JP2008126184A - Electrode for preventing adhesion of organism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the following problems: an increase in an electric resistance value on the surface of an electrode for preventing adhesion of organisms occurs after long-term usage to decrease an electron transfer velocity between microorganisms and the electrode, make uniform impression of a setting electric potential over the whole of the electrode difficult, the electric resistance value on the surface of the electrode can be reduced by the conventional method where platinum is carried on the surface of the electrode, but increases when the platinum is consumed after a long-term use, and the conventional method using platinum also has a large problem with cost. <P>SOLUTION: Iridium oxide of 35-65 mol% and tantalum oxide of 65-35 mol%, calculated as metal, are carried on a part of a substrate made of titanium or a titanium alloy, required to be prevented from organism adhesion, through a conductive titanium oxide layer, so that an electrochemical antifouling effect can be obtained stably for a long time. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention is an anti-biofouling prevention method that electrochemically prevents organisms and scales from adhering to offshore structures, ships, water transportation pipes or waterways, fishing nets, heat exchangers, seawater intake screens, etc. The present invention relates to an electrode.

Many organisms exist in seawater and freshwater, and adhere to the surface of underwater structures, causing various problems. For example, when adhering to a ship or a buoy, a problem of increased propulsion resistance occurs. Moreover, when it adheres to the aquaculture ginger, problems such as inhibition of seawater exchange occur. Furthermore, problems such as deformation of nets occur when attached to fishing nets such as stationary nets.
In addition, microorganisms attached to the pipes and valves of water supply / drainage cause problems such as contaminating people and products through seawater and fresh water.
The general mechanism of biological attachment to the surface of structures in contact with seawater and fresh water is as follows.
First, adherent gram-negative bacteria adsorb to the surface of the structure and secrete a large amount of slime-like substances derived from lipids. Furthermore, Gram-negative bacteria gather and grow in this slime layer to form a microbial coating. In the seawater, large organisms such as algae, shellfish, and barnacles, which are large organisms, adhere to the microbial coating. The attached large creatures will breed and grow, eventually covering the surface of the underwater structure.
As an antifouling means for organisms adhering to the surface of such underwater structures and seawater or fresh water, a bactericidal substance is added to the antifouling surface, or a paint film containing an organotin compound is used. In general, an organic tin-based compound is eluted and an antifouling method using chlorine generated by electrolyzing seawater is generally performed. However, these methods generate harmful substances, and there is a concern about the impact on the organism due to water pollution.

In recent years, methods have been proposed for controlling organisms attached to the surface of an underwater structure, seawater, or fresh water that is electrochemically contacted without generating harmful substances.
In this electrochemical biological control method, when a potential higher than a predetermined potential at which a direct electrochemical reaction with a microorganism is confirmed is applied to the microorganism, the redox substance inside the microorganism is irreversibly oxidized, and the respiration of the microorganism It is said that it is possible to induce a decrease in the activity and the permeation barrier of the microbial membrane and kill the microorganism (see Japanese Patent Publication No. 6-91821: Patent Document 1). Incidentally, in the marine-adherent bacterium Vibrio arginolyticus used in the present invention, 0.7 Vvs. The oxidation peak current can be confirmed by SCE. In other words, since the predetermined potential at which direct electrochemical reaction with microorganisms is confirmed occurs below the decomposition potential of fresh water or seawater that is the electrolyte, there is no production of chemical substances and only microorganisms that adhere to the conductive substrate are sterilized. It is possible to prevent the subsequent attachment of aquatic organisms. For this reason, it has been shown that this is an excellent antifouling method that is free from marine pollution and has no effect on the ecosystem of marine organisms (see Japanese Patent Application Laid-Open No. 2003-265068).
Japanese Patent Laid-Open No. 9-248554 (see Patent Document 3) discloses a step of adsorbing and sterilizing microorganisms in water on the surface of the conductive substrate by applying a positive potential to the conductive substrate in water. By applying a higher positive potential to the conductive substrate, the cells of microorganisms adsorbed on the surface of the conductive substrate are destroyed, and the sterilized microorganisms adhering to the conductive substrate and their decomposition products are detached. The invention is summarized as a method for controlling an aquatic microorganism characterized in that Further, in Japanese Patent No. 3105024 (see Patent Document 4), in water, by applying a positive potential to the conductive substrate, the microorganisms in the water are adsorbed on the surface of the conductive substrate and sterilized (+0 to 1). .5 V vs SCE) and a step (−0 to −0.4 V vs SCE) for removing sterilized microorganisms adsorbed on the surface of the conductive substrate by applying a negative potential to the conductive substrate. An invention having a gist of a method for controlling an underwater microorganism characterized by the above is described. Japanese Patent Laid-Open No. 2001-198572 (see Patent Document 5) adsorbs microorganisms in water to the surface of the conductive substrate by applying a positive potential that does not cause electrolysis to the conductive substrate in water. Sterilizing, applying a negative potential that causes electrolysis to the conductive substrate, reducing the surface of the conductive substrate, inducing an alkaline substance to the surface of the conductive substrate, and adsorbing to the surface of the conductive substrate And a process for removing the decomposed microorganisms and degradation products thereof, an invention having a gist of a method for controlling underwater microorganisms is described.

  Further, an antifouling method in which a positive potential is applied to the conductive coating film to generate hypochlorite ions or chlorine ions is disclosed in Japanese Patent Publication No. 6-15069 (see Patent Document 6) and Japanese Patent Publication No. 8-14036. It is described in the gazette (refer patent document 7), and it is thought that the antifouling effect by the chlorine injection system by a seawater electrolyzer generates chlorine etc. directly on the surface to be protected.

Japanese Patent Publication No. 6-91821 (page 3, line 42 to line 46, page 8, line 42 to line 44) JP2003-265068 (page 3, column 3, line 33 to line 47, page 7, column 12, line 38 to page 4, column 13, line 16) JP-A-9-248554 (page 6, line 4 to line 8) Japanese Patent No. 3105024 (page 3, line 20 to line 27, Fig. 1-4) JP 2001-198572 A (page 3, line 5 to line 8) Japanese Patent Publication No. 6-15069 (page 3, line 1 to line 6) Japanese Patent Publication No. 8-14036 (page 3, line 10 to line 12)

By applying a potential that does not cause electrolysis of seawater or fresh water to the biofouling prevention electrode, the method of sterilizing microorganisms and preventing fouling has no pollution of the ocean or river, and has an effect on the ecosystem of the organism. This is an excellent antifouling method because there is no rust. By the way, the above-mentioned electrochemical antifouling method was sterilized by applying a positive potential that does not cause electrolysis of seawater or freshwater to sterilize adhering microorganisms, and applied a negative potential that does not cause electrolysis of seawater or freshwater. The process of removing microorganisms, charged organic substances and scales, the process of applying a negative potential that causes electrolysis of seawater and fresh water to wash and reduce the surface to be protected, and electrochemically generating products By applying a positive potential, it comprises the steps of detaching and cleaning aquatic organisms and scales that directly or indirectly contact the surface of the biofouling prevention electrode and reactivating the biofouling prevention electrode. In the electrochemical antifouling method, in order to maintain the effect for a long period of time, it is necessary to clean and reduce the biofouling prevention electrode as the antifouling surface so that the sterilization step can be sufficiently performed by the cleaning step. During the cleaning process, the sterilization process and the desorption process cannot be performed, and magnesium hydroxide and the like are deposited on the surface of the biofouling prevention electrode, thereby inhibiting the electron transfer reaction. A positive potential is applied to generate product. Moreover, it is necessary to change the time allocation of each process according to an environment.
When the electrode for preventing biofouling, which is the surface to be protected, is applied by the positive potential, particularly when it is consumed by oxidation or elution in the process of reactivation, the electrical resistance value on the surface of the electrode for preventing biofouling Increase in the rate of electron transfer between the microorganism and the biofouling prevention electrode, and it may be difficult to apply a set potential uniformly across the antifouling biofouling prevention electrode. there were. Even with the conventional method of supporting platinum on the surface of the biofouling prevention electrode, although the electric resistance value on the initial electrode surface can be lowered, platinum is consumed when used for a long period of time. 5 μg / Ah) The electrical resistance value becomes high. In addition, the conventional method using platinum has a big problem in terms of cost.
Furthermore, it was difficult to support the base material having a surface roughness (Ra) of 0.5 μm or less.
Therefore, it has been necessary to study a biofouling prevention electrode that does not increase the electrical resistance value on the surface over time.

