Flotation Techniques

In froth flotation, first a pulp of crushed and ground particles in water is conditioned with desired flotation reagents including pH modifiers and surfactants. Then it is agitated in a cell, as shown schematically in 

TABLE 16.1-1 Flotation Techniques Classified on the Basb of Mechanism of e aration and Size of Material Separated 

Natural surface activity In association with surface-active agents Foam fractionation for example, detergents from aqueous solutions Ion flotation, molecular flotation, adsorbing colloid flotation for example, Sr , Pb , Hg , cyanides Foam flotation for example, microorganisms, proteins Microflotation, colloid flotation, ultraflotation for example, particulates in wastewater, clay, microorganisms Froth flotation of nonpolar minerals for example, sulfiir Froth flotation for example minerals such as silica Precipitate flotation (1st and 2nd kind) for example, ferric hydroxide 

Source Reprinted from Separation and Purification Methods, Courtesy of Marcel Dekker, Inc. 

Two cells used in the laboratory for studying the physical chemistry of flotation process are the Hal-limond cell and Fuerstenau cell. Tests can be conducted in these cells under controlled chemical conditions. Tests in a Hallimond tube cell, shown schematically in Fig. 16.2-2, require only about I g of the mineral and do not require the use of a frother. Rigorous control of flotation time, gas flow, and citation that have been made possible by recent modiflcations enable one to conduct tests with a reproducibility of 1%. Also, application of the results obtained using the Hallimond tube cell has been demonstrated recently by correlating such results with those obtained using conventional laboratoiy large-scale cells.  

Foses fractionation involves the removal of naturally surface-active species by aeration at low flow rates in the absence of any agitation. This technique is particularly useful for the removal of highly surface-active contaminants from surfacmme nsed for hesic surfaces and colloid chemistry resenrch work, 

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Nonferrous Metal Production. Nonferrous metal production, which includes the leaching of copper and uranium ores with sulfuric acid, accounts for about 6% of U.S. sulfur consumption and probably about the same in other developed countries. In the case of copper, sulfuric acid is used for the extraction of the metal from deposits, mine dumps, and wastes, in which the copper contents are too low to justify concentration by conventional flotation techniques or the recovery of copper from ores containing copper carbonate and siUcate minerals that caimot be readily treated by flotation (qv) processes. The sulfuric acid required for copper leaching is usually the by-product acid produced by copper smelters (see Metallurgy, extractive Minerals RECOVERY AND PROCESSING). 

The isolation of zinc, over 90% of which is from sulfide ores, depends on conventional physical concentration of the ore by sedimentation or flotation techniques. This is followed by roasting to produce the oxides the SO2 which is generated is used to produce sulfuric acid. The ZnO is then either treated electrolytically or smelted with coke. In the former case the zinc is leached from the crude ZnO with dil H2SO4, at which point cadmium is precipitated by the addition of zinc dust. The ZnS04 solution is then electrolysed and the metal deposited — in a state of 99.95% purity — on to aluminium cathodes. 

In spite of the lack of basic research on flotation of gold-bearing ores, the flotation technique is used not only for upgrading of low-grade gold ore for further treatment, but... 

Flotation of arsenical gold ores associated with base metals is accomplished using a sequential flotation technique, with flotation of base metals followed by flotation of gold-containing pyrite/arsenopyrite. The pyrite/arsenopyrite is floated at a weakly acid pH with a xanthate collector. 

Selection of a flotation technique for gold preconcentration depends very much on the ore mineralogy, gangue composition and gold particle size. There is no universal method for flotation of the gold-bearing minerals, and the process is tailored to the ore characteristics. A specific reagent scheme and flowsheet are required for each ore. 

Many operating plants treating PGM ores use conventional flotation techniques and the metallurgical results are below optimum in a number of these plants. 

Two bituminous coals of moderate ash content were chosen for this paper to illustrate this method of determining coal-mineral association. The first sample was an Upper Freeport coal with 1.3% moisture, 9.88% ash, and 1.56% total sulfur. The second sample was an Indiana No. 3 coal having 10.5% moisture, 7.35% ash, and 4.26% total sulfur. Both coals had been precleaned at a coarse particle size, ground to minus 325 mesh (44 ym), and then separate samples were cleaned by float-sink and by froth flotation techniques, as described elsewhere [5]. Analyses of the feed coals are included in Table I. 

