Bastnasite cerium

Cerium is the 25th most abundant element on Earth. It is also the most abundant rare-earth metal in the lanthanide series. Its major ores are monazite and bastnasite. Cerium is found in the Earth s crust in 46 ppm, which is about 0.0046% of the Earth s crust. Cerium is mixed with other elements in its ores, making it difflcult to find, isolate, and identify. Its existence was unknown until about 1803... 

Cerium is the most abundant so-called rare-earths metal. It is found in a number of minerals including ahanite (also known as orthite), monazite, bastnasite, cerhe, and samarskite. Monazite and bastnasite are presently the two more important sources of cerium. 

Large deposits of monazite (found on the beaches of Travancore, India and in river sands in Brazil), ahanite (in the western United States), and bastnasite (in Southern California) will supply cerium, thorium, and the other rare-earth metals for many years to come. 

Whereas certain rocks of igneous origin formed by melting and recrystallization can include minerals enriched in the lanthanides (4), cerium is usually present as a trace element rather than as an essential component. Only a few minerals in which cerium is an essential stmcture-defining component occur in economically significant deposits. Two minerals supply the world s cerium, bastnasite [68909-13-7] LnFCO., and monazite [1306-41 -8] (Ln,Th)PO. ... 

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. 

Mischmetal. Mischmetal [62379-61-7] contains, in metallic form, the mixed light lanthanides in the same or slightly modified ratio as occurs in the resource minerals. It is produced by the electrolysis of fused mixed lanthanide chloride prepared from either bastnasite or mona2ite. Although the precise composition of the resulting metal depends on the composition of chloride used, the cerium content of most grades is always close to 50 wt %. 

An alternative commercial form of a metallic mixed lanthanide-containing material is rare-earth siUcide [68476-89-1/, produced in a submerged electric-arc furnace by the direct reduction of ore concentrate, bastnasite, iron ore, and quart2. The resulting alloy is approximately 1/3 mischmetal, 1/3 sihcon, and 1/3 iron. In addition there are some ferro-alloys, such as magnesium—ferrosilicons, derived from cerium concentrate, that contain a few percent of cerium. The consumption of metallic cerium is overwhelmingly in the mixed lanthanide form in ferrous metallurgy. 

The cerium concentrate derived from bastnasite is an excellent polish base, and the oxide derived direcdy from the natural ratio rare-earth chloride, as long as the cerium oxide content is near or above 50 wt %, provides an adequate glass poHsh. The polishing activity of the latter is better than the Ce02 Ln0 ratio suggests. Materials prepared prior to any Ln purification steps are sources for the lowest cost poHshes available used to treat TV face plates, mirrors, and the like. For precision optical polishing the higher purity materials are preferred. 

Cerium oxide acts as a catalytic oxidizer in a spinel-based additive (38) that aids SO2 to SO conversion and promotes the required sulfate formation. Bastnasite itself is the most economical source of cerium and can be used directly at 1% as the capture additive (39). 

Rare Earths are produced primarily from three ores, monazite, xenotime, and bastnasite. Monazite is a phosphate mineral of essentially the cerium subgroup metals and thorium -(light rare Earths, Th) P04. The composition of monazite is reasonably constant throughout the world, with almost 50% of its rare Earth content as cerium and most of the remaining 50% as the other members of the cerium subgroup. Xenotime, like monazite, is a rare Earth orthophosphate but contains up to 63% yttrium oxide and also a markedly higher propor-... 

The element was discovered by Klaproth in 1803 and also in the same year by Berzelius and Hisinger. It is named after the asteroid Ceres. Cerium is found in several minerals often associated with thorium and lanthanum. Some important minerals are monazite, aUanite, cerite, bastnasite, and samarskite. It is the most abundant element among aU rare-earth metals. Its abundance in the earth s crust is estimated to be 66 mg/kg, while its concentration in sea water is approximately 0.0012 microgram/L. 

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. 

Gadolinium is produced from both its ores, monazite and bastnasite. After the initial steps of crushing and beneficiation, rare earths in the form of oxides are attacked by sulfuric or hydrochloric acid. Insoluble rare earth oxides are converted into soluble sulfates or chlorides. When produced from monazite sand, the mixture of sand and sulfuric acid is initially heated at 150°C in cast iron vessels. Exothermic reaction sustains the temperature at about 200 to 250°C. The reaction mixture is cooled and treated with cold water to dissolve rare earth sulfates. The solution is then treated with sodium pyrophosphate to precipitate thorium. Cerium is removed next. Treatment with caustic soda solution fohowed by air drying converts the metal to cerium(lV) hydroxide. Treatment with hydrochloric or nitric acid sol-... 

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. 