The present invention has been made in view of these problems, and while maintaining and improving the function as a biofouling prevention electrode serving as an antifouling surface, the electrochemical antifouling effect of the entire antifouling biofouling prevention electrode is prolonged. The aim is to obtain a stable environment.
The present invention relates to a biofouling prevention electrode in an electrochemical antifouling device comprising a biofouling prevention electrode, a counter electrode, and a power source for applying a voltage between the biofouling prevention electrode and the counter electrode. A biofouling prevention electrode for use in an electrochemical antifouling method using a direct electron transfer reaction with a living organism, wherein the biofouling prevention electrode is a conductive material provided on the surface of an electrode substrate made of titanium or a titanium alloy. A bioadhesion-preventing electrode characterized in that a mixed oxide of 35 to 65 mol% iridium oxide and 65 to 35 mol% tantalum oxide based on metal is supported on a titanium oxide layer. The gist of

In the electrochemical antifouling device, using the biofouling prevention electrode according to the present invention, by applying a positive potential that does not generate a product electrochemically from the electrolyte, directly or directly on the surface of the biofouling prevention electrode The proliferation of aquatic organisms that come into contact indirectly can be suppressed over a long period of time.
That is, a mixed oxide of 35 to 65 mol% of iridium oxide and 65 to 35 mol% of tantalum oxide based on metal is supported on the conductive titanium oxide layer provided on the surface of the electrode substrate made of titanium or titanium alloy. As a result, the electric resistance value on the electrode surface can be kept small even if the usage time elapses. This is a result of using iridium oxide, which consumes less than platinum, and does not use platinum, so there is no cost problem.
Furthermore, the surface roughness (Ra) of the titanium substrate can be supported on the smooth surface of up to 0.2 μm with the supported amount of the mixed oxide of iridium oxide and tantalum oxide, and the consumption of the electrode support is reduced. The rate can be improved.

Hereinafter, the present invention will be described in detail.
The biofouling prevention electrode according to the present invention is used in an electrochemical antifouling method using a direct electron transfer reaction with a living organism. This electrode for preventing bioadhesion is composed of 35 to 65 mol% iridium oxide and 65 to 35 mol% tantalum oxide based on metal on a conductive titanium oxide layer provided on the surface of an electrode substrate made of titanium or a titanium alloy. An electrode for preventing biofouling, characterized in that it carries a mixed oxide of
In the titanium or titanium alloy used as the base material, a corrosion-resistant conductive alloy mainly composed of titanium is used as the titanium alloy. For example, titanium-tantalum-niobium (Ti-Ta-Nb), titanium-palladium ( Ti-Pd), titanium-zirconium (Ti-Zr), titanium-aluminum (Ti-Al), and other titanium-based alloys that are usually used as electrode materials. The biofouling prevention electrode is not particularly limited as long as it can directly or indirectly contact aquatic organisms and can apply an electric potential. The electrode can be processed into a desired shape such as a plate, a perforated plate, a rod, or a plate net. It will not specifically limit if it has the function to maintain.

A living body carrying a mixed oxide of 35 to 65 mol% iridium oxide and 65 to 35 mol% tantalum oxide based on metal on a conductive titanium oxide layer provided on the surface of an electrode substrate made of titanium or a titanium alloy. The anti-adhesion electrode sterilizes aquatic organisms that directly or indirectly come into contact with the surface of the anti-adhesion electrode by applying a positive potential that does not generate oxygen or chlorine from water or seawater, and suppresses growth. It is possible to generate chlorine compounds or radicals from water, seawater, etc., and to reactivate aquatic organisms and scales that are in direct or indirect contact with the surface of the biofouling prevention electrode and the biofouling prevention electrode.

The titanium or titanium alloy used in the present invention (hereinafter, titanium base material) is preferably pretreated in advance. Specific examples of such pretreatment include the following. First, after degreasing the surface of the titanium substrate according to a conventional method, for example, washing with alcohol or the like and / or electrolysis in an alkaline aqueous solution, the hydrogen fluoride concentration is in the range of 1 to 20% by weight, particularly 5 to 10% by weight. Treated with a mixed acid of hydrofluoric acid in the water and an acid containing a carbonyl group (carboxylic acid, ascorbic acid, lactic acid, formic acid, acetic acid, etc.) in the range of 1 to 20% by weight, particularly 5 to 10% by weight By doing so, the oxide film on the surface of the titanium base material can be removed, and the inner surface of the titanium crystal grains can be finely roughened into fine protrusions. The acid treatment can be carried out at a temperature from room temperature to about 40 ° C. for a few seconds to a dozen minutes depending on the surface condition of the titanium substrate.

By the treatment described above, the roughness (Ra) of the titanium base material surface can be set to 0.2 μm or more. When the surface roughness (Ra) is less than 0.2 μm in this biological adhesion prevention electrode, the adhesion strength between the mixed oxide of iridium oxide and tantalum oxide and the titanium base material on which the conductive titanium oxide layer is formed decreases. End up.
On the other hand, if the surface roughness is too large, when used as a biofouling prevention electrode for a long time, irregularities on the surface will accumulate microorganisms, dust, etc., and microorganisms will be adsorbed and propagated on the accumulated layer, thus preventing sufficient biofouling Since there is a possibility that the effect cannot be obtained, the surface roughness is preferably selected as appropriate according to the conditions such as the place of use and the biomass, but the surface roughness (Ra) of the titanium substrate is 0.2 to 0. .5 μm is preferred.

The titanium substrate surface can then be changed to a low oxidation state titanium oxide. This calcination can be generally performed by heating in the atmosphere at a temperature of about 300 to 600 ° C., preferably about 300 to 400 ° C. for about 10 minutes to 4 hours. As a result, a very thin conductive titanium oxide layer is formed on the surface of the titanium substrate. As described above, the titanium in the vicinity of the surface of the titanium base material having the roughened surface and the titanium oxide coating formed thereon can be changed to a titanium oxide in a low oxidation state. The thickness of the titanium oxide layer is generally within the range of 10 to 100 nm, preferably 20 to 60 nm. Further, the composition of the titanium oxide is such that x is generally 1 <x <2, especially 1. It is desirable that the range is 9 <x <2.

Next, 35 to 65 mol% of iridium oxide and 35 to 65 mol% of tantalum oxide based on metal are loaded. This is because the composition based on metal conversion of iridium oxide exceeds 65 mol%, the composition based on metal conversion of tantalum oxide is less than 35 mol%, and the composition based on metal conversion of iridium oxide is less than 35%. When the composition based on metal conversion exceeds 65 mol%, the amount of consumption during use increases. Further, when the composition based on metal conversion of iridium oxide is less than 35% and the composition based on metal conversion of tantalum oxide exceeds 65 mol%, it is difficult to uniformly apply a set potential to the entire electrode. By applying a solution containing an iridium compound and a tantalum compound, preferably a lower alcohol solution, to the surface of the titanium substrate on which the titanium oxide layer is formed as described above, and then drying, the iridium compound and the tantalum compound are applied to the substrate surface. Adhere. Examples of the iridium compound and the tantalum compound that can be used here include compounds soluble in a lower alcohol solvent that can be thermally decomposed under the firing conditions described later and converted into iridium oxide and tantalum oxide, respectively.

Examples of such iridium compounds include iridium chloride, iridium chloride, and potassium iridium chloride. Examples of tantalum compounds include tantalum chloride and tantalum ethoxide. On the other hand, examples of lower alcohols that can dissolve these iridium compounds and tantalum compounds include methanol, ethanol, propanol, isopropanol, butanol, and mixtures thereof. The total metal concentration of the iridium compound and the tantalum compound in the lower alcohol solution can be generally in the range of 2 to 200 g · dm ⁻³ , preferably 20 to 100 g · dm ⁻³ . When the metal concentration is lower than 2 g · dm ⁻³ , the loading efficiency is deteriorated, and when it exceeds 200 g · dm ⁻³ , aggregation tends to occur at the time of firing, and problems such as non-uniformity in loading strength and loading amount occur. .

