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Showing 11 to 14 of 14 (0.03 seconds)Spelling suggestions: "subject:"chalcocite"" "subject:"calcocite""
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Thermodynamics and electrochemistry of the chalcocite-potassium ethyl xanthate systemBasilio, Cesar Indiongco January 1985 (has links)
Comprehensive thermodynamic calculations have been carried out on the chalcocite-KEX-water system based on complete mass balance equations which include both soluble and insoluble species. The calculations have yielded i) E<sub>h</sub>-pH stability diagrams for different KEX additions, ii) equilibrium concentrations and amounts of all the dissolved and insoluble species including those of CuX and CuX₂, iii) two- and three-dimensional plots showing the effect of E<sub>h</sub> and pH on the formation of selected species, and iv) minimum xanthate additions required to form CuX and CuX₂. These information can be used as a guide in predicting the optimum conditions for flotation and leaching of chalcocite.
The upper limiting potentials predicted from the thermodynamic calculations are in excellent agreement with those determined from the microflotation tests. The lower flotation edges, on the other hand, are found to be dependent on the sequence of reagent additions. When xanthate is added after the addition of a reducing or oxidizing agent to control the potential, they are in reasonable agreement with predicted values. When the collector is added prior to the potential control, however, the lower flotation edges are significantly higher than the predictions. The flotation experiments carried out at several different concentrations show that the minimum amount of the collector is required between 0 to 200 mv, as predicted by the thermodynamic calculations.
Voltammetry experiments carried out in the absence of a collector at pH 9.2 and 6.8 suggest that the anodic oxidation of chalcocite results in the formation of Cu₂O, Cu(OH)₂ and S<sup>O</sup>. At potentials below -400 mv, Cu₂S is reduced to Cu<sup>O</sup> and HS⁻. When xanthate is added, several adsorption peaks are observed. There are indications that the peaks appearing between -200 and -100 mv may involve the reaction between xanthate and Cu<sup>O</sup>. However, at potentials above -40 mv, xanthate may adsorb directly on chalcocite without involving Cu<sup>O</sup>. / M.S.
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Associated Sulfide Minerals in Thiosulfate Leaching of Gold: Problems and SolutionsXia, Chen 01 April 2010 (has links)
The effects of some associated minerals on thiosulfate gold leaching were studied through thermodynamic analysis and leaching experiments on composite ore samples containing various minerals and a reference silicate gold ore.
In the leaching test on the reference gold ore, about 93% of gold was extracted within 3.0 hours. The presence of various amount of pyrite, pyrrhotite, chalcopyrite, arsenopyrite, chalcocite, bornite, and some lead species, has significant detrimental effects.
Under reduced oxygen conditions, the thiosulfate consumptions could be significantly reduced. High gold extractions (i.e. >= 90%) were observed in the leaching tests with reduced dissolved oxygen (i.e., 0.7% oxygen in the supplied gas) in the absence or in the presence of sulfide minerals such as pyrite, pyrrhotite, arsenopyrite and chalcopyrite. High copper concentration and a pre-aeration step was also found to largely increase the gold extractions under such conditions.
Thiosulfate-copper-ethylenediamine system was found effective in the leaching of gold. The leaching kinetics was significantly slower than that of the conventional thiosulfate-copper-ammonia leaching. The consumption of thiosulfate, however, was largely reduced. This leaching system worked effectively on the reference gold ore within a wider pH range (e.g., 6-11), with or without ammonia. The presence of ammonia in a low concentration improved the leaching rate but also increase the consumption of thiosulfate. Comparable gold extractions were observed in the leaching of the composite ores containing various sulfide minerals, such as pyrite, pyrrhotite, chalcocite, galena and chalcopyrite.
The leaching of gold in the presence of iron sulfides was also improved by applying chemical additives, such as, carbonate, calcium, galena, phosphate, and additional hydroxide anion. It is proposed that these additives either passivated the harmful surface of sulfide minerals or masked some detrimental aqueous species.
Finally, some improved leaching methods concluded in this study were applied on a few industrial ore samples in order to demonstrate the effectiveness of these methods. It was found that by comprehensively applying these improved thiosulfate leaching strategies, satisfactory gold extractions and thiosulfate consumption results were archived on these ores. / Thesis (Ph.D, Mining Engineering) -- Queen's University, 2008-09-18 11:48:38.672
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The influence of adsorbed polymer on clay and copper mineral particles' interactionsHe, Mingzhao January 2009 (has links)
Attractive particle interactions which lead to the hetero-aggregation or 'sliming' of silicate clay gangue and valuable sulphide mineral particles are encountered in a number of hydrometallurgical and flotation processes. Sliming leads to poor recovery of the valuable minerals and high recovery of the clay gangue minerals in flotation concentrates. In the present work, the hetero-aggregation mechanism of hydrophilic mica clay mineral sericite (or muscovite) and hydrophobic chalcocite was investigated by probing the particle interactions and the prevailing interfacial chemistry under dispersion conditions where the individual chalcocite and sericite particles displayed negative zeta potentials. The mitigation/suppression of the hetero-aggregation was examined via the prudent control of dispersion conditions and pulp chemistry (i.e., pH modification and solution speciation control) and the use of two, anionic, polymeric dispersants with different molecular weight and functionality (carboxylate-substituted polyacrylamide, Cyquest 3223 and sulphonate-substituted polymaleic acid, P80 co-polymers) as dispersants. The adsorption behaviour of both polymers onto both minerals under industrially relevant suspension conditions have been quantified in terms of the polymer adsorption density and the adsorbed layer characteristics. These interfacial layer properties which impact on the mineral particles' zeta potentials and interactions, and also underpin the dispersion efficacy of polymers were characterized, using interfacial and solution analytical methods and TM-AFM imaging analysis.
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Geology of the Palo Verde Ranch Area, Owl Head Mining District, Pinal County, ArizonaApplebaum, Steven January 1975 (has links)
A quartz diorite intrusion of probable early Tertiary age that crops out over at least 6 square miles in the Palo Verde Ranch area in Pinal County, Arizona was mapped as a distinct intrusion. The quartz diorite intrudes an area comprising Pinal Schist, Oracle granite, andesitic flows, granoaplite, and dike rocks including both pegmatite and diabase. Two major physical features, the Owl Head Buttes and Chief Buttes volcanic areas, both remnants of an extensive early Tertiary series of flows of intermediate composition that covered the area, now remain as lava-capped buttes above the pediment. Weak but persistent fracture-controlled copper mineralization is found in the quartz diorite and the Pinal Schist at or near their mutual contacts in the form of chrysocolla, malachite, black copper oxides, chalcocite, chalcopyrite, and bornite, in decreasing order. Pyrite is rare. Alteration related to northeast and northwest-trending fractures increases in intensity from the common propylitic to argillic to the northeast toward the San Juan claims area. A barely discernible increase in copper sulfides mirrors the alteration zoning, although geochemical sampling showed background copper in the quartz diorite to be more uniform away from fractures.
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