METHOD FOR EXTRACTING MEDIUM AND HEAVY RARE EARTH ELEMENTS FROM MIXTURE OF RARE EARTH ELEMENTS

摘要

PURPOSE:To extract efficiently almost all of medium and heavy rare earth elements from an acidic aqueous soln. contg. salts of light rare earth elements and medium and heavy rare earth elements by dividing the soln. into two parts and an extracting reagent contg. a specified org. phosphorus compound into two parts and by transferring rare earth elements from the aqueous soln. to the extracting reagent by a prescribed method. CONSTITUTION:Part of the acidic aqueous soln. contg. salts of light rare earth elements and medium and heavy rare earth elements is treated with part of an extracting reagent contg. an org. phosphorus compound represented by the formula (where X is -OH, -OR' or R', and each of R and R' is alkyl) as the effective component while adjusting the pH of the aqueous soln., and the extracting reagent contg. rare earth elements transferred from the aqueous soln. is taken out. The remainder of the extracting reagent is continuously fed to the first stage of a multistage extracting apparatus, an aqueous acid soln. to the final stage, and the remainder of the acidic aqueous soln. and the used extracting reagent are continuously fed to the medium stage. The acidic aqueous soln. contg. a reduced amount of medium and heavy rare earth elements is taken out of the first stage, and the extracting reagent contg. rare earth elements enriched with medium and heavy rare earth elements out of the final stage. The extracting reagent is brought into contact with an aqueous acid soln. to separate the enriched rare earth elements from the extracting reagent.