CN111206278A - Method for removing electrode surface deposits containing lead compound from electrolytic electrode to which lead compound has adhered - Google Patents
Method for removing electrode surface deposits containing lead compound from electrolytic electrode to which lead compound has adhered Download PDFInfo
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- CN111206278A CN111206278A CN201911071414.2A CN201911071414A CN111206278A CN 111206278 A CN111206278 A CN 111206278A CN 201911071414 A CN201911071414 A CN 201911071414A CN 111206278 A CN111206278 A CN 111206278A
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D17/00—Constructional parts, or assemblies thereof, of cells for electrolytic coating
- C25D17/10—Electrodes, e.g. composition, counter electrode
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D1/00—Electroforming
- C25D1/04—Wires; Strips; Foils
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D21/00—Processes for servicing or operating cells for electrolytic coating
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Abstract
The purpose of the present invention is to provide a method for removing an electrode surface deposit containing a lead compound, which is deposited on the surface of an electrode for electrolysis, by electrolysis in industrial electrolysis such as electrolytic copper foil production or copper plating, with safety and low environmental load, efficiently. The present invention relates to a method for removing an electrode surface deposit containing a lead compound from the surface of an electrode for electrolysis by performing an alkaline immersion step of immersing an electrode for electrolysis having the electrode surface deposit containing the lead compound adhered to the surface in an alkaline aqueous solution, an acid treatment step of immersing the electrode for electrolysis in an organic acid, or an alkaline coating step of coating the surface of the electrode for electrolysis with an alkaline aqueous solution.
Description
Technical Field
The present invention relates to a method for removing an electrode surface deposit containing a lead compound from an electrode for electrolysis having an electrode surface deposit on the surface thereof by electrolysis in industrial electrolysis such as electrolytic copper foil production or copper plating.
Background
Conventionally, in electrolysis in industrial electrolysis such as electrolytic copper foil production or copper plating, an oxygen generating electrode having an electrode catalyst layer containing iridium oxide coated thereon is directly used on the surface of an electrode substrate made of a valve metal such as titanium or tantalum or a valve metal alloy.
However, when such an oxygen generating electrode is used for a certain period of time or longer, the interface between the electrode substrate made of a valve metal such as titanium or tantalum or a valve metal alloy and the electrode catalyst layer made of iridium oxide is corroded, and a passivation layer is formed on the surface of the electrode substrate, so that electrolysis is difficult. Therefore, it is necessary to physically shave the surface of the electrode base until a new surface is shaved, or to newly fabricate an electrode for electrolysis from the electrode base.
Further, it is known that: when an electrode for electrolysis is used in which a layer containing 0.5 to 20 μm of a metal such as tantalum or niobium, or a metal oxide or a metal alloy is formed on the surface of an electrode substrate made of a valve metal such as titanium or tantalum, or a valve metal alloy, and an electrode catalyst layer containing iridium oxide is coated on the surface of the layer, corrosion of the surfaces of the electrode substrate and the catalyst layer can be suppressed.
However, even in the case where the oxygen generating electrode is used for electrolysis in the production of an electrolytic copper foil or in copper plating, a lead compound containing lead sulfate or lead oxide adheres to the electrode surface of the electrode for electrolysis. Lead contained in the electrolytic solution adheres to the electrode surface as lead oxide which is a good conductor during electrolysis, but is converted from lead oxide which is a conductor to lead sulfate which is a poor conductor when electrolysis is stopped. Further, lead compounds (lead sulfate or lead oxide) as the deposits on the electrode surface are detached from the surface of the electrode for electrolysis at the start and stop of the electrolysis or during the electrolysis. As a result, the above-described electrode for oxygen generation has the following problems: this causes a defect in the thickness of the copper foil due to non-uniform current distribution as an electrode for electrolysis, and cannot be continuously used for a long period of time as an electrode for electrolysis.
In this case, the electrode for generating oxygen gas is used for removing the electrode surface deposits containing the lead compound by physically polishing and washing the surface of the electrode for electrolysis used for electrolysis, or by performing an acid treatment step of immersing the electrode for electrolysis in a mixed solution of concentrated nitric acid and hydrogen peroxide and then washing with water under high pressure (patent document 1).
However, when the above-mentioned electrode for oxygen generation is continuously used for 3 months, it is difficult to remove the electrode deposit containing the lead compound from the surface of the electrode for electrolysis by the above-mentioned polishing and washing treatment.
In addition, the method of removing the electrode deposit containing the lead compound from the electrolytic electrode using the above-described acid treatment process has a problem that hydrogen peroxide which is difficult to handle is used, nitric acid which imposes a large burden on the use environment, and the like, although the method is excellent in the removal property of the electrode deposit containing the lead compound.
