Method for directly preparing sodium stannate from tin stripping liquid

Abstract

The invention relates to a method for directly preparing sodium stannate from a tin stripping liquid, which comprises the following steps: (1) carrying out first alkali treatment on the tin stripping liquid, and carrying out solid-liquid separation to obtain copper oxide mud and an alkali treatment liquid; (2) sequentially carrying out neutralization treatment, solid-liquid separation and water washing treatment on the alkali treatment liquid to obtain tin sludge; and (3) carrying out second alkali treatment and evaporative crystallization treatment on the tin sludge to obtain sodium stannate. According to the method disclosed by the invention, soluble impurities are removed by adopting neutralization treatment and water washing treatment methods, so that recycling of copper and direct preparation of sodium stannate can be realized at the same time, and the method has relatively great advancement and economical efficiency.

Description

Technical Field

[0001] This invention relates to the field of resource secondary utilization technology, and in particular to a method for directly preparing sodium stannate from tin stripping solution. Background Technology

[0002] PCB (Printed Circuit Board) manufacturing is an industry that generates a large amount of liquid / solid industrial waste. One type of liquid waste (referred to as waste liquid) is generated when liquids in the working tanks of various processes are discarded or changed. It is characterized by high concentrations of pollutants, diverse types, and complex compositions. Solder stripping is a process in PCB manufacturing that generates a large amount of wastewater. The resulting solder stripping solution has a high heavy metal content (total metal content can reach over 100g / L), a high pollution index, high free acidity, and a complex composition. It generally contains acids (nitric acid, sulfuric acid, hydrochloric acid, and other organic acids), accelerators, surfactants, nitrogen oxide inhibitors, heavy metal complexing agents, copper corrosion inhibitors, and many other components, making it difficult to treat using conventional methods. How to effectively treat waste solder stripping water has become a major challenge for PCB manufacturers.

[0003] CN110065965B discloses a composite additive and method for enhancing the preparation of sodium stannate by soda roasting of cassiterite concentrate. The composite additive includes a carbonaceous reducing agent, metallic tin powder, and stannous oxide powder. The method for enhancing the preparation of sodium stannate by soda roasting of cassiterite concentrate using this composite additive is as follows: cassiterite concentrate, sodium carbonate, and the composite additive are mixed, ground, and then roasted under a protective atmosphere. The resulting roasted product is then subjected to cooling, crushing, grinding and leaching, solid-liquid separation, purification and impurity removal, and concentration and crystallization to obtain sodium stannate. Compared with existing reduction roasting processes for preparing sodium stannate, this method significantly improves the sodium stannate yield and directly uses cassiterite concentrate as the tin source, making the raw material widely available and inexpensive. In particular, it achieves low-temperature solid-phase roasting under an inert atmosphere, avoiding the introduction of reducing gases, optimizing the experimental process, and facilitating industrial production. It optimizes the sodium stannate calcination process and improves the sodium stannate yield of the soda roasting process; however, the process still requires pyrometallurgical treatment.

[0004] CN114804458B relates to a method for recycling waste tin stripping solution. The method includes: solid-liquid separation of the waste tin stripping solution to obtain a liquid phase and a precipitate phase; sequentially subjecting the precipitate phase to a first washing and alkaline treatment, followed by solid-liquid separation to obtain a copper oxide phase and an alkaline treatment solution; electrolyzing the alkaline treatment solution to obtain electrolytic tin; and sequentially subjecting the electrolytic tin to a second washing and acidic tin plating agent treatment to obtain a tin plating agent product. This invention provides a recycling method that employs a segmented treatment approach for specific waste tin stripping solutions. The liquid phase after solid-liquid separation is recycled as tin stripping solution, and the precipitate phase undergoes specific alkaline and electrolytic treatments to achieve separate recovery of copper and tin. Simultaneously, the electrolyzed liquid phase can be returned to the alkaline treatment process, achieving a closed-loop process and realizing the green treatment of waste tin stripping solution. It utilizes the principle that tin dissolves in alkali to obtain an alkaline sodium stannate solution, thus achieving the separation of tin and copper; however, the subsequent direction is to electrolyze sodium stannate to obtain elemental tin, and then oxidize the elemental tin to obtain tin products; there is still a waste of energy in the reduction + oxidation process.

