Pulp potential

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

Heyes and Trahar (1984) leached pyrite with cyclohexane and compared the extract with a sulphur-containing solution of cyclohexane in a UV spectra photometer as shown in Fig. 1.4, indicating that sulphur was present at the mineral surface. Therefore, the inherent hydrophobicity and natural floatability once thought to be typical of sulphides is now thought to be restricted to sulphides such as molybdenite and other minerals or compound with special structural features. The collectorless floatability that most sulphide minerals showed came from the self-induced or sulphur-induced flotation at certain pulp potential range and certain conditions. 

The presence of oxygen enhances the formation of the surface coating and depresses the flotation of pyrrhotite. It appears, therefore, that although the floatability of individual mineral may be controlled by pulp potential, the presence of several sulphide minerals, particularly when they are ground with steel media, leads to galvanic interaction among them and the alteration of certain mineral surfaces may be accelerated. Then the pulp potential dependence of their floatability may not follow those of individual mineral. 

The collectorless floatability of chalcopyrite has been studied in some detail and some results are shown in Fig. 2.5 (Guy and Trahar, 1985 Wang, 1992). It has been found that there is a clear distinction between flotation and non-flotation, which appear to be pH and dependent. The upper limit and lower limit of pulp potential for collectorless flotation of chalcopyrite change with pH. 

Figure 2.7 Effect of pulp potential on collectorless flotation behaviors of pyrite and pyrrhotite...

Figures 2.6, 2.7 and 2.8 provided the evidence that there exists the critical upper and lower limit of pulp potential for collectorless flotation at certain pH. Figure 2.9 further demonstrated the flotation recovery of jamesonite as a function of potential at different pH. It is obvious that jamesonite has very good collectorless floatability in different potential range, which much depended on different pH. The...

The influences of pulp potential on the Na2S -induced flotation of pyrite at pH = 8 was examined by Heyes and Trahar (1984) for an initial sodium concentration of 10 mol/L. The region of fairly strong Na2S -induced floatability over a wider potential range between 0 and 0.5 V was reported. They noted that the floatability... 

McCarron et al. (1990) used the X-ray photoelectron spectroscopy to analyze chalcopyrite and pyrite surface after being conditioned in sodium sulphide solutions. They found that multilayer quantities of elemental sulphur were produced at the surface of both minerals in 3 x 10 and 3 x 10" mol/L sulphide solutions although for a given sulphide concentration, the surface coverage of elemental sulphur for p)uite was greater than that for chalcopyrite under open circuit conditions. Eliseev et al. (1982) concluded that elemental sulphur was responsible for the hydrophobicity of pyrite and chalcopyrite treated with sodium sulphide. Luttrell and Yoon (1984a, b) observed a shoulder due to elemental sulfixr near 164 eV in the S (2p) spectra from relatively pure chalcopyrite floated after being conditioned at different pulp potential established by different hydrosulphide concentration. 

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. 

Pulp Potential Dependence of Collector Flotation and Hydrophobic Entity... 

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 ... 

Figure 4.4 Flotation recovery of chalcopyrite as a function of pulp potential...

Figure 4.6 Relation between recovery of galena and pulp potential in the presence of condition (BX lO mol/L, KNO3 0.1 mol/L flotation time 2 min, at natural pH)...

The influence of pulp potential on floatability of jamesonite is shown in Fig. 4.12 for an initial concentration of 1 x 10 mol/L ethyl xanthate (EX), dithiocarbamate (DDTC) and ammonium dialkyl dithio-phosphate (ADDP). If the upper and lower... 

Figure 4.12 Flotation recovery of jamesonite as a function of pulp potential in the presence of collector (collector concentration 10" mol/L, pH = 8.8)...

Figure 4.13 presents the lower (E h ) and upper (E h ) limiting flotation potential of jamesonite as a function of pH with collector concentration of 1 xl0 mol/L. It can be seen that the lower (E ) and upper (Et ) limiting flotation potential is changed with the pH value. The flotation of jamesonite may occur only at a range of pulp potential E < h < E - The flotation potential with DDTC as a collector is higher than that with EX as a collector. 

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 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... 

Figure 4.20 Flotation recovery of marmatite as a function of pulp potential with ethyl xanthate as a collector at different pH (KEX 10" mol/L)...

Figure 4.21 reveals the influence of pulp potential on the flotation of marmatite at different pH using dithiocarbamate as a collector. Figure 4.21 shows that marmatite has good floatability with a maximum recovery of about 90% in acidic pH media with a potential range 300 - 750 mV when DDTC is used as a collector. In alkaline pH media, the floatability of marmatite becomes very poor in various potential regions. If the collector metal salt was formed into marmatite like sphalerite, the reaction between marmatite and dithiocarbamate may be written simply as follows ... 

The relationship between pyrrhotite flotation recovery and pulp potential is presented in Fig. 4.26. It can be shown that the flotation of pyrrhotite has different... 

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