JPH046291A - Method for recovering silver - Google Patents

Abstract

PURPOSE:To prevent the throwing away of a silver ion-contg. liquid and to make effective utilization of silver by circulating the whole treating liquid obtd. by treating a photographic processing liquid in an electrolytic cell to a treating tank before the electrodeposition of the whole silver ions at the time of supplying the photographic processing liquid in the treating tank to the electrolytic cell and recovering the silver. CONSTITUTION:The silver ions are reduced on a three-dimensional cathode 5 and are deposited as metal silver on the cathode 6 when the fixing soln in a fixing tank contg. the silver ions is supplied as the electrolyte through a supply pipe 11 to an electrolytic cell body 1. These silver ions are suspended in the electrolyte or deposited on the base of a diaphragm 2. The fixing soln is electrolyzed until the soln. is taken through a take-out pipe 12. The correlative relation between the stagnation time thereof and the decrease in the concn. of the silver ions is previously measured and the fixing soln. is supplied at a prescribed supply rate to the cell body 1. The concn. of the silver ions in the fixing soln. taken through the take-out pipe 12 is prevented from attaining the concn. at which silver sulfide is not formed or below in this way and the exertion of the fixing soln on the adverse influence on a photosensitive material is prevented in the fixing stage where the fixing soln is circulated and supplied.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a method for recovering silver from a solution containing silver ions by electrolysis, and more particularly, it relates to a method for recovering silver from a solution containing silver ions, and more specifically to a method for recovering silver from a solution containing silver ions, and more specifically, for recovering silver from a solution containing silver ions. After supplying a bleach-fixing solution or the like from a fixing tank or a bleach-fixing tank to a silver recovery electrolytic tank, and recovering the silver and ions by electrolytic reaction in the electrolytic tank, substantially all of the photographs in the electrolytic tank are removed. This invention relates to a second method for recovering silver from a photographic processing solution without producing silver sulfide or the like by so-called in-line processing by circulating the processing solution through the fixing tank or the like.

(Prior Art) After imagewise exposure, a photosensitive material is processed through the processing steps of color development, bleach-fixing, washing and/or stabilization, for example in paper photosensitive material processing.

Such photographic processing steps include a color development step, a bleaching step, a bleach-fixing step, a fixing step, a stabilizing step, a washing step, etc., and each step is carried out in a separate processing tank. In the processing solution, there are silver ions that dissolve quickly, such as in the emulsion of a photosensitive material, and the processing time increases.
Accordingly, the silver ion concentration gradually increases. In particular, photographic processing is a so-called heterogeneous reaction between silver halogenide in a light-sensitive material and a processing solution, and the various processing chemicals in the processing solution move through the gelatin film, causing a reaction and producing by-products. The treatment is carried out under conditions such that the particles move through the gelatin film and diffuse into the processing solution. Therefore, if a large amount of reaction by-products are present in the processing solution, it will affect the photographic processing performance. By replenishing the solution, or by withdrawing or replacing the deteriorated treatment solution, or by connecting electrolytic equipment for the purpose of silver component recovery, the silver in the treatment solution is removed by an electrolytic reaction in the electrolytic tank of the electrolysis equipment. The mainstream is to use various methods to collect and remove ions.

(Problems to be Solved by the Invention) According to the electrolytic recovery method described above, it is possible to recover silver components with considerable efficiency, but in silver recovery using the electrolytic method, the amount of F4E S deposited increases as the electrolysis time increases. Therefore, the seismic intensity decreases due to the silver ions in the photographic processing solution.3 Photographic processing solutions contain thiosulfate ions in addition to silver ions, and silver ions).
When the electrolysis of the photographic processing solution whose temperature has decreased by 1 degree is continued, silver sulfide begins to form due to the reaction between silver ions and the thiosulfate ions. The formation of silver sulfide in the photographic processing solution must be avoided since it has an adverse effect on the photosensitive material. The critical concentration of silver ions for silver sulfide production is approximately 0.5 to Ig/i
1! In conventional electrolytic silver recovery, when the silver ion concentration approaches this value, electrolysis is stopped and the photographic processing solution is discarded to prevent silver sulfide from forming in the photographic processing solution.

However, it is undesirable to dispose of photographic processing solutions containing silver for environmental and economical reasons, and a method for avoiding the disposal of silver is desired.

