Method for preparing sodium stannate and co-producing barium stannate by utilizing tin-containing wastewater of beta-thymidine production process

Abstract

The method comprises the following steps: treating tin-containing wastewater generated in a process for producing beta-thymidine through condensation reaction of thymine and tetraacetyl ribose by using a mixed alkali aqueous solution consisting of ammonia water and tetramethylammonium hydroxide, and then settling and separating to obtain colloidal water-containing tin hydroxide; the preparation method comprises the following steps: mixing colloidal water-containing tin hydroxide and solid sodium hydroxide, heating and co-melting to convert the colloidal water-containing tin hydroxide and the solid sodium hydroxide into a sodium stannate-containing mixed material, and sequentially extracting with deionized water and filtering or centrifugally separating to obtain a sodium stannate-containing aqueous solution; the aqueous solution containing sodium stannate is subjected to concentration, cooling crystallization and filtration or centrifugal separation to obtain a sodium stannate wet solid material and an aqueous solution containing sodium stannate, and the sodium stannate wet solid material is subjected to vacuum drying to obtain a finished product sodium stannate meeting quality requirements. And sequentially adding barium chloride into the aqueous solution containing sodium stannate for precipitation, filtering or centrifugal separation, deionized water washing and vacuum drying to obtain a barium stannate product meeting the quality requirement.

Description

Technical Field

[0001] The present invention belongs to the fields of energy conservation, environmental protection and inorganic fine chemicals, and relates to a method for preparing sodium stannate and co-producing barium stannate by using tin-containing wastewater generated in the process of producing β-thymidine by a chemical method. Background Art

[0002] β-Thymidine, also known as 2'-deoxythymidine, deoxythymosin, 2'-deoxythymidine, is a deoxyribonucleoside containing thymine base, and is mainly used as a pharmaceutical intermediate for the synthesis of anti-AIDS drugs such as zidovudine and stavudine and antiviral drugs. The typical chemical synthesis method of β-thymidine is that thymine is protected by silylation and then condensed with tetraacetylribose in turn under the catalysis of Lewis acid to generate triacetyl 5-methyluridine, triacetyl 5-methyluridine is deacetylated to generate 5-methyluridine, 5-methyluridine is dehydrated to generate 2,2'-anhydro-5-methyluridine, 2,2'-anhydro-5-methyluridine is halogenated to generate 2'-halo-2'-deoxy-5-methyluridine, and finally 2'-halo-2'-deoxy-5-methyluridine is reduced and dehalogenated to obtain β-thymidine with high selectivity. Among them, when SnCl4 is used as a catalyst in the condensation reaction, it has a high yield and becomes the most widely used Lewis acid catalyst, but it also causes a large amount of process wastewater containing Sn(IV) to be generated during the production of β-thymidine by this process.

[0003] Sodium stannate is a colorless hexagonal crystal or white powder with a CAS number of 12058-66-1. It is soluble in water but insoluble in alcohol and acetone. When heated to 140 °C, it becomes anhydrous due to the loss of crystal water. It can absorb carbon dioxide in the air and be converted into sodium carbonate and stannic hydroxide. It is mainly used for alkaline tin plating, copper plating and tin-aluminum alloy plating in the electroplating industry, and is also used as a mordant in the dye industry. It also has wide application value in many fields such as glass production, ceramic preparation, metallurgy and the electronic industry. Barium stannate is a white powdery crystal with a CAS number of 12009-18-6. It is slightly soluble in water and easily soluble in hydrochloric acid, and can be used to produce high-dielectric-insulating ceramics.

