METHOD FOR RECOVERING RARE EARTH ELEMENT FROM NOBLE METAL SMELTING SLAG

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PROBLEM TO BE SOLVED : To recover high-purity rare-earth elements from a noble metal smelting slag through a simple and inexpensive process without using an expensive organic solvent extraction method. SOLUTION : A method for recovering rare-earth elements from a noble metal smelting slag includes continuously carrying out the following processes : an inorganic acid leaching process of dissolving the noble metal smelting slag including rare-earth elements in the aqueous solution of inorganic acids excluding sulfuric acid and phosphoric acid to obtain an acid leachate including the rare-earth elements; a cementation process of adding a metallic iron to the acid leachate to precipitate heavy metals replaceable and precipitable with iron, and removing the heavy metals by solid-liquid separation; an oxidation process of adding an oxidant to the heavy metal-removed acid leachate to convert the divalent Fe ions to the trivalent Fe ions by oxidation; a neutralization process of adjusting the pH of the acid leachate after oxidation to 5 to 7 to precipitate the trivalent Fe ions and aluminum ions as hydroxides to remove by solid-liquid separation; and a recovery process of adjusting the pH of the separated acid leachate to 8 to 10 and precipitating the rare-earth elements as hydroxides to recover by solid-liquid separation. SELECTED DRAWING : Figure 1 COPYRIGHT : (C)2016, JPO&INPIT