| 摘要 |
PROBLEM TO BE SOLVED: To provide, when recovering a rare earth element by a sulfuric acid double salt precipitation method, a method which enables stable recovery of the rare earth element even when a scale of execution of the rare earth element recovery is expanded.SOLUTION: After a sulfuric acid double salt generating reaction is completed, a solution obtained is stirred in a state where precipitation of rare earth sulfuric acid double salt does not occur, and materials other than a solution containing a specified amount of the precipitation of the rare earth sulfuric acid double salt are recovered by passage though a solid-liquid separator. Subsequently, the solution containing the specified amount of the precipitation of the rare earth sulfuric acid double salt is allowed to stand still to precipitate the rare earth sulfuric acid double salt, and thereafter a supernatant liquid is removed and the precipitation of the rare earth sulfuric acid double salt is allowed to remain in a reaction tank. Then, in coexistence of the rare earth sulfuric acid double salt precipitation as seed crystals, an alkali metal sulfate is added to form a slurry and thereafter a solution containing the rare earth element is introduced to carry out the sulfuric acid double salt forming reaction. |
