Samarium separation

Yttrium-group earths, containing samarium, separation from mona-zite by magnesium nitrate, 2 56 separation by fractional crystallization of bromates, 2 56, 62 separation from cerium earths by double-sulfate method, 2 44, 46... 

In his opinion, a new previously unknown element contained in didymium was responsible for the appearance of the new lines in the spectrum. He named it decipium from the Latin to deceive, to stupefy and the name proved to be ironical decipium turned out to be a mixture of several REEs both known and unknown ones. Decipium was debunked in 1879 by L. de Boisbaudran of France who played a prominent role in the discovery of new REEs. In the next chapter we shall tell you how he discovered gallium predicted by Mendeleev. Boisbaudran extracted didymium from samarskite and thoroughly studied the sample by spectroscopy. Boisbaudran was a much more skillful experimenter than Delafontaine and he succeeded in separating the impurity from didymium . He named the new element samarium after samarskite, being unaware that samarium was also a mixture of elements. Boisbaudran s discovery was immediately confirmed by Marignac who, after multiple recrystallizations of samarium , separated two fractions which he marked Y and Yp (not to be confused with the symbol of yttrium Y ). The spectrum of the second fraction was identical to the spectrum of samarium . As to the first fraction, we shall have a look at it a little later. 

Europe) In 1890 Boisbaudran obtained basic fractions from samarium-gadolinium concentrates which had spark spectral lines not accounted for by samarium or gadolinium. These lines subsequently have been shown to belong to europium. The discovery of europium is generally credited to Demarcay, who separated the rare earth in reasonably pure form in 1901. The pure metal was not isolated until recent years. 

Although rare-earth ions are mosdy trivalent, lanthanides can exist in the divalent or tetravalent state when the electronic configuration is close to the stable empty, half-fUed, or completely fiUed sheUs. Thus samarium, europium, thuUum, and ytterbium can exist as divalent cations in certain environments. On the other hand, tetravalent cerium, praseodymium, and terbium are found, even as oxides where trivalent and tetravalent states often coexist. The stabili2ation of the different valence states for particular rare earths is sometimes used for separation from the other trivalent lanthanides. The chemicals properties of the di- and tetravalent ions are significantly different. 

The reduction diffusion process has also been used for the production of powders of the magnetic neodymium-iron-boron alloy (Nd15Fe77B8). The reaction involves use of a powder mix of neodymium oxide, iron, ferroboron and calcium. The reaction is conducted by heating the powder charge mixture at 1200 °C for 4 h under vacuum. Neodymium-iron-boron alloys are much more prone to oxidation than samarium-cobalt alloys and a proprietary leaching procedure is used for the separation of the alloy and calcium oxide. 

Europium - the atomic number is 63 and the chemical symbol is Eu. The name derives from the continent of Europe . It was separated from the mineral samaria in magnesium-samarium nitrate by the French chemist Eugene-Anatole Demar9ay in 1896. It was also first isolated by Demar ay in 1901. 

Promethium (gjPm) was predicted to fill a space between the rare-earths neodymium (gjjNd) and samarium (gjSm) in the periodic table in 1902. Although a few scientists claimed to have produced it, separating promethium from other rare-earths proved to be difficult, and thus identifying it was elusive. Only small amounts are produced and exist. 

Using a spectrometer in 1853, Jean Charles-GaUisard de Marignac (1817—1894) suspected that dydimia was a mixture of yet-to-be-discovered elements. However, it was not until 1879 that Paul-Emile Locoq de Boisbaudran (1838—1912), using a difficult chemical fractionation process, discovered samarium in a sample of samarskite, calling it samarium after the mineral, which was named for a Russian mine official. Colonel von Samarski. Samarskite ore is found where didymia is found. Didymia ( twins ) was the original name given to a combination of the two rare-earths (praseodymium and neodymium) before they were separated and identified. 

In 1896 Eugene-Anatole Demarcay (1852-1904), a French chemist, was working with a sample of samarium when he realized that it was contaminated by an unknown element. He was able to separate the two (samarium and europium) in 1901 by a long and tedious process. He is given credit for the discovery of europium and was the one to give the new element its... 

