Gadolinite, extraction

Gadolinite, extraction of, 2 44 Gadolinium, separation of europium from samarium and, as magnesium nitrate double salt, 2 57 separation of samarium from, in acetate solution with sodium amalgam, 5 36... 

L. Rhenus, Rhine) Discovery of rhenium is generally attributed to Noddack, Tacke, and Berg, who announced in 1925 they had detected the element in platinum ore and columbite. They also found the element in gadolinite and molybdenite. By working up 660 kg of molybdenite in 1928 they were able to extract 1 g of rhenium. 

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. 

If the starting material is gadolinite, ore is digested with hydrochloric or nitric acid. Rare earths dissolve in acid. The solution is treated with sodium oxalate or oxalic acid to precipitate rare earths as oxalates. For euxenite, ore is opened either by fusion with potassium bisulfate or digestion with hydrofluoric acid. If monazite or xenotime is extracted, ore is either heated with sulfuric acid or digested with caustic soda solution at elevated temperatures. 

In 1880 the French chemist Jean-Charles-Galissard de Marignac (1817— 1894) studied samples of erbium metal that had been extracted from gadolinite. He discovered that the erbium metal contained minute amounts of a second metal. He named the metal (and the element) gadolinium, after the mineral. 

At this date, the principal ore minerals for the REEs are monazite, bastnaesite, and xenotime. The first REE mineral to be used was gadolinite, and from this mineral, several of the REE were first isolated, but it was not applied on an industrial scale. The first REE ore mineral from which REE were extracted for industrial use was monazite. 

Rhoiinm — (L. Rhenus, Rhine), Re at. wt. 186.207(1) at. no. 75 m.p. 3186°C b.p. 5596°C sp. gr. 21.02 (20°C) valence -1, -h1, 2,3, 4,5, 6, 7. Discovery of rhenium is generally attributed to Noddack, Tacke, and Berg, who announced in 1925 they had detected the element in platinum ores and columbite. They also found the element in gadolinite and molybdenite. By working up 660 kg of molybdenite they were able in 1928 to extract 1 g of rhenium. The price in 1928 was 10,000/g. Rhenium does not occur free in nature or as a compound in a distinct mineral species. It is, however, widely spread throughout the earth s crust to the extent of about 0.001 ppm. Commercial rhenium in the U.S. today is obtained from molybdenite roaster-flue dusts obtained from copper-sulfide ores mined in the vicinity of Miami, Arizona, and elsewhere in Arizona and Utah. Some molybdenites... 

Extraction. The process of extraction of the rare earths from minerals and their isolation as a group from the other elements with which they are generally associated is not a complicated one but, in most cases, it does demand the use of large-scale apparatus. In general, the silicates such as allanite, cerite, and gadolinite are opened up, or cracked, by treatment of the finely powdered mineral with hot concentrated nitric or hydrochloric acid... 

The following procedure has been used in the extraction of Norwegian gadolinite, Virginia allanite, and Swedish cerite. The extraction of gadolinite is described here for illustration. 

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