US3721623A
Expired / Lapsed
US
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Method of improving the salt rejection of semipermeable reverse osmosis membranes
Assignee: Graftech Technology LLC
•
Filing: 1971-07-23
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Granted: 1973-03-20
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Expires: 1991-07-23
Abstract
Abstract A method of improving the salt rejection of supported semipermeable membranes comprises contacting the membrane with sodium phosphate and alkyl or alkylaryl sulfonates.
Inventors
- 👤 R Stana
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 03:23
CPC Classifications
B; B01; B01D; B01D67/00; B01D67/0081; B01D67/0088; B01D61/00; B01D61/02; B01D61/025; B01D71/00; B01D71/06; B01D71/08; B01D71/12
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
31 words
The method of claim 1, wherein the semipermeable membrane is supported in a reverse osmosis apparatus and feed liquid contacts the membrane, said detergent additive being added to the feed liquid.
Claim 2
Dependent Claim
33 words
The method of claim 2, wherein the membrane is a cellulose ester membrane and the detergent additive is added in the ratio of between about 60-500 parts additive per million parts feed liquid.
Claim 3
Dependent Claim
28 words
The method of claim 2, wherein the sulfonate is selected from the group of sulfonates having the formula: CnH2n 1-SO3Na, CnH2n 1-(C6H4)-SO3Na and mixtures thereof, where n 5-18.
Claim 4
Dependent Claim
22 words
The method of claim 4, wherein sodium phosphate comprises 40-90 wt.% of the additive and sulfonates comprise 10-50 wt.% of the additive.
Claim 5
Dependent Claim
25 words
The method of claim 4, wherein the membrane is a modified cellulose acetate membrane supported by a support made of bonded, resin coated filler particles.
Claim 6
Dependent Claim
18 words
The method of claim 4, wherein the phosphate is selected from the group consisting of Na3PO4 and Na5P3O10.
Claim 7
Dependent Claim
15 words
The method of claim 4, wherein the detergent is added to the feed liquid once.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-03-19 | 1976-09-18 | 1977-03-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-03-19 | 1980-09-18 | 1981-03-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-03-19 | 1984-09-18 | 1985-03-20 | $7700.00 | Window Closed / Lapsed |