[0005] The aforementioned existing technologies all suffer from long processing steps and high processing costs. Therefore, there is an urgent need for a new method to directly prepare sodium stannate from tin stripping solution. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a method for directly preparing sodium stannate from tin stripping solution. By employing alkali treatment and water washing processes, soluble substances are separated from tin sludge, significantly improving the purity of the sodium stannate product. This method simultaneously realizes the resource utilization of copper and the direct preparation of sodium stannate, demonstrating significant advancement and economic efficiency.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] This invention provides a method for directly preparing sodium stannate from a tin stripping solution, the method comprising:

[0009] (1) The tin stripping solution is subjected to a first alkali treatment, and after solid-liquid separation, copper oxide mud and alkali treatment solution are obtained;

[0010] (2) The alkaline treatment solution is subjected to neutralization, solid-liquid separation and water washing in sequence to obtain tin mud;

[0011] (3) The tin mud is subjected to a second alkali treatment and evaporation crystallization treatment to obtain the sodium stannate.

[0012] The method of the present invention employs a combination of first alkali treatment, neutralization treatment, water washing treatment, second alkali treatment, and evaporation crystallization treatment, which can simultaneously realize the resource recovery of copper and the direct preparation of sodium stannate; the water washing treatment can remove soluble impurities from tin mud, thereby improving the purity of sodium stannate products.

[0013] Since tin hydroxide is an amphoteric substance, soluble in both acids and alkalis, this invention first uses a first alkali treatment to generate copper oxide precipitate, followed by neutralization to generate tin hydroxide precipitate. Water washing is then used to remove soluble impurities from the tin hydroxide sludge, improving its purity. A second alkali treatment dissolves the tin hydroxide precipitate, generating sodium stannate. Pure sodium stannate is then obtained through evaporation and crystallization. The possible chemical reactions involved are as follows:

[0014] .

[0015] As a preferred technical solution of the present invention, the alkaline solution used for the first alkaline treatment includes sodium hydroxide; the mass concentration of the alkaline solution is 40%~50%, such as 40%, 42%, 44%, 46%, 48%, 50%, etc., but is not limited to the listed values, and other unlisted values ​​within the above range are also applicable.

[0016] Preferably, the content of free sodium hydroxide in the solution after the first alkali treatment is 7.5% to 20%, such as 7.5%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0017] Preferably, the pH of the solution after the first alkali treatment is 14.2 to 14.8, such as 14.2, 14.3, 14.4, 14.5, 14.6, 14.7, 14.8, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0018] Preferably, the temperature of the first alkali treatment is greater than 90°C, such as 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0019] Preferably, the treatment time of the first alkali is 4 to 6 hours, such as 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0020] As a preferred technical solution of the present invention, the copper oxide sludge obtained in step (1) is cleaned to obtain copper oxide product.

[0021] Preferably, the cleaning agent for the cleaning treatment includes a sodium hydroxide solution; the mass fraction of the sodium hydroxide solution is 0.5% to 2%, for example, 0.5%, 1%, 1.5%, 2%, etc., but is not limited to the listed values, and other unlisted values ​​within the above range are also applicable.

[0022] In this invention, copper oxide sludge is cleaned until the tin content in the cleaning solution is less than 1000 ppm, and more than 96% of the tin is transferred to an alkaline solution.

[0023] Preferably, the solid-liquid ratio of the copper oxide sludge to the cleaning agent is 1:(2~3), such as 1:2, 1:2.2, 1:2.4, 1:2.6, 1:2.8, 1:3, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0024] As a preferred embodiment of the present invention, the neutralizing agent used in the neutralization treatment includes nitric acid.

