A method for reducing the turbidity of stannous sulfate products

Abstract

A method for reducing the turbidity of stannous sulfate products includes the following steps: (1) Electrolysis: In a sulfur dioxide reducing atmosphere, an ion-exchange membrane electrolysis method is used to place a sulfuric acid solution into an electrolytic cell and electrolyze it with a refined tin electrode to obtain a stannous sulfate solution; (2) Sedimentation: In a sulfur dioxide reducing atmosphere, the stannous sulfate solution is allowed to settle naturally, and the supernatant is collected; (3) The supernatant is concentrated and crystallized, then subjected to solid-liquid separation, washing, centrifugation, and drying to obtain the stannous sulfate product. This invention uses SO2 as a reducing gas, which simultaneously reduces the tetravalent tin in the stannous sulfate solution to divalent tin during electrolysis, thereby reducing the content of tetravalent tin in the solution and thus reducing the turbidity of the product. It eliminates the need for capture reduction and secondary reduction treatment after electrolysis, improving production efficiency while ensuring product quality.

Description

Technical Field

[0001] This invention belongs to the field of stannous sulfate production, and specifically relates to a method for reducing the turbidity of stannous sulfate products. Background Technology

[0002] Stannous sulfate is a white or light yellow crystalline powder. It is soluble in water and dilute sulfuric acid, decomposing rapidly in aqueous solutions. It begins to decompose into basic salts above 360°C and slowly oxidizes in air, turning slightly yellow. It is mainly used in the electroplating industry for tin plating, anodizing and coloring aluminum alloy surfaces, as a mordant in the printing and dyeing industry, and as a hydrogen peroxide remover. It is also used in tin plating and as a chemical reagent, such as in acidic electroplating of alloys, tinplate, cylinder pistons, and steel wire, and in bright tin plating of electronic components. Additionally, it is used for anodizing and coloring coatings on aluminum alloy products, as a mordant in the printing and dyeing industry, and as a hydrogen peroxide remover in organic solvents.

[0003] Currently, the main method for producing stannous sulfate is as follows: stannous sulfate solution is obtained by electrolyzing tin plates in sulfuric acid solvent, and then concentrated to obtain stannous sulfate product. For example, the ion-exchange membrane electrolysis method for preparing high-purity stannous sulfate, as disclosed in Wei Qing's "Preparation of High-Purity Stannous Sulfate by Ion-Exchange Membrane Electrolysis Method," *Journal of Wuyi University: Natural Science Edition*, 2000, 14(1):55-59, generally contains 0.1–0.5 g / L tetravalent tin in the stannous sulfate solution obtained after electrolysis. The stannous sulfate product produced using such a solution contains 0.1–0.5% tetravalent tin. When the tetravalent tin content reaches 0.5%, the product is yellowish and has a turbidity ≥50 degrees. Simultaneously, when using the membrane electrolysis method to produce stannous sulfate, a certain amount of anode mud is generated on the anode plate during electrolysis. The anode mud contains Sn. 4+ Metal ions are generated; the resulting anode mud settles at the bottom of the diaphragm tank, and when it accumulates to a certain extent, it will affect the electrolysis efficiency of the entire electrolysis process.

[0004] Application number CN201710554713.6 discloses a method for reducing the tetravalent tin content in stannous sulfate. This method involves laying a layer of tin granules at the bottom of a stannous sulfate electrolytic cell, adding acetone oxime, sodium dithionite, sodium sulfite, hydrazine, and other oxygen scavengers to dilute sulfuric acid, controlling the electrolytic cell voltage and the tin ion concentration in the electrolyte, and using isopropanol, acetone, and butanone to reduce the tetravalent tin content in the stannous sulfate product. The method produces stannous sulfate with a tetravalent tin content ≤0.07%. However, the tin granules used in this method are laid at the bottom of the electrolytic cell, and the tin anode plate will generate anode sludge during electrolysis, which will cover the tin granules at the bottom of the cell. Since the tetravalent tin is mainly in the electrolyte, the reduction effect is poor. Furthermore, the oxygen scavengers in dilute sulfuric acid introduce impurities such as sodium salts, and hydrazine is toxic, posing certain environmental and operational risks.

