Monazite flotation

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. 

Experimental work conducted at different levels of sodium silicate (Table 24.9) indicates that sodium silicate is an excellent depressant for titanium, zircon and other gangue minerals while the monazite flotation is not affected. 

The acintols (mixture of oleic and linoleic acids) were found to give better results compared to sodium oleate. This can be attributed to the presence of linoleic acid, which has two double bonds. Furthermore, the rate of monazite flotation increased with the acintol than with the sodium oleate. 

Effect of sodium silicate on monazite flotation from Kerala and Chennai beach sand (India)... 

Effect of different collectors on monazite flotation from the Chennai beach sand... 

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. 

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.

A large portion of the REOs are produced from monazite- and bastnaesite-containing ores. In the majority of cases, bastnaesite and monazite ores are relatively complex and contain gangue minerals (calcite, barite, fluorite and apatite) with similar flotation properties as the monazite and bastnaesite. 

A large portion of monazite production comes from mineral sand deposits. In the beneficiation of monazite from mineral sand deposits that contain garnet, ilmenite, shell and silicates, the physical concentration and combination of physical preconcentration-flotation is used. Several reagent schemes using flotation were developed throughout various studies [8-10] and some have been confirmed in continuous pilot plants. 

In conclusion, it can be noted that the effect of pH on flotation of beach sand minerals is critical in selective flotation of monazite from other minerals. 

Reagent additions (kg/t) Flotation Monazite concentrate PH Monazite tailings ... 

Testwork using monazite depression with lactic acid and flotation of the residual minerals with 3-lauril amine hydrochloride achieved a concentrate grading 75.5% monazite at a recovery of about 70%. 

Effect of different collectors on flotation of monazite using sodium oleate as the activator... 

Farah, M.Y., and Fayed, L.A., Oxalate Activation in the Flotation of Monazite by Heavy Sulphonate Collector, Egypt Journal of Chemistry, Vol. 1, p. 2363, 1958. 

Europeum generally is produced from two common rare earth minerals monazite, a rare earth-thorium orthophosphate, and bastnasite, a rare earth fluocarbonate. The ores are crushed and subjected to flotation. They are opened by sulfuric acid. Reaction with concentrated sulfuric acid at a temperature between 130 to 170°C converts thorium and the rare earths to their hydrous sulfates. The reaction is exothermic which raises the temperature to 250°C. The product sulfates are treated with cold water which dissolves the thorium and rare earth sulfates. The solution is then treated with sodium sulfate which precipitates rare earth elements by forming rare earth-sodium double salts. The precipitate is heated with sodium hydroxide to obtain rare earth hydrated oxides. Upon heating and drying, cerium hydrated oxide oxidizes to tetravalent ceric(lV) hydroxide. When the hydrated oxides are treated with hydrochloric acid or nitric acid, aU but Ce4+ salt dissolves in the acid. The insoluble Ce4+ salt is removed. 

The Travancore monazite is first reduced to convert leucoxene (ilmenite) into magnetite, thus changing the magnetic behaviour of the ilmenite [139]. The conductivity of monazite is not affected by the reduction process. Flotation processes have also been adopted to dress the Travancore monazite. 

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