Yttrium bromate

Cerous iodates and the iodates of the other rare earths form crystalline salts sparingly soluble in water, but readily soluble in cone, nitric acid, and in this respect differ from the ceric, zirconium, and thorium iodates, which are almost insoluble in nitric acid when an excess of a soluble iodate is present. It may also be noted that cerium alone of all the rare earth elements is oxidized to a higher valence by potassium bromate in nitric acid soln. The iodates of the rare earths are precipitated by adding an alkali iodate to the rare earth salts, and the fact that the rare earth iodates are soluble in nitric acid, and the solubility increases as the electro-positive character of the element increases, while thorium iodate is insoluble in nitric acid, allows the method to be used for the separation of these elements. Trihydrated erbium iodate, Er(I03)3.3H20, and trihydrated yttrium iodate, Yt(I03)3.3H20,... 

Sm, Eu and Gd can be concentrated by crystallization through double magnesium nitrates, followed by crystallization of bismuth magnesium nitrates [30]. Sm and Eu are then removed by a proceedure based on valence change, and Gd is recovered by bromate crystallizations. Yttrium group earths may be conveniently separated by bromate crystallization. 

Classical methods of separation [7] are (1) fractional crystallization, (2) precipitation and (3) thermal reactions. Fractional crystallization is an effective method for lanthanides at the lower end of the series, which differ in cation radius to a large extent. The separation of lanthanum as a double nitrate, La(N03)3-2NH4N03-4H20, from praseodymium and other trivalent lanthanide with prior removal of cerium as Ce4+ is quite a rapid process and is of commercial significance. Other examples are separation of yttrium earths as bromates, RE(Br03>9H20 and use of simple nitrates, sulfates and double sulfate and alkali metal rare earth ethylenediamine tetraacetate complex salts in fractional crystallization separation. 

Yttrium is one of the most abundant rare earth elements and its purification is easily accomplished. Yttrium fractions from a bromate series are freed from dysprosium, holmium, and erbium by fractional precipitation with ammonia, K2OO4, or NaNC>2. The latter is probably the most effective. Yttrium salts give no absorption lines ini the viable portion of the spectrum, consequently the removal of holmium and erbium is easily observed by the direct vision spectroscope. 

Erbium may be prepared from the erbium-yttrium fractions of a bromate series by methods similar to those used in purifying yttrium, except that erbium is concentrated in the less basic fractions. Fusion of the nitrates gives a rapid separation of these two elements. 

Chlorates of the yttrium group only have been prepared, best by adilii E2(SO,)3 to Ba(C103)2, when there is formed a hydrate of tho fiirnui E(C10j)3 8 H20. The bromates are similar and arc of great service in tl yttrium group separations. 

This method has been considered the best of the classical separation procedures for producing individual elements in high purity. The most suitable compounds are ammonium nitrates (for La, Pr, and Nd) and double magnesium nitrates (for Sm, Eu, Gd). Manganese nitrates have also been used for separation of lanthanides of the cerium group (La-Nd). Bromates and sulphates have been used in the separation of the yttrium group (being the heavy lanthanides or HREE)... 

Barium bromate is useful in the preparation of the bromates of other elements, particularly those of the yttrium group of the rare earths (Synthesis 17). Workers in this field have found that the freshly prepared material is usually more satisfactory than that which is commercially available the differential in cost also definitely favors the former. The synthesis is carried out by pouring together hot saturated solutions of barium chloride and potassium bromate. Barium bromate in the form of a fine crystalline powder is obtained. 

The yttrium group solution is treated with a slight excess of ammonia solution. The resulting hydrous oxides are washed and then converted to bromates (synthesis 17) for fractional crystallization. 

If the material is to be separated into the cerium and yttrium groups of rare earths by precipitation of the double sulfates of the former, removal of the last trace of cerium is unnecessary since it does not seriously interfere in the fractionation of the cerium group double magnesium nitrates. It is important, however, that there be no ceriuni in a bromate series,... 

Yellow liquors containing principally yttrium-group earths with samarium will be obtained from the most soluble fractions and wUl fail to crystallize. These may be removed from the series to be combined later with other materials of similar composition obtained in the same manner. When these fractions are of sufficient volume they should be used for the preparation of bromates (synthesis 17). 

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... 

Different, more specific, separation techniques were developed, each one having its special characteristics. It could be separation of other double salts - nitrates, oxalates - composed of a RE metal ion and another cation present in the solution, for example K+, Na+, NH or Mg. Double ammonium nitrate may be used for removal of lanthanum and the separation of neodymium from praseodymium. Members within the cerium group may be separated using double manganese nitrates, while elements in the yttrium group are separated using the differences in solubihty of their bromates. Auer von Welsbach did much work with RE-ammonium oxalate systems. Charles James in the USA developed an effective technique with RE-magne-sium double salts. 

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