Quartz flotation

In the case of quartz flotation using primary amines and quaternary ammonium salts, as collectors, Somasundaran [24] found that the concentration (log C) of collectors at the critical flotation condition is linearly related to n values as shown in Fig. 5.7. In addition, the concentration (log C) at which the zeta-potential of quartz in alkylamine solutions is equal to zero was found to have similar linear relationship with n values (Fig. 5.8). 

Fig. 5.7. Critical concentration of amines in quartz flotation (by P. Somasundaran, D.W. Fuerstenau).

Organic depressants for Fe " -activated wolframite and quartz Depression of wolframite-quartz flotation with various flotation agents is shown in Figs. 5.16a and 5.16b. Experimental results for the concentration of the reagents for good depression of the above two minerals are listed in Table 5.22. The structural characteristics of the depressant molecules can be summarized as follows ... 

TABLE 14,3-2 Calculated and Experimental Values for the Relative Effectiveness of Sodium Ions and Barium Ions in Depressing Quartz Flotation at Natural pH Using 10 J kmoLW per Dodecy(ammonium Acetate... 

Quartz can be floated by cationic surfactant dodecyla-mine hydrochloride. Nonionic polymer, polyacrylamide (PAM), which does not adsorb on quartz and does not cause flotation by itself, increases the quartz flotation by amine slightly due to the uptake of water molecules by the polymer for hydration. The hydration of polymer causes an increase in the effective concentration of amine. 

Collector pH range of 100 % flotation Optimum pH of eassiterite Limit of inevitable metal ions Flotation results of quartz (%) Flotation results of tourmaline (%)... 

The examples in the preceding section, of the flotation of lead and copper ores by xanthates, was one in which chemical forces predominated in the adsorption of the collector. Flotation processes have been applied to a number of other minerals that are either ionic in type, such as potassium chloride, or are insoluble oxides such as quartz and iron oxide, or ink pigments [needed to be removed in waste paper processing [92]]. In the case of quartz, surfactants such as alkyl amines are used, and the situation is complicated by micelle formation (see next section), which can also occur in the adsorbed layer [93, 94]. 

The addition of 2,2, 4,4, 6-pentanitro-6 -methyldiphenylamine [64653-47-0] to seawater precipitates potassium (38). Aromatic amines, especially aminotetrahydronaphthalenes and their A[-aryl derivatives, are efficient flotation agents for quartz. The use of DPA for image formation in films has been patented (39,40). Diarylamines are used as intermediates (41) for azo, sulfur, oxidative base, triaryhnethane, oxazine, nitro, and safranine dyes (see Dyes and DYE INTERLffiDIATES). 

The electrostatic separation method is the exclusive choice in some specific situations, for example in the cases of rutile and ilmenite deposits. These deposits generally contain minerals of similar specific gravities and similar surface properties so that processes such as flotation are unsuitable for concentration. The major application of electrostatic separation is in the processing of beach sands and alluvial deposits containing titanium minerals. Almost all the beach sand plants in the world use electrostatic separation to separate rutile and ilmenite from zircon and monazite. In this context the flowsheet given later (see Figure 2.35 A) may be referred to. Electrostatic separation is also used with regard to a number of other minerals. Some reported commercial separations include those of cassiterite from scheelite, wolframite from quartz, cassiterite from columbite, feldspar from quartz and mica, and diamond from heavy associated minerals. Electrostatic separation is also used in industrial waste recovery. 

Copper concentration Copper ore, water, chemical reagents, thickeners Flotation wastewaters Tailings containing waste minerals such as limestone, and quartz... 

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 ore used in this example contained a mixture of pyrochlore and columbite as the major niobium minerals. The tantalum is mainly associated with columbite. The major gangue minerals present in this ore were soda and potassium feldspars with small amounts of mica and quartz. Beneficiation of this ore using cationic flotation, normally employed for flotation of niobium, was not applicable for this particular ore, since most of the mica and feldspar floated with the niobium and tantalum. The effect of amine on Ta/Nb flotation is illustrated in Figure 23.9. The selectivity between Ta/Nb and gangue minerals using a cationic collector was very poor. 

India has very large deposits of monazite on the coastal shores of Kerala and Chennai. A typical mineral composition of this type of deposit is 60% ilmenite, 1.2% rutile, 5% zircon, 6.4% garnet, 4% silinanite, 16% quartz, 2.5-5% monazite and 1-7% shell. Research work involved different anionic collectors and pH during monazite flotation, along with the level of sodium silicate used as depressant. 

Table 10.2 Separation results of collectorless flotation of a mixture of chalcopyrite, galena and quartz (Feng et al., 1991)...

The common gangue material quartz (silica) is naturally hydrophilic and can be easily separated in this way from hydrophobic materials such as talc, molybdenite, metal sulphides and some types of coal. Minerals which are hydrophilic can usually be made hydrophobic by adding surfactant (referred to as an activator ) to the solution which selectively adsorbs on the required grains. For example, cationic surfactants (e.g. CTAB) will adsorb onto most negatively charged surfaces whereas anionic surfactants (e.g. SDS) will not. Optimum flotation conditions are usually obtained by experiment using a model test cell called a Hallimond tube . In addition to activator compounds, frothers which are also surfactants are added to stabilize the foam produced at the top of the flotation chamber. Mixtures of non-ionic and ionic surfactant molecules make the best frothers. As examples of the remarkable efficiency of the process, only 45 g of collector and 35 g of frother are required to float 1 ton of quartz and only 30 g of collector will separate 3 tons of sulphide ore. 

Figure i). Flotation recovery R (in %) of quartz as dependent on the concentration (in raol/L) of cetyl-pyridlnlum chloride. 

The oxide, a-quartz, was selected as the substrate for the present and continuing studies of metal ion adsorption. It is of considerable importance in several practical situations—e.g., water purification and ore flotation—and has the important property that it is negatively charged over a wide pH range since its zero-point-of-charge (z.p.c.) is circa pH 2. 

The inadvertent activation of a mineral can often result in an undesirable response to flotation. A typical example is quartz, a highly unreactive mineral whose recovery by flotation is therefore difficult. However, in the presence of metal cations, it can be activated to respond to anionic collectors, as shown by the data13 in Figure 3. It is of interest that the pH value at which flotation is effective can be related to that at which the monohydroxy complexes of the metal ions are predominantly stable, suggesting a specific adsorption of these species onto the quartz surface. In some cases this can be used for the selective depression of the quartz minerals in, for example, the flotation of pyrite in the presence of cationic collectors such as the long-chain amines. 

Figure3 Minimum flotation edges of quartz as a function of pH 1 x 10 4 M sulfonate, 1 x 10 4 M metal ion (after Fuerstenau and Palmer, ref. 13)...

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