Sequential separation of the yttrium - Heavy rare earths by fractional hydroxide precipitation

In the course of the treatment of monazite in Brazil a fraction of crude yttrium carbonate is obtained. The main constituents of this fraction are: Y2O3 (76.7%), Dy2O3 (9.31%), Er 2O3 (3.21%), Yb2O3 (2.34%), Lu 2O3 (1.56%), Ho2O3 (1.40%), Tb 4O7 (0.97%), Gd2O3 (0.69%), CeO 2 (0.43%), Tm2O3 (0.33%), Nd2O 3 (0.22%), La2O3 (0.21%), Sm2O 3 (0.14%), Pr6O11 (0.13%), and minor impurities like nickel, calcium, and iron. An alternative process based on the homogeneous precipitation technique has been studied for sequential separation of yttrium from heavy rare earths. The first step of the process is the dissolution of the crude yttrium carbonate using hot hydrochloric acid. The resultant filtered solution of pH 2-3 has 30-35gl-1 total rare-earth elements (REE). From this solution the lanthanides were precipitated by the controlled hydrolysis of hot urea and the precipitate filtered off. The homogeneous precipitation is repeated once more. Yttrium is kept in the filtrate. The final yttrium fraction has 86.2% Y2O3. If the original rare-earth solution is spiked with an amount of lanthanum a most efficient separation of yttrium was obtained. In this paper, the influence of lanthanum to improve the yttrium separation is discussed. This separation envisages an industrial application. © 2004 Elsevier B.V. All rights reserved.