JPH0688271A - Carbonaceous electrode type electrolytic cell - Google Patents

Abstract

PURPOSE:To minimize the elution of carbonaceous electrodes as carbon dioxide by reaction with the gaseous oxygen generated by the carbonaceous electrodes and the deterioration of these electrodes at the time of using the carbonaceous electrodes in an oxygen generation electrolysis or electrolytic treatment. CONSTITUTION:The desorption of the carbon dioxide to be generated by forming ferrite coating layers 7 in a part or the whole of the positive polarization surfaces or anode surfaces of the carbonaceous electrodes 5 is suppressed, by which the further formation of the carbon dioxide is prevented and the ratio of the exposure of the carbonaceous electrodes 5 to water to be treated is suppressed to the required min. ratio. The formation of the ferrite coating layers 7 in a part of the carbonaceous electrodes 5 is executed by once forming the coating layers 7 in the whole of the positive polarization surfaces or the anode surfaces of the carbonaceous electrodes 5, then chipping off a part or using the ferrite particles of the particle sizes smaller than the hole diameters of the carbonaceous electrodes 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbonaceous electrode type electrolytic cell which can be used as an electrolytic plating bath in the plating industry for treating various kinds of water to be treated or for electrolysis of various electrolytic solutions, and more specifically, containing a microorganism. For sterilization of water to be treated such as fish culture water, performance improvement, or electrolytic treatment or electrolysis of the electrolytic solution while generating oxygen gas such as silver recovery from the photographic processing solution, or plating as a highly resistant anode material A carbonaceous three-dimensional electrode type electrolytic cell using a suitable carbonaceous three-dimensional electrode.

[0002]

2. Description of the Related Art In addition to natural fish breeding in the sea and rivers as various fish resources, recently, farmed fish in farms and the like have attracted attention, and many farmed fish have been supplied to the market. When breeding these fish in aquaculture farms, bacteria and fungi contained in aquaculture water may inhibit the growth of the fish or kill them, but even if the bacteria are low, the fish are contaminated. It adheres to fish or fish and reduces its commercial value. In order to suppress these adverse effects, a fungicide such as a bactericide is added to the water for fish culture in a large amount, and further, an antibiotic is administered in order to suppress the damage of the fish due to the fungicide to the minimum source. In addition, a large amount of nutrients such as vitamins is administered to fish in order to increase resistance, and food is provided on the fish. Therefore, the fish that are bred have a small amount of food required for rearing with respect to the total intake, so that the growth rate, which is essential in aquaculture, is slowed down, and further growth of the antifungal agent is inhibited or the growth of human body is inhibited. Fish that are contaminated with a mildew-proofing agent will be supplied to the market. Further, dissolved oxygen of about 8 ppm exists in the water for fish farming as in ordinary water, and fish ingest this oxygen to grow. Administration of a large amount of chemicals reduces the dissolved amount of this oxygen, or reacts with dissolved oxygen to reduce the dissolved oxygen amount and inhibits growth.

Of course, in addition to water for fish farms, there is water to be treated which requires electrolysis or electrolytic treatment with gas generation. The protection of fish by the above-mentioned antifungal agent causes not only the problem of contamination of the fish itself, but also the amount of antifungal agent to be used due to the enormous amount of water for fish farming, which causes a problem that the cost increases. ing. Further, the cost of the nutritional supplement that accompanies the use of the fungicide also becomes enormous, and it is not directly connected to the growth of fish, but rather, the use of the fungicide which causes an adverse effect can be avoided at a low cost to the human body. The advantages are enormous because harmless fish can be grown and commercialized in a short period of time.

Further, if the dissolved oxygen concentration of the fish culture water can be increased, the activity of the fish becomes active, and the intake of the food increases accordingly, and the growth of the fish is significantly promoted. If the dissolved oxygen concentration can be increased at a low cost, it is possible to cultivate and supply to the market fish that are larger in size and have higher commercial value than ordinary cultured fish in a short period of time. Further, also in the case of antifungal treatment of water to be treated other than fish farm water, the use of antifungal agents causes similar drawbacks, and the increase in dissolved oxygen amount often causes various advantages. The carbonaceous electrode is used not only for treating water to be treated but also as an electrode for electrolytic reaction such as electrolysis for oxygen generation, electrolytic plating, and water electrolysis.