The application of the solution onto the surface of the titanium substrate on which titanium oxide is formed can be performed, for example, by a spraying method, a brush coating method, a dipping method, or the like. In this way, a lower alcohol solution of an iridium compound and a tantalum compound. The titanium substrate to which is applied is dried at a relatively low temperature in the range of about 20 to 100 ° C. and then fired in an oxidizing atmosphere, usually in the air. The processing described above can be repeated until the loading amount reaches the above range. The calcination can be performed by heating to a temperature generally in the range of about 450 to 600 ° C., preferably about 500 to 550 ° C. in a suitable heating furnace such as an electric furnace, a gas furnace or an infrared furnace. . The heating time in that case can be made into about 5 minutes-2 hours according to the magnitude | size of the base material which should be baked. By this firing, the iridium compound and the tantalum compound are changed to iridium oxide and tantalum oxide, respectively, and a mixed oxide of iridium oxide-tantalum oxide can be formed on the titanium substrate on the titanium oxide layer. If the predetermined iridium oxide-tantalum oxide cannot be formed by a single operation, the above-described solution application-drying-firing process can be repeated a desired number of times.

  In the antifouling apparatus using the biofouling prevention electrode according to the present invention, a counter electrode is provided so as not to contact the biofouling prevention electrode. The counter electrode base material may be the same as the biological adhesion preventing electrode. Moreover, it can also select suitably according to the physical property and shape of a to-be-stained surface. Further, the biological adhesion preventing electrode and the counter electrode are not particularly limited as long as they are disposed so that the biological adhesion preventing electrode and the microorganisms react electrochemically.

The biological adhesion preventing electrode and the counter electrode are connected to the power supply device by lead wires. This power supply device is a device that applies a direct current between the biological adhesion preventing electrode and the counter electrode, and preferably has a function of converting the polarity. In addition, when there are few organisms living in water or seawater to the extent that antifouling can be maintained simply by applying a potential higher than the potential at which the direct electron transfer reaction between the electrode and the microorganism occurs, a constant current generator (galvano (Stat) can be used.
The potentiostat and galvanostat that can be used are not particularly limited as long as a predetermined potential can be applied to the biological adhesion preventing electrode or a constant current can flow. In particular, it is preferable to implement a DC power supply device to which voltage control or current control and timing control means are added.

Furthermore, a reference electrode can be used as necessary.
It is preferable to install the reference electrode in the vicinity of the working electrode, but do not use the reference electrode when the current value at the time when the antifouling effect is manifested is clear between the biological adhesion preventing electrode and the counter electrode. There is no problem.

The basic antifouling function expression configuration in the electrochemical antifouling method according to the present invention is:
(1) Sterilization step: a step of sterilization by applying a positive potential that does not electrochemically generate a product from the electrolytic solution to the biofouling prevention electrode (+0 to 1.5 V vs SCE);
(2) Desorption step: A negative potential that does not electrochemically generate a product from the electrolyte is applied to the bioadhesion-preventing electrode to electrostatically function aquatic organisms and scales that directly or indirectly adhere to contact. (−0 to −0.6 V vs. SCE) desorbing by
(3) Washing and reducing step: Applying a negative potential to electrochemically generate a product from the electrolyte to the biofouling prevention electrode, and aquatic organisms and scales attached to and contacted with the biofouling prevention electrode by alkali decomposition Washing and reducing the surface of the biofouling prevention electrode (-0.6 to -2.0 V vs SCE);
(4) Decomposition cleaning reactivation process: A positive potential for electrochemically generating a product from the electrolyte is applied to the biofouling prevention electrode to adhere directly or indirectly to the biofouling prevention electrode surface. The contacted aquatic organism and scale are desorbed and decomposed by generation of chlorine compounds or radicals, the surface of the biofouling prevention electrode is cleaned and reactivated (positive potential higher than +1.5 V vs SCE),
Perform any process on the antifouling surface biofouling prevention electrode so that the load on the water and seawater caused by the most chemically generated chemical substances is minimal, and the long-term antifouling effect is stably obtained. Is.
However, these potentials can be changed by the biofouling prevention electrode used as the antifouling surface and the counter electrode material and the combination thereof, or the reference electrode for measuring the reference potential of water or seawater. For example, as a reference electrode, a reference electrode generally used for electrochemical measurement such as SCE (saturated citrus electrode) or Ag / AgCl (silver / silver chloride electrode) can be used.

Next, potential application conditions in each step will be described.
(1) Sterilization process When a positive potential is applied to the biological adhesion prevention electrode in water containing aquatic organisms, the aquatic organisms in the water are adsorbed on the surface of the biological adhesion prevention electrode. Further, the positive potential applied to the biofouling prevention electrode has an action of electrochemically sterilizing aquatic organisms adsorbed and brought into contact with the biofouling prevention electrode surface. That is, aquatic organisms are adsorbed on the surface of the biological adhesion preventing electrode by a positive potential and sterilized on the surface. At this time, the set potential is a potential at which no product is generated electrochemically from the electrolytic solution, and is a potential equal to or lower than the generation potential of oxygen and chlorine accompanying the decomposition of water and seawater.
The preferred potential is +0 to 1.5 V vs. SCE, more preferably +0.5 to +1.2 Vvs. SCE. However, this potential depends on the physical properties of the biofouling prevention electrode to be used. If the potential is lower than the generation potential of oxygen and chlorine accompanying water decomposition, contamination of water and seawater with electrolytic products will occur. Can be suppressed to a minimum, and a stable antifouling effect can be exhibited over a long period of time. Also, +0 Vvs. Aquatic organisms cannot be adsorbed on a substrate and sterilized if the direct electron transfer reaction with microorganisms is confirmed from SCE, but the potential is intermittently considered in consideration of deterioration and consumption of the biofouling prevention electrode. Is preferably varied.
The time for applying a positive potential at which no product is electrochemically generated from the electrolyte can be appropriately selected depending on the characteristics of the biofouling prevention electrode. In general, the antifouling effect is about 0.5 to 24 hours, even for several years, depending on the durability of the electrode for preventing biofouling and the amount of aquatic organisms that directly or indirectly contact the surface of the electrode for preventing biofouling. Is maintained as long as possible per unit time because the load on the water and seawater by the electrolytically generated chemical substance is small. Depending on the formation rate of the oxide depending on the biofouling prevention electrode, application for 0.1 to 1000 hours is more preferable.

(2) Desorption step Next, when a negative potential is applied to the surface of the biological adhesion prevention electrode, the aquatic organisms and scales that are in direct or indirect contact with each other are desorbed. The negative potential at which no product is electrochemically generated from the electrolyte is 0 to -1.0 Vvs. Ag / AgCl. Preferably, −0 to −0.6 Vvs. Ag / AgCl. At this time, aquatic organisms, other cells, sterilized aquatic organism cells and / or damaged or organic matter attached to the biofouling prevention electrode are not exposed to the surface of the biofouling prevention electrode due to electrostatic mechanisms or potential fluctuations. Desorbed due to fluctuations in pH and the like.
Furthermore, desorption and washing can be made more efficient by changing the potential at the negative potential. The width of the varying potential is preferably about −0.3 V to −0.9 V, and the period is preferably 10 Hz to 0.001 Hz.
The time for applying a negative potential at which no product is electrochemically generated from the electrolyte can be appropriately selected depending on the characteristics of the biofouling prevention electrode. Generally, it varies depending on the durability of the biofouling prevention electrode and the amount of aquatic organisms directly or indirectly in contact with the surface of the biofouling prevention electrode, but is preferably about 0.1 to 24 hours. In consideration of deterioration of the biofouling prevention electrode, application for 0.1 to 2 hours is more preferable.

