Purification of europium

Claim 1

THE PROCESS OF PURIFYING EUROPIUM IN A MIXTURE OF SOLUBLE TERVALENT RARE EARTH METAL SALTS IN AN AQUEOUS SOLUTION WHICH COMPRISES SUBJECTNG THE EUROPIUM-CONTAINING SOLUTION, THE EUROPIUM CONTENT OF WHICH IS AT LEAST 11% BASED ON TOTAL RARE EARTH OXIDES, TO CONDITONS REDUCING SELECTIVELY THE EUROPIUM TO THE DIVALENT STATE THEREBY PRODUCING AN AQUEOUS SOLUTION OF A MIXTURE OF SOLUBLE DIVALENT EUROPIUM IONS AND SOLUBLE TERVALENT IONS OF OTHER RARE EARTH METALS, CONVERTING SAID RARE EARTH METAL SALTS TO SULFATES BY ADDING TO SAID SOLUTION FULFATE ION AS A SOLUBLE SULFATE COMPOUND WHICH DOES NOT INTERFERE WITH THE SEPARATION AND PURIFICATION OF EUROPIUM, SAID ADDITION OF SULFATE ION BEING MADE UNDER NON-XOIDIZING CONDITIONS, THEREBY TO PRECIPITATE THE EUROPOUS SULFATE CRYSTALS AND A MINOR PORTION OF THE TERVALENT RARE EARTH METAL SALTS AS IMPURITIES AND RETAINING THE REMAINDER OF THE RARE EARTH METAL SALTS IN SOLUTION AS SOLUBLE TERVALENT SALTS, SEPARTING THE IMPURE EUROPOUS SULFATE CRYSTALS FROM THE MOTHER LIQUOR, CONVERTING SAID EUORPOUS SULFATE TO EUROPOUS CARBONATE BY TREATING THE EUROPOUS SULFATE WITH A STRONG ALKALINE SOLUTION OF A CARBONATE, SAID CONVERSION TO EUROPOUS CARBONATE BEING CARRIED OUT UNDER NONOXIDIZING CONDITIONS TO RETAIN THE EUROPIUM IN THE DIVALENT STATE, DISSOLVING SAID EUROPOUS CARBONATE IN AN ACID WHICH DOES NOT INTERFERE WITH THE SEPARATION AND PURIFICATION OF OXIDIZING CONDITIONS AND SO AVOIDING REOXIDATION OF EUROPIUM, ADDING ALKALI TO SAID EUROPOUS SALT SOLUTION TO RAISE THE PH TO AT LEAST ABOUT 8 BUT NOT GREATER THAN ABOUT 9.5, THEREBY PRECIPITATING SAID REMAINDER OF TERVALENT RARE EARTH IMPURITIES AS THE HYDROXIDES WHILE RETAINING THE DIVALENT PURIFIED EUROPIUM IN SOLUTION AND SEPARATING THE PRECIPITATED TERVALENT RARE EARTH IMPURITIES FROM THE MOTHER LIQUOR.