responsible for the increased copper extraction. / Thesis (Master, Mining Engineering) -- Queen's University, 2014-01-11 00:25:35.365

Thesis (PhD)--University of South Australia, 2008.

Thesis (PhD)--University of South Australia, 2008.

Thesis (PhDApSc(MineralsandMaterials)--University of South Australia, 2002.

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.

Thesis (PhDApSc(MineralsandMaterials))--University of South Australia, 2002.

Thesis (PhD)--University of South Australia, 1997