Chalcocite oxidation

Young, C. A., Woods, R., Yoon, R. H., 1998. A voltammetric study of chalcocite oxidization to metalstable copper sulphides. In P. E. Richardson, R. Woods (ed.), Int. Symp. Electrochemistry in Mineral and Metal Processing II. Pennington Electrochem. Soc., 3-17... 

In direct attack, electrons removed by At. ferrooxidans attached to the surface of chalcocite are transferred by the electron transport system of the organism to O2 as terminal electron acceptor. The organism conserves energy in this electron transfer, which is a respiratory process. The following equation summarizes the initial steps in chalcocite oxidation ... 

Nielsen, A. M. Beck, J. V. (1972). Chalcocite oxidation and coupled carbon dioxide fixation by Thiobacillus ferrooxidans. Science, 175, 1124—6. 

Copper ore minerals maybe classified as primary, secondary, oxidized, and native copper. Primaryrninerals were concentrated in ore bodies by hydrothermal processes secondary minerals formed when copper sulfide deposits exposed at the surface were leached by weathering and groundwater, and the copper reprecipitated near the water table (see Metallurgy, extractive). The important copper minerals are Hsted in Table 1. Of the sulfide ores, bornite, chalcopyrite, and tetrahedrite—teimantite are primary minerals and coveUite, chalcocite, and digenite are more commonly secondary minerals. The oxide minerals, such as chrysocoUa, malachite, and azurite, were formed by oxidation of surface sulfides. Native copper is usually found in the oxidized zone. However, the principal native copper deposits in Michigan are considered primary (5). 

Central metal cation Monatomic metal cation to which all the ligands are bonded in a complex ion, 409 Cerium (IV) oxide, 147 Chadwick, James, 517 Chalcocite, 539... 

The adsorption of collectors on sulfide mineral occurs by two separate mechanisms chemical and electrochemical. The former results in the presence of chemisorbed metal xanthate (or other thiol collector ion) onto the mineral surface. The latter yields an oxidation product (dixanthogen if collector added is xanthate) that is the hydrophobic species adsorbed onto the mineral surface. The chemisorption mechanism is reported to occur with galena, chalcocite and sphalerite minerals, whereas electrochemical oxidation is reportedly the primary mechanism for pyrite, arsenopyrite, and pyrrhotite minerals. The mineral, chalcopyrite, is an example where both the mechanisms are known to be operative. Besides these mechanisms, the adsorption of collectors can be explained from the point of interfacial energies involved between air, mineral, and solution. 

Chalcocite and covellite are also oxidized by ferric sulfate, with the resulting ferrous sulfate reoxidized back to the ferric form. This mechanism is termed indirect bacterial oxidation. Ferric oxidation of chalcocite can also be seen to proceed through two stages, with very quick conversion to covellite in the first stage, and the completion of the oxidation in the second stage ... 

The sulfuric acid needed to solubilize copper from chalcocite is balanced by the acid recovered from the copper electrowinning step this acid is recycled to the heaps. The overall acid requirements for the process are, therefore, dependent on the acid consumption by the gangue minerals in the ore and the acid production by pyrite oxidation. If the pyrite associated with the ore is significant and the acid consumption by the ore is low, excess sulfuric acid can be neutralized by lime. 

Mixed copper sulphide oxide ores. These contain varieties of both sulphide and oxide minerals, and are the most complex copper-bearing ores from a beneficiation point of view. The major copper minerals present in this ore type include bomite, chalcocite, covellite, malachite, cuprite and chrysocolla. In some cases, significant amounts of cobalt minerals are also present in this ore. 

Gaudin and Schuhmann (1936) and Harris and Finkelstein (1977) have shown that the most likely adsorbed hydrophobic entity is cuprous xanthate which could be formed by a combination of the oxidation of chalcocite and the reaction of the... 

Heyes, G. W. and Trahar, W. J., 1979. Oxidation-reduction effects in the flotation of chalcocite. Inter. J. Miner. Process, 6 229 - 252... 

Copper is the 26th most abundant element on Earth, but it is rare to find pure metallic deposits. It is found in many different types of mineral ores, many of which are close to the surface and easy to extract. It is found in two types of ores (1) sulfide ores, such as covellite, chalcopyrite, bornite, chalcocite, and enargite and (2) oxidized ores, such as tenorite, malachite, azurite, cuprite, chrysocolla, and brochanite. 

Cu isotope compositions of chalcocite from enrichment blankets or Fe-oxides... 

Seo, J.H., Lee, S.K., Lee, I. 2007. Quantum chemical calculations of equilibrium copper (I) isotope fractionations in ore-forming fluids. Chemicai Geoiogy, 243, 225-237. Wall, A., Heaney, P., Mathur, R. 2007. Insights into copper isotope fractionation during the oxidative phase transition of chalcocite, using time-resolved synchrontron X-ray diffraction. Geochimica Cosmochimica Acta, 77, A1081. 

The highest copper concentrations are contained in white dolomites (4,137 ppm on average) where primary chalcocite and copper and manganese oxides occur. No concentrations of interest in Au, Ag, Pb and Zn were detected in the dolomites. The dolomitic unit shows the highest concentrations in Mn (0.56% to 2.6%). 