[0004] There are two typical preparation methods for sodium stannate: one is that metallic tin is melted and then water-quenched to form tin flowers, which are then co-fused with sodium hydroxide and sodium nitrate to generate a mixed material containing sodium stannate. Subsequently, it is successively subjected to water dissolution, purification and impurity removal with sodium sulfide and hydrogen peroxide, suction filtration, evaporation and concentration, centrifugal separation, drying, and pulverization to obtain the sodium stannate product; the other is that after stannic oxide reacts with a sodium hydroxide solution to generate a material containing sodium stannate, it is then subjected to impurity removal, suction filtration, evaporation and concentration, centrifugal separation, drying, and pulverization to obtain the sodium stannate product. There are also two typical preparation methods for barium stannate: one is that after Sn(OH)4 reacts with a NaOH solution to generate an aqueous solution of the Na2Sn(OH)6 complex, it reacts with an aqueous BaCl2 solution under strong stirring under the condition of controlling the pH value of the solution above 11. Then, the material formed by the reaction is separated, and the obtained solid material is thoroughly washed and dried; the other is that sodium stannate dissolved in water reacts with a water-soluble Ba(II) salt such as BaCl2 under strong stirring under alkaline conditions. Then, the material formed by the reaction is separated, and the obtained solid material is thoroughly washed and dried.

[0005] In these methods for preparing sodium stannate, whether it is the method based on metallic tin as the raw material or the method based on stannic oxide as the raw material, they highly rely on scarce natural resources, thus making the production of sodium stannate have a relatively high raw material cost. And in the methods for preparing barium stannate, there is actually a process of generating barium stannate by reacting sodium stannate with a water-soluble Ba(II) salt.

[0006] A method for preparing sodium stannate and co-producing barium stannate by using tin-containing wastewater from the β-thymidine production process according to the present invention belongs to a method for preparing sodium stannate and barium stannate by using industrial Sn(IV)-containing wastewater. One of its purposes is to solve the problems of scientific disposal and high-value utilization of resource recovery of Sn(IV)-containing wastewater generated in the existing chemical method for producing β-thymidine, and the other is to reduce the dependence on scarce natural resources in the existing production of sodium stannate and barium stannate and reduce their production raw material costs and other problems.

[0007] In the research and development process of a method for preparing sodium stannate and co-producing barium stannate from tin-containing wastewater in the β-thymidine production process, a lot of technical information on the preparation and application of β-thymidine, sodium stannate, and barium stannate was accessed. The main ones with certain reference value include: "Study on the Synthesis Process of 2'-Bromo-2'-deoxy-3',5',O-dipropionyl-β-D-ribosylthymidine" (Chinese Journal of Modern Applied Pharmacy, 2004, Vol. 21, No. 3), "Research on the Synthesis of β-Thymidine" (Master's Degree Thesis of China University of Petroleum, 2016), "Method for Synthesizing Deoxythymidine" (CN118930594A, November 12, 2024), "A Method for Synthesizing β-Thymidine" (CN104513287A, April 15, 2015), "Direct Preparation of Sodium Stannate from Tin Concentrate" (Journal of Central South Institute of Mining and Metallurgy, 1987, Vol. 18, No. 4), "Optimization of Sodium Stannate Synthesis Process by Response Surface Methodology" (Yunnan Chemical Industry, 2023, Vol. 50, No. 5), "Research on the Crystallization Process in the Industrial Production of Sodium Stannate" (China Nonferrous Metallurgy, 2017, Vol. 46, No. 4), "Experimental Study on the One-Step Synthesis of Sodium Stannate" (Modern Chemical Industry, 2012, Vol. 32, No. 9), "Barium Stannate Powder and Its Manufacturing Method" (Inorganic Chemicals Industry, 1994, No. 5), "Research Progress on Barium Stannate Nanomaterials" (China Ceramics, 2020, Vol. 56, No. 3), "Superbasic Sodium Stannate as Catalyst for Dehydrogenation, Michael Addition and Transesterification Reactions" (Applied Catalysis, A: General, 2011, Vol. 406, No. 1-2), "Function Mechanism of CO-CO2 Atmosphere on the Formation of Na2SnO3 from SnO2 and Na2CO3 during the Roasting Process" (Powder Technology, 2016, Vol. 301), "Crystallization and Phase Transition Boosted Optical Linear & Nonlinear and Magnetic Properties in Transparent xCu:BaSnO3 NCs / Glass-Ceramic" (Journal of the European Ceramic Society, 2025, Vol. 45, No. 3). Summary of the Invention

