US4965061A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for removing fluoride from a wastewater and producing hydrofluoric acid therefrom
Assignee: FLORIDA RECOVERIES PARTNERSHIP A PARTNERSHIP UNDER FL
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Filing: 1989-01-30
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Granted: 1990-10-23
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Expires: 2009-01-30
Abstract
Abstract A process for producing hydrofluoric acid from SiF 6 2- in a wastewater is disclosed. The process is carried out by (i) combining (NH 4 ) 2 SO 4 , at a pH high enough such that the sulfate is in its divalent state, with SiF 6 2- from said wastewater in an amount in excess of that stoichiometrically required to form (NH 4 ) 2 SiF 6 as follows: (NH.sub.4).sub.2 SO.sub.4 +SiF.sub.6.sup.2- →(NH.sub.4).sub.2 SiF 6 +SO 4 2- (ii) concentrating a solution including (NH 4 ) 2 SiF 6 and excess (NH 4 ) 2 SO 4 to precipitate and separate (NH 4 ) 2 SiF 6 of high purity therefrom; (iii) re-solubilizing the (NH 4 ) 2 SiF 6 for reaction with NH 4 OH to form NH 4 F liquor and precipitated Si(OH) 4 ; (iv) separating the NH 4 F liquor from the precipitated Si(OH) 4 ; (v) reacting the NH 4 F with water to form precipitated NH 4 F·HF and ammonia gas; (vi) reacting NH 4 F·HF with NaF to yield precipitated NaF·HF and NH 4 F liquor; and (vii) heating and decomposing the NaF·HF into HF and NaF.
Inventors
- 👤 William W. Berry
- 👤 Gordon J. Rossiter
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 14:34
CPC Classifications
C; C01; C01B; C01B33/00; C01B33/08; C01B33/10; C01B33/103; C01B7/00; C01B7/19; C01B7/191; C01B7/193; C01B7/194; C02; C02F; C02F1/00; C02F1/52; C02F1/5236; C02F1/58; C02F1/583; C02F1/20; C02F1/42; C02F1/66
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
204 words
A process for producing hydrofluoric acid from SiF 6 2- comprising the steps of: (i) combining (NH 4 ) 2 SO 4 , at a pH high enough such that the sulfate is in a non-protonated state, with SiF 6 2- from said wastewater in an amount in excess of that stoichiometrically required to form (NH 4 ) 2 SiF 6 as follows: (NH.sub.4).sub.2 SO.sub.4 +SiF.sub.6.sup.2- →(NH.sub.4).sub.2 SiF.sub.6 +SO.sub.4.sup.2- (ii) concentrating a solution including (NH 4 ) 2 SiF 6 and excess (NH 4 ) 2 SO 4 to precipitate separate (NH 4 ) 2 SiF 6 therefrom, wherein the separated (NH 4 ) 2 SiF 6 has a higher purity than if stoichiometric ratios of the reactants had been used. (iii) re-solubilizing the (NH 4 ) 2 SiF 6 for reaction with NH 4 OH to form NH 4 F liquor and precipitated Si(OH) 4 ; (iv) separating the NH 4 F liquor from the precipitated Si(OH) 4 ; (v) reacting the NH 4 F with water to form precipitated NH 4 F.HF and ammonia gas; (vi) reacting NH 4 F.HF with NaF to yield precipitated NaF.HF and NH 4 F liquor; and (vii) heating and decomposing the NaF.HF into HF and NaF.
Claim 2
Dependent Claim
204 words
A process for producing hydrofluoric acid from SiF 6 2- comprising the steps of: (i) combining (NH 4 ) 2 SO 4 , at a pH high enough such that the sulfate is in a non-protonated state, with SiF 6 2- from said wastewater in an amount in excess of that stoichiometrically required to form (NH 4 ) 2 SiF 6 as follows: (NH.sub.4).sub.2 SO.sub.4 +SiF.sub.6.sup.2- →(NH.sub.4).sub.2 SiF.sub.6 +SO.sub.4.sup.2- (ii) concentrating a solution including (NH 4 ) 2 SiF 6 and excess (NH 4 ) 2 SO 4 to precipitate separate (NH 4 ) 2 SiF 6 therefrom, wherein the separated (NH 4 ) 2 SiF 6 has a higher purity than if stoichiometric ratios of the reactants had been used. (iii) re-solubilizing the (NH 4 ) 2 SiF 6 for reaction with NH 4 OH to form NH 4 F liquor and precipitated Si(OH) 4 ; (iv) separating the NH 4 F liquor from the precipitated Si(OH) 4 ; (v) reacting the NH 4 F with water to form precipitated NH 4 F.HF and ammonia gas; (vi) reacting NH 4 F.HF with NaF to yield precipitated NaF.HF and NH 4 F liquor; and (vii) heating and decomposing the NaF.HF into HF and NaF.
Claim 3
Dependent Claim
27 words
The process of claim 1 wherein 1.5-5.0 moles of (NH 4 ) 2 SO 4 are employed per mole of SiF 6 2- recovered from the wastewater.
Claim 4
Dependent Claim
24 words
The process of claim 2 wherein 1.5-3.0 moles of (NH 4 ) 2 SO 4 are employed per mole of SiF 6 2- .
Claim 5
Dependent Claim
58 words
The process of claim 1 wherein the (NH 4 ) 2 SO 4 is combined with SiF 6 2- adsorbed onto an anion exchange resin in step (i) to form a solution of free (NH 4 ) 2 SiF 6 and excess unexchanged (NH 4 ) 2 SO 4 which are then separated from said anion exchange resin.
Claim 6
Dependent Claim
118 words
The process of claim 4 further including: feeding the wastewater including SiF 6 2- through at least one fixed port; feeding the (NH 4 ) 2 SO 4 strip solution through at least one fixed port; rotating a plurality of beds of anion exchange resin about a circular path in periodic fluid communication with the fixed ports; the anion exchange resin, when in fluid communication with the wastewater being fed through at least one fixed port, being loaded with SiF 6 2- ions; and the anion exchange resin, when in fluid communication with the (NH 4 ) 2 SO 4 solution, having the SiF 6 2- stripped therefrom by formation of (NH 4 ) 2 SiF 6 .
Claim 7
Dependent Claim
67 words
The process of claim 5 wherein the (NH 4 ) 2 SO 4 strip solution is fed through at least two fixed ports and wherein an eluant interaction product formed by passing (NH 4 ) 2 SO 4 through a first fixed port is directed to at least one additional fixed port in a direction opposite to that in which the beds of anion exchange resin rotate.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-10-22 | 1994-04-23 | 1994-10-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-10-22 | 1998-04-23 | 1998-10-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-10-22 | 2002-04-23 | 2002-10-23 | $7700.00 | Window Closed / Lapsed |