METHOD FOR RECOVERING RARE EARTH ELEMENTS

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PROBLEM TO BE SOLVED : To provide a process for efficiently recovering high-quality rare earth oxide from waste grinding slurry. SOLUTION : In a method of recovering rare earth elements, rare earth oxides are recovered from the waste grinding slurry containing rare earth elements in a first process [I] including steps (1)-(5), and ammonium sulfate of the process [I] and water are reproduced in a second process [II] of a step (6) and recycled in the process [I]. The process [I] comprises steps of : (1) mixing slurry containing rare earth oxides with a sulfuric acid compound, heating/roasting the mixture, and dissolving it in water to make rare earth element solution; (2) adjusting a pH value of the rare earth element solution and dissociating insoluble components; (3) adding precipitant to the solution to separate out rare earth carbonate; (4) dissociating the rare earth carbonate from the slurry; and (5) baking the rare earth carbonate to recover it as rare earth oxides. If the pH regulator and the precipitant in the process [I] are aqueous ammonia and ammonium salt, the process [II] comprises the step of : (6) aqueous ammonium sulfate solution from which the rare earth carbonate is separated is condensed to recover the aqueous ammonium sulfate solution and the water. COPYRIGHT : (C)2009, JPO&INPIT