Floatability

The vessel design features a Chinese hat-like conical core stopper above the underflow sump, which is there to prevent the vortex from reaching the latter and reentraining the settled soHds. The core stopper is also beheved to stabilize and locate the vortex flow in the vessel. Overflow from the vessel is through a wide cylindrical insert through the Hd, similar to a vortex finder in a hydrocyclone (16), and an optional provision can be made for collecting any floatables in a float trap. 

Similarly, small (0.2—0.6 mm) air bubbles are introduced into a 2.6-m Deister Flotaire column at an intermediate level allowing rapid flotation of readily floatable material in the upper recovery zone. The bottom air permits longer retention time of the harder-to-float particles in the presence of micrometer-sized bubbles at a reduced downward velocity. The first commercial unit went on stream in 1986. It was used to improve the recovery of <0.6 mm (—28 mesh) coal in the plant s tailings. An average of 5.5% increase in coal recovery resulted from its use (14). The second commercial use processed <0.15 mm (—100 mesh) coal feed. 

Surfaces that do not have strong surface chemical bonds that were broken tend to be nonpolar and are not readily wetted. Substances such as graphite and talc are examples that can be broken along weakly bonded layer planes without rupturing strong chemical bonds. These solids are naturally floatable. Also, polymeric particles possess... 

Grit Chambers Industries with sand or hard, inert particles in their wastewaters have found aerated grit chambers useful for the rapid separation of these inert particles. Aerated grit chambers are relatively small, with total volume based on 3-min retention at maximum flow. Diffused air is normally used to create the mixing pattern shown in Fig. 25-44, with the heavy, inert particles removed by centrifugal action and friction against the tank walls. The air flow rate is adjusted for the specific particles to be removed. Floatable solids are removed in the aerated grit chamber. It is important to provide for... 

Further considerations include skimmers and weir overflow rates. Skimmers should be provided on all units since even secondary effluents contain some floatable solids and grease. Overflow rates and sludge scraper design should conform to the requirements of other clarification units. 

Flossofen, m. flowing furnace. Flotationschemie, /, flotation chemistry, flotationsfahig, a. floatable, Flotationsverfahren, n. flotation process. Flotator, m. flotation machine, flotierbar, a. floatable, flotieren, v.t. float. 

Dispersing a number of water-floatable particles on an oil film, the particles of a material that, under illumination and in the presence of air, accelerates the oxidation of organic compounds in the oil film... 

The particles consist of a bead with an exterior surface that is at least partially coated with a material capable of accelerating the oxidation of organic compounds floating on water, under illumination, and in the presence of air. The coated bead is water-floatable and has a diameter of less than 2 mm. The bead consists of a plastic material coated with an intermediate layer of a material that will not accelerate the oxidation of the plastic material by air or by itself, oxidized under illumination and in the presence of air by the outer coating material. 

Activators are those reagents which act in a manner converse to the action of depressants, i.e., they render those minerals floatable which either have been temporarily depressed or would not float without their assistance. They are generally soluble salts which ionize in the aqueous medium. The ions then react with the mineral surface, providing a monomolecular coating and thereby making the mineral surface favourably disposed to the collectors. Sphalerite (ZnS) is essentially not floatable with common collectors. The addition of Cu2+ to the solution, however, alters the mineral surface to CuS, which can adsorb collector. This feature is described elaborately in a later section. 

Machado, L.C.R., Lima, F.W.J., Paniago, R., Ardisson, J.D., Sapag, K. and Lago, R.M. (2006) Polymer coated vermiculite-iron composites novel floatable magnetic adsorbents for water spilled contaminants. Applied Clay Science,... 

Depressants are used to make materials less floatable, and again have been used for some time.4,18 A recent example is the use of phosphoric acid to depress the flotation of a sedimentary phosphate ore, enhancing the selectivity of recovery of calcite and silica.24 Natural and synthetic polymers have also been used as depressants.20... 

Literature on flotation of gold, PGMs, rare earths and various oxides is rather limited, compared to literature on treatment of sulphide-bearing ores. As mentioned earlier, the main problem arises from the presence of gangue minerals in the ore, which have flotation properties similar to those of valuable minerals. These minerals have a greater floatability than that of pyrochlore or columbite. In the beneficiation of oxide minerals, finding a selectivity solution is a major task. 

Flotation Properties of Gold Minerals and Factors Affecting Floatability... 