(3) (Washing reduction process)
Furthermore, the negative potential at which an electrochemical product is generated from an electrolyte such as water or seawater is −1.0 Vvs. More negative potential than Ag / AgCl, preferably -1.0 V to -2.0 Vvs. It is about Ag / AgCl. By applying this negative potential, detachment of aquatic organisms, other cells, sterilized aquatic organism cells adhering to the biofouling prevention electrode, and / or their damaged or organic matter is promoted. When a negative potential is generated that electrochemically generates a product from the electrolyte, hydrogen is generated on the surface of the bioadhesion prevention electrode due to decomposition of the electrolyte, and this hydrogen deposits on the surface of the bioadhesion prevention electrode. This is because is removed. Further, the pH becomes alkaline in the vicinity of the biological adhesion preventing electrode. Furthermore, the precipitation of hydroxide may occur due to the strong alkali atmosphere, and it is necessary to appropriately select the potential to be applied and the application time. However, the organic substance is dissolved by the hydroxide. By removing and dissolving them, the surface of the biofouling prevention electrode is cleaned. In addition, it may be necessary to reduce the oxide on the surface of the biofouling prevention electrode, reduce the oxide that hinders the electron transfer reaction at the biofouling prevention electrode interface, and maintain and recover the function of the sterilization process. . Furthermore, desorption and washing can be made more efficient by changing the potential at the negative potential. The width of the changing potential is preferably about −0.3 V to −2 V, and the period is preferably 10 Hz to 0.001 Hz.
The time for applying a negative potential at which a product is generated electrochemically from the electrolyte can be appropriately selected depending on the characteristics of the biofouling prevention electrode. In general, it varies depending on the durability of the biofouling prevention electrode and the amount of aquatic organisms directly or indirectly in contact with the surface of the biofouling prevention electrode, but is preferably about 0.5 to 24 hours. In consideration of deterioration of the biofouling prevention electrode, application for 0.5 to 2 hours is more preferable.

(4) (Decomposition cleaning reactivation process)
The potential at which the product is electrochemically generated from the electrolyte is a potential at which oxygen or chlorine is generated as water or seawater decomposes, and is +1.5 Vvs. This is clearly confirmed by the potential exceeding Ag / AgCl. When these high potentials are applied for a long time, water and seawater are likely to electrolyze and generate chlorine and unknown substances, and the bioadhesion prevention electrode may deteriorate. In order to maintain a stable antifouling effect and to minimize contamination by water and electrolysis products in seawater, it may be inappropriate.
However, in the present invention aiming at antifouling for a long period of time, sterilized microorganisms, organic matter and scales that cannot be excluded even if various potentials are applied to the surface of the electrode for preventing biofouling that becomes the antifouling surface are adhered. In order to re-activate them and reproduce the antifouling effect for a long period of time without the cost of replacing electrodes for preventing biofouling, it is necessary to control the minimum chlorine compound and radical generation function. preferable.
By the way, when the physical property of the electrode for preventing biological adhesion is lower than the oxygen overvoltage, the generation of chlorine compound occurs, and in the opposite case, the phenomenon that oxygen is generated first can be confirmed.
The time for applying a positive potential for electrochemically generating a product from the electrolytic solution can be appropriately selected depending on the characteristics of the biofouling prevention electrode. In general, the durability of the biofouling prevention electrode varies depending on the amount of aquatic organisms that directly or indirectly contact the surface of the biofouling prevention electrode. It is preferable to make settings to minimize contamination by substances. Considering this point, it is more preferable to apply about 0.5 to 24 hours per month. Moreover, it is also possible to set and operate for the time of about 1/10 to 1 / 10,000 compared with the set time of the sterilization process of (1).

  In the present invention, in order to minimize contamination of water and seawater by chemical substances and maintain the antifouling effect over a long period of time, the above (1) sterilization step, (2) desorption step, (3) washing reduction step, (4) Each step of the decomposition cleaning reactivation step can be applied periodically in an arbitrary order and frequency according to the situation after appropriately setting the applied potential and the applied time.

Furthermore, the present invention can also use constant current control. The constant current control conditions are as follows.
For the expression of the antifouling effect due to the constant current, the setting of the current value can be appropriately changed depending on the material and shape of the biofouling prevention electrode and the purpose of the maintenance state of the biofouling prevention electrode. In general, a current value of 50 mA / m ² or more is effective and may be 1 A / m ² or less. Preferably, 100 mA / m ² or more and 1 A / m ² or less may be used when an effect is expected by utilizing the fact that a water splitting reaction is involved. In particular, it is preferable to output 100 to 400 mA / m ^{2 because} power consumption can be reduced and deterioration of the material of the bioadhesion preventing electrode functioning as an electrode can be suppressed, so that it can be used for a long time. In addition, each energization time can be appropriately selected and controlled depending on the purpose.
In addition, when the surface of the biofouling prevention electrode is oxidized and the output voltage becomes high, the current to be set is controlled positively and negatively for an arbitrary time to reduce the biofouling prevention electrode and lower the output voltage. Can be kept in a state. However, if the time during which a negative current is passed at a constant current is too long, the effect of preventing aquatic organism adhesion may be reduced. The negative current value is also preferably selected and used depending on the biological adhesion preventing electrode.

Similarly, when performing constant current control in the removal control when the aquatic organism has adhered, in order to expect the manifestation of the effect by utilizing the water splitting reaction, 400 mA / m ² or more is required. is necessary. Moreover, if it outputs exceeding 1000 mA / m < ² >, it is unpreferable at the point of the reduction of power consumption or the material deterioration of the electroconductive base material which functions as an electrode. Therefore, in order to long-term ^available, good minimum period of operation to the extent that the effect in the range of 400mA / ^{m 2} ~1000mA / m 2 is confirmed. Furthermore, when a period during which a lot of aquatic organisms are observed is determined, it is preferable to perform removal control from about one month before that period. Moreover, when combined with positive / negative reversal control, accumulation of inorganic substances existing in water on the electrode surface can be prevented and efficiently removed. For the control, it is preferable to appropriately select the adjustment ratio of the current amount as the polarity conversion time and the reaction amount. Furthermore, when determining the control process throughout the year, it is possible to combine the process of controlling the prevention of attachment of aquatic organisms and the process of removal control.

  The electrolyte solution that can be treated according to the present invention is not particularly limited as long as it is water containing organisms. For example, seawater, river water, lake water, tap water, drinking water, or various buffer solutions may be used. In addition, the target organism is not particularly limited as long as it is an organism present in the water.

  The biofouling prevention electrode according to the present invention is a biofouling prevention device comprising at least a biofouling prevention electrode, a counter electrode, and a power source for applying a voltage between the biofouling prevention electrode and the counter electrode. A biofouling prevention electrode for use in an electrochemical antifouling method utilizing a direct electron transfer reaction between a biofouling prevention electrode and a living organism, wherein the biofouling prevention electrode is an electrode substrate made of titanium or a titanium alloy. Biological adhesion characterized by carrying a mixed oxide of 35 to 65 mol% iridium oxide and 65 to 35 mol% tantalum oxide based on metal on a conductive titanium oxide layer provided on the surface Since the electrode is a prevention electrode, the power supply applies at least a positive potential that does not electrochemically generate a product from the electrolyte to the organism adhesion prevention electrode. It is possible to inhibit the growth of direct or indirect contact to aquatic organisms on the surface. An aquatic that includes a biofouling prevention electrode, a counter electrode, and a power source that applies a voltage between the biofouling prevention electrode and the counter electrode, and that directly or indirectly contacts the surface of the biofouling prevention electrode. A positive potential for electrochemically generating a product from the electrolyte is applied to the biofouling prevention electrode by an electrochemical antifouling device that controls a direct electron transfer reaction between the living organism and the biofouling prevention electrode. Thus, it is possible to set a process for desorbing and cleaning aquatic organisms and scales that directly or indirectly contact the surface of the biofouling prevention electrode and reactivating the biofouling prevention electrode, and the electrochemical antifouling device. Is a positive potential at which no electrochemical product is generated from the electrolyte, a negative potential at which no electrochemical product is generated from the electrolyte, and an electrochemical from the electrolyte. To product Negative potential and can be arbitrarily set can and periodically applied to occur.

Hereinafter, the present invention will be described in more detail with reference to examples.
FIG. 1 is a schematic view of an apparatus used in the following examples.
In the test tank 6, the biological adhesion preventing electrode 3, the reference electrode 4, and the counter electrode 5 are arranged. The potentiostat 2 is individually connected to each of the biofouling prevention electrode 3, the reference electrode 4, and the counter electrode 5. The test tank 6 contains sterilized seawater, and a stirrer 8 and a stirring bar 7 are disposed at the bottom thereof. A silver / silver chloride electrode (Ag / AgCl) was used for the reference electrode 4, and an electrode formed of a conductive material was used for the counter electrode 5.
The control unit 1 outputs an instruction value of the potential applied to the reference electrode 4 of the biofouling prevention electrode 3 in an analog manner, and the potentiostat 2 converts the potential of the biofouling prevention electrode 3 to the reference electrode 4 into an instruction value input in an analog manner. Thus, a voltage is output to the biological adhesion preventing electrode 3 and the counter electrode 5. In order to change the potential, the control unit 1 outputs an analog output of the indication value of the applied potential with a time resolution of at least 100 Hz, preferably 1 kHz or more. Furthermore, the potentiostat 2 responds to the analog input value of the potential accordingly with a response performance of at least 100 Hz, preferably 1 kHz or more.
The control unit 1 includes a circuit configured by a CPU, an input / output port, a digital / analog converter, and a memory (not shown) such as a ROM or a RAM. A control program and a timing chart for control to be described later are incorporated in the ROM, and the CPU converts the potential indication value into an analog value by a digital / analog converter according to the control program and the timing chart, and outputs the result to the potentiostat 2. . By using a one-chip computer incorporating the above-described components in the control unit 1, the overall circuit configuration can be simplified and made inexpensive.

