Classifications

• • 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
  • C25D21/16—Regeneration of process solutions
  • C25D21/18—Regeneration of process solutions of electrolytes
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/30—Electroplating: Baths therefor from solutions of tin

Definitions

• the present invention relates to a method and device for regenerating plating compositions.
• JP2004-534151A proposes a method for regenerating a plating solution in which electrolytically deposited tin is used to reduce tin(IV) ions to tin(II) ions.
• JP2015-518923A also proposes a method for regenerating a plating composition by oxidizing and reducing two types of metal components in the plating composition using an apparatus equipped with a working electrode chamber, a counter electrode chamber, and an ion exchange membrane separating them.
• One aspect of the present invention aims to provide a method for regenerating a plating composition that can efficiently reduce metal ions in a high oxidation state in the plating composition to metal ions in a low oxidation state.
• the first aspect is a method for regenerating a plating composition, comprising: removing at least a portion of the surfactant from a plating composition containing tin (IV) ions and a surfactant; introducing the plating composition from which at least a portion of the surfactant has been removed into a counter electrode chamber having a counter electrode and a working electrode chamber having a working electrode, the working electrode chamber being isolated by a membrane selected from the group consisting of an ion exchange membrane, a reverse osmosis membrane, and a nanofiltration membrane; reducing at least a portion of the tin (IV) ions in the introduced plating composition to metallic tin using the working electrode as a cathode; and oxidizing at least a portion of the reduced metallic tin to tin (II) ions using the working electrode as an anode.
• the second embodiment is a plating composition regeneration device that includes a surfactant removal means, a working electrode chamber having a working electrode, a counter electrode chamber having a counter electrode, and one type of membrane selected from the group consisting of an ion exchange membrane, a reverse osmosis membrane, and a nanofiltration membrane that separates the working electrode chamber from the counter electrode chamber.
• a method for regenerating a plating composition can be provided that can efficiently reduce metal ions in a high oxidation state in the plating composition to metal ions in a low oxidation state.
• the term "process” includes not only independent processes, but also processes that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved.
• the content of each component in a composition means the total amount of the multiple substances present in the composition when multiple substances corresponding to each component are present in the composition, unless otherwise specified.
• the upper and lower limits of the numerical ranges described in this specification can be arbitrarily selected and combined from the numerical values exemplified as numerical ranges. Below, the embodiments of the present invention are described in detail. However, the embodiments shown below are examples of a plating composition regeneration method and regeneration device for embodying the technical concept of the present invention, and the present invention is not limited to the plating composition regeneration method and regeneration device shown below.
• a method for regenerating a plating composition includes a first step of removing at least a portion of the surfactant from a plating composition containing tin (IV) ions and a surfactant; a second step of introducing the plating composition from which at least a portion of the surfactant has been removed into a counter electrode chamber having a counter electrode and a working electrode chamber having a working electrode, the working electrode chamber being isolated by a membrane selected from the group consisting of an ion exchange membrane, a reverse osmosis membrane, and a nanofiltration membrane, and reducing at least a portion of the tin (IV) ions in the introduced plating composition to metallic tin using the working electrode as a cathode; and a third step of oxidizing at least a portion of the reduced metallic tin to tin (II) ions using the working electrode as an anode.
• tin (IV) ions can be electrochemically reduced using an electrochemical device equipped with a counter electrode chamber and a working electrode chamber separated by a membrane that is difficult for tin ions to permeate, such as an ion exchange membrane, to efficiently reduce the tin (IV) ions to metallic tin.
• This can be considered, for example, as follows.
• the plating composition may be an electrolytic plating solution or an electroless plating solution.
• the plating composition may be preferably an electrolytic plating solution or an electrolytic tin plating solution, and more preferably a used electrolytic tin plating solution.
• the plating composition may be a liquid medium in which at least tin (IV) ions and a surfactant are dissolved.
