JPH0688276A - Method for electrolytically recovering silver - Google Patents

Abstract

PURPOSE:To inexpensively and simply recover silver from a solution containing silver component and an ion compound by electrolysis. CONSTITUTION:An electrodepositing silver containing a silver-sulfur compound is converted into an easy-soluble silver compound by fringing the electrodepositing silver containing silver-sulfur compound electrodeposited on an electrode into contact with an aq. solution containing hypochlorite ion. A solution containing a sulfite and a thiosulfate is preferably used for dissolving the easy-soluble silver compound and a bleaching fixing solution of photographic processing containing a ferric organic acid salt in addition to the sulfite and the thiosulfate is preferably used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recovering silver from a solution containing silver ions by electrolysis, and more specifically to a fixing solution or a bleach-fixing solution containing a silver component and a sulfur compound in a photographic processing step. The method of supplying a photographic processing solution from a fixing bath or a bleach-fixing bath to a silver recovery electrolytic bath, and electrolytically depositing the silver ions on the electrodes of the electrolytic bath as metallic silver or silver sulfide to recover the silver ions by an electrolytic reaction in the electrolytic bath. .

[0002]

2. Description of the Related Art A light-sensitive material is processed after imagewise exposure, for example, in processing a light-sensitive material for paper, through processing steps such as color development, bleach-fixing, washing with water and / or stabilization. Such a photographic processing step includes a color developing step, a bleaching step, a bleach-fixing step, a fixing step, a stabilizing step, a washing step and the like, and each step is performed in a separate processing tank. In the processing solution in each processing step, silver ions dissolved from the emulsion of the light-sensitive material are present, and the silver ion concentration gradually increases as the processing time elapses. In particular, photographic processing is a reaction between silver halide in a light-sensitive material and a processing solution. The reaction occurs only when various processing agents in the processing solution move in the gelatin film, and by-products move in the gelatin film. Then, it is performed under the condition that it diffuses into the processing liquid. Therefore, if a large amount of reaction by-products are present in the processing solution, it will also affect the photographic processing performance.Therefore, in particular, the processing of deteriorated processing solutions in which silver ions have accumulated in the processing solution is a new processing solution. Replenishment, or withdrawal or replacement of the deteriorated treatment liquid, or an electrolytic facility for the purpose of silver component recovery is connected to the treatment tank, and silver ions in the treatment liquid are removed by an electrolytic reaction in the electrolytic bath of the electrolytic equipment. The mainstream method is to perform electrodeposition as metallic silver or silver sulfide on the electrode and to collect and remove the electrodeposited silver component.

[0003]

Problems to be Solved by the Invention In the silver recovery by this electrolytic method, the silver component can be recovered with considerable efficiency. In particular, when a three-dimensional electrode having an enormous surface area is used as an electrode, the entire surface area of the three-dimensional electrode is used for silver recovery, so that the recovery rate is very high and silver recovery from a low-concentration silver-containing aqueous solution is possible. it can. However, in this electrolysis method, as the amount of silver recovered increases, the electrode surface is covered with electrodeposited silver, the effective surface area decreases, and further clogging occurs, so that the electrodeposition of silver ions in the solution does not occur. Therefore, in order to continue the recovery of silver, it is necessary to replace the electrode or remove the deposited silver from the electrode. As a method of dissolving or suspending silver adhering to an electrode or the like in a solution to remove it, a method of immersing the electrode in dilute nitric acid to dissolve or suspend silver as silver nitrate, and immersing the electrode in a potassium iodide solution to remove silver A method of dissolving or suspending as silver iodide, a method of dissolving in a bleach-fixing solution,
A method in which a counter electromotive force is applied to the electrode to dissolve or suspend silver is easily conceived and known. Although silver can be dissolved by the above method, as a result of studies by the present inventors, the aqueous solution to be recovered silver contains a thiosulfate salt, a sulfite salt and a photographic processing solution containing a sulfur compound such as a mercapto compound, or a waste solution thereof. In such cases, it was found that the above method could not completely remove silver from the electrode or was very time consuming. In particular, when thiosulfate which does not generate odor (nitric acid gas, iodine gas, hydrogen sulfide gas, etc.) at a low cost is dissolved in a bleach-fixing solution for photography, which is a main component for silver dissolution, 10 to 30% remain undissolved, the capacity of silver recovery deteriorates when the electrode is reused, and clogging becomes severely unusable due to repeated regeneration. Insufficient silver recovery.