Other chemists also worked to separate gadolinium from the mineral dydimia. Paul-Emile Locoq de Boisbaudran, following clues provided by Marignac, isolated element 62 (samarium)... 

Mosander extracted from the mineral lanthana a rare earth fraction, named didymia in 1841. In 1879, Boisbaudran separated a rare earth oxide called samaria (samarium oxide) from the didymia fraction obtained from the mineral samarskite. Soon after that in 1885, Baron Auer von Welsbach isolated two other rare earths from didymia. He named them as praseodymia (green twin) and neodymia (new twin) after their source didymia (twin). The name praseodymium finally was assigned to this new element, derived from the two Greek words, prasios meaning green and didymos meaning twin. 

The discovery of samarium is credited to Boisbaudran, who in 1879 separated its oxide, samaria from Mosander s didymia, the mixture of rare earth oxides from which cerium and lanthanum were isolated earher. Demarcay in 1901 first identified samaria to be a mixture of samarium and europium oxides. The element got its name from its mineral, samarskite. The mineral, in turn, was named in honor of the Russian mine official Col. Samarki. 

Samarium ore usually is digested with concentrated sulfuric or hydrochloric acid. The extraction process is similar to other lanthanide elements. Recovery of the metal generally consists of three basic steps. These are (1) opening the ore, (2) separation of rare earths first to various fractions and finally to their individual compounds, usually oxides or halides, and (3) reduc-... 

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. 

Trivalent samarium activated minerals usually display an intense luminescence spectrum with a distinct hne structure in the red-orange part of the spectrum. The radiating term 65/2 is separated from the nearest lower level 11/2 by an energy interval of 7,500 cm This distance is too large compared to the energy of phonons capable to accomplish an effective non-radiative relaxation of excited levels and these processes do not significantly affect the nature of their spectra in minerals. Thus all detected lines of the Sm " luminescence take place from one excited level and usually are characterized by a long decay time. 

By increasing the temperature of an ion exchange system, more rapid separation can be performed. In fact, temperature modifies the separation factor of two neighbor elements. For example, by increasing the temperature from 25°C to 95°C, the 1.5 samarium-europium separation factor becomes 1.8 and the europium-gadolinium 1.1 separation factor goes to 1.5. Thus the difficult Eu-Gd separation at 25°C becomes "easy" at 95°C. 

French chemist who discovered gallium, samarium, and dysprosium, and perfected methods of separating the rare earths He ranks with Bunsen, Kirch-hofiF, and Crookes as one of the founders of the science of spectroscopy. 

The 147Sm-143Nd system was first used in cosmochemistry by Lugmair et al. (1975a), who published a precise isochron age for an Apollo 17 basalt (Fig. 8.11). The system developed rapidly thereafter. Note that the spread in 147Sm/144Nd in the mineral phases of this basalt is less than 50%, not factors of ten, several hundred, or even a few thousand, as can be seen in other systems. The fact that precise isochron ages can still be obtained is a testament to the care taken in chemical separation of samarium and neodymium and the precision of modem mass spectrometric analysis. 

Several samarium and neodymium isotopes are isobars (Table 4.2) and cannot be separated by mass spectrometry. Thus, samarium and neodymium must be completely separated by chemical procedures prior to measuring them in a mass spectrometer. The ion-exchange chemistry necessary to separate these elements is now well developed (see Appendix). Isotope measurements can be done either by TIMS or ICPMS (inductively... 

As with the Sm- Nd and Re- Os systems, careful chemistry is required to cleanly separate the parent and daughter elements because mass spectrometry cannot resolve 176Lu from 176Hf. The ion-exchange chemistry is similar to that for samarium-neodymium. In fact, fractions of samarium, neodymium, lutetium and hafnium are often produced in a single procedure. Mass spectrometry is done by ICPMS because this is the only method that effectively ionizes hafnium. 

It has been found that from a homogeneous solution the oxalate of samarium is preferentially precipitated over oxalates of other rare earths and yttrium falls behind all of them. Thus, in a separation process Sm is concentrated to a greater extent at the head section and Y at the tail section [45]. 

---