[0008] Technical problems to be solved: This application discloses a method for preparing sodium stannate and co-producing barium stannate using tin-containing wastewater from the β-thymidine production process. The technical problems to be solved are to overcome the potential environmental pollution of tin-containing wastewater generated in the production process of β-thymidine by the condensation method of thymine and tetraacetylribose, improve the scientific treatment effect and resource utilization rate of tin-containing wastewater, and reduce the raw material cost in the existing production technologies of sodium stannate and barium stannate. The invention of the method for preparing sodium stannate and co-producing barium stannate using tin-containing wastewater generated in the β-thymidine production process promotes the clean production of β-thymidine, sodium stannate and barium stannate and the greening of the production process, promotes the efficient utilization of resources, and makes the production of β-thymidine, sodium stannate and barium stannate more in line with the requirements of "low emission, low pollution, low consumption, and high safety".

[0009] Technical solutions:

[0010] A method for preparing sodium stannate and co-producing barium stannate using tin-containing wastewater from the β-thymidine production process, taking the tin-containing wastewater generated in the condensation reaction of thymine and tetraacetylribose to produce β-thymidine as one of the basic raw materials. After adding mixed alkali to the tin-containing wastewater to convert Sn(IV) therein into a hydrated Sn(OH)4 colloidal precipitate, the separated hydrated Sn(OH)4 colloidal precipitate is mixed with solid NaOH and then co-melted to obtain a mixed material containing sodium stannate. Then, through water extraction and filtration or centrifugal separation in sequence, an aqueous solution containing sodium stannate is obtained. Finally, the aqueous solution containing sodium stannate is concentrated, cooled and crystallized, and filtered or centrifugally separated to obtain wet sodium stannate material and a filtrate or centrifugate containing sodium stannate; the obtained wet sodium stannate material is washed with an aqueous NaOH solution and then vacuum dried to obtain a finished sodium stannate meeting the quality requirements, and the filtrate or centrifugate containing sodium stannate is added with a solution formed by dissolving Ba(II) salt in water, and then filtered or centrifugally separated, washed, and vacuum dried in sequence to obtain a finished barium stannate meeting the quality requirements.

[0011] Preferably, the mixed alkali is composed of ammonia water and tetramethylammonium hydroxide according to m(ammonia water):m(tetramethylammonium hydroxide)=1.0-10:0.01-5.0.

[0012] Preferably, the material ratio of the hydrated Sn(OH)4 colloidal precipitate to solid NaOH during the co-melting is m(Sn(OH)4 colloidal precipitate):m(NaOH)=0.1-5.0:0.01-5.0.

[0013] Preferably, the temperature during the co-melting of the hydrated Sn(OH), colloidal precipitate and solid NaOH is 100-600°C, and the co-melting time is 0.5-5.0 hours.

[0014] Preferably, the temperature for extracting the mixed material containing sodium stannate formed by co-melting the water-containing Sn(OH)4 colloidal precipitate and solid NaOH with water is 50 - 100 °C.

[0015] Preferably, the method for preparing sodium stannate and co-producing barium stannate from tin-containing wastewater in the process of producing β-thymidine comprises the following specific steps:

[0016] First step: An aqueous solution of a mixed base composed of m(ammonia water):m(tetramethylammonium hydroxide) = 1.0 - 10:0.01 - 5.0 is added to the tin-containing wastewater under stirring.

[0017] Second step: After the material added with the mixed base is allowed to stand and age for 0.5 - 5.0 hours, the upper aqueous phase is separated to obtain a water-containing Sn(OH)4 colloidal precipitate.

[0018] Third step: The water-containing Sn(OH)4 colloidal precipitate is transferred to a melting kettle, and solid NaOH is added. The mixture is co-melted at 100 - 600 °C for 0.5 - 5.0 hours under stirring to obtain a mixed material containing sodium stannate.

[0019] Fourth step: Deionized water is added to the mixed material containing sodium stannate at a ratio of m(Sn(OH)4 colloidal precipitate):m(water) = 0.5:0.1 - 10, and the mixture is stirred and extracted at 50 - 100 °C for 0.5 - 5.0 hours.