S. Pongstabodee, N. Kunachitpimol, and S. Damronglerd, Combination of three-stage sink-float method and selective flotation technique for separation of mixed post-consumer plastic waste, Waste Manage. (Oxford), 28(3) 475—483,2008. 

Magnetic and flotation techniques can reduce the Ti02 content of Georgia kaolinites from 1.7—2.0% to 0.2—0.4%. Leaching experiments by Dolcater et al. (1970) indicate that on an average 15% (range 0—30%) of the Ti in seven samples (six from Georgia) was in the kaolinite structure. Thus, present data indicate that some Ti does occur in the kaolinite layer, presumably in the octahedral sheet. 

To determine the density of a small irregular-shaped object by flotation technique. 

Density of a Small Irregular-Shaped Object by Flotation Technique... 

In this example, the development of a new flotation technique for waste water treatment is discussed. Dimensional analysis has been used since the onset of this work. It concerns the so-called Induced Air Flotation, IAF, which is an alternative to the well-known Dissolved Air Flotation, DAF, the latter being already discussed in Example 7. 

Khelifa, A., Moulay, S. and Naceur, A.W. (2005) Treatment of metal finishing effluents by the electro flotation technique. Desalination 181,27-33. 

The influence of small amounts of PVC degrading in PET scrap during reprocessing has been studied (371). An aqueous column flotation technique, utilising pH level and surfactants, has been proposed (311). A continuous thermal separation system, for removal of trace PVC, has also been described (204). Triboelectrostatic separation, based on cyclones, fluidised beds or rotating tubes, has also separated five commonly used plastics, including PVC (30). 

This method has been employed to measure the critical wetting surface tensions of particles of sulfur, silver iodide, methylated glass beads, quartz, paraffin-wax-coated coal, and surfactant-coated pyrite. Generally. Fuerstenau and coworkers [106-115] found that the film flotation technique is sensitive to the surface hydrophobicity and the heterogeneity of the particles. It was found that particle size, particle shape, particle density, film flotation time, and the nature of the wetting liquids have negligible effects on the results of film flotation. But the liquid and the solid particles used in the experiments must not have any chemical interactions. 

Fig. 5.4 Qarification of a Muscat must using the flotation technique (laboratory experiments). Influence of different fining agents (each value is the average of two experiments). Upper values (%) residual NTU compared to the control must lower values (% in italics) residual NTU compared to the flotated must...

Fig. 5.6a-c Clarification of a Muscat must using the flotation technique. Comparison between industrial trials and laboratory experiments (three measurements), during and 14 h after flotation (average of three sampling). For industrial trials, measurements are the average of six measures made during the process (15 min between each sampling)... 

Marchal, R., Lallement, A., Jeandet, R, Establet, G. (2003). Qarification of Muscat musts using wheat proteins and the flotation technique. J. Agric. Food Chem., 51, 2040-2048. 

The conventional method of ore concentration after mining involves (a) crushing and grinding to size, which is determined by the degree of liberation of the minerals from the bulk of the ore and (b) beneficiation of the ore, either by physical means or by flotation technique, whenever applicable to produce a concentrate acceptable to the smelter. In a typical copper operation, the mill feed averages 0.70% copper and the flotation concentrate is anywhere from 25 to 30% copper. 

The objective of the work is to present an experiment-founded adsorption model for precipitate flotation. Batch precipitate flotation of CufOH) with dodecylbenzene sulphonate (DBS) as collector, was carried out both with dissolved (DAF) and dispersed (DIS) air. The processes were considered as a succession of the dynamic equilibria taking place at the gasliquid and solidliquid interfaces. Both flotation processes were expressed quantitatively in terms of surface concentrations of Cu(OH)2 and DBS per unit surface area of the air buble, as well as the ratio of the numbers of air bubbles and solid particles (B /P ). Also the maximal concentrations of both DBS and Cu(OH)2, recoverable under the given conditions were calculated. All these values were determined by following the Cu(OH)2 and DBS recovery. The 2 flotation techniques were compared in regard to their efficiency and mechanism. Finally, the results obtained were discussed in terms of the other models for the colloid particle adsorption at the air-water interface. 

Concentration generally carried out using flotation techniques... 

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