JPH04298288A - Treatment of cyanide and metal-containing solution - Google Patents

Abstract

PURPOSE:To provide the new method which decomposes the cyanide ions in a cyanide ion- and metal ion-contg. soln. and more particularly a waste plating soln. and recovers metals with single operation. CONSTITUTION:The ion- and metal ion-contg. soln. is supplied to an electrolytic cell (1), where the above-mentioned cyanide ions are oxidation decomposed by an anode (12) and the above-mentioned metal ions are reduced and are deposited as metals on a cathode (17). The electrolytic cell (1) to be used is either of a diaphragm type electrolytic cell segmented to an anode chamber and a cathode chamber by a porous diaphragm (18) or a non-diaphragm type electrolytic cell which is not segmented to both chambers by the diaphragm (18) so that an electrolyte comes into sufficient contact with both electrodes.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for decomposing and recovering cyanide and metals in a solution, particularly in a plating waste solution, in a single operation using an electrolytic reaction.

0002

BACKGROUND OF THE INVENTION Conventionally, attempts have been made to treat waste liquids containing cyanide ions and metal ions, particularly plating waste liquids, to decompose the cyanide ions or recover metals. For metal recovery from such solutions,
There are substitution reduction methods using metals, reduction methods by adding a reducing agent, etc., and both methods are methods for recovering metal ions by reducing them to metals using generated hydrogen. For example, when metal recovery is performed by neutralization by adding a reducing agent, it is often necessary to filter the waste liquid that contains cyanide ions, which is not only dangerous, but also requires calcination treatment of the filtration residue to recover the pure metal. The disadvantage is that it must be collected. In addition, attempts have been made to recover precious metals using electrolytic reactions, but when recovering metals from waste liquid using methods other than electrolysis, the concentration of the waste liquid is generally high and it contains waste organic matter that is difficult to handle. It is difficult to perform normal treatment operations, and the waste organic matter cannot be decomposed and is often discarded as is. In addition, the electrolytic method is attracting attention as an effective method for recovering metals because it does not use chemicals, which reduces costs and avoids residual reagents.

However, metal recovery using conventional electrolytic methods involves leading the waste liquid into the cathode chamber of an electrolytic cell, which is divided into an anode chamber and a cathode chamber by a diaphragm such as an ion exchange membrane that allows only ions to pass through but not the electrolyte. The waste liquid (electrolyte) remains in the cathode chamber and is discharged outside the tank after metal recovery, so only metal recovery is performed in the electrolytic cell. As mentioned above, in addition to the metals to be recovered, the waste liquid often contains highly toxic cyanide ions, and these cyanide ions are removed by alkali, sodium hypochlorite, chlorine gas, etc. before or after supplying the waste liquid to the electrolytic tank. The waste liquid is removed from the waste liquid by a separate treatment in which metals are recovered and cyanide ions are decomposed, and the waste liquid is discharged. Furthermore, when conventional plate-shaped or porous cathodes are used to recover metals from waste liquid containing cyanide ions, the current density cannot be made sufficiently small.
There is a risk that a relatively large amount of hydrogen will be generated and react with cyanide ions in the waste liquid to generate hydrogen cyanide. Therefore, in waste liquid treatment using conventional electrolytic methods, it is necessary to perform electrolytic treatment for metal recovery and treatment for cyanide ion decomposition separately, which not only takes time and makes the work dangerous, but also There are disadvantages in that the cost of the added chemicals is high and the remaining chemicals need to be disposed of.

0004

OBJECTS OF THE INVENTION The present invention provides electrolytic decomposition of cyanide ions and electrolytic recovery of metals in a solution containing cyanide ions and metal ions using a single electrolytic cell, that is, cyanide ion decomposition and metal recovery. The purpose of the present invention is to provide a method that can simultaneously perform the following electrolytically.

[0005]

[Means for Solving the Problems] The present invention supplies a solution containing cyanide ions and metal ions to an electrolytic cell equipped with an anode and a cathode, oxidizes and decomposes the cyanide ions at the anode, and reduces the metal ions. This is a method for treating a solution containing cyanide ions and metals, characterized in that cyanide ions are precipitated as metals on a cathode, and cyanide ion decomposition and metal recovery are performed in a single operation.

The present invention will be explained in detail below. In the method of the present invention, the inside of the electrolytic cell is divided into an anode chamber and a cathode chamber by a porous diaphragm that allows the electrolyte to flow, without dividing the inside of the electrolytic cell by a diaphragm, or by using a porous diaphragm through which an electrolytic solution can flow. By bringing the solution into contact with both the anode and cathode of the electrolytic cell, the metal ions in the electrolyte are deposited as metal on the cathode, and the cyanide ions are decomposed at the anode, and the cyanide ions in the solution are decomposed in one pass operation. It is characterized by being able to perform decomposition and metal recovery at the same time. The method of the present invention is directed to the treatment of solutions containing cyanide ions and metal ions, particularly noble metal ions such as gold, platinum, palladium, etc., and such solutions are often plating waste solutions.

The electrolytic cell that can be used in the method of the present invention is not particularly limited, and either a monopolar electrolytic cell or a bipolar electrolytic cell may be used. Further, a diaphragm-type electrolytic cell may be used in which the inside of the electrolytic cell is divided into an anode chamber and a cathode chamber using a diaphragm, or a diaphragm-less electrolytic cell may be used in which the electrolytic cell is not divided into bipolar chambers using a diaphragm. However, when using a diaphragm type electrolytic cell, the diaphragm needs to be a porous diaphragm through which the electrolyte can flow, and an ion exchange membrane that substantially completely blocks the flow of the electrolyte is used. It is not possible. As a specific diaphragm, it is preferable to use a neutral diaphragm such as a filter cloth, a woven cloth, a vinyl chloride resin or plastic net, a punch plate, or an unglazed plate.

As the anode and the cathode, for example, a dimensionally stable electrode made of a platinum group metal oxide-coated titanium material, a platinum-plated titanium material electrode, a lead dioxide-coated electrode, etc., and an electrode made of a nickel material, a carbon material, etc., respectively. It is possible to use a single plate-like, porous, etc. electrode, or it is also possible to use a type of electrode in which a carbon material is placed in an electric field and polarized into an anode and a cathode. However, it is desirable that the material of the cathode on which metal precipitation occurs is fibrous carbon having a large surface area. By using fibrous carbon with a large surface area, the current density can be reduced to a minute value, thereby making it possible to suppress the amount of hydrogen generated to the minimum amount required for metal ion reduction. This can be assumed to be because the length of each fiber of fibrous carbon is sufficiently long so that there is no potential gradient within the electrode, the potential is the same in every part of the electrode, and almost the entire surface of the electrode undergoes an electrode reaction. On the other hand, using porous materials will increase the surface area, but with such porous materials, only the surface contributes to electrolysis, and the inside does not, so there is no point in increasing the surface area. many. This seems to be because, due to the potential difference within the electrode, only the surface close to the counter electrode functions as a substantial electrolytic surface. Note that the anode is preferably porous in order to improve the flow of the solution.

[0009] When fibrous carbon is used as a cathode, its current density becomes extremely small, thereby dramatically improving current efficiency. For example, when precious metals in waste liquid are deposited on a cathode by electrolysis and recovered, the concentration of the precious metals is 10 to 1000.
mg/liter, and if a plate electrode is used to reduce this to 1 mg/liter or less, the current efficiency is 1 to 1.
While it is about 0%, when the fibrous carbon is used, the current efficiency increases to about 10 to 30%. The fibrous carbon may be a commercially available one, and a felt-shaped one or a cotton-shaped one can be used as it is. Electricity may be supplied to the fibrous carbon using a current collector made of titanium, stainless steel, or the like. Note that cyanide ions are oxidatively decomposed on the anode surface, converted to carbon dioxide and nitrogen, and removed from the electrolyte, but in order to accelerate the decomposition of cyanide ions, a small amount of common salt, sodium hypochlorite, or nitrogen is added. Sodium chlorate, bleaching powder, etc. can be added to the electrolyte.

Other electrolytic conditions for the solution treatment containing cyanide ions and metal ions according to the method of the present invention are not particularly limited, and can be set within the following ranges. ■ Electrolysis temperature: Room temperature is sufficient, but electrolysis may be performed under heating. (2) Current concentration: It is preferable to set the current concentration to 0.05 A/liter or more to prevent the metal deposited on the cathode from redepositing. (2) Cathode current density: It is desirable to set the current density to 0.01 A/dm2 or less to suppress the generation of hydrogen gas at the cathode, smooth metal deposition, and prevent the generation of hydrogen cyanide. ■ Circulating fluid volume: It is desirable to set the volume to 100 ml/min or more to prevent hydrogen gas from accumulating. When using a diaphragm-type electrolytic cell, the solution containing cyanide ions and metal ions is first supplied to the cathode chamber of the electrolytic cell to precipitate metal ions, and then supplied to the anode chamber through a porous diaphragm to remove cyanide ions. Even if you try to decompose the
Conversely, after decomposing cyanide ions by supplying them to the anode chamber,
The metal may be recovered by being supplied to the cathode chamber through a porous diaphragm. When a non-diaphragm type electrolytic cell is used, a solution may be supplied to any part of the electrolytic cell, and the solution (electrolytic solution) contacts the anode and the cathode to decompose cyanide ions and recover metals.

[0011] When a solution containing cyan ions and metal ions is supplied to a diaphragm type electrolytic cell using a porous diaphragm or a diaphragmless type electrolytic cell not using a diaphragm as described above, the solution flows into the anode and cathode of the electrolytic cell. Because it comes into contact with both electrodes, cyanide ion decomposition occurs at the anode and metal recovery occurs at the cathode at the same time.Cyanide ion decomposition and metal recovery can be carried out using relatively small equipment without using chemicals that are expensive and tend to produce residue. It becomes possible to carry out the process in a single step. Moreover, even if the cyanide ion concentration or metal ion concentration changes, it can be handled by appropriately setting electrolytic conditions such as current concentration and applied voltage, and the present invention can be applied to solutions with a wide range of concentrations. .

Next, an example of a monopolar electrolytic cell that can be used in the cyanide ion decomposition and metal recovery method of the present invention will be explained based on the accompanying drawings. FIG. 1 is a partially cutaway vertical sectional view showing an example of a monopolar electrolytic cell that can be used in the method of the present invention. Reference numeral 1 denotes an electrolytic cell main body having a drain outlet 2 formed at the center of the lower surface and open at the upper end, and an electrolytic solution outlet 3 facing outward at the upper right side of the electrolytic cell main body 1. A donut-shaped connecting body 4 with a downwardly bent part connected to the inner end is fixed to the upper peripheral edge of the electrolytic cell body 1, and the peripheral edge of the connecting body 4 is fixed to the upper peripheral edge of the electrolytic cell body 1. A donut-shaped lower horizontal piece 6 of the intermediate body 5 aligned with the peripheral edge is joined. The connecting body 4 and the lower horizontal piece 6 are screwed together by a power supply screw 7 and tightened by a clamp 8 around the power supply screw 7.
A cylindrical anode 9 is electrically connected to the lower end, and the lower end of the anode 9 reaches near the bottom plate inside the electrolytic cell body 1.

A cylindrical connecting piece 10 is connected upward at the inner edge of the lower horizontal piece 6 of the intermediate body 5, and the connecting piece 1
An upper horizontal piece 11 shaped like a donut is arranged outwardly at the upper end of 0. A lid 13 whose periphery is aligned with the periphery of the horizontal piece 11 and has a through hole 12 formed in the center is joined to the upper horizontal piece 11, and the lid 13 is connected to the horizontal piece 11 and the periphery of both. It is fastened by a clamp 14. A power supply pipe 16 which also serves as electrolyte dispersion and has a large number of pores 15 bored inside the electrolytic cell body 1 passes through the central through-hole 12 of the lid 13 , and the feed pipe 16 also serves as an electrolyte dispersion tube. A cathode 17 formed into a cylindrical shape with a predetermined thickness by intertwining a large number of carbon fibers is installed around the power supply tube 16 in close contact with the cathode 17 . This cathode 17 is housed in a porous diaphragm 18 made of a bag-shaped filter cloth or the like with an open top. The diaphragm 18 is fitted to the lower end of a cylindrical auxiliary body 19 disposed in the anode 9, and the diaphragm 18 prevents the fibrous carbon constituting the cathode 17 from shorting with the anode 9. The diaphragm 18 is
Similarly, the upper end is fitted into the lower end of the auxiliary body 19 and surrounded by a bag-shaped mesh body 20, so that the diaphragm 18 and the cathode 17 are brought into close contact with each other.

The anode 9 of the electrolytic cell constructed as described above is energized from the power supply screw 7, and the cathode 17 is energized from a power supply part (not shown) connected to the power supply pipe 16 protruding from the electrolytic cell body 1. When a waste liquid containing cyan ions and metal ions, such as gold ions, is supplied from the power supply pipe 16, the waste liquid (electrolyte) permeates through the pores 15 of the power supply pipe 16 into the inside of the cathode 17 made of fibrous carbon. By the time the electrolyte reaches the outer end of the electrolyte, metal ions such as gold ions are deposited on the cathode 17 by an electrolytic reaction at the cathode 17, and the metal ion concentration in the electrolyte decreases or becomes zero. In this case, it is desirable to prevent the hydrogen generated from the cathode 17 from being used to generate hydrogen cyanide by adjusting the current concentration and the like.

This electrolytic solution further passes through the porous diaphragm 18 and reaches the anode chamber, and the cyanide ions in the electrolytic solution come into contact with the anode 9 and are oxidatively decomposed and removed from the electrolytic solution, forming metal ions. and is taken out from the electrolyte outlet 3 as a solution containing little or no cyanide ions. When cyanide ion decomposition and metal recovery are insufficient, the electrolyte taken out from the electrolyte solution outlet 3 may be supplied again to the power supply pipe 16 of the electrolytic cell to further continue cyanide ion decomposition and metal recovery. . In addition, in the method of the present invention, the electrolytic cell may be assembled so that the electrolyte passes from the anode chamber to the cathode chamber instead of from the cathode chamber to the anode chamber, and the electrolyte is supplied to the anode chamber. Cyanide ion decomposition takes place, followed by metal recovery in the cathode chamber. Furthermore, when a non-diaphragm type electrolytic cell is used, cyanide ion decomposition and metal recovery are performed simultaneously.

[0016]

EXAMPLES Examples of cyanide ion decomposition and metal recovery by the method of the present invention will be described below, but these examples are not intended to limit the present invention. Example 1 The electrolytic cell shown in FIG. 1 was used to treat a waste liquid containing cyanide ions and metal ions. Diameter 52mm and height 120mm (effective volume 52mm x 102mm)
A platinum group metal oxide-coated titanium material with a diameter of 50 mm was housed as an anode in a cylindrical electrolytic cell, and a titanium feed tube with a diameter of 10 mm was coated with fibrous carbon to a thickness of 12.5 mm to form a cathode. form, cover with a neutral filter cloth,
Furthermore, the neutral filter cloth was brought into close contact with the cathode using a plastic net. A plating waste solution with a gold ion concentration of 20.1 mg/liter and a cyanide ion concentration of 44.0 g/liter was diluted with tap water, and a commercially available gold potassium cyanide concentrate and a special grade potassium cyanide reagent were added to obtain the initial gold ion concentration. Prepare 1 liter of a solution with an initial cyanide ion concentration of 70.0 mg/liter and an initial cyanide concentration of 203.0 mg/liter to form an electrolytic solution (initial pH 11.80, initial temperature 12.0°C).
).

Using this electrolytic cell and electrolytic solution, electrolytic treatment was carried out for 90 minutes under the electrolytic conditions of 0.50 A current, 0.50 A/liter current concentration, and 1.920 liter/minute circulating fluid volume (current flow rate After 0.80AH/liter), the gold ion concentration and cyanide ion concentration in the electrolyte were measured and found to be 0.1 mg/liter and 39.0m, respectively.
g/liter, the gold recovery rate is 99.86% (gold recovery current efficiency 3.8%), and the cyanide ion decomposition rate is 81.8%.
It was 92%. pH after 90 minutes is 11.00
Met. Further electrolysis was continued, and when the energization time reached a total of 360 minutes, the energization was stopped (the energization amount was 3.49AH/
When the gold ion concentration and cyanide ion concentration in the electrolyte were measured, they were 0.0 mg/liter and 0.1 mg/liter, respectively, and the gold recovery rate was 100 mg/liter.
%, and the cyanide ion decomposition rate was 99.95%, indicating almost complete gold recovery and cyanide ion decomposition. 36
The pH after 0 minutes was 10.30. The results are summarized in Table 1. Furthermore, the relationship between the current concentration and the cyanide ion concentration in the electrolytic solution is summarized in the graph of FIG. 2, and the relationship between the current concentration and the gold ion concentration in the electrolytic solution is summarized in the graph of FIG. 3.

Example 2 Diameter: 125 mm and height: 255 mm (effective volume: 1
A dimensionally stable electrode with a diameter of 87 mm was housed as an anode in a cylindrical electrolytic cell (25 mm x 240 mm), which was approximately the same shape as Example 1 but different in size, and fibrous carbon was placed in a titanium power supply tube with a diameter of 10 mm. The same waste liquid as in Example 1, which was coated to a thickness of 15.0 mm to form a cathode, covered with a neutral filter cloth, and further adhered the neutral filter cloth to the cathode with a plastic net. Similarly, the initial gold ion concentration was 34.0 mg/liter and the initial cyanide ion concentration was 8.
Prepare 8 liters of 09.0 mg/liter solution and use it as an electrolytic solution (initial pH 12.45, initial temperature 14.0°C)
And so. Using this electrolytic cell and electrolytic solution, electrolytic current 1.
0A, current concentration 0.13A/liter and circulating fluid volume 1.
After electrolytic treatment was performed for 360 minutes under electrolytic conditions of 0.080 liters/min (current flow rate: 0.76AH/liter), the gold ion concentration and cyanide ion concentration in the electrolyte were measured and found to be 0.1 mg/liter and 91 mg/liter, respectively. .0mg
/liter, the gold recovery rate is 99.68% (gold recovery current efficiency 1.8%), and the cyanide ion decomposition rate is 88.9%.
It was 6%. pH after 360 minutes is 12.09
Met.

[0019] Electrolysis was continued for a total of 1350 electrification times.
The energization is stopped when the energization amount reaches 2.89 AH.
When the gold ion concentration and cyanide ion concentration in the electrolyte were measured, they were 0.0 mg/liter and 0.1 mg/liter, respectively, and the gold recovery rate was 10 mg/liter).
0%, the cyanide ion decomposition rate is 99.99%,
It was found that almost complete gold recovery and cyanide ion decomposition were achieved, and that it was possible to decompose high concentrations of cyanide ions. 1
The pH after 350 minutes was 11.90. The results are summarized in Table 1. Furthermore, the relationship between the current concentration and the cyanide ion concentration in the electrolytic solution is summarized in the graph of FIG. 2, and the relationship between the current concentration and the gold ion concentration in the electrolytic solution is summarized in the graph of FIG. 3.

Example 3 The same electrolytic cell as in Example 2 was used, and the initial gold ion concentration was 16.
4.0 mg/liter and initial cyanide ion concentration 44
Eight liters of a 70.0 mg/liter solution was prepared to serve as an electrolytic solution (initial pH 12.00, initial temperature 6.3° C.). Using this electrolytic cell and electrolyte, the electrolytic current is 1.0
A, current concentration 0.13 A/liter and circulating fluid volume 0.
After electrolytic treatment was performed for 360 minutes under electrolytic conditions of 93 liters/min (current flow rate: 0.77 AH/liter), the gold ion concentration and cyanide ion concentration in the electrolyte were measured and found to be 0.1 mg/liter and 3590 mg/liter, respectively. .0mg
/liter, the gold recovery rate is 99.94% (gold recovery current efficiency 8.9%), and the cyanide ion decomposition rate is 21.4%.
9%, indicating that gold can be recovered from solutions containing concentrated cyanide ions. The pH after 360 minutes was 11.55.

[0021] Electrolysis was continued for a total of 1390 hrs.
When the energization amount reaches 3.00 AH, the energization is stopped.
The gold ion concentration and cyanide ion concentration in the electrolyte were measured to be 0.1 mg/liter and 2120.0 mg/liter, respectively, with a gold recovery rate of 99.94% and a cyanide ion decomposition rate of 54%. .17%
Almost complete gold recovery was achieved, and cyanide ion decomposition was also performed. The pH after 1350 minutes was 11.90. The results are summarized in Table 1. Furthermore, the relationship between the current concentration and the cyanide ion concentration in the electrolytic solution is summarized in the graph of FIG. 2, and the relationship between the current concentration and the gold ion concentration in the electrolytic solution is summarized in the graph of FIG. 3.

Example 4 The same electrolytic cell as in Example 2 was used, and the initial gold ion concentration was 90.
．． 0mg/liter and initial cyanide ion concentration 1147
．． Eight liters of a 0 mg/liter solution was prepared to serve as an electrolytic solution (initial pH 13.89, initial temperature 5.0° C.). Using this electrolytic cell and electrolytic solution, electrolytic treatment was performed for 300 minutes under the same electrolytic conditions as in Example 3 (current flow: 0.64
AH/liter), the gold ion concentration and cyanide ion concentration in the electrolyte were measured and found to be 0.1 mg/liter each.
liter and 678.0 mg/liter, gold recovery rate is 99.89% (gold recovery current efficiency 5.9%),
The cyanide ion decomposition rate was 42.22%. 300
The pH after minutes was 13.05.

[0023] Electrolysis was continued for a total of 600 hrs.
The energization is stopped when the current reaches 1.29 AH.
The gold ion concentration and cyanide ion concentration in the electrolyte were measured to be 0.1 mg/liter and 286.0 mg/liter, respectively, with a gold recovery rate of 99.90% and a cyanide ion decomposition rate of 99.90%. The result was 75.9%, indicating that almost complete gold recovery and cyanide ion decomposition occurred, and that gold recovery and cyanide ion decomposition occurred even if the initial pH value changed significantly. The pH after 600 minutes was 12.90. The results are summarized in Table 1. Furthermore, the relationship between the current concentration and the cyanide ion concentration in the electrolytic solution is summarized in the graph of FIG. 2, and the relationship between the current concentration and the gold ion concentration in the electrolytic solution is summarized in the graph of FIG. 3.

[0024]

[Table 1]

[0025]

[Effect of the invention] The present invention supplies a solution containing cyanide ions and metal ions to an electrolytic cell in which an anode and a cathode are installed,
Treatment of cyanide and metal-containing solutions, especially plating waste liquid, characterized in that cyanide decomposition and metal recovery are performed in a single operation by oxidatively decomposing the cyanide ions at the anode and reducing the metal ions and precipitating them as metals on the cathode. A method (Claim 1). Electrolytic cells that can be used in the method of the present invention include electrolytic cells partitioned into an anode chamber and a cathode chamber by a porous diaphragm (Claim 2) and membraneless electrolytic cells (Claim 3), which are supplied to the electrolytic cell. The electrolyte solution is brought into contact with both the anode and cathode, and cyanide ions are decomposed into carbon dioxide and nitrogen at the anode.
The metal ions are reduced on the cathode and deposited as metals on the cathode. Therefore, cyanide ion decomposition and metal recovery can be performed simultaneously by supplying the solution to the electrolytic cell and performing one-pass treatment.

Furthermore, the method of the present invention allows cyanide ion decomposition and metal recovery to be carried out in a single step by electrolysis using relatively small equipment and without the use of costly and residue-prone chemicals. . However, it is of course possible to add a small amount of a chemical to promote cyanide ion decomposition. Moreover, even if the cyanide ion concentration or metal ion concentration of the treatment solution changes, it can be handled by appropriately setting electrolytic conditions such as current concentration and applied voltage, and the present invention can be applied to solutions with a wide range of concentrations. be able to. When a fibrous carbon material is used as the cathode (Claim 4), each fiber is long enough so that there is no potential gradient within the electrode, and the potential is the same at every part of the electrode, and almost the entire surface of the electrode undergoes an electrode reaction. By setting the density to a minute value, it becomes possible to suppress the amount of hydrogen generated to a minimum amount.

[Brief explanation of the drawing]

[Fig. 1] Partially broken vertical cross-sectional view showing an example of a monopolar electrolytic cell that can be used in the method of the present invention.

[Figure 2] Graph showing the relationship between current concentration and cyanide ion concentration in the electrolyte in Examples 1 to 4

[Figure 3] Graph showing the relationship between current concentration and gold ion concentration in the electrolyte in Examples 1 to 4

[Explanation of symbols]

Claims (4)

[Claims] 1. A solution containing cyanide ions and metal ions is supplied to an electrolytic cell in which an anode and a cathode are installed, and the cyanide ions are oxidized and decomposed at the anode, and the metal ions are reduced and deposited as a metal on the cathode. A method for processing cyanide and metal-containing solutions, characterized by performing cyanide ion decomposition and metal recovery in a single operation. 2. The method according to claim 1, wherein an electrolytic cell is used which is divided into an anode chamber and a cathode chamber by a porous diaphragm. 3. The method according to claim 1, wherein a membraneless electrolytic cell is used. 4. The method according to claim 1, wherein the cathode is formed of a fibrous carbon material.