[0004]

It is an object of the present invention to provide an electrolytic silver recovery method for easily and inexpensively dissolving and removing or recovering a silver component electrodeposited on an electrode when it contains a sulfur compound.

[0005]

According to the present invention, a solution containing a silver component and a sulfur compound is supplied to an electrolytic cell and the silver component is deposited as a solid silver component on an electrode of the electrolytic cell to recover silver. In the method, the solid silver component electrodeposited on the electrode is brought into contact with an aqueous solution containing hypochlorite ions.

The present invention will be described in detail below. The inventors of the present invention have found that when metallic silver is electrodeposited on the electrode, the metallic silver is easily dissolved by a general dissolution method, but solid silver compounds electrolytically deposited from a solution containing a sulfur compound are generally dissolved. In the dissolution method, a part of the solid silver compound remains undissolved or takes a very long time, which is presumed to be because the solid silver compound is a silver sulfur compound such as silver sulfide. The inventors of the present invention have conducted diligent research and confirmed that the deposited silver compound is changed and easily dissolved in the silver solution by bringing the deposited silver compound and the like into contact with an aqueous solution containing hypochlorous acid. I found it. The electrolytic bath targeted by the present invention is not particularly limited, and a developing solution, a bleaching solution, a fixing solution, a bleach-fixing solution, a stabilizing solution, a photographic processing solution such as washing water, or a solution containing other silver ions is supplied. It is possible to target any silver recovery electrolytic cell in which the silver recovery is performed and the silver component is electrodeposited on the surface of the electrode due to the silver recovery and the electrodeposition efficiency is deteriorated. It is desirable that the electrolytic bath for silver recovery uses a bleaching solution, a fixing solution, a bleach-fixing solution, a stabilizing solution and the like that often contain ions.

The structure of the electrolytic cell is not particularly limited, and an electrolytic cell having an arbitrary structure can be used. In addition to the commonly used rotary cathode type (box type) electrolytic cell, a tertiary electrode having a large electrode area can be used. It is possible to use an original electrode type electrolytic cell or a relatively large electrolytic cell which uses a plate-shaped or perforated plate-shaped electrode capable of increasing the processing capacity. Regardless of which type of electrolytic cell is used, it is preferable to use an electrode having a large surface area as a cathode on which silver is electrodeposited, and the electrode is, for example, granular, spherical, felt-like, woven cloth-like, porous block-like, etc. Carbon material such as activated carbon, graphite and carbon fiber having the same shape, metal material having the same shape such as nickel, copper, stainless steel, iron and titanium, and a material obtained by applying a noble metal coating to these metal materials. It is desirable to use three-dimensional electrodes. However, rod-shaped, plate-shaped, and porous electrodes used in the above-mentioned rotating cathode type silver recovery electrode can also be used.

The counter electrode, that is, the anode is not particularly limited, but it is desirable that the counter electrode, that is, the anode, has a shape and arrangement for smoothly transmitting and receiving an electric current to and from the cathode. For example, as an electrolytic cell, carbon is provided at the center of a cylindrical electrolytic cell body. In the case of an electrolytic cell containing a cylindrical three-dimensional cathode made of fibers, it is desirable that the anode has a cylindrical shape that surrounds the three-dimensional electrode and that the anode has a mesh shape to facilitate the flow of the electrolytic solution. As the material, a graphite material, a carbon material, a platinum group metal oxide coated titanium material (dimensional stability electrode), a platinum coated titanium material, a nickel material, or the like can be used. The electrolytic cell for silver recovery used in the method of the present invention is usually close to a photographic processing tank in which one or more developing tanks, a bleaching tank, a fixing tank (or a bleach-fixing tank), a stabilizing tank and a washing tank are integrated. It is preferable that the electrolysis tank is connected to one of the photographic processing tanks to be formed and the processing liquid or waste liquid overflowing from the processing tank is processed. The electrolytic bath may be connected to any of the processing baths of the photographic processing bath, and when a photographic processing bath having a plurality of fixing baths is used, a plurality of electrolytic baths may be provided in all or a part of the fixing bath. Can be connected. It is also possible to connect a plurality of tanks in parallel or in series for processing the waste liquid from the photographic processing tanks.

