Flotation galena

O Dell, C. S., Walker, G. W., Richardson, P. E., 1986. Electrochemistry of the chalcocite-xandiate system. J. Appl. Electrochem., 16 544-554 Opahle, I., Koepemik, K., Eschrig, H., 2000. Full potential band stracture calculation of iron pyrite. Computational Materials Science, 17(2 - 4) 206 - 210 Page, P. W. and Hazell, L. B., 1989. X-ray photoelectron spectroscopy (XPS) studies of potassium amyl xanthate (KAX) adsorption on precipitated PbS related to galena flotation. Inter. J. Miner. Process, 25 87 - 100... 

Grano, S. R., Prestidge, C. A., and Ralston, J. (1997) Solution interaction of ethyl xanthate and sulfite and its effect on galena flotation and xanthate adsorption, Int. J. Miner. Process., 52(2-3), 161-186. 

Basiho C. 1., Kartio 1. J., and Yoon R.-H. (1996) Lead activation of sphalerite during galena flotation. Min. Eng. 

As an example, the data obtained from the Sullivan concentrator of Canada for galena flotation is given below (Bushell, 1958) ... 

Thus, the concentration of xanthate needed for galena flotation will increase with sodium carbonate dosage with the corresponding relation given by ... 

General mechanism of galena flotation using xanthate as collector is attributed to the formation of lead xanthate on the mineral surface ... 

The solubility products (pL) and the dissociation constants (p a) of zinc-xanthates as a function of chain length n) are illustrated in Fig. 5.5. The recovery of galena flotation using xanthates and fatty acids with various chain lengths is shown in Fig. 5.6 [1]. 

Fig. 5.6. The performance of xanthate and fatty acids with various chains for galena flotation 1—methyl 2—ethyl 3—propyl 4—butyl 5—amyl.

It has been reported that in the case of flotation of galena, flotation performance depends on the micro-bubbles contained in the pulp as follows [17] (Table 5.14a). 

The galena would be floated first under conditions of alkaline pH (pH 8-10) using a low concentration of an alkyl xanthate as the collector, sodium sulfite to depress the zinc minerals and a short-chain alcohol as a frother. After galena flotation, the pH would be raised to 11-12 (to depress gangue iron sulfides) copper sulfate is added to activate sphalerite and marmatite additional alkyl xanthate is added to float these two minerals. The final lead concentrate should be more than half lead with minimal zinc content the final zinc concentrate should be more than half zinc with minimal lead content. 

Activators enhance the adsorption of collectors, eg, Ca " in the fatty acid flotation of siUcates at high pH or Cu " in the flotation of sphalerite, ZnS, by sulfohydryl collectors. Depressants, on the other hand, have the opposite effect they hinder the flotation of certain minerals, thus improving selectivity. For example, high pH as well as high sulfide ion concentrations can hinder the flotation of sulfide minerals such as galena (PbS) in the presence of xanthates (ROCSS ). Hence, for a given fixed collector concentration there is a fixed critical pH that defines the transition between flotation and no flotation. This is the basis of the Barsky relationship which can be expressed as [X ]j[OH ] = constant, where [A ] is the xanthate ion concentration in the pulp and [Oi/ ] is the hydroxyl ion concentration indicated by the pH. Similar relationships can be written for sulfide ion, cyanide, or thiocyanate, which act as typical depressants in sulfide flotation systems. 

Depressants are reagents that selectively prevent the reaction between a coUector and a mineral, thus preventing its flotation. For example, sodium cyanide [143-33-9] depresses sphalerite [12169-28-7] (zinc sulfide) and pyrite [1309-36-0] (iron sulfide) but not galena. It thus enhances selective flotation of the galena. 

A simple two-mineral separation, say of galena (specific gravity 7.5) from a siliceous gangue (specific gravity 2.65) can be taken as a good example to illustrate the process. The flotation operation comprises the following successive steps. 

The attachment of minerals to the bubbles, which is the heart of the flotation process, occurs. Once this occurs, gravity completes the separation readily. In the present example, galena attaches itself to the bubbles and thereby its effective density is drastically reduced. This causes galena to buoy up in spite of the fact that it is, in reality, much heavier than the siliceous gangue. 

The galena-bearing froth is removed from the top and the impoverished tailing is drawn away from the bottom of the cell. A device in which all these processes take place is called a flotation cell (Figure 2.20). 

Native gold and its alloys, which are free from surface contaminants, are readily floatable with xanthate collectors. Very often however, gold surfaces are contaminated or covered with varieties of impurities [4], The impurities present on gold surfaces may be argentite, iron oxides, galena, arsenopyrite or copper oxides. The thickness of the layer may be of the order of 1-5 pm. Because of this, the flotation properties of native gold and its alloys vary widely. Gold covered with iron oxides or oxide copper is very difficult to float and requires special treatment to remove the contaminants. 

Figure 1.1 Effect of pulp potential on self-induced collectorless flotation behaviors of galena and arsenopyrite at pH = 6 (Sun, 1990)...

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