Abstract: A process is disclosed for purifying a composition comprising at least one rare-earth element. The process is useful for removing radioactive impurities from these elements. The process comprises the steps of:(1) forming an aqueous solution of the composition to be purified having a pH between 4.0 and 6.5;(2) precipitating a portion of the rare earth and the radioactive impurities by adding to the solution, while maintaining the pH between 4.0 and 6.5;(i) a soluble barium or strontium salt;(ii) a soluble aluminum, magnesium or zirconium salt;(iii) a selective precipitating agent; and(iv) a sulfate ion-providing salt.The preferred selective precipitating agent is 8-hydroxyquinoline. After precipitation, the process is completed by the steps of:(3) separating the solution from the precipitate and(4) recovering purified rare earth from the solution.The process produces highly purified rare earth which can be used to form phosphors for X-ray screens.