Vapor Phase Extraction and Mutual Separation of Rare Earths from Monazite Using Chemical Vapor Transport Mediated by Vapor Complexes

Rare earths chlorides (RCl3), produced by direct chlorination of monazite concentrate or chlorine free crude oxides, were extracted via vapor complexes with KCl. The complexes, RKCl4(g), decomposed along a given temperature gradient, and RCl3 was selectively deposited in a temperature region 850–990 °C. Other elements such as Th, U, and P in the monazite were concentrated at the lower temperature fractions. Coexistence of vapor complex(es) in a RCl3-POCl3 system was suggested from the difference between the yields of RCl3 for the concentrate and the crude oxides.