[0005]

A three-dimensional electrode having a huge surface area is widely used as an electrolytic cell used for electrolytic treatment or electrolysis involving the generation of gas, and the material for the three-dimensional electrode is A carbonaceous material that is inexpensive and has excellent performance as an electrode material is used. However, when the carbonaceous material comes into contact with oxygen gas, carbon on the surface thereof reacts with the oxygen gas and is eluted as carbon dioxide to be consumed. The present inventors have installed a platinum group metal oxide-coated electrode or the like on the side of the three-dimensional electrode that is positively polarized to cause gas generation on the platinum group metal oxide-coated electrode and We have proposed an electrolytic cell designed to prevent elution. However, since the cost of the platinum group metal oxide-coated electrode is high and not economical in this electrolytic cell, an electrolytic cell using a carbonaceous three-dimensional electrode that produces the same effect at a lower cost is required.

[0006]

It is an object of the present invention to provide a carbonaceous material which is inexpensive and has excellent activity as an electrode substance but lacks resistance to oxygen gas which is often generated by electrolysis in a state where the resistance to oxygen gas is improved. An object is to provide a carbonaceous electrode type electrolytic cell that can be used.

[0007]

According to the present invention, in a carbonaceous electrode type electrolytic cell containing a carbonaceous electrode as an electrode, a ferrite coating layer is formed on a part or the entire surface of the carbonaceous electrode which is positively polarized. It is a carbonaceous electrode type electrolytic cell characterized by the above.

The present invention will be described in detail below. The present invention is
Although it is inexpensive and excellent in activity as an electrode substance, in view of the characteristic of the carbonaceous material that it lacks resistance to oxygen gas often generated by electrolysis, even if the carbonaceous material is used for electrolysis involving oxygen gas generation, it is slightly It is a carbonaceous electrode type electrolytic cell that uses as an electrode the carbonaceous material that can be efficiently electrolyzed or electrolyzed only with the consumption of various carbonaceous materials. This can be achieved by forming a ferrite coating layer.
The electrolytic cell according to the present invention is a carbonaceous electrode type electrolytic cell having a carbonaceous electrode, preferably a carbonaceous three-dimensional electrode type electrolytic cell, a bipolar electrode fixed bed type three-dimensional electrode type electrolytic cell, a single electrode type fixed electrode. It includes a floor type three-dimensional electrode type electrolytic cell and an electrolytic cell having a normal plate-shaped or perforated plate-shaped electrode. In normal electrolysis or electrolytic treatment, the more often the water to be treated or the electrolytic solution comes into contact with the three-dimensional electrode or the like, the higher the electrolysis efficiency or treatment efficiency. Therefore, using a three-dimensional electrode electrolytic cell such as a bipolar fixed bed type with a large surface area such as electrodes can improve the processing efficiency compared to the case of using other electrolytic cells, thereby achieving the same processing efficiency. This is advantageous in that the device size required for this can be made smaller than other electrolytic cells.

The carbonaceous electrode in the carbonaceous electrode type electrolytic cell of the present invention may be a plate-shaped, porous plate-shaped or rod-shaped, as well as a porous three-dimensional material permeable to the water to be treated or the electrolytic solution, for example, a felt-shaped material. It is desirable that the carbonaceous electrode be formed of a carbonaceous material such as activated carbon, graphite, carbon fiber or the like having a shape such as a woven fabric shape, a porous block shape, or a solid body having a large number of through holes. Although it may be used as an anode, the carbonaceous electrode is preferably used as a dielectric substance which is polarized in an electric field and is polarizable to a cathode. When used as a dielectric, the carbonaceous electrode is placed in a direct current or alternating current electric field, and a direct current voltage is applied between the positive and negative electrodes for power supply composed of flat plate-shaped or expanded mesh-shaped or perforated plate-shaped porous plates installed at both ends. A low frequency AC voltage is applied to polarize the three-dimensional electrode, and positive and negative charges are formed at one end and the other end of the three-dimensional electrode to polarize the three-dimensional electrode. In addition to this, separate from the power supply anode and cathode, a carbonaceous three-dimensional material that functions alone as an anode or as a cathode is installed so as not to be short-circuited alternately and electrically connected to form a multipolar fixed bed electrolysis. It can be a tank. When using a solid body having a large number of through holes as described above as a three-dimensional electrode, the aperture ratio is 10% or more and 95% or less, preferably 20% or more so as not to interfere with the movement of the water to be treated. 80% or less.