[0025] Preferably, the pH of the neutralized solution is 9 to 10, such as 9, 9.2, 9.4, 9.6, 9.8, 10, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0026] As a preferred technical solution of the present invention, the solid-liquid separation in step (2) yields tin mud and filtrate.

[0027] Preferably, the water washing process includes washing the tin sludge after solid-liquid separation with deionized water to obtain a cleaning solution.

[0028] Preferably, the filtrate and washing solution are subjected to evaporation and crystallization treatment to obtain sodium nitrate product.

[0029] As a preferred embodiment of the present invention, the alkaline solution used in the second alkali treatment includes sodium hydroxide and hydrogen peroxide.

[0030] In this invention, hydrogen peroxide is added during the second alkali treatment to remove organic impurities and further improve the purity of sodium stannate.

[0031] Preferably, the mass fraction of the hydrogen peroxide is 0.1% to 2%, such as 0.1%, 0.5%, 1%, 1.5%, 2%, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0032] Preferably, the molar ratio of sodium hydroxide to tin in the tin sludge during the second alkali treatment is greater than 3:1, such as 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0033] Preferably, the temperature of the second alkali treatment is greater than 85°C, such as 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0034] As a preferred embodiment of the present invention, the evaporation crystallization process yields an evaporation mother liquor; the evaporation mother liquor is then reused in the second alkali treatment.

[0035] As a preferred embodiment of the present invention, sodium stannate crystals are obtained after the evaporation and crystallization process; the sodium stannate crystals are then washed with water and dried to obtain the sodium stannate product.

[0036] Preferably, the number of water washes is at least two, such as 2, 3, 4, 5, or 6 times, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0037] Preferably, the drying temperature is 90~105℃, such as 90℃, 95℃, 100℃, 105℃, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0038] Preferably, the drying time is 2 to 4 hours, such as 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0039] As a preferred technical solution of the present invention, the washing solution after washing with sodium stannate crystallization water is mixed with the solution treated with the second alkali and then subjected to evaporation crystallization treatment.

[0040] As a preferred technical solution of the present invention, the method includes:

[0041] (1) The tin stripping solution is subjected to a first alkali treatment, and after solid-liquid separation, copper oxide mud and alkali treatment solution are obtained;

[0042] The alkaline solution used for the first alkali treatment includes sodium hydroxide; the mass concentration of the alkaline solution is 40%~50%; the content of free sodium hydroxide in the solution after the first alkali treatment is 7.5%~20%; the pH of the solution after the first alkali treatment is 14.2~14.8; the temperature of the first alkali treatment is greater than 90℃; and the time of the first alkali treatment is 4~6 hours.

[0043] The copper oxide sludge obtained in step (1) is cleaned to obtain copper oxide product; the cleaning agent for the cleaning treatment includes sodium hydroxide solution; the mass fraction of the sodium hydroxide solution is 0.5%~2%; the solid-liquid ratio of the copper oxide sludge to the cleaning agent is 1:(2~3);

[0044] (2) The alkaline treatment solution is subjected to neutralization, solid-liquid separation and water washing in sequence to obtain tin mud;

[0045] The neutralizing agent used in the neutralization treatment includes nitric acid; the pH of the solution after neutralization treatment is 9-10; after solid-liquid separation in step (2), tin mud and filtrate are obtained; the water washing treatment includes washing the tin mud after solid-liquid separation with deionized water to obtain a cleaning solution; the filtrate and cleaning solution are subjected to evaporation and crystallization treatment to obtain sodium nitrate product;

[0046] (3) The tin mud is subjected to a second alkali treatment and evaporation crystallization treatment to obtain the sodium stannate;

[0047] The alkaline solution used in the second alkaline treatment includes sodium hydroxide and hydrogen peroxide; the mass fraction of the hydrogen peroxide is 0.1%~2%; the molar ratio of sodium hydroxide to tin in the tin slurry in the second alkaline treatment is greater than 3:1; the temperature of the second alkaline treatment is greater than 85°C.