Documents of the prior art
Patent document
Patent document 1: japanese patent No. 4451471
Disclosure of Invention
Technical problem to be solved by the invention
An object of the present invention is to provide a safe and environmentally-friendly removing method capable of solving the above-mentioned problems of the conventional methods, and capable of efficiently removing an electrode surface deposit containing a lead compound, which has adhered to the surface of an electrode for electrolysis formed with a layer (intermediate layer) containing a metal such as tantalum, niobium, or a metal oxide or a metal alloy on the surface of an electrode substrate formed with a valve metal or a valve metal alloy, and an electrode catalyst layer covered on the surface of the layer (intermediate layer), by electrolysis in industrial electrolysis such as electrolytic copper foil production or copper plating.
Means for solving the problems
In order to achieve the above object, the present invention provides the following method for removing an electrode deposit containing a lead compound from the surface of an electrode for electrolysis.
Item 1. a removing method for removing an electrode surface deposit containing a lead compound adhering to the surface of an electrode for electrolysis by performing an alkaline immersion step of immersing the electrode for electrolysis having the electrode surface deposit containing the lead compound adhering to the surface in an alkaline aqueous solution and an acid treatment step of immersing the electrode for electrolysis in an organic acid.
The method according to item 1, wherein the surface cleaning step is performed after the alkali impregnation step and/or after the acid treatment step.
Item 3. the method of item 1 or 2, wherein the organic acid is a carboxylic acid or a sulfonic acid.
The method according to any one of items 1 to 3, wherein the organic acid is one or more selected from acetic acid, formic acid, oxalic acid, citric acid, and tartaric acid.
The method according to any one of items 1 to 4, wherein the alkaline aqueous solution is an aqueous solution of ammonia, a hydroxide or a carbonate of an alkali metal or an alkaline earth metal.
The method according to any one of items 1 to 5, wherein the alkaline aqueous solution is an aqueous solution of sodium hydroxide or potassium hydroxide.
The method of any one of items 1 to 6, wherein the lead compound is lead sulfate or lead oxide.
The method according to any one of claims 1 to 7, wherein the electrolysis electrode is an electrolysis electrode having an electrode catalyst layer containing a platinum group metal or an oxide thereof coated on a surface of the electrode.
The method according to any one of claims 1 to 8, wherein the electrolysis electrode is an electrolysis electrode in which a layer (intermediate layer) containing a metal or a metal oxide or a metal alloy is coated on a surface of an electrode base body made of a valve metal or a valve metal alloy.
Item 10. the method of item 9, wherein the metal is one or more metals or metal oxides selected from titanium, tantalum, niobium, zirconium, and hafnium, or an alloy thereof.
The method according to item 11, wherein the electrolytic electrode having the electrode surface deposit containing the lead compound adhered to the surface thereof is subjected to an alkali coating step of coating an alkaline aqueous solution on the surface of the electrolytic electrode, thereby removing the electrode surface deposit containing the lead compound adhered to the surface of the electrolytic electrode.
The method according to claim 12 to 11, wherein after the alkali coating step, a drying step is performed on the electrode for electrolysis.
Item 13. the method according to item 11 or 12, characterized in that a surface cleaning process is performed after the drying process.
The method according to any one of claims 11 to 13, wherein the aqueous alkaline solution is an aqueous solution of ammonia, a hydroxide or a carbonate of an alkali metal or an alkaline earth metal.
The method of any one of claims 11 to 14, wherein the basic aqueous solution is an aqueous solution of sodium hydroxide or potassium hydroxide.
The method of any one of claims 11 to 15, wherein the lead compound is lead sulfate or lead oxide.
The method according to any one of claims 11 to 16, wherein the electrolysis electrode is an electrolysis electrode having an electrode catalyst layer containing a platinum group metal or an oxide thereof coated on a surface of the electrode.
The method according to any one of claims 11 to 17, wherein the electrolysis electrode is an electrolysis electrode in which a layer (intermediate layer) containing a metal or a metal oxide or a metal alloy is coated on a surface of an electrode base body formed of a valve metal or a valve metal alloy.
Item 19. the method of item 18, wherein the metal is one or more metals or metal oxides selected from titanium, tantalum, niobium, zirconium, and hafnium, or alloys thereof.
Effects of the invention
According to the method for removing an electrode deposit containing a lead compound from the surface of an electrode for electrolysis of the present invention, lead hydroxide or lead carbonate can be removed (dissolved) by subjecting an electrode surface deposit containing lead sulfate or lead oxide as a lead compound, which is deposited on the surface of an electrode for electrolysis, to an alkali immersion step of immersing the electrode surface deposit in an alkaline aqueous solution such as sodium hydroxide or sodium carbonate to convert lead sulfate or lead oxide into lead hydroxide or lead carbonate, and then subjecting the electrode surface deposit containing lead hydroxide or lead carbonate to an acid treatment step of immersing the electrode surface deposit in an organic acid (for example, carboxylic acid or sulfonic acid).
In addition, lead hydroxide or lead carbonate can be removed by converting lead sulfate or lead oxide into lead hydroxide or lead carbonate through an alkali coating step of applying an alkaline aqueous solution such as sodium hydroxide or sodium carbonate to an electrode surface deposit containing a lead compound (lead sulfate or lead oxide) deposited on the surface of the electrode for electrolysis.