• the liquid medium constituting the plating composition may contain at least water, and may further contain a water-soluble organic solvent, etc., in addition to water, as necessary.
• the surfactant contained in the plating composition may be any of nonionic surfactants, cationic surfactants, anionic surfactants, amphoteric surfactants, etc. Furthermore, the surfactant may function as a so-called brightener, leveler, etc. in the plating composition. From the viewpoint of the reduction efficiency of tin (IV) ions, the surfactant may contain at least one type selected from the group consisting of nonionic surfactants, cationic surfactants, and amphoteric surfactants.
• the plating composition may contain only one type of surfactant, or a combination of two or more types.
• Nonionic surfactants include, for example, ester type surfactants in which polyhydric alcohols such as glycerin, sorbitol, and sucrose are ester-bonded to fatty acids; ether type surfactants formed by adding ethylene oxide, propylene oxide, etc. to compounds having hydroxyl groups such as higher alcohols and alkylphenols; and ester-ether type surfactants formed by adding ethylene oxide, propylene oxide, etc. to ester type surfactants.
• ester type surfactants in which polyhydric alcohols such as glycerin, sorbitol, and sucrose are ester-bonded to fatty acids
• ether type surfactants formed by adding ethylene oxide, propylene oxide, etc. to compounds having hydroxyl groups such as higher alcohols and alkylphenols
• ester-ether type surfactants formed by adding ethylene oxide, propylene oxide, etc. to ester type surfactants.
• nonionic surfactants include polyethylene glycol, polypropylene glycol, polyoxyethylene octylphenol, polyoxyethylene ⁇ -naphthyl ether, polyoxyethylene alkylamine, polyoxyethylene alkyl ether, polyoxyethylene polyoxypropylene alkyl ether, glycerin fatty acid ester and its ethylene oxide adduct, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, fatty acid monoethanolamide and its ethylene oxide adduct, fatty acid-N-methyl monoethanolamide and its ethylene oxide adduct, fatty acid diethanolamide and its ethylene oxide adduct, sucrose fatty acid ester, alkyl (poly)glycerin ether, polyglycerin fatty acid ester, polyethylene glycol fatty acid ester, fatty acid methyl ester ethoxylate, N-long chain alkyl dimethylamine oxide, etc.
• Nonionic surfactants may have fluor
• Cationic surfactants include, for example, amine salts and quaternary ammonium salts.
• Specific examples of cationic surfactants include alkyl (or alkenyl) trimethyl ammonium salts, alkyl (or alkenyl) triethyl ammonium salts, dialkyl (or alkenyl) dimethyl ammonium salts, alkyl (or alkenyl) quaternary ammonium salts, mono- or dialkyl (or alkenyl) quaternary ammonium salts containing an ether group, an ester group, or an amide group, alkyl (or alkenyl) pyridinium salts, alkyl (or alkenyl) dimethyl benzyl ammonium salts, alkyl (or alkenyl) isoquinolinium salts, dialkyl (or alkenyl) morphonium salts, polyoxyethylene alkyl (or alkenyl) amines, alkyl (or alken
• Amphoteric surfactants exhibit the properties of anionic surfactants in the alkaline range and cationic surfactants in the acidic range.
• amphoteric surfactants include carboxylates and sulfonates, and may be either amino acid type or betaine type.
• amphoteric surfactants include alkyl dimethyl amino acid betaines, alkyl dimethyl acetate betaines, alkyl dimethyl carboxy betaines, alkyl dimethyl carboxy methylene ammonium betaines, alkyl dimethyl ammonio acetates, fatty acid amidopropyl dimethyl amino acid betaines, alkyl yl amidopropyl dimethyl glycines, 2-alkyl-1-(2-hydroxyethyl) imidazolium-1-acetates, alkyl diaminoethyl glycines, dialkyl diaminoethyl glycines, and alkyl dimethyl amine oxides.
• Anionic surfactants include carboxylates, sulfonates, sulfates, and phosphates.