Next, the potential control timing chart shown in FIGS. 2 to 6 will be described in detail. In the timing chart, the horizontal axis indicates time, and the vertical axis indicates an indication value of the potential of the biological adhesion preventing electrode 3 with respect to the reference electrode 4. Here, a combination of the following four types of steps (six potential application steps) is explicitly illustrated as a timing chart, but other steps depending on how to apply a potential are not specifically excluded.
(1) (Sterilization step) Positive potential application step (T1) that does not generate an electrochemical product: A step of applying a positive potential lower than the positive potential side electrolysis product generation potential 9. The potential value to be applied can be changed depending on the process.
(2) (Desorption step) Negative potential application step (T2) that does not generate electrochemical products or amplitude potential application step (T3) in a negative potential region that does not generate electrochemical products: Both steps are negative A negative potential higher than the potential side electrolytic product generation potential 10 is applied. In the amplitude potential application step (T3), the applied potential is changed almost continuously. Depending on the responsiveness of the system, it is possible to give a potential changed in a trapezoidal wave instead of a triangular wave as the indication potential.
(3) (Washing reduction step) A negative potential applying step (T4) for generating an electrochemical product, or an amplitude potential applying step in a negative potential region where an electrochemical product is generated and / or a negative potential region where no electrochemical product is generated ( T5): In both steps, a negative potential lower than the negative potential side electrolysis product generation potential 10 is applied.
(4) (Decomposition cleaning reactivation step) Positive potential application step (T6) for generating an electrochemical product: A positive potential higher than the positive side electrolysis product generation potential 9 is applied.
In the potential application pattern shown in the timing chart of FIG. 2, the positive potential application step (T1) that does not generate an electrochemical product and the positive potential application step (T6) that generates an electrochemical product are alternately repeated. The application potential and application period of each process can be determined appropriately according to the case. For example, a pattern in which a plurality of different potential values are applied in the positive potential application process (T1) that does not generate an electrochemical product can be created. It is.
In the potential application pattern shown in the timing chart of FIG. 3, a positive potential application step (T1) that does not generate an electrochemical product, a negative potential application step (T2) that does not generate an electrochemical product, and an electrochemical product. The positive potential applying step (T6) for generating is alternately repeated. The applied potential and the application period in each step can be appropriately determined according to circumstances, and the order and frequency are also arbitrary. For example, a positive potential application step (T1) that does not generate an electrochemical product and a negative potential application step (T2) that does not generate an electrochemical product are alternately repeated a certain number of times, and then an electrochemical product is generated. A pattern of applying the positive potential applying step (T6) can be created.
In the potential application pattern shown in the timing chart of FIG. 4, a positive potential application step (T1) that does not generate an electrochemical product, an amplitude potential application step (T3) in a negative potential region that does not generate an electrochemical product, and The positive potential application step (T6) for generating the electrochemical product is repeated alternately. The applied potential and the application period in each step can be appropriately determined according to circumstances, and the order and frequency are also arbitrary. The amplitude and change rate of the potential in the amplitude potential application step (T3) in the negative potential region where no electrochemical product is generated should be set within a range in which the controller 1 can output, although it depends on the responsiveness of the system. Can do. As in FIG. 3, for example, a positive potential applying step (T1) that does not generate an electrochemical product and an amplitude potential applying step (T3) in a negative potential region that does not generate an electrochemical product are alternately repeated a certain number of times. Then, it is also possible to create a pattern in which a positive potential application step (T6) for generating an electrochemical product is applied.

In the potential application pattern shown in the timing chart of FIG. 5, a positive potential application step (T1) that does not generate an electrochemical product, a negative potential application step (T2) that does not generate an electrochemical product, and an electrochemical product The negative potential applying step (T4) to be generated and the positive potential applying step (T6) to generate the electrochemical product are alternately repeated. The applied potential and the application period in each step can be appropriately determined according to circumstances, and the order and frequency are also arbitrary. For example, a positive potential application step (T1) that does not generate an electrochemical product and a negative potential application step (T2) that does not generate an electrochemical product are alternately repeated a certain number of times, and then an electrochemical product is generated. A pattern of applying a negative potential applying step (T4) and a positive potential applying step (T6) for generating an electrochemical product can be created.
In the potential application pattern shown in the timing chart of FIG. 6, a positive potential application step (T1) that does not generate an electrochemical product, a negative potential region that generates an electrochemical product, and / or an amplitude in a negative potential region that does not generate an electrochemical product. The potential application step (T5) and the positive potential application step (T6) for generating an electrochemical product are alternately repeated. The applied potential and the application period in each step can be appropriately determined according to circumstances, and the order and frequency are also arbitrary. The amplitude and change rate of the potential in the amplitude potential application step (T5) in the negative potential region where the electrochemical product is generated / not generated are set in a range that can be output by the control unit 1 depending on the response of the system. can do. For example, a positive potential application step (T1) that does not generate an electrochemical product and an amplitude potential application step (T5) in a negative potential region that does or does not generate an electrochemical product are repeated a certain number of times, and thereafter A pattern of applying a positive potential applying step (T6) for generating an electrochemical product can be created.

The preparation procedure of Examples 1-3 and Comparative Examples 1-4 is shown below.
<Preparation of biological adhesion prevention electrode>

Example 1
A titanium base material (t0.5 × 100 × 100 mm) corresponding to JIS type 2 was degreased and washed with ethyl alcohol and then treated in an aqueous solution containing 8 wt% hydrofluoric acid and 6 wt% lactic acid at 20 ° C. for 1 minute. . The titanium substrate was taken out of the sulfuric acid solution and washed with water in the atmosphere. Moreover, the average roughness (Ra) of the titanium base material surface at this time was 0.3 micrometer. Next, heat treatment was performed in the atmosphere at 400 ° C. for 30 minutes to form a conductive titanium oxide layer. Then each dissolved chloroiridic acid _{(H 2 IrCl 6 · 6H 2} O) and tantalum ethoxide _{(Ta (OC 2 H 5)} 5) to butanol, 60 mol% of iridium oxide composition ratio is based on metal conversion And 40 mol% tantalum oxide, and a total amount of iridium (Ir) and tantalum (Ta) metal concentration of 50 g · dm ⁻³ is weighed to 0.4 cm ³ per dm ² with a measuring pipette. Then, it was coated on the titanium substrate, dried at room temperature for 20 minutes, and then baked in air at 530 ° C. for 10 minutes. Loading of iridium oxide and tantalum oxide each in terms of metal ^{0.020 g} · dm -2, was 0.014 g · ^{dm -2.} In the above steps, a conductive titanium oxide layer was formed on the surface of the titanium base material, and a mixed oxide of 60 mol% iridium oxide and 40 mol% tantalum oxide based on metal conversion was supported thereon. The bioadhesion-preventing electrode 3 of Example 1 was produced.

Example 2
The same base material as in Example 1 and the same pretreatment were performed to prepare a titanium base material on which a conductive titanium oxide layer having an average roughness (Ra) of the base material surface of 0.3 μm was formed. Then, iridium oxide and respectively ^{0.017 g} · dm supported amount in terms of metal of tantalum oxide -2 except that the 0.018 g · ^{dm -2} in the same manner as in Example 1, on a titanium substrate surface, conductive The bioadhesion-preventing electrode 3 of Example 2 was produced, in which a porous titanium oxide layer was formed, and a mixed oxide of 50 mol% iridium oxide and 50 mol% tantalum oxide based on metal was supported thereon.

