Copper sulphide minerals

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 

However, the calculated potential for CuEX formation corresponding to a xanthate concentration of 4.7 x 10 mol/L are, respectively, 0.021V for Eq. (4-6), 0.082V for Eq. (4-7b) and -0.391V for Eq. (4-8b) (for pH = 11 and a sulphate ion concentration of 10 mol/L), which do not agree with the observed lower limiting flotation potential of Heyes and Trahar (1979) in Fig. 4.2 (curve 2). The calculated potential for reactions (4-1) also do not correspond with the results of curve 1 and 3 in Fig. 4.2. 

The calculated decomposition potential are 0.783 V atpH= 5,+0.516 VatpH=8, and +0.251 V at pH= 11 for [ HCuOj ] = 10 mol/L for reaction (4-10a). Neither fits the data in Fig. 4.2. The calculated decomposition potential however are 0.59 V at pH = 5, 0.411 V at pH= 8 and 0.23 V at pH= 11 for reaction (4-lOb), which are in excellent agreement with Basilio s results in Fig. 4.2, although the results of Heyes and Trahar in Fig. 4.2 show that there is no upper limiting potential for chalcocite at pH = 8. Thus the fall in recovery will commence at the potential predicted by the reaction of the type (4-10b). The reaction (4-10) also gives an evidence that dixanthogen dose not confer floatability on chalcocite in the region of potential in Fig. 4.2. 

The influence of pulp potential on the floatability of chalcopyrite is shown in Fig. 4.4 for an initial concentration of 2x 10 mol/L ethyl XMthate and butyl xanthate. The lower flotation potential is -O.IV for KBX and OV for KEX. The hydrophobic entity is usually assumed to be dixanthogen (Allison et al., 1972 Woods, 1991 Wang et al, 1992) by the reaction (1-3). The calculated potential in terms of reaction (1-3), are, however, 0.217 V and 0.177 V, respectively, for ethyl and butyl xanthate oxidation to dixanthogen for a concentration of 2 x lO mol/L, which corresponds to the region of maximum recovery but not to the lower limiting potential for flotation, indicating that some other surface hydrophobicity to the mineral. Richardson and Walker (1985) considered that ethyl xanthate flotation of chalcopyrite may be induced by the reaction  

For [EX ] = 2x 10 mol/L, CuX would be produced at 0.18V. Again, it does not correspond with the observed lower limiting flotation potential. 

---

Abstract In the beginning, the mixed potential model, which is generally used to explain the adsorption of collectors on the sulphide minerals, is illustrated. And the collector flotation of several kinds of minerals such as copper sulphide minerals, lead sulphide minerals, zinc sulphide minerals and iron sulphide minerals is discussed in the aspect of pulp potential and the nature of hydrophobic entity is concluded from the dependence of flotation on pulp potential. In the following section, the electrochemical phase diagrams for butyl xanthate/water system and chalcocite/oxygen/xanthate system are all demonstrated from which some useful information about the hydrophobic species are obtained. And some instrumental methods including UV analysis, FTIR analysis and XPS analysis can also be used to investigated sulphide mineral-thio-collector sytem. And some examples about that are listed in the last part of this chapter. 

The ability of SO2/O2 mixtures to oxidise iron and various other ionic species is well known (5), and a similar process for the reoxidation of ferrous ions during the leaching of copper sulphide minerals has been recently published (6). 

The production of copper from sulphide minerals is accomplished with a preliminary partial roast of die sulphides before reaction widr air in the liquid state, known as mattes, to form copper metal (conversion). The principal sources of copper are minerals such as chalcopyrite, CuFeSa and bornite CuaFeSa, and hence the conversion process must accomplish the preferential oxidation of non, in the form of FeO, before the copper metal appears. As mentioned before, tire FeO-SiOa liquid system is practically Raoultian, and so it is relatively easy to calculate the amount of iron oxidation which can be canned out to form this liquid slag as a function of the FeO/SiOa ratio before copper oxidation occurs. The liquid slag has a maximum mole fraction of FeO at the matte blowing temperatures of about 0.3, at solid silica saturation. 

The colour is the most obvious and conspicuous external property of a large number of minerals. Minerals are distinguished by an extraordinary variety of colours and shades of varying richness and intensity. Some mineral species are characterised by a constant colour, which enables one to detect them almost unerroneously. Just as an example, mention may be made of a sulphidic mineral of copper, bomite (Cu5FeS4). The best identifying feature of this mineral is its purplish-blue tarnish over a bronze colour ( peacock ore). 

