Bastnaesite

Bastnaesite, containing neither U nor Th, has replaced monazite as the primary LREE-ore mineral. Related minerals may arise from substitution of the fluorine and carbonate ions. Bastnaesite is a widespread mineral, although it never occurs in 

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A limited number of rare-earth minerals are mined for large-scale rare-earth production mona2ite, bastnaesite, loparite [12173-83-OJ, xenotime [13817-22-6]. In addition, siace the 1980s rare-earth-containing clays called ionic ore are mined ia China. Table 4 shows the rare-earth composition of typical mineral concentrates. 

Rare earth Bastnaesite Loparite Mona2ite Xenotime... 

Commercial mining of rare-earth reserves began ia the late 1800s. Mona2ite was the principal rare-earth source up until 1965. Thereafter bastnaesite production exceeded mona2ite production and as of 1992 bastnaesite, which is the world s principal source of rare earths, constituted 65% of world output of rare-earth minerals (see Table 5). In addition to the conventional ores, there are several other rare-earth resources having a low level of iadustrial production. 

Selective Oxidation. Cerium, the most abundant lanthanide, can be separated easily after oxidation of Ce(III) to Ce(IV), simplifying the subsequent separation of the less abundant lanthanides. Oxidation occurs when bastnaesite is heated in air at 650°C or when the hydroxides are dried in air... 

A U.S. Bureau of Mines survey covering 202 froth flotation plants in the United States showed that 198 million tons of material were treated by flotation in 1960 to recover 20 million tons of concentrates which contained approximately 1 billion in recoverable products. Most of the worlds copper, lead, zinc, molybdenum, and nickel are produced from ores that are concentrated first by flotation. In addition, flotation is commonly used for the recoveiy of fine coal and for the concentration of a wide range of mineral commodities including fluorspar, barite, glass sand, iron oxide, pyrite, manganese ore, clay, feldspar, mica, sponumene, bastnaesite, calcite, garnet, kyanite, and talc. 

Scandium is very widely but thinly distributed and its only rich mineral is the rare thortveitite, Sc2Si20v (p. 348), found in Norway, but since scandium has only small-scale commercial use, and can be obtained as a byproduct in the extraction of other materials, this is not a critical problem. Yttrium and lanthanum are invariably associated with lanthanide elements, the former (Y) with the heavier or Yttrium group lanthanides in minerals such as xenotime, M "P04 and gadolinite, M M SijOio (M = Fe, Be), and the latter (La) with the lighter or cerium group lanthanides in minerals such as monazite, M P04 and bastnaesite, M C03F. This association of similar metals is a reflection of their ionic radii. While La is similar in size to the early lanthanides which immediately follow it in the periodic table, Y , because of the steady fall in ionic radius along the lanthanide series (p. 1234), is more akin to the later lanthanides. 

There are over 100 minerals known to contain lanthanides but the only two of commercial importance are monazite, a mixed La, Th, Ln phosphate, and bastnaesite, an La, Ln fluorocarbonate (M C03F). Monazite is widely but sparsely distributed in many rocks but, because of its high density and inertness, it is concentrated by weathering into sands on beaches and river beds, often in the presence of other... 

The bulk of both monazite and bastnaesite is made up of Ce, La, Nd and Pr (in that order) but, whereas monazite typically contains around 5-10% Th02 and 3% yttrium earths, these and the heavy lanthanides are virtually absent in bastnaesite. Although thorium is only weakly radioactive it is contaminated with daughter elements such as Ra which are more active and therefore require careful handling during the processing of monazite. This is a complication not encountered in the processing of bastnaesite. 

Rare earth (RE) is a generic name for 14 metallic elements of the lanthanide series. These elements have similar chemical propenies and are usually supplied as a mixture of oxides extracted from ores such as bastnaesite or monazite. 

Reprinted from the U. S. Bur. Mines Rept. Invest., No. 5378 (Dec. 1957), by F. W. Lytle, J. I. Botsford, and H. A. Heller, entitled X-ray Emission Spectro-graphic Analysis of Bastnaesite Rare Earths. ... 

The cerium group of REOEs, in which loparit, bastnaesite, parisit, monazite, eshipit and ortit are included. 

Most of the products that come from REOEs are monacite, bastnaesite and euxenite. 

Bastnaesite belongs to the carbonatite group of minerals that contain REOEs. Beside the cerium group of elements, bastnaesite also contains yttrium and europium. Typically, it contains 65-75% REOE. Bastnaesite is usually found in pegmatites, carbonatite and hydrothermal ore bodies in alkaline gangue minerals. Because it is poor chemically and stable, it is not found in mineral sand deposits. 

Monazite, bastnaesite and loparite contain exclusively cerium group of REOEs. 

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]. 

Flotation properties of bastnaesite depend largely on the gangue composition of the ore and the impurities present in the mineral itself. Bastnaesite found in a carbonatite ore is recovered using fatty acid collector after heat pretreatment of the flotation feed. The effect of heat temperature on bastnaesite grade-recovery is illustrated in Figure 24.3. 

Floatability of bastnaesite found in barite-fluorite ores is extremely poor using either fatty acid flotation or sodium oleate. Research work conducted on an ore from Central Asia showed that the floatability of bastnaesite improved significantly after barite preflotation [5]. The flotation of bastnaesite from a carbonatite ore improved with the use of oleic acid modified with phosphate ester. The flotation of bastnaesite from deposits ofpegmatitic origin can be successfully accomplished with several types of collectors, including tall oil modified with secondary amine, and tall oil modified with petroleum sulphonate-encompassing group. 

The effect of the tall oil modification on bastnaesite metallurgical results is presented in Table 24.2. Data shown in this table indicates that the use of a modified tall oil resulted in significant improvement in the metallurgical results of bastnaesite. 

Figure 24.3 Effect of heat temperature on bastnaesite grade-recovery relationship.

Effect of tall oil modifications on bastnaesite flotation from pegmatitic ores... 

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. 

Flotation practice in the beneficiation of bastnaesite-containing ores... 

Liberation of the Mountain Pass ore has been extensively studied on the mill feed ore and on the plant product. Grinding the ore to a K 0 of about 56 pm is required to achieve liberation. Locking between the bastnaesite and calcite above 50 pm is common. Usually calcite/bastnaesite middlings reports to the final concentrate. 

Flotation temperature was the subject of numerous studies. It was concluded that heating the pulp with collector is the only way to selectively float bastnaesite. Heating the pulp with collector is believed to result in selective aggregation of bastnaesite in the form of repellent droplets, which may result in improved selectivity and in a reduction in slime interference. 

Beneficiation of barite, fluorite and bastnaesite from the Dong Pao deposit in Vietnam... 

This ore is heavily weathered ore, with more than 30% of the bastnaesite contained in the -7 (iim fraction. The major host minerals present in this ore are barite and fluorite. Table 24.6 shows the chemical analyses of the ore used in various research studies. 

Because this ore was high in barite and fluorite, direct flotation of bastnaesite from the ore was not possible. It should be pointed out that fluorite has similar flotation properties as bastnaesite and depression of fluorite during bastnaesite flotation is difficult. 

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. 

The ore was washed and deslimed before grinding. The fines from the washing contained over 30% of the total bastnaesite present in the ore. 

The ground ore was first subjected to barite flotation followed by fluorite flotation. By floating the barite and fluorite ahead of the bastnaesite, about 70% of the total weight was removed from bastnaesite flotation feed. The bastnaesite flotation feed was upgraded from 8.5% REO to about 30% REO. 

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 flotation of barite, sodium silicate was used as a depressant and barium chlorite as a barite activator. Barite collector SR82 was composed of petroleum sulphonate, sodium alkyl sulphate and succinamate mixture. The collector was selective towards both fluorite and bastnaesite. Over 96% of the barite was recovered in a relatively high-grade concentrate. 

During fluorite flotation, Quebracho and lignin sulphonate mixture (MESB) was used with collector composed of a mixture of oleic acid and phosphoric ester. Collectors used for bastnaesite flotation included tall oil fatty acid modified with three ethylene tetra... 

The results obtained from the continuous locked-cycle tests are summarized in Table 24.8. The major contaminant of the bastnaesite concentrate was fluorite. Complete fluorite flotation was not possible without heavy losses of bastnaesite in the fluorite concentrate. 

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