Lower limiting flotation potential

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. 

From the Eqs. (3-1) to (3-13), the h-pH diagram of sodium sulphide solution is constructed with element sulphxir as metastable phase considering the presence of barrier (about 300kJ/mol) or overpotential (about 3.114 mV) of sulphide oxidation to sulphate and shown in Fig. 3.7. It is obvious that the lower limit of potential of sodium sulphide-induced collectorless flotation of pyrite, pyrrhotite and arsenopyrite at various pH agree well with the potential defined respectively by reactions of Eq. (3-9) producing elemental sulphur. The initial potential... 

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. 

Figure 4.13 The lower (E ) and rqjper limiting flotation potential of jamesonite as a function of pH (1-EX, 2-DDTC, collector concentration 1 xlO" mol/L)...

Figure 4.30 Electrochemical phase diagram for the butyl xanthate/oxygen system and the observed lower and upper ( ) limiting flotation potential of galena and chalcopyrite at which flotation recovery is greater than 50% (EX 2 xlO mol/L)...

The lower and upper limit flotation potential of pyrrhotite activated by copper ion change with pH as shown in Fig. 6.6. At pH = 4.5, pyrrhotite exhibits better flotation response with recovery about 80% in the potential range of 0.25-0.65 V indicating the stronger activation of copper ion. At pH =6.5, the recovery of pyrrhotite reaches 80% around potential 0.3V. At pH = 9.2, the floatability of pyrrhotite is low. 

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. 

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...

Figure 2.14 Electrochemical phase diagram for chalcopyrite with elemental sulphur as metastable phase. Equilibrium lines (solid lines) correspond to dissolved species at 10 mol/L. Plotted points show the upper and lower limit potential of collectorless flotation of chalcopyrite reported from Sun (1990), Feng (1989) and Trahar (1984)...

The h-pH diagram of galena is constructed through the reactions (2-12) to (2-14) and (2-21) to (2-23) and presented in Fig. 2.15. It may be seen from Fig. 2.15 that the lower limit potential of collectorless flotation of galena at various pH are well defined by the conditions producing elemental sulphur. The upper limit potential of self-included collectorless flotation of galena at various pH is... 

The h-pH diagrams of surface oxidation of arsenopyrite and pyrite are shown in Fig. 2.16 and Fig. 2.17, respectively. Figure 2.16 shows that jBh-pH area of self-induced collectorless flotation of arsenopyrite is close to the area forming sulphur. The reactions producing elemental sulphur determine the lower limit potential of flotation. The reactions producing thiosulphate and other hydrophilic species define the upper limit of potential. In acid solutions arsenopyrite demonstrates wider potential region for collectorless flotation, but almost non-floatable in alkaline environment. It suggests that the hydrophobic entity is metastable elemental sulphur. However, in alkaline solutions, the presence of... 

The cyclic voltammetry for sphalerite electrode is presented in Fig. 2.22. It follows from Fig. 2.22 that the potential range of collectorless flotation of sphalerite is 155-270 mV. For the collectorless flotation of sphalerite, the lower limit of flotation corresponds to the following reactions ... 

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 ... 

The collector flotation of chalcocite has been studied in some detail (Basiollio et al., 1985 Heyes and Trahar, 1979 O Dell et al., 1984 Richardson et al., 1984, 1985 Walker et al., 1984). Figure 4.2 compares the results reported by different authors. It can be seen that the lower potential limit of flotation found in the different experimental conditions agrees favorably and is independent of pH but the upper limit is pH dependent. 

The influence of pulp potential on the flotation of marmatite, arsenopyrite and pyrrhotite with 10 mol/L butyl xanthate as a collector in the presence of 150 mg/L 2,3-dihydroxyl propyl dithiocarbonic sodium (GX2) has been tested. Taking the flotation recovery to be 50% as a criterion, above which the mineral is considered to be floatable and otherwise not floatable, the upper and lower potential limits of the flotation of marmatite, arsenopyrite and pyrrhotite at different pH are presented in Fig. 5.25 and Table 5.1. It is evident that marmatite is floatable in some range of potential at various pH, whereas arsenopyrite and pyrrhotite are not floatable in the corresponding conditions. It suggests that the flotation separation of marmatite from arsenopyrite and pyrrhotite may be... 

Figure 5.25 The upper and lower potential limits of marmatite flotation with butyl xanthate as a collector in the presence of GX2...

The Eh-pH diagrams shown in Fig. 29 portray the region of chemisorption as extending nearly 0.3 V below the stability zone of copper(I) xanthate. At high Eh values, chalcocite is oxidized to copper sulfides of progressively lower copper content. Chemisorbed xanthate will not coexist with these sulfides when CuO is formed since the oxide is expected to overlay the surface of the mineral. This implies that there is an upper potential limit to flotation of chalcocite with ethyl xanthate, and such behavior has been established for this system. ... 

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