Monazite gadolinium

Gadolinium is found in several other minerals, including monazite and bastnasite, both of which are commercially important. With the development of ion-exchange and solvent extraction techniques, the availability and prices of gadolinium and the other rare-earth metals have greatly improved. The metal can be prepared by the reduction of the anhydrous fluoride with metallic calcium. 

Gadohnium is the 40th most abundant element on Earth and the sixth most abundant of the rare-earths found in the Earths crust (6.4 ppm). Like many other rare-earths, gadolinium is found in monazite river sand in India and Brazil and the beach sand of Florida as well as in bastnasite ores in southern California. Similar to other rare-earths, gadolinium is recovered from its minerals by the ion-exchange process. It is also produced by nuclear fission in atomic reactors designed to produce electricity. 

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. 

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-... 

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). 

The abundance of gadolinium in Earth s surface is estimated at about 4.5 to 6.4 parts per million. That would make it one of the most abundant of the rare earth elements. It ranks above bromine and uranium, but just below lead and boron in order of abundance. Some minerals in which it occurs are monazite, bastnasite, samarskite, gadolinite, and xenotime. 

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. 

Gadolinium occurs as its oxide in gadolinite [1] and is found in several other minerals, including monazite and bastnasite, which are of commercial importance. Seventeen isotopes of the element are now recognized. Natural Gd, however, is a mixture of only seven isotopes [2]. The element constitutes 63 x 10" % (= 6.3 xg/g) of the earth s crust [1,3]. To the best of our knowledge no data are available in the literature that deal with its concentration in oceans, drinking water, or diet. 

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