When such a carbonaceous electrode is used as an anode for electrolysis or electrolytic treatment reaction involving oxygen gas generation or as the above-mentioned dielectric, the carbonaceous electrode reacts with oxygen gas and a part is eluted as carbon dioxide. Deterioration of the carbonaceous electrode occurs. Therefore, in the present invention, a ferrite coating layer is formed on a part of the surface of the carbonaceous electrode used as an anode or the positively polarized surface of the carbonaceous electrode used as a dielectric to deteriorate the carbonaceous electrode. To minimize. When an AC voltage is applied, a ferrite coating is formed on both surfaces facing both electrodes. The method of forming the ferrite layer on the carbonaceous electrode is not particularly limited, but a method of spraying or vapor depositing ferrite particles can be adopted. When a ferrite layer is formed on the entire surface of the carbonaceous electrode, the electrode activity of the carbonaceous material is lost, so it is necessary to coat the ferrite layer so that at least a part of the carbonaceous material is exposed on the surface. The ferrite coating area with respect to the electrode area is preferably 30 to 100%, and the protection function of the carbonaceous electrode by the ferrite of less than 30% becomes insufficient. The thickness of the ferrite layer cannot be unconditionally limited because it depends on the composition of the electrolytic solution and the electrolytic conditions, but it is usually desirable to set it in the range of 50 μm to 2 μm.

Then, for example, when a porous three-dimensional electrode is used as the carbonaceous electrode and particles having a pore size smaller than that of the three-dimensional electrode are used as the ferrite particles to form the ferrite coating layer, the ferrite particles become the carbonaceous electrode. Block the pores (for example, ferrite particles with a diameter of 40 μm
When spraying on the carbonaceous electrode of μm, the pores of the carbonaceous electrode are clogged), and the surface of the carbonaceous electrode is covered, and the electrode activity of the carbonaceous electrode is completely lost. In order to suppress such a decrease in electrode activity, a ferrite coating layer is once formed on the entire surface of the carbonaceous electrode or on the side that undergoes positive polarization, and then a part of the coating layer is cut into a groove shape to expose the carbonaceous material. To cause the electrode activity, or by spraying or vapor depositing ferrite particles having a diameter larger than the pore size of the carbonaceous electrode, without allowing the ferrite particles to enter the inside of the carbonaceous electrode, and the carbonaceous electrode surface is partially The electrode can be manufactured so that it is exposed.

Further, the surface of the carbonaceous electrode can be exposed by spraying a mixture of ferrite particles and a water-soluble substance such as sodium chloride on the carbonaceous electrode and then eluting the sodium chloride. In addition to this, the ferrite particles are sprayed with a grid-shaped metal, such as stainless steel, copper, or nickel, placed on the sprayed surface, and the ferrite coating layer is formed only on the part where the grid-shaped metal does not exist, and the other parts are sprayed. It is also possible to expose the carbonaceous material. The ferrite coating layer thus formed is presumed to have a large number of ferrite particles carried on the surface of the carbonaceous electrode as a single coating layer. The water to be treated is brought into contact with the carbonaceous electrode through the space between the adjacent ferrite particles, or is brought into direct contact with the carbonaceous electrode in a portion where the ferrite particles are not present to perform electrolytic treatment of the water to be treated or the like. Then, the presence of the ferrite coating layer causes an oxygen gas generation reaction on the ferrite coating layer, and oxygen generation on the carbonaceous three-dimensional electrode can be suppressed, so that the elution of the carbonaceous three-dimensional electrode is effective. It is considered to be prevented.