Further, after the alkali impregnation step, the acid treatment step, or the alkali coating step is performed, the lead compound (lead hydroxide or lead carbonate) remaining on the surface of the electrode for electrolysis can be physically removed by performing a surface cleaning step by brush coating using a brush, and thus the electrode surface deposits as the lead compound can be effectively removed.
In the method for removing lead compounds from the surface of an electrode for electrolysis, the acid used in the acid treatment step is not a strong acid such as an inorganic acid, but an organic acid which is safe and has a low environmental load is used, or the acid treatment step is not used.
Detailed Description
The present invention will be described in detail below.
(alkali impregnation step)
When the electrode for electrolysis is used for producing a metal foil (for example, for producing a copper foil), the electrode surface deposit containing a lead compound adheres to the surface of the electrode for electrolysis, and the electrode performance of the electrode for electrolysis is impaired. In this case, the electrode surface deposits containing the lead compound (for example, lead sulfate, lead oxide, or the like) adhering to the surface of the electrode for electrolysis can be removed by performing the alkali impregnation step on the electrode for electrolysis having the electrode surface deposits (hindering the electrode performance) containing the lead compound adhering to the surface of the electrode for electrolysis.
Specifically, the lead sulfate or lead oxide in the electrode surface attachment containing the lead compound can be converted into lead hydroxide or lead carbonate by immersing the electrode for electrolysis in an alkaline aqueous solution such as ammonia, a hydroxide or carbonate of an alkali metal or an alkaline earth metal for about several hours.
When the electrode for electrolysis is used for metal plating (for example, for copper plating), the electrode surface deposits containing lead sulfate as a lead compound adhere to the surface of the electrode for electrolysis, and hinder the electrode performance of the electrode for electrolysis. In this case, the electrode surface deposits containing the lead compound adhering to the surface of the electrode for electrolysis can be removed by subjecting the electrode for electrolysis having the electrode deposits containing the lead compound adhering to the surface (which impairs the performance of the electrode) to an alkaline immersion step.
Specifically, the lead sulfate in the electrode surface attachment containing the lead compound can be converted into lead hydroxide or lead carbonate by immersing the electrode for electrolysis in an alkaline aqueous solution such as ammonia, a hydroxide or carbonate of an alkali metal or an alkaline earth metal for about several hours.
In the present invention, the inhibition of the electrode performance of the electrolysis electrode means that the weight (thickness) tolerance per unit area of the metal foil or the plating produced by the electrolysis is equal to or more than a reference value due to the adhesion of the electrode surface deposit containing the lead compound to the electrode surface. For example, in the case of continuously producing a copper foil, the thickness is 1m2When the weight of the copper foil of (2) is different from the reference value by 1% or more, it is judged that the electrode performance of the electrode for electrolysis is impaired. By applying the removal method of the present invention to an electrolysis electrode in which the thickness tolerance of a metal foil or plating produced by electrolysis is equal to or more than a reference value, it is possible to effectively remove electrode deposits containing a lead compound from the surface of the electrolysis electrode.
The alkaline aqueous solution that can be used in the alkaline immersion step of the present invention can be used without limitation as long as it can effectively remove the electrode surface deposits containing the lead compound that have adhered to the surface of the electrode for electrolysis. Examples of the alkaline aqueous solution include aqueous ammonia, and aqueous solutions of hydroxides or carbonates of alkali metals or alkaline earth metals.
Examples of the hydroxide of an alkali metal or an alkaline earth metal include lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, beryllium hydroxide, magnesium hydroxide, calcium hydroxide, strontium hydroxide, and barium hydroxide.
Examples of the carbonate of an alkali metal or an alkaline earth metal include lithium carbonate, sodium carbonate, potassium carbonate, rubidium carbonate, cesium carbonate, beryllium carbonate, magnesium carbonate, calcium carbonate, strontium carbonate, and barium carbonate. Among the above, hydroxides of alkali metals or alkaline earth metals are preferable, and sodium hydroxide or potassium hydroxide is more preferable.
The concentration of the alkaline aqueous solution used in the alkaline immersion step of the present invention may be appropriately selected according to the purpose, and for example, a concentration in the range of 1 to 48 mass% (room temperature 25 ℃) can be used without any particular problem. Preferably in the range of 3 to 35 mass% (room temperature 25 ℃ C.), more preferably in the range of 4 to 30 mass% (room temperature 25 ℃ C.). When the concentration of the alkaline aqueous solution exceeds 48 mass%, there is a possibility that the catalyst layer of the electrode for electrolysis is peeled off, and when the concentration is less than 1 mass%, the reaction for converting lead sulfate in the electrode surface deposit containing a lead compound into lead hydroxide or lead carbonate cannot be sufficiently performed, and the removal efficiency is insufficient.