• the surfactant content in the plating composition may be, for example, 0.01 g/L or more and 10 g/L or less, and preferably 0.1 g/L or more or 5 g/L or less.
• the surfactant content in the plating composition after removal in the first step may be, for example, 0.005 g/L or more.
• the surfactant content can be measured using surface tension as an index. Specifically, it can be measured using a drop counter.
• the tin (IV) ions contained in the plating composition may be derived from, for example, a water-soluble tin (IV) salt, or may be generated by the oxidation of the tin (II) ions constituting the plating composition before use.
• the tin (IV) ions contained in the plating composition may be simple metal ions or complex ions.
• complexing agents that form complex ions include carboxylic acids including gluconic acid (including gluconolactone), citric acid, glutaric acid, succinic acid, malic acid, tartaric acid, lactic acid, and salts or derivatives thereof; phosphoric acids including tripolyphosphoric acid, hydroxyethanediphosphonic acid, and salts thereof; sugars including sorbitol, mannitol, and salts thereof; amino acids including phenylalanine, glutamic acid, aspartic acid, alanine, glycine, and salts thereof; HEDTA, EDTA, and the like.
• the complexing agent may include at least one selected from the group consisting of these, and may include at least gluconic acid.
• the complexing agent may be used alone or in combination of two or more. Because the tin (IV) ion is a complex ion, it is possible to set the pH of the plating composition to a weak acidic to weak alkaline range, which makes it possible to suppress corrosion of the plated object that is vulnerable to strong acids or strong alkalis (for example, ceramic capacitors and other objects that use oxides as components).
• the content of tin (IV) ions in the plating composition may be, for example, 0.1 g/L or more and 100 g/L or less, and preferably 1 g/L or more.
• the content of the complexing agent in the plating composition may be, for example, equimolar to 20 times the molar amount of tin ions, and preferably 10 times the molar amount.
• the content of tin (IV) ions in the plating composition is measured, for example, by inductively coupled plasma atomic emission spectroscopy (ICP-AES), or by oxidation-reduction titration with potassium iodate after reduction with iron powder.
• ICP-AES inductively coupled plasma atomic emission spectroscopy
• the plating composition may contain tin(II) ions in addition to tin(IV) ions.
• the tin(II) ions may be simple metal ions or complex ions.
• the complexing agent that forms the complex ions is the same as that for tin(IV) ions.
• the content of tin(II) ions contained in the plating composition may be, for example, 100 g/L or less, and preferably 20 g/L or less.
• the content of tin(II) ions contained in the plating composition is measured in the same manner as that for tin(IV) ions.
• the tin(II) ion may be derived from a water-soluble tin(II) salt.
• water-soluble tin(II) salts include stannous sulfate, stannous chloride, tin fluoroborate, tin(II) alkanesulfonate, tin(II) alkanolsulfonate, and tin(II) aromatic sulfonate.
• the salt may contain at least one selected from the group consisting of these, and may contain at least tin(II) alkanesulfonate.
• alkane sulfonic acid in the tin(II) alkanesulfonate examples include alkanesulfonic acids having 1 to 3 carbon atoms, and specific examples include methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, and 2-propanesulfonic acid.
• the plating composition may further contain, in addition to tin ions, other metal ions other than tin.
• other metal ions include salts of lead ions, copper ions, silver ions, bismuth ions, cobalt ions, nickel ions, etc.
• the plating composition may further contain alkali metal ions, ammonium ions, etc.
• alkali metal ions, ammonium ions, etc. By containing alkali metal ions, ammonium ions, etc., the electrical conductivity is increased, heat generation due to solution resistance during electrolytic plating is suppressed, and uniform electrodeposition tends to be improved.
• alkali metal ions include lithium ions, sodium ions, potassium ions, rubidium, cesium, etc.
• Alkali metal ions, ammonium ions, etc. may be added to the plating composition as, for example, a salt with an acid component. By containing an acid component in the plating composition, for example, the stability of the plating composition is further improved.