To further suppress the elution of the carbonaceous electrode, a platinum group metal oxide such as iridium oxide or ruthenium oxide is formed on a base material such as titanium on the surface of the carbonaceous electrode on which the ferrite coating layer is formed. A porous material which is coated with a substance and which is usually used as an insoluble metal electrode may be placed in contact with each other so that oxygen generation mainly occurs on the porous material. In the electrolytic cell of the present invention, when the carbonaceous electrodes or the carbonaceous electrode and the power feeding electrode terminal are brought close to each other in order to reduce the voltage, an electrically insulating spacer such as an organic polymer is used to prevent a short circuit. It is preferable to insert a mesh spacer made of a material. The three-dimensional electrode type electrolytic cell of the present invention can be used not only for electrolysis or electrolysis treatment involving gas generation but also for electrolysis or electrolysis treatment without gas generation.

When used for electrolysis or electrolytic treatment involving gas generation, the oxygen gas and hydrogen gas that are generated are usually generated at a mixing ratio within the explosion limit. Therefore, in order to avoid the danger of explosion, air, etc. It is preferable to dilute with an inert gas. For example, the separation means for the electrolytic gas generated at the outlet of the electrolytic cell and the separated electrolytic gas are diluted with air to have an electrolytic gas concentration of 4
It is preferable to install a means for diluting so as to have a volume% or less, but if the capacity of the electrolytic cell is relatively small and the amount of generated gas is small, the gas separating means may not be installed. The carbonaceous electrode type electrolytic cell according to the present invention can be used for various purposes, but can be preferably used for modification treatment such as sterilization of water to be treated containing microorganisms. For example, fish culture water has an appropriate temperature and is supplemented with nutrients, and is in an environment where molds, bacteria and the like easily propagate. In the conventional electrolysis or electrolytic treatment, the number of molds and bacteria that do not ionize and receive the redox reaction on the electrode surface and die is extremely limited, and it is not completely sterilized. It is presumed that the situation is such that bacteria with strong resistance are instead propagated.

When a direct current voltage or a low frequency alternating voltage is applied to the water to be treated from the electrolytic cell of the present invention, non-ionized molds and bacteria in the water to be treated are also subjected to liquid flow to form an anode of a carbonaceous electrode type electrolytic cell or It is considered that a carbonaceous electrode having a very large surface area such as a cathode or a dielectric material, especially a carbonaceous three-dimensional electrode, is sufficiently contacted with the surface thereof to undergo a redox reaction and the cell is destroyed and killed. Therefore, an equivalent bactericidal or antifungal effect can be produced without using a conventional bactericide or antifungal agent. Further, when the water to be treated is hard water, impurities such as calcium ions and magnesium ions are contained. When the water to be treated is electrolyzed, it is reduced on the cathode of the electrolytic cell and precipitated as hydroxides thereof on the cathode or the like to be removed from the water to be treated, thereby not adversely affecting, for example, fish.

Generally, in the electrolytic treatment operation of the above-mentioned fish culture water, in order to increase the amount of dissolved oxygen which has a favorable effect on the growth of fish, the electrolytic treatment is carried out while actively generating oxygen gas. The surface of the carbonaceous electrode in the electrolysis cell is easy to elute, but the elution is suppressed by the ferrite coated on the surface as described above, and it is possible to effectively perform electrolysis or electrolytic treatment with oxygen generation. It will be possible. In the present invention, the value of the DC voltage or the low-frequency AC voltage applied between the positive and negative electrode terminals for power supply is not particularly limited, and may be any value that causes high current density electrolytic treatment in which gas generation occurs on the electrode surface. However, it is desirable that the frequency when using an AC voltage is 10 hertz or less.
When the treatment of the water to be treated or the electrolysis of the electrolytic solution is performed while the gas is generated by the electrolytic cell of the present invention, a part of the oxygen generated from the polarized three-dimensional electrode is subjected to the electrolytic treatment as it is. Dissolved in the water to be treated to raise the dissolved oxygen concentration to a value higher than the normal value, and the oxygen concentration consumed by the bacteria disappears due to the killing of the bacteria, so the oxygen concentration further increases and the fish It is possible to adjust the oxygen concentration to be suitable for growth and the like, or to achieve a predetermined electrolytic reaction such as generation of oxygen gas and hydrogen gas by water electrolysis. And, for example, the anode potential is +0.2 to +1.5 V (vs.SH
Although sterilization of water for fish farming and removal of impurities can be carried out within the range of E), since substantial oxygen gas generation occurs at +1.0 V or more, the anode potential is +1.0 V or more, preferably +1.2 V or more. The preferable cathode potential is in a range nobler than -0.5 V (vs. SHE), and sterilization treatment of fish-culture water to be treated and removal of impurities can be performed in this range. Oxygen gas is generated at an anode potential of +1.2 V or higher, and a small amount of ozone gas is produced as a by-product, and both gases have a favorable effect on the growth of fish.

