US4036715A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of recovering silver from photographic bleach-fix and concurrently regenerating the bleach-fix
Assignee: Eastman Kodak Co
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Filing: 1971-12-20
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Granted: 1977-07-19
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Expires: 1991-12-20
Abstract
Abstract An improved practical and highly efficient electrolytic method for concurrently recovering silver from photographic bleach-fix solutions which contain iron, and regenerating the bleach-fix for reuse. A substantial improvement in current efficiency at low current densities is realized by a combination of (a) adding a reductant such as sodium dithionite before electrolysis, as a reducing agent for ferric ions in the bleach-fix solution, (b) maintaining a non-oxidizing atmosphere in the cell, and (c) providing either a cation permeable membrane or a porous alundum membrane between the electrolytic cell anode and cathode, to separate a first pool of bleach-fix catholyte from a second pool of a different salt solution such as sodium carbonate as anolyte.
Inventors
- 👤 Harry C. Baden
- 👤 Charleton C. Bard
- 👤 Donald J. Brugger
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 18:10
CPC Classifications
G; G03; G03C; G03C5/00; G03C5/26; G03C5/395; G03C5/3954; C; C25; C25C; C25C1/00; C25C1/20
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
111 words
A method for electrolytically recovering silver from spent aqueous bleach-fix photographic processing solution containing ions of both silver and iron III comprising introducing into said processing solution a chemical compound characterized by the ability to reduce iron III to iron II, impressing a direct electrical current between a cathode which is immersed in a first pool of such processing solution and an anode which is immersed in a second pool of anolyte solution of a carbonate, borate phosphate or silicate, thereby plating silver onto said cathode, said first and second pools being separated from one another by non-porous cation permeable barrier or a porous barrier, and excluding air from said pools.
Claim 2
Independent Claim
111 words
A method for electrolytically recovering silver from spent aqueous bleach-fix photographic processing solution containing ions of both silver and iron III comprising introducing into said processing solution a chemical compound characterized by the ability to reduce iron III to iron II, impressing a direct electrical current between a cathode which is immersed in a first pool of such processing solution and an anode which is immersed in a second pool of anolyte solution of a carbonate, borate phosphate or silicate, thereby plating silver onto said cathode, said first and second pools being separated from one another by non-porous cation permeable barrier or a porous barrier, and excluding air from said pools.
Claim 3
Dependent Claim
15 words
A method in accordance with claim 1 wherein said anolyte solution is a carbonate solution.
Claim 4
Independent Claim
129 words
A method for electrolytically recovering silver from spent aqueous bleach-fix photographic processing solution containing ions of both silver and iron III comprising introducing into said processing solution a chemical compound characterized by the ability to reduce iron III to iron II, said chemical compound being selected from the group consisting of sodium formaldehydesulfoxylate, hydrazine, morpholine borane, dimethylamine borane, trimethylamine borane, hydroxylamine sulfate, and aminoiminomethanesulfinic acid, impressing a direct electrical current between a cathode which is immersed in a first pool of such processing solution and an anode which is immersed in a second pool of anolyte solution, thereby plating silver onto said cathode, said first and second pools being separated from one another by a non-porous cation permeable barrier or a porous barrier, and excluding air from said pools.
Claim 5
Independent Claim
129 words
A method for electrolytically recovering silver from spent aqueous bleach-fix photographic processing solution containing ions of both silver and iron III comprising introducing into said processing solution a chemical compound characterized by the ability to reduce iron III to iron II, said chemical compound being selected from the group consisting of sodium formaldehydesulfoxylate, hydrazine, morpholine borane, dimethylamine borane, trimethylamine borane, hydroxylamine sulfate, and aminoiminomethanesulfinic acid, impressing a direct electrical current between a cathode which is immersed in a first pool of such processing solution and an anode which is immersed in a second pool of anolyte solution, thereby plating silver onto said cathode, said first and second pools being separated from one another by a non-porous cation permeable barrier or a porous barrier, and excluding air from said pools.
Claim 6
Dependent Claim
14 words
A method in accordance with claim 3 wherein said chemical compound is hydroxylamine sulfate.
Claim 7
Independent Claim
125 words
A method for electrolytically recovering silver from spent aqueous bleach-fix photographic processing solution containing ions of both silver and iron III comprising introducing into said processing solution a chemical compound characterized by the ability to reduce iron III to iron II, impressing a direct electrical current between a cathode which is immersed in a first pool of such processing solution and an anode which is immersed in a second pool of anolyte solution, of a carbonate, borate, phosphate or silicate thereby plating silver onto said cathode, said first and second pools being separated from one another by a non-porous cation permeable barrier or a porous barrier, and excluding air from said pools by introducing and maintaining over said pools an atmosphere of non oxidizing gas.
Claim 8
Independent Claim
125 words
A method for electrolytically recovering silver from spent aqueous bleach-fix photographic processing solution containing ions of both silver and iron III comprising introducing into said processing solution a chemical compound characterized by the ability to reduce iron III to iron II, impressing a direct electrical current between a cathode which is immersed in a first pool of such processing solution and an anode which is immersed in a second pool of anolyte solution, of a carbonate, borate, phosphate or silicate thereby plating silver onto said cathode, said first and second pools being separated from one another by a non-porous cation permeable barrier or a porous barrier, and excluding air from said pools by introducing and maintaining over said pools an atmosphere of non oxidizing gas.
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) | 1980-07-18 | 1981-01-17 | 1981-07-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-07-18 | 1985-01-17 | 1985-07-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-07-18 | 1989-01-17 | 1989-07-19 | $7700.00 | Window Closed / Lapsed |