(Object of the Invention) The present invention provides for, when silver ions are recovered from a photographic processing solution by electrolysis, the photographic processing solution containing reduced ion concentration is circulated into the photographic processing tank without being disposed of, and the silver ions are contained in the photographic processing solution. Photographic processing that prevents the waste of photographic processing solutions and makes effective use of expensive silver, and also prevents the formation of silver sulfide due to the reaction of low-concentration ions and thiosulfate ions, thereby suppressing the negative effects on photosensitive materials. The purpose of the present invention is to provide a method for recovering silver through liquid filtration.

(Means for Solving the Problems) The present invention connects a photographic processing tank and an electrolytic tank for silver recovery, and transfers a photographic processing solution containing silver ions in the photographic processing tank to the electrolytic tank for silver recovery. In the method of supplying, electrodepositing and recovering silver in the electrolytic bath, substantially all of the photographic processing solution treated in the electrolytic bath is circulated to the photographic processing bath before all silver ions are electrodeposited. This silver recovery method is characterized by the following.

The present invention will be explained in detail below.

The present invention connects a photographic processing tank such as a constant S tank and an electrolytic cell for silver recovery, supplies a photographic processing solution with an increased root ion concentration in the photographic processing tank to the electrolytic cell, and performs a normal silver recovery electrolytic reaction. The present invention is characterized in that the photographic processing solution, in which the silver ion concentration has decreased as the electrolysis time elapses, is circulated to the photographic processing tank without being discarded.

The types of photographic processing solutions to which the present invention is applied are not particularly limited; A bleach-fix solution, a stabilizing solution, etc. can be used, but it is preferable to use a bleach-fixing solution, a fixing solution, a bleach-fix solution, a stabilizing solution, etc. with a high silver ion concentration.

The silver ion concentration in the fixing solution in normal photographic processing is 5 to 6.
g/x, and this silver ion concentration is 0.5 g/7
! Below this, the silver ions produce silver sulfide through an electrolytic reaction with thiosulfate ions in the photographic processing solution. Therefore, in the present invention, the silver concentration in the photographic processing solution is preferably within a range of 0.5 g'/l or more by adjusting the electrolytic conditions such as electrolysis time, electrolytic current, supply and circulation speed of the photographic processing solution, etc. Electrolysis is performed and the photographic processing solution is circulated through the photographic processing bath before the silver ion concentration falls below this range. In the present invention, since substantially all of the photographic processing solution is circulated, there is no need to recover all the silver ions in an electrolytic bath, thereby preventing the adverse effects of silver sulfide on photosensitive materials. Prioritize.

The silver recovery device used in the method of the present invention usually includes one or more developing tanks, bleaching tanks, and fixing tanks (or bleach-fixing tanks).
, an electrolytic cell for silver recovery may be installed in close proximity to a photographic processing tank in which a stabilizing tank and a washing tank are integrated, and the electrolytic tank may be connected to any of the photographic processing tanks. preferable. The electrolytic cell may be connected to any of the photographic processing tanks. For example, when using a photographic processing tank having a plurality of fixing tanks, the plurality of electrolytic cells may be connected to all or part of the fixing tank. Can be connected.

The supply of the photographic processing solution to the electrolytic bath and the circulation to the photographic processing bath can be carried out by a one-time method in which the photographic processing solution is circulated between the electrolytic bath and the photographic processing bath at a constant rate, or a fixed amount of the photographic processing solution. It is possible to adopt any of the Pano-Sen type methods in which the photographic processing solution is supplied to the electrolytic tank at once and electrolyzed for a certain period of time, and then the photographic processing solution is circulated to the photographic processing tank at once.

When two fixer tanks are connected, a portion of the fixer in the ankle tank is supplied to the electrolytic tank, and the silver ions of the fixer are added to the electrolyte in the electrolytic tank. 'e Preferably: M
g ,,' Electrolysis is carried out in a range that does not exceed 1 f to deposit silver ions as metal silver on the surface of the electrolytic cell, and also to suspend the particles in the cathode chamber with fine particles or to deposit them in the cathode chamber. It is collected by settling on the bottom plate. Silver io]・' concentration is the above value, that is, 0.5 g/I! It is necessary to circulate the fixing solution into the fixing tank when it approaches 1g, ''e, and it is necessary to understand the change in silver ion concentration over time. The residence time in the electrolytic cell is approximately proportional to the electrolytic current value, but in the case of the -vortex type, the residence time is determined by the supply speed of the photographic processing solution.
In the case of the Huff equation, the residence time is equal to the electrolysis time.

