Process for recovering highly pure rare earth oxides from a waste rare earth phosphor
AssigneeKasei Optonix, Ltd.
InventorsMasaru Naitou, Masatake Yoshikawa, Kinichiro Narita
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Abstract
A process for recovering highly pure rare earth oxides from a waste rare earth phosphor containing at least Fe and/or Ca as impurities, which comprises dissolving the waste rare earth phosphor in an excess amount of a strong acid capable of dissolving the waste rare earth phosphor, adding to the solution at a temperature of at least 70.degree. C. oxalic acid in an amount of from 0.3 to 1.8 times the theoretical amount to obtain precipitates of rare earth oxalates, washing the precipitates with warm water having a temperature of at least 50.degree. C. and then baking them.
Claims10
A process for recovering highly pure rare earth oxides from a waste rare earth oxysulfide phosphor containing at least 500 ppm of Fe and/or 10 ppm of Ca impurities, which comprises:
- (a) dissolving the waste rare earth oxysulfide phosphor in an excess amount of a combination of hydrochloric acid and hydrogen peroxide;
- (b) adding oxalic acid to said solution at a temperature of at least 70.degree. C. in an amount of from 0.3 to 1.8 times the theoretical amount, thereby precipitating rare earth oxalates from the solution;
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- (c) washing the precipitated rare earth oxalates with warm water having a temperature of at least 50.degree. C., and baking the washed oxalates.
Dependencies are inferred from the claim text.