A method for efficiently reducing trivalent iron ions in a plating solution for ultra-thin electrolytic iron foil

Abstract

The invention relates to the technical field of manufacturing ultra-thin electrolytic iron foil, and specifically discloses a method for efficiently reducing trivalent iron ions in a plating solution for ultra-thin electrolytic iron foil, wherein an iron-containing plating solution is placed in a container, the pH of the iron-containing plating solution is adjusted to 0.3-0.5, tungsten powder is then added to the iron-containing plating solution, the container is sealed, and the container is placed in a water bath at 50-80°C, stirred for 30-60 minutes, and then allowed to stand for at least 24 hours, so that the trivalent iron ions in the iron-containing plating solution are fully reduced. The invention can efficiently reduce the trivalent iron ions in the iron-containing plating solution, and does not need to add an antioxidant and increase the content of ferrous ions in the iron-containing plating solution, thereby ensuring the quality of the coating.

Description

Technical Field

[0001] The invention belongs to the technical field of ultra-thin electrolytic iron foil manufacturing, and in particular relates to a method for efficiently reducing trivalent iron ions in a plating solution for ultra-thin electrolytic iron foil. Background Art

[0002] Ultra-thin electrolytic iron foil has excellent properties such as high mechanical strength, high magnetic permeability, good magnetic absorption ability, and electromagnetic wave shielding ability. It has very broad application prospects in electronic components, aerospace, optoelectronic materials, 5G and other fields.

[0003] However, during the electroplating process of iron, the presence of trivalent iron ions in the iron-containing plating solution will have a great impact on the performance of the coating. The trivalent iron ions will produce iron hydroxide precipitation at pH=3. Especially when the current density is high, the hydrogen ions near the surface of the coating will be consumed more, which will lead to a local increase in pH and precipitation of trivalent iron ions, resulting in increased porosity and brittleness of the coating, black streaks on the surface and other quality problems. Therefore, how to control the concentration of trivalent iron ions in the iron-containing plating solution is crucial for electrolytic iron foil.

[0004] At present, there are generally two methods to control the trivalent iron ions in the iron-containing plating solution: one is to add a small amount of antioxidants, such as ascorbic acid, to the iron-containing plating solution, which can effectively prevent the oxidation of divalent iron. However, a common problem with this method is that the antioxidants used are mostly organic solvents, which need to be continuously replenished. After long-term use, oxides will accumulate in the plating solution and have a negative impact on the coating. The other is to use iron filings to reduce the trivalent iron ions in the iron plating solution. However, the reduction of trivalent iron ions by iron filings will inevitably increase the content of ferrous ions in the solution, resulting in serious quality problems such as uneven thickness, coarse crystals, pinholes, weak adhesion, grayness, or even no coating on the surface of the coating.

[0005] Therefore, providing a method for efficiently reducing ferric ions in an iron-containing plating solution without adding an antioxidant and without increasing the ferrous ion content in the iron-containing plating solution to ensure the quality of the coating is a technical problem that technicians in this field hope to solve. Summary of the invention

[0006] In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide a method for efficiently reducing trivalent ferrous ions in a plating solution for ultra-thin electrolytic iron foil. The present invention can efficiently reduce trivalent ferrous ions in an iron-containing plating solution without adding antioxidants or increasing the content of ferrous ions in the iron-containing plating solution, thereby ensuring the quality of the coating.

[0007] The technical solution of the present invention is achieved in this way:

[0008] A method for efficiently reducing trivalent iron ions in a plating solution for ultra-thin electrolytic iron foil comprises placing an iron-containing plating solution in a container, adjusting the pH of the iron-containing plating solution to 0.3-0.5, adding tungsten powder to the iron-containing plating solution, sealing the container, placing the container in a water bath at 50-80°C, stirring the reaction for 30-60 minutes, and then standing for at least 24 hours, so that the trivalent iron ions in the iron-containing plating solution are fully reduced.

[0009] Furthermore, tungsten powder is used to adjust the pH of the iron-containing plating solution.

[0010] Furthermore, the molar ratio of the tungsten powder to the trivalent iron ions in the iron-containing plating solution is 1:3-4.

[0011] Furthermore, the molar ratio of the tungsten powder to the trivalent iron ions in the iron-containing plating solution is 1:3.2.

[0012] Furthermore, the water bath reaction temperature is 60°C.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] 1. The present invention uses tungsten powder to adjust the pH value of the iron-containing plating solution without introducing impurities. At the same time, tungsten powder is used to reduce the trivalent iron ions (Fe 3+ ), which can effectively reduce the trivalent iron ions in the iron-containing plating solution to divalent iron ions (Fe 2 + ), and the generated product is mainly precipitated in the form of tetravalent tungsten oxide, so that the total iron content will not be increased, thereby avoiding serious quality problems such as uneven thickness, coarse crystals, pinholes, weak adhesion, grayness or even no coating on the surface of the coating. At the same time, the present invention does not use antioxidants, does not introduce impurity ions, and ensures the quality of the coating while reducing costs.

