Sequential 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. 

Bulk flotation followed by sequential flotation of gold-bearing sulphides, and depression of stibnite. This method was practiced at the Bradly concentrator (USA)... 

Metallurgical results obtained using a sequential flotation method... 

Recent studies conducted on ore from Kazakhstan have shown that sequential flotation using thionocarbamate collector gave better metallurgical results than those obtained with xanthate. 

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. 

The reagent scheme developed during extensive laboratory testing is presented in Table 24.7. This reagent scheme is unique in such a way that the collector and number of depressants involved are composed of a number of chemicals that provide improved selectivity during sequential flotation of barite and fluorite from bastnaesite. 

For the convenience of the reader, we have outlined the method of sequential flotation employed in our laboratory for separating chylomicrons VLDL, LDL, HDLa, HDLs, VHDL, and d> 1.25 bottom (Table 1). This method, the result of years of experience, has been highly reproducible in terms of the normal human population examined in this laboratory. Such a method may not necessarily apply to dyslipoproteinemic states, where modifications may be necessary, depending on the type of abnormality under consideration. It should also be stressed that any lipoprotein isolated is in need of purification this may be achieved by ultracentrifugation based on the assumption that contaminants are in loose association with the main complex. Whenever this purification is not achieved, other methods may be used as outlined below. For a discussion of the application of density gradient ultracentrifugation to the study of plasma lipoproteins, the reader is referred to a recent review (L3). 

Method of Separating Chylomicrons and the Various Lipoprotein Classes BY Sequential Flotation in the Ultracentripuge (All Run at 15°C)... 

The most widely applied activation procedure is that involving the use of copper(II) ions to enhance the floatability of some sulfide minerals, notably the common zinc sulfide mineral sphalerite.2 Sphalerite does not react readily with the common thiol collectors, but after being treated with small amounts of copper it floats readily owing to the formation of a surface layer of CuS." A similar procedure is often adopted in the flotation of pyrrhotite (FeS), pyrite (FeS2), galena (PbS) and stibnite (Sb2S3). In the context of coordination chemistry, the major contribution has been to the understanding of the chemistry involved in the deactivation of these minerals, a procedure often adopted in the sequential flotation of several minerals from a complex ore. 

Lipoproteins have densities that are lower than the densities of plasma proteins, which do not contain lipids. This characteristic is used to purify and fractionate lipoproteins by sequential flotation centrifugation to... 

These collectors are effective only under oxidizing conditions, and it is generally accepted that the species that confers hydrophobicity on the mineral surface is either a chemisorbed metal thio compound or the oxidized form of the collector, dithiolate. The amounts of each species formed will depend on the relative stabilities of the metal—sulfur and sulfur—sulfur bonds. The formation of four-membered chelate rings is also possible with soft metal ions such as copper(I) because the largely covalent character of the bond in this instance is able to overcome the strain within the ring by extensive electron delocalization. This could account for the >artial selectivity of some of these reagents for the copper minerals, which has been put to good use in the sequential flotation of copjrer, lead and zinc from complex sulfide ores. ... 

Standard centrifugation procedures used for fractionation of lipoproteins in human blood plasma are made by sequential flotation using KBr, NaBr, NaCl, or a combination of these salts to produce a solution with determined density, in which a selected lipoprotein fraction moves upward. 

The type of collector and flowsheet configuration play an important role in gold recovery from these ores. With a flowsheet that uses bulk Cu-Pb flotation followed by Cu-Pb separation, the gold recovery is higher than that achieved with a sequential Cu-Pb flotation flowsheet. In laboratory tests, and Aerophine collector type, in combination with xanthate, had a positive effect on gold recovery as compared to either dithiophosphate or thionocarbamate collectors. Table 17.10 compares the metallurgical results obtained with an Aerophine collector to those obtained with a dithiophosphate collector. 

The flowsheet that was developed for beneficiation of the Dong Pao ore involves sequential barite-fluorite-bastnaesite flotation. The flowsheet is presented in Figure 24.8. 

Results obtained using sequential rutile, ilmenite, and zircon flotation from bulk concentrate... 

The ink particles are then removed by either washing or flotation. The simplest form is wash deinking which consists of sequentially dewatering several times. The washing process will normally improve the brightness of the stock if the print particles which are present are in the size range 1-10 /an in diameter. 

