Monazite samarium

Samarium is the 39th most abundant element in the Earths crust and the fifth in abundance (6.5 ppm) of all the rare-earths. In 1879 samarium was first identified in the mineral samarskite [(Y, Ce U, Fe) (Nb, Ta, Ti )Ojg]. Today, it is mostly produced by the ion-exchange process from monazite sand. Monazite sand contains almost all the rare-earths, 2.8% of which is samarium. It is also found in the minerals gadolmite, cerite, and samarskite in South Africa, South America, Australia, and the southeastern United States. It can be recovered as a byproduct of the fission process in nuclear reactors. 

Boisbaudran obtained this rare earth element in 1892 in basic fractions from samarium-gadolinium concentrates, but it was not identified for several years. Demarcay obtained the element in the pure form in 1901. The element was named after Europe. It is found in nature mixed with other rare earth elements. Its concentration, however, is much lower than most other lanthanide elements. The principal rare earth ores are xenotime, monazite, and bastna-site. 

Samarium occurs in nature widely distributed but in trace quantities, always associated with other rare earth metals. The two most important minerals are (i) monazite, which is an orthophosphate of thorium and the rare earths and (ii) bastanasite, which is a rare earth fluocarbonate. The samarium content of these ores is about 2%, as oxide. It also is found in precambri-an granite rocks, shales, and certain minerals, such as xenotime and basalt. Its abundance in the earth s crust is estimated to be 7.05 mg/kg. 

The monazite sand is heated with sulfuric acid at about 120 to 170°C. An exothermic reaction ensues raising the temperature to above 200°C. Samarium and other rare earths are converted to their water-soluble sulfates. The residue is extracted with water and the solution is treated with sodium pyrophosphate to precipitate thorium. After removing thorium, the solution is treated with sodium sulfate to precipitate rare earths as their double sulfates, that is, rare earth sulfates-sodium sulfate. The double sulfates are heated with sodium hydroxide to convert them into rare earth hydroxides. The hydroxides are treated with hydrochloric or nitric acid to solubihze all rare earths except cerium. The insoluble cerium(IV) hydroxide is filtered. Lanthanum and other rare earths are then separated by fractional crystallization after converting them to double salts with ammonium or magnesium nitrate. The samarium—europium fraction is converted to acetates and reduced with sodium amalgam to low valence states. The reduced metals are extracted with dilute acid. As mentioned above, this fractional crystallization process is very tedious, time-consuming, and currently rare earths are separated by relatively easier methods based on ion exchange and solvent extraction. 

Neodymium, determination of atomic weight of, in neodymium oxalate, 2 61 separation of, from samarium from monazite, as magnesium nitrate double salt, 2 56, 57... 

As with other rare earth elements, the primary sources of samarium are the mineral monazite and bastnasite. It is also found in samarskite, cerite, orthite, ytterbite, and fluorspar. 

The commercially important samarium-containing minerals are treated with concentrated sulfuric acid or, in the case of monazite, with a solution of sodium hydroxide (73%) at approximately 40°C (104°E) and under pressure. The element is separated from the solutions via solvent extraction or ion exchange. Sm salts are weakly yellow and may exhibit ion emission. Sm ions show luminescence and are sometimes used to generate lasers. Samarium is used in the manufacture of headphones and tape drivers, see ALSO Cerium Dysprosium Erbium Europium Gadolinium Holmium Lanthanum Lutetium Neodymium Praseodymium Promethium Terbium Ytterbium. 

The method evolved by Moseley (1887 to 1915) of determining the atomic number enabled chemists to ascertain, as has already been seen, the maximum number of elements that can exist in serial order between any two selected ones. As the atomic numbers of lanthanum and lutecium are 57 and 71, it is clear that it is possible for 13 elements to exist of atomic numbers between these. Now europium was the twelfth to be discovered, but no element corresponding to 61 had been recorded. This should lie between neodymium (60) and samarium (62), and as early as 1902 Bohuslav Brauner had predicted its existence. In 1926 Hopkins, of Illinois, with his collaborators Harris and Yntema, announced the discovery of a new element in the neodymium extracted from monazite sand, the lines of the X-ray spectrum agreeing with those expected for element 61. He called it Illinium. 

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. 

Most important mineral Samarium belongs to the light REM group, the cerium group. Minerals typical forthis group are monazite (Ce,La,Nd,Th)(PO, SiO ), Figure M25, and bastnaesite (Ce,La)C03(F,0H), Figure M22. 

At Baiyunebo in Inner Mongoha, 135 km from Baotou, RE minerals are found together with minerals of iron, titanium and niobium. The deposit is worked for iron, which keeps the costs low for production of the RE metals. Both monazite and bastnaesite are mined and, because of that, the mine is very important as a source of the cerium group metals. The bastnaesite has a higher content of samarium and europium than the CaHfornian ore in Mountain Pass. As the monazite is low in thorium and free from uranium its radioactivity is low, which is a benefit for ore handhng. 

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