Example 3
The same base material as in Example 1 and the same pretreatment were performed to prepare a titanium base material on which a conductive titanium oxide layer having an average roughness (Ra) of the base material surface of 0.3 μm was formed. Then, iridium oxide and respectively ^{0.013 g} · dm supported amount in terms of metal of tantalum oxide -2 except that the 0.021 g · ^{dm -2} in the same manner as in Example 1, on the titanium substrate surface oxidation A titanium layer was formed, and the bioadhesion-preventing electrode 3 of Example 3 was produced, on which a mixed oxide of 40 mol% iridium oxide and 60 mol% tantalum oxide based on metal conversion was supported.

Example 4
A titanium substrate (t0.5 × 100 × 100 mm) corresponding to JIS type 2 was degreased and washed with ethyl alcohol, and then treated in an aqueous solution containing 8 wt% hydrofluoric acid and 6 wt% lactic acid at 20 ° C. for 2 minutes. . The titanium substrate was taken out of the sulfuric acid solution and washed with water in the atmosphere. Moreover, the average roughness (Ra) of the titanium base material surface at this time was 0.2 micrometer. Next, heat treatment was performed in the atmosphere at 400 ° C. for 30 minutes to form a conductive titanium oxide layer. Then each dissolved chloroiridic acid _{(H 2 IrCl 6 · 6H 2} O) and tantalum ethoxide _{(Ta (OC 2 H 5)} 5) to butanol, 60 mol% of iridium oxide composition ratio is based on metal conversion And 40 mol% tantalum oxide, and a total amount of iridium (Ir) and tantalum (Ta) metal concentration of 50 g · dm ⁻³ is weighed to 0.4 cm ³ per dm ² with a measuring pipette. Then, it was coated on the titanium substrate, dried at room temperature for 20 minutes, and then baked in air at 530 ° C. for 10 minutes. Loading of iridium oxide and tantalum oxide each in terms of metal ^{0.020 g} · dm -2, was 0.014 g · ^{dm -2.} In the above steps, a conductive titanium oxide layer was formed on the surface of the titanium base material, and a mixed oxide of 60 mol% iridium oxide and 40 mol% tantalum oxide based on metal conversion was supported thereon. The bioadhesion-preventing electrode 3 of Example 4 was produced.

Example 5
A titanium substrate (t0.5 × 100 × 100 mm) corresponding to JIS type 2 was degreased and washed with ethyl alcohol, treated in an 8 wt% hydrofluoric acid aqueous solution at 20 ° C. for 1 minute, and then rotated at a rotational speed of 300 rpm. After buffing for a minute, it was degreased and washed with ethyl alcohol. Further, the average roughness (Ra) of the substrate surface at this time was 0.1 μm. Next, in the same manner as in Example 1, a conductive titanium oxide layer was formed on the surface of the titanium substrate, and a mixed oxide of 60 mol% iridium oxide and 40 mol% tantalum oxide based on metal conversion was formed thereon. The supported bioadhesion preventing electrode 3 of Example 5 was produced.

Comparative Example 1
A titanium substrate (t0.5 × 100 × 100 mm) corresponding to JIS type 2 was degreased and washed with ethyl alcohol, treated in an 8 wt% hydrofluoric acid aqueous solution at 20 ° C. for 2 minutes, and then 60 wt% at 120 ° C. Treated with aqueous sulfuric acid for 3 minutes. The titanium substrate was taken out of the sulfuric acid solution and washed with water in the atmosphere. Moreover, the average roughness (Ra) of the titanium base material surface at this time was 0.6 micrometer. Then, chloroplatinic acid _{(H 2 PtCl 6 · 6H 2} O), iridium acid _{(H 2 IrCl 6 · 6H 2} O) chloride and tantalum ethoxide _{(Ta (OC 2 H 5)} 5) and then individually dissolved in butanol The composition of the supported material is composed of platinum of 70 mol%, 11 mol% of iridium oxide and 19 mol% of tantalum oxide, and a metal of platinum (Pt), iridium (Ir) and tantalum (Ta). A solution having a total concentration of 70 g · dm ⁻³ was weighed by a 0.4 cm ³ solution per 1 dm ² with a measuring pipette, coated on the titanium substrate, dried at room temperature for 20 minutes, and then in the atmosphere. Baked at 10 ° C. for 10 minutes. The supported amounts of platinum, iridium oxide, and tantalum oxide were 0.02 g · dm ⁻² , 0.003 g · dm ⁻² , and 0.005 g · dm ⁻² , respectively, in terms of metal. Through the above steps, a conductive titanium oxide layer is formed on the surface of the titanium substrate, and a mixed oxidation of 70 mol% platinum, 11 mol% iridium oxide and 19 mol% tantalum oxide based on metal conversion is formed thereon. A biological adhesion preventing electrode 3 of Comparative Example 1 on which an object was carried was produced.

Comparative Example 2
A titanium substrate (t0.5 × 100 × 100 mm) corresponding to JIS type 2 was degreased and washed with ethyl alcohol, treated in an 8 wt% hydrofluoric acid aqueous solution at 20 ° C. for 1 minute, and then 60 wt% at 120 ° C. Treated with aqueous sulfuric acid for 20 seconds. The titanium substrate was taken out of the sulfuric acid solution and washed with water in the atmosphere. Moreover, the average roughness (Ra) of the titanium base material surface at this time was 0.6 micrometer. Then each dissolved chloroplatinic acid _{(H 2 PtCl 6 · 6H 2} O) in butanol, 0.4 cm per 1dm2 solution sum is 50 g · ^{dm -3} of metal concentration in the measuring pipette platinum (Pt) ^Three weighed samples were coated on the titanium substrate, dried at room temperature for 20 minutes, and then fired at 400 ° C. for 10 minutes in the air. The amount of platinum supported was 0.02 g · dm ⁻² in terms of metal. Through the above steps, a conductive titanium oxide layer was formed on the surface of the titanium base material, and the bioadhesion prevention electrode 3 of Comparative Example 2 in which platinum was supported thereon was produced.

Comparative Example 3
The same base material as in Example 1 and the same pretreatment were performed to prepare a titanium base material on which a conductive titanium oxide layer having an average roughness (Ra) of the base material surface of 0.3 μm was formed. Then, iridium oxide and respectively ^{0.027 g} · dm supported amount in terms of metal of tantalum oxide -2 except that the 0.007 g · ^{dm -2} in the same manner as in Example 1, on a titanium substrate surface, conductive The bioadhesion-preventing electrode 3 of Comparative Example 3 was produced, in which a porous titanium oxide layer was formed, and a mixed oxide of 80 mol% iridium oxide and 20 mol% tantalum oxide based on metal conversion was supported thereon.

Comparative Example 4
The same base material as in Example 1 and the same pretreatment were performed to prepare a titanium base material on which a conductive titanium oxide layer having an average roughness (Ra) of the base material surface of 0.3 μm was formed. Then, iridium oxide and respectively ^{0.006 g} · dm supported amount in terms of metal of tantalum oxide -2 except that the 0.028 g · ^{dm -2} in the same manner as in Example 1, on a titanium substrate surface, conductive The bioadhesion-preventing electrode 3 of Comparative Example 4 was produced, in which a porous titanium oxide layer was formed, and a mixed oxide of 20 mol% iridium oxide and 80 mol% tantalum oxide based on metal was supported thereon.

<Durability verification in electrochemical control of biofouling prevention electrode>
Repeated in the pattern shown in the timing chart shown in FIG. 6 as a potential application pattern using the bioadhesion prevention electrodes 3 of Examples 1 to 5 and Comparative Examples 1 to 4 prepared above, 3% sodium chloride aqueous solution (25 ° C.) Among them, the reference electrode was an Ag / AgCl electrode, and the potential consumption was measured after applying the potential for 1848 hours. The supported amount is measured by using a fluorescent X-ray film thickness meter (Seiko Instruments Inc., SFT-3300) before and after the biological adhesion preventing electrode 3 is tested, and the X-ray intensity obtained from the coating component is used. Indirectly from the calibration curve.
The potential application conditions in FIG. 6 are as follows.
T1: 0.9Vvs. Ag / AgCl, 270 sec applied T5: -0.3 to -0.9 Vvs. Ag / AgCl amplitude is applied for 46 sec. T6: 1.1 Vvs. Ag / AgCl, 15 sec applied

  From the results shown in Table 1, it can be seen that Examples 1 to 5 consume less amount of the loaded material than Comparative Examples 1 to 4. From this, it was confirmed that the bioadhesion prevention electrode of the present invention has high durability in electrochemical control. In Comparative Example 4, there was no major problem from the point of consumption.