Therefore, in the case of one-time processing, the relationship between the supply rate of the preliminary photographic processing solution, the electrolytic current value, and the silver ion concentration of the photographic processing solution taken out of the electrolytic cell is measured, and the photograph taken out from the electrolytic cell is measured. Either the photographic processing solution is supplied to the electrolytic bath so that the silver and ion concentration in the processing solution reaches the desired value, or the silver ion concentration taken out from the electrolytic bath is measured over time and if it is higher than the desired value. The supply rate can be lowered, and if it is low, the supply rate can be increased to bring it closer to the desired value.

In the case of Hatch 2 processing, the relationship between electrolysis time and silver ion concentration is measured in advance while other electrolytic conditions are kept constant, and after a predetermined period of time, the photographic processing solution in the electrolytic bath is taken out and circulated into the photographic processing bath. Alternatively, the silver ion concentration of the photographic processing solution in the electrolytic bath is measured over time, and when the concentration reaches a predetermined value, the photographic processing solution in the electrolytic bath is taken out and circulated to the photographic processing bath. I can do it.

The electrolytic cell that can be used in the present invention is not particularly limited, and any conventional silver recovery electrolytic cell can be used; however, in the case of vortex processing, a three-dimensional electrode type electrolytic cell with a large electrode area is used. In the case of hatch-2 treatment, it is preferable to use a relatively large electrolytic cell using plate-shaped, perforated plate-shaped, etc. electrodes that can increase the processing capacity.

Even if a chair-type electrolytic cell is used, it is preferable to use an electrode with a large surface area as the cathode on which silver is deposited. carbon-based materials such as activated carbon, graphite, carbon fiber, etc., having the same shape, metal materials such as copper, stainless steel, iron, titanium, etc., and metal materials coated with precious metals. It is desirable to use three-dimensional electrodes, where the materials etc. are closely selected.

However, it is also possible to use rod-shaped, plate-shaped, and porous electrodes that are used in conventional Ho-Nox type (rotating cathode type) silver recovery electrolytic cells.

The counter electrode, that is, the anode, is not particularly limited, but it is desirable that it has a shape and arrangement that allows smooth transfer of current between it and the cathode. In the case of an electrolytic cell containing a cylindrical three-dimensional cathode, it is desirable that the anode be cylindrical to surround the three-dimensional electrode and mesh-shaped to ensure smooth flow of the electrolyte. As for the material, graphite material, carbon material, platinum group metal oxide coated titanium material (dimensionally stable electrode), platinum coated titanium material, Ni-Nokel material, etc. can be used.

In addition, in the silver recovery electrolytic reaction, hydrogen gas and oxygen gas are frequently generated, and if these gases circulate together with the photographic processing solution from the electrolytic tank to the photographic processing tank, there is a risk that the composition of the photographic processing solution in the photographic processing tank will change. There is. For example, when oxygen gas is dissolved in a photographic processing solution, sulfite ions in the photographic processing solution may be oxidized and consumed. To prevent this, it is desirable to install a gas separation means in the circulation line from the electrolytic cell to the photographic processing bath.

Furthermore, it is desirable to install a filtration means in the circulation line from the electrolytic cell to the photographic processing tank in order to remove impurities caused by circulation of the photographic processing solution or impurities mixed in the photographic processing tank during photographic processing.

Further, in the method of the present invention, the photographic processing tank and the electrolytic tank are connected, and the connection is usually made by piping made of an electrically conductive material. Therefore, the leakage current generated in the electrolytic bath may flow into the photographic processing bath through the piping, causing unnecessary reactions in the photographic processing solution, or causing damage to components such as the heater. Therefore, in the present invention, it is desirable to install means for extracting the leakage current outside the system. As an example of such means, a member having higher conductivity than the photographic processing solution may be placed in a pipe connecting the electrolytic bath and the photographic processing bath or in the electrolytic bath such that one end of the member is in contact with the photographic processing solution, so that the anode and cathode are facing each other. Either connect the other end to the ground and dissipate the leakage current to the ground, or connect the other end to a capacitor and use the leakage current to charge the capacitor. Although there are indirect means for dissipating heat, it is preferable to adopt the former method of direct grounding for ease of installation and operation.

The electrolytic cell that can be used in the present invention and the silver recovery method using the electrolytic cell will be illustrated below with reference to the accompanying drawings, but these are not intended to limit the present invention.

