RARE EARTH ELEMENT RECOVERY METHOD

摘要

Provided is a method of recovering rare-earth elements, including causing rare-earth elements particularly including Nd and Dy to leach efficiently from a raw material for leaching which contains the rare-earth elements, and separating and recovering the rare-earth elements. The method of recovering rare-earth elements includes: a leaching step including performing leaching treatment of rare-earth elements in which an acidic slurry of a raw material for leaching which contains the rare-earth elements is held under a predetermined condition, and then subjecting the slurry obtained after the leaching treatment to solid-liquid separation, yielding a leachate containing the rare-earth elements; and a separation step of separating and recovering the rare-earth elements from the yielded leachate, in which: the raw material for leaching contains Ca as CaO at a ratio of 4 to 15 mass % and Ti as TiO2 at a ratio of 2 to 13 mass % in a solid component (S); an acid aqueous solution is an acid aqueous solution of hydrochloric acid and/or nitric acid; and the leaching treatment performed in the leaching step is digestion or maceration which is performed under the heating and pressurizing conditions of a temperature of 160 to 300° C. and a pressure of 0.65 to 10 MPa, and the rare-earth elements are caused to leach together with Ca in the leaching step.

主权项

1. A method of recovering rare-earth elements, comprising:
a leaching step including preparing a slurry by adding water to a raw material for leaching which contains rare-earth elements, followed by mixing, further adding an acid aqueous solution to the slurry, followed by mixing, to adjust a pH of the slurry, performing leaching treatment in which the rare-earth elements in the raw material for leaching are transferred into the acid aqueous solution while the resultant slurry is held under a predetermined condition, and then subjecting the slurry obtained after the leaching treatment to solid-liquid separation, yielding a leachate containing the rare-earth elements; and a separation step of separating and recovering the rare-earth elements from the leachate yielded in the leaching step, wherein: the raw material for leaching comprises Ca as CaO at a ratio of from 4 to 15 mass % and Ti as TiO2 at a ratio of from 2 to 13 mass % in a solid component (S) obtained by drying the raw material for leaching under drying conditions of 110° C. and 2 hours; the acid aqueous solution comprises an acid aqueous solution which contains hydrochloric acid and/or nitric acid and adjusts the pH to from 0 to 2.7; and the leaching treatment performed in the leaching step is digestion or maceration which is performed under heating and pressurizing conditions of a temperature of from 160 to 300° C. and a pressure of from 0.65 to 10 MPa, and the rare-earth elements in the raw material for leaching are caused to leach together with Ca in the leaching step.