Mineral film flotation

The large Canadian oil-sands surface-mining and water-based flotation processing operations involve a number of kinds of emulsions and foams in a variety of process steps. Whereas mineral ore flotation relies on wettability alteration and bubble attachment, oil and bitumen flotation rely more on attachment and filming to create an oleic foam. 

The flotational separation and enrichment of minerals is one of the most broadly used technological applications that utilizes the control of wetting. Flotation is usually classified as foam (froth), oil, or film flotation, and is based on the difference in wetting of the valuable (flotated) mineral that is to be extracted or concentrated, and the gangue (a barren rock). In froth and... 

Flotation. The slurry of ground ore leaving the grinding circuit may be separated from part of the water in thickeners or may go directly to the flotation cells. The latter are rectangular tanks into which air is injected or drawn via impellers. Flotation is based on producing a water-repellent chemical film on the exposed sulfide minerals in the ground ore. The sulfide minerals collect on the surface of the air bubbles and rise to the top of the flotation cell, where they can be removed from the froth. The froth overflows the cells in collector troughs called launders. 

The flotation of sphalerite, the sulfidic mineral source of zinc, is next considered as an example to illustrate the role of activators. This mineral is not satisfactorily floated solely by the addition of the xanthate collector. This is due to the fact that the collector products formed, such as zinc xanthate, are soluble in water, and so do not furnish a hydrophobic film around the mineral particles. It is necessary to add copper sulfate which acts as an... 

The rest of the chapter has been devoted to special topics and in materials science there are many possibilities. Those selected include the mechanism of the flotation of minerals in which the addition of a certain organic to the solution causes a specific mineral to become hydrophobic so that it is exposed to air bubbles, the bubbles stick to it and buoy the mineral up to the surface, leaving unwanted minerals on the bottom of the tank. It turns out that the mechanism of this phenomenon involves a mixed-potential concept in which the anodic oxidation of the organic collector, often a xanthate, allows it to form a hydrophobic film upon a semiconducting sulfide or oxide, but only if there is a partner reaction of oxygen reduction. This continues until there is almost full coverage with the dixanthate, and the surface is thereby made water-repelling. 

By the use of other reagents certain oxidized ores may be floated. For the oxides and carbonates of basic metals, fatty acids such as oleic, and soaps, are frequently useful. These no doubt form an oriented thin film of the soap of the heavy metal present in the mineral, by double decomposition with the surface layer the long hydrocarbon chain is probably oriented outwards. By special activation it is said that even quartz may be floated by the judicious use of soaps, if its surface is contaminated naturally or artificially with small amounts of heavy metals. There would appear to be a vast range of possibilities in the separation of complex minerals, by proper selection of reagents capable of modifying their surfaces. A detailed study of the flotation of various silicate minerals, with oleic acid, has been given by Patek.4... 

Many theories have been advanced concerning the mechanisms involved in surfacing the mineral particles so as to create a hydrophobic hydrocarbon film on the mineral surface, and many investigations have been carried out to define these mechanisms. When firoth flotation is used in an aqueous medium that carries the solids to be separated (together with dispersed air bubbles and possibly an organic liquid) a three- or possibly a four-phase system must be considered. In most froth flotation processes, the solid particles are initially completely water-wetted, and the solid-liquid interface must be replaced by... 

Use Boiler water compounds, detergents, textiles, leather tanning, photographic film developing, deflocculation of clays, flotation and desliming of minerals, dispersion of pigments, paper processing, industrial and municipal water treatment. 

A mineral particle will attach itself to an air bubble and float when its surface is hydrophobic, or water-repellent and conversely, a particle with a hydrophilic, or water-attractive, surface will not become attached to an air bubble. Practically all minerals as they occur are hydrophilic. It is the function of one class of flotation agents, called promoters or collectors, to convert the surface of the mineral to be floated from a hydrophilic to a hydrophobic state. At the same time, the collector must not alter the hydrophilic surface of the gangue, which is to stay behind. One theory as to how this is done is that the collector is selectively adsorbed and oriented on the mineral surface to form a hydrophobic film. 

The usual representation of oil-sand structure is shown in Figure 1, where the bitumen is not in direct contact with the mineral phase, but instead is separated by at least a thin film of water. The separation of oil from solids by a water film is widely held to be the characteristic difference between Athabasca oil sand and oil sand from other oil-sand deposits in the world (e.g., California, New Mexico, or Utah). These other oil-sand deposits are thought to consist of oil-wet solids. That is, the bitumen occurs in direct contact with the mineral grains. The significance of the distinction is that the oil-wet oil sands are considered to be more difficult to beneficiate using hot-water flotation because of the difficulty in dislodging bitumen from an oil-wet surface. 

Uses Binder, emulsion stabilizer, vise, control agent, emulsifier, film-former, protective colloid, stabilizer, suspending agent, thickener in foods, cosmetics, pharmaceuticals thickener, protective colloid in emulsion paints, adhesives binder in ceramics suspending agent in PVC polymerization protective colloid in suspension polymerization mineral flotation depressant hair preps. in blow-molded bottles tablet coating aid in... 

Uses Antistat, binder, emulsion stabilizer, film-former, vise, control agent, thickener, suspending agent, stabilizer, slip agent, flocculant in cosmetics mineral flotation depressant textile auxiliaries vise, builder for oil-well workover/completion fluids binder, surfactant, lubricant, plasticizer in ceramics dry str. and formation aid in mfg. of paper/paperboard in contact with aq.ffatty foods... 

After bitumen-solid separation, bitumen-air attachment has to occur. The process conditions that most favour bitumen-solids separation, that is a high degree of electrostatic repulsion due to charged surfactant molecules at the interfaces, also tend to oppose gas-bitumen attachment since the gas bubbles also acquire a surface charge of the same sign [JJ2] (see Figure 14). In comparison, mineral flotation involves gas-solid attachment without filming and such electrostatic repulsion is not as... 

Corrosion inhibitor. Easily formulated for desired dispersibility with good film-forming persistency. The acetic acid and hydroxyacetic salts are highly water soluble. Useful in non-metallic mineral flotation. Wetting, emulsifying and antistripping agent with asphalt compounds and coal-tar pitches. 

In the flotation device, the flow of charged air bubbles acts as collector and transporter of ionic impurities of treated water. Through the bubble-film extractor, this flow is removed from treated water. So, the mineral composition of treated water can be corrected, and the target mineral impurities can be extracted. The efficiency of demineralization of treated water can be evaluated if the relationship of bubble charge density upon pH and ionic concentration of water is known. An appropriate empiric equation is the following ... 

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