US4144185A
Expired / Lapsed
US
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Method and composition for removing calcium sulfate scale deposits from surfaces
Assignee: United States Department of the Interior
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Filing: 1978-02-24
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Granted: 1979-03-13
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Expires: 1998-02-24
Abstract
Abstract A method and composition for removing calcium sulfate scale deposits from surfaces, such as reverse osmosis membranes and electrodialysis stacks, wherein the surface to be cleaned is contacted by an aqueous solution comprising a chelating agent, a soluble carbonate and a fluorocarbon surfactant.
Inventors
- 👤 Jacob Block
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 09:52
CPC Classifications
C; C11; C11D; C11D3/00; C11D3/02; C11D3/04; C11D3/10; B; B01; B01D; B01D65/00; B01D65/02; C02; C02F; C02F5/00; C02F5/08; C11D1/00; C11D1/004; B01D2321/00; B01D2321/16; B01D2321/162
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
181 words
A composition for removing calcium sulfate scale deposits from surfaces consisting essentially of an aqueous solution of about one weight percent to maximum solubility of a polyamino carboxylic acid selected from the group consisting of ethylenediamine tetracetic acid, nitrilo triacetic acid, diethylenetriamine pentaacetic acid, N-hydroxyethylethylenediamine triacetic acid, and mixtures thereof, a minimum of about one mole of a soluble carbonate per mole of said polyamino carboxylic acid, said carbonate being selected from the group consisting of (NH 4 )HCO 3 , NaHCO 3 , KHCO 3 , Na 2 CO 3 , K 2 CO 3 , (NH 4 ) 2 CO 3 , and mixtures thereof, and from about 0.005 to 0.01 weight percent of an anionic fluorocarbon surfactant selected from the group consisting of compounds of the formulas F(CF 2 CF 2 ) n (CH 2 ) 2 S(CH 2 ) 2 COOLi and [F(CF 2 CF 2 ) n (CH 2 ) 2 O] x PO(ONH 4 ) y , where n = 3, 4 or 5, x = 1 or 2, and y = 2 or 1.
Claim 2
Dependent Claim
181 words
A composition for removing calcium sulfate scale deposits from surfaces consisting essentially of an aqueous solution of about one weight percent to maximum solubility of a polyamino carboxylic acid selected from the group consisting of ethylenediamine tetracetic acid, nitrilo triacetic acid, diethylenetriamine pentaacetic acid, N-hydroxyethylethylenediamine triacetic acid, and mixtures thereof, a minimum of about one mole of a soluble carbonate per mole of said polyamino carboxylic acid, said carbonate being selected from the group consisting of (NH 4 )HCO 3 , NaHCO 3 , KHCO 3 , Na 2 CO 3 , K 2 CO 3 , (NH 4 ) 2 CO 3 , and mixtures thereof, and from about 0.005 to 0.01 weight percent of an anionic fluorocarbon surfactant selected from the group consisting of compounds of the formulas F(CF 2 CF 2 ) n (CH 2 ) 2 S(CH 2 ) 2 COOLi and [F(CF 2 CF 2 ) n (CH 2 ) 2 O] x PO(ONH 4 ) y , where n = 3, 4 or 5, x = 1 or 2, and y = 2 or 1.
Claim 3
Dependent Claim
20 words
A method for removing calcium sulfate scale deposits from surfaces comprising contacting the deposits with the composition of claim 1.
References Cited (Backward Citations)
US3660287A
Cited
US3684720A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1982-03-12 | 1982-09-11 | 1983-03-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1986-03-12 | 1986-09-11 | 1987-03-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1990-03-12 | 1990-09-11 | 1991-03-13 | $7700.00 | Window Closed / Lapsed |