US4053561A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Removal of fluorine from phosphatic solutions
Assignee: Stauffer Chemical Co
•
Filing: 1975-08-14
•
Granted: 1977-10-11
•
Expires: 1995-08-14
Abstract
Abstract A method for removing fluoride ions from phosphoric acid by neutralizing said acid to a pH between about 5 and about 9, contacting the neutral salt solution thereby formed with an insoluble alkaline earth metal phosphate salt, and lowering the pH to convert the solution back to a purified acid.
Inventors
- 👤 Mazin R. Irani
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 19:03
CPC Classifications
C; C01; C01B; C01B25/00; C01B25/16; C01B25/26; C01B25/28; C01B25/30; C01B25/301; C01B25/303; C01B25/38; C01B25/40; C01B25/405
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
49 words
A method for removing fluoride ions from phosphoric acid comprising the steps of neutralizing said acid to a pH between about 5 and about 9, separating precipitated impurities, contacting the neutral salt solution thereby formed with an insoluble alkaline earth metal phosphate salt, and separating the neutral salt solution.
Claim 2
Independent Claim
49 words
A method for removing fluoride ions from phosphoric acid comprising the steps of neutralizing said acid to a pH between about 5 and about 9, separating precipitated impurities, contacting the neutral salt solution thereby formed with an insoluble alkaline earth metal phosphate salt, and separating the neutral salt solution.
Claim 3
Dependent Claim
60 words
The method of claim 1 wherein the neutralization of said phosphoric acid is accomplished by contacting said acid with an alkaline reagent selected from the group consisting of ammonia, or compounds whose cations are selected from the group consisting of sodium, potassium and ammonium, and whose anions are selected from the group consisting of carbonate, bicarbonate, hydroxide and mixtures thereof.
Claim 4
Dependent Claim
28 words
The method of claim 2 wherein said neutralization is accomplished with a reagent selected from the group consisting of sodium carbonate, sodium bicarbonate, sodium hydroxide, and mixtures thereof.
Claim 5
Dependent Claim
32 words
The method of claim 1 wherein said neutralization is accomplished by contacting said acid with an alkali metal loaded ion exchange resin selected from the group consisting of sodium, potassium and ammonium.
Claim 6
Dependent Claim
13 words
The method of claim 4 wherein said ion exchange resin is sodium loaded.
Claim 7
Dependent Claim
14 words
The method of claim 1 wherein said neutralization is accomplished by means of electrodialysis.
Claim 8
Dependent Claim
24 words
The method of claim 1 wherein said alkaline earth metal phosphate salt is selected from the group consisting of calcium, magnesium and mixtures thereof.
Claim 9
Dependent Claim
29 words
The method of claim 7 wherein said insoluble alkaline earth metal phosphate salt has an alkaline earth metal to phosphorus mole ratio varying from about 1.4:1 to about 1.8:1
Claim 10
Dependent Claim
28 words
The method of claim 7 wherein said alkaline earth metal phosphate is a calcium salt selected from the group consisting of hydroxy apatite, tricalcium phosphate, and mixtures thereof.
Claim 11
Dependent Claim
15 words
The method of claim 1 wherein said neutral salt solution is reconverted to phsophoric acid.
Claim 12
Dependent Claim
24 words
The method of claim 10 wherein said reconversion is accomplished by contacting the neutral salt solution with a hydrogen ion loaded cation exchange resin.
Claim 13
Dependent Claim
14 words
The method of claim 10 wherein said reconversion is accomplished by means of electrodialysis.
Claim 14
Dependent Claim
27 words
The method of claim 10 wherein said reconversion is accomplished by contactng with a mineral acid selected from the group consisting of sulfuric, hydrochloric and nitric acids.
Claim 15
Dependent Claim
12 words
The method of claim 13 wherein said mineral acid is sulfuric acid.
Claim 16
Dependent Claim
22 words
The method of claim 1 wherein the fluorine content of said neutral salt solution after said contacting, complies with food grade requirements.
Claim 17
Dependent Claim
18 words
The method of claim 10 wherein the fluorine content of said reconverted acid complies with food grade requirements.
References Cited (Backward Citations)
US2044940A
Cited
GB467843A
Cited
DE1284404B
Cited
GB1024924A
Cited
US3645682A
Cited
US3872215A
Cited
US3937783A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1980-10-10 | 1981-04-11 | 1981-10-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-10-10 | 1985-04-11 | 1985-10-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-10-10 | 1989-04-11 | 1989-10-11 | $7700.00 | Window Closed / Lapsed |