JPH0633288A - Electrolytic metal collecting method - Google Patents

Abstract

PURPOSE:To collect a metal from a dil. metal salt soln. in high yield in a packed-bed electrolytic metal collecting device by forming a bed packed with a mixture of conductive fiber with non-conductive fiber and applying a current to the bed to deposit the metal on the mixture surface. CONSTITUTION:A packed-bed electrolytic device provided with a plate anode 3, a plate counter cathode 2, a liq.-permeable diaphragm 4 provided away from the cathode surface and a packed bed 6 set between the diaphragm and cathode 3 is used to collect a metal. A conductive fiber (carbon fiber, fibrous activated carbon) is used as the conductive medium material forming the packed bed 6, and further, a non-conductive fiber (polyester fiber, PP fiber) is meshed with the conductive fiber to form a mixture. A metal salt soln. is circulated through an electrolytic cell 1, and a current is applied between both electrodes 2 and 3 to deposit the metal.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a metal electrowinning method for extracting these metals from metal salt solutions, particularly metal salt solutions containing valuable metals or harmful metals in dilute concentrations with relatively low electrical conductivity. It is a thing.

[0002]

2. Description of the Related Art As a device used for recovering or removing metal from a solution having a low electric conductivity containing valuable metal or harmful metal at a relatively low concentration such as a plating waste liquid or other industrial wastewater, it has been conventionally shown in FIG. Packed bed electrowinning devices as shown are known.

This device is provided with a plate-like anode 2 vertically provided in an electrolytic cell 1 and a plate-like cathode 3 provided so as to face the anode 2, and between the anode 2 and the cathode 3. The conductive medium substance 6 is filled with, for example, graphite particles or the like, and a solution to be treated is caused to flow between both electrodes to be energized so that the metal contained in the solution becomes conductive such as graphite. It is obtained by electrodeposition on the surface of the sexual medium substance 6.

In the apparatus, since the conductive medium substance 6 contacts the cathode 3 and functions as a part of the cathode during operation, a gap is formed so as not to contact the anode 2 and cause a short circuit. You need to keep it. Therefore, a diaphragm 4 is provided in the vicinity of the anode 2 so as to be separated from the surface of the anode 2 via a spacer 5 of an appropriate shape such as a lattice or spiral formed of a non-conductive substance, and the diaphragm 4 and the cathode 3 are provided. By filling the space (filling chamber) formed by the conductive medium substance 6 with the conductive medium substance 6, the conductive medium substance 6 is prevented from coming into contact with the anode 2.

Many proposals have been made for this packed bed type electrowinning apparatus so that the metal can be taken in high yield. For example, 1) according to the electrical conductivity of the aqueous solution containing the collected metal, the surface distance between the lower cathode plate and the diaphragm, which is the inlet side of the undiluted aqueous solution, is narrowed so that the target concentration of the collected metal is low. A method of efficiently performing an electrode reaction by increasing the interplanar spacing in the upper layer portion having a smaller size (Japanese Patent Laid-Open No. 62-20891), 2) a conductive non-conductive material such as a particulate non-conductive material such as plastic or ceramics. It is mixed by mixing with the cathode so as to show the same polarity as the cathode without causing the bipolar phenomenon, and by changing the length of the conductive particulate matter continuously filled between the surfaces of the cathode plate and the diaphragm. There is a method for increasing the electrode reaction area (Japanese Patent Laid-Open No. 58-130292), 3) a method for increasing the cathode surface area as much as possible, and the like.

[0006]

However, in the method of 1) above, the closer to the anode of the particulate conductive medium material, the higher the current density and the more easily the metal is electrodeposited. Since the conductive medium substances are adhered to each other by the metal as the electrodeposits and grows, the electric current easily concentrates on the portion having the low electric resistance. If such a phenomenon further progresses, the electrode layer will not function as a part of the cathode plate three-dimensionally and electrodeposition will not occur in the inner layer of the conductive medium particles or in the part close to the plate cathode. There was a problem that the initial large electrode reaction area was extremely reduced even though there were still enough voids for electrodeposition.

In the method 2), a conductive medium substance can be used more effectively as a cathode than in the method 1), but it is possible to uniformly disperse and fill non-conductive particles in the electrolytic cell. There is a problem that the stock solution for treatment may partially pass through because it is difficult. Furthermore, in the method of 3), when conductive fibers having a large surface area are used as the conductive medium substance, the conductive fibers are partially wrapped by gas due to hydrogen gas generated during electrolysis and participate in the electrode reaction. It was recognized that they would not. In this case, by setting the bulk density and packing density of the fibers to optimum values, it is possible to maintain the initial high electrolytic extraction efficiency to some extent in consideration of outgassing, but as the amount of electrodeposition increases, the same as in 1) There is a problem that the effective electrode area is extremely reduced due to the adhesion between the conductive fibers.

For this reason, the conductive medium substance conventionally filled in the electrolytic cell is replaced in a short cycle,
Alternatively, there is an inconvenience that it is necessary to perform a regeneration treatment, and the above inconvenience is more remarkable especially when the electric conductivity of the solution to be treated is low.

An object of the present invention is to eliminate the above-mentioned inconvenience in the electrowinning of metals using a packed bed metal electrowinning apparatus and to maintain a high initial electrowinning efficiency for a long time. It is an object of the present invention to provide a metal electrowinning method.

[0010]

[MEANS FOR SOLVING THE PROBLEMS] The metal electrowinning method of the present invention for achieving the above-mentioned object is a plate-shaped anode, a plate-shaped cathode provided so as to face the plate-shaped anode, and the plate-shaped anode. A liquid permeable membrane provided in the vicinity of the plate-shaped anode and isolated from the surface of the plate-like anode, and a packed bed made of a conductive medium substance provided between the plate-shaped cathode and the liquid-permeable membrane. In conducting electrowinning of metal using a packed bed electrowinning apparatus, a conductive fiber is used as a conductive medium substance forming the packed bed, and the conductive fiber is entangled with a non-conductive fiber. Characterized by filling the packed bed as a body, circulating a solution containing a sampled metal inside the electrolytic cell, and conducting electrolysis by applying an electric current between both electrodes, thereby depositing a metal on the surface of the mixture. Is.

In the present invention, the shape of the conductive fiber used as the conductive medium substance in the packed bed is 10 to 15 μm.
m is suitable, and it is desirable that the form of the mixture filler obtained by entwining this with the non-conductive fiber is felt-like.

[0012]

Next, details of the present invention and its operation will be described.

In the present invention, the conductive medium material used as the packed bed of the electrolytic cell is a mixture of conductive fibers such as carbon fibers and fibrous activated carbon with non-conductive fibers such as polyester and polypropylene. When the metal is electrodeposited on the surface of the conductive material by electrolyzing the electrolytic solution containing the collected metal by doing so,
Even if the deposited metal grows, the non-conductive fibers partially exist so that the mutual adhesion of the conductive fibers does not easily occur and the function as the three-dimensional electrode can be maintained for a long time.

Further, by using the fibrous substance as the conductive medium substance, the surface area can be increased and the porosity can be increased more than double as compared with the conventionally used particulate substance. As a result, the electrode reaction area and the metal growth space can be made large, so that the initial electrowinning efficiency can be increased, and this can be maintained for a long time.

The mixing ratio, filling amount, materials, etc. of the conductive fibers and the non-conductive fibers for advantageously achieving the advantages of the present invention are the characteristics of the solution containing the sampled metal, the electrolysis conditions based on the characteristics, etc. The optimum condition may be determined in accordance with
For example, when a solution having an electric conductivity of 2 mS / cm is electrolyzed, the mixture filler has a volume resistivity of 35.5 Ω · cm.
The mixing ratio and filling amount may be selected as follows.

The mixture of the conductive fiber and the non-conductive fiber used in the metal electrowinning method of the present invention is made by entangled each fiber and needle-punching to form a felt-like mixture. Is desirable. This is because the felt-like shape allows the uniformity of the mixture to be adjusted when the mixture is filled in the electrolytic cell, and the mixture can be filled without changing the state. The shape of the fibers used for this purpose is appropriately 10 to 15 μm in diameter. If the fiber mixture has a form other than the above, for example, a chopped form, it is difficult to uniformly fill the fiber mixture, and it is impossible to maintain the electrolytic extraction efficiency with good reproducibility.

[0017]

EXAMPLES Examples of the present invention will be described below together with comparative examples. Example 1 In the packed bed electrowinning apparatus having the shape shown in FIG. 1, the electrolytic cell was a vinyl chloride electrolytic cell having a width of 6 cm, a depth of 4 cm, and a height of 10 cm (internal method), and a plate installed in the electrolytic cell. The interplanar distance between the plate-shaped anode and the diaphragm is 0.3 cm, and the interplanar distance between the diaphragm and the plate-shaped cathode is 3 cm, and the plate-shaped anode has 5.5 × 12.0 × 0.2 cm ruthenium oxide. (T
DK), and 6.0 × 12.0 × 0.5 for the plate cathode.
cm graphite plate (manufactured by Toyo Carbon Co., Ltd.), and a 5.5 × 10.0 cm filter cloth was used for the diaphragm.

The packed bed has a diameter of 12 to 13 μm and a volume of
Specific resistivity 1.5-1.6 × 10^{− Two}Ω · cm carbon fiber
Fiber (made by Osaka Gas Co.) 44% by weight polyester fiber
And needle punched to obtain a bulk density of 0.017 g / c
m^Three, A felt-like mixture with a volume resistivity of 35.5 Ω · cm
Packed density is 0.023 g / cm^ThreeFilled with
did. The porosity of the filling material at this time was 95%.

Next, as a treating liquid, a copper pyrophosphate copper solution of 500 mg / l adjusted to have an electric conductivity of 7.8 mS / cm was used, and the solution was used as a lower liquid in the cathode chamber of the electrowinning apparatus. It is a transient treatment method in which it is supplied from the inlet at a supply rate of 0.29 l / h and discharged from the upper overflow outlet to the outside, and electrolysis is performed at room temperature of 20 ° C. with a current density of 2.0 A / dm ² for the plate electrode. Then, copper was sampled from the solution by depositing copper on the surface of the filling material.

The target lower limit of the collection efficiency at this time is 95%
The concentration of copper in the solution discharged from the overflow outlet was measured by an atomic absorption spectrophotometer, and when the copper extraction efficiency was 95% or less, the amount of copper electrodeposited by that time and the electrolytic treatment time were measured.

The results are shown in Table 1. From Table 1, the amount of copper electrodeposited until the electrolytic extraction efficiency was 95% or less was 1
It is 4.1 g, and it can be seen that the electrolytic treatment time is 130 hours.

[0022]

[Table 1] Comparative Example 1 Graphite particles of -7 to +9 mesh (JIS standard) and a volume specific resistance of 0.8 Ω · cm were used as a filler.
Electrolytic extraction of copper from copper pyrophosphate was performed under the same electrolytic conditions as in Example 1 except that the packed bed was filled with a porosity of 95%.

The results of measuring the amount of electrodeposited copper and the electrolytic treatment time in the same manner as in Example 1 are shown in Table 1. It can be seen from Table 1 that the amount of copper deposited was 1.0 g and the electrolytic treatment time was 8.2 hours. Comparative Example 2 Carbon fiber having a bulk density of 0.02 g / cm ³ and a volume specific resistance of 1.48 Ω · cm was used as a filler, and the packing density was 0.039 g.
Electrolysis of copper from copper pyrophosphate was performed under the same electrolysis conditions as in Example 1 except that the packed bed was filled at a porosity of / cm ³ and a porosity of 95%.

The results of measuring the amount of electrodeposited copper and the electrolytic treatment time in the same manner as in Example 1 are shown in Table 1. It can be seen from Table 1 that the amount of copper electrodeposited was 4.2 g and the electrolytic treatment time was 38 hours. Comparative Example 3 As a filler, a mixture of -7 to +9 mesh (JIS standard) graphite particles having a volume specific resistance of 0.8 Ω · cm and glass beads having a diameter of 2 mm and a volume ratio of 44% was used. The electrolytic extraction of copper from copper pyrophosphate was carried out under the same electrolytic conditions as in Example 1 except that the packed bed was filled with 10% by weight.

Table 1 shows the results obtained by measuring the amount of electrodeposited copper and the electrolytic treatment time in the same manner as in Example 1. It can be seen from Table 1 that the amount of copper electrodeposited was 4.2 g and the electrolytic treatment time was 29 hours.

As is clear from the above results, Example 1
The method of the present invention in which a suitable amount of conductive fibers and non-conductive fibers is entangled in the filler shown in and used as a mixture,
It was confirmed that this method is far superior to the conventional method shown in the comparative example, since the initial high electrolytic extraction efficiency can be maintained for a long time.

[0027]

As described above, according to the method of the present invention, a packed bed type metal electrowinning apparatus is used to obtain a metal salt solution,
In particular, when electrolytically collecting a metal from a metal salt solution having a low electrical conductivity and a dilute concentration, it is possible to collect a metal in a high yield by maintaining a high initial collection efficiency for a long time. It can exert an excellent effect on the treatment of industrial wastewater.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing the outline of a packed bed metal electrowinning apparatus used in the method of the present invention.

[Explanation of symbols]

 1 Electrolyzer 2 Plate-like Anode 3 Plate-like Cathode 4 Diaphragm 5 Spacer 6 Conductive Medium Substance (Filled Bed) 7 Liquid Inlet 8 Overflow Outlet

Claims (4)

[Claims] 1. A plate-like anode, a plate-like cathode installed so as to face the plate-like anode, and a liquid-permeable diaphragm provided near the plate-like anode and isolated from the surface of the plate-like anode. When performing electrolytic electrowinning of metal using a packed bed electrowinning apparatus comprising a packed bed made of a conductive medium substance provided between the plate cathode and the liquid permeable membrane,
A conductive fiber is used as the conductive medium substance forming the packed bed, and the packed bed is filled as a mixture in which the conductive fiber is entangled with the non-conductive fiber. A metal electrowinning method, characterized in that electrolysis is carried out by causing a current to flow between both electrodes to deposit a metal on the surface of the mixture. 2. The metal electrowinning method according to claim 1, wherein the conductive fiber is one of carbon fiber and fibrous activated carbon, or a mixture of both. 3. The metal electrowinning method according to claim 1, wherein the non-conductive fibers are polyester fibers or polypropylene fibers. 4. The metal electrowinning method according to claim 1, wherein the conductive and non-conductive fibers have a diameter of 10 to 15 μm, and the fibers formed by mixing the two have a felt shape.