Figure 1 is a vertical cross-sectional view showing an example of a monopolar electrolytic cell that can be used in the present invention, which uses a fibrous cathode as a three-dimensional electrode constituent material and is used for silver recovery. FIG. 2 is a schematic diagram showing a state in which an electrolytic cell and a photographic processing cell are connected.

A cylindrical electrolytic cell body 1 made of vinyl chloride resin or the like has a diaphragm 2 such as a cylindrical ion exchange membrane with a bottom located inside it, which separates a cathode chamber 3 in the center and a donut-shaped area around it. It is divided into an anode chamber 4. The donut-shaped anode chamber 4 accommodates a donut-shaped anode 5 located between the inner wall of the main body 1 and the outer surface of the diaphragm 2 and made of a carbonaceous material or a platinum group oxide-coated titanium material.

A three-dimensional cathode 6 formed of felt-like carbon fiber or the like into a cylindrical shape is accommodated in the diaphragm 2, and the three-dimensional cathode 6
includes a base piece 7 in the center and a pair of side pieces 8 that branch laterally and are bent downward near the base end of the base piece 7.
A current is supplied by a power feeding cathode 10 in which a pointed viscous tip engaging portion 9 is formed through the enlarged diameter stepped portions at the lower ends of the base piece 7 and side pieces 8. .

An electrolytic solution supply pipe 11 is provided at the upper left of the cathode chamber 3 of the electrolytic cell body 1, and an electrolytic solution extraction pipe 12 is provided in contact with the electrolyte near the diaphragm 2 on the right side of the cathode chamber. is set up.

As shown in Figure 2-2, this electrolytic cell main body 1 consists of two color developing tanks (CD), one bleaching tank (13L>2 fixing tanks (FiX), and three washing tanks). one each connected to each of the two fixing tanks of the photographic processing tank consisting of;
The fixing solution in the fixing tank can be configured to supply the fixing solution to the electrolytic cell main body and perform a one-time process.

When the fixing solution in the fixing tank containing silver ions is supplied to the electrolytic cell main body 1 from the pump 13 through the electrolyte supply pipe 11 with the electrolyte, the ions are reduced on the three-dimensional cathode 6. Metallic silver is deposited on the three-dimensional cathode 6, suspended in the electrolytic solution, or deposited on the bottom surface of the diaphragm 2. The fixing solution, which is an electrolytic solution, is supplied from the electrolytic solution supply pipe 11 and is electrolyzed until it is taken out from the electrolytic solution extraction pipe 12.The correlation between this residence time and the decrease in silver ion concentration is measured in advance and a predetermined value is determined. When the fixing solution is supplied to the electrolytic cell main body 1 at a supply rate of There is no possibility that the photosensitive material will be adversely affected during the fixing process.

In addition, in an electrolytic cell for silver recovery, it is necessary to take out the metallic silver that is electrodeposited on the cathode and floats or accumulates in the cathode chamber out of the tank, but in the electrolytic cell shown in Figure 1-2, the electricity is stopped. rear,
When the power feeding cathode 10 is pulled upward and taken out from the main body 1, the three engaging portions 9 at the tips of the power feeding cathode 10 engage with the inside of the three-dimensional cathode 6, and together with the power feeding cathode 10. The two-dimensional cathode 6 is also taken out of the tank. Then, a substitute three-dimensional cathode or the three-dimensional cathode 6 is cleaned to remove the precipitated silver, and the three-dimensional cathode is reengaged with the power supply cathode 10, as shown in FIG. It can be assembled into an electrolytic cell. Therefore, when the electrolytic cell shown in FIG. 1 is used, there is no need to disassemble the entire electrolytic cell to recover silver as in the conventional case.

FIG. 3 is a longitudinal cross-sectional view showing another example of a monopolar electrolytic cell that can be used in the present invention using a bead-like substance as a three-dimensional electrode constituent material, and this electrolytic cell is similar to the electrolytic cell shown in FIG. 1. Similarly, it can be connected to any photographic processing tank.

A bottomed cylindrical electrolytic cell main body 21 houses along its inner wall a donut-shaped anode 22 made of a carbonaceous material, a nickel material, or the like. On the inner circumferential side of the donut-shaped anode 22, a cage-like body 23 made of synthetic resin or the like is installed, which has a cylindrical shape with a bottom, has a relatively fine mesh, and does not allow the metal silver to be deposited to pass through. Predetermined 2 of the upper edge of the body 23
A semicircular old capital 24 is placed between the locations. The layered body 23 divides the electrolytic cell body 21 into a cathode chamber 25 located inside the cage body 23 and an anode chamber 26 outside.

