US3725265A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Purification of waste water
Assignee: WR Grace and Co Conn
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Filing: 1971-01-22
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Granted: 1973-04-03
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Expires: 1991-01-22
Abstract
Abstract A MULTI-STAGE LIMING PROCESS IS DESCRIBED WHICH PURIFIES WASTE WATER BY CONTROLLING THE PH OF THE WASTE WATER, E.G., AS FROM A PHOSPHATE FERTILIZER PLANT, AND THEREBY PERMITTING SELECTIVE PRECIPITATION OF IMPURITIES IN THE WASTE WATER AND THEIR RECOVERY AS USEFUL BY-PRODUCTS OF THE PROCESS IN ONE EMBODIMENT OF THE INVENTION THE MAIN PRODUCT OF THE FIRST STAGE IS A LOW SILICA CALCIUM FLUORIDE, AND THE MAIN PRODUCT OF THE SECOND STAGE IS A LOW FLUORINE DICALCIUM PHOSPHATE. IN ANOTHER EMBODIMENT OF THE INVENTION THE MAIN PRODUCT OF THE FIRST STAGE IS LOW IN PHOSPHATE CONTENT THEREBY ENHANCING THE VALUE OF THERE BYPRODUCTT, LOW SILICA CALCIUM FLUORIDE.
Inventors
- 👤 C Legal
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 08:36
CPC Classifications
C; C02; C02F; C02F1/00; C02F1/52; C02F1/5236; C02F1/66; C02F2101/00; C02F2101/10; C02F2101/12; C02F2101/14; Y; Y10; Y10S; Y10S210/00; Y10S210/902; Y10S210/906; Y10S210/915
Claims Analysis
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References Cited (Backward Citations)
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-04-02 | 1976-10-02 | 1977-04-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-04-02 | 1980-10-02 | 1981-04-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-04-02 | 1984-10-02 | 1985-04-03 | $7700.00 | Window Closed / Lapsed |