COMPARATIVE-STUDY OF THE MUTUAL SEPARATION CHARACTERISTICS AND MECHANISM FOR NEIGHBORING RARE-EARTH ELEMENTS FROM BINARY CHLORIDE MIXTURES AND OXIDE MIXTURES VIA VAPOR COMPLEXES

A comparative study of the mutual separation characteristics and mecha nism was made for neighboring rare-earth elements La, Ce, Pr, and Nd f rom their binary chloride mixtures and oxide mixtures using a chemical vapor-transport reaction under a suitable temperature and pressure gr adient. The separation factors, expressed as the atomic ratios for the resulting chlorides, were observed within 6 h up to 21.4 for La: Ce, greater than or equal to 100 for Pr: Ce, and 1.84 for Pr:Nd from the o xide mixtures; however, they were only 12.3 for La: Ce, 5.79 for Pr:Ce , and 1.32 for Pr:Nd from the chloride mixtures under identical reacti on conditions, using AlCl3 as the sole complex former. It was also obs erved for the mutual separation from the oxide mixtures that the separ ation factors increased when KCl was added as another complex former, but decreased several times when either without chlorine in the carrie d gas, or without active carbon in the raw material, or under a poor v apor-transport condition. These results provide evidence that this rea ction for the oxide mixtures would mainly be the combination of a carb othermic reduction-chlorination of the oxides, complexation of the chl orides, and transportation of the vapor complexes.