Monazite europium

As with other rare-earth metals, except for lanthanum, europium ignites in air at about 150 to I8O0C. Europium is about as hard as lead and is quite ductile. It is the most reactive of the rare-earth metals, quickly oxidizing in air. It resembles calcium in its reaction with water. Bastnasite and monazite are the principal ores containing europium. 

Europium is the 13th most abundant of all the rare-earths and the 55th most abundant element on Earth. More europium exists on Earth than all the gold and silver deposits. Like many other rare-earths, europium is found in deposits of monazite, bastnasite, cerite, and allanite ores located in the river sands of India and Brazil and in the beach sand of Florida. It has proven difficult to separate europium from other rare-earths. Today, the ion-exchange... 

Several other processes also are apphed for the commercial production of europium. In general, all processes are based upon the initial steps involving opening the mineral (bastnasite or monazite) with sulfuric acid or sodium hydroxide, often followed by roasting and solubihzation. In one such process after separation of cerium, the soluble rare earth chloride mixture in HCl solution is pH adjusted and treated with bis(2-ethylhexyl)phosphate to obtain europium sesquioxide, EuaOs. 

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. 

Europium occurs in the rare-earth fluocarbonaie mineral basmasite. mainly found in southern California. The mineral contains between 0.09 and 0.11% EuiOi, Other minerals, such as xenolime and monazite. also contain europium compounds, and sometimes they are used as sources of he element. 

As a metal, europium is very reactive so that one usually finds it under its trivalent, triply oxidized form (Eu3+ ion) in oxides or salts. A divalent form (Eu2+) also displays some stability. Two minerals that contain many of the lanthanide elements, which are separated by liquid-liquid extraction, are commercially important monazite (found in Australia, Brazil, India, Malaysia, and South Africa) and bastnasite (found in China and the United States). 

The most common ores of europium are monazite, bastnasite, and gadolinite. 

Preparation and Characterization of Lanthanide and Actinide Solids. Crystalline / element phosphates were prepared as standards for comparison to the solids produced in the conversion of metal phytates to phosphates. The europium standard prepared was identified by X-ray powder diffiaction as hexagonal EuP04 H20 (JCPDS card number 20-1044), which was dehydrated at 204-234 °C and converted to monoclinic EUPO4 (with the monazite structure) at 500-600 °C. The standard uranyl phosphate solid prepared was the acid phosphate, U02HP04 2H20 (JCPDS card number 13-61). All attempts to prepare a crystalline thorium phosphate failed, though thorium solubility was low. In the latter case the solids were identified as amorphous Th(OH)4 with some minor crystalline inclusions of Th02. 

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. 

Before 1960, the production of the rare earth elements was approximately 2 ktons per year. Production was mainly from monazite (and xenotime) from placer deposits (Geschneider 2011). The start of the growth of the rare earth industry began in the early 1960s, when it was discovered that the element europium (Eu) gave an intense red luminescence when exited by electrons. This was very quickly utilized in the development of color TV s (Geschneider 2011). 

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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