• acid components include sulfuric acid, hydrochloric acid, alkane sulfonic acid, alkanol sulfonic acid, aromatic sulfonic acid, phosphoric acid, alkyl carboxylic acid, aryl carboxylic acid, etc., and the plating composition may contain at least one selected from the group consisting of these. These acids may be used alone or in combination of two or more.
• the pH of the plating composition may be, for example, 1 or more and 13 or less, preferably 3 or more or 4 or more, and preferably 11 or less or 9 or less.
• the pH of the plating composition may be adjusted to a desired range, for example, with a pH adjuster.
• pH adjusters include alkali metal hydroxides, ammonia, etc., in addition to the acid components described above.
• the plating composition may further contain an antioxidant.
• an antioxidant for example, the stability of the plating composition can be improved and the bath life can be extended.
• antioxidants include hydroquinone, ascorbic acid, catechol, hypophosphorous acid, erythorbic acid, etc.
• the content of the antioxidant contained in the plating composition may be, for example, 0.01 g/L or more and 20 g/L or less, and preferably 0.1 g/L or more or 5 g/L or less.
• the first step may include removing at least a portion of the antioxidant. Removal of the antioxidant may be accomplished by treatment with activated carbon.
• the method for removing the surfactant in the first step may include, for example, activated carbon treatment, gel filtration treatment, etc.
• the method for removing the surfactant in the first step may preferably include activated carbon treatment.
• the method for removing the surfactant by activated carbon treatment may include, for example, contacting the plating composition with activated carbon. By using activated carbon, at least a portion of the surfactant can be more efficiently removed from the plating composition.
• a method for electrostatically adsorbing the surfactant for example, a method for contacting with an ion exchange resin
• activated carbon treatment for example, a method for contacting with an ion exchange resin
• Activated carbon is a porous material whose main component is carbon and that has been subjected to a chemical or physical activation process.
• the activated carbon used in the activated carbon process may be activated with a chemical agent or with a gas.
• the activated carbon may be powdered activated carbon, granular activated carbon, or a combination of these.
• the specific surface area of the activated carbon may be, for example, 200 m 2 /g or more and 1500 m 2 /g or less, preferably 300 m 2 /g or more or 700 m 2 /g or less.
• the specific surface area is measured using nitrogen gas after heat treatment at 200 ° C. for 6 hours as a pretreatment based on the BET (Brunauer Emmett Teller) theory.
• the average pore diameter of the activated carbon may be, for example, 1.5 nm or more and 3.5 nm or less, preferably 2.0 nm or more and 3.0 nm or less.
• the mesopore shape of the activated carbon may be, for example, 2 nm or more and 30 nm or less, preferably 4 nm or more and 10 nm or less, in terms of the average pore width on the adsorption side by the INNES method.
• the average pore width on the desorption side by the INNES method may be, for example, 2 nm or more and 5 nm or less, preferably 2 nm or more and 3.5 nm or less.
• the amount of activated carbon used for contact with the plating composition may be selected appropriately depending on the type of activated carbon.
• the amount of activated carbon used may be an amount that can remove at least a portion of the surfactant contained in the plating composition, and is preferably an amount sufficient to remove 50% by mass or more, 70% by mass or more, or 90% by mass or more of the surfactant.
• the amount of activated carbon used may be selected depending on the method of contact with the plating composition. For example, when contacting with the plating composition in one pass, a larger amount of activated carbon may be required than when contacting with the plating composition by circulating the plating composition.
• the plating composition may be brought into contact with the activated carbon by, for example, mixing the plating composition with the activated carbon and then performing solid-liquid separation, or by passing the plating composition through activated carbon held in a filter, cartridge, or the like.
• the contact temperature between the plating composition and the activated carbon may be, for example, 0°C or higher or 70°C or lower.