<Preparation of microorganism suspension>
After primary culture of marine-adherent bacteria Vibrio alginoliticus (ATCC17749) at 30 ° C. in marine broth (Marine broth) 2216 (manufactured by DIFCO Laboratories), 100 microliters were collected and cultured in a 25 ml centrifuge tube (marine). Broth was aerobically cultured at 30 ° C. and 150 rpm for 2 hours. The cultured cells are collected by centrifugation, then washed with sterilized seawater and suspended in sterilized seawater. The number of bacteria is counted with a hematite meter, and a cell suspension with a concentration of 1 × 10 ⁷ cells / milliliter is obtained. Produced.

<Attachment of microorganisms to the electrode for preventing biofouling and potential application>
The bioadhesion-preventing electrodes 3 of Examples 1, 3, 5 and Comparative Example 4 were immersed in a suspension stirred at 200 rpm for 90 minutes at room temperature, and the cells were adhered to the surface of the bioadhesion-preventing electrode. . It was immersed in sterilized seawater contained in the test tank 6, and various potentials were applied while stirring the sterilized seawater at a stirring speed of 200 rpm. As the potential application condition, each pattern shown in FIGS. Further, the potential of T1 was 0.9 V vs Ag / AgCl and applied for 60 minutes. The potential of T2 was −0.6 V vs Ag / AgCl and applied for 30 minutes. The potential of T3 was −0.3 V to −0.6 V vs Ag / AgCl, applied for 30 minutes, and the potential was amplified at intervals of 2 minutes. The potential of T4 was −1.4 V vs. Ag / AgCl and applied for 60 minutes. The potential of T5 was −0.3 V to −1.4 V vs. Ag / AgCl, applied for 60 minutes, and the potential was amplified at intervals of 2 minutes. The potential of T6 was applied at 1.6 V vs Ag / AgCl for 5 minutes.

<Evaluation of sterilization of microorganisms and determination of effects of each process>
The confirmation of the bactericidal effect, the detachment of dead attached microorganisms, and the determination of the cleaning effect were carried out by the double staining method of Propidium Iodide (PI) and 4,6-Diamidino-2-Phenylindole (DAPI). PI and DAPI are microorganisms that adhere to nucleic acid of microorganisms due to the difference in the permeability of microorganisms to the cell membrane. Those that show blue fluorescence are live cells, and those that show red fluorescence are dead cells. in use. In addition, by comparing the abundance of the sterilized red-fluorescent microorganisms on the surface of the bioadhesion preventing electrode, the detachment of scales and organic substances and the cleaning function were determined.
For staining of microorganisms, the electrode 3 for preventing bioadhesion to which a potential is applied is washed with sterilized seawater, and the adherent cells on the electrode for preventing bioadhesion are PI 250 μg / ml aqueous solution, DAPI 20 μg / ml aqueous solution (adjusted before staining). 30 μl of each was added dropwise. Thereafter, ultraviolet excitation light is irradiated, and under the observation of a fluorescence microscope, those that show blue fluorescence are viable cells and those that show red fluorescence are dead cells. It was evaluated by the number of dead cells relative to the number of cells adsorbed on the surface.
In the determination, ◯ indicates a sterilization rate of 80% or more, Δ indicates a sterilization rate of 20 to 80%, and x indicates a sterilization rate of less than 20%.

In the potential application patterns of FIGS. 2 to 6, the sterilizing effect of the microorganisms was determined after completing the T1 step. The determinations of the detachment steps T2 and T3 are as follows: the attached organism amount after applying the potential is a decrease ratio from the T1 step after the sterilization determination. The reduction rate was shown as less than 30%. The determination of the T4, T5, and T6 steps was determined based on the state of each pattern before the T4, T5, and T6 steps and the presence or absence of dead cells after each step.
In order to determine the superiority of the test results, various times were applied for the potential application time and the applied voltage. Therefore, it is desirable to give priority to the test results in consideration of the total results in a short time and at a completely low potential, and the present invention is not limited to this embodiment and application examples.
The effects of Examples 1, 3, 5 and Comparative Example 4 in the steps of FIGS.

Application example 1
When the examples 1, 3, 5 and comparative example 4 are used as the biological adhesion preventing material 3 of the apparatus (see FIG. 1), and the potential application pattern shown in the timing chart shown in FIG. The sterilization rate in the T1 step and the cleaning rate in the T6 step were determined. The results are shown in Table 2.
In the T1 step, 0.9VvsAg / AgCl was applied for 60 minutes to determine the bactericidal efficiency. In addition, the number of dead cells attached only in the T1 step and the presence or absence of dead cells regarded as organic matter attached after the T6 step was applied at 1.0 V vs Ag / AgCl for 5 minutes, and washed by decomposition. The effect was judged.

In the determination of the bactericidal effect, ◯ indicates a sterilization rate of 80% or more, Δ indicates a sterilization rate of 20 to 80%, and x indicates less than 20%.
The degradation cleaning effect indicates the presence or absence of adherent dead cells, ◯ indicates a cleaning rate of 80% or more, Δ indicates a cleaning rate of 20 to 80%, and X indicates a cleaning rate of less than 20%.

Application example 2
Examples 1, 3, 5 and Comparative Example 4 are used as the biological adhesion preventing material 3 of the apparatus (see FIG. 1), and the potential application pattern shown in the timing charts shown in FIGS. The desorption rate in the T2 and T3 steps was determined. The results are shown in Table 3.
Since the bactericidal effect showed almost the same bactericidal efficiency as in Application Example 1, 0.9VvsAg / AgCl was applied for 15 minutes in the T1 step, and dead and live bacteria were mixed to prevent adhering organisms. The electrode 3 was adjusted. Thereafter, the T2 potential in FIG. 3 is applied at −0.6 V vs Ag / AgCl for 30 minutes, and the T3 potential in FIG. 4 is applied at −0.3 V to −0.6 V vs Ag / AgCl for 30 minutes. Amplified at minute intervals. Before and after the T2 step and T3 step at that time, the number of detached microorganisms was compared with the number of attached microorganisms, which is the sum of dead bacteria and viable bacteria, and the reduction ratio was determined to determine the detachment effect.

  The decrease rate is indicated by O as 70% or more, Δ as 30 to 70%, and X as less than 30%. In addition, the cleaning effect could be confirmed in all of the biological adhesion prevention electrodes 3 that subsequently performed the T6 step, and the cleaning promotion effect by the combination could be expected.

Application example 3
Examples 1, 3, 5 and Comparative Example 4 are used as the biological adhesion preventing material 3 of the apparatus (see FIG. 1), and the potential application pattern shown in the timing charts shown in FIGS. The cleaning rate in the T4 and T5 processes was determined. The results are shown in Table 4.
Since the bactericidal effect showed almost the same bactericidal efficiency as Example 1, 0.9VvsAg / AgCl was applied for 15 minutes in the T1 step, and dead and live bacteria were mixed to prevent adhering organisms. The electrode 3 was adjusted. Thereafter, the T2 potential was -0.6 V vs Ag / AgCl and applied for 30 minutes. Next, the electric setting of T4 was set to -1.4 V vs Ag / Ag Cl for 10 minutes. Further, the potential setting of T5 was −0.3 V to −1.4 V vs Ag / AgCl applied for 10 minutes, and the potential was amplified at intervals of 2 minutes. Before and after the T4 and T5 steps, the degradation and cleaning effect was determined by the presence or absence of dead cells regarded as attached organic matter.

The results are shown in Table 4 (◯: reduction rate of 70% or more, Δ: reduction rate of 30 to 70%, x: reduction rate of less than 30%).
The degradation cleaning effect indicates the presence or absence of adherent dead cells, ◯ indicates a cleaning rate of 80% or more, Δ indicates a cleaning rate of 20 to 80%, and X indicates a cleaning rate of less than 20%. Moreover, when T6 process was implemented after that, almost perfect cleaning effect could be confirmed with all the biological adhesion prevention electrodes 3 in a short time, and the cleaning promotion effect by the combination was expectable.

