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US4650652A
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Process for recovering highly pure rare earth oxides from a waste rare earth phosphor
Assignee: Mitsubishi Chemical Corp
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Filing: 1985-01-24
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Granted: 1987-03-17
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Expires: 2005-01-24
Abstract
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 DEG 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 DEG C. and then baking them.
Inventors
- 👤 Masaru Naitou
- 👤 Masatake Yoshikawa
- 👤 Kinichiro Narita
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 03:24
CPC Classifications
C; C01; C01F; C01F17/00; C07; C07C; C07C51/00; C07C51/41; C07C51/412; C01F17/20; C01F17/206; C01F17/218; C09; C09K; C09K11/00; C09K11/01; C09K11/08; C09K11/77; C09K11/7783; C09K11/7784; C09K11/7787; C09K11/7789; Y; Y02; Y02W; Y02W30/00; Y02W30/50
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
111 words
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° C. in an amount of from 0.3 to 1.8 times the theoretical amount, thereby precipitating rare earth oxalates from the solution; and (c) washing the precipitated rare earth oxalates with warm water having a temperature of at least 50° C., and baking the washed oxalates.
Claim 2
Dependent Claim
111 words
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° C. in an amount of from 0.3 to 1.8 times the theoretical amount, thereby precipitating rare earth oxalates from the solution; and (c) washing the precipitated rare earth oxalates with warm water having a temperature of at least 50° C., and baking the washed oxalates.
Claim 3
Dependent Claim
23 words
The process according to claim 1, wherein the waste rare earth oxysulfide phosphor is mainly composed of Y 2 O 2 S phosphor.
Claim 4
Dependent Claim
23 words
The process according to claim 1, wherein the waste rare earth oxysulfide phosphor is mainly composed of La 2 O 2 S phosphor.
Claim 5
Dependent Claim
23 words
The process according to claim 1, wherein the waste rare earth oxysulfide phosphor is mainly composed of Gd 2 O 2 S phosphor.
Claim 6
Dependent Claim
37 words
The process according to claim 1, wherein the total amount of all rare earth oxysulfide compounds contained in the waste rare earth phosphor is at least 80% by weight as computed as RE 2 O 2 S.
Claim 7
Dependent Claim
46 words
The process according to claim 1, wherein the amount of hydrochloric acid is from 1.2 to 1.7 times the theoretically required amount of 6 mole and the amount of H 2 O 2 is from 2 to 7 times the theoretically required amount of 1 mole.
Claim 8
Dependent Claim
28 words
The process according to claim 1, wherein the amount of oxalic acid present in solution ranges from 0.5 to 1.5 times the theoretical amount required for oxalate formation.
Claim 9
Dependent Claim
21 words
The process according to claim 1, wherein the temperature of the wash water of step (d) is at least 80° C.
Claim 10
Dependent Claim
31 words
The process according to claim 1, wherein said solution containing the dissolved phosphor is adjusted to a rare earth metal ion concentration of 0.5±0.1 gram ion per liter in said solution.
Claim 11
Dependent Claim
46 words
The process according to claim 1, wherein said waste rare earth oxysulfide phosphor has a total rare earth metal compound content of at least 80% by weight, a Fe impurity content of at least 1,500 ppm and a Ca impurity content of at least 50.0 ppm.
References Cited (Backward Citations)
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1990-03-16 | 1990-09-15 | 1991-03-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-03-16 | 1994-09-15 | 1995-03-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-03-16 | 1998-09-15 | 1999-03-17 | $7700.00 | Window Closed / Lapsed |