Flotation behavior

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

Therefore, it has been concluded that the reduction of oxygen as a cathodic process was essential for the electrochemical reaction on sulphide surface and was different for various sulphide minerals. The reduction of oxygen affected the oxidation of sulphide minerals and the interactions with collectors, which had a pronounced influence on flotation behavior of sulphide minerals (Ahmed, 1978 Buckley et al., 1985, 1995 Woods, 1984,1994 Hu et al., 2004 Yu et al., 2004a Zhang et al., 2004a, d). 

This book systematically summarizes the researches on electrochemistry of sulphide flotation in our group. The various electrochemical measurements, especially electrochemical corrosive method, electrochemical equilibrium calculations, surface analysis and semiconductor energy band theory, practically, molecular orbital theory, have been used in our studies and introduced in this book. The collectorless and collector-induced flotation behavior of sulphide minerals and the mechanism in various flotation systems have been discussed. The electrochemical corrosive mechanism, mechano-electrochemical behavior and the molecular orbital approach of flotation of sulphide minerals will provide much new information to the researchers in this area. The example of electrochemical flotation separation of sulphide ores listed in this book will demonstrate the good future of flotation electrochemistry of sulphide minerals in industrial applications. 

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

The reaction potential producing elemental sulphur are 0.24 V at pH = 6 based on the reaction (2-10), 0.28 V at pH =8 on the reaction (2-11), and 0.1 V at pH = 11 on die reaction (2-12) with lO" mol/L concentration of dissolved species. The reported flotation initial potential (see Table 2.1) are very close to these theoretical calculation values. The theoretical and experimental values in Table 2.1 indicate that the elemental sulphur might be responsible for the hydrophobicity of sulphide surfaces. At different pH media the formation of elemental sulphur occurs and hence the flotation behavior undergoes different processes. 

Pyrite and arsenopyrite have similar oxidation and self-induced collectorless flotation behavior. It is generally suggested that anodic oxidation of pyrite occurs according to reactions (2-24) in acidic solutions (Lowson, 1982 Heyes and Trahar, 1984 Trahar, 1984 Stm et al., 1991 Chander et al., 1993). The oxidation of pyrite in basic solutions takes place according to reactions (2-25). Since pyrite is flotable only in strong acidic solutions, it seems reasonable to assume that reaction (2-24) is the dominant oxidation at acidic solutions. Whereas pyrite oxidizes to oxy-sulfur species with minor sulphur in basic solutions. 

There is significant agreement between the lower potential boundary of the flotation region and the potential at which the anodic ciurent begins in a potential sweep. The amoimt of extracted sulphur on the sulphide minerals can be correlated with their collectorless flotation behaviors. The higher the concentration of surface sulphur, the faster the collectorless flotation rate and thus the higher the recovery. 

However, the decomposition potential of zinc xanthate into dixanthogen is above 0.3 V according to reactions (4-33) or (4-34) and the upper potential limit of flotation of marmatite extends to 620 mV, which indicates the coexistence of dixanthogen on marmatite in this condition. The difference of flotation behavior and hydrophobic entity between sphalerite and marmatite may be due to the existence of iron in marmatite. 

Abstract In this chapter, the depression mechanism of five kinds of depressants is introduced respectively. The principle of depression by hydroxyl ion and hydrosulphide is explained which regulates the pH to make the given mineral float or not. And so the critical pH for certain minerals is determined. Thereafter, the depression by cyanide and hydrogen peroxide is narrated respectively which are that for cyanide the formation of metal cyanide complex results in depression of minerals while for hydrogen peroxide the decomposition of xanthate salts gives rise to the inhibitation of flotation. Lastly, the depression by the thio-organic such as polyhydroxyl and poly carboxylic xanthate is accounted for in detail including die flotation behavior, effect of pulp potential, adsorption mechanism and structure-property relation. 

Flotation Behavior of Zinc-Iron Sulphide mth Polyhydroxyl and Polycarboxylic Xanthate as Depressants... 