• a plating composition from which at least a part of the surfactant has been removed is introduced into the working electrode chamber of an electrochemical device having a working electrode and a counter electrode chamber having a counter electrode, the working electrode chamber and the counter electrode chamber being isolated by one type of membrane selected from the group consisting of an ion exchange membrane, a reverse osmosis membrane, and a nanofiltration membrane, and at least a part of the tin (IV) ions in the introduced plating composition are reduced to metallic tin using the working electrode as the cathode.
• An aqueous solution containing conductive ions may be placed in the counter electrode chamber of the electrochemical device. By placing an aqueous solution containing conductive ions in the counter electrode chamber, the tin (IV) ions can be reduced more efficiently.
• the material of the working electrode provided in the working electrode chamber may be, for example, gold, platinum, platinum-coated titanium, silver, nickel, graphite, tin, titanium, iridium oxide, etc.
• the material of the counter electrode may be, for example, platinum, platinum-coated titanium, gold, nickel, iridium oxide, titanium, graphite, palladium, etc.
• the working electrode chamber and the counter electrode chamber are separated by an ion exchange membrane. This allows the tin (IV) ion to be reduced more efficiently.
• the ion exchange membrane may be a cation exchange membrane, an anion exchange membrane, or a combination of both.
• the ion exchange membrane may be appropriately selected from commercially available ion exchange membranes.
• the ion exchange membrane may include at least a cation exchange membrane from the viewpoint of the reduction efficiency of the tin (IV) ion.
• the cation exchange membrane may include a copolymer of a fluororesin based on sulfonated tetrafluoroethylene.
• a membrane that is difficult for tin ions to pass through such as a reverse osmosis membrane (RO membrane) or a nanofiltration membrane (NF membrane, loose RO membrane, may be used.
• RO membrane reverse osmosis membrane
• NF membrane nanofiltration membrane
• the conductive ion-containing aqueous solution may contain at least water and a water-soluble metal salt.
• the water-soluble metal salt may contain, as metal ions, for example, alkali metal ions, alkaline earth metal ions, etc.
• the water-soluble metal salt may contain, as anions, for example, sulfate ions, nitrate ions, phosphate ions, etc.
• the second step at least a portion of the tin (IV) ions in the plating composition introduced into the working electrode chamber is reduced to metallic tin by a first electrolysis process using the working electrode as a cathode.
• the metallic tin produced by the reduction may be deposited, for example, on the working electrode.
• the current density in the electrolysis of tin (IV) ions may be, for example, 0.05 A/dm 2 or more and 1 A/dm 2 or less, and preferably 0.1 A/dm 2 or more or 0.5 A/dm 2 or less.
• the temperature in the electrolysis may be, for example, 30° C. or more and 80° C. or less, and preferably 35° C. or more or 75° C. or less.
• the time required for the electrolysis may be, for example, 10 minutes or more and 200 hours or less.
• the metallic tin produced by reduction in the second step is oxidized to tin (II) ions by a second electrolysis process using the working electrode as the anode.
• the metallic tin deposited on the working electrode in the second step may be oxidized to tin (II) ions by electrolysis using the working electrode as the anode. That is, the third step may be performed using the same electrochemical device following the reduction of tin (IV) ions in the second step.
• the current density in the electrolysis of metallic tin may be, for example, 0.5 A/ dm2 or more and 100 A/ dm2 or less.
• the temperature in the electrolysis of metallic tin may be, for example, 10°C or more and 80°C or less, and preferably 15°C or more or 75°C or less.
• the time required for electrolysis may be, for example, 0.2 hours or more and 10 hours or less.
• the method for regenerating a plating composition may further include a step of adding a surfactant to the plating composition after the third step.
• a plating composition to which a surfactant has been added By using a plating composition to which a surfactant has been added, a plating having a better surface is formed.
• the surfactant added may be the same type as the surfactant removed in the first step. Furthermore, the amount of surfactant added may be approximately the same as the amount removed in the first step.
