METHOD OF PREPARING RARE-EARTH ELEMENT OXIDES Russian patent published in 2002 - IPC

FIELD: preparation of pure rare-earth element oxides with minimum losses. SUBSTANCE: rare-earth element-containing concentrate is processed into three stages. In each stage it is decomposed with 3 or 4 N hydrochloric or nitric acid at S: L ratio of 1: 2 on heating and are rare-earth element oxalates are deposited and residue is subsequently separated, washed and calcined to oxide. In first stage rare-earth element oxalates and copper are deposited. In first stage in the presence of 2N oxalic acid at pH of 1 or 2. In second and third stages rare-earth element oxalates are deposited at pH of 1.5 and excessive concentration of oxalic acid of 0.2, 0.5. Oxalates of yttrium group of rare-earth elements are deposited in the presence of acetone, and in second stage copper impurity in the form of ammonia complex and heavy metal impurity in the form of sulfides are separated. EFFECT: standard, readily available reactants and insignificant amount of energy; full separation of impurities and minimum losses of rare-earth elements. 3 cl, 25 ex, 2 tbl