US3901777A - Recovery of silver from used photographic solutions - Google Patents

Recovery of silver from used photographic solutions Download PDF

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Publication number
US3901777A
US3901777A US480828A US48082874A US3901777A US 3901777 A US3901777 A US 3901777A US 480828 A US480828 A US 480828A US 48082874 A US48082874 A US 48082874A US 3901777 A US3901777 A US 3901777A
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United States
Prior art keywords
silver
pump
solution
cell
waste
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Expired - Lifetime
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US480828A
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English (en)
Inventor
James Sidney Bentley
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Photographic Silver Recovery Ltd
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Photographic Silver Recovery Ltd
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Filing date
Publication date
Application filed by Photographic Silver Recovery Ltd filed Critical Photographic Silver Recovery Ltd
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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C7/00—Constructional parts, or assemblies thereof, of cells; Servicing or operating of cells
    • C25C7/06—Operating or servicing

Definitions

  • ABSTRACT In an intermittently-operating electrolytic cell for the recovery of silver from used photographic bleach-fix solution, the cathode assembly and the solution are automatically separated when the plating current is switched off
  • the emptying pump is stopped by a cell bottom level switch; and a filling pump is started by a top level switch of the buffer tank, which also starts the plating cell and the metered feed, the filling pump being stopped by a top level switch of the cell.
  • the cathode assembly is selfdraining.
  • an auxiliary tank is installed upstream of the silver recovery machine to receive the sil ver waste solution from the film processing equipment or other source, a pump operating at a constant flow rate delivers waste solution from this auxiliary tank to the silver recovery machine, the silver recovery machine is supplied with plating current set at an appropriately chosen constant level, and the pump and electrical current supply are operated intermittently in substantial time coincidence so that the pump is always feeding when the recovery machine is operating to plate silver on the cathode and whenever the pump is not operating the plating current is removed.
  • the solution in the auxiliary tank has a substantially fixed silver concentration.
  • the metering pump when pumping, delivers this solution at a constant flow rate into the recovery unit and thus the flow conditions obtaining in the recovery unit, during the periods when it is actually in operation, are always the same in that a constant flow of solution enters with a constant silver concentration. This enables a fixed current amperage to be selected appropriate to this particular silver concentration and the problems associated with varying silver concentrations and a more or less arbitrarily selected current value disappear.
  • a combined Bleach Fix Solution now extensively used to process colour print paper can be de-silvered and prepared for re-use by the system disclosed in said US. Pat. No. 3,715,29l.
  • the Ferric EDTA complex in the solution gives rise to the difficulty that it softens and re-dissolves the silver back from the cathode into the solution when the plating current is switched off.
  • the plating bath may be fed, by the metered flow system described in our Patent, with a constant volume of silver in solution to match a preset plating current amperage it is then important to ensure that the silver already collected on the cathode is protected from the bleach effect of the solution during shut down periods of the apparatus.
  • the cathode and the plating solution are automatically separated from one another when the plating current is switched off.
  • One way of accomplishing this is by an automatic drain and re-fill system for the plating cell which comes into operation as soon as the level of solution in the buffer tank reaches a low level switch.
  • a selfdraining cathode assembly is employed.
  • the cathode is of the multiple flat disc type, the discs being disposed horizontally on a vertical shaft driven by an electric motor above the plating tank. These flat cathode discs are now dished into a conical form so that the solution drains down to the centre. A series of holes drilled at the lowest level of each disc allows the surplus solution from each disc to drain off to the bottom of the tank leaving the cathode silver surface free of solution.
  • the self-draining assembly can be raised vertically, by electro-mechanical jacks or similar means, clear of the plating bath and lowered again each time the plating current is switched off and subsequently switched on.
  • FIG. 1 is a general diagram of a silver recovery plant
  • FIGS. 2 and 3 are a diagrammatic cross-sectional elevation and plan of the cathode assembly of the recovery cell.
  • the silver recovery cell or plating tank 1 l equipped with an anode and a self-draining cathode assembly is preceded by a buffer or store tank 12, which receives the used photgraphic solution to be processed and from which the solution is pumped to the recovery cell intermittently by a metering pump 13, the flow rate of the pump being chosen to match the plating current employed as explained in our prior patent.
  • the buffer tank 12 is provided with top and bottom level switches A and D; the recovery cell 11, similarly has two further level switches B and E.
  • a cell emptying pump and delivery line 14 is provided for pumping solution from the recovery cell 11 back to the buffer tank 12, and a filling pump and delivery line for returning the solution from the buffer tank to the recovery cell.
  • the unit is on stand-by, with the recovery cell initially empty, the plating current switched off and all three pumps idle.
  • the buffer tank 12 fills with used photographic solution until the top level switch A is reached. Operation of this switch starts the metering pump 13 and the filling pump 15 and switches on the plating current.
  • the recovery cell 11 then fills rapidly until the level of the switch B at the top of this cell is reached, whereupon the filling pump 15 is switched off but the metering pump remains on. At this time the level in the buffer tank will have fallen to the store level indicated at C. With the metering pump operating, plating continues until the level in the buffer tank 12 has fallen to the bottom level switch D.
  • the metering pump and the plating current are then switched off and the cell emptying pump 14 is switched on.
  • the cell 11 rapidly empties until the bottom level switch E of the cell is reached, at which point the pump 14 is stopped and the cathode in the cell is dry.
  • the level in the buffer tank 12 will then have risen to the standby level indicated at F and the unit remains on stand-by until the level switch A is again reached.
  • air break arrangements are provided in the cell emptying and filling lines at 16 and 17.
  • FIGS. 2 and 3 show the self-draining cathode assembly.
  • the cathode discs 18 are clamped at intervals up the cathode drive shaft 19 with intervening spacers 20.
  • each cathode disc is of frustoconical form with drain holes 21 near the centre.
  • the cathode discs are assembled with the smaller diameters of their frusto-conical forms lowermost, they could be inverted, the solution then draining outward over the cathode discs instead of inward.
  • a method for recovering silver from waste silver solutions, especially spent photographic processing liquids said method utilizing: an electrically operated silver recovery machine of the type which includes an electrical supply for passing electric current between two electrodes, one of which is a self-draining cathode assembly, and through waste silver solution in said machine; a feed line via which waste silver solutions having predetermined average silver concentrations are supplied for processing; an auxiliary tank arranged to receive waste silver solutions from said feed line; and a pump arranged to deliver waste silver solutions from said auxiliary tank to said silver recovery machine; said method comprising the steps of:

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Electrolytic Production Of Metals (AREA)
  • Silver Salt Photography Or Processing Solution Therefor (AREA)
US480828A 1973-06-27 1974-06-19 Recovery of silver from used photographic solutions Expired - Lifetime US3901777A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB3065073A GB1462868A (en) 1973-06-27 1973-06-27 Electrolytic recovery for silver from used photographic solutions

Publications (1)

Publication Number Publication Date
US3901777A true US3901777A (en) 1975-08-26

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ID=10310965

Family Applications (1)

Application Number Title Priority Date Filing Date
US480828A Expired - Lifetime US3901777A (en) 1973-06-27 1974-06-19 Recovery of silver from used photographic solutions

Country Status (8)

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US (1) US3901777A (it)
JP (1) JPS5741555B2 (it)
CA (1) CA1061284A (it)
DE (1) DE2429288A1 (it)
FR (1) FR2235211B2 (it)
GB (1) GB1462868A (it)
IT (1) IT1054173B (it)
SE (1) SE7408402L (it)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4561957A (en) * 1984-06-11 1985-12-31 Palazzolo James C Electrolytic silver recovery system
US4802961A (en) * 1987-12-23 1989-02-07 Woog Manfred J Silver removal apparatus and method
US5685962A (en) * 1994-12-21 1997-11-11 Eastman Kodak Company Apparatus for silver recovery
US6074536A (en) * 1997-01-31 2000-06-13 Agfa-Gevaert N.V. Electroyltic cell and method for removing silver from silver-containing aqueous liquids
US20020134674A1 (en) * 2000-06-20 2002-09-26 Andrews Craig C. Electrochemical apparatus with retractable electrode

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2615839A (en) * 1948-04-12 1952-10-28 Henry O Willier Recovery of precious metals from photographic baths
US3330755A (en) * 1962-08-14 1967-07-11 Electro Cell Corp Electrolytic apparatus
US3616332A (en) * 1969-12-17 1971-10-26 Texas Instruments Inc Process for recovering silver from scrap materials and electrolyte composition for use therein
US3705716A (en) * 1971-07-09 1972-12-12 Eastman Kodak Co Monitoring silver recovery
US3715291A (en) * 1969-09-11 1973-02-06 Photographic Silver Recovery Method of recovering silver from waste silver solutions

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3342718A (en) * 1964-01-21 1967-09-19 William M Adams Apparatus for the recovery of silver from used photographic fixing solutions by electrolysis
US3458425A (en) * 1967-01-09 1969-07-29 Charles I Tolle Cathode structure for electrolytic apparatus

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2615839A (en) * 1948-04-12 1952-10-28 Henry O Willier Recovery of precious metals from photographic baths
US3330755A (en) * 1962-08-14 1967-07-11 Electro Cell Corp Electrolytic apparatus
US3715291A (en) * 1969-09-11 1973-02-06 Photographic Silver Recovery Method of recovering silver from waste silver solutions
US3616332A (en) * 1969-12-17 1971-10-26 Texas Instruments Inc Process for recovering silver from scrap materials and electrolyte composition for use therein
US3705716A (en) * 1971-07-09 1972-12-12 Eastman Kodak Co Monitoring silver recovery

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4561957A (en) * 1984-06-11 1985-12-31 Palazzolo James C Electrolytic silver recovery system
US4802961A (en) * 1987-12-23 1989-02-07 Woog Manfred J Silver removal apparatus and method
US5685962A (en) * 1994-12-21 1997-11-11 Eastman Kodak Company Apparatus for silver recovery
US6074536A (en) * 1997-01-31 2000-06-13 Agfa-Gevaert N.V. Electroyltic cell and method for removing silver from silver-containing aqueous liquids
US20020134674A1 (en) * 2000-06-20 2002-09-26 Andrews Craig C. Electrochemical apparatus with retractable electrode

Also Published As

Publication number Publication date
FR2235211B2 (it) 1978-06-02
DE2429288A1 (de) 1975-01-16
FR2235211A2 (it) 1975-01-24
AU6986874A (en) 1975-12-11
JPS5068910A (it) 1975-06-09
SE7408402L (it) 1974-12-30
IT1054173B (it) 1981-11-10
GB1462868A (en) 1977-01-26
JPS5741555B2 (it) 1982-09-03
CA1061284A (en) 1979-08-28

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