US4008077A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Rejuvenation of waste silver-laden solutions
Assignee: Individual
•
Filing: 1975-12-24
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Granted: 1977-02-15
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Expires: 1995-12-24
Abstract
Abstract A method is provided for recovering metallic silver from used silver-laden solutions, such as spent photographic fix, stop baths, stabilizers, electrolytic fix tailings, and waste silver-plating drag out and rinse solutions. The silver-laden solutions are treated with mechanically worked narrow aluminum foil strips, threads or chaff, substantially completely covered with a few microns thick imperfect layer of aluminum oxide. The resulting silver-free solution may then be chelated with a suitable chelating agent to provide a rejuvenated solution, which may be repeatedly used and restored. The method provides high silver recovery efficiency, and little maintenance, while providing the capability or repetitive use of various solutions employed in photographic development, where silver is obtained.
Inventors
- 👤 Richard A. Wallace
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 17:58
CPC Classifications
C; C22; C22B; C22B34/00; C22B34/30; C22B34/32; C22B11/00; C22B11/04; C22B11/042; C22B11/046; C22B3/00; C22B3/20; C22B3/26; C22B3/32; C22B3/42; C22B3/44; C22B3/46; C22B7/00; C22B7/006; Y; Y02; Y02P; Y02P10/00; Y02P10/20
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
68 words
A method for recovering silver metal from spent silver-laden solutions which comprises: contacting said spent silver-laden solution with a chelating agent and finely divided mechanically worked aluminum coated with an imperfect aluminum oxide coating, which results in an induction period of at least one minute, when said solution is first contacted with said aluminum, whereby finely divided silver metal is formed; and recovering the finely divided silver metal.
Claim 2
Independent Claim
68 words
A method for recovering silver metal from spent silver-laden solutions which comprises: contacting said spent silver-laden solution with a chelating agent and finely divided mechanically worked aluminum coated with an imperfect aluminum oxide coating, which results in an induction period of at least one minute, when said solution is first contacted with said aluminum, whereby finely divided silver metal is formed; and recovering the finely divided silver metal.
Claim 3
Dependent Claim
16 words
A method according to claim 1, wherein said aluminum is in the form of aluminum chaff.
Claim 4
Dependent Claim
13 words
A method according to claim 2, wherein said chelating agent is a citrate.
Claim 5
Dependent Claim
16 words
A method according to claim 1, wherein said aluminum is in the form of aluminum gauze.
Claim 6
Dependent Claim
13 words
A method according to claim 1, wherein said chelating agent is a citrate.
Claim 7
Independent Claim
99 words
A method for recovering silver metal from a spent silver-laden photographic fix solution which comprises: contacting said spent photographic fix solution with finely divided mechanically worked aluminum, having a large length to thickness ratio and coated with an imperfect aluminum oxide coating so as to provide an induction period of at least about one minute when said solution and aluminum are first contacted, and citrate, whereby finely divided silver metal is formed and aluminum ion is formed which is chelated by said citrate; and recovering the finely divided silver metal and the substantially silver free rejuvenated photographic fix solution.
Claim 8
Independent Claim
99 words
A method for recovering silver metal from a spent silver-laden photographic fix solution which comprises: contacting said spent photographic fix solution with finely divided mechanically worked aluminum, having a large length to thickness ratio and coated with an imperfect aluminum oxide coating so as to provide an induction period of at least about one minute when said solution and aluminum are first contacted, and citrate, whereby finely divided silver metal is formed and aluminum ion is formed which is chelated by said citrate; and recovering the finely divided silver metal and the substantially silver free rejuvenated photographic fix solution.
Claim 9
Dependent Claim
24 words
A method according to claim 6, wherein the amount of citrate is sufficient to provide a concentration of from about 1 to 30 gms/l.
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) | 1980-02-15 | 1980-08-16 | 1981-02-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-02-15 | 1984-08-16 | 1985-02-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-02-15 | 1988-08-16 | 1989-02-15 | $7700.00 | Window Closed / Lapsed |