In most cases, oxide copper ores contain more than one copper oxide mineral, and also contain mixtures of sulphide and oxide copper minerals. From a processing point of view, the oxide copper ores can be divided into the following five groups ... 

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. 

Arsenic occurs primarily in sulphide minerals associated with copper ores, and to a lesser extent with zinc, lead and gold ores. Arsenic is produced as a by-product of the smelting of these metals. Primary arsenic production has now ceased in the USA and Europe, and most arsenic is now imported from China and Mexico. The volatility of arsenic represents a significant concern, and there is at present no known natural mechanism by which arsenic is immobilized in the environment. Anthropogenic activities account for an input of some 19000 tonnes into the atmosphere, compared with 12000 tonnes from natural processes, such as volcanism and forest fires (Ayres and Ayres, 1996). 

In the 2nd period ranging from the 1930s to the 1950s, basic research on flotation was conducted widely in order to understand the principles of the flotation process. Taggart and co-workers (1930, 1945) proposed a chemical reaction hypothesis, based on which the flotation of sulphide minerals was explained by the solubility product of the metal-collector salts involved. It was plausible at that time that the floatability of copper, lead, and zinc sulphide minerals using xanthate as a collector decreased in the order of increase of the solubility product of their metal xanthate (Karkovsky, 1957). Sutherland and Wark (1955) paid attention to the fact that this model was not always consistent with the established values of the solubility products of the species involved. They believed that the interaction of thio-collectors with sulphides should be considered as adsorption and proposed a mechanism of competitive adsorption between xanthate and hydroxide ions, which explained the Barsky empirical relationship between the upper pH limit of flotation and collector concentration. Gaudin (1957) concurred with Wark s explanation of this phenomenon. Du Rietz... 

Abstract Two systems are discussed in this chapter, which are copper activating zinc-iron system with and without depressants. Firstly, the system in the absence of depressants is discussed. And it is obtained that at a specific pH the activation for each mineral occurs in a certain range. Through the electrochemical methods and surface analysis the entity contributing to the activation can be identified which are usually copper sulphides and vary for different minerals. Secondly, the system with depressants is researched. And also the effects of pulp potential on the activation are discussed. The same conclusion can be obtained as the one from the former system. Furthermore, zeta potential are involved in the discussion of activation and die mechanism can be explained firom the changes of zeta potential. Similarly, the activation mechanism of this system is also studied through solution chemistry, bonding of activator with mineral surfaces and surface analysis. 

Electrochemical Mechanism of Copper Activating Zinc-Iron Sulphide Minerals... 

Activation of Copper Ion on Flotation of Zinc-Iron Sulphide Minerals in the Presence of Depressants... 

The influence of copper ion on the flotation of zinc-iron sulphide minerals in the presence of depressant with butyl xanthate l.Ox 10 mol/L as a collector is presented in Fig. 6.11 to Fig. 6.14. It can be seen from Fig. 6.11 and Fig. 6.12 that in the presence of 120 mg/L 2-hydroxyl ethyl dithio carbonic sodium (GXl) and 2,3 dihydroxyl propyl dithio carbonic sodium (GX2), marmatite is activated by copper ion and exhibits very good flotation with a recovery above 90% in the pH range of 4-8. The flotation of arsenopyrite and pyrrhotite is poor with a... 

Miner. Process Extra. Metall. Rev., 2 203 - 234 Hayes, R. A. and Ralston, J., 1988. The collectorless flotation and separation of sulphide minerals by control. Inter. J. Miner. Process, 23 55 - 84 Hepel, T. and Pomianowski, A., 1977. Diagrams of electrochemical equilibria of the system copper-potassium ethyl xanthate-water at 25°C. Int. J. Miner. Process, 4 345 - 361 Heyes, G. W. and Trahar, W. J., 1977. The natural floatability of chalcopyrite. Int. J. Miner. Process, 4 317-344... 

Rand, D. A., 1975. Oxygen reduction on sulphide minerals, part III comparisson of activity of various copper, iron, lead, nickle mineral electrodes. Electrochemistry and Interfacial Electrochemistry, 60 265 - 275... 

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... 

The CLEAR process is designed to completely leach the copper values from a copper concentrate consisting of any combination of copper sulphide or copper iron sulphide mineralization. The most abundant copper mineral is chalcopyrite whose composition is... 

---