Mineral flotability

The problem of mineral flotability above the CMC with respect to the appearance of adsorption maxima has not yet been systematically studied. The aim of this paper was to correlate the adsorption maxima and the flotability of minerals with the kind of potential determining ions. 

The mineral flotability was calculated from kinetic data in a modified Hallimond tube T ). All measurements were performed at 25.0 + 0.2 °C. 

At concentration > CMC, mineral flotability rapidly decreases regardless of the character of PDIs. This decrease in flotability is in a good agreement with the occurrence of adsorption maxima and gives evidence of the change in the character and structure of the adsorption layer. 

The mechanism of interaction of an anionic surfactant with a mineral surface occupied with PDIH+ and OH- is confirmed by the position of IP in relation to the optimum of mineral flotability. If IP of a mineral occurs at a lower pH than the flotability optimum the adsorption of the nondissociated component of the surfactant is negligible. If the condition... 

Several reviews on ore processing by flotation are available.17-21 In addition to providing details of the chemistry of collectors they describe the use of activators and depressants. The former usually convert the surfaces of an ore particle which does not bind strongly to conventional collectors to one that does. The addition of Cu2+ ions to enhance the flotability of minerals such as sphalerite, a zinc sulfide, has been exploited for some time.4 Formation of a surface layer of CuS has been assumed to account for this, but the mechanisms and selectivities of such processes continue to be investigated.18,22,23... 

Abstract 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 h and pH of pulp. And then the surface oxidation is analysed eletrochemically and the relations of E to the composition of the solutions are calculated in accordance with Nemst Equation. The E h-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. 

Abstract 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 sulphide-induced collectorless flotability. And the nature of hydrophobic entity is then determined through J h-pH diagram and cyclic voltammogram, which is element sulphur. It is further proved widi 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. 

The flotation of minerals is based on different attachment forces of hydrophobized and hydrophilic mineral particles to a gas bubble. Hydrophobized mineral particles adher to gas bubbles and are carried to the surface of the mineral dispersion where they form a froth layer. A mineral is hydrophobized by the adsorption of a suitable surfactant on the surface of the mineral component to be flotated. The hydrophobicity of a mineral particle depends on the degree of occupation of its surface by surfactant molecules and their polar-apolar orientation in the adsorption layer. In a number of papers the relationship was analyzed between the adsorption density of the surfactant at the mineral-water interface and the flotability. However, most interpretations of adsorption and flotation measurements concern surfactant concentrations under their CMC. 

The appeareance of maxima on the adsorption isotherms and decrease in flotability can be explained by the hypothesis that in the presence of micelles no adsorption layer of the surfactant can be formed, the character of which corresponds to the equilibrium state only with monomers (sufficiently hydrophobic adsorption layer). Due to a heterogeneity of forces acting at the surfactant ion mineral interface it can be assumed that at concentrations S CMC some of the molecules will be bound much more firmly in a three-dimensional micelle than in... 

If IP of a mineral occurs at a higher pH than the flotability optimum, the nondissociated acid acts as a hydrophobizing component and it holds ... 

Dixit and Biswas124 dealt with the relationship between H+ an OH- concentrations and adsorption of an anionic collector on a mineral surface and its flotability. They used the system zircon-Na oleate. If Na oleate is dissolved in water the following equilibrium sets up ... 

Quartz Fatty acids, a mitres Fatly acids, amines Stanch, dextrin Flotation of bemetite using fatty acids around anutral pH and reverse flotation of quartz using amines Easily flotable in tbe acidic range calcite is usually present as ihe gargue in other salt-type minerals... 

On the basis of the IR data, the general consensus is that when minerals exhibit 100% flotability, several types of chemisorbed oleate as well as precipitated calcium oleate are present at the surface, in agreement with the initial hypothesis of Peck [425]. However, there is controversy concerning the assignment of the adsorption bands of adsorbed oleate and, hence, the structure of surface species. It stems from the strong dependence of the oleate-calcium coordination on the deposition and precipitation conditions-an effect well known for L monolayers and LB films of alkanoates [426]. The amount of oleate adsorbed on a fluorite slab, as measured by IR spectroscopy, is quite different than that for fine fluorite particles [412]. For the slab, there exists an adsorption saturation point, but for fine particles, the amount of adsorbed oleate increases with concentration, although the concentration dependence of the amount of oleate in the... 

Froth flotation separation of minerals requires the mineral of interest to have a hydrophobic surface while the other minerals present in the pulp (a mixture of 25% m/m powdered ore with water) are hydrophilic [361, 362]. The particles of the hydrophobic mineral can be captured by the gas bubbles and raised to the pulp surface where they are collected to the froth. Flotability of the mineral depends not only on the amount of adsorbed hydrophobizing reagent (the collector), which in most cases does not exceed a monolayer, but also on the form in which it is adsorbed [361, 363]. 

Activators are used for enhancing flotation of the minerals that may not possess any flotability in their absence. Flotation of quartz using calcium salts and of sphalerite using copper sulfate (see Fig. 16.4-2) are typical examples of activation. In the case of oleate flotation of quartz in the presence of calcium, activation can be attributed to electrostatic adsorption of the calcium ions on the negatively charged quartz... 

Naturally flotable modifiers are for jpuigue depression graphite, being soft, can coat other minerals and thus cause difficulties... 

Flotation properties of pentlandite are not well umforstood notability is in between chalcopyrite and pyrrhotite Naturally flotable since MO]S is soft, it can coat other minerals and thus enhance gangue flotation Quartz is the gangue for other minerals it can be floated easily with amines during the flotation of minerals sodium silicate can be used to depress quartz... 

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