In the alkali impregnation step of the present invention, the temperature of the aqueous alkali solution is not particularly limited, and may be, for example, about 0 to 90 ℃, preferably about room temperature (25 ℃) to 80 ℃, and more preferably about 50 to 70 ℃. The time for immersing the electrolysis electrode in the alkaline aqueous solution in the alkaline immersion step may be a time to the extent that the lead compound (lead sulfate or lead oxide converted to lead hydroxide or lead carbonate, etc.) attached to the surface of the electrolysis electrode is converted, and for example, when the lead compound attached to the surface of the electrolysis electrode is lead sulfate, in the case of using an aqueous solution of a hydroxide or carbonate of an alkali metal or an alkaline earth metal as the alkaline aqueous solution, a time sufficient for the attached lead sulfate to be converted to lead hydroxide or lead carbonate may be sufficient. Further, when the lead compound adhering to the surface of the electrode for electrolysis is lead oxide, in the case of using an aqueous solution of a hydroxide or carbonate of an alkali metal or an alkaline earth metal as the alkaline aqueous solution, it is sufficient for the adhered lead oxide to be converted into lead hydroxide or lead carbonate. The time for immersion in the alkaline aqueous solution is usually about 10 minutes to 10 hours, preferably about 1 hour to 5 hours.
The electrode for electrolysis subjected to the alkali immersion step may be subjected to the acid treatment step described later as it is, or may be subjected to the acid treatment step after being subjected to the surface cleaning step described later. The method of carrying out the alkaline immersion step and thereafter carrying out the alkaline immersion step can be appropriately examined according to the amount of the lead compound-containing electrode surface deposit deposited on the surface of the electrode for electrolysis.
(acid treatment Process)
In the removing method of the present invention, the electrode surface deposits containing the lead compound adhering to the surface of the electrolysis electrode can be effectively removed by subjecting the electrolysis electrode to the acid treatment step after the alkali immersion step.
Specifically, the electrode for electrolysis is immersed in an organic acid for several hours to dissolve lead hydroxide or lead carbonate converted in the alkali immersion step, thereby removing the electrode deposit containing a lead compound from the surface of the electrode for electrolysis.
The organic acid that can be used in the acid treatment step of the present invention is not particularly limited, and for example, a carboxylic acid or a sulfonic acid can be used.
Specific examples of the acid include carboxylic acids such as oxalic acid, malonic acid, succinic acid, adipic acid, sebacic acid, citric acid, fumaric acid, maleic acid, formic acid, acetic acid, and tartaric acid; sulfonic acids such as p-toluenesulfonic acid, methanesulfonic acid, trifluoroacetic acid, dichloroacetic acid, trichloroacetic acid, trifluoromethanesulfonic acid, benzenesulfonic acid, naphthalenesulfonic acid, and naphthalenedisulfonic acid.
Among them, acetic acid, formic acid, oxalic acid, citric acid, tartaric acid are preferable, and acetic acid or formic acid is more preferable. The concentration of the organic acid to be used is not particularly limited as long as it is 50% by mass or more (room temperature 25 ℃ C.), preferably 75% by mass or more (room temperature 25 ℃ C.), and more preferably 90% by mass or more (room temperature 25 ℃ C.).
In the acid treatment step of the present invention, the temperature of the organic acid is not particularly limited, and may be, for example, about 0 to 90 ℃, preferably about room temperature (25 ℃) to 80 ℃, and more preferably about 50 to 70 ℃. The time for immersing the electrolysis electrode in the organic acid in the acid treatment step may be a time sufficient to dissolve the lead compound attached to the surface of the electrolysis electrode, and for example, when the lead compound attached to the surface of the electrolysis electrode is lead hydroxide or lead carbonate, the time sufficient to dissolve the lead hydroxide or lead carbonate may be sufficient. The immersion time in the organic acid may be generally about 10 minutes to 10 hours, and preferably about 1 hour to 5 hours.
The electrolytic electrode subjected to the acid treatment step may be subjected to a surface cleaning step as it is. Further, by performing the alkali immersion step again, the electrode deposits containing the lead compound can be efficiently removed from the surface of the electrode for electrolysis.
(alkali coating Process)
In the removing method of the present invention, in addition to the alkali immersion step and the acid treatment step, an alkali coating step of coating an alkaline aqueous solution on the surface of the electrode for electrolysis is performed, whereby the electrode surface deposits containing the lead compound and adhering to the surface of the electrode for electrolysis can be removed.
Specifically, by applying an alkaline aqueous solution such as ammonia water or a hydroxide or carbonate of an alkali metal or alkaline earth metal to the surface of an electrolysis electrode having an electrode surface deposit containing a lead compound adhered to the surface thereof, lead sulfate or lead oxide in the electrode surface deposit containing a lead compound can be converted into lead hydroxide or lead carbonate, and the electrode surface deposit can be removed.
The method for applying the alkaline aqueous solution to the surface of the electrode for electrolysis in the alkaline coating step is not particularly limited, and a known method such as a method of applying the solution using a brush roll or the like, a spray method, a dip coating method, or the like can be used.
The alkaline aqueous solution that can be used in the alkaline coating step of the present invention is not particularly limited as long as it can effectively remove the electrode surface deposits containing the lead compound that have adhered to the surface of the electrode for electrolysis. Examples of the alkaline aqueous solution include aqueous ammonia, and aqueous solutions of hydroxides or carbonates of alkali metals or alkaline earth metals.
