Iron ores, flotation separation

Various starches have been used in industry for depressing talc, mica, natural sulfur, carbon gangue and sulfide minerals, and especially for depressing oxidized iron minerals in the reverse flotation of iron ore and the separation of Cu-Mo in the copper-molybdenite sulfide flotation. 

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. 

Tests have been done further on the separation of a Cu-Pb mixed concentration of ethyl xanthate flotation of copper-lead-iron sulphide ore by E- control modifying with H2O2. Test results are presented in Table 10.3. It indicates the possibility of selective flotation separations of copper-lead flotation concentration by control. The feed of copper-lead mixed concentrated assayed Cu 6.53% and Pb 62.38%. Using hydrogen peroxide as a potential modifier, a copper concentration with 24.19% Cu and recovery with 89% can be obtained after separation. 

In contrast to conventional flotation, in which the desirable mineral is directly floated and collected from the produced froth, reverse (indirect) flotation aims to have the undesirable minerals preferentially floated and removed, leaving behind a slurry that has been concentrated in the desirable mineral. This method has been used for the purification of iron ore and the separation of salt from potash. The next section describes some other variations on conventional froth flotation. 

Bastnasite is mined from hard rock deposits. Production in China is a by-product of iron ore mining while U.S, production is solely for rare-earths. Ore is recovered by drilling and blasting. The ore Is crushed, ground and subjected to flotation. The bastnasite fraction is floated off and thereby seperated from other minerals to produce a concentrate. Bastnasite can be converted directly, without separating individual rare-earths, to other derivatives such as sulphate or chloride by dissolution in acid. The following step to crack the concentrate for further processing used in the U.S. is to roast in air and then to leach with HCl. This produces an insoluble cerium rich... 

Promoters or collectors provide the substances to be separated with a water-repellent air-avid coating that will adhere to air bubbles. Typical collectors for flotation of metallic sulfides and native metals are dithiophosphates and xanthates. Fatty acids and their soaps, petroleum sulfonates, and sulfonated fatty acids are widely used as collectors in flotation of fluorspar, iron ore, phosphate rock, and others. Fuel oil and kerosene are used as collectors for coal, graphite, sulfur, and molybdenite. Cationic collectors such as fatty amines and amine salts are widely used for separation of quartz, potash, and silicate minerals. 

The flotation processes using oil-water interface for collection of particles are emulsion flotation at, 1 liquid-liquid flotation. In the former the rengentized particles are collected by oil-water emulsion droplets and by aemu on of the system, whereas in the latter removal of the particles collected at the interfoce is achieved mostly by phase separation, The only commercial use of emulsion flotation, to onr knowledge, is that of the separation of aputite from iron ore at LKAB, Malmberget, Sweden,... 

Application of express-flotation is promising for recovery of small particles (Petrovitz, 1981). The process consists of the following operations. Pulp is saturated with microbubbles 100 pm in diameter in a mechanical flotation machine at intensive agitation of a small amount of air (80 to 100 per m pulp). Saturated pulp is released to a thickener where separation into foam and chamber product takes place. Saturation time is 5 min, flotation time is 1 min. Extraction of finely pulverized iron ore of Olenegorskii deposites makes up 98%. In usual flotation such recovery is attained in 10 min. 

Flotation has been used for more than 100 years to separate sulphides, oxides and other salts from ores, as well as to obtain phosphates, barite, chromite and other materials. Up to 90% of copper, lead, nickel, zinc are extracted using flotation in the USA [152 - 153]. In Russia, flotation is widely used to additionally obtain apatite, barite and phosphates. Flotation of iron oxides is not used in practise yet, but the number of experiments carried out in this direction is rather large. The main physicochemical principles of flotation have been discussed above [59 -74]. Here, only some practical problems will be discussed. In [153], requirements are pointed out which apply to three-phase flotation foams, and the main components of the process are defined, i.e. surfactant - collector surfactant - frother activator, depressants, colligend, gangue. The peculiarities of flotation and foam separation in batch and continuous modes are outlined as well as the structure and properties of the main types of flotation agents described. As surfaces of the majority of mineral particles are hydrophilic in nature, hydrophobisation of particles is necessary for a selective separation. 

A technology with enormous potential in the mineral processing area is selective flocculation accompanied by flotation. Such a process already has become coimnercial for the separation of iron minerals from low-giade iron ore. In this case starch is used as flocculant for iron oxide and quartz is floated using amiiK... 

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