Flotation of pyrochlore

The treatment process and flotation properties of pyrochlore are very much dependent on the gangue composition of the ore. The selective flotation of pyrochlore from carbonatite ore is not possible since calcite and dolomite have similar flotation properties as pyrochlore. In addition, in the presence of carbonates, the stable pH required for flotation of pyrochlore (i.e. 5.0-5.5) cannot be maintained. 

In the case of carbonatite ores, a beneficiation process involves preflotation followed by reactivation and flotation of pyrochlore. In the case of pegmatitic ores that contain silicates, biotite, albite and limonite, as the gangue minerals, direct flotation of pyrochlore can be achieved with a variety of different collectors. 

The successful flotation of pyrochlore from carbonatite ores depends on a number of factors ... 

Flotation of pyrochlore using sodium alkyl sulphate is dependent on flotation pH. At a pH above 5.5, no pyrochlore flotation is achieved. At this pH, microcline, limonite and aegirine were floated. It appears that the use of alkyl sulphate at slightly acidic to alkaline pH number of gangue minerals can be selectively floated from pyrochlore. At a pH between 1.5 and 3.0, alkyl sulphate floats pyrochlore and zircon, whereas floatability of limonite, microline and aegirine is greatly reduced (Figure 22.4). 

Using cationic flotation (C-14 amine and amine hydrochloride) method, no selectivity between pyrochlore and gangue minerals is achieved. Amine flotation, therefore, cannot be successfully applied for flotation of pyrochlore. 

The results obtained indicated that cationic flotation of pyrochlore was not successful. Dispersant AQ4 has a pronounced effect on niobium metallurgical results. Dispersant/ depressant AQ4 is composed of the following individual reagents 60% orthodihydrox-ybenzene (Catacol), 30% low-molecular-weight acrylic acid (Accumer 2400) and 10% hexametapho sphate. 

Meanwhile, the hydroximic acid with C7-C9 (HM-50) shows good flotation performance when it is used in the flotation of pyrochlore, loparite, perovskite, cassiterite, yttrotantalite, and various rare earth minerals. 

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. 

Figure 22.2 Effect of type of acid used in the pretreatment of pyrochlore flotation feed on the grade-recovery relationship.

The use of quinolines [7] were examined with the addition of fuel oil as co-collector. According to the data provided (Table 22.5), quinolines are effective pyrochlore flotation collectors. The number of carbons in the quinoline structure determines the grade and recovery of pyrochlore. 

The results showed that amines normally used for pyrochlore flotation did not work for flotation of Ta/Nb. Therefore, collector selection is very dependent on the type of niobium minerals present in the ore. 

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. 

From disseminated ores contained in mineral lenses, the recovery of bastnaesite and monazite is accomplished using flotation. The flotation properties of bastnaesite and monazite are similar to the gangue minerals contained in the bastnaesite and monazite, such as calcite, barite, apatite, tourmaline, pyrochlore and others, which represent difficulties in selective flotation. However, in recent years, significant progress has been made in the flotation of both monazite and bastnaesite [2,3]. 

Monazite is readily floatable using cationic collectors such as oleic acid and sodium oleate in the pH region of 7-11. Monazite does not float readily using, for example, laurel amine or anionic collectors. Adsorption of the sodium oleate on the monazite increases with an increase in pH, indicating that monazite does not float in acid pH, while pyrochlore is readily floatable and is depressed at a pH greater than 10. Figure 24.1 shows the effect of pH on flotation of monazite, pyrochlore and zircon. 

Figure 24.1 Effect of pH on flotation of monazite, zircon and pyrochlore.

In addition, starch performs different depressant performances in the flotation of various rare metal minerals. The flotation results of various rare metal minerals using starch as depressant are shown in Fig. 4.6. As shown in Fig. 4.6, pyrochlore, pyroxene, fluorite, and dolomite can be depressed by starch although the reagent dosage is low. Fluorite can be depressed by starch in both acid and base conditions. However, dolomite cannot be depressed in acid condition. 

Sodium silicate has a strong depressing effect on pyrochlore, and it is sometimes used during calcite flotation. Sodium silicate hydrosol is prepared by reacting ferric chloride and silicate, followed by acidification of the mixture, which has a positive effect on selectivity. The addition of small quantities of hydrosol (100 g/t) resulted in significant improvement in concentrate grade. 

Extensive studies have been carried out using orthodihydroxybenzene, known as catechol (commercial name). This reagent has improved the rate of fine pyrochlore flotation and also has a beneficial effect on selectivity. Research work with this reagent was conducted on carbonatite ore from Canada. 

Effect of different amines on pyrochlore flotation from St. Honore Niobec ore... 

The apatite barite bulk flotation was accomplished with a mixture of tall oil fatty acid and sulphonate (Aero 827) at an alkaline pH. Sodium silicate and caustic tapioca starch were used for pyrochlore depression during the bulk apatite barite flotation stage. 

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