• the plating composition regeneration device includes a surfactant removing means, a working electrode chamber including a working electrode, a counter electrode chamber including a counter electrode, and one type of membrane selected from the group consisting of an ion exchange membrane, a reverse osmosis membrane, and a nanofiltration membrane, which separates the working electrode chamber from the counter electrode chamber.
• the plating composition regeneration device can be used in the plating composition regeneration method described above.
• Examples of the surfactant removal means provided in the regeneration device include activated carbon treatment and gel filtration treatment.
• the surfactant removal means may preferably include activated carbon treatment. Removal of the surfactant by activated carbon treatment may include, for example, contacting the plating composition with activated carbon. By using activated carbon, the surfactant can be removed more efficiently from the plating composition.
• the contact between the plating composition and activated carbon may be achieved, for example, by passing the plating composition through activated carbon held in a cartridge or the like. That is, the regeneration device may include a cartridge filled with activated carbon and configured to allow the plating composition to pass through.
• the regeneration device may be an electrochemical device that includes a working electrode chamber, a counter electrode chamber, and one type of membrane selected from the group consisting of an ion exchange membrane, a reverse osmosis membrane, and a nanofiltration membrane that separates the working electrode chamber from the counter electrode chamber, and that is configured to enable electrolysis.
• the regeneration device may further include a power supply device, a control device, a temperature control device, etc. that enable the electrolysis process.
• a method for regenerating a plating composition comprising: removing at least a portion of the surfactant from a plating composition containing tin (IV) ions and the surfactant; introducing the plating composition from which at least a portion of the surfactant has been removed into a counter electrode chamber having a counter electrode and a working electrode chamber having a working electrode, the counter electrode chamber being isolated by a membrane selected from the group consisting of an ion exchange membrane, a reverse osmosis membrane, and a nanofiltration membrane; reducing at least a portion of the tin (IV) ions in the introduced plating composition to metallic tin using the working electrode as a cathode; and oxidizing at least a portion of the reduced metallic tin to tin (II) ions using the working electrode as an anode.
• ⁇ 4> A regeneration method according to any one of ⁇ 1> to ⁇ 3>, in which the pH of the working electrode chamber is 1 or more and 13 or less.
• ⁇ 5> The regeneration method according to any one of ⁇ 1> to ⁇ 4>, wherein the counter electrode chamber is provided with an aqueous solution containing conductive ions.
• ⁇ 6> The regeneration method according to any one of ⁇ 1> to ⁇ 5>, wherein removing at least a portion of the surfactant from the plating composition includes contacting the plating composition with activated carbon.
• ⁇ 7> The regeneration method according to any one of ⁇ 1> to ⁇ 6>, wherein the surfactant includes at least one selected from the group consisting of nonionic surfactants and cationic surfactants.
• a plating composition regeneration device comprising a surfactant removal means, a working electrode chamber having a working electrode, a counter electrode chamber having a counter electrode, and one type of membrane selected from the group consisting of an ion exchange membrane, a reverse osmosis membrane, and a nanofiltration membrane, isolating the working electrode chamber from the counter electrode chamber.
• a plating composition regeneration device in the plating composition regeneration method described in any one of ⁇ 1> to ⁇ 8>, the plating composition regeneration device comprising a surfactant removal means, a working electrode chamber having a working electrode, a counter electrode chamber having a counter electrode, and one type of membrane selected from the group consisting of an ion exchange membrane, a reverse osmosis membrane, and a nanofiltration membrane, isolating the working electrode chamber from the counter electrode chamber.
• a plating composition having the composition shown below was prepared using purified water, potassium stannate (IV) as a tin (IV) ion source, tin (II) methanesulfonate as a tin (II) ion source, gluconic acid, a cationic surfactant containing decyltrimethylammonium chloride, hydroquinone, and sodium methanesulfonate.
