US 4,265,862 A · Process for purifying rare-earth compositions using fractional sulfate precipitation

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.

Claims7

Dependent claims

A process for purifying a composition comprising at least one rare-earth element and at least one acid-soluble radioactive impurity of the actinium decay chain, said process comprising the steps of:

(1) forming an aqueous solution of said composition having a pH between 4 and 6.5;
(2) precipitating a portion of said rare earth and said radioactive impurity by adding to said solution in an amount sufficient to effect such precipitation and 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 sulfate ion-providing salt;
and
(iv) a selective precipitating agent consisting of a compound or salt selected from the group consisting of:
(a) nitrogen-containing heterocyclic ring compounds having an hydroxyl group located in a .beta. or .gamma. position with respect to a nitrogen atom in the heterocyclic ring and
(b) ammonium salts of N-nitrophenylhydroxylamines;
(3) separating the solution from the precipitate;
and
(4) recovering purified rare earth from the solution.

9 more elements

Dependencies are inferred from the claim text.

Process for purifying rare-earth compositions using fractional sulfate precipitation

Life of this patent

Process for purifying rare-earth compositions using fractional sulfate precipitation

Life of this patent

Abstract

Claims7