[0048] The evaporation crystallization process yields an evaporation mother liquor; the evaporation mother liquor is reused in the second alkali treatment; the evaporation crystallization process yields sodium stannate crystals; the sodium stannate crystals are washed with water and dried to obtain the sodium stannate product; the water washing is performed at least twice; the drying temperature is 90~105℃; the drying time is 2~4 hours; the washing solution after washing the sodium stannate crystals is mixed with the solution from the second alkali treatment and then subjected to evaporation crystallization.

[0049] Compared with the prior art, the present invention has at least the following beneficial effects:

[0050] The method of the present invention employs a combination of first alkali treatment, neutralization treatment, water washing treatment, second alkali treatment, and evaporation crystallization treatment, which can simultaneously realize the resource recovery of copper and the direct preparation of sodium stannate; the water washing treatment can remove soluble impurities from tin mud, thereby improving the purity of sodium stannate products. Attached Figure Description

[0051] Figure 1 This is a process flow diagram of a method for directly preparing sodium stannate from a tin stripping solution provided by the present invention. Detailed Implementation

[0052] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0053] Example 1

[0054] This embodiment provides a method for directly preparing sodium stannate from a tin stripping solution, the method comprising:

[0055] (1) Add 50% sodium hydroxide to the tin stripping solution. The free sodium hydroxide content in the solution is 7.5%, the solution pH is 14.2, and perform the first alkali treatment at 90℃ for 4 hours. After solid-liquid separation, copper oxide mud and alkali treatment solution are obtained.

[0056] The copper oxide sludge is cleaned with 0.5% sodium hydroxide at a solid-liquid ratio of 1:2 to obtain the copper oxide product.

[0057] (2) Nitric acid is added to the alkaline treatment solution to adjust the pH to 9. After neutralization, tin mud and filtrate are obtained by solid-liquid separation. The tin mud is washed with deionized water to obtain a cleaning solution. The filtrate and cleaning solution are evaporated and crystallized to obtain sodium nitrate product.

[0058] (3) Sodium hydroxide is added to the tin mud, and a second alkali treatment is carried out at 85°C, and hydrogen peroxide with a mass fraction of 0.1% is slowly added; the molar ratio of sodium hydroxide to tin in the tin mud during the second alkali treatment is 3:1; after evaporation and crystallization treatment, evaporation mother liquor is obtained; the evaporation mother liquor is reused in the second alkali treatment; sodium stannate crystals are obtained after the evaporation and crystallization treatment.

[0059] The sodium stannate crystals are washed twice with water and then dried at 90°C for 2 hours to obtain the sodium stannate product. The washing solution after washing the sodium stannate crystals is mixed with the solution from the second alkali treatment and then subjected to evaporation crystallization.

[0060] Example 2

[0061] This embodiment provides a method for directly preparing sodium stannate from a tin stripping solution, the method comprising:

[0062] (1) Add sodium hydroxide with a mass concentration of 45% to the tin stripping solution. The content of free sodium hydroxide in the solution is 10%, the pH of the solution is 14.5, and perform the first alkali treatment at 100℃ for 5 hours. After solid-liquid separation, copper oxide mud and alkali treatment solution are obtained.

[0063] The copper oxide sludge was cleaned with 1% sodium hydroxide at a solid-liquid ratio of 1:2.5 to obtain the copper oxide product.

[0064] (2) Nitric acid is added to the alkaline treatment solution to adjust the pH to 9.5. After neutralization, the solid and liquid are separated to obtain tin mud and filtrate. The tin mud is washed with deionized water to obtain a cleaning solution. The filtrate and cleaning solution are evaporated and crystallized to obtain sodium nitrate product.

[0065] (3) Sodium hydroxide is added to the tin mud, and a second alkali treatment is carried out at 100°C, and hydrogen peroxide with a mass fraction of 1% is slowly added; the molar ratio of sodium hydroxide to tin in the tin mud during the second alkali treatment is 4:1; after evaporation and crystallization treatment, evaporation mother liquor is obtained; the evaporation mother liquor is reused in the second alkali treatment; sodium stannate crystals are obtained after the evaporation and crystallization treatment.