P. Somasundaran, "The Relationship Between Adsorption at Different Interfaces and Flotation Behavior", Trans. AIME,... 

Comparing the sedimentation or flotation behavior of differently formed floes, as shown in Figure 5, indicates that the efficiency of a flotation unit of a geometry similar to that of the design D sedimentation tank is noticeably higher for the not so readily coagulating suspension (Al3+). Upgrading inefficient sedimentation seems possible when Al3+ salts are used for floe formation. 

Zhao, S. G., Zhong, H., and Liu, G.Y., Effect of quaternary ammonium salts on flotation behavior of aluminosihcate minerals, J. Centr. South Univ. Technol.. 14. 500, 2007. 

Natarajan, R. and Fuerstenau, D.W., Adsorption and flotation behavior of manganese dioxide the presence of octyl liydnixainale, Int. J. Miner. Process., 11, 139, 1983. 

Most of the theories on interactions of surfactants with minerals are closely related to their solution chemistry. For example, the ion-exchange adsorption theory proposed by Gaudin (1932, 1934) and Wark (1938) and the molecular adsorption theory proposed by Cook and Nixon (1950) are based on the dissociation equilibria and states of the collectors in water. More recently, Somasundaran (1976) observed that ion-molecule complexes of long-chain surfactants in flotation systems can have high surface activity depending upon the association equilibria of the surfactants in solutions (Ananthapadmanabhan et al., 1979 Kulkarni and Somasundaran, 1980). Also the cationic flotation behavior of salt type minerals is closely related to the formation of alkyl amine salt (Hu and Wang, 1990). In this chapter, solution equilibria of reagents relevant to selected flotation systems are examined. 

The pHo values of some amphoteric flotation reagents are shown in Table 2.5 (Nemethy and Scheraga, 1962). The PZC values of various minerals are given in Chapter 3. The relationship between flotation behavior of salt type minerals and solution equilibria of alkyl amino phosphoric acid has also been reported (Hu et al., 2003). 

Ct = 1.0 X 10 mol/1 is shown in Fig. 2.7. In this case the neutral molecule (RNH2) precipitates in the high pH range and the ionic forms RNH and (RNHs) " dominate in the acidic pH range. Again, the ion-molecular complex exhibits a maximum at certain pH values. In this case also, the pH dependence of surface tension of amine solution and the flotation behavior of silica using amine have been correlated with the activities of the species. 

When mineral particles are contacted with water, they will undergo dissolution, the extent of which is dependent upon the type and concentration of chemicals in solution. The dissolved mineral species can undergo further reactions such as hydrolysis, complexation, adsorption and even surface or bulk precipitation. The complex equilibria involving all such reactions can be expected to determine the interfacial properties of the particles and their flotation behavior. The concentration of each dissolved mineral species can be calculated from various solution equilibria of the minerals. The calculated results are plotted as log C-pH diagram. The equilibria in selected salt-type mineral systems with special reference to calcite and apatite are examined below. 

In many flotation systems, the electrical nature of the mineral/water interface controls the adsorption of collectors. The flotation behavior of insoluble oxide minerals, for example, is best understood in terms of electrical double-layer phenomena. A very useful tool for the study of these phenomena in mineral/water systems is the measurement of electrokinetic potential, which results from the interrelation between mechanical fluid dynamic forces and interfacial potentials. Two methods most commonly used in flotation chemistry research for evaluation of the electrokinetic potential are electrophoresis and streaming potential. 

Correlation of oleate adsorption and flotation maximum at about pH 7.5 for a variety of minerals and high abstraction (adsorption + surface precipitation) below this pH with the species distribution diagram (Fig. 4.9) suggests that the role of acid-soap dimer and precipitated oleic acid can be significant in controlling the adsorption and resultant flotation behavior. 

In 1940 s, Taggart (Taggart et al 1930) proposed that flotation behavior of minerals is determined by chemical reactions between reagents and metallic species of minerals in solution. The solubility products of reaction compounds is normally used as the criteria. 

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