The bastnasite ore is calcined after concentration by flotation, then a hydrochloric acid attack under certain operating conditions solubilize most of the trivalent rare earths. The residue, which is recovered by filtration contains the tetravalent component of bastnasite along with 65 to 80% cerium oxide. 

Mischmetal is produced commercially by electrolysis, The usual starting ingredient is the dehydrated rare earth chloride produced from monazite or bastnasite. The mixed rare earth chloride is fused in an iron, graphite, or ceramic crucible with the aid of electrolyte mixtures made up of potassium, barium, sodium, or calcium chlorides. Carbon anodes are immersed in the molten salt. As direct current flows through the cell, molten mischmetal huilcls up in the bottom of the crucible. This method is also used to prepare lanthanum and cerium metals. 

Bastnasite (Y,Ce)(C03)F A fluoro carbonate of cerium/yttrium—concentrates contain 60% REO raised to 70% REO by acid leaching and 85% by leaching and calcining Y2O3 low (0.1-0.3%)... 

Bastnasite LnFCOs Monazite (Ln, Th)P04 (richer in earlier lanthanides) Xenotime (Y, Ln)P04 (richer in later lanthanides). In addition to these, there are Chinese rare earth reserves which amount to over 70% of the known world total, mainly in the form of the ionic ores from southern provinces. These Chinese ion-absorption ores, weathered granites with lanthanides adsorbed onto the surface of aluminium silicates, are in some cases low in cerium and rich in the heavier lanthanides (Longnan) whilst the Xunwu deposits are rich in the lighter metals the small particle size makes them easy to mine. The Chinese ores have made them a leading player in lanthanide chemistry. 

After initial concentration by crushing, grinding and froth flotation, bastnasite is treated with 10% HCl to remove calcite, by which time the mixture contains around 70% lanthanide oxides. This is roasted to oxidize the cerium content to Ce on further extraction with HCl, the Ce remains as Ce02, whilst the lanthanides in the (-T3) state dissolve as a solution of the chlorides. 

In general, Y and the heavier lanthanides, Gd to Lu, are less abundant than the lighter lanthanides. La to Eu. However, there are two further complicating factors one is that the elements with even atomic number are more abundant than those of odd atomic number, reflecting the greater stability of such nuclei. Secondly, some ores (e.g. bastnasite, monazite) are richer in the lighter metals while others (e.g. xenotime) have more of the heavier metals. The abundance of yttrium in the Earth s crust is 31 ppm while the total abundance of the lanthanides is some 180 ppm cerium is the most abundant (66 ppm), while thulium and lutetium are the rarest (0.5 and 0.8 ppm, respectively). 

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... 

A fraction of Ce, La. Nd and Pr derived from bastnasite or monazite is a typical feedstock in the recovery process of cerium on a commercial scale. Separation of the rare-earth elements may be achieved by splitting the mixed rare-earth elements into a cerium/lanthanum and didymium (Nd/Pr) fraction first. The cerium/lanthanum fraction may be used as a further feedstock in a second extraction stage and will yield high pure cerium and lanthanum solution respectively. Cerium can then be precipitated as. for example, an oxalate or a carbonate which may be used as precursor for cerium derivatives. 

The most important ores of cerium are cerite, monazite, and bastnasite. It is thought to occur in Earth s crust with a concentration of 40 to 66 parts per million. This makes cerium about as abundant as copper or zinc. 

Zuo Y, Liu YH, Chen J et al (2009) Extraction and recovery of cerium(iv) along with fluorine(i) from bastnasite leaching liquor by DEHEHP in [Cginim]PF. J Chem Technol Biotechnol 84 949-956... 

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. 

Cerium is the most abundant member of the lanthanide, or rare earth, elements. It has two stable valence states, Ce (cerous) and Ce " (ceric). It is found as a trace element in several minerals, but only two, bastnasite, LnFCOs, and monazite, (Ln, Th)P04 (where Ln = a lanthanide element, such as lanthanum, praseodymium, neodymium, or cerium), which are approximately 30 percent and 22 to 25 percent cerium, respectively, are the principal sources of this element. 

To obtain cerium, a bastnasite concentrate is treated with sulfuric acid or hydrochloric acid, yielding the hydrated sulfate or the chloride of cerium. The sulfate is converted to the hydroxide or the carbonate, and then to the fluoride. A monozite concentrate is digested in an autoclave with an excess of caustic soda at 150°C (302°F). 

Lanthanum — (Gr. lanthanein, to lie hidden), La at. wt. 138.90547(7) at. no. 57 m.p. 920°C b.p. 3464°C sp. gr. 6.145 (25°C) valence 3. Mosander in 1839 extracted a new earth lanthana, from impure cerium nitrate, and recognized the new element. Lanthanum is found in rare-earth minerals such as cerite, monazite, allanite, and hastnasite. Monazite and bastnasite are principal ores in which lanthanum occurs... 

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