[0066] The sodium stannate crystals are washed with water three times and then dried at 100°C for 3 hours to obtain the sodium stannate product. The washing solution after washing the sodium stannate crystals is mixed with the solution from the second alkali treatment and then subjected to evaporation crystallization.

[0067] Example 3

[0068] This embodiment provides a method for directly preparing sodium stannate from a tin stripping solution, the method comprising:

[0069] (1) Add sodium hydroxide with a mass concentration of 40% to the tin stripping solution. The content of free sodium hydroxide in the solution is 20%, the pH of the solution is 14.8, and perform the first alkali treatment at 110℃ for 6 hours. After solid-liquid separation, copper oxide mud and alkali treatment solution are obtained.

[0070] The copper oxide sludge was cleaned with 2% sodium hydroxide at a solid-liquid ratio of 1:3 to obtain the copper oxide product.

[0071] (2) Nitric acid is added to the alkaline treatment solution to adjust the pH to 10. After neutralization, tin mud and filtrate are obtained by solid-liquid separation. The tin mud is washed with deionized water to obtain a cleaning solution. The filtrate and cleaning solution are evaporated and crystallized to obtain sodium nitrate product.

[0072] (3) Sodium hydroxide is added to the tin mud, and a second alkali treatment is carried out at 110°C, and hydrogen peroxide with a mass fraction of 2% is slowly added; the molar ratio of sodium hydroxide to tin in the tin mud during the second alkali treatment is 5:1; after evaporation and crystallization treatment, evaporation mother liquor is obtained; the evaporation mother liquor is reused in the second alkali treatment; sodium stannate crystals are obtained after the evaporation and crystallization treatment.

[0073] The sodium stannate crystals were washed with water four times and then dried at 105°C for 4 hours to obtain the sodium stannate product. The washing solution after washing the sodium stannate crystals was mixed with the solution from the second alkali treatment and then subjected to evaporation crystallization.

[0074] Example 4

[0075] This embodiment provides a method for directly preparing sodium stannate from tin stripping solution. The only difference from Embodiment 1 is that after the first alkali treatment in step (1), the free sodium hydroxide content in the solution is 2%. All other steps and condition parameters are the same as in Embodiment 1.

[0076] Example 5

[0077] This embodiment provides a method for directly preparing sodium stannate from tin stripping solution. The only difference from Embodiment 1 is that after the first alkali treatment in step (1), the free sodium hydroxide content in the solution is 30%. All other steps and conditions are the same as in Embodiment 1.

[0078] Example 6

[0079] This embodiment provides a method for directly preparing sodium stannate from tin stripping solution. The only difference from Embodiment 1 is that the molar ratio of sodium hydroxide to tin in tin mud in the second alkali treatment in step (3) is adjusted to 2:1. All other steps and conditions are the same as in Embodiment 1.

[0080] Example 7

[0081] This embodiment provides a method for directly preparing sodium stannate from tin stripping solution. The only difference from Embodiment 1 is that the alkali solution used in the first alkali treatment in step (1) is replaced with ammonia water of equal mass. All other steps and condition parameters are the same as in Embodiment 1.

[0082] Comparative Example 1

[0083] This comparative example provides a method for directly preparing sodium stannate from tin stripping solution. The only difference from Example 1 is that the water washing treatment described in step (2) is not performed. All other steps and conditions are the same as in Example 1.

[0084] Comparative Example 2

[0085] This comparative example provides a method for directly preparing sodium stannate from tin stripping solution. The only difference from Example 1 is that the first alkali treatment in step (1) is not performed. All other steps and conditions are the same as in Example 1.

[0086] Performance testing

[0087] The purity, tin recovery rate, and copper recovery rate of the sodium stannate products prepared in Examples 1-7 and Comparative Examples 1-2 were tested. The free sodium hydroxide content in the solution was determined by the total alkalinity minus the corresponding alkalinity of sodium stannate. The sodium stannate content was calculated after detecting the tin content using inductively coupled plasma spectroscopy (ICP). The test results are shown in Table 1.