Examples of the hydroxide of an alkali metal or an alkaline earth metal include lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, beryllium hydroxide, magnesium hydroxide, calcium hydroxide, strontium hydroxide, and barium hydroxide.
Examples of the carbonate of an alkali metal or an alkaline earth metal include lithium carbonate, sodium carbonate, potassium carbonate, rubidium carbonate, cesium carbonate, beryllium carbonate, magnesium carbonate, calcium carbonate, strontium carbonate, and barium carbonate. Among the above, hydroxides of alkali metals or alkaline earth metals are preferable, and sodium hydroxide or potassium hydroxide is more preferable.
The alkaline aqueous solution used in the alkaline coating step of the present invention can be used without any problem as long as it has a concentration in the range of 1 mass% to a saturation concentration (for example, the maximum dissolved concentration at each temperature such as 52.2 mass% at 20 degrees). Preferably 20 to 48% by mass (room temperature: 25 ℃ C.), more preferably 32 to 48% by mass (room temperature: 25 ℃ C.). When the amount is less than 1% by mass, the reaction for converting lead sulfate in the electrode surface deposit containing a lead compound into lead hydroxide or lead carbonate is not sufficiently performed, and the removal efficiency is not sufficient.
In the alkali coating step, the amount of the alkaline aqueous solution to be applied may be an amount sufficient to convert the electrode surface deposits containing the lead compound adhering to the surface of the electrode for electrolysis, specifically, an amount sufficient to convert the lead compound such as lead sulfate or lead oxide into lead hydroxide or lead carbonate, for example, 100ml/m2～1000ml/m2May be in the range of 200ml/m, preferably2～800ml/m2The range of (1).
The electrode for electrolysis subjected to the alkali coating step may be subjected to a drying step to dry the electrode for electrolysis. The drying step may be performed under conditions such that the applied alkaline aqueous solution is evaporated, and for example, the drying step may be performed at room temperature for about 10 minutes to 24 hours, preferably at a temperature of from room temperature to 200 ℃ for 5 minutes to ten and several hours.
The electrolytic electrode subjected to the alkali coating step may be subjected to the surface cleaning step described later as it is, or may be subjected to the surface cleaning step after the drying step. Further, after the surface treatment step, the alkaline coating step and the surface cleaning step are repeated again with respect to the electrode for electrolysis, whereby the electrode deposit containing the lead compound can be efficiently removed from the surface of the electrode for electrolysis.
(surface cleaning Process)
In the removing method of the present invention, the electrode surface deposits containing the lead compound on the surface of the electrode for electrolysis can be physically removed by performing the surface cleaning step after the alkali immersion step and/or after the acid treatment step, or after the alkali coating step.
As the surface cleaning step, a method that can be generally used for surface cleaning of the electrode surface can be used. For example, the surface may be cleaned by spraying high-pressure water having a pressure of about 5 to 100MPa on the electrode surface, or by polishing (brushing) the surface with a brush or bristles. The electrode for electrolysis is subjected to a surface cleaning treatment to physically remove the lead compound remaining on the surface of the electrode for electrolysis, thereby removing the electrode deposit containing the lead compound from the surface of the electrode for electrolysis.
In addition, when the surface is cleaned by polishing (brushing), brushing may be performed while using water (e.g., ion-exchanged water, distilled water, pure water, tap water, etc.).
(electrode for electrolysis)
The electrolysis electrode to which the removal method of the present invention can be applied is an electrode in which an electrode surface deposit containing a lead compound is deposited on the surface of the electrolysis electrode, and the electrode surface deposit containing a lead compound is a substance in which a lead compound containing lead sulfate, lead oxide, or the like is deposited on the surface of the electrolysis electrode by electrolytic plating or metal foil production electrolysis.
The content of the lead compound in the electrode surface deposit is not particularly limited as long as it contains lead sulfate or lead oxide, and when at least 50% or more of the electrode surface deposit is a lead compound, the removal method of the present invention can be preferably applied. In addition, various metal impurities other than lead compounds may be contained in the electrode surface deposits. That is, the removal method of the present invention can be used for the following electrodes for electrolysis: an electrode for electrolysis used in electrolytic plating or metal foil production electrolysis has a surface of an electrode attached matter containing a lead compound such as lead oxide or lead sulfate, and thus the electrode performance of the electrode for electrolysis is impaired.
The amount of lead compound removed from the electrode surface deposit deposited on the electrolysis electrode can be measured by the method described in examples. Specifically, the peak intensity of lead on the electrode surface is measured using a fluorescent X-ray analyzer, and can be determined from the peak intensity of lead on the electrode surface before the removal method (initial intensity) and the peak intensity of lead on the electrode surface after the removal method.