[0020] Fifth step: The material obtained in the fourth step is filtered or centrifuged, and the obtained filtrate or centrifugate is transferred to a concentration kettle and concentrated under the conditions of a vacuum degree of 0.05 - 0.1 MPa and a temperature of 60 - 100 °C.

[0021] Sixth step: The concentrated liquid obtained in the fifth step is transferred to a crystallization tank for cooling crystallization, and then the crystallized material is filtered or centrifuged to obtain wet sodium stannate material and a filtrate or centrifugate containing sodium stannate respectively.

[0022] Seventh step: The wet sodium stannate material obtained in the sixth step is washed with an aqueous NaOH solution with a mass percentage of 3 - 30%, and then dried and dehydrated under the conditions of a vacuum degree of 0.05 - 0.1 MPa and a temperature of 60 - 100 °C to obtain finished sodium stannate meeting the quality requirements.

[0023] Eighth step: Barium stannate is prepared from the filtrate or centrifugate containing sodium stannate obtained in the sixth step.

[0024] Preferably, the specific steps for preparing barium stannate from the filtrate or centrifugate containing sodium stannate are as follows: while stirring, slowly add an aqueous solution of Ba(II) salt with a mass percentage of 5-30% to the filtrate or centrifugate containing sodium stannate until no white precipitate is formed during the addition; filter or centrifuge the mixed material obtained after adding the Ba(II) salt aqueous solution, and wash the obtained solid material with deionized water to obtain a wet material containing barium stannate; the wet material containing barium stannate is dried and dehydrated under the conditions of a vacuum degree of 0.05-0.1 MPa and a temperature of 60-100 °C to obtain a finished barium stannate meeting the quality requirements.

[0025] Beneficial effects:

[0026] 1. Using the tin-containing wastewater generated in the process of producing β-thymidine by the condensation reaction of thymine and tetraacetylribose as one of the basic raw materials to prepare sodium stannate and co-produce barium stannate can avoid the potential environmental harm of this tin-containing wastewater and improve the effective utilization rate of resources.

[0027] 2. Using the tin-containing wastewater generated in the process of producing β-thymidine by the condensation reaction of thymine and tetraacetylribose as one of the basic raw materials to prepare sodium stannate and co-produce barium stannate can reduce the dependence on scarce resources when producing sodium stannate and barium stannate.

[0028] 3. Using the tin-containing wastewater generated in the process of producing β-thymidine by chemical method as one of the basic raw materials to prepare sodium stannate and co-produce barium stannate is conducive to promoting the clean production of β-thymidine, sodium stannate and barium stannate and the greening of the production process. Description of the drawings

[0029] Figure 1 is the XRD pattern of the sodium stannate product;

[0030] Figure 2 is the XRD pattern of the barium stannate product. Detailed implementation manners

[0031] The following examples can enable those skilled in the art to understand the present invention more comprehensively, but do not limit the present invention in any way.

[0032] Example 1

[0033] A method for preparing sodium stannate and co-producing barium stannate by using tin-containing wastewater in the process of producing β-thymidine includes the following steps:

[0034] The first step: while stirring, add an aqueous solution of a mixed base composed of m(ammonia water):m(tetramethylammonium hydroxide)=1.0:0.1 to the tin-containing wastewater;

[0035] The second step: after standing and aging the material added with the mixed base for 5.0 hours, then separate the upper aqueous phase to obtain a colloidal precipitate of Sn(OH)4 containing water;

[0036] Step 3: Transfer the aqueous Sn(OH)4 colloidal precipitate to a melting kettle, add solid NaOH according to m(Sn(OH)4 colloidal precipitate):m(NaOH) = 0.5:1.0, and co-melt at 200 °C for 5.0 hours under stirring to obtain a mixed material containing sodium stannate;

[0037] Step 4: Add deionized water to the mixed material containing sodium stannate according to m(Sn(OH)4 colloidal precipitate):m(water) = 0.5:1.0, and stir and extract at 50 °C for 2.0 hours;

