US4804528A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Stripping and recovery of dichromate in electrolytic chlorate systems
Assignee: Aker Solutions Canada Inc
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Filing: 1988-01-12
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Granted: 1989-02-14
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Expires: 2008-01-12
Abstract
Abstract A process for removing dichromates from chlorate-rich solutions containing hypochlorite and dichromate ions and produced by the electrolysis of brine. The dichromate is reduced in a two-stage process by the addition of ammonia under controlled conditions of pH and temperature to a mixed di- and trivalent chromium hydroxide which is precipitated from solution and removed. The process provides an economical method of recovering chromium from electrolytically produced chlorate solutions.
Inventors
- 👤 Ian H. Warren
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 21:51
CPC Classifications
C; C01; C01B; C01B11/00; C01B11/12; C01B11/14; C01B11/145; C25; C25B; C25B1/00; C25B1/01; C25B1/24; C25B1/26; C25B1/265; C25B15/00; C25B15/08; C25B15/085; Y; Y10; Y10S; Y10S204/00; Y10S204/13; Y10S210/00; Y10S210/902; Y10S210/911; Y10S210/912; Y10S210/913
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
134 words
A process for the removal of dichromate from a solution containing chlorate, hypochlorite and dichromate ions by the reduction of the hexavalent chromium of said dichromate to mixed di- and trivalent chromium in the form of a hydroxide precipitate which process comprises effecting said reduction in two stages comprising (a) adding ammonia to said solution and treating said solution at a pH greater than 8.5 at a temperature of greater than 60° C. with said ammonia to effect production of said hydroxide precipitate; said ammonia and said hypochlorite being present in sufficiently excessive amounts to permit the production of said hydroxide precipitate; and (b) adjusting the pH of the resultant solution to below 8.5 at a temperature of greater than 40° C. to effect substantially complete precipitation of said di- and trivalent chromium hydroxide.
Claim 2
Dependent Claim
134 words
A process for the removal of dichromate from a solution containing chlorate, hypochlorite and dichromate ions by the reduction of the hexavalent chromium of said dichromate to mixed di- and trivalent chromium in the form of a hydroxide precipitate which process comprises effecting said reduction in two stages comprising (a) adding ammonia to said solution and treating said solution at a pH greater than 8.5 at a temperature of greater than 60° C. with said ammonia to effect production of said hydroxide precipitate; said ammonia and said hypochlorite being present in sufficiently excessive amounts to permit the production of said hydroxide precipitate; and (b) adjusting the pH of the resultant solution to below 8.5 at a temperature of greater than 40° C. to effect substantially complete precipitation of said di- and trivalent chromium hydroxide.
Claim 3
Dependent Claim
51 words
A process as claimed in claim 1 wherein said solution during stage (a) has a pH greater than 10.5 and a temperature selected from the range 75° C.-85° C., and during stage (b) has a pH selected from the range 6.5-7.5 and a temperature selected from the range 75° C.-85° C.
Claim 4
Dependent Claim
25 words
A process as claimed in claim 2 wherein any ammonia remaining in said solution after stage (a) is removed under vacuum prior to stage (b).
Claim 5
Dependent Claim
34 words
A process as claimed in claim 3 wherein the pH of the solution in stage (a) is adjusted by the addition of sodium hydroxide and in stage (b) by the addition of hydrochloric acid.
Claim 6
Dependent Claim
40 words
A process as claimed in any one of claims 1 to 4 wherein said solution comprising chlorate, hypochlorite and dichromate ions is a solution comprising sodium chlorate and sodium chloride produced by the electrolysis of brine in an electrolytic cell.
References Cited (Backward Citations)
SE218495C1
Cited
US3843769A
Cited
JPS5521508A
Cited
US4259297A
Cited
US4560546A
Cited
US4477318A
Cited
US4680126A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-02-14 | 1992-08-15 | 1993-02-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-02-14 | 1996-08-15 | 1997-02-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-02-14 | 2000-08-15 | 2001-02-14 | $7700.00 | Window Closed / Lapsed |