[0015] In addition, the generated tetravalent tungsten oxide is insoluble in acidic solution. After washing and drying the precipitate, the tungsten powder can be recycled by reducing it with hydrogen, carbon, etc.

[0016] 2. The present invention uses tungsten powder to reduce trivalent iron ions, and the reduction rate is high, which can reach 95.24%. It is also simple to operate and good for the environment, and has wide promotion and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 - Example 1 Fe in iron-containing plating solution 3+ Concentration curves with different tungsten contents.

[0018] Figure 2 - Example 2 Fe in iron-containing plating solution 3+ Concentration curve with different tungsten contents.

[0019] Figure 3- pH value change curve before and after the reaction of Example 2.

[0020] Figure 4 - Example 2 Total iron content change curve before and after the reaction.

[0021] Figure 5 -Energy spectrum analysis diagram of the precipitate after the reaction of Example 2.

[0022] Figure 6 -Photographs of Example 2 using acetone, boric acid and ammonia to dissolve the precipitate. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0024] The components of the prepared iron-containing plating solution are: Fe 2+ 3.00mol / L; tungsten powder 12.00g / L; NaCl 0.10mol / L; boric acid 0.20mol / L; sodium citrate 0.05mol / L. At 60℃, the current density is 1.50A / dm 2 After electroplating for a period of time, the components of the iron-containing plating solution are: Fe 2+ 2.30mol / L;Fe 3+ 0.2mol / L; tungsten powder 11.41g / L; NaCl 0.09mol / L; boric acid 0.18mol / L; sodium citrate 0.045mol / L. The following examples use this iron-containing plating solution to carry out the following research.

[0025] Example 1

[0026] Take five 200mL portions of iron-containing plating solution into five beakers. 3+ The molar concentration of the solution was 0.2 mol / L, tungsten powder was added to adjust the pH of the iron-containing plating solution to 0.3, and then 0 g, 0.25 g, 0.5 g, 1.0 g, and 2.0 g of tungsten powder were added to five beakers, respectively. The beakers were sealed with plastic wrap and stirred in a water bath at 60 °C for 30 min. The Fe content in the solution was detected by ultraviolet spectrophotometer using sulfosalicylic acid as an indicator. 3+ concentration.

[0027] In this embodiment, Fe 3+ The concentration curves with different tungsten contents are as follows: Figure 1 As shown in the figure, it can be seen that as the concentration of tungsten powder increases, Fe 3+ The concentration gradually decreases, but the required tungsten powder concentration is too high, and the economic benefits are not good.

[0028] Example 2

[0029] Take five 200mL portions of iron-containing plating solution into five beakers. 3+ The molar concentration of the solution was 0.2 mol / L, tungsten powder was added to adjust the pH of the iron-containing plating solution to 0.3, and then 0 g, 0.12 g, 0.24 g, 0.36 g, and 0.48 g of tungsten powder were added to five beakers, respectively. The beakers were sealed with plastic wrap and stirred in a water bath at 60 °C for 60 min. The Fe content in the solution was detected by ultraviolet spectrophotometer using sulfosalicylic acid as an indicator. 3+ concentration.

[0030] In this embodiment, Fe 3+ The concentration curves with different tungsten contents are as follows: Figure 2 As shown in the figure, it can be seen that with the increase of tungsten powder concentration, Fe 3+ The concentration gradually decreases and approaches zero.

[0031] The pH value change curve before and after the reaction in this embodiment is as follows Figure 3 As shown in the figure, it can be seen that as the concentration of tungsten powder gradually increases, the pH value gradually decreases and tends to be flat after pH=0.5.

[0032] The second to fifth portions after the reaction were oxidized with excess hydrogen peroxide, heated in a small electric furnace for 30 to 60 minutes, and the amount of water lost during heating was replenished with deionized water. Figure 4 Compared with the initial total iron content before the reaction (the first portion), the content of different tungsten powders after the reaction is basically the total iron (Fe 3+ , Fe 2+ ) content has not changed, Figure 5 Energy spectrum analysis of the precipitate after the reaction shows that the content of Fe and Cl elements is almost zero, and W:O=1:3. In the thermogravimetric analysis, the weight of the precipitate decreases by 5% before and after calcination. Figure 3 The pH of the system with different contents of tungsten powder decreases with the increase of tungsten powder content, which proves that the acidity of the system increases after the reaction. The dissolution of the precipitate by acetone, boric acid and ammonia water is shown in the dissolution photos. Figure 6 As shown, corresponding to Figure 6 A, 6B, 6C, as can be seen from the figure, are insoluble in acetone, dissolve in boric acid to show a slight red color, and dissolve in ammonia water to show red color.

