Dianzuo Wang

Electrochemical Flotation Separation of Sulphide Minerals

This chapter is mainly about potential controlled flotation. First, the factors affecting potential controlled flotation are discussed, such as potential modifiers, pH modifier, frother, conditioning time, surface pretreatment and grinding environment. It is found that the flotation behavior of minerals modified by different potential modifiers or pH modifiers may differ from each other even at the same potential or the same pH. And other factors are also investigated to find the way of influencing the pulp potential to control the flotation behavior of minerals. Thereafter, some examples about potential controlled flotation are presented which are the flotation of copper sulphide minerals and the flotation of lead-zinc-iron sulphide minerals. As the last part, origin potential control flotation (OPCF) is introduced. The factors coupled with OPCF including grinding, lime dosage, aeratation and reagent schemes are all dicussed, which are different from the conventional flotation. In the end listed are some applications of OPCF technology.

Roles of Depressants in Flotation of Sulphide Minerals

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 the flotation behavior, effect of pulp potential, adsorption mechanism and structure-property relation.

Electrochemistry of Activation Flotation of Sulphide Minerals

Two systems are discussed in this chapter, which are copper activating zinc-iron system with and without depressants. Firstly, the system in the absence of depressants is discussed. And it is obtained that at a specific pH the activation for each mineral occurs in a certain range. Through the electrochemical methods and surface analysis the entity contributing to the activation can be identified which are usually copper sulphides and vary for different minerals. Secondly, the system with depressants is researched. And also the effects of pulp potential on the activation are discussed. The same conclusion can be obtained as the one from the former system. Furthermore, zeta potential are involved in the discussion of activation and the mechanism can be explained from the changes of zeta potential. Similarly, the activation mechanism of this system is also studied through solution chemistry, bonding of activator with mineral surfaces and surface analysis.

General Review of Electrochemistry of Flotation of Sulphide Minerals

This chapter reviews the development of froth flotation achieved in the past one hundred years and accounts for the achievements of the theory of flotation of sulphide minerals in four aspects, which are the natural flotability of sulphide minerals, the role of oxygen in the flotation of sulphide minerals, the interaction of collectors with sulphide minerals, the effect of the semi-conductor property of sulphide minerals and electrochemical behaviors in the grinding system. Furthermore, the purpose of this book is revealed in the end.

Mechano-Electrochemical Behavior of Flotation of Sulphide Minerals

This chapter introduces the changes of electrochemical behavior of sulphide minerals leading by mechnical force exerted in the process of grinding, which is called mechano-electrochemical behavior. To investigate it, two new equipments are applied. The configuration of them is illustrated. And the mechano-electrochemical behavior of pyrite and galena is investigated in this chapter. It is found that after grinding the corrosion and oxidation of these mineral surface are inhibited and produce a reduction atmosphere, which may be useful for the interaction between galena and xanthate to form collector salt and not suitable for the formation of dixanthogen. Meanwhile, surface changes of sulphide minerals under mechanical force are also investigated with Nissan mineral phase micro-camera for observing the surface top graph. And the fact turns out to be that among three sulphide minerals the pyrite erodes the fastest and its eroding current is the largest which is consistent with the previous one.

Natural Floatability and Collectorless Flotation of Sulphide Minerals

This chapter first explains the natural flotability of some minerals in the aspect of the crystal structure and demonstates the collectorless flotaiton of some minerals and its dependence on the Eh and pH of pulp. And then the surface oxidation is analysed eletrochemically and the relations of Eh to the composition of the solutions are calculated in accordance with Nernst Equation. The Eh-pH diagrams of several minerals are obtained. Thereafter, electrochemical determination such as linear potential sweep voltammetry (LPSV) and cyclic voltammetry (CV) and surface analysis of surface oxidation applied to the sulphide minerals are introduced. And recent researches have proved that elemental sulfur is the main hydrophobic entity which causes the collectorless flotability and also revealed the relation of the amount of sulfur formed on the mineral surfaces to the recoveries of minerals, which is always that the higher the concentration of surface sulphur, the quicker the collectorless flotation rate and thus the higher the recovery.

Collectorless Flotation in the Presence of Sodium Sulphide

The sodium sulphide-induced collectorless flotation of several minerals are first introduced in this chapter. The results obtained are that sodium sulphide-induced collectorless flotation of sulphide minerals is strong for pyrite while galena, jamesonite and chalcopyrite have no sodium sulphideinduced collectorless flotability. And the nature of hydrophobic entity is then determined through Eh-pH diagram and cyclic voltammogram, which is element sulphur. It is further proved with the results of surface analysis and sulphur-extract. In the end, the self-induced and sodium sulphide-induced collectorless flotations are compared. And it is found that the order is just reverse in sodium sulphide-induced flotation to the one in self-induced collectorless flotation.

Corrosive Electrochemistry of Oxidation-Reduction of Sulphide Minerals

The flotation mechanism is discussed in the terms of corrosive electrochemistry in this chapter. In corrosion the disolution of minerals is called self-corrosion. And the reaction between reagents and minerals is treated as inhibition of corrosion. The stronger the ability of inhibiting the corrosion of minerals, the stronger the reagents react with minerals. The two major tools implied in the research of electrochemical corrosion are polarization curves and EIS (electrochemistry impedance spectrum). With these tools, pyrite, galena and sphalerite are discussed under different conditions respectively, including interactions between collector with them and the difference of oxidation of minerals in NaOH solution and in lime. And the results obtained from this research are in accordance with those from other conventional research. With this research some new information can be obtained while it is impossible for other methods.

Molecular Orbital and Energy Band Theory Approach of Electrochemical Flotation of Sulphide Minerals

In the light of quantum chemistry, sulphide minerals and the interaction of them with reagents are investigated in this chapter. With the density functional theory pyrite is first researched including its bulk properties about energy band and frontier orbitals and the property of FeS2 (100) surface. It is found that surface Fe and S atom have more ionic properties. And both Fe2+ and S2− have high electrochemistry reduction activity, as is the base of oxygen adsorption. Thereafter, the configuration of oxygen adsorping on the surface of pyrite is studied. And from the viewpoint of adsorption energy, the parallel form of oxygen adsorption is in preference to the perpendicular form. Similarly, some properties of ganlena are investigated. Furthermore, the activation of sphalerite is also researched. And the conclusion is that the forbidden gap of doped ZnS will decrease and the electrochemistry activity of ZnS is in return enhanced. The reaction between reagents and minerals is also discussed in the terms of molecular orbital and energy band, which provides a new method to investigate the mechanism of flotation.

Collector Flotation of Sulphide Minerals

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.