A three-dimensional cathode 27, which is a large number of small-diameter fine particles made of a conductive material such as a carbonaceous material, is housed inside the dish-shaped body 23. A current is supplied through the shaped body 23, and the current is further supplied to a power feeding cathode 28 suspended from slightly below the center of the old capital 24 of the cage shaped body 23.

Similarly, when a photographic processing solution containing negative ions is supplied to this electrolytic cell, the silver ions in the photographic processing solution are reduced on the three-dimensional cathode 27 and deposited as metallic silver on the three-dimensional cathode 27. Alternatively, it may float in the electrolytic solution or be deposited on the bottom surface of the cage-like body 23. In the case of batch type processing, after a predetermined electrolysis time has elapsed, the electricity supply is stopped, the former capital 24 is pulled upward, the criminal body 23 is taken out, and the layered body 2 is removed.
3 together with the three-dimensional cathode 27, and if necessary, the three-dimensional cathode 27 is replaced and reinstalled at a predetermined position in the electrolytic cell body 21 to resume silver recovery.

(Example) Next, an example regarding silver recovery treatment from a fixer by the method of the present invention will be described, but the present invention is not limited to this example.

The electrolytic cell shown in FIG. 1 was arranged as shown in FIG. 2 to recover silver from the fixing solution.

The electrolytic cell body is made of vinyl chloride resin and has a bottomed cylindrical shape with an inner diameter of 100 mm and a depth of 150 mm, and a mesh-like mesh with an outer diameter of 98 mm, an inner diameter of 96 mm, and a height of 140 mm is placed along the inner wall of the electrolytic cell body. A donut-shaped anode made of titanium material coated with palladium oxide was installed. Inside the donut-shaped anode, there is an outer diameter of 90 mm.
A bottomed cylindrical diaphragm made of sintered polypropylene fiber with a height of 130 fl and a thickness of 3 nm was installed. Inside the diaphragm, a three-dimensional cathode made of felt-like carbon fiber molded into a cylindrical shape and having a diameter of 84 cm, a height of 120 mm, and an aperture of 65% was housed. A titanium power supply cathode having three hook-shaped tip retaining parts was connected to the upper surface of the three-dimensional cathode by each time the tip retaining parts entered the three-dimensional cathode.

A fixing running liquid having the following composition was supplied into this electrolytic cell body without changing the supply speed, and the electrolytic voltage was 2.2V.
Silver was recovered by a one-time process under the electrolytic conditions of 15 A of electrolytic current, and the silver ion concentration and silver sulfide production amount in the electrolyte extraction tube at each supply rate were investigated. As silver sulfide was produced, the surface of the cathode changed from silvery white to black, and the amount produced was confirmed by the color change. The results are summarized in Table 1.

(Composition of fixer running liquid) Ammonium thiosulfate Anhydrous bisulfite) I) Sodium ram metasulfite EDTA-2Na Sodium carbonate I ion H2O0g/I! 18g//+ 3g/i 0.8 g / J 14g/1 5.63 g / +2 7.4 Table 1 As is clear from Table 1, the silver ion concentration in the electrolyte extraction tube is 0.5g# As described above, it has been found that silver sulfide is not produced when silver is recovered while circulating the photographic processing solution at a relatively high speed.

Example 2 The electrolytic cell main body of Example 1 was connected to a fixing tank S of a photographic processing tank, and a fixing running liquid having the same composition as that of Example 1 was added to the fixing tank so that silver ions); 0.7g/A
The electrolytic cell main body S: was supplied and circulated to the fixing tank so that the electrolytic cell main body S: The sulfite concentration in the fixing solution circulated to the fixing tank was measured with and without a gas separation device installed between the electrolytic tank and the fixing tank.

The sulfite concentration in the fixer after gas separation is 17.
f3 g /β, and the sulfite concentration without gas separation was 14.1 g/6. This result shows that the oxidative consumption of sulfite ions was suppressed by gas separation, that is, by separating and removing oxygen gas from the fixing solution.

(Effects of the Invention) According to the present invention, when recovering silver by supplying a photographic processing solution containing silver ions in a photographic processing tank to an electrolytic tank, before all silver ions are electrodeposited, This is a method in which substantially all of the processed photographic processing solution is circulated to the photographic processing solution (Claim 1).

