US3617569A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Removal of phosphate from waste water
Assignee: Dow Chemical Co
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Filing: 1970-07-31
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Granted: 1971-11-02
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Expires: 1990-07-31
Abstract
Abstract Phosphates are removed from an aqueous stream by a two-stage precipitation process whereby the bulk of the phosphates are first precipitated by addition of a soluble aluminum, calcium or iron salt and phosphates still remaining in solution are then precipitated by addition of a soluble lanthanide metal salt or other such salt. Separation of the precipitated phosphates is facilitated by use of a water-soluble organic anionic polyelectrolyte flocculating agent such as a partially hydrolyzed polyacrylamide.
Inventors
- 👤 Stacy L Daniels
- 👤 Daniel G Parker
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 03:41
CPC Classifications
C; C02; C02F; C02F1/00; C02F1/52; C02F1/5236; Y; Y10; Y10S; Y10S210/00; Y10S210/902; Y10S210/906
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
29 words
The process of claim 1 wherein the primary precipitant is added in a quantity of two-four equivalents and the secondary precipitant is added in a quantity of one-two equivalents.
Claim 2
Dependent Claim
11 words
The process of claim 1 wherein the primary precipitant is aluminum.
Claim 3
Dependent Claim
11 words
The process of claim 1 wherein the primary precipitant is iron.
Claim 4
Dependent Claim
13 words
The process of claim 1 wherein the secondary precipitant is a lanthanide metal.
Claim 5
Dependent Claim
12 words
The process of claim 5 wherein the lanthanide metal is predominantly lanthanum.
Claim 6
Dependent Claim
24 words
The process of claim 1 wherein the phosphate precipitate separation is preceded by addition to the stream of an anionic water-soluble polymeric polyelectrolYte flocculant.
Claim 7
Dependent Claim
58 words
The process of claim 7 wherein the polyelectrolyte is a copolymer or a corresponding partly hydrolyzed polyacrylamide or polymethacrylamide of which the molecular structure consists essentially of 20- 50 mole percent of acrylic acid or methacrylic acid units and 80- 50 percent of acrylamide or methacrylamide units and has an average molecular weight of at least 2 million.
Claim 8
Dependent Claim
16 words
The process of claim 1 wherein the aqueous stream contains a significant concentration of bicarbonate ion.
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) | 1974-11-01 | 1975-05-03 | 1975-11-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-11-01 | 1979-05-03 | 1979-11-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-11-01 | 1983-05-03 | 1983-11-02 | $7700.00 | Window Closed / Lapsed |