Copper is distributed widely in nature as sulfides, oxides, arsenides, arsenosulfides, and carbonates. It occurs in the minerals cuprite, chalcopyrite, azurite, chalcocite, malachite and bornite. Most copper minerals are sulfides or oxides. Native copper contains the metal in uncombined form. The principal copper minerals with their chemical compositions and percentage of copper are listed below ... 

Acidithiobacillus ferrooxidans is able to degrade chalcocite (CU2S) by oxidizing the Cu(I) in the mineral to Cu and the sulphide-S to 804 . Because the end-products of this oxidation are soluble, the oxidation results in the mobilization of the copper and sulphur in the chalcocite. Evidence exists for two distinct mechanisms by which At. ferrooxidans can perform the oxidation of chalcocite. One mechanism involves a direct attack of the crystal lattice of chalcocite by cells attached to the surface of chalcocite. The other mechanism involves an indirect attack of the crystal lattice of chalcocite by the chemical oxidant Fe generated from Fe in the bulk phase by planktonic cells (unattached) oi At. ferrooxidans. 

Other acidophilic Fe(II)-oxidizing bacteria may also promote oxidation of chalcocite, but whether by a direct or indirect mechanism remains to be elucidated. 

Likewise, the initial oxidation step of other metals sulfides (chalcocite, covellite, galena and sphalerite) appeared to produce the aqueous divalent metal ion and elemental sulfur. 

More and more minerals are being found amenable to bacteriological leaching. The copper sulfide minerals, such as chalcopyrite (B31-B33, D22, D24), chalcocite (B35), and tetrahedrite (B32, D21) are among the best studied. The iron sulfide (pyrite) (B31, B33, C22, L4) and sulfur (B33, B34, C22, L4) oxidation processes are the best understood. Investigations on the leaching of nickel sulfides (D21, D24, T17), lead sulfide (E4), molybdenum sulfide (molybdenite) (B17, B31, D24), cobalt sulfide (D9), zinc sulfide (D24), and uranium oxide (D24, F2, H13, H14, Ml) have been reported in the literature. 

The possibility of using brine to slurry the ore in the presence of an oxidizer such as chlorine in order to extract metals from the more common sulfide minerals has been studied by Strickland and co-workers (Jl, S12, S13). The reactions of acid chlorine solutions with galena (PbS), pyrite (FeSj), sphalerite (ZnS), chalcocite (CujS), covellite (CuS), chalcopyrite (CuFeSs), bornite (CusFeSi), pyrrhotite (FeS), and arsenopyrite (FeAsS) were examined with respect to their reaction rates and mechanisms. 

Three primary reactions were observed between aqueous chlorine and the base-metal sulfides. Elemental sulfur was produced during the reaction with chalcocite, bornite, and covellite. A rapid oxidation of the pyrrhotite, pyrite, and arsenopyrite to the sulfate form was observed. The formation of sulfur monochloride was indicated with sphalerite, galena (under most conditions), and chalcopyrite. The ratio of sulfur to sulfate was close to what could be expected if the sulfur monochloride hydrolyzed to form sulfur. Thermodynamic considerations indicated sulfate formation as the primary product. 

Ores of copper native copper, cuprite, chalcocite, chalcopyrite, malachite, azurite. Metallurgy of ores containing native copper, oxide and carbonate ores, sulfide ores. Gangue, flux, flotation, roasting of ores, matte, blister copper. Cupric compounds copper sulfate (blue vitriol, bluestone), Bordeaux mixture, cupric chloride, cupric bromide, cupric hydroxide. Test for cupric ion with Fehling s solution. Cuprous compounds cuprous chloride, cuprous bromide, cuprous iodide, cuprous oxide. Covalent-bond structure of cuprous compounds. 

World mine production of copper is currently in the range of 13-14 Mt, about a third of which is from Chile. Other large producers are the United States, followed closely by Indonesia and Australia. The most important ore mineral is chalcopyrite [CuFeS2], and also significant are bornite [CusFeSJ and chalcocite [CU2S]. The first two are primary minerals, whereas chalcocite forms principally by their weathering and subsequent reprecipitation of the solubilized copper as enriched blankets of chalcocite ore beneath the oxidation zone. 

Today, essentially all copper is obtained from minerals such as azurite, or basic copper carbonate (Cu2(0H)2C03) chalcocite, or copper glance or copper sulfide (CU2S) chalcopyrite, or copper pyrites or copper iron sulfide (CuFeS2) cuprite, or copper oxide (CU2O) and malachite, or basic copper carbonate (Cu2(0H)2C03). 

The oxidation of sulphides may proceed with extreme rapidity and spontaneous sulphide fires in mines have not been an uncommon occurrence. Bateman (1950) notes that a sulphide vein in a blind and warm stope at the Leonard Mine (Butte, Montana) was oxidised to a depth of 1 m within two years. At the Ely Mine, Nevada, chalcocite ore in a bench in an open pit was oxidised so quickly that, at a depth of 10-15 m, about 15% copper within the ore was removed in solution. 

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