The photograph is processed, and the photographic processing solution containing silver is supplied to the electrolytic cell for silver recovery having the above-mentioned constitution to perform electrolysis.
As a method of supplying the photographic processing liquid, a one-time type in which the photographic processing liquid is supplied to the electrolytic bath at a constant speed to take out the same amount as the supply amount, and a constant amount of the photographic processing liquid is supplied to the electrolytic bath at once There is a batch system in which the photographic processing liquid is taken out of the electrolytic cell at once after electrolysis for a certain period of time, and any supply system may be used. The higher the silver ion concentration in the supplied photographic processing liquid, the larger the amount of silver ion deposited on the cathode as metallic silver or silver sulfide or other silver sulfur compound, and when the silver ion concentration decreases, the amount of electrodeposition increases. As it becomes smaller, the amount of electrodeposited silver sulfide or other silver-sulfur compound gradually increases, the cathode surface is covered with the metallic silver and the silver sulfide or other silver-sulfur compound, and clogging occurs inside the three-dimensional cathode. hand,
The electrodeposition efficiency decreases to the extent that economical operation cannot be performed. In order to continue the silver recovery, it is necessary to regenerate or replace the electrode, especially the cathode.In the method of the present invention, the electrode in which the silver component is electrodeposited is taken out in the electrolytic cell or after being removed from the electrolytic cell. It is treated with an aqueous solution containing chlorate ions to dissolve or suspend the electrodeposited silver compound or the like, and removed from the inside or the surface of the cathode.

Although the effect of hypochlorous acid in the present invention is not clear, silver sulfide or other silver sulfur compound is changed to silver chloride, silver oxide or silver hypochlorite, silver sulfate or other compound or complex. The effect of forming the However, the reason why hypochlorous acid is merely an oxidant cannot be explained because the effect of the present invention cannot be obtained with hydrogen peroxide, persulfate, percarbonate and the like, which are commonly used as oxidants.

The silver component electrodeposited on the cathode is easily converted into a silver component which is soluble in the metallic silver solution by reaction with the hypochlorite ion. As a method for dissolving metallic silver, nitric acid,
A bleaching agent that ionizes silver-dissolved components such as high-concentration iodide, bromide, and thiosulfate, such as iron chloride, ferric organic acid, dichromic acid, hydrogen peroxide, persulfate, and red blood salt Various methods such as first bleaching and then dissolving in a silver-soluble component are possible. As the organic acid ferric iron,
There are ferric ethylenediaminetetraacetic acid, ferric diethylenetriaminepentaacetic acid, ferric propylenediaminetetraacetic acid and the like. In particular, in the present invention, a photographic fixing solution containing thiosulfate and sulfite, which has a weak solubility but is excellent in terms of odor and cost, is used as a silver solution because the solubility of the precipitated silver component is greatly improved. It is advantageous to do Further, other than the method of performing the fixing treatment after the bleaching treatment, it is preferable to use a bleach-fixing solution as a fixing solution containing a bleaching agent, and in this case, silver dissolution is possible and it is very preferable.

As a solution containing the above-mentioned sulfite ion or thiosulfate ion and ferric organic acid, there is a bleach-fixing solution in the photographic processing step, and particularly in the case of silver recovery from the photographic processing solution, Since the partial bleach-fixing solution can be used as it is, the cost reduction can be achieved at low cost. Furthermore, in the case of silver recovery from a photographic processing solution, the solution in the electrolytic bath is often circulated to the photographic processing bath, and if compounds or chelating agents not used in the photographic processing bath are mixed in the electrolytic bath, the photographic processing process will be adversely affected. May occur,
The use of the aforementioned bleach-fix solution is more convenient. In the method of the present invention, it is not necessary to dissolve or suspend all the electrodeposited silver components on the electrode surface to remove them, and it may be continuously used as an electrode of a silver recovery electrolytic cell with some silver components remaining. .
Note that in the silver recovery by electrolysis, sulfur may be electrodeposited on the electrode, and it is desirable to perform the removal operation of the electrodeposited sulfur in parallel with the above silver component.

Next, the method for recovering electrodeposited silver according to the present invention will be described in detail with reference to the electrolytic cell shown in the accompanying drawings. Figure 1
It is a longitudinal cross-sectional view showing an example of a monopolar electrolytic cell to which the present invention can be applied. The bottomed cylindrical electrolytic cell body 1 formed of vinyl chloride resin or the like has a bottomed cylindrical ion exchange membrane or other diaphragm 2 located inside thereof, and a central cathode chamber 3 and a donut-shaped surrounding thereof. It is divided into the anode chamber 4 of. The doughnut-shaped anode chamber 4 accommodates a doughnut-shaped anode 5 located between the inner wall of the main body 1 and the outer surface of the diaphragm 2 and formed of a carbonaceous material or a platinum group metal oxide coated titanium material. .
The diaphragm 2 accommodates a three-dimensional cathode 6 formed of carbon fiber or the like in a felt-like columnar shape. The three-dimensional cathode 6 includes a base piece 7 in the central portion and a proximal end of the base piece 7. At a lower end of the base piece 7 and the side piece 8 with a pair of side pieces 8 branching laterally and bent downward, and having a sharpened harpoon shape through an enlarged diameter step portion. An electric current is supplied by a solid or hollow feed cathode 10 having a tip engaging portion 9. When, for example, a photographic processing solution containing silver ions is supplied to this electrolytic bath as an electrolytic solution, the silver ions are reduced on the three-dimensional cathode 6 and reacted with metallic silver or thiosulfate ions contained in the photographic processing solution. Silver sulfide is electrodeposited on the three-dimensional cathode 6, suspended in an electrolytic solution, or deposited on the bottom surface of the diaphragm 2. After a lapse of a certain time from the start of the operation, a sufficient amount of silver component is electrodeposited on the three-dimensional cathode 6 to lower the electrolysis efficiency, and it is necessary to remove the electrodeposited silver component from the three-dimensional cathode 6. Become. Even if the three-dimensional cathode 6 is removed while the electrolytic cell body 1 is housed, the silver component is removed.
May be taken out of the electrolytic cell body 1.

When the silver component is removed by taking it out of the main body 1 of the electrolytic cell, the power supply cathode 10 is pulled up and taken out from the main body 1 after the energization is stopped. The three engaging portions are respectively engaged with the inside of the three-dimensional cathode 6, and the three-dimensional cathode 6 together with the feeding cathode 10 are provided.
Is also taken out of the tank. When the three-dimensional cathode 6 on which metallic silver, silver sulfide or another silver sulfur compound is electrodeposited is treated with a solution containing hypochlorite ion, for example, an aqueous solution of sodium hypochlorite, the silver sulfur compound is converted into a readily soluble compound. To be done. When a solution containing a sulfite and a thiosulfate, for example, a bleach-fixing solution in a photographic processing step is added to this solution as a silver solution, the easily soluble compound is sufficiently dissolved or partially suspended in the silver solution and recovered. . When the silver sulfur compound remains without being oxidized by the treatment with the aqueous solution of sodium hypochlorite, the compound is not recovered because it does not react with sulfite or thiosulfate. In this case, it is desirable to add a chelating agent (organic acid ferric iron, etc.) to chelate and dissolve the above compound and recover it. Since the bleach-fixing solution in the photographic processing step contains a chelating agent such as EDTA in addition to the above-mentioned sulfite and thiosulfate, the silver-sulfur compound etc. can be efficiently recovered by using the bleach-fixing solution.

When the three-dimensional cathode 6 is treated in the electrolytic cell body 1, the photographic processing solution in the electrolytic cell body 1 is extracted and then a solution containing hypochlorite ions is added, or the electrolytic cell is used. A solution containing hypochlorite ions is added without extracting the photographic processing solution in the main body 1 to convert the silver component electrodeposited on the three-dimensional cathode 6 into soluble silver, and further a bleaching solution of the photographic processing solution. After passing the solution, the fixing solution is passed to remove the silver compound, or the bleach-fixing solution is passed to remove the silver,
The electrode can be regenerated and silver can be recovered.

FIG. 2 is a vertical cross-sectional view illustrating a silver recovery electrolytic cell with a bag-like diaphragm to which the present invention can be applied. A plate-shaped graphite anode 15 is installed close to the side wall of a box-shaped electrolytic cell 11 whose wall surface is made of an electrically insulating organic polymer material such as vinyl chloride resin, and the anode chamber 13 for accommodating the anode 15 is the above-mentioned. It is partitioned from the cathode chamber 14 by the side wall and the U-shaped diaphragm 12 in a side view. Cylindrical stainless rotating cathode in the center of the electrolytic cell 11
16 is installed, and the cathode 16 rotates by receiving the rotational force of the motor through the rotating shaft and the connecting plate. The anode chamber
A photographic processing solution containing silver ions and a sulfur compound or the like is supplied as an electrolytic solution 18 to at least one of the cathode 13 and the cathode chamber 14 by a processing solution supply pipe (not shown). The rotating cathode 16 agitates the electrolytic solution 18 in the cathode chamber 14 to promote contact between the cathode 16 and silver ions in the electrolytic solution 18. The silver ions are reduced on the cathode 16 to be deposited on the cathode 16 as metallic silver, silver sulfide particles or silver sulfur compound particles, or suspended in the cathode chamber 14 or deposited on the bottom plate of the cathode chamber 14. .
The metal silver, silver sulfide particles and silver sulfur compound particles electrodeposited on the rotating cathode 16 become easily soluble silver compounds due to hypochlorite ions, as in the case of the electrolytic cell of FIG. Then, it is dissolved in various silver solutions and collected.

FIG. 3 is a vertical cross-sectional view illustrating a bipolar electrode type three-dimensional electrode type recovery electrolytic cell to which the present invention can be applied. A cylindrical electrolytic cell body 22 having upper and lower flanges 21 is provided with a mesh-shaped power feeding cathode terminal 23 and power feeding anode terminal 24 near the upper end and the lower end, respectively. The cathode terminal 23 for applying a negative DC voltage is formed of, for example, platinum, stainless steel, titanium, nickel, copper, hastelloy, graphite, carbon material, mild steel or metal material coated with platinum group metal. The anode terminal 24 facing the cathode terminal 23 and providing a positive DC voltage is, for example, a carbon material (activated carbon, charcoal, coke,
Coal, etc.), graphite material (for example, carbon fiber, carbon cloth, graphite, etc.), carbon composite material (for example, carbon mixed with metal in powder form, etc.), activated carbon fiber non-woven fabric, or platinum, platinum, It is formed of a material supporting palladium or nickel, a dimensionally stable electrode (platinum group oxide-coated titanium material), a platinum-coated titanium material, a nickel material, a stainless material, an iron material, or the like.

A plurality of sponge-like fixed beds 25 are laminated between the two electrode terminals 23 and 24 in the illustrated example, and between the fixed beds 25 and between the fixed beds 25 and the two electrode terminals 23. , 24 are sandwiched by four porous diaphragms or spacers 26. Each fixed bed 25 is in close contact with the inner wall of the electrolytic cell body 22 and does not pass through the inside of the fixed bed 25, so that the leakage flow of the photographic processing liquid flowing between the fixed bed 25 and the side wall of the electrolytic cell body 22 is minimized. It is located in. When electricity is supplied to the above-mentioned electrolytic cell body 22 while supplying a photographic processing solution containing silver ions from below, each fixed bed 25 has its lower surface polarized negatively and its upper surface polarized positively as shown in the figure. Inner and fixed floor 25
An electric potential is generated between them, and the silver ions in the photographic processing liquid contacting the negatively polarized portion of the lower surface of the fixed bed 25 are reduced and electrodeposited as metallic silver or silver sulfide particles. Then, as in the case of FIG. 1 and FIG. 2, it is converted into a readily soluble compound by the hypochlorite ion and recovered.

[0019]

EXAMPLES Examples of silver recovery by the method of the present invention will be described below, but the examples do not limit the present invention. Example 1 First, using the electrolytic cell shown in FIG. 1, silver ions in the fixing solution used in the photographic processing step were electrodeposited as metallic silver and silver sulfide on the cathode. The electrolytic cell body is made of bottomed cylindrical vinyl chloride resin with an inner diameter of 150 mm and a depth of 150 mm, and along the inner wall of the electrolytic cell body, the outer diameter is 130 mm, the inner diameter is 125 mm, and the height is 120 mm.
A doughnut-shaped power supply anode made of the mesh-shaped titanium material coated with iridium oxide was installed. Inside the doughnut-shaped anode, a diaphragm having a bottomed cylindrical diameter made of polypropylene and having an outer diameter of 120 mm and a thickness of 3 mm was installed by fixing its peripheral portion to the bottom plate of the electrolytic cell body by welding. Inside the diaphragm, a felt-like carbon fiber was formed into a cylindrical shape with a diameter of 110 mm,
A three-dimensional cathode having a height of 120 mm and a porosity of 50% was housed. A titanium power supply cathode having three harpoon-shaped tip engaging portions was connected to the upper surface of the three-dimensional cathode by inserting the tip engaging portions into the three-dimensional cathode.

In the main body of the electrolytic cell, a fixing running solution having the following composition was diluted 200 times to prepare 200 liters of washing water waste liquid, which was supplied at a rate of 10 liters / minute, and an electrolytic current of 2 A.
When silver was recovered by a cyclic treatment under constant current controlled electrolysis conditions, the electrolysis voltage was maintained at 2.5 to 5.0 V. The silver concentration in the wash water waste solution after 1 hour from the start of electrolysis is 1 pp
It was reduced to m (the amount of silver reduction was 8 g). (Composition of fixing running solution) Ammonium thiosulfate 100 g / l Anhydrous sodium bisulfite 18 g / l Sodium metasulfite 3 g / l EDTA Ferric ammonium dihydrate 50 g / l EDTA 1 g / l Sodium carbonate 14 g / l Silver ion 8.2 g / Liter pH 7.4

After the waste water of the washing water in the electrolytic bath was extracted, the aqueous solutions shown in Table 1 were circulated for 1 hour each, and then discharged from the electrolytic bath, and a bleach-fixing solution having the following composition was further placed in the electrolytic bath. The liquid was introduced to make the liquid volume 10 liters and circulated for 3 hours. (Composition of bleach-fixing solution) EDTA Ferric ammonium dihydrate 100 g / liter EDTA 5 g / liter Ammonium thiosulfate 150 g / liter Ammonium sulfite 10 g / liter (pH adjusted to 7.4 with ammonia and acetic acid) The silver concentration in the solution was measured by the atomic absorption method, and the recovery rate was calculated by the following formula and shown in Table 1. Silver recovery rate (%) = [silver concentration (g / liter)] x 10 liters / 8g x 100%

[0022]

[Table 1]

Example 2 In the same manner as in Example 1, silver was electrodeposited from the waste water of washing water.
Next, after draining the washing water waste liquid from the electrolytic cell, two types of one, one treated with a 3% solution of sodium hypochlorite and the other untreated, were circulated with 1N nitric acid for 3 hours in the electrolytic cell to form a tertiary solution. The silver component on the former cathode was eluted. When the silver recovery rate was analyzed and calculated in the same manner as in Example 1, the recovery rate of the untreated one was 87%, whereas the recovery rate of the treated one was 100%.

[0024]

INDUSTRIAL APPLICABILITY The method of the present invention is a method for recovering silver by supplying a solution containing a silver component and a sulfur compound to an electrolytic cell, and depositing the silver component as a solid silver component on an electrode of the electrolytic cell to recover silver. The electrolytic silver recovery method is characterized in that the solid silver component electrodeposited on the electrode is brought into contact with an aqueous solution containing hypochlorite ions (claim 1). When recovering silver ions by the electrolytic method, the silver ions are electrodeposited as metallic silver, silver sulfide or other silver sulfur compound on the electrode. In order to recover the electrodeposited silver component in a reusable form, it is necessary to dissolve or suspend the electrodeposited silver component in a solution. According to the conventional nitric acid dissolution method or silver iodide method, metallic silver can be sufficiently dissolved, but it is insufficient to dissolve silver sulfur compounds such as silver sulfide and a part thereof is not dissolved, or even if all are dissolved There was a problem that it took a very long time.

In the method of the present invention, it is possible to recover an electrodeposited silver component, particularly a silver component containing a silver sulfur compound, with a high recovery efficiency in a relatively short time by using an inexpensive chemical called a solution containing hypochlorite ion. This is because the electrodeposited silver sulfur compound can be converted into a readily soluble silver compound by hypochlorite ion. The converted readily soluble silver compound is dissolved in a silver solution and recovered. It is preferable to use a solution containing a sulfite and a thiosulfate as the silver solution (Claim 2), particularly an organic acid. When a bleach-fixing solution containing a ferric salt, a thiosulfate and a sulfite is used in the photographic process, chelation with the iron salt further accelerates the dissolution of the silver compound.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing an example of a monopolar electrolytic cell to which the present invention can be applied.

FIG. 2 is a vertical cross-sectional view illustrating a silver recovery electrolytic cell with a bag-like diaphragm to which the present invention can be applied.

FIG. 3 is a vertical cross-sectional view illustrating a bipolar electrode three-dimensional electrode type recovery electrolytic cell to which the present invention can be applied.

[Explanation of symbols]

1 ... Electrolyzer main body 2 ... Diaphragm 3 ... Cathode chamber
4 ... Anode chamber 5 ... Anode 6 ... Three-dimensional cathode
7 ... Base piece 8 ... Side piece 9 ... Tip engaging part
10 ... Power supply cathode 11 ... Electrolytic cell body 12 ... Diaphragm 13 ... Anode chamber 14 ... Cathode chamber 15 ... Anode
16 ・ ・ ・ Cathode 18 ・ ・ ・ Electrolyte 21 ・ ・ ・ Flange 22
・ ・ ・ Electrolyzer body 23 ・ ・ ・ Power supply cathode terminal 24
... Anode terminal for power supply 25 ... Fixed floor 26 ...
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[Procedure amendment]

[Submission date] August 2, 1993

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

[Figure 1]

[Fig. 2]

[Figure 3]

Claims (3)

[Claims] 1. A method for recovering silver by supplying a solution containing a silver component and a sulfur compound to an electrolytic cell and depositing the silver component as a solid silver component on an electrode of the electrolytic cell to recover silver. A method for recovering electrolytic silver, which comprises bringing the solid silver component into contact with an aqueous solution containing hypochlorite ions. 2. The electrode is regenerated by bringing the silver component into contact with an aqueous solution containing hypochlorite ions and then dissolving the silver component in an aqueous solution containing at least thiosulfate or sulfite. Electrolytic silver recovery method. 3. Silver is recovered by dissolving the electrodeposited silver after treatment with an aqueous solution containing hypochlorite ions in a bleach-fixing solution containing ferric organic acid salt, thiosulfate salt and sulfite salt. The electrolytic silver recovery method according to claim 1, wherein