[0038] Step 5: Filter or centrifuge the material obtained in Step 4, and transfer the obtained filtrate or centrifugate to a concentration kettle to concentrate under the conditions of a vacuum degree of 0.5 MPa and a temperature of 80 °C;

[0039] Step 6: Transfer the concentrated solution obtained in Step 5 to a crystallization tank for cooling crystallization, then filter or centrifuge the crystallized material to obtain wet sodium stannate material and a filtrate or centrifugate containing sodium stannate respectively;

[0040] Step 7: The wet sodium stannate material obtained in Step 6 is washed with an aqueous NaOH solution with a mass percentage of 5%, and then dried and dehydrated under the conditions of a vacuum degree of 0.5 MPa and a temperature of 60 °C to obtain finished sodium stannate meeting the quality requirements;

[0041] Step 8: Prepare barium stannate from the filtrate or centrifugate containing sodium stannate obtained in Step 6. The process is as follows: Slowly add a solution formed by dissolving a Ba(II) salt with a mass percentage of 5% in water to the filtrate or centrifugate containing sodium stannate obtained under stirring until no white precipitate is formed when added; Filter or centrifuge the obtained mixed material, wash the obtained solid material with deionized water to obtain a wet material containing barium stannate; The wet material containing barium stannate is dried and dehydrated under the conditions of a vacuum degree of 0.5 MPa and a temperature of 80 °C to obtain finished barium stannate meeting the quality requirements.

[0042] Example 2

[0043] A method for preparing sodium stannate and co-producing barium stannate from tin-containing wastewater in the process of producing β-thymidine, comprising the following steps:

[0044] Step 1: Add an aqueous solution of a mixed base composed of m(ammonia water):m(tetramethylammonium hydroxide) = 5.0:0.1 to the tin-containing wastewater under stirring;

[0045] Step 2: After standing and aging the material added with the mixed base for 3.0 hours, separate the upper aqueous phase to obtain an aqueous Sn(OH)4 colloidal precipitate;

[0046] Step 3: Transfer the aqueous Sn(OH)4 colloidal precipitate to a melting kettle, add solid NaOH according to m(Sn(OH)4 colloidal precipitate) : m(NaOH) = 0.5 : 2.0, and co-melt at 400 °C for 3.0 hours under stirring to obtain a mixed material containing sodium stannate;

[0047] Step 4: Add deionized water to the mixed material containing sodium stannate according to m(Sn(OH)4 colloidal precipitate) : m(water) = 0.5 : 2.0, and stir and extract at 80 °C for 2.0 hours;

[0048] Step 5: Filter or centrifuge the material obtained in Step 4, and transfer the obtained filtrate or centrifugate to a concentration kettle to concentrate under the conditions of a vacuum degree of 0.6 MPa and 90 °C;

[0049] Step 6: Transfer the concentrated liquid obtained in Step 5 to a crystallization tank for cooling crystallization, then filter or centrifuge the crystallized material to obtain wet sodium stannate material and filtrate or centrifugate containing sodium stannate respectively;

[0050] Step 7: After the wet sodium stannate material obtained in Step 6 is washed with a 10% NaOH aqueous solution by mass percentage, it is then dried and dehydrated under the conditions of a vacuum degree of 0.5 MPa and 100 °C to obtain finished sodium stannate meeting the quality requirements;

[0051] Step 8: Prepare barium stannate from the filtrate or centrifugate containing sodium stannate obtained in Step 6, and the process is as follows: Slowly add a solution formed by dissolving a 10% Ba(II) salt in water to the obtained filtrate or centrifugate containing sodium stannate under stirring until no white precipitate is formed when adding; Filter or centrifuge the obtained mixed material, wash the obtained solid material with deionized water to obtain a wet material containing barium stannate; The wet material containing barium stannate is dried and dehydrated under the conditions of a vacuum degree of 0.6 MPa and 80 °C to obtain finished barium stannate meeting the quality requirements.