The electrode substrate of the electrode for electrolysis is not particularly limited in material or shape as long as it is made of a metallic material, has conductivity, or has appropriate rigidity. For example, a valve metal or an alloy of a valve metal such as titanium, tantalum, niobium, or zirconium, which has excellent corrosion resistance, is preferable. If necessary, the electrode substrate may be subjected to physical and chemical pretreatment such as annealing, surface roughening by sandblasting or the like, and surface cleaning by pickling or the like in advance as appropriate.
Further, the electrode for electrolysis is preferably covered with a layer (intermediate layer) containing a metal or a metal oxide or a metal alloy on the surface of the electrode base. The metal forming the layer (intermediate layer) is not particularly limited as long as it has excellent conductivity and corrosion resistance and has good adhesion to the substrate or the electrode catalyst layer. Typical metals used for the intermediate layer include titanium, tantalum, niobium, zirconium, hafnium, and the like, oxides of these metals, alloys of these metals, and the like, which have excellent corrosion resistance, and they have excellent adhesion to an electrode substrate made of a valve metal such as titanium. In addition, the metal in the layer containing a metal, a metal oxide, or a metal alloy (intermediate layer) may be only one type, or a combination of a plurality of types of metals may be used. When a plurality of metals are used in combination, the ratio thereof can be appropriately adjusted. Among them, tantalum, titanium, or oxides of these metals or alloys of these metals are preferable.
As a method for coating the electrode substrate with the cover layer (intermediate layer), a layer forming method by vacuum sputtering is exemplified. As the vacuum sputtering, various apparatuses such as dc sputtering, high-frequency sputtering, arc ion plating, ion beam plating, and cluster ion beam method can be applied, and a layer (intermediate layer) having desired physical properties can be formed by appropriately setting conditions such as the degree of vacuum, the substrate temperature, the composition and purity of the target plate, and the deposition rate (input power). The thickness of the layer (intermediate layer) may be usually in the range of 0.1 to 10 μm, and may be appropriately selected from the practical viewpoint of corrosion resistance, productivity, and the like. Thus, the electrode base body with the surface covered has excellent characteristics against thermal oxidation of the surface thereof, i.e., has a remarkable feature in the growth behavior of the oxide film.
The electrode for electrolysis is preferably covered with a cover layer (intermediate layer) on the electrode substrate by the above-described method, and further covered with an electrode catalyst layer. The electrode catalyst layer is not particularly limited, and various known materials can be applied according to the use, and for example, in the case of an oxygen generation reaction in which durability is particularly required, it preferably contains a platinum group metal oxide such as iridium oxide.
Various methods are known as a method for covering the electrode catalyst layer on the electrolysis electrode, and the method can be appropriately selected according to the purpose. For example, a thermal decomposition method or the like is exemplified, and an electrode catalyst layer can be formed by dissolving a raw material salt of a metal of the catalyst layer component, such as chloride, nitrate, alkoxide, resinate, or the like, in a solvent such as hydrochloric acid, nitric acid, alcohol, or an organic solvent to prepare a covering liquid, applying the covering liquid on the surface of the electrode substrate, and performing a heating treatment in a firing furnace in an oxidizing atmosphere such as air after drying. The thickness of the electrode catalyst layer is usually in the range of 0.1 to 30 μm. In addition, the metal in the electrode catalyst layer may be only one kind, or a plurality of kinds may be used in combination. When a plurality of kinds are used in combination, the ratio of each metal can be appropriately adjusted.
Alternatively, the metal oxide may be prepared in advance, an appropriate organic binder and an appropriate organic solvent may be added to the metal oxide to prepare a paste, and the paste may be printed on an electrode substrate and fired to form an electrode catalyst layer on the electrode substrate by a thick film method or a CVD method.
Further, in the removing method of the present invention, an electrode catalyst layer may be formed on the electrode for electrolysis from which the deposits on the surface of the electrode have been removed by the above-described method.
The electrode for electrolysis used in the removal method of the present invention may be used as an electrode for metal foil production or an electrode for metal plating. Specifically, an electrode for manufacturing a metal foil (for example, an electrode for manufacturing a copper foil) is an electrode for continuously manufacturing a copper foil by plating copper on a cylindrical cathode and peeling the cathode. In addition, the metal plating electrode (for example, a copper plating electrode) is used for electrolysis for forming a thin film layer by reducing an arbitrary metal component (for example, copper) contained in the electrolyte and causing an electric crystallization on the plating object.
Examples
The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
< example 1>
An electrode for electrolysis used in a simulated electrolysis test for copper foil production electrolysis was used as the test electrode described below under electrolysis conditions. The amount of lead compound removed from the deposits on the electrode surface was measured using a fluorescent X-ray analyzer described later.
