Laval University From the SelectedWorks of Fathi Habashi 2008 Scandium Fathi Habashi Available at: https://works.bepress.com/fathi_habashi/743/ Metall-Magazin Scandium Habashi, F. (1) When the Russian chemist Dmitri Ivanovich num. Although scan- that he called thortveitite, contained Mendeleev (1834-1907) proposed the Periodic dium has two elec- 30 to 40% of Sc2O3. This mineral was Table in 1869 he predicted the existence of trons in the outermost also found later, in Madagascar. It has eka-boron, which would have an atomic weight shell and one would the composition (Sc,Y)2Si2O7. between 40 of calcium and 48 of titanium. The expect that it would Bazzite: Be3(Sc,Al)2Si6O18 is another element was discovered by Swedish chemist Lars form divalent com- silicate mineral containing scandium Fredrik Nilson (1840-1899) in 1878 by spec- pounds, yet its most discovered in 1915. troscopic analysis of the minerals euxenite and common valency state Euxenite: (Y,Ca,Ce,U,Th)(Nb,Ta,Ti)2O6 gadolinite, which had not yet been found any- is three resembling occurs in granite pegmatites and detri- where except in Scandinavia. By processing 10 aluminum. tal black sands. It is commonly par- kg of euxenite and other residues of rare-earth Scandium is usually tially amorphous due to radiation associated with the damage.It was first described in 1870 minerals, Nilson was able to prepare about 2 lanthanides and the and named from the Greek word g of the oxide of the new metal in high purity metal has hexago- meaning hospitable or friendly to and called the metal scandium in honour of his nal structure like the strangers, in allusion to the many rare fatherland. It was another Swedish chemist Per yttrium, lanthanum, elements that it contains. It is found Teodor Cleve (1840-1905) who later pointed out and the lanthanides. in many locations worldwide, notably that Nilson‘s scandium was identical with Men- On the other hand alu- its type locality in Jølster, Sunnfjord, deleev‘s eka-boron. minum has face cen- Norway. Other locations include the tered cubic structure. Ural Mountains, Sweden, Minas Gerais candium has a unique position Scandium forms an insoluble hydrox- in Brazil, Ampangabe in Madagas- in the modern Periodic Table. It ide, fluoride, or oxalate under proper car. Ontario, Canada; and in Arizona, Sis a transition metal like yttrium conditions, similar to the rare earths. Wyoming and Colorado in the USA. and lanthanum, however it resembles Gadolinite: (Ce,La,Nd,Y)2FeBe2Si2O10 aluminum more than it resembles the Occurence is a silicate mineral nearly black in other transition metals. For example, color with vitreous luster. Gadolinite it has a single valency like alumi- Scandium is widespread in nature was named in 1800 in honor of Johan num while the transition metals have but in small concentrations; its rela- Gadolin, the Finnish mineralogist - multiple valencies. All its compounds tive abundance is 5 x 10-4 % like the chemist who first isolated an oxide of are colorless like yttrium, lanthanum, lanthanides. It occurs in association the rare earth element yttrium from and aluminum thus not resembling of with the lanthanides, with uranium the mineral in 1792. However, gadoli- the transition metals which all have ores, in laterites, in bauxite, in wolf- nite does not contain more than trace colored ions in solution. Mendeleev ramite, and in ilmenite. Thortveitite, amounts of gadolinium. successfully predicted the properties euxenite, and gadolinite are the only of scandium by linking it with alumi- known concentrated sources of this Recovery element. The present main source of scandium metal is from the military Scandium is present in all rare earth stockpiles of the former Soviet Union minerals, although only in trace (mainly in Ukraine), which were them- amounts. Because it has similar chem- selves extracted from uranium tail- ical properties to the other rare earth ings. Scandium was also extracted in elements, it cannot be obtained by the former Soviet Union from ilmenite. selective precipitation as the oxalate It is believed however that all these or a double salt. The most effective operations are no longer functioning. separation is by solvent extraction, Scandium ion, Sc3+, has ionic radius scandium behaving quite differently close to that of Fe2+, Mg2+, Ti4+, and from the other rare earth metals. For Zr4+ thus isomorphism is possible. The example, it is readily extracted by only naturally occurring isotope of diethyl ether from thiocyanate solu- scandium is 45Sc. tion. Tributylphosphate, known as TBP Thortveitite: In 1911, Schetelig, in is an effective extractant from chloride Lars Fredrik Nilson (1840-1899) Norway, discovered a silicate mineral, solutions, while the other rare earth 814 · 62. Jahrgang · 12/2008 Metall historisch then prepared in multi-pound lots by nium ore to a fluidized bed chlorinator chemical separation techniques. at about 1000 °C to produce a vapors of TiCl4 and FeCl3. Scandium remains Extraction