[0088] Table 1

[0089]

[0090] The test results show that:

[0091] (1) As can be seen from Examples 1 to 3, the method of the present invention can simultaneously realize the resource recovery of copper and the direct preparation of sodium stannate through a combination of first alkali treatment, neutralization treatment, water washing treatment, second alkali treatment and evaporation crystallization treatment, thereby improving the purity of sodium stannate products and the recovery rate of tin and copper.

[0092] (2) By comparing Example 1 with Examples 4-7, it can be seen that in Examples 4 and 5, the content of free sodium hydroxide in the solution after the first alkali treatment was adjusted, thereby further improving the purity of sodium stannate, tin recovery rate and copper recovery rate; in Example 6, the molar ratio of sodium hydroxide to tin in the tin mud was adjusted in the second alkali treatment, which helped to completely dissolve the tin mud and thus improved the tin recovery rate; in Example 7, the alkali solution used in the first alkali treatment was replaced with ammonia water of equal mass, which resulted in insufficient alkalinity of the solution to dissolve the tin mud, and copper dissolved in the solution in the form of copper ammonia complex; although copper and tin can be separated, copper exists in the form of complex, and copper resource utilization requires additional processing steps, and some copper still remains in the undissolved tin mud. When dissolved later, copper will catalyze the decomposition of hydrogen peroxide, which will reduce the tin leaching rate when the tin mud is dissolved, and the removal of organic matter is incomplete, thus reducing the purity and quality of sodium stannate.

[0093] (3) By comparing Example 1 with Comparative Examples 1-2, it can be seen that Comparative Example 1 does not perform water washing treatment, which cannot remove soluble impurities in tin mud, resulting in a decrease in the purity of sodium stannate product; Comparative Example 2 does not perform first alkali treatment, so tin dissolves while copper does not. Although copper and tin can be separated and copper can be recovered, it will also lead to a decrease in tin leaching rate and incomplete removal of organic matter.

[0094] In summary, this invention provides a method for directly preparing sodium stannate from tin stripping solution. The method employs a combination of a first alkali treatment, neutralization treatment, water washing treatment, a second alkali treatment, and evaporation crystallization treatment, which can simultaneously achieve the resource recovery of copper and the direct preparation of sodium stannate. The water washing treatment can remove soluble impurities from the tin sludge, thereby improving the purity of the sodium stannate product.

[0095] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for directly producing sodium stannate from a tin stripping solution, characterized by, The method comprises: (1) performing first alkali treatment on the tin stripping solution, and obtaining copper oxide sludge and alkali treatment solution after solid-liquid separation; (2) sequentially performing neutralization treatment, solid-liquid separation and water washing treatment on the alkali treatment solution to obtain tin sludge; (3) performing second alkali treatment and evaporation crystallization treatment on the tin sludge to obtain the sodium stannate.

2. The method of claim 1, wherein, The alkali solution used in the first alkali treatment comprises sodium hydroxide; the mass concentration of the alkali solution is 40%-50%; Preferably, the content of free sodium hydroxide in the solution after the first alkali treatment is 7.5%-20%; Preferably, the pH of the solution after the first alkali treatment is 14.2-14.8; Preferably, the temperature of the first alkali treatment is greater than 90℃; Preferably, the time of the first alkali treatment is 4-6h.

3. The method according to claim 1 or 2, characterized in that, The copper oxide sludge obtained in step (1) is subjected to cleaning treatment to obtain a copper oxide product; Preferably, the cleaning agent used in the cleaning treatment comprises a sodium hydroxide solution; the mass fraction of the sodium hydroxide solution is 0.5%-2%; Preferably, the solid-liquid ratio of the copper oxide sludge to the cleaning agent is 1:(2-3).

4. The method according to any one of claims 1 to 3, characterized in that, The neutralizing agent used in the neutralization treatment comprises nitric acid; Preferably, the pH of the solution after the neutralization treatment is 9-10.