[0052] Example 3

[0053] A method for preparing sodium stannate and co-producing barium stannate from tin-containing wastewater in the process of producing β-thymidine, comprising the following steps:

[0054] Step 1: Add an aqueous solution of a mixed base composed of m(ammonia water) : m(tetramethylammonium hydroxide) = 10.0 : 0.1 to the tin-containing wastewater under stirring;

[0055] Step 2: After standing the material added with the mixed base for 1.0 hour, then separate the upper aqueous phase to obtain an aqueous Sn(OH)4 colloidal precipitate;

[0056] Step 3: Transfer the aqueous Sn(OH)4 colloidal precipitate to a melting kettle, and add solid NaOH at a ratio of m(Sn(OH)4 colloidal precipitate) : m(NaOH) = 0.5 : 5.0. Co-melt at 600 °C for 2.0 hours under stirring to obtain a mixed material containing sodium stannate;

[0057] Step 4: Add deionized water to the mixed material containing sodium stannate at a ratio of m(Sn(OH)4 colloidal precipitate) : m(water) = 0.5 : 10.0, and stir and extract at 100 °C for 2.0 hours;

[0058] Step 5: Filter or centrifuge the material obtained in Step 4, and transfer the obtained filtrate or centrifugate to a concentration kettle to concentrate under the conditions of a vacuum degree of 0.5 MPa and a temperature of 80 °C;

[0059] Step 6: Transfer the concentrated solution obtained in Step 5 to a crystallization tank for cooling crystallization, then filter or centrifuge the crystallized material to obtain wet sodium stannate material and a filtrate or centrifugate containing sodium stannate respectively;

[0060] Step 7: The wet sodium stannate material obtained in Step 6 is washed with an aqueous NaOH solution with a mass percentage of 5%, and then dried and dehydrated under the conditions of a vacuum degree of 0.5 MPa and a temperature of 60 °C to obtain finished sodium stannate meeting the quality requirements;

[0061] Step 8: Prepare barium stannate from the filtrate or centrifugate containing sodium stannate obtained in Step 6. The process is as follows: Slowly add a solution formed by dissolving a Ba(II) salt with a mass percentage of 5% in water to the obtained filtrate or centrifugate containing sodium stannate under stirring until no white precipitate is formed when added; Filter or centrifuge the obtained mixed material, wash the obtained solid material with deionized water to obtain a wet material containing barium stannate; The wet material containing barium stannate is dried and dehydrated under the conditions of a vacuum degree of 0.5 MPa and a temperature of 80 °C to obtain finished barium stannate meeting the quality requirements.

Claims

1. A method for preparing sodium stannate and co-producing barium stannate from tin-containing wastewater in the process of producing β-thymidine, which is characterized in that: Using the tin-containing wastewater generated in the process of producing β-thymidine by the condensation reaction of thymine and tetraacetyl ribose as one of the basic raw materials, after adding a mixed alkali to the tin-containing wastewater to convert Sn(IV) therein into a hydrated Sn(OH)4 colloidal precipitate, the separated hydrated Sn(OH)4 colloidal precipitate is then mixed with solid NaOH and subjected to co-melting to form a mixed material containing sodium stannate. Then, through water extraction and filtration or centrifugal separation in sequence, an aqueous solution containing sodium stannate is obtained. Finally, the aqueous solution containing sodium stannate is concentrated, cooled and crystallized, and filtered or centrifugally separated to obtain a wet sodium stannate material and a filtrate or centrifugate containing sodium stannate; the obtained wet sodium stannate material is washed with an aqueous NaOH solution and then vacuum dried to obtain a finished sodium stannate meeting the quality requirements, and the filtrate or centrifugate containing sodium stannate is added with a solution formed by dissolving a Ba(II) salt in water, and then filtered or centrifugally separated, washed, and vacuum dried in sequence to obtain a finished barium stannate meeting the quality requirements.