• Tin (IV) ion 0.16 mol/L Tin (II) ion: 0.04 mol/L
• Gluconic acid 0.8 mol/L Methanesulfonic acid: 1.2 mol/L
• Surfactant 1 g/L Hydroquinone: 1g/L Sodium ion: 1.4 mol/L
• Example 1 The plating composition 2L prepared above was passed through an activated carbon cartridge (MX manufactured by Kankyo Technos Co., Ltd.) attached to a filter at room temperature (25°C) and introduced into the working electrode chamber of an electrochemical device.
• the electrochemical device was equipped with a platinum-coated titanium electrode as a working electrode and a platinum-coated titanium electrode as a counter electrode, and the working electrode chamber and the counter electrode chamber were separated by a cation exchange membrane (Noafion (TM) 424).
• a 10g/L aqueous sodium sulfate solution was placed in the counter electrode chamber of the electrolysis device, and electrolysis treatment was performed for 1 hour at a liquid temperature of 40°C to 70°C, a current density of 0.1A/ dm2 to 0.5A/ dm2 , and a current value of 36.1A.
• electrolysis treatment was performed for 0.5 hours at a current value of 34.3 A and a current density of 1 A/ dm2 to 80 A/ dm2 with the working electrode as the anode and at a solution temperature of 20°C to 70°C, to obtain a regenerated plating composition as a plating composition of the treated gas.
• concentrations of tin(IV) ions and tin(II) ions in the regenerated plating composition were evaluated using a combination of redox titration and inductively coupled plasma atomic emission spectrometry (ICP-AES). Specifically, the concentration of tin(II) ions was calculated by titrating with an iodine standard solution in 2M hydrochloric acid using starch as an indicator. The total concentration of tin ions was calculated using ICP-AES, and the concentration of tin(IV) ions was calculated by subtracting the concentration of tin(II) ions.
• ICP-AES inductively coupled plasma atomic emission spectrometry
• the concentration of tin (IV) ions in the regenerated plating composition was 0.04 mol/L, and the concentration of tin (II) ions was 0.16 mol/L. From these results, the reduction efficiency of tin (IV) ions was evaluated to be 95%. The reduction efficiency was calculated by dividing the integrated current value in the third process by half the integrated current value in the second process.
• the activated carbon contained in the activated carbon cartridge (MX) had a specific surface area of 437 m2 /g and an average pore diameter of 2.4 nm as measured by the BET method, and the mesopore shape had an average pore width of 6.0 nm on the adsorption side and an average pore width of 2.1 nm on the desorption side as measured by the INNES method.
• the activated carbon contained in the activated carbon cartridge (YCC-R) had a specific surface area of 1237 m2 /g and an average pore diameter of 1.8 nm as measured by the BET method, and the mesopore shape had an average pore width of 2.5 nm on the adsorption side and an average pore width of 4.0 nm on the desorption side as measured by the INNES method.
• Comparative Example 1 The electrolysis treatment was carried out twice in the same manner as in Example 1, except that the plating composition was introduced directly into the working electrode chamber without passing it through the activated carbon cartridge, to obtain a plating composition after treatment.
• the concentrations of tin(IV) ions and tin(II) ions in the resulting plating composition after treatment were evaluated in the same manner, and the concentration of tin(IV) ions was found to be 0.19 mol/L, and the concentration of tin(II) ions was found to be 0.01 mol/L. From these results, the reduction efficiency of tin(IV) ions was evaluated to be 0%.
• Comparative Example 2 The electrolysis treatment was carried out twice in the same manner as in Example 1, except that an electrolysis apparatus in which the working electrode chamber and the counter electrode chamber were not separated by a cation exchange membrane and were in a state in which liquids could pass through each other was used, to obtain a plating composition after treatment.
• the concentrations of tin (IV) ions and tin (II) ions in the resulting plating composition after treatment were evaluated in the same manner, and the concentration of tin (IV) ions was found to be 0.20 mol/L, and the concentration of tin (II) ions was found to be 0.0 mol/L. From these results, the reduction efficiency of tin (IV) ions was evaluated to be 0%.

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