Mineral flotation

Metal ore bodies may contain several different minerals that are separated into individual concentrates. These may be slurry-transported in the same pipeline by pumping them in separate batches, each separated by a slug of water to prevent contamination [607]. Such batching also allows pipeline flow to be maintained when the mine or separation site temporarily runs out of ore. 

For reviews and more information on the principles and practice of mineral-slurry pipelining see Refs. [90,615-618]. The relationships among suspension rheology, flow rate, and pressure drop in a pipeline are discussed in Section 6.7.1 and oil pipelining is discussed in Section 11.3.4. 

The raw minerals mined from natural deposits comprise mixtures of different specific minerals. An early step in mineral processing is to use crushing and grinding to free these various minerals from each other. In addition, these same processes may be used to reduce the mineral particle sizes to make them suitable for a subsequent separation process. Non-ferrous metals such as copper, lead, zinc, nickel, cobalt, molybdenum, mercury, and antimony are typically produced from mineral ores containing these metals as sulfides (and sometimes as oxides, carbonates, or sulfates) [91,619,620], The respective metal sulfides are usually separated from the raw ores by flotation. Flotation processes are also used to concentrate non-metallic minerals used in other industries, such as calcium fluoride, barium sulfate, sodium and potassium chlorides, sulfur, coal, phosphates, alumina, silicates, and clays [91,619,621], Other examples are listed in Table 10.2, including the recovery of ink in paper recycling (which is discussed in Section 12.5.2), the recovery of bitumen from oil sands (which is discussed further in Section 11.3.2), and the removal of particulates and bacteria in water and wastewater treatment (which is discussed further in Section 9.4). 

Species recovered Recovered from Industrial process or interest 

Non-ferrous metal sulfides (Cu, Pb, Zn, Ni, Co, Mo, Hg, Sb) Mineral ores Metal production 

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Two main operational variables that differentiate the flotation of finely dispersed coUoids and precipitates in water treatment from the flotation of minerals is the need for quiescent pulp conditions (low turbulence) and the need for very fine bubble sizes in the former. This is accompHshed by the use of electroflotation and dissolved air flotation instead of mechanically generated bubbles which is common in mineral flotation practice. Electroflotation is a technique where fine gas bubbles (hydrogen and oxygen) are generated in the pulp by the appHcation of electricity to electrodes. These very fine bubbles are more suited to the flotation of very fine particles encountered in water treatment. Its industrial usage is not widespread. Dissolved air flotation is similar to vacuum flotation. Air-saturated slurries are subjected to vacuum for the generation of bubbles. The process finds limited appHcation in water treatment and in paper pulp effluent purification. The need to mn it batchwise renders it less versatile. 

Two air-saturation systems suited for use in water treatment are shown in Figure 15 (31). Such mechanisms faciHtate the release of air that generates much finer bubbles than mechanical air dispersion methods used in mineral flotation practice. 

Flotation Reagents. Only one sulfide mineral flotation collector is manufactured from phosphine, ie, the sodium salt of bis(2-methylpropyl)phosphinodithioic acid [13360-78-6]. It is available commercially from Cytec Industries Inc. as a 50% aqueous solution and is sold as AEROPHINE 3418A promoter. The compound is synthesized by reaction of 2-methyl-1-propene [115-11-7] with phosphine to form an iatermediate dialkylphosphine which is subsequently treated with elemental sulfur [7704-34-9] and sodium hydroxide [1310-73-2] to form the final product (14). The reactions described ia equations 10 and 11... 

P. A. Mingione, "Use of AEROPHINE 3418A Promoter for Sulphide Minerals Flotation," Proceedings of the 22nd Mnnual Meeting of the Canadian Mineral Processors, Ottawa, 1990. 

Xanthate esters are prepared by reaction of isopropyl alcohol and carbon disulfide [75-15-0]. Isopropyl xanthates have wide use ia mineral flotation (qv) processes, and sodium isopropyl xanthate [140-93-2], C4HyOS2Na, is a useful herbicide for bean and pea fields (see Herbicides) (30). 