[0033] In summary: the oxidant in the reaction system is Fe 3+ Since the oxidizing property of the oxidant is greater than that of the oxidation product, the tungsten in the precipitate cannot be in the 5- or 6-valent state, and the precipitate basically does not contain Fe and Cl elements in the energy spectrum analysis. The weight loss of 1- and 2-valent tungsten powder does not meet the 5% weight reduction in the thermogravimetric analysis, so it cannot be 1- or 2-valent tungsten. The 3-valent tungsten is soluble in organic solvents, but the precipitate is insoluble in acetone, and the fully reacted ratio in Example 2 is W:Fe3+ =1:3.2 does not meet the requirement of 1:3, so it is not trivalent. The tetravalent W WO2·H2O meets the 5% weight reduction of thermogravimetric analysis. Combining the phenomenon that the acidity in the system increases after the previous reaction and the total iron does not change substantially, the main reaction chemical equation of the present invention can be deduced as: 2H2O+4Fe 3+ +W=WO2+4Fe 2+ +4H + .

[0034] Example 3

[0035] Take six 200mL portions of iron-containing plating solution into six beakers. 3+ The molar concentration of the solution was 0.2 mol / L, and then tungsten powder was added to adjust the pH of the iron-containing plating solution to 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6, respectively. Then, 1.0 g of tungsten powder was added to six beakers, which were sealed with plastic wrap and stirred in a water bath at 60 °C for 30 min. The Fe content in the solution was detected by ultraviolet spectrophotometer using sulfosalicylic acid as an indicator. 3+ concentration.

[0036] As the pH increases, the hydrogen evolution reaction gradually weakens, and the current efficiency is higher at lower pH, but decreases at higher pH. In addition, when the pH reaches 0.6, the tungsten powder becomes insoluble. Therefore, controlling the appropriate pH not only helps to improve the current efficiency, but also effectively reduces the generation of unnecessary by-products and ensures the maximum utilization of materials.

[0037] Example 4

[0038] Take two 200mL portions of iron-containing plating solution into two beakers. 3+ The molar concentration was 0.2 mol / L. After adding 1.2 g of tungsten powder directly to one portion, the portion was sealed with plastic wrap and stirred in a water bath at 60°C for 30 min. The Fe content in the solution was detected by UV spectrophotometer using sulfosalicylic acid as an indicator. 3+ concentration; add 0.2g tungsten powder to another portion to adjust the pH of the iron-containing plating solution to 0.4, then add 1.0g tungsten powder, seal with plastic wrap, and stir magnetically in a 60℃ water bath for 30min. Use sulfosalicylic acid as an indicator and use an ultraviolet spectrophotometer to detect Fe in the solution. 3+ The results are shown in the following table.

[0039]

[0040] From the table above, we can see that when tungsten powder is added directly without adjusting the pH value, the reduction rate of iron ions is only 25%. However, after adding tungsten powder to adjust the pH value in advance, the reduction efficiency of iron ions reaches 95%. This shows that adding a small amount of tungsten powder to adjust the pH value in advance can significantly increase the reduction rate of Fe 3+ This is because under appropriate pH conditions, the surface activity of tungsten powder is higher, which is more conducive to Fe 3+ reduction reaction.

[0041] Finally, it should be noted that the above embodiments of the present invention are only examples for illustrating the present invention, and are not intended to limit the implementation methods of the present invention. For those skilled in the art, other different forms of changes and modifications can be made based on the above description. It is impossible to list all implementation methods here. Any obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for efficiently reducing trivalent iron ions in a plating solution for ultra-thin electrolytic iron foil, characterized in that: The iron-containing plating solution is placed in a container, and tungsten powder is used to adjust the pH value of the iron-containing plating solution to 0.3-0.

5. Then, tungsten powder is added to the iron-containing plating solution. The container is sealed and placed in a water bath at 50-80°C, and stirred for 30-60 minutes, and then allowed to stand for at least 24 hours, so that the trivalent iron ions in the iron-containing plating solution are fully reduced.

2. The method for efficiently reducing trivalent iron ions in a plating solution for ultra-thin electrolytic iron foil according to claim 1, characterized in that: The molar ratio of tungsten powder to trivalent iron ions in the iron-containing plating solution is 1:3~4.

3. The method for efficiently reducing trivalent iron ions in a plating solution for ultra-thin electrolytic iron foil according to claim 2, characterized in that: The molar ratio of tungsten powder to trivalent iron ions in the iron-containing plating solution is 1:3.

2.

4. The method for efficiently reducing trivalent iron ions in a plating solution for ultra-thin electrolytic iron foil according to claim 1, characterized in that: The water bath reaction temperature was 60°C.

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