JPS63176489A - Electrode for electrolysis - Google Patents

Abstract

PURPOSE:To prolong the service life of an electrode for electrolysis and to enhance productivity and profitability by providing a coated layer and a packed bed consisting of metal which is not passivated and insoluble in an electrolyte and different with metal to be passivated to holes provided on the surface of a base material consisting of the metal to be passivated. CONSTITUTION:In an electrode used in the case of collecting metal or the like by electrolysis, holes are provided on the surface of a base material 1 consisting of metal or alloy which is passivated in the case of polarizing it in an electrolytic soln. At least one part or all parts of the inner surfaces of the holes provided to the base material 1 are covered with a first layer 2 consisting of one kind of metal, alloy, a compd. or a mixture thereof which is not passivated in the case of polarizing it in the electrolytic soln. and is insoluble therein. Then a second layer 3 consisting of metal, alloy or the like compd. which is different from them is applied on the first layer 2 and packed. Thereby the first and second layers 2, 3 do not fall in the case of peeling and collecting an electrolytic layer 4 and the electrical performance of the electrode is maintained over a long period.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electrode for electrolysis, and more specifically, the present invention relates to an electrode for electrolysis, and more specifically, pores are provided on the surface of a substrate made of a metal or the like to be passivated, and the pores are filled with an electrode for electrolysis that is not passivated. The present invention relates to an electrode for electrolysis, which has two different layers made of metals etc. insoluble in liquid, thereby extending the life of the electrode for collecting metals etc. by electrolysis, and thereby significantly improving productivity, economic efficiency, etc.

[Prior art and its problems] Conventionally, manganese dioxide, tin, zinc, copper,
Nickel etc. are extracted by electrolysis.

For the electrodes used in this electrolysis, for example, carbon materials such as lead alloys and graphite have been used as anodes for manganese dioxide, but due to the presence of impurities and mechanical strength, titanium has almost been replaced. ing. However, since titanium undergoes a passivation phenomenon as electrolysis progresses, there is a restriction that the current density cannot be increased. Therefore, the conventional method has been to keep the current density as low as about 50 to 60 A/ffl to minimize the passivation phenomenon.

In this way, electrolysis of manganese dioxide [takes zinc, copper,
Compared to electrowinning of other metals such as nickel, tin, antimony, etc., the current density is 1/8 to 1/10, so the production amount per unit area of the electrode is extremely small, and this point is the main reason for electrolysis. This has become an unavoidable problem for increasing speed and reducing costs.

In particular, in conventional electrolysis operations using 7-node titanium plates, electrolysis was carried out at a current density that was at the limit of passivation, so it was inevitable that the sliding voltage would always tend to rise, and the anode It was necessary to remove the passivation film on the titanium surface by polishing and reverse electrolysis, making the operation complicated.

As described above, the inability to increase the current density in the electrowinning process of manganese dioxide is extremely disadvantageous from the viewpoint of productivity.

However, in recent years, research has been conducted for the purpose of suppressing this passivation phenomenon at current density. Examples include plating a titanium plate with corrosion-resistant platinum or the like or coating it with a platinum group oxide such as ruthenium oxide.

In addition, in order to eliminate the disadvantage of the above method of poor durability, after coating a titanium plate with a first layer made of platinum or platinum group oxide, the surface is further coated with peracid, manganese dioxide, etc. There have also been reports of research literature on electrodes that attempt to protect the first layer and make it more durable, such as a method of covering the first layer with a second layer.

However, the surface coating layer of these electrodes is extremely brittle against impact forces, and due to cracks etc. during use, the second layer may become weaker than the first layer.
The layer collapses, and as a result, the first layer in contact with the substrate accelerates peeling and elution from the substrate, and cannot withstand long-term use as an electrode.

For example, in the electrolytic production of manganese dioxide, the target substance is electrodeposited on the anode, so the electrodeposited manganese dioxide is
It is necessary to strip the anode every time, and each time the platinum plating film and oxide film described above are peeled off from the surface of the titanium plate along with the electrodeposited manganese dioxide, and the surface layer disappears within a short period of time, and at the same time the substrate causes passivation and becomes incapable of electrolysis. Furthermore, in the case of zinc electrowinning, where the cathode is frequently taken in and taken out of the electrolytic tank, the cathode comes into contact with or collides with the anode each time it is taken out and taken out of the electrolytic tank, resulting in the collapse of the 7-node surface layer. .

For these reasons, the above-mentioned electrodes have not yet reached the stage of practical use, and solving these problems is an urgent need for speeding up electrolysis and improving productivity.

[Object of the invention] The object of the present invention is to overcome the drawbacks of the prior art,
The object of the present invention is to provide an electrode for electrolysis that has a longer lifespan while maintaining the electrical performance of the electrode, and that contributes to improvements in productivity, economic efficiency, etc.

[Means and effects for solving the problem j As a result of extensive research by the present inventors in order to solve the above problem,
The surface of a base made of valve metal, etc., which becomes passivated when polarized in an electrolytic solution, is perforated, and the inner surface of the hole obtained does not become passivated when polarized in an electrolytic solution. , a first layer made of a metal, alloy, or one of these compounds insoluble in an electrolytic solution is fixed, and a metal, alloy, or one of these compounds insoluble in an electrolytic solution different from the first layer is roughly filled in the pores. The present invention was developed based on the finding that an electrode coated and filled with a second layer consisting of at least one type can achieve the above object.

In other words, the present invention provides a) a base made of at least one metal or alloy that becomes passivated when polarized in an electrolytic solution, and having pores on its surface; and b) at least pores of the entire surface of the base A metal, alloy, compound, or a mixture thereof that does not become passivated when polarized in an electrolyte and is insoluble in the electrolyte, provided on a part or all of the surface of the
C) a first layer consisting of a seed, and C) polarized in an electrolytic solution provided so as to cover and fill at least some or all of the pores of the entire surface of the substrate on which the first layer is applied. An electrode for electrolysis, characterized in that it has a first layer that does not passivate and is insoluble in an electrolytic solution, and a second layer that is made of at least one kind of different metal, alloy, compound, or mixture thereof. be.

In the present invention, the so-called passivating metal, alloy, or compound that forms an insulating film when polarized in an electrolytic solution used as a base is one that has sufficient corrosion resistance against the electrolytic solution, Specifically, titanium, niobium,
Examples include so-called valve metals such as tantalum and zirconium, lead, and alloys and compounds thereof. A plurality of these metals may be used as a base. As for the shape of this base body, any shape such as a flat plate, a flat plate with holes, a lattice-like plate, etc. is applicable.

The electrode of the present invention is provided with one or more holes of an appropriate size on the surface of this substrate. The pores of an appropriate size as used herein refer to the 25th infiltration material covered and filled with the pores.
However, the size is such that it will not come off due to the impact force when removing electrodeposited manganese dioxide, etc. The shape of the hole is usually considered to be cylindrical, but it can be of any shape.For example, even a hole that penetrates the electrode base in the thickness direction (through hole, see Figure 1 (ω)) may be open only on one side. It may be a closed hole (see Figure 1 (b)), and any shape or size may be used as long as the first layer or second layer does not peel or come off from the hole due to impact. When the pore size is constant, the larger the number of pores in a closed pore, the larger the overall surface area of the electrode, and therefore a higher current density can be obtained with a lower electrolytic voltage. However, if the pore size is too large, It may be difficult to maintain sufficient strength as an electrode base, so sufficient consideration is required.

As mentioned above, the size, shape, number, etc. of the holes are determined not only to ensure that the mechanical strength of the electrode base is not impaired, but also to prevent the first and second layers inside the holes from coming off. Appropriate selection will be made based on a comprehensive judgment based on gender, etc.

In the electrode of the present invention, out of the entire surface of the substrate having pores, at least a part or all of the inner surface of the pore contains a metal that does not become passivated when polarized in an electrolyte and is insoluble in the electrolyte. , an alloy, a compound or a mixture thereof. The metal constituting this first layer is a conductive substance that has sufficient corrosion resistance against electrolyte, and specifically includes platinum group metals such as platinum, iridium oxide, and ruthenium oxide, alloys, and compounds thereof. A mixture of the following may be mentioned.

Furthermore, in the present invention, this 11i! At least part or all of the inside of the pores of the entire surface of the substrate coated with at least a metal that does not passivate when polarized in the electrolytic solution and is insoluble in the electrolytic solution and is different from the first layer. A second layer consisting of one type is coated and filled. Like the first layer, the metal forming this second layer is also an S-conducting material that has sufficient corrosion resistance against electrolytes, and specifically, relatively inexpensive manganese dioxide, lead peroxide, etc. are preferable. used. This second layer may be composed of multiple layers.

As a method for fixing these first and second layers, a baking method, an electrolytic method, a welding method, a pressure bonding method, a cladding method, a fitting method, a riveting method, etc. are employed. The locations where the first layer is fixed are:
It is sufficient to coat only the inner surface of the hole, and the layer fixed to other parts than the inner surface of the hole will peel off within a short period of time, so it is not necessary to fix it to the entire surface of the electrode. However, when fixing by plating, baking, etc., it may be cheaper to fix the electrode over the entire surface of the electrode than to fix it only partially on the inner surface of the hole. Which one to use should be selected depending on the conditions at that time. The purpose of coating with the second layer is to prevent peeling and elution of the first layer, but the impact resistance effect will be greater if the entire void in the hole is completely covered and filled with the second layer. Of course.

In fact, in the electrolytic production of manganese dioxide, unless the second layer is made of a substance other than manganese dioxide such as lead peroxide, if the second layer is manganese dioxide, manganese dioxide is electrodeposited during electrolysis. Therefore, there is no need to separately fix manganese dioxide before using the electrode.

Using the electrode according to the present invention as a 7-node electrode, electrowinning of manganese dioxide was repeatedly performed at a current density several times the current density of 60 A/Td, but the first and second layers, which are the fixed layers inside the holes, were It has been demonstrated that it can be used for a longer period of time than conventional electrodes without coming off or eluting.

Such an electrode for electrolysis of the present invention can be used not only as an anode for manganese dioxide electrolysis, but also for electrolytic extraction of peracid from a lead nitrate bath, and for electrolysis of zinc, copper,
It goes without saying that it can also be used as an effective electrode when electrolytically extracting nickel or the like from a sulfate bath.

[Examples] Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

Examples 1 to 5 and Comparative Examples 1 to 4 For titanium plates of 50mX 200mX 5#lI thickness,
Regarding the electrode (7 nodes) A-1 that had been subjected to perforation and other treatments, electrolysis of manganese dioxide was repeatedly performed under the conditions shown in Table 2, and changes in electrolysis voltage and bridge life were evaluated. The results are shown in Table 1 and in Figure 2.

The number of days for each electrolysis was 7 days, and after each electrolysis, the N-deposited manganese dioxide was subjected to impact with an iron hammer to be peeled off from the anode.

The anode was used for repeated electrolysis as it was.

Table 1 *1; Area of part immersed in electrolyte 50m5+X 10
06x 2 sides, *2; Penetration: both open hole type, closed: indicates obstructed hole type (see Figure 1), *3; Fixing method is as follows.

lr 02, RIJ 02: Application of each compound, coating by firing, Pt: Plating method, Mn 02: FaM, yjj-NWt,
The fixed parts are as follows.

Perforated electrode (A-E): Fixed only on the inner surface of the hole, non-perforated electrode (
F-H): Fixed on the entire surface *4: Plating thickness is approximately 0.2 μm.

As shown in Table 2, Table 1, and Figure 2, when the anode of Comparative Example 4 without any treatment was used on the non-porous titanium substrate, the current was 180 A/min. Under high density conditions, immediately after the start of electrolysis, it turned into a non-vJ state and could no longer be energized.

In addition, in the anodes F-H of Comparative Examples 1 to 3, in which the surface of the non-porous titanium plate that is the substrate is coated with iridium oxide or ruthenium oxide and manganese dioxide, the electrolysis voltage gradually increases as the number of electrolysis increases, After 840 hours, passivation occurred and it became impossible to conduct electricity. This anode F-
When H was measured using a surface analyzer, it was found that the iridium and ruthenium oxide films had disappeared and a titanium oxide film had occurred in their place. Note that the anode G of Comparative Example 2
Anode H of Comparative Example 3 and Anode H of Comparative Example 3 differ in the amount of ruthenium oxide coated, and Anode G of Comparative Example 2 has a smaller amount of ruthenium oxide coated.

On the other hand, the anodes A to E of Examples 1 to 5, in which a titanium plate serving as a substrate was bored to provide through holes or closed holes, and the holes were coated with iridium oxide, platinum, ruthenium oxide, and manganese dioxide, had a diameter of 180 A/7 d. 16 under high current density
Despite being used for a long period of 80 hours, no passivation phenomenon was observed, the electrolysis voltage increased only slightly, and no problems were observed in electrolysis. Anode A- after use
When the surface of Sample E was analyzed in the same manner, there was almost no peeling or wear of the fixed film of the first layer. The current efficiency was approximately the same as that of the conventional method, and the crystalline form of manganese dioxide obtained was identified as γ-manganese dioxide, which is mainly used for dry batteries. The properties of the electrodeposited manganese dioxide block were also dense, similar to those produced by the conventional method.

[Effects of the Invention] As is clear from the above description, the electrode for electrolysis of the present invention, in which holes are provided on the surface of the substrate and two different layers are provided in the holes, is suitable as an electrode for collecting metals, etc. by electrolysis. It is suitable for use as an electrode for manganese dioxide electrolysis and other electrodes because it extends the life of the electrode and significantly contributes to improving productivity, economy, and workability.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1(a) and FIG. 1(a) are cross-sectional views of a through-hole type and a closed-hole type, respectively, showing an example of the electrolytic electrode of the present invention. FIG. 1(C) is a cross-sectional view of a conventional electrolysis electrode. Cross-sectional view showing the electrode for electrolysis, 2nd
The figure is a graph showing the relationship between the sliding voltage and the number of days of electrolysis when manganese dioxide is electrolytically extracted using the electrodes of Examples 1 to 5 and Comparative Examples 1 to 4 as seven nodes. 1: Substrate, 2: First layer, 3: Second layer, 4: Electrodeposition layer. Patent applicant Mitsui Kinzoku Mining Co., Ltd. Agent Patent attorney Tatsuo Ito Agent Patent attorney Tetsuya Ito Figure 1 (0) Figure 1 (1)) Figure 1 (c)

Claims (1)

[Scope of Claims] 1. a) a substrate made of at least one metal or alloy that becomes passivated when polarized in an electrolytic solution and having pores on its surface; b) of the entire surface of the substrate; A first layer made of a metal, alloy, compound, or a mixture thereof that does not become passivated when polarized in the electrolyte and is insoluble in the electrolyte, and is provided on at least part or all of the surface within the pore. c) at least a part or all of the pores of the entire surface of the substrate on which the first layer is applied, when polarized in an electrolytic solution, which is provided so as to cover and fill the pores; without passivation,
and a second layer made of at least one metal, alloy, compound, or mixture thereof different from the first layer and insoluble in the electrolytic solution.
An electrode for electrolysis characterized by having a layer. 2. The electrode for electrolysis according to claim 1, which is used as an anode for manganese dioxide electrolysis.