Mechanical flotation machines are most commonly used in the mineral industiy, while pneumatic column-type units are gaining popularity in recent years. Surveys by Harris (1976), Young (1982), Bar-beiy (1982), and Mavros (1991) provide a detailed overview of the process-engineering aspec ts of mineral flotation devices in particular and systems in general. 

S. K. Mishra, Anionic Collectors in Non-sulfide Mineral Flotation, in Reagents in Mineral Technology, P. Somasundaram and B. K. Moudgil, eds., vol. 27, Surfactant Science Series, Mercel Dekker Inc., p. 195, New York, 1988. 

Nonsolvent bath, polymer precipitation by immersion in, 15 808-811 Nonspecific elution, in affinity chromatography, 6 398, 399 Nonstationary Poisson process, in reliability modeling, 26 989 Non-steady-state conduction, 9 105 Nonsteroidal antiinflamatory agents/drugs (NSAIDs) 21 231 for Alzheimer s disease, 2 820 for cancer prevention, 2 826 Nonsulfide collectors, 16 649 Nonsulfide flotation, 16 649-650 Nonsulfide mineral flotation collectors used in, 16 648-649t modifiers used in, 16 650, 651t Nonsulfide ores, 16 598, 624... 

Sulfenyl chloride derivatives, 22 106 Sulfenyl chlorides, 23 645 Sulfidation, 23 506-507 Sulfide flotation, 26 649. See also Sulfide mineral flotation Sulfide mineral flotation... 

The saponified fatty acids which are used are most often palmitic, stearic or oleic acid but the way in which they confer a hydrophobic nature to the surface of the ink particle is not well understood. If enough calcium ions are present (and these sometimes need to be added to the system) insoluble calcium salts of the fatty acids are probably produced and these may coat the surface of the print particle making it hydrophobic. The ink particle then adheres to an air bubble and can be floated out of the stock. The saponified fatty acids are often called collectors —a term which comes from mineral flotation. 

Because the oxidation of sulphide has a pronounced effect on sulphide mineral flotation, oxidation will produce metal ions on the mineral surface and these ions will react with collectors to render the surface hydrophobicity. From the DOS shown in Fig. 9.13, Fig. 9.15 and Fig. 9.16, marmatite and (Zn, Cu) S are the intrinsic semiconductors and sphalerite is a broad band semiconductor. The top of the valence band of above three materials are dominantly occupied by Fe (3d),... 

The investigations on electrochemistry related to sulphide mineral flotation have been widely reported for a long time. However, pilot tests and industrial plant operations of potential control flotation (PCF) of sulphide ores have made little progress due to the absence of an apphcable control potential method. The addition of oxidants and reductants will result in a big consumption of the chemicals. In the meantime, adjusting the pulp potential by external field is also of low efficiency. 

Flotation of Naturally Hydrophobic Minerals. Flotation response of naturally hydrophobic minerals correlates very well with elec-trokinetic measurements. Figure 3 shows that the flotation of coal correlates well with zeta potential of demineralized coal (5.). The flotation rate is maximum where the zeta potential is zero and it decreases with increase in the magnitude of the zeta potential. Similar observations were made earlier by Chander and Fuerstenau (6 ) for the flotation of molybdenite. The decrease in flotation rate with increase in zeta potential is because of the electrical double layer repulsion between the charged particle and the air bubble. 

For example, in mineral flotation, surfactant can be added to adsorb on metal ore particles, increasing the contact angle, so they attach to gas bubbles, but the surfactant does not adsorb much on silicates, so these do not attach to gas bubbles. The surfactant may also stabilize a foam containing the desired particles facilitating their recovery as a particle-rich froth that can be skimmed. Flotation processes thus involve careful modification of surface tension and wettability. 

There are many other applications of zeta potential, some of which are discussed in later sections, including mineral flotation (Section 10.3.1), bitumen flotation (Section 11.3.2), paper-making (Section 12.2), and many others. 

The role of turbulence in assisting with suspension stability is described in Section 10.3.1. For example, a rule of thumb for the role of turbulence in maintaining sufficient suspension stability for mineral flotation is the one-second criterion which states that the particles in a suspension are sufficiently well dispersed for flo-... 

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