Commercially available electrode for electrolysis for producing metal foil (DAISO ENGINEERING CO., LTD. manufactured model: MD-220, base: titanium, electrode catalyst layer: iridium oxide, intermediate layer; alloy of titanium and tantalum)
Conditions of electrolysis
Counter electrode (cathode): pt plate
Current density: 100A/dm2
Electrolysis temperature: 80 deg.C
Electrolyte solution: with addition of 50ppm of Pb (NO)3)220% by weight of H2SO4With 10% by weight of Na2SO4Solution of (2)
Electrolysis time: 168 hours
Conditions for fluorescent X-ray analysis
The measuring instrument: 3270 manufactured by Rigaku Corporation
Target: rh (rhodium)
Output setting: 20kV and 30mA
Measuring time: 30 seconds
And (3) measuring atmosphere: under the atmosphere
Preparation of a sample: the test electrode was cut into a 10 mm-long 10 mm-wide 1 mm-thick section
The cut piece of the electrode for electrolysis (length: 10 mm. times. width: 10 mm. times. thickness: 1mm) to which the electrode surface deposit containing lead sulfate was attached was immersed in a 24 mass% aqueous solution of sodium hydroxide (manufactured by Tokyo Chemical industry co., ltd.) under the above-mentioned electrolysis conditions at 60 ℃ for 2 hours, and an alkaline immersion step was performed to convert the lead sulfate in the electrode surface deposit attached to the surface of the electrode for electrolysis into lead hydroxide. Then, the surface of the electrode for electrolysis is brushed with a brush while spraying ion exchange water thereon, whereby a part of the lead compound (mainly, lead hydroxide) that can be removed by the alkali impregnation step is physically removed, and the surface cleaning step is performed. Next, the electrode piece for electrolysis was immersed in 99.5 mass% acetic acid (manufactured by Tokyo Chemical Industry co., ltd.) at 60 ℃ for 1 hour, and subjected to an acid treatment process to dissolve lead hydroxide. Further, the surface of the electrode for electrolysis was brushed with a brush while spraying ion exchange water thereon, and the surface cleaning step was performed by physically removing the remaining lead compound (mainly, lead hydroxide). For the electrode for electrolysis from which the electrode deposit containing the lead compound was removed from the surface, the peak intensity of lead on the electrode surface was measured using a fluorescent X-ray analyzer. The lead compound was reduced by 94.4% as compared with the peak intensity of the initial intensity (the peak intensity of lead on the electrode surface before removing the electrode deposit containing the lead compound from the surface was taken as 100).
< example 2>
The test was performed in the same manner as in example 1, except that the sodium hydroxide used in the test was changed to 12% by mass. For the electrode for electrolysis from which the electrode deposit containing the lead compound was removed from the surface, the peak intensity of lead on the electrode surface was measured using a fluorescent X-ray analyzer. The lead compound was reduced by 85.6% compared to the peak intensity of the initial intensity.
< example 3>
The test was performed in the same manner as in example 1, except that the sodium hydroxide used in the test was changed to 6 mass%. For the electrode for electrolysis from which the electrode deposit containing the lead compound was removed from the surface, the peak intensity of lead on the electrode surface was measured using a fluorescent X-ray analyzer. The lead compound was reduced by 78.1% as compared with the peak intensity of the initial intensity.
< example 4>
Under the above electrolysis conditions, a 48 mass% aqueous solution of sodium hydroxide (Tokyo Chemical IndustryCo., Ltd.) was 400ml/m2The above-mentioned aqueous sodium hydroxide solution was applied to a cut piece (length: 10 mm. times. width: 10 mm. times. thickness: 1mm) of an electrolysis electrode to which an electrode surface deposit containing lead sulfate had adhered, using a brush, and an alkali coating step was carried out to convert lead sulfate in the electrode surface deposit adhering to the surface of the electrolysis electrode into lead hydroxide. Then, the mixture was dried overnight at room temperature (25 ℃ C.) to conduct a drying step. Further, the surface of the electrode for electrolysis was brushed with a brush while spraying ion exchange water thereon to physically remove lead compounds (mainly lead hydroxide), and then the surface cleaning step was performed. For the electrode for electrolysis from which the electrode deposit containing the lead compound was removed from the surface, the peak intensity of lead on the electrode surface was measured using a fluorescent X-ray analyzer. The lead compound was reduced by 65.6% as compared with the peak intensity of the initial intensity (the peak intensity of lead on the electrode surface before removing the electrode deposit containing the lead compound from the surface was taken as 100). Further, the alkali coating step, the drying step, and the surface cleaning step are repeated in the same orderAs a result of measuring the removal rate of the lead compound on the electrode surface, the lead compound was reduced by 81.5% from the peak intensity of the initial intensity after 2 cycles, and the lead compound was reduced by 94.4% from the peak intensity of the initial intensity after 3 cycles.
< comparative example 1>
The same electrolytic electrode chips (length: 10 mm. times. width: 10 mm. times. thickness: 1mm) as those used in < example 1> for the electrolysis test were immersed in a 6 mass% aqueous solution of sodium hydroxide at 60 ℃ for 2 hours, and then subjected to an alkali immersion step in which lead sulfate in the electrode surface deposits adhering to the surface of the electrolytic electrode was converted into lead hydroxide. Then, the surface of the electrode for electrolysis is brushed (with a brush) while spraying ion-exchange water thereon, whereby a part of the lead compound (mainly, lead hydroxide) that can be removed by the alkali impregnation step is physically removed, and the surface cleaning step is performed. For the electrode for electrolysis from which the electrode deposit containing the lead compound was removed from the surface, the peak intensity of lead on the electrode surface was measured using a fluorescent X-ray analyzer. The lead compound was reduced by 31.7% as compared with the peak intensity of the initial intensity.