[0005] Application No. 202210420625.8 discloses a method for deeply reducing tetravalent tin in stannous sulfate solution, comprising the following steps: (1) heating the solution; (2) capture and reduction; (3) filtration and separation; (4) secondary heat preservation and reduction; (5) cooling and settling. This invention utilizes capture and reduction, secondary heat preservation and reduction, and sedimentation to deeply reduce the tetravalent tin in stannous sulfate solution, lowering the concentration from 0.1–0.5 g / L to below 0.05 g / L. The resulting stannous sulfate solution is clear and transparent, with turbidity decreasing from ≥50 degrees to below 10 degrees and color decreasing from 156 to below 35. The stannous sulfate product produced using this method has a purity ≥99.70% and a shelf life of over 2 years, making it suitable as a dedicated stannous sulfate for the electroplating and electrolytic coloring industries. Although this method can effectively reduce the turbidity of the product, the processing of stannous sulfate mainly takes place in the later stage of electrolysis, which prolongs the later processing time and is not conducive to improving the production efficiency of the product. Summary of the Invention

[0006] The purpose of this invention is to solve the above-mentioned technical problems and provide a method for reducing the turbidity of stannous sulfate products without increasing post-treatment.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] A method for reducing the turbidity of stannous sulfate products includes the following steps:

[0009] (1) Electrolysis: In a sulfur dioxide reducing atmosphere, an ion-exchange membrane electrolysis method is used to put sulfuric acid solution into an electrolytic cell and electrolyze it with a refined tin plate to obtain stannous sulfate solution;

[0010] (2) Sedimentation: In a sulfur dioxide reducing atmosphere, allow the stannous sulfate solution to settle naturally and take the supernatant;

[0011] (3) The supernatant is concentrated and crystallized, then separated into solid and liquid, washed, centrifuged and dried to obtain stannous sulfate product.

[0012] As a further technical solution, in the reducing atmosphere described above, the partial pressure of sulfur dioxide is 100~150 kPa.

[0013] As a further technical solution, the concentration of the sulfuric acid solution mentioned above is 10-15 g / L.

[0014] As a further technical solution, the voltage of the electrolytic cell described above is 1.8V to 2.2V, and the electrolysis reaction time is 16 to 17 hours.

[0015] As a further technical solution, the natural settling time described above is 1 to 2 days.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: Since SO2 can ionize into hydrogen ions when dissolved in water, it can play a role in reduction and leaching in the sulfuric acid system. Therefore, the present invention uses SO2 as a reducing gas to construct an SO2-H2SO4 equilibrium system with the sulfuric acid solution. During the electrolysis of the sulfuric acid solution, the main reaction is Sn-2e=Sn. 2+ The reaction will occur simultaneously with Sn. 2+ -2e=Sn 4+ The side reaction is mitigated because electrolysis is performed under reducing conditions. During electrolysis, tetravalent tin in the stannous sulfate solution is simultaneously reduced to divalent tin, lowering the tetravalent tin content in the solution and thus reducing the turbidity of the product. This eliminates the need for post-electrolysis capture reduction and secondary reduction treatment, improving production efficiency while ensuring product quality. As anode mud is continuously generated, the solution potential increases, affecting electrolysis efficiency. This invention uses sulfur dioxide to effectively leach and reduce tetravalent tin in the anode mud to divalent tin, reducing the amount of anode mud generated and lowering the solution potential, thereby ensuring the effective operation of the entire electrolysis process and reducing the frequency of mud discharge. Detailed Implementation

[0017] The present invention will be further described in detail below with reference to the embodiments, but the implementation of the present invention is not limited to the scope shown in the embodiments.

[0018] Example 1:

[0019] A method for reducing the turbidity of stannous sulfate products includes the following steps:

[0020] (1) Electrolysis: In a sulfur dioxide reducing atmosphere, an ion-exchange membrane electrolysis method is used to place a sulfuric acid solution into an electrolytic cell and electrolyze it with a tin electrode to obtain a tin sulfate solution; the partial pressure of sulfur dioxide is 100 kPa, the concentration of sulfuric acid solution is 10 g / L, the voltage of the electrolytic cell is 1.8 V to 2.2 V, and the electrolysis reaction time is 17 h;

[0021] (2) Settling: In a sulfur dioxide reducing atmosphere, allow the stannous sulfate solution to settle naturally in the electrolytic cell for 1 day, and take the supernatant;

[0022] (3) After filtration, the supernatant is concentrated and crystallized at a temperature of 80°C and a vacuum of 0.06 MPa. After solid-liquid separation, the stannous sulfate crystals are washed with ethanol solution for 10 min, then centrifuged and dried to obtain the stannous sulfate product.

