Method for preparing sodium stannate by ultrasonic strengthening oxidation of tin sheet at low temperature

Abstract

The present application relates to a kind of ultrasonic reinforced sodium stannate preparation method of tin oxide sheet low temperature, belong to sodium stannate preparation technical field.The present application will high-purity tin sheet be added to sodium hydroxide solution, under the condition of ultrasonic wave, control sodium hydroxide solution temperature is 20~30 ℃, slowly add hydrogen peroxide to 20~30% of preset total addition amount after continuing ultrasonic reinforced oxidation reaction 7~10min;Again, slowly add hydrogen peroxide after multiple times, continue ultrasonic reinforced oxidation reaction, the addition amount of hydrogen peroxide is 10~15% of preset total addition amount each time, ultrasonic reinforced oxidation reaction 4~8min after each hydrogen peroxide is added;Hydrogen peroxide is completely added according to preset total addition amount, continue ultrasonic reinforced oxidation reaction until tin sheet completely dissolves and obtains sodium stannate solution;Sodium stannate solution is filtered, concentrated, separated, washed, dried in turn and obtains sodium stannate product.The present application strictly controls oxidation reaction temperature to 20~30 ℃, reduces hydrogen peroxide volatilization, uses ultrasonic to reinforce hydrogen peroxide oxidation effect, improves tin dissolution effect.

Description

Technical Field

[0001] This invention relates to a method for preparing sodium stannate at low temperature using ultrasonically enhanced tin oxide sheets, belonging to the field of sodium stannate preparation technology. Background Technology

[0002] Sodium stannate is an important chemical raw material, playing a vital role in electroplating, textiles, corrosion prevention, and organic synthesis catalysts. The main production methods for sodium stannate include the detinning method, the alkali fusion method, and the alkali hydrolysis method. The detinning method is primarily used to recover secondary tin resources such as tinplate and tin plating slag. However, it suffers from problems such as low product purity, large wastewater volume, and unstable sources of tin-containing waste, which are detrimental to stable industrial production. The alkali fusion method involves using cassiterite concentrate as raw material, reacting it with sodium oxyoxide at high temperatures to produce a molten sodium stannate. After cooling, leaching, impurity removal, filtration, and crystallization, the sodium stannate product is obtained. However, this method is subject to problems such as strong corrosion to equipment, high cost, and complex process.

[0003] Alkaline hydrolysis is one of the most widely used and technologically mature methods in China. Its principle involves using refined tin (zero-valent tin) as raw material. The refined tin can be small-sized tin flowers or large-sized tin sheets. In a solution of concentrated sodium hydroxide and an oxidant, redox reactions and hydrothermal reactions occur, converting it into sodium stannate. Patent CN101544397 reports a method for producing sodium stannate using tin as the oxidant. However, this process requires maintaining a high-temperature reaction (300℃-600℃), resulting in the generation of harmful ammonia gas, high energy consumption, serious environmental pollution, and operational safety hazards. Taninouchi et al. compared the effects of 13 oxidants on tin conversion in alkaline solutions, finding that iodate ions had the best effect. However, how to separate tin from iodate ions is one of the issues to be considered in subsequent processing. At this point, oxidants that do not introduce impurity ions, such as oxygen and hydrogen peroxide, are attracting more attention. Because oxygen has limited oxidizing power, high-pressure, high-temperature oxygen pressure treatment is required to achieve satisfactory results. However, the oxygen pressure method still suffers from problems such as unsafe operation, high cost, and demanding equipment requirements. Hydrogen peroxide, on the other hand, has become the primary oxidant used in sodium stannate production due to its high oxidizing power and relatively environmentally friendly properties.

[0004] Existing patent CN201210313074.1 provides a method for preparing sodium stannate using tin flecks, hydrogen peroxide, and sodium hydroxide as raw materials. The reaction is carried out at 60–100°C for 1–6 hours, followed by filtration, concentration of the filtrate under reduced pressure, filtration again, and drying of the filter cake. The yield of sodium stannate reaches up to 99.5%. This invention features a simple preparation process, does not produce harmful gases such as ammonia, does not use high temperature or high pressure, and is energy-saving and environmentally friendly, making it suitable for industrial production. Patent CN201911190579.1 discloses a method for preparing sodium stannate with low free alkali and low aqueous solution turbidity. The preparation steps involve reacting metallic tin flecks with sodium hydroxide solution and hydrogen peroxide at 75–85°C for 3.5–4.5 hours, followed by filtration to obtain a sodium stannate solution as filtrate. However, hydrogen peroxide is relatively stable below 30°C, and only begins to decompose into water and oxygen above 30°C. The amount of oxygen produced by the decomposition of 30% hydrogen peroxide at different temperatures was tested. The oxygen volumes measured at 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, and 90℃ were 0, 4.9, 10, 20, 49, 89, and 125 (mL), respectively. This indicates that hydrogen peroxide becomes unstable with increasing temperature, and the decomposition rate accelerates. Tin itself has a high density and tends to settle at the bottom of the solution in the reaction system. Furthermore, larger tin sheets are significantly more difficult to dissolve than smaller tin flowers. During high-temperature reactions, a large amount of hydrogen peroxide at the higher liquid level is converted into water and oxygen, which then escapes into the air. This reduces the oxidizing power of the solution, leading to poor tin sheet dissolution, long dissolution time, low hydrogen peroxide utilization, and high hydrogen peroxide consumption. However, at low temperatures, the kinetic energy of the reactants decreases, the average velocity of molecules slows down, and the collision frequency and energy between reactant molecules decrease, resulting in a slower reaction rate and poor tin sheet dissolution. Therefore, how to achieve rapid oxidation at low temperatures, improve tin oxidation efficiency, reduce oxidant consumption, and accelerate tin dissolution is a key issue that urgently needs to be addressed. Summary of the Invention

