Bastnasite production

Bastnasite (CeFCOs) - a fluorocarbonate of cerium containing 60-70% rare earth oxides (REO), including lanthanum and neodymium - is the world s major source of rare earths. Host rocks include carbonatite, dolomite breccia with syenite intrusives, pegmatite, and amphibole skam. Since 1985, the bastnasite production in China has increased very fast and has dominated the market from the 1990s to the present. 

Bastnasite has been identified in various locations on several continents. The largest recognized deposit occurs mixed with monazite and iron ores in a complex mineralization at Baiyunebo in Inner MongoHa, China. The mineral is obtained as a by-product of the iron ore mining. The other commercially viable bastnasite source is the Mountain Pass, California deposit where the average Ln oxide content of the ore is ca 9%. This U.S. deposit is the only resource in the world that is minded solely for its content of cerium and other lanthanides. 

An alternative process for opening bastnasite is used ia Chiaa high temperature roastiag with sulfuric acid followed by an aqueous leach produces a solution containing the Ln elements. Ln is then precipitated by addition of sodium chloride as a mixed sulfate. Controlled precipitation of hydroxide can remove impurities and the Ln content is eventually taken up ia HCl. The initial cerium-containing product, oace the heavy metals Sm and beyond have been removed, is a light lanthanide (La, Ce, Pr, and Nd) rare-earth chloride. 

The ores from which rare-earth elements are extracted are monazite, bastnasite, and oxides of yttrium and related fluorocarbonate minerals. These ores are found in South Africa, Australia, South America, India, and in the United States in Cahfomia, Florida, and the Carolinas. Several of the rare-earth elements are also produced as fission by-products during the decay of the radioactive elements uranium and plutonium. The elements of the lanthanide series that have an even atomic number are much more abundant than are those of the series that have an odd atomic number. 

It is found in ores such as monazite, gadohnite, and bastnasite. It was first separated into three elements in 1843 (yttria, erbia, and terbia). Erbium is also produced as a by-product of nuclear fission of uranium. 

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. 

Several other processes also are apphed for the commercial production of europium. In general, all processes are based upon the initial steps involving opening the mineral (bastnasite or monazite) with sulfuric acid or sodium hydroxide, often followed by roasting and solubihzation. In one such process after separation of cerium, the soluble rare earth chloride mixture in HCl solution is pH adjusted and treated with bis(2-ethylhexyl)phosphate to obtain europium sesquioxide, EuaOs. 

Holmium is obtained from monazite, bastnasite and other rare-earth minerals as a by-product during recovery of dysprosium, thulium and other rare-earth metals. The recovery steps in production of all lanthanide elements are very similar. These involve breaking up ores by treatment with hot concentrated sulfuric acid or by caustic fusion separation of rare-earths by ion-exchange processes conversion to halide salts and reduction of the hahde(s) to metal (See Dysprosium, Gadolinium and Erbium). 

Third example - Although ceric oxide really represents the active element in polishing media, most of the polishing plants are satisfied with about 50 % pure ceric oxide, which is available in the natural mixture of the light rare eai h elements as they are extracted either from bastnasite or monazite, in order to keep the cost of the product low. 

These materials are available through production of bastnasite at the Mountain Pass Mine in California, of monazite from Australia, India and Brazil, and of monazite as a by-product from the production of tin ores, rutile and various heavy mineral sands. 

From this early availability and use of mischmetal grew a demand for bastnasite ore. In these alloys, about one-half of the present rare earths are cerium. In the mid-to-late sixties, a more economical source of cerium was introduced which was, in essence, a concentrate from which the lanthanum had been removed. This material allowed for the production of alloys whose rare earth concentration was about 90% cerium. These rare earthbearing materials have the approximate analyses shown in Table I and are now used commercially, with the high cerium source predominating in the United States. 

Even today, however, the alloy is favored over mischmetal for multiple ladle practices and for a combined deoxidation-desulfur-ization-sulfide shape control effect using large ladle additions in the production of critical line pipe qualities. This latter application is threatened by substitution with calcium injection as we will see later. Because it was based on bastnasite, an exclusively American ore at the time, and because of its metallurgical limitations, RES never took hold extensively in Europe and in Japan, The recent emergence of a very large Chinese bastnasite deposit may prompt renewed interest in some sort of direct reduced REM alloy during the eighties. 

The Mountain Pass, California deposit now supplies nearly 100% of the world s bastnasite. Palabora deposits are mainly used for copper production but have given some rare earths concentrates in the past. The rare earths distribution in bastnasite, a fluoro-carbonate, is given in Table III. 

Of these, bastnasite is the only mineral worked primarily for rare earths and both monazite and xenotime are mostly by-products of mining ilmenite, rutile, cassiterite, zircon or gold. Apatite and some multi oxide minerals like pyrochlore, euxenite, brannerite and loparite (a niobium titanate) are also commercial sources of rare earths, but production of RE from these is limited. 

Fig. 1.5. Production of rare earths chloride from bastnasite [2],...

HDEP has been found useful for the commercial production of Eu from bastnasite and for the purification of yttrium. 

Bastnasite and monazite are the main sources for the production of rare earth metals and their compounds A flow sheet illustrating the sources, processes, the products that can be obtained and their uses or applications is given in Fig. 1.17. 

Rare-earth minerals occur in a variety of geologic environments. Concentrations exist in igenous, sedimentary and metamorphic rocks. The rare-earths are constituents in over 160 of minerals [3], but only a few are recovered for commercial production. Bastnasite, Monazite, Loparite, Xenotime and Rare-earth bearing Clay are the major sources of the world s rare-earth supply. Bastnasite, Monazite and Lopariie are considered to be the principle cerium ores (Table 1.1). 

Bastnasite is mined from hard rock deposits. Production in China is a by-product of iron ore mining while U.S, production is solely for rare-earths. Ore is recovered by drilling and blasting. The ore Is crushed, ground and subjected to flotation. The bastnasite fraction is floated off and thereby seperated from other minerals to produce a concentrate. Bastnasite can be converted directly, without separating individual rare-earths, to other derivatives such as sulphate or chloride by dissolution in acid. The following step to crack the concentrate for further processing used in the U.S. is to roast in air and then to leach with HCl. This produces an insoluble cerium rich... 

Yttrium By-product from bastnasite REE production Phosphorus... 

Source Monazite, bastnasite, and related fluocarbo-nate minerals as well as minerals of the yttrium group. These ores contain varying percentages of rare-earth oxides, which are often loosely called rare earths. Rare earth elements also occur as fission products of uranium and plutonium. 

Monazite concentrate is processed either with sulfuric acid, like bastnasite, to produce a mixture of sulfates but the usual process is an alkaline treatment. The alkali process is preferred since it removes the phosphates more readily [9]. Whichever method is chosen the radioactive thorium must be completely removed. After benefication the monazite concentrate is finely ground and reacted with a hot concentrated sodium hydroxide at 140° to 150°C. Insoluble hydroxides of the rare-earths and thorium are formed while trisodium phosphate and excess sodium hydroxide remain in solution. The next step is hydrochloric acid attack on the solids portion. The thorium remains insoluble and a crude thorium hydroxide can be filtered off Trace contaminants that do carry through into solution, such as uranium and lead, as well as some thorium, are removed by coprecipitation with barium sulphate in a deactivation step. The cerium-containing product will be a rare-earth chloride differing only marginally in the proportions of the various rare- earths present, to the analogous rare-earth chloride produced from bastnasite. 

Lanthanides are constituents of many different minerals in igneous rocks, shale, and silicates however, the two major sources for commercial production are bastnasite (a flu-orocarbonate) and monazite (a phosphate)... 

The world s resources of rare earth metals lie mainly in deposits of bastnasite in China. The chart below shows that mine production of the ore from China dominates the world s output. Bastnasite is a mixed metal carbonate fluoride, (M,M. ..)C03F. The composition varies with the source of the mineral, but the dominant component is cerium ( 50%), followed by lanthanum (20-30%), neodymium (12-20%) and praseod5mium (w5%). Each of the other rare earth metals (except for promethium which does not occur naturally) typically occurs to an extent of < 1 %. Monazite,... 

Relatively inexpensive samarium depends upon the mischmetal production and the production of other separated light lanthanides from the monazite and bastnasite ores for other products. In the preparation of mischmetal samarium is naturally concentrated in the slag because it is only reduced to the divalent state during electrolysis while the other rare earths are reduced to metal at the cathode. The samarium is cheaply recovered from the slag. In the early 1980 s when mischmetal production peaked, the total amount of samarium available from both the mischmetal production and as a by-product for other separated rare earths was about 400 tons per year. The production of samarium could be increased but it would be much more expensive since it would have to be separated from the ores for itself and bear the burden of the separation costs since the other lanthanides would be surplus materials. 

Production The most important base minerals are xenotime, monazite, and bastnasite. The first two are orthophosphate minerals LaP04 and the third is a fluoride carbonate LaCOsF. Lanthanoids with even atomic numbers are more common. Monazite also contains thorium and yttrium which makes handling difficult since thorium and its decomposition products are radioactive. 

Molycorp, a wholly owned subsidiary of Unocal Corp., was the only company to mine rare earth minerals in the United States in 2002. The rare-earth separation plant operations stopped in 2003. Molycorp mined bastnasite, a rare earth fluorocarbonate mineral, as a primary product at Mountain Pass, California. The value of domestic ore production was estimated at 31 million in 2002 the estimated value of refined rare earth minerals was more than 1 billion. The end uses for rare earth products in 2000 were as follows automotive catalytic, 22 percent glass polishing and ceramics, 39 percent permanent magnets, 16 percent petroleum refining catalysts, 12 percent metallurgical additives and alloys, 9 percent rare earth phosphors for lighting, televisions, computer monitors, radar, and x-ray intensifying film, 1 percent, and miscellaneous,... 

An oxide of a rare earth element, it occurs in monazite and bastnasite. It is marketed as the oxide or as other salts, such as oxalate, carbonate or chloride salts. Technical grade products contain more or less amounts of praseodymium and some lanthanum and other rare earths. 

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