2. A method for preparing sodium stannate and co-producing barium stannate from tin-containing wastewater in the process of producing β-thymidine according to claim 1, characterized in that, The mixed alkali used to convert Sn(IV) in the tin-containing wastewater into a hydrated Sn(OH)4 colloidal precipitate is composed of ammonia water and tetramethylammonium hydroxide in a mass ratio of m(ammonia water):m(tetramethylammonium hydroxide) = 1.0 - 10:0.01 - 5.

0.

3. A method for preparing sodium stannate and co-producing barium stannate from tin-containing wastewater in the process of producing β-thymidine according to claim 1, characterized in that: The material ratio of the hydrated Sn(OH)4 colloidal precipitate to solid NaOH during co-melting is m(Sn(OH)4 colloidal precipitate):m(NaOH) = 0.1 - 5.0:0.01 - 5.

0.

4. A method for preparing sodium stannate and co-producing barium stannate from tin-containing wastewater in the process of producing β-thymidine according to claim 1, characterized in that: When the hydrated Sn(OH)4 colloidal precipitate is mixed with solid NaOH and subjected to co-melting, the temperature is 100 - 600 °C, and the co-melting time is 0.5 - 5.0 hours.

5. A method for preparing sodium stannate and co-producing barium stannate from tin-containing wastewater in the process of producing β-thymidine according to claim 1, characterized in that: The temperature for extracting the mixed material containing sodium stannate formed by co-melting the hydrated Sn(OH)4 colloidal precipitate with solid NaOH with water is 50 - 100 °C.

6. A method for preparing sodium stannate and co-producing barium stannate from tin-containing wastewater in the process of producing β-thymidine according to claim 1, characterized in that The specific steps for preparing sodium stannate and co-producing barium stannate are as follows: First step: The aqueous solution of the mixed alkali with a mass ratio of m(ammonia water):m(tetramethylammonium hydroxide) = 1.0 - 10:0.01 - 5.0 is added to the tin-containing wastewater under stirring. Second step: After the material added with the mixed alkali is allowed to stand and age for 0.5 - 5.0 hours, the upper aqueous phase is separated to obtain a hydrated Sn(OH)4 colloidal precipitate. Third step: The hydrated Sn(OH)4 colloidal precipitate is transferred to a melting kettle, solid NaOH is added, and co-melting is carried out at 100 - 600 °C for 0.5 - 5.0 hours under stirring to obtain a mixed material containing sodium stannate. Fourth step: Deionized water is added to the mixed material containing sodium stannate, and stirring extraction is carried out at 50 - 100 °C for 0.5 - 5.0 hours. Fifth step: The material obtained in the fourth step is filtered or centrifugally separated, and the obtained filtrate or centrifugate is transferred to a concentration kettle and concentrated under the conditions of a vacuum degree of 0.05 - 0.1 MPa and a temperature of 60 - 100 °C. Sixth step: The concentrated solution obtained in the fifth step is transferred to a crystallization tank for cooling crystallization, and then the crystallized material is filtered or centrifugally separated to obtain a wet sodium stannate material and a filtrate or centrifugate containing sodium stannate respectively. Step 7: The sodium stannate wet material obtained in the sixth step is washed with an aqueous NaOH solution with a mass percentage of 3-30%, and then dried and dehydrated under the conditions of a vacuum degree of 0.05-0.1 MPa and a temperature of 60-100 °C to obtain the finished sodium stannate that meets the quality requirements; Step 8: Barium stannate is prepared from the filtrate or centrifugate containing sodium stannate obtained in the sixth step.

7. Preparation of barium stannate from the filtrate or centrifugate containing sodium stannate obtained in the sixth step according to claim 6, characterized in that The specific steps for preparing barium stannate are as follows: A solution formed by dissolving a Ba(II) salt with a mass percentage of 5-30% in water is slowly added to the filtrate or centrifugate containing sodium stannate obtained under stirring until no white precipitate is formed during the addition; The obtained mixed material is filtered or centrifuged, and the obtained solid material is washed with deionized water to obtain a wet material containing barium stannate; The wet material containing barium stannate is dried and dehydrated under the conditions of a vacuum degree of 0.05-0.1 MPa and a temperature of 60-100 °C to obtain the finished barium stannate that meets the quality requirements.

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