A photographic processing solution contains thiosulfate ions in addition to silver ions, and when a photographic processing solution containing low fmm silver ions is electrolyzed, the electrolysis of thiosulfate ions takes precedence over the electrolysis of silver ions, and silver sulfide is produced. Since silver sulfide has an adverse effect on photosensitive materials, it is necessary to avoid its formation as much as possible, and in the present invention, the photographic processing solution after electrolysis is circulated to the photographic processing bath before silver sulfide is formed. There are some ions that are not recovered in the electrolytic cell, but
Fi! Since the ion is circulated to the photographic processing tank, there is no problem of environmental pollution, and no economic loss is caused, making it an extremely effective silver recovery method.

Silver sulfide is produced at a silver ion concentration of 0.5g/7! Silver sulfide generation in the photographic processing solution can be prevented by setting the silver ion concentration of the photographic processing solution, which is the electrolytic solution in the electrolytic bath, to be circulated to the photographic processing tank before it reaches the above concentration. (Claim 2)

Hydrogen and oxygen gases are often generated in the silver recovery electrolytic reaction, but when these gases circulate together with the photographic processing solution from the electrolytic tank to the photographic processing tank, a change in the composition of the photographic processing solution in the photographic processing tank occurs. There is a risk of In particular, oxygen generated by water electrolysis often causes acid depletion of sulfite in photographic processing solutions such as fixing solutions, thereby adversely affecting its preservation. To prevent this, for example, from the electrolytic tank to the photographic processing tank.
Preferably, a gas separation means is installed in the circulation line to perform gas separation of the photographic processing liquid from which silver has been recovered, and then the photographic processing liquid is circulated to the photographic processing tank (Claim 3).

Furthermore, in order to remove impurities due to circulation of the photographic processing solution or impurities mixed in the photographic processing tank during photographic processing, a filtration means is installed in the circulation line from the electrolytic tank to the photographic processing tank, and after filtration, the photographic processing is carried out. It should be possible to circulate it to the tank (Claim 4).

In normal electrolysis, leakage current inevitably occurs in the electrolytic cell, and the leakage current flows into the photographic processing tank unit through piping, etc., and causes unnecessary reactions in the photographic processing solution, and the current leaks through parts such as heaters. Therefore, in the present invention, it is desirable to install a means for extracting the leakage current from the system (claim 5), and the means S prevents unnecessary current wastage and unnecessary side reactions. It is possible to prevent damage to the parts and the like.

[Brief explanation of the drawing]

Figure 1 shows the present invention applied to silver recovery using a fibrous cathode as a three-dimensional electrode structure. FIG. 3 is a schematic diagram showing the state of connection between the electrolytic cell and the photographic processing cell, and FIG. 3 is a longitudinal sectional view showing another example of the monopolar electrolytic cell that can be used in the present invention. 11 ・ 13 ・ 21 ・ 25 ・ 27 ・ ... Electrolyte supply pipe pump / electrolytic cell body 22 ... Anode / cage-like body 24 ... Old capital / cathode room 26 ... Harvest room / three-dimensional cathode 28. - Cathode electrolyte extraction tube for power supply 12 - Electrolytic cell main body - Cathode chamber 4 - Anode 6 - Base piece 8 - Engagement part 10 - 2... Diaphragm - Anode chamber - Three-dimensional Cathode/side piece...Cathode for power supply Figure 2

Claims (5)

[Claims] (1) A photographic processing tank and a silver recovery electrolytic tank are connected, and a photographic processing solution containing silver ions in the photographic processing tank is supplied to the silver recovery electrolytic tank to deposit silver in the electrolytic tank. A method for recovering silver, characterized in that substantially all of the photographic processing solution processed in the electrolytic bath is circulated to the photographic processing bath before all silver ions are electrodeposited. (2) Claim 1 in which the photographic processing solution in the electrolytic cell is circulated to the photographic processing tank before the silver ion concentration decreases to 0.5 g/l.
Silver recovery method described in. (3) After gas separation of the photographic processing solution from which silver was recovered,
Claim 1 or 2, wherein the photographic processing solution is circulated to a photographic processing tank.
Silver recovery method described in. (4) The silver recovery method according to any one of claims 1 to 3, wherein after filtering the photographic processing liquid from which the silver has been recovered, the photographic processing liquid is circulated to a photographic processing tank. (5) The back part of the electrode where the anode and cathode in the electrolytic cell do not face each other and/or
5. The silver recovery method according to claim 1, wherein a member having higher conductivity than the photographic processing solution is installed in the inlet/outlet pipe of the electrolytic cell so that one end thereof can be grounded.