<Verification of biological adhesion prevention by controlling the potential of biological adhesion prevention electrodes in the actual ocean>
Application example 4
The biological adhesion prevention electrode 3 (t0.5 × W750 × L450 mm) treated in the same manner as in Example 1 is installed in an actual ocean structure, and the timing chart shown in FIG. , T6 was deleted) for 6 months. At this time, the counter electrode 2 was iron (SS400, t10 × w20 × L300 mm), and the reference electrode 3 was a silver / silver chloride electrode.
Control condition T1: 0.9 Vvs. Applied for 180 minutes at Ag / AgCl T4: -0.0 to -0.1 Vvs. Apply for 20 minutes while amplifying Ag / AgCl in 2 minute period

Six months later, the surface of the biofouling prevention electrode 3 that had been treated in the same manner as in Example 1 was free from marine biofouling and contamination. Also, the output voltage was stable without change.

Application example 5
<Verification of biological adhesion prevention by current control of biological adhesion prevention electrode in actual ocean>
The bioadhesion prevention electrode 3 (t0.5 × W750 × L450 mm) treated in the same manner as in Example 1 is installed in an actual marine structure, and the following control conditions 1, 2, 5 are used using a DC power supply. 6 and Comparative Control Condition 1 were conducted for 6 months. At this time, the counter electrode 2 was iron (SS400, t10 × w20 × L300 mm), and the reference electrode 3 was a silver / silver chloride electrode.
After 6 months, the surface of the conductive substrate was visually evaluated and the change in the output voltage was observed.
Control condition 1: 50 mA / m ² always energized.
Control condition 2: 100 mA / m ² always energized.
Control conditions 5: 50mA / ^{m 2} at 180 minutes after energization by the polarity conversion -10 mA / ^{m 2} repeated 20 minutes energization.
Control conditions 6: 100mA / ^{m 2} at 180 minutes after energization by the polarity conversion -10 mA / ^{m 2} repeated 20 minutes energization.

  The results are shown in Table 5 (◯: no adhesion, Δ: some adhesion, x: adhesion). Under the control conditions 1, 2, 5, and 6 of the application example 5, after 6 months, the surface of the biofouling prevention electrode 3 subjected to the same treatment as that of the example 1 was free from marine organisms and contamination. Also, the output voltage was stable without change.

<Verification of biofouling prevention by controlling the potential of the biofouling prevention electrode in fresh water>
Application example 6
The biological adhesion prevention electrode 3 (t0.5 × W750 × L450 mm) treated in the same manner as in Example 1 is installed in a river structure in a place with a large flow, and a timing chart shown in FIG. (However, T6 was deleted) for 6 months. At this time, the counter electrode 2 was iron (SS400, t10 × w20 × L300 mm), and the reference electrode 3 was a silver / silver chloride electrode.
Control condition T1: 2.0 Vvs. Applied for 180 minutes at Ag / AgCl T4: -0.0 to -0.1 Vvs. Apply for 20 minutes while amplifying Ag / AgCl in 2 minute period

After 6 months, the surface of the bioadhesion-preventing electrode 3 that had been treated in the same manner as in Example 1 was free from adhesion and contamination of the chickenpox insect, its larva, or its nest. Also, the output voltage was stable without change.
In addition, the same effect was obtained when the biofouling prevention electrode 3 that was treated in the same manner as in Example 1 on the lakeside with little or almost no flow in the installation location under the same conditions as in Application Example 6.

Application example 7
<Verification of biofouling prevention by current control of freshwater electrodes for biofouling>
The biological treatment preventing electrode 3 (t0.5 × W750 × L450 mm) treated in the same manner as in Example 1 is installed in a river structure in a place with a large flow, and a control condition 1 shown below using a DC power supply device The energization test was carried out for 6 months under -8 and comparative control condition 1. At this time, the counter electrode 2 was iron (SS400, t10 × w20 × L300 mm), and the reference electrode 3 was a silver / silver chloride electrode. After 6 months, the surface of the conductive substrate was visually evaluated and the change in the output voltage was observed.
Control condition 1: 50 mA / m ² always energized.
Control condition 2: 100 mA / m ² always energized.
Control condition 3: 200 mA / m ² always energized.
Control condition 4: 300 mA / m ² always energized.
Control conditions 5: 50mA / ^{m 2} at 180 minutes after energization by the polarity conversion -10 mA / ^{m 2} repeated 20 minutes energization.
Control conditions 6: 100mA / ^{m 2} at 180 minutes after energization by the polarity conversion -10 mA / ^{m 2} repeated 20 minutes energization.
Control conditions 7: 200mA / ^{m 2} at 180 minutes after energization by the polarity conversion -10 mA / ^{m 2} repeated 20 minutes energization.
Control conditions 8: 300mA / ^{m 2} at 180 minutes after energization by the polarity conversion -10 mA / ^{m 2} repeated 20 minutes energization.

The results are shown in Table 6 (◯: no adhesion, Δ: some adhesion, x: adhesion). Under the control conditions 1 to 8 of Application Example 6, after 6 months, the surface of the biofouling prevention electrode 3 that had been treated in the same manner as in Example 1 was attached to the surface of aquatic insects, their larvae, or their nests and soiled There was no dust adsorbed on the nest. Also, the output voltage was stable without change.
In addition, the same effect was obtained when the biofouling prevention electrode 3 that was treated in the same manner as in Example 1 on the lakeside with little or almost no flow in the installation location under the same conditions as in Application Example 7.

Application example 8 (confirmation of chlorine generation)
The biological adhesion prevention electrode 3 obtained in Example 1 was immersed in 50 ml of seawater, and 0.80 to 1.1 Vvs. The chlorine concentration in seawater when each potential was applied for 30 minutes every 0.05 V in Ag / AgCl was measured. The chlorine concentration in seawater to which a potential was applied was measured using a residual chlorine electrode (97 · 70BN; manufactured by Orion Research). Ten milliliters of seawater after the potential application was sampled, and 100 microliters of iodine reagent (manufactured by Orion Research) and acid reagent (manufactured by Orion Research) were added and stirred. After the solution was allowed to stand for 2 minutes, a multimeter (83 MULTITIMER; manufactured by FLUKE) was connected, the potential was measured with a residual chlorine electrode, and the chlorine concentration was determined using a calibration curve from the electrode potential difference from the standard sample. The chlorine measurement limit is 0.2 ppm. A standard sample was prepared by adding 100 microliters of residual chlorine standard solution (manufactured by Orion Research), iodine reagent, and acid reagent, respectively, and stirring for 2 minutes, and then adding 9900 microliters of distilled water and stirring again. As a result, chlorine was 1.0 Vvs. Confirmed from Ag / AgCl. From this result, it was confirmed that the antifouling effect of this application example was not sterilization derived from the product of the electrolytic reaction with chlorine or the like.

As described above, the bioadhesion-preventing electrode according to the present invention has a conductive titanium oxide layer on the portion of the substrate made of titanium or titanium alloy that requires bioadhesion prevention, and is 35 to 65 based on metal conversion. Since it carries mol% iridium oxide and 65 to 35 mol% tantalum oxide, it is possible to stably obtain an electrochemical antifouling effect over a long period of time.

Schematic diagram of the apparatus of the example Potential control timing chart Potential control timing chart Potential control timing chart Potential control timing chart Potential control timing chart

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Control part 2 Potentiostat 3 Electrode for biological adhesion prevention 4 Reference electrode 5 Counter electrode 6 Test tank 7 Stirring rod 8 Stirrer 9 Positive potential side electrolysis product generation potential 10 Negative potential side electrolysis product generation potential T1 Electrochemical product Positive potential application step T2 that does not generate electrochemical potential negative potential application step T3 that does not generate electrochemical product Amplitude potential application step T4 in the negative potential region that does not generate electrochemical product T4 negative potential application that generates electrochemical product Step T5 Amplitude potential application step T6 in the negative potential region that generates / does not generate an electrochemical product T6 Positive potential application step that generates an electrochemical product

Claims (1)

In an electrochemical antifouling apparatus comprising a biofouling prevention electrode, a counter electrode, and a power source for applying a voltage between the biofouling prevention electrode and the counter electrode, the biofouling prevention electrode and the living organism directly An electrode for preventing biofouling used in an electrochemical antifouling method using an electron transfer reaction, wherein the biofouling preventive electrode is formed on a conductive titanium oxide layer provided on the surface of an electrode substrate made of titanium or a titanium alloy. A bioadhesion-preventing electrode characterized in that it carries a mixed oxide of 35 to 65 mol% iridium oxide and 65 to 35 mol% tantalum oxide based on metal conversion.

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