Method for recovering rear-earth element

Abstract

To provide a method for recovering rare earths where the intrusion of impurities is prevented, and large quantities of rare earths are recovered at a low cost. The method for recovering rare earths comprises: a first stage where rare earth magnet scrap produced from either or both of the production process of a rare earth magnet and the city is fed to sulfuric acid, and rare earths in the rare earth magnet scrap are dissolved in the sulfuric acid; a second stage where components which do not dissolve in the sulfuric acid are removed so as to obtain a rare earth-containing solution; a third stage where an ammonia aqueous solution is added to the solution; a fourth stage where the ammonium salt of rare earth-sulfuric acid produced by the addition of the ammonia aqueous solution is crystallized; and a fifth stage where the crystals of the ammonium salt of rare earth-sulfuric acid produced in the fourth stage are recovered.

Description

technical field [0001] The invention relates to a method for recovering rare earth elements from rare earth magnet scraps. Background technique [0002] In the conventional manufacturing process of rare earth magnets, a large amount of slag and tangible chips containing rare earth elements (rare earth elements) are generated by cutting and grinding. Also, products using rare-earth magnets (rare-earth magnets) (for example, motors for hard disks, etc.) are discarded as waste products. These rare-earth magnet scraps contain about 30% by mass of rare-earth elements, so it is necessary to develop a method for recovering rare-earth elements. [0003] For example, Patent Document 1 discloses a method for recovering alloy scraps containing rare earth metals: dissolving the alloy scraps containing rare earth elements while being put into the heating part of the melting furnace, and slowly releasing the solidified alloy scraps from the lower part. Slowly pull down to recover the al...

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Problems solved by technology

[0010] However, in the invention of Patent Document 1, since carbon and silicon are recovered from the grinding machine used when cutting and grinding the rare earth magnet, the paint applied to prevent oxidation of the rare earth magnet is also recovered as residue at the same time, Therefore, there is a problem that the purity of the recovered rare earth element decreases, and the performance of the rare earth magnet that reuses the rare earth element decreases.

In addition, in the inventions of Patent Documents 2 and 3, since nitric acid or hydrochloric acid is used to dissolve rare earth elements, there is a problem that it is necessary to take measures against corrosion of the reaction container, and there is also a problem that the rare earth elements dissolved per unit liquid volume of nitric acid or hydrochloric acid The problem that the amount of elements is small and impractical

In addition, in the invention of Patent Document 4, there is a problem that complicated operations such as solvent extraction and back extraction must be performed, and treatment of an organic solvent is required.

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