5. The method according to any one of claims 1 to 4, characterized in that, The solid-liquid separation in step (2) obtains tin sludge and filtrate; Preferably, the water washing treatment comprises cleaning the tin sludge after the solid-liquid separation with deionized water to obtain a cleaning solution; Preferably, the filtrate and the cleaning solution are subjected to evaporation crystallization treatment to obtain a sodium nitrate product.

6. The method according to any one of claims 1 to 5, characterized in that, The alkali solution used in the second alkali treatment comprises sodium hydroxide and hydrogen peroxide; Preferably, the mass fraction of the hydrogen peroxide is 0.1%-2%; Preferably, the molar ratio of sodium hydroxide to tin in the second alkali treatment is greater than 3:1; Preferably, the temperature of the second alkali treatment is greater than 85℃.

7. The method according to any one of claims 1 to 6, characterized in that, The evaporation crystallization treatment obtains an evaporation mother liquor; the evaporation mother liquor is recycled to the second alkali treatment.

8. The method according to any one of claims 1 to 7, characterized in that, The evaporation crystallization treatment obtains sodium stannate crystals; the sodium stannate crystals are subjected to water washing and drying to obtain a sodium stannate product; Preferably, the water washing is performed at least twice; Preferably, the drying temperature is 90-105℃; Preferably, the drying time is 2-4h.

9. The method according to any one of claims 1 to 8, characterized in that, The washing solution of the sodium stannate crystals after water washing is mixed with the solution of the second alkali treatment, and then subjected to evaporation crystallization treatment.

10. The method according to any one of claims 1 to 9, characterized in that, The method comprises: (1) performing first alkali treatment on the tin stripping solution, and obtaining copper oxide sludge and alkali treatment solution after solid-liquid separation; The alkali solution used in the first alkali treatment comprises sodium hydroxide; the mass concentration of the alkali solution is 40%-50%; the content of free sodium hydroxide in the solution after the first alkali treatment is 7.5%-20%; the pH of the solution after the first alkali treatment is 14.2-14.8; the temperature of the first alkali treatment is greater than 90℃; the time of the first alkali treatment is 4-6h; The copper oxide sludge obtained in step (1) is subjected to cleaning treatment to obtain a copper oxide product; the cleaning agent used in the cleaning treatment comprises a sodium hydroxide solution; the mass fraction of the sodium hydroxide solution is 0.5%-2%; the solid-liquid ratio of the copper oxide sludge to the cleaning agent is 1:(2-3); (2) sequentially performing neutralization treatment, solid-liquid separation and water washing treatment on the alkali treatment solution to obtain tin slurry; The neutralizing agent used in the neutralization treatment comprises nitric acid; the solution after the neutralization treatment has a pH of 9-10; the solid-liquid separation in step (2) obtains tin slurry and filtrate; the water washing treatment comprises cleaning the tin slurry after the solid-liquid separation with deionized water to obtain a cleaning solution; the filtrate and the cleaning solution are subjected to evaporation crystallization treatment to obtain a sodium nitrate product; (3) performing second alkali treatment and evaporation crystallization treatment on the tin slurry to obtain the sodium stannate; The alkali solution used in the second alkali treatment comprises sodium hydroxide and hydrogen peroxide; the mass fraction of the hydrogen peroxide is 0.1%-2%; the molar ratio of sodium hydroxide to tin in the tin slurry in the second alkali treatment is greater than 3:1; the temperature of the second alkali treatment is greater than 85℃; The evaporation crystallization treatment obtains evaporation mother liquor; the evaporation mother liquor is recycled for the second alkali treatment; the evaporation crystallization treatment obtains sodium stannate crystals; the sodium stannate crystals are subjected to water washing and drying to obtain a sodium stannate product; the water washing is performed at least twice; the drying temperature is 90-105℃; the drying time is 2-4h; the washing solution after the water washing of the sodium stannate crystals is mixed with the solution for the second alkali treatment, and then subjected to evaporation crystallization treatment.

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