[0023] Example 2:

[0024] A method for reducing the turbidity of stannous sulfate products includes the following steps:

[0025] (1) Electrolysis: In a sulfur dioxide reducing atmosphere, an ion-exchange membrane electrolysis method is used to place sulfuric acid solution into an electrolytic cell and electrolyze it with a tin electrode to obtain stannous sulfate solution; the partial pressure of sulfur dioxide is 120 kPa, the concentration of sulfuric acid solution is 12 g / L, the voltage of the electrolytic cell is 1.8 V to 2.2 V, and the electrolysis reaction time is 16 h;

[0026] (2) Settling: In a sulfur dioxide reducing atmosphere, allow the stannous sulfate solution to settle naturally in the electrolytic cell for 1 day, and take the supernatant;

[0027] (3) After filtration, the supernatant is concentrated and crystallized at a temperature of 80°C and a vacuum of 0.06 MPa. After solid-liquid separation, the stannous sulfate crystals are washed with ethanol solution for 10 min, then centrifuged and dried to obtain the stannous sulfate product.

[0028] Example 3:

[0029] A method for reducing the turbidity of stannous sulfate products includes the following steps:

[0030] (1) Electrolysis: In a sulfur dioxide reducing atmosphere, an ion-exchange membrane electrolysis method is used to place sulfuric acid solution into an electrolytic cell and electrolyze it with a tin electrode to obtain stannous sulfate solution; the partial pressure of sulfur dioxide is 150 kPa, the concentration of sulfuric acid solution is 15 g / L, the voltage of the electrolytic cell is 1.8 V to 2.2 V, and the electrolysis reaction time is 16 h;

[0031] (2) Settling: In a sulfur dioxide reducing atmosphere, allow the stannous sulfate solution to settle naturally in the electrolytic cell for 1 day, and take the supernatant;

[0032] (3) After filtration, the supernatant is concentrated and crystallized at a temperature of 80°C and a vacuum of 0.06 MPa. After solid-liquid separation, the stannous sulfate crystals are washed with ethanol solution for 5-10 min, then centrifuged and dried to obtain the stannous sulfate product.

[0033] The test results of stannous sulfate products in Examples 1-3 are shown in Table 1:

[0034] Table 1

[0035] Example <![CDATA[SnSO4(%)]]> Turbidity Example 1 99.6 9 Example 2 99.7 8 Example 3 99.5 9 industry standard ≥99.0 \

[0036] As can be seen from Examples 1-3, under the same voltage, the electrolysis time of the present invention is reduced compared to the 18-20h of the prior art, and the electrolysis efficiency is higher. The product of the present invention has low turbidity and can reduce the tetravalent tin content in the product without introducing too many additives and steps.

[0037] The above embodiments are merely specific examples to further illustrate the purpose, technical solution, and beneficial effects of the present invention, and the present invention is not limited thereto. Any modifications, equivalent substitutions, improvements, etc., made within the scope of the disclosure of the present invention are included within the protection scope of the present invention.

Claims

1. A method for reducing the turbidity of stannous sulfate products, characterized in that, Includes the following steps: (1) Electrolysis: In a sulfur dioxide reducing atmosphere, an ion-exchange membrane electrolysis method is used to place a sulfuric acid solution into an electrolytic cell and electrolyze it with a tin electrode to obtain a tin sulfate solution; in the reducing atmosphere, the partial pressure of sulfur dioxide is 100~150kPa and the concentration of the sulfuric acid solution is 10-15g / L. (2) Sedimentation: In a sulfur dioxide reducing atmosphere, allow the stannous sulfate solution to settle naturally and take the supernatant; (3) The supernatant is concentrated and crystallized, then separated into solid and liquid, washed, centrifuged and dried to obtain stannous sulfate product.

2. The method for reducing the turbidity of stannous sulfate products according to claim 1, characterized in that: The voltage of the electrolytic cell is 1.8V to 2.2V, and the electrolysis reaction time is 16 to 17 hours.

3. The method for reducing the turbidity of stannous sulfate products according to claim 1, characterized in that: The natural settling time is 1 to 2 days.