This multi-step, one-pot process was taken further by integration of a third supported reagent for the sequential preparation of 3,5-diphenylpyrazole (Scheme 2.17). Following the previously established procedure, acetophenone was deprotonated and acylated to afford the 1,3-dicarbonyl species. This intermediate was easily separated from the spent polymers by filtration and passed without isolation into a suspension of the resin bound hydrazine salt (9), affording the desired pyrazole in 91% yield. In a subsequent publication, the authors reported that the depleted polymeric reagents from the first step of the conversion (i.e. (7) and (8)) were recovered and separated via a selective flotation procedure, enabhng them to... 

In a two-part series. Zeme discusses the importance of good separator hydraulics. A poor hydraulic design can make a good separation scheme ineffective. Zemel provides the methods and procedures to run a tracer test to identify short-circuiting, stagnant-flow regions, and shear forces. Analysis of the residence-time distribution curve that results is presented. Actual tests run on separators indicate that the most successful separator was the sequential dispersed-gas flotation cell, which closely followed the tanks-in-serie< model. This is contrasted with the poor performance of a conventional 2, 006-hbl [3 0-ms] wash tank The tracer responses of a pressurized flotation cell, a 15j000-bbl [2400 mJj wash tank, and a horizontal free-water knockout with and without baffles are also discussed. 

Among the separators tested, the most successful was a sequential dis-pereed-gas flotation cell. This cell followed very closely the tanks- n-se-nes" flow model described earlier as a mathematical model for normal flow. 

Sequential, dispened-gas flotation ceil. This flotation cell (Fig. 1) is representative of a number of such cells at many field locations. With minor variations, the design is identical. 

The recovery of valuable minerals and metals requires several stages of sequential processing operations. The mined ore must be crushed and ground to fine sizes prior to treatment by such bene-ficiation processes as heavy-medium separation, tabling, magnetic separation, electrostatic separation, flotation, selective flocculation, etc. Since most of these processes are carried out in aqueous media, solid-liquid separations by such operations as thickening and filtration are an integral part of the benefici-... 

Froth flotation has been used to separate many raw-mineral ores, such as those for copper, lead, zinc, and tungsten. If two valuable minerals are very difficult to separate from each other then a sequential set of flotation stages may be needed. An illustration is provided in Figure 10.8. First, enough grinding is applied to permit the two minerals to be liberated from the non-valuable gangue minerals. A first,... 

Condition the solids to alter the wettability of the mineral and the gangue. The fundamental surface wettability for sulfide ores is different from oxides, silicates, and salt-type minerals. pH is a critical variable. Typical conditioning chemical additions include collector about 0.01 to 0.1 kg/Mg solids frother about 0.01 to 0.5 kg/Mg solids activator about 1 to 4 kg/Mg solids depressant about 0.02 to 2 kg/Mg solids. Allow 6-min contact for conditioning. Bubble size about 1000 pm. Flotation rate constant is 0.2 to 1 min sink rate constant is 0.005 min-. Flotation cells mechanical cell for fast float, sequential separation, and relatively coarse particle diameter 1.6 to 2.4 kW/m cell volnme. Pneumatic cell for relatively dilute feed concentrations and smaller particle diameters. Air blower 0.5 kW/m cell volume. Typical solids throughput 0.4 to 0.8 kg/s m feed concentration 10 to 40% w/w. Air escape velocity 0.02 m/s. Float times 6 to 20 min. Feed concentration to rongher or scavenger 30% w/w to cleaner 10% w/w. 

The previous sections reviewed recent advancements in sequential electrostatic assembly to form NP-shelled structures. An alternate route to NP assembly arises from interfacial activity and stabilization of NPs. Colloidal particles with partial hydrophilic and hydrophobic character are known to behave like surface-active molecules (surfactants), particularly when adsorbed to a fluid-fluid interface. The assembly of small particles at interfaces is of relevance to advance fields that traditionally feature emulsions, foams, and flotation systems. It is also of pertinence to the development of new fields such as the synthesis of novel materials that include Janus particles, colloidosomes, porous solids, and anisotropic particles, all recently prepared by particle assembly at interfaces [36,38]. 

Lertrojanachusit N, Pornsunthomtawee O, Kitiyanan B, Chavadej J, Chavadej S (2013) Separation and purification of carbon nanotubes using froth flotation with three sequential pretreatment steps of catalyst oxidation, catalyst removal, and silica dissolution. Asia-Pac J Chem Eng 8... 

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