[0005] To address the problems of low dissolution efficiency in existing sodium stannate preparation methods, this invention proposes a method for the low-temperature preparation of sodium stannate from tin oxide sheets using ultrasonic enhancement. This invention strictly controls the oxidation reaction temperature to 20–30°C, utilizes ultrasonic cavitation to promote the generation of more potent oxidizing free radicals (·OH) from hydrogen peroxide, and enhances the diffusion of hydrogen peroxide and free radicals in the solution using ultrasonically generated microjets and shock waves (mechanical action). By optimizing the method of adding hydrogen peroxide, the effective utilization of hydrogen peroxide is improved, the tin dissolution effect is enhanced, and the amount of hydrogen peroxide used is reduced, while avoiding problems such as the easy decomposition of hydrogen peroxide at high temperatures and high energy consumption during heating.

[0006] A method for preparing sodium stannate at low temperature using ultrasonically enhanced tin oxide sheets, the specific steps of which are as follows:

[0007] (1) Add high-purity tin sheet to sodium hydroxide solution. Under ultrasonic conditions, control the temperature of sodium hydroxide solution to 20-30℃, slowly add hydrogen peroxide to 20-30% of the preset total addition amount, and continue ultrasonic enhancement oxidation reaction for 7-10 minutes.

[0008] (2) Under the conditions of ultrasound and solution system temperature of 20-30℃, hydrogen peroxide is slowly added in multiple batches and then the ultrasonic strengthening oxidation reaction is continued. The amount of hydrogen peroxide added each time is 10-15% of the preset total amount. The ultrasonic strengthening oxidation reaction is carried out for 4-8 minutes after each addition of hydrogen peroxide. After the hydrogen peroxide is completely added according to the preset total amount, the ultrasonic strengthening oxidation reaction is continued until the tin sheet is completely dissolved to obtain sodium stannate solution.

[0009] (3) The sodium stannate solution is filtered, concentrated, separated, washed and dried to obtain the sodium stannate product.

[0010] In step (1), the concentration of sodium hydroxide solution is 3-6 mol / L, and the solid-liquid ratio of high-purity tin sheet to sodium hydroxide solution is 1:4-8 g:mL.

[0011] The hydrogen peroxide has a mass concentration of 15-30%, and the preset total amount of hydrogen peroxide added is 1.2-2 times the molar amount of high-purity tin sheet.

[0012] The ultrasonic power is 180–300W and the frequency is 20–40kHz.

[0013] The hydrogen peroxide addition rate in step (1) is 2-4 mL / min.

[0014] The hydrogen peroxide addition rate in step (2) is 1-4 mL / min.

[0015] The principle of this invention for the low-temperature preparation of sodium stannate from ultrasonically enhanced tin oxide sheets is as follows: Under low-temperature conditions (20-30°C), while reducing hydrogen peroxide volatilization, the ultrasonic enhancement promotes the generation of free radicals with stronger oxidizing properties from hydrogen peroxide, thereby improving the oxidation efficiency of hydrogen peroxide and achieving enhanced tin dissolution at low temperatures (e.g., Figure 1 The micro-jets generated by ultrasound scour and damage the surface of the tin sheet, thinning it and creating numerous holes and erosion cracks on its surface (e.g., Figure 2 and Figure 3 This increases the specific surface area of ​​the tin sheet, promoting contact between the tin sheet and sodium hydroxide and the oxidant, thereby improving the dissolution effect of tin. Figure 2 , 3 As shown in Figure 4.

[0016] The beneficial effects of this invention are:

[0017] (1) This invention utilizes ultrasound to promote the generation of more oxidizing hydroxyl radicals in hydrogen peroxide at a temperature of 20-30°C. Combined with optimizing the addition method of hydrogen peroxide, it effectively enhances the oxidation potential of the solution, strengthens the oxidation of zero-valent tin