US3982932A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Recovery of silver from gelatinous photographic wastes
Assignee: Eastman Kodak Co
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Filing: 1972-08-22
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Granted: 1976-09-28
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Expires: 1992-08-22
Abstract
Abstract Silver is recovered from photographic waste liquids containing emulsified silver, silver compounds, and gelatin by reacting therewith a proteolytic enzyme while the reactants are maintained in an alkaline condition. Then the reactants are acidified to a pH of 4.2 or less by introducing an acid such as HCl or H 2 SO 4 . Precipitation of gelatin-bound silver and silver compounds occurs upon acidification, and the precipitate is allowed to settle out in a settling tank. Supernatant liquid is removed from the top, neutralized and sent to sewer. Settled sludge is removed from the bottom and silver recovered, as by incineration. The operation can be conducted either batch-wise or continuously.
Inventors
- 👤 Matyas Korosi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 02:01
CPC Classifications
C; C22; C22B; C22B3/00; C22B3/18; C22B11/00; C22B11/04; C22B11/042; C22B11/046; Y; Y02; Y02P; Y02P10/00; Y02P10/20; Y10; Y10S; Y10S423/00; Y10S423/09; Y10S423/17
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
119 words
A process for recovering silver in the form of silver metal or compounds from waste wash waters of emulsion manufacture comprising: mixing with said wash waters a proteolytic enzyme endopeptidase which is a bacterial enzyme prepared from Bacillus subtillis and which is further characterized by the ability to react with gelatin to produce a peptide, maintaining said wash waters at an alkaline pH during reaction of said enzyme therewith; introducing acid into said wash waters in sufficient amount to develop an acid pH corresponding to the isoelectric point thereby to effect the precipitation of silver metal or compounds and forming a supernatant liquid, and separating a concentrate of silver metal or compounds and said supernatant liquid from one another.
Claim 2
Dependent Claim
119 words
A process for recovering silver in the form of silver metal or compounds from waste wash waters of emulsion manufacture comprising: mixing with said wash waters a proteolytic enzyme endopeptidase which is a bacterial enzyme prepared from Bacillus subtillis and which is further characterized by the ability to react with gelatin to produce a peptide, maintaining said wash waters at an alkaline pH during reaction of said enzyme therewith; introducing acid into said wash waters in sufficient amount to develop an acid pH corresponding to the isoelectric point thereby to effect the precipitation of silver metal or compounds and forming a supernatant liquid, and separating a concentrate of silver metal or compounds and said supernatant liquid from one another.
Claim 3
Dependent Claim
26 words
A process in accordance with claim 1 wherein said acid is introduced in sufficient amount to develop a pH of 4.2 to 3.5 in said liquid.
Claim 4
Dependent Claim
18 words
A process in accordance with claim 1 wherein said acid is HCl or H 2 SO 4 .
Claim 5
Dependent Claim
34 words
A process in accordance with claim 1, also comprising adding alkaline material to said supernatant liquid after said separating step in sufficient amount to neutralize acid therein, and then disposing of said supernatant liquid.
Claim 6
Dependent Claim
29 words
A process in accordance with claim 1, also comprising heating said liquid and maintaining the temperature thereof between about 48°C and about 52°C during reaction of said enzyme therewith.
Claim 7
Dependent Claim
12 words
A process in accordance with claim 1, conducted as a batch operation.
Claim 8
Dependent Claim
56 words
A process in accordance with claim 1 conducted as a continuous operation by introducing said enzyme, and said alkali into a flowing stream of said liquid, passing said flowing stream through an elongated reaction zone and completing the enzyme reaction therein, acidifying said flowing stream, and passing the acidified flowing stream through an elongated precipitation zone.
Claim 9
Dependent Claim
14 words
A process according to claim 1 wherein the pH is adjusted to about 3.5.
Claim 10
Dependent Claim
17 words
A process according to claim 1 wherein said alkaline pH is maintained by aqueous NaOH or KOH.
References Cited (Backward Citations)
US3748123A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1979-09-28 | 1980-03-29 | 1980-09-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-09-28 | 1984-03-29 | 1984-09-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-09-28 | 1988-03-29 | 1988-09-28 | $7700.00 | Window Closed / Lapsed |