FLOTATION PROPERTIES OF GOLD MINERALS AND FACTORS AFFECTING FLOATABILITY... 

Native gold and its alloys, which are free from surface contaminants, are readily floatable with xanthate collectors. Very often however, gold surfaces are contaminated or covered with varieties of impurities [4], The impurities present on gold surfaces may be argentite, iron oxides, galena, arsenopyrite or copper oxides. The thickness of the layer may be of the order of 1-5 pm. Because of this, the flotation properties of native gold and its alloys vary widely. Gold covered with iron oxides or oxide copper is very difficult to float and requires special treatment to remove the contaminants. 

Tellurides, on the other hand, are readily floatable in the presence of small quantities of collector, and it is believed that tellurides are naturally hydrophobic. Tellurides from Minnesota (USA) were floated using dithiophosphate collectors, with over 9% gold recovery. 

In flotation of gold-containing base metal ores, a number of modifiers normally used for selective flotation of copper lead, lead zinc and copper lead zinc have a negative effect on the floatability of gold. Such modifiers include ZnS04-7H20, S02, Na2S205 and cyanide when added in excessive amounts. 

The adsorption of collector on gold and its floatability is considerably improved by the presence of oxygen. Figure 17.1 shows the relationship between collector adsorption, oxygen concentration in the pulp and conditioning time [4], The type of modifier and the pH are also important parameters in flotation of gold. 

The floatability of gold from gold-containing copper gold ores depends on the nature and occurrence of gold in these ores, and its association with iron sulphides. 

Some porphyry copper ores contain naturally floatable gangue minerals, such as chlorites and aluminosilicates, as well as preactivated quartz. Sodium silicate, carboxy methyl-cellulose and dextrins are common depressants used to control gangue flotation. 

The Busheld Complex consists of varieties of ore types, including high-chromium ores, ore with floatable gangue minerals and small but significant quantities of ultrafine slimes that are important from a processing point of view. 

Pyrrhotite is a relatively slow floating mineral, especially monoclinic pyrrhotite, which is usually present in these ore types. The floatability of pyrrhotite also decreases when using certain hydrophobic mineral depressants, such as guars and dextrins. The flotation of pyrrhotite may improve with small additions of copper sulphate (CuS04). 

Violarite is the least floatable mineral of all the sulphides and represents a major loss of PGM in the flotation tailing from a number of operations. 

Ore Sulphide-dominated PGM ore composed of Cu, Ni, pyrrhotite and some pyrite. This ore contains a fair amount of floatable gangue minerals... 

Ore Sulphide-dominated PGM ore containing nickel, pyrrhotite and a little copper. Floatable gangue was dominated by talc and chlorites... 

Amplats - Mine 3 South Africa, Morensky Reef Grind To a K%0 of 87 pm Reagents CUSO4 = 100-200 g/t, dibutyl xanthate = 320 g/t. Modified guar gum = 200-250 g/t Metallurgy 90-100 g/t total PGM in concentrate, PGM recovery = 80-82% Ore Sulphide-dominated PGM deposit containing Cu/Ni and mixed pyrite-pyrrhotite. The main floatable gangues are calcite, chlorites with lesser talc... 

Chemical composition and physical structure of the oxide copper minerals and the ionic composition of the slurry phase play important roles in the floatability of various oxide minerals. The oxide copper minerals are often porous, and in some cases, water soluble. Some of the oxide minerals tend to slime during grinding, and flotation of fine oxide minerals is rather difficult. 

The gangue constituents and their nature are sometimes determining factors in selection of a treatment process for beneficiation of oxide copper ores. Highly weathered ores usually contain a fairly large amount of slimes, which has a negative effect on the floatability of oxide copper minerals. Also, there is an appreciable difference in floatability between oxide minerals from carbonaceous and siliceous ores. 

Floatability of malachite is one of the most important oxide copper minerals for production of copper from oxide ores using flotation. Extensive research has been carried out by a number of researchers [4-7] in which various flotation methods were examined. 

Figure 19.3 illustrates the floatability of pure malachite with different amines. It should be pointed out that there are several varieties of malachite, Cu4(P04)2(0H)4-0H. Pseudomalachite is difficult to float, and it is well known that pseudo-malachite can be floated with anionic collectors, but responds poorly to the sulphidization method. 

Figure 19.3 Floatability of malachite with C-18 mono- and dialkylamines at pH 8.5-9.0.

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