Agfa Gevaert Nv

Agfa-gevaert

Agva-gevaert N. V.

Werner J Van De Wynckel

Frank P Michiels

Benedictus J Jansen

Benny Jansen

Dirk F De Ruijter

Patrick Albert Mertens

Paul Smet

Guy Damen

Fernand I Ketels

Michiels Frank

An apparatus is disclosed for electrolytic desilvering of photographic processing solutions, more particularly fixing solutions or bleach-fixing solutions, comprising an electrolysis unit equiped with a monitoring system comprising a cathode, an anode and a reference electrode, characterized in that said reference electrode is a pH sensitive electrode. The desilvering is preferably performed under potentiostatic conditions. Whe using a pH sensitive reference electrode the cathodic plating potential is automatically corrected for pH changes. A preferred pH sensitive electrode is a glass electrode.

PH sensitive reference electrode in electrolytic desilvering

An apparatus for de-silvering silver-containing solutions comprises an electrolytic cell (10) having an anode (20), a cathode (30) and a reference electrode (45) positioned adjacent the cathode (30), and electrical power supply control means (41) for controlling the supply of electrical power to the anode (20) and the cathode (30). Operation of the cell (10) is controlled potentiostatically while the current exceeds a certain threshold value and the current is controlled galvanostatically at that threshold (minimum) value in circumstances in which the potentiostatic control would result in a current below the threshold value. To this end, the power supply control means (41) includes means (60) for adjusting the cathode potential and control means (70) linked to said adjustment means (60) for controlling operation of the cell potentiostatically at a selected cathode potential, means for monitoring the current drawn through the cell during such potentiostatic control and for comparing such current with a threshold current, and means for controlling the cell galvanostatically at such threshold current value, means for switching from potentiostatic to galvanostatic control in response to cell current dropping below said threshold value, means for periodically re-establishing said selected cathode potential, and means for reverting from galvanostatic to said potentiostatic control in response to a cell current above said threshold value when said selected cathode potential is re-established.

Process and apparatus for desilvering a silver-containing solution

The apparatus, such as a photographic sheet material processing apparatus, comprises a plurality of operating components selected from output operating components such as a pump (22), a solenoid (30), a heater (25), an electrolysis cell (54), a fan (92), and a drive motor (96), and input operating components, such as a liquid level sensor (24). Operatively linked to these components is a CPU (100), containing information concerning a desired operating sequence for the apparatus, in the form of functional instructions independent of the characteristics of the operating components. Information concerning characteristics of each component is stored in separate memory means (122, 124, . . . etc.). Means (122, 124, . . . etc.) are provided for converting the functional instructions into physical instructions to operate the operating components. The operating components can easily be replaced during servicing without the need for re-programming of the CPU, even if a component is replaced by another having different characteristics.

Multi-component apparatus with improved servicing characteristic

A method for processing exposed silver-based photographic material comprises passing the exposed material through a bath of developer liquid and subsequently through a bath of fixer liquid. Silver from used fixer liquid is recovered by electrolysis. The fractional image exposure of exposed material to be processed in a coming period and the amount-of silver recovered by electrolysis in a preceding period are measured. The used fixer liquid is periodically regenerated by the addition of fresh fixer thereto. The quantity of fresh fixer to be added is calculated as a function of the measured fractional image exposure and as a function of the measured amount of recovered silver. The quality of the fixer is thereby maintained at an optimum level while keeping the quantity of fresh fixer which is used to a minimum.

Method for processing exposed silver-based photographic material

An apparatus for desilvering silver-containing solutions comprises an electrolytic cell (10) having an anode (20), a cathode (30) and a reference electrode (45) positioned adjacent the cathode (30), and electrical power supply control means (41) for controlling the supply of electrical power to the anode (20) and the cathode (30). The power supply control means (41) includes means (60) for adjusting the cathode potential and control means (70) linked to said adjustment means (60) to reduce the cathode potential, at least periodically, as the desilvering process continues. The process leads to better silver adhesion on the cathode occurs, while maintaining good desilvering levels in the solution, and cathode poisoning is minimised.

A silver-containing solution is de-silvered in an electrolytic cell having an anode and a cathode. The diffusion limitation current density of the electrolytic cell is estimated by measuring a current flow there-through and silver is deposited on the cathode at a de-silvering current density which is lower than the diffusion limitation current density.

Process for de-silvering of a silver-containing solution

An apparatus for de-silvering a silver-containing solution, comprises a plurality of electrolysis cells (10, S1, S2) each having an anode (20, 120, 220) and a cathode (30, 130, 230). A master cell (10) further comprises a reference electrode (45). The remaining cell or cells constitute slave cells (S1, S2). Control means (41) adjust the cathode potential applied to the slave cells (S1, S2) in response to the current flow (I.sub.M) through the master cell (10). The apparatus is particularly suitable for de-silvering large volumes of silver-containing solution, without the use of high currents.

Apparatus and method for de-silvering a silver-containing solution

A silver recovery device (30) is described for removing silver from a silver-containing solution. The device (30) comprises an ion-exchange resin bed (34) and a pump (62) for directing the solution through the resin bed (34). The pump (62) is positioned downstream of the resin bed (34) and the resin bed (34) is held within a retaining space (36) of variable dimensions. Higher liquid flow rates are thereby achievable, without fluidization of the resin.

Silver recovery device and process

An apparatus for the electrolytic recovery of silver from solutions containing silver is described. The apparatus comprises an electrolytic cell, an anode positioned within the cell, a reference electrode positioned within the cell, and a removable cathode positioned within the cell. The cathode has an inner face directed towards the anode and an outer face directed towards the reference electrode. The apparatus includes means for restraining the deposition of silver on the outer face of the cathode. The risk of incorrect potentials being sensed by the reference electrode are thereby reduced or avoided. The tendency for side reactions to occur is also reduced.

Apparatus for the electrolytic recovery of silver from solutions

Silver is recovered from solutions containing the same, e.g. photographic processing solutions, in an electrolytic cell including an anode, a removable cathode and electrical connectors therefore on the exterior of the cell. The removable cathode is circular in configuration and encircles the anode. On the interior of the cell, electrical contact is made around the upper end of the cathode by means of an annular contact surface providing a large area of contact and minimizing the risk of occurrence of a corrosive connection. The upper end of the cathode is shaped for deformation, preferably in the form of castellations, and is clampingly pressed against the contact surface by a frusto-conical extension of the lid of the cell. The lid fits in threadwise engagement within the opening to the cell through which the cathode can be removed. As the lid is threaded into the cell opening, the frusto-conical extension thereof bears against the deformable cathode end portion and clamps the same against the contact surface. In this arrangement, the contact surface is situated above the level of the electrolyte in the cell so as to be protected against corrosion by the electrolyte.

Apparatus for the electrolytic recovery of silver

An electrode for use in an electrolytic cell is disclosed, comprising a generally flat sheet (50) of flexible material having at least one electrically conductive surface. Upper and lower securing means are provided each comprising a tongue (55a,b) formed on one side edge (53) of the sheet (50) and a slot (56a,b) associated with an opposite side edge (54) of the sheet (50). The tongues and slots co-operate to enable the sheet (50) to be folded into and secured in an open frusto-conical configuration. This arrangement gives ease of removal from an electrolytic cell after use and advantages of requiring less storage and transport space in a flat configuration.

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Mortsel, Belgium

Werner J Van De Wynckel