< comparative example 2>
The same electrolytic electrode chips (length: 10 mm. times. width: 10 mm. times. thickness: 1mm) as those used in < example 1> were immersed in 98 mass% acetic acid and immersed at 90 ℃ for 3 hours to carry out the acid treatment step. Then, the surface of the electrode for electrolysis is brushed (with a brush) while spraying ion-exchange water thereon, whereby a part of the lead compound that can be removed by the acid treatment step is physically removed, and the surface cleaning step is performed. For the electrode for electrolysis from which the electrode deposit containing the lead compound was removed from the surface, the peak intensity of lead on the electrode surface was measured using a fluorescent X-ray analyzer. The lead compound was reduced by 29.3% as compared with the peak intensity of the initial intensity.
Industrial applicability
The removal method of the present invention can remove electrode deposits containing lead compounds from the surfaces of various electrodes for electrolysis, not only in the production of electrolytic copper powder or electrolytic copper foil, but also in copper plating.
Claims (19)
1. A method for removing an electrode surface deposit containing a lead compound adhering to the surface of an electrode for electrolysis by subjecting the electrode for electrolysis having the electrode surface deposit containing the lead compound adhering to the surface thereof to an alkaline immersion step of immersing the electrode in an alkaline aqueous solution and an acid treatment step of immersing the electrode in an organic acid.
2. The method according to claim 1, wherein the surface cleaning step is performed after the alkali impregnation step and/or after the acid treatment step.
3. A process according to claim 1 or 2, wherein the organic acid is a carboxylic acid or a sulphonic acid.
4. The method according to any one of claims 1 to 3, wherein the organic acid is one or more selected from the group consisting of acetic acid, formic acid, oxalic acid, citric acid and tartaric acid.
5. The method according to any one of claims 1 to 4, wherein the aqueous alkaline solution is an aqueous solution of ammonia, a hydroxide or a carbonate of an alkali metal or an alkaline earth metal.
6. A process according to any one of claims 1 to 5, wherein the aqueous alkaline solution is an aqueous solution of sodium hydroxide or potassium hydroxide.
7. A method according to any one of claims 1 to 6 wherein the lead compound is lead sulphate or lead oxide.
8. The method according to any one of claims 1 to 7, wherein the electrolysis electrode is an electrolysis electrode having an electrode catalyst layer containing a platinum group metal or an oxide thereof coated on the surface of the electrode.
9. The method according to any one of claims 1 to 8, wherein the electrolysis electrode is an electrode for electrolysis in which a layer (intermediate layer) containing a metal or a metal oxide or a metal alloy is coated on the surface of an electrode base made of a valve metal or a valve metal alloy.
10. The method according to claim 9, wherein the metal is one or more metals or metal oxides selected from titanium, tantalum, niobium, zirconium, and hafnium, or an alloy thereof.
11. A method for removing an electrode surface deposit containing a lead compound adhering to the surface of an electrode for electrolysis by applying an alkaline aqueous solution to the surface of the electrode for electrolysis to which the electrode surface deposit containing the lead compound has adhered.
12. The method according to claim 11, wherein the drying step is performed on the electrode for electrolysis after the alkali coating step.
13. The method according to claim 11 or 12, wherein the surface cleaning step is performed after the drying step.
14. The method according to any one of claims 11 to 13, wherein the aqueous alkaline solution is an aqueous solution of ammonia, a hydroxide or a carbonate of an alkali metal or an alkaline earth metal.
15. A process according to any one of claims 11 to 14, wherein the aqueous alkaline solution is an aqueous solution of sodium hydroxide or potassium hydroxide.
16. A method according to any one of claims 11 to 15 wherein the lead compound is lead sulphate or lead oxide.
17. The method according to any one of claims 11 to 16, wherein the electrolysis electrode is an electrolysis electrode having an electrode catalyst layer containing a platinum group metal or an oxide thereof coated on a surface of the electrode.
18. The method according to any one of claims 11 to 17, wherein the electrolysis electrode is an electrode for electrolysis in which a layer (intermediate layer) containing a metal or a metal oxide or a metal alloy is coated on the surface of an electrode base made of a valve metal or a valve metal alloy.
19. The method according to claim 18, wherein the metal is one or more metals or metal oxides selected from titanium, tantalum, niobium, zirconium, and hafnium, or an alloy thereof.
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| CN111910189A (en) * | 2020-07-14 | 2020-11-10 | 广东省稀有金属研究所 | Method for removing dirt on surface of noble metal oxide electrode |
| CN115305161A (en) * | 2022-07-22 | 2022-11-08 | 福建紫金铜箔科技有限公司 | Electrolytic copper foil anode plate cleaning agent and preparation method thereof |
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| JP2023062131A (en) | 2023-05-02 |
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