Complex flotation

A very important but rather complex application of surface chemistry is to the separation of various types of solid particles from each other by what is known as flotation. The general method is of enormous importance to the mining industry it permits large-scale and economic processing of crushed ores whereby the desired mineral is separated from the gangue or non-mineral-containing material. Originally applied only to certain sulfide and oxide ores. 

Sulfide collectors ia geaeral show Htfle affinity for nonsulfide minerals, thus separation of one sulfide from another becomes the main issue. The nonsulfide collectors are in general less selective and this is accentuated by the large similarities in surface properties between the various nonsulfide minerals (42). Some examples of sulfide flotation are copper sulfides flotation from siUceous gangue sequential flotation of sulfides of copper, lead, and zinc from complex and massive sulfide ores and flotation recovery of extremely small (a few ppm) amounts of precious metals. Examples of nonsulfide flotation include separation of sylvite, KCl, from haUte, NaCl, which are two soluble minerals having similar properties selective flocculation—flotation separation of iron oxides from siUca separation of feldspar from siUca, siUcates, and oxides phosphate rock separation from siUca and carbonates and coal flotation. 

Production of KCl at the Wendover, Utah operation employs a large 7000 acre complex of solar ponds. Both shallow brine wells and deeper wells are used to pump brine into the pond complex. In the preconcentration ponds water is evaporated and sodium chloride is crystallized. Later the brine is transferred to production ponds where sylvinite is deposited. Brine is then transferred to other ponds where camaUite is crystallized. Sylvinite is removed from drained ponds with self-loading scrapers and taken to the plant were KCl is separated by flotation with an amine oil collector. The camaUite,... 

For any adsubble method, if the material to be removed (termed the colligend) is not itself surface-active, a suitable surfactant (termed the collector) may be added to unite with it and attach or adsorb it to the bubble surface so that it may be removed (Sebba, Ion Flotation, Elsevier, New York, 1962). The union between colligend and collector may be by chelation or other complex formation. Alternatively, a charged colhgend may be removed through its attraction toward a collector of opposite charge. 

Zhou ZA, Langlois R, Xu Z, Finch JA, Agnew R (1997) In-plant testing of a hydrodynamic reactor in flotation. In Finch JA, Rao SR, Huang LM (eds) Processing of Complex Ores. CIM, Sudbury, Canada, pp 185-193... 

Separation of milled solid materials is usually based on differences in their physical properties. Of the various techniques to obtain ore concentrates, those of froth flotation and agglomeration exploit differences in surface activities, which in many cases appear to involve the formation of complexes at the surface of the mineral particles. Separation by froth flotation (Figure 4) depends upon conversion of water-wetted (hydrophilic) solids to nonwetted (hydrophobic) ones which are transported in an oil-based froth leaving the undesired materials (gangue) in an aqueous slurry which is drawn off from the bottom of the separator. The selective conversion of the ore particles to hydrophobic materials involves the adsorption of compounds which are usually referred to as collectors. 4... 

Selenium Adsorption colloid flotation Spectrophotometry of methylene blue complex - [517,546]... 

Because of the complex nature of gold-containing Cu-Pb-Zn ores, the reagent schemes used are also complex. Reagent modifiers such as ZnS04, NaCN and lime have to be used, all of which have a negative effect on gold flotation. 

Figure 18.1 shows the rate of flotation of different sulphides from operation A (UG2 Complex). In these experiments, xanthate was used as the primary collector with dithiopho-sphate as the secondary collector. 

Morrice, E., Valkiewicz, J.W., and Casale, G., Pilot Plant Flotation of Serpentinized Platinum-Palladium Ore from Stillwater Complex, Report of Investigation 8885, 1976. 

The complex Lodge deposits have quite a complicated flowsheet. Typical examples include operating plants in Australia and South America. An example of a plant that uses both gravity and flotation is the Wheal Jane Concentrator in Cornwall, UK, shown in Figure 21.2. 

A phenomenon observed in both laboratory and pilot plant testing of ores with phosphonic acid collectors is complete cassiterite flotation at a pH below 4.0. In fundamental practice, it indicates that a pH region below 4 is the region of maximum flotation. However, in plant practice, at a low pH (below 4), loss of flotation occurred. The loss of flotation at a low pH has not been established. It is, however, postulated that loss of flotation is believed to be associated with complex solution chemical interaction between phosphonic acid collectors and cationic species, in particular, those of iron, which is always present in industrial flotation pulp. 

The Wheal Jane plant had incorporated flotation together with gravity since start-up of this plant. The flotation development testwork was carried out at the Warren Spring laboratory. The ore treated at the Wheal Jane plant is very complex and finely disseminated. About 86% is less than 50 pm, of which 50% is less than 20 pm. 

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