A method is described to produce high purity rare earth oxides of the elements La, Ce, Tb, Eu and Y from phosphor, such as waste phosphor powders originating in various consumer products. One approach involves leaching the powder in two stages and converting to two groups of relatively high purity m
A method is described to produce high purity rare earth oxides of the elements La, Ce, Tb, Eu and Y from phosphor, such as waste phosphor powders originating in various consumer products. One approach involves leaching the powder in two stages and converting to two groups of relatively high purity mixed rare earth oxides. The first group containing Eu and Y is initially separated by solvent extraction. Once separated, Eu is purified using Zn reduction with custom apparatus. Y is purified by running another solvent extraction process using tricaprylmethylammonium chloride. Ce is separated from the second group of oxides, containing La, Ce and Tb by using solvent extraction. Subsequently, La and Tb are separated from each other and converted to pure oxides by using solvent extraction processes. A one-stage leaching process, wherein all rare earths get leached into the solution and subsequently processed, is also described.
대표청구항▼
1. A method for recovery of a rare earth constituent from a phosphor, the method comprising: leaching a rare earth constituent from a phosphor with H2SO4 to form a rare earth leachate solution;adjusting the rare earth leachate solution to a pH preferential to the precipitation of rare earth oxalates
1. A method for recovery of a rare earth constituent from a phosphor, the method comprising: leaching a rare earth constituent from a phosphor with H2SO4 to form a rare earth leachate solution;adjusting the rare earth leachate solution to a pH preferential to the precipitation of rare earth oxalates relative to other metal oxalates, and then precipitating the rare earth constituent from the rare earth leachate solution as one or more rare earth oxalates; andconverting the one or more rare earth oxalates to one or more rare earth oxides. 2. The method of claim 1, wherein the one or more rare earth oxides is greater than 99% pure. 3. The method of claim 1, wherein the phosphor is a powder derived from phosphor waste. 4. The method of claim 1, wherein the pH of the rare earth leachate solution is adjusted to about 2. 5. The method of claim 1, wherein the rare earth constituent comprises compounds comprising a rare earth element selected from the group consisting of La, Ce, Eu, Tb, Y and combinations thereof. 6. A method for recovery of a rare earth constituent from a phosphor, the method comprising: leaching a rare earth constituent from a phosphor to form a rare earth leachate solution;adjusting the rare earth leachate solution to a pH preferential to the precipitation of rare earth oxalates relative to other metal oxalates, and then precipitating the rare earth constituent from the rare earth leachate solution as one or more rare earth oxalates; andconverting the one or more rare earth oxalates to one or more rare earth oxides;wherein the rare earth constituent comprises compounds comprising a rare earth element selected from the group consisting of La, Ce, Eu, Tb, Y and combinations thereof; andwherein the leaching comprises a first stage of leaching Eu and Y-comprising compounds from the phosphor with about 6N H2SO4 to form a Eu and Y leachate, while La, Ce and Tb-comprising compounds from the phosphor are retained in an un-leached residue. 7. The method of claim 6, further comprising a second stage of leaching La, Ce and Tb-comprising compounds from the un-leached residue by an about 36N H2SO4 to form a La, Ce and Tb leachate. 8. The method of claim 7, wherein the first stage Eu and Y leachate and second stage La, Ce and Tb leachate are further separately processed following the leaching resulting in a high purity mixture of Eu and Y oxides and a separate high purity mixture of La, Ce and Tb oxides. 9. The method of claim 8, wherein the purity of the oxides is greater than 95%. 10. The method of claim 9, wherein the purity of the oxides is at least 99%. 11. The method of claim 6, further comprising separation and purification of individual rare earth oxides by solvent extraction or Zn reduction to achieve a high purity of greater than 99%. 12. The method of claim 8, further comprising separation of high purity Y from the high purity mixture of Eu and Y oxides by solvent extraction with a solvent system comprising a solvent selected from the group consisting of Di-(2-ethylhexyl)phosphoric acid in dilute H2SO4/HCl/HNO3, 2-ethylhexyl 2-ethylhexyl phosphonic acid in dilute H2SO4/HCl/HNO3, and combinations thereof. 13. The method of claim 12, further comprising purification of Y oxide to greater than 99% purity using solvent extraction with tricaprylmethylammonium chloride. 14. The method of claim 12, further comprising purification of Eu oxide to greater than 99% purity by Zn reduction from a mixture of Eu and Y traces after separation of Y. 15. The method of claim 12, further comprising separation of greater than 99% high purity Ce oxide from the mixture of oxides of La, Ce and Tb by solvent extraction with a solvent system comprising a solvent selected from the group consisting of Di-(2-ethylhexyl)phosphoric acid, 2-ethylhexyl 2-ethylhexyl phosphonic acid, tributyl phosphate, and combinations thereof. 16. The method of claim 15, further comprising separation of greater than 99% high purity La and Tb by solvent extraction with a solvent system comprising a solvent selected from the group consisting of Di-(2-ethylhexyl)phosphoric acid, 2-ethylhexyl 2-ethylhexyl phosphonic acid, and combinations thereof, after separation of Ce. 17. The method of claim 6, wherein the phosphor is not fired with an alkali material, such that no caustic fusion occurs. 18. The method of claim 6, wherein the method does not comprise an alkaline or acidic digestion step between leaching and precipitating. 19. The method of claim 6, wherein the rare earth constituent further comprises Gd. 20. The method of claim 6, wherein the pH of the rare earth leachate solution is adjusted to about 2. 21. The method of claim 6, wherein the one or more rare earth oxides is greater than 95% pure. 22. The method of claim 6, wherein the one or more rare earth oxides is at least 99% pure. 23. The method of claim 6, wherein the phosphor is a powder derived from phosphor waste. 24. The method of claim 6, wherein the pH of the rare earth leachate solution is adjusted to about 2. 25. A method for recovery of a rare earth constituent from a phosphor, the method comprising: leaching a rare earth constituent from a phosphor to form a rare earth leachate solution;adjusting the rare earth leachate solution to a pH preferential to the precipitation of rare earth oxalates relative to other metal oxalates, and then precipitating the rare earth constituent from the rare earth leachate solution as one or more rare earth oxalates; andconverting the one or more rare earth oxalates to one or more rare earth oxides;wherein the rare earth constituent comprises compounds comprising a rare earth element selected from the group consisting of La, Ce, Eu, Tb, Y and combinations thereof; andwherein the leaching comprises a single stage of leaching La, Ce, Eu, Tb and Y-comprising compounds from the phosphor by an about 36N H2SO4. 26. The method of claim 25, wherein a high purity mixture of La, Ce, Eu, Tb, and Y oxides results. 27. The method of claim 25, wherein the one or more rare earth oxides is greater than 95% pure. 28. The method of claim 25, wherein the one or more rare earth oxides is at least 99% pure. 29. The method of claim 25, wherein the phosphor is a powder derived from phosphor waste. 30. The method of claim 25, wherein the rare earth constituent further comprises Gd. 31. The method of claim 25, further comprising separation and purification of individual rare earth oxides by solvent extraction or Zn reduction to achieve a high purity of greater than 99%.
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Otto, Robert; Wojtalewicz-Kasprzak, Agnieszka, Method for recovery of rare earths from fluorescent lamps.
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