from wolframite in the residue and can be recovered by leaching the residue with hydro- Wolframite, (Fe,Mn)WO4, concentrates chloric acid, followed by extraction contain 500–800 ppm scandium. Two with tributyl phosphate. Scandium methods have been proposed for the is then precipitation from the strip recovery of scandium: solution by an ammonium hydroxide. When digested with acid, iron, Scandium hydroxide is then calcined manganese, and scandium go to oxide. The residue generally also into solution while tungstic acid, contains yttrium and lanthanides, and H2WO4, is precipitated. The solu- the yttrium and lanthanides can also tion can then be treated further be recovered from the residue as a part to recover scandium. of the scandium recovery process. When wolframite is digested with sodium carbonate, water-solu- Preparation of metallic scandium Per Teodor Cleve (1840-1905) ble sodium tungstate is formed. The residue is then dissolved in Fischer, Brunger, and Grieneisen pre- elements are hardly extracted. Organo- hydrochloric acid and scandium pared metallic scandium for the first phosphoric acids such as diethylhexyl is preferentially extracted by trib- time in 1937 by electrolysis of a eutec- phosphoric acid, known as D2-EHPA utyl phosphate and stripped with tic melt of potassium, lithium, and are much more effective extractants 8 M hydrochloric acid. Scandium scandium chlorides at a temperature for scandium than for the other rare is then precipitated with ammo- of 700 to 800 °C. Tungsten wires in a earth elements. nia in presence of ammonium pool of liquid zinc were the electrodes Scandium is not recovered from rare chloride, and final purification of in a graphite crucible. Pure scandium earth minerals such as monazite or the scandium by TBP extraction. is now produced by reducing scan- bastnasite but it recovered mainly as a dium fluoride with calcium metal: by-product from two main sources: Extraction from bauxite Uranium ores in Canada and 2 ScF3 + 3 Ca → 2 Sc + 3 CaF2 USA In the production of alumina from Uranium and ilmenite processing red mud by Bayer process scandium The production of the first pound in the Former Soviet Union remains in the red mud. A pilot plant of 99% pure scandium metal was Extraction from uranium ores was constructed which includes acid announced in 1960. In 1954 traces of scandium in ura- leaching of the red mud, ion-exchange nium ores of the Blind River deposit separation of scandium and lantha- Applications in Ontario, Canada were detected by nides from iron, and subsequent liq- spectrum analysis. In 1959 a unit was uid-liquid extraction of the eluate The metal has little commercial impor- installed for the extraction of thorium for further scandium purification and tance. In 1970 pure scandium cost sev- compounds from the spent solution. enrichment. eral thousand dollars per pound. The This was followed in 1960 by the current price of refined scandium is extraction of 0.9 kg of scandium oxide Extraction from laterites in the order of US $600 per kilogram. from which the metal was prepared. World production of the metal is in the Discovery of scandium in the late Scandium can be recovered from lat- order of 2,000 kg per year, generally 1950s in the Vitro solvent extraction erites during the sulfuric acid leaching as a by-product of uranium process- plant for uranium in Salt Lake City, process at high temperature and high ing. Greater consumption would allow Utah led to its commercial recovery pressure. It will dissolve together with additional price reductions. Scandium as a by-product. Micro amounts of nickel but will not be precipitated oxide finds use as a catalyst and in scandium were extracted with ura- by hydrogen sulfide like nickel. By making crucibles and other ceramic nium from the acid leach solution by adjusting the pH of the solution after parts. Scandium sulfate in very dilute dodecyl phosphoric acid, but failed to separating the nickel sulfide, scandium aqueous solution is used in agriculture follow uranium into the hydrochloric hydroxide or carbonate can then be as a seed treatment to improve the acid strip solution and were eventually precipitated. germination of corn, peas, wheat, and concentrated in the organic phase. A other plants. fluoride strip system was developed to Extraction from ilmenite However, the major application is recover scandium from the solvent as expected to be as an alloying ele- a cake containing 10% Sc2O3 and 20% A process for extracting scandium ment with aluminum since it is a ThO2. High purity scandium oxide was from titanium ore by feeding the tita- light metal. Approximately 15 dif- · 62. Jahrgang · 12/2008 815 Metall-Magazin ferent commercial Al-Sc alloys have Yttrium and Lanthanides, from Titanium - C.K. Gupta and N. Krishnamurty, Ex- Ore”, United States Patent 504 9363 been developed in Russia, and some of tractive Metallurgy of Rare Earths, CRC (1991) Press, Boca Raton, Florida 2005 them are used for aerospace applica- - L.D.