If there is a relatively large void in the electrolytic cell of the present invention through which the water to be treated or the electrolytic solution to be electrolyzed flows, the water to be treated can flow without coming into contact with the carbonaceous electrode or the like. Since the treatment of water to be treated or the efficiency of electrolysis decreases,
It is desirable that the carbonaceous electrode is arranged so that the flow of the water to be treated or the like in the electrolytic cell does not short pass. When the water to be treated is water for fish farms, the carbonaceous electrode type electrolyzer having such a configuration is installed close to a fish farm or a fishing pond, and a part of the fish water for fish farms is circulated. It can be used by returning it to the aquaculture site after sterilization in the electrolytic bath etc., and in the case of silver recovery from the photographic processing liquid, install it close to the photographic processing bath and take a photograph. Electrolytic silver recovery can be performed while circulating the processing liquid. When the water to be treated supplied to the electrolytic cell is a laminar flow, it may pass through the electrolytic cell without sufficiently contacting the surface of the carbonaceous electrode. As a turbulent flow having a Reynolds number of 100 or more, particularly preferably 500 or more, it is more preferable to pass through the electrolytic cell or the like while sufficiently performing lateral movement.

If the effect is not sufficiently obtained by passing the electrolytic cell only once, the treated water which has been treated may be passed through the electrolytic cell again. To increase overall processing efficiency. Further, in the electrolytic cell of the present invention, a leakage current is generated in the electrolytic cell, and the leakage current may cause electrocution of fish in the fish farm, or may flow from the electrolytic cell through the water to be treated or the electrolytic solution into another metal member, May cause electrochemical corrosion such as elution. Therefore, a member having higher conductivity than the water to be treated or the like is installed so that one end thereof can be grounded in the back surface of the electrode and / or in the inlet / outlet pipe of the electrolytic cell where the positive and negative electrode terminals for feeding in the electrolytic cell do not face each other. Thus, the leakage current can be cut off.

Next, preferred examples of the electrolytic cell which can be used in the present invention will be explained based on the attached drawings, but the electrolytic cell used in the method of the present invention is not limited to this electrolytic cell. FIG. 1 is a schematic vertical sectional view showing an example of a bipolar electrode fixed bed type electrolytic cell that can be used as the electrolytic cell of the present invention. A cylindrical electrolytic cell body 2 having upper and lower flanges 1 is provided with a mesh-shaped power feeding anode terminal 3 and power feeding cathode terminal 4 near the upper end and the lower end, respectively. The electrolytic cell body 2 is preferably formed of an electrically insulating material that can withstand long-term use or re-use, and in particular, synthetic resins such as polyepichlorohydrin, polyvinyl methacrylate, polyethylene, polypropylene, polyvinyl chloride, and polychloroethylene. , Phenol-formaldehyde resin and the like can be preferably used. The power supply anode terminal 3 for applying a positive DC voltage is, for example, a carbon material (eg, activated carbon, charcoal, coke, coal, etc.), a graphite material (eg, carbon fiber, carbon cloth, graphite, etc.), a carbon composite material (eg, carbon). Metal powder mixed and sintered), activated carbon fiber non-woven fabric (eg KE-1000)
Felt, Toyobo Co., Ltd.), 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. Further, the power supply cathode terminal 4 facing the power supply anode terminal 3 and applying a negative DC voltage is, for example, platinum, stainless steel, titanium, nickel, hastelloy, graphite,
It is formed of a carbon material, mild steel, a metal material coated with a platinum group metal, or the like.

A plurality of, in the illustrated example, three fixed beds 5 clogged three-dimensional electrodes are stacked between the power feeding electrode terminals 3 and 4, and between the fixed beds 5 and between the fixed floor 5 and the above. Four porous diaphragms or spacers 6 are sandwiched between the power feeding electrode terminals 3 and 4. The surface of each fixed bed 5 facing the cathode terminal 4 for power supply is coated with a ferrite coating layer 7, and the fixed bed 5 adheres to the inner wall of the electrolytic cell body 2 and does not pass through the inside of the fixed bed 5, The leakage flow of the water to be treated or the like flowing between the electrolytic cell 5 and the side wall of the electrolytic cell body 2 is arranged as small as possible. When a diaphragm is used, a woven cloth, a biscuit plate, a particle-sintered plastic, a porous plate, an ion exchange membrane, etc. are used as the diaphragm, and a woven cloth, a porous plate, a net made of an electrically insulating material is used as a spacer. ,
A rod-shaped material or the like is used. When electricity is supplied to the electrolyzer 2 having such a structure from below so that the water to be treated such as fish culture water and the electrolytic solution are supplied from below as shown by the arrow in FIG. The positive upper surface is negatively polarized to generate an electric potential in the fixed bed 5 and between the fixed beds 5, and the water to be treated flowing in the electrolyzer contacts the fixed bed 5 polarized positively or negatively by the electric potential. Oxygen gas is generated as a result, and at the same time, the water to be treated is reformed. The generated oxygen gas is dissolved in the water to be treated and is taken out from above the electrolyzer 2 as water to be treated having a higher concentration of dissolved oxygen gas than the water to be treated before being supplied to the electrolyzer 2. The presence of the ferrite coating layer 7 minimizes the elution of the fixed bed 5 due to oxygen gas, so that the fixed bed 5 is not replaced, that is, without disassembling and assembling the electrolytic cell, which is a complicated operation. It is possible to treat the water to be treated and electrolyze the electrolytic solution over a period of time.

FIG. 2 illustrates a cylindrical fixed bed type carbonaceous three-dimensional electrode usable in the electrolytic cell of FIG. A coating layer 7 of ferrite particles having a particle size larger than the pore size of the carbonaceous material is formed on the side of the fixed bed 5 made of a carbonaceous material having a short cylindrical shape and subject to positive polarization, and a space between the adjacent ferrite particles is formed. Through this, the water to be treated in the electrolytic cell is brought into contact with the carbonaceous material for electrolytic treatment. FIG. 3 shows another example of a cylindrical fixed bed type carbonaceous three-dimensional electrode usable in the electrolytic cell of FIG. A ferrite coating layer is once formed on the positively polarized side of the fixed bed 5 by thermal spraying, and then a part of the ferrite coating layer 7 is shaved into a lattice-shaped groove 8 to expose the carbonaceous material. Thus, the water to be treated and the carbonaceous material are brought into contact with each other, and the water to be treated is electrolyzed.

[0022]

EXAMPLES Examples of electrolytic treatment of water to be treated using the electrolytic cell of the present invention will be described below, but the examples do not limit the present invention.

Example 1 Height made of transparent hard polyvinyl chloride resin 1
The electrolytic cell shown in FIG. 1 having a cylindrical shape with a flange of 00 mm and an inner diameter of 50 mm was installed in a fish culture water circulation system of a water tank for raising goldfish together with a filter and a pump. In the electrolytic cell, a thickness of 0.
Made of porous carbon with a 5 mm ferrite coating layer, the diameter is 50 mm and the thickness is 10 mm.
Two fixed beds of 26.4g are sandwiched between six polyethylene resin diaphragms with a diameter of 50mm and a thickness of 1.2mm with an opening ratio of 80%, and the diaphragms at the upper and lower ends are made of titanium with platinum plated on the surface. A 48 mm thick 1.0 mm mesh anode terminal for power supply and a cathode terminal for power supply were placed in contact with each other.

The ferrite coating layer is provided on the anodic polarization side of a fixed bed made of the carbonaceous material (average pore size 100 μm),
A SUS304 mesh with a mesh and wire diameter of 0.35 mm is installed, and ferrite particles with a particle diameter of 150 to 200 μm are placed at about 8000 to 8500 ° C.
Was formed by thermal spraying with a hydrogen gas plasma. The fish culture water in the water tank was supplied to the electrolytic cell at a rate of 0.5 liter / min, and the anode and cathode voltages shown in Table 1 were applied between the power feeding electrode terminals to perform the treatment of the fish culture water. The number of bacteria and the dissolved oxygen concentration in the fish culture water before and after passing through the electrolytic cell and the average weight of each fixed bed after 48-hour electrolysis are summarized in the upper column of Table 1.

[0024]

[Table 1]

[0025]

[Comparative Example 1] Electrolysis treatment of fish-cultured water was carried out under the same conditions as in Example 1 except that the ferrite coating layer was not formed on the fixed bed, and the number of bacteria and the dissolved oxygen concentration in the fish-cultured water before and after passing through the electrolytic cell and Table 1 shows the average weight of each fixed bed after electrolysis for 48 hours.
It is summarized in the bottom column. It can be seen from Table 1 that the formation of the ferrite coating layer does not significantly affect the sterilization efficiency and the amount of dissolved oxygen, but the weight of the fixed bed is hardly reduced and stable electrolytic treatment can be performed.

[0026]

Example 2 A ferrite coating layer was formed by spraying ferrite particles of 50 to 80 μm (less than the pore size of the fixed bed) on the anodic polarization side of the fixed bed, and then the ferrite coating layer was scraped off in a groove shape to obtain the ferrite. By changing the coverage of the coating layer over the anodic surface of the fixed bed in the range of 10 to 80%, the anodic potential is changed.
Table 2 summarizes the number of bacteria and the dissolved oxygen concentration in the fish culture water before and after passing through the electrolytic cell, and the average weight of each fixed bed after electrolysis for 48 hours in the same manner as in Example 1 with the cathode potential fixed to 1.2 V and -0.5 V. It was
From Table 2, it can be seen that if the coverage is less than 30%, the weight loss of the fixed bed after electrolysis is relatively large and the carbonaceous electrode protection function of the ferrite coating layer is not sufficiently fulfilled.

[0027]

[Table 2]

[0028]

[Example 3] A ferrite coating layer having a thickness of 37 µm was applied to one of two graphites having a length of 10 cm, a width of 5 cm, and a thickness of 0.5 cm (porosity 55%, weight 23.2 g) in the same manner as in Example 1. Was formed. Porous carbon on which a ferrite coating layer was formed was used as an anode, and porous carbon that was not formed was used as a cathode, and was divided into an anode chamber and a cathode chamber by a cation exchange membrane Nafion (trade name) 12 cm in length, 3 cm in width, and 10 in depth.
It was placed in a cm-shaped electrolytic cell. 320 g in this electrolytic cell
/ L sodium chloride aqueous solution was added, and the current density was 5
Sodium hydroxide was produced by electrolysis of sodium chloride under the conditions of A / dm ² and electrolysis voltage of 3.2 V, and the composition of the gas generated from the anode was measured. The gas composition in the initial stage of electrolysis was 9 chlorine.
3.7%, oxygen 2.4%, trace amount of hydrogen (the remaining carbon dioxide gas and chlorine gas are dissolved in the sodium chloride aqueous solution as carbonate ion, hypochlorite ion, chlorate ion, etc., the same applies below), and after 30 days The composition of the gas generated after passing 9 chlorine
It was 2.7%, oxygen 2.5%, and trace amount of hydrogen. When the ferrite coating layer deteriorates, the amount of oxygen generated increases, but it can be seen that the ferrite electrode (anode) of this example hardly deteriorates after 30 days. The weight of the anode after 2 days is 2
It was 3.1 g, and the weight loss was 0.4%.

[0029]

Comparative Example 2 Sodium chloride was electrolyzed under the same conditions as in Example 3 except that the graphite coating layer was not formed, and the composition of the gas generated from the anode was measured. The gas composition at the beginning of electrolysis was 93.8% chlorine, 2.2% oxygen, and trace amount of hydrogen, and the gas composition after 30 days was 89.3% chlorine, 4.
The amount of trace hydrogen was 7%, the weight of the anode was 21.2 g, and the weight loss was 8.6%. It can be seen that the durability is improved by forming the ferrite coating layer on the carbonaceous electrode.

[0030]

The electrolytic cell of the present invention is characterized by forming a ferrite coating layer on a part or all of the surface of the carbonaceous electrode of the carbonaceous electrode type electrolytic cell that undergoes positive polarization or the surface of the carbonaceous anode. It is a high-quality electrode type electrolytic cell (Claim 1). This ferrite coating layer suppresses the desorption of carbon dioxide generated by the reaction between the oxygen gas and the carbonaceous electrode that may occur on the anodic surface or the anode surface of the carbonaceous electrode during electrolysis or electrolytic treatment. Further generation of carbon dioxide can be prevented.

Therefore, even when the electrolytic cell of the present invention is used for a reaction in which electrolysis or electrolytic treatment is performed while generating oxygen gas, for example, the reaction can be performed while minimizing the consumption of the carbonaceous electrode. Thus, it is possible to provide an electrolytic cell in which the disadvantages of the carbonaceous electrode, which is cheap and has high electrode activity, can be utilized while the disadvantages of the carbonaceous electrode, which is easily deteriorated by oxygen gas, are suppressed. It is desirable to use a thermal spraying method to form the ferrite coating layer (claim 2), and the thermal spraying method can relatively easily form a coating layer having a substantially uniform thickness.

When a ferrite coating layer is formed on the entire anodic surface or anode surface of the carbonaceous electrode of the electrolytic cell of the present invention, the contact between the water to be treated and the carbonaceous electrode having an electrode activity is hindered, and the above-mentioned coating is performed. The electrolytic treatment of the treated water is stopped. Therefore, a part of the carbonaceous electrode must be exposed so that it can come into contact with the water to be treated. For that purpose, for example, first, a ferrite coating layer is formed on all of the anodic polarization surface or the anode surface of the carbonaceous electrode, and then the coating layer is shaved in a groove shape to expose a part of the carbonaceous electrode. 3) Alternatively, by coating ferrite particles having a relatively large particle size, for example, a particle size larger than the pore size of the carbonaceous electrode (Claim 4), a space is created between adjacent ferrite particles, and a treatment is performed through the space. It is possible to bring the water into contact with the carbonaceous electrode to carry out the electrolytic treatment. The ferrite coating layer preferably has a coverage of 30 to 100% (claim 5), and a coverage of less than 30% results in insufficient protection of the carbonaceous electrode.

[Brief description of drawings]

FIG. 1 is a schematic vertical cross-sectional view showing an example of a bipolar electrode fixed bed type electrolytic cell that can be used as the electrolytic cell of the present invention.

FIG. 2 is a schematic perspective view illustrating a cylindrical fixed bed type carbonaceous three-dimensional electrode usable in the electrolytic cell of FIG.

3 is a schematic perspective view showing another example of a cylindrical fixed bed type carbonaceous three-dimensional electrode usable in the electrolytic cell of FIG.

[Explanation of symbols]

1 ・ ・ Flange 2 ・ ・ Electrolyzer body 3 ・ ・ ・ Anode terminal for power supply 4 ・ ・ ・ Cathode terminal for power supply 5 ・ ・
・ Fixed floor 6 ・ ・ ・ Spacer 7 ・ ・ ・ Ferrite coating layer 8 ・ ・ ・ Groove

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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 (5)

[Claims] 1. A carbonaceous electrode type electrolytic cell containing a carbonaceous electrode as an electrode, wherein a ferrite coating layer is formed on at least a part of the anodic surface or the anode surface of the carbonaceous electrode. Electrode type electrolytic cell. 2. The electrolytic cell according to claim 1, wherein the ferrite coating layer is formed by thermal spraying. 3. The electrolytic cell according to claim 1, wherein a groove is formed on the ferrite coating layer side of the carbonaceous electrode. 4. The carbonaceous electrode is a porous three-dimensional electrode,
The electrolytic cell according to any one of claims 1 to 3, wherein the diameter of the ferrite particles forming the ferrite coating layer is larger than the pore diameter of the carbonaceous electrode. 5. A carbonaceous electrode having a anodic polarization surface or an anode surface of 30 to 30
The electrolytic cell according to any one of claims 1 to 4, wherein the ferrite coating layer is formed at 100%.