Zinc Sulphide Minerals

Only limited studies on the electrochemical behavior of sphalerite have been reported, perhaps due to its high electrical resistivity. The Relation between recovery of sphalerite and pulp potential is presented in Fig. 4.17 with an initial butyl xanthate concentration of 10 mol/L. It can be seen from Fig. 4.17 that flotation begins at 0 V, the upper limit potential is 0.31 V. 

The potential is 200 mV based on reaction (4-31) and 10 mV on reaction (4-32) at natural pH. It can be inferred that the initial reaction of sphalerite corresponds to reaction (4-32). 

For the collector flotation of sphalerite, the upper limit potential of flotation may be corresponding to the following decomposition reactions  

Assuming the concentration of all dissolved species to be lO mol/L, the reaction potential are 0.37 V and 0.32 V respectively, corresponding to reactions (4-33) and (4-34) and the oxidation peak potential in Fig. 4.18. Therefore the upper limit potential of flotation of sphalerite may depend on reaction (4-33) or (4-34), i.e. the decomposition of zinc xanthate and the formation of zinc hydroxide or oxy-zinc species. 

The influence of pulp potential on the flotation of marmatite at different pH is given in Fig. 4.20 using ethyl xanthate as a collector. In acidic pH media, marmatite exhibits a wide floatable potential range and the upper potential limit of flotation 

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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 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. 

Khalid, A.M. and Ralph, B.J., 1977. The Leaching behaviour of various zinc sulphide minerals with three Thiobacillus species. Conference Bacterial Leaching. GBF Monograph Series, No. 4 pp. 165—173. 

Dutrizac has reviewed (4) the dissolution of zinc sulphide minerals in acidified ferric sulphate solutions. The results suggested that the important parameters involved are temperature and ferric ion concentration, and that the dissolution rates are rapid, at least near the solution boiling point. The reaction involved when using ferric sulphate solutions can be... 

Lead The production of lead from lead sulphide minerals, principally galena, PbS, is considerably more complicated than the production of zinc because tire roasting of the sulphide to prepare the oxide for reduction produces PbO which is a relatively volatile oxide, and therefore the temperature of roasting is limited. The products of roasting also contain unoxidized galena as well as die oxide, some lead basic sulphate, and impurities such as zinc, iron, arsenic and antimony. 

There are new ideas and experiments on the rTCA cycle. A group from Harvard University studied some reaction steps in the rTCA cycle which were kept going by mineral photochemistry. The authors assumed that solar UV radiation can excite electrons in minerals, and that this energy is sufficient to initiate the corresponding reaction steps. In this photocatalytic process, semiconductor particles were suspended in water in the presence of a zinc sulphide colloid (sphalerite) the experiments were carried out in a 500 mL reaction vessel at 288 K. Irradiation involved a UV immersion lamp (200-410 nm) in the photoreactor. Five reactions out of a total of 11 in the rTCA cycle were chosen to check the hypothesis ... 

In general, the calceous-dolomitic rocks from the Cambrian age are affected by their upper beds, by sulphide mineralization of lead, zinc and iron contemporaneous with sedimentation. The oxide lead and zinc minerals are disseminated through dolomitic limestone. As a consequence of the action of the descending process, these formations may assume different types of mineralization. According to the intensity of the oxidation process, which is associated with the different characteristics of the country rock, this country rock may be (a) principally calceous, (b) calceous with dolomitized zones and (c) primarily dolomitized. 

Treatment of mixed lead zinc sulphide oxide ores with barite-calcite gangue minerals... 

There are only few operations treating mixed lead zinc sulphide oxide ores that contain barite-calcite gangue minerals. A typical example of such an operation is the Tynagh oxide complex in Ireland [11]. In this deposit, the oxide ores are generally located at the bottom and at the ends of the sulphide mud ores. The major gangue mineral is barite (large quantities) and minor amounts of clay. This ore assays 8.5% Pb(total), 6% Pb(oxide), 6.8% Zn(total) and 5% ZnO. 

Some oxide-type minerals have been found to luminesce when irradiated. A simple example is ruby (aluminium oxide with chromium activator), which emits bright-red light. The phosphors are incorporated into colour television screens to emit the colours blue (silver-activated zinc sulphide), green (manganese-activated zinc orthosilicate), and red (europium-activated yttrium vanadate). 

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). 

Modifiers in the flotation of sulphide minerals mainly include depressants and activators. A depressant is defined as a reagent which inhibits the adsorption of a collector on a given mineral or adsorbed on the mineral to make the siuface hydrophilic, and includes inorganic depressants such as lime, sodium cyanide, sulphin dioxide, zinc sulphate, sodium sulphide etc., and organic depressants such as sulfhydryl acetic acid, polyacrylamide polymers containing various functional groups etc. In this chapter, roles of depressants in the flotation sulphide minerals will be discussed and some new organic depressants will be introduced. 

Figure 5.31 Zeta potential of zinc-iron sulphide minerals as a function of pH...

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

Table 6.1 Eh-pH area of flotation of Zinc-Iron sulphide minerals in the presence of 10 mol/L Cu with 10 mol/L butyl xanthate as a collector...

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... 

Figure 6.11 Flotation response of zinc-iron sulphide minerals as a function of pH in the presence of 120 mg/L GXl and 1.0 x 10 mol/L CUSO4 with butyl xanthate as a collector...

Figure 6.13 and Fig. 6.14 demonstrate the flotation results of zinc-iron sulphide minerals with l.Ox lO mel/L butyl xanthate as a collector in the presence of (1-carbonic sodium-2-hydroxyl) sodium propronate dithio carbonic sodium (TX3) or (1-carbonic sodium-2-sodium acetate) sodium propronate dithio carbonic... 

Besides, the polarization resistance of sphalerite electrode is the highest among lead-zinc-iron sulphide minerals, illustrating its poor conductivity of ZnS. 

Lead-Zinc-Iron-Sulphide Minerals and Ores... 

Pozzo, R. L., Malicsi, A. S., Iwasaki, L, 1988. Pyrite-pryyhotite-grinding media contact and its effect on flotation. Minerals Metallurgical Processing, 5(1) 16-21 Pozzo, R. L., Malicsi, A. S., Iwasaki, I., 1990. Pyrite-pyrrhotite-grinding media contact and its effect on flotation. Minerals Metallurgical Processing, 7(1) 16 - 21 Prestidge, C. A., Thiel, A. G., Ralston, J., Smart, R. S. C., 1994. The interaction of ethyl xanthate with copper (II)—activated zinc sulphide kinetic effects. Colloids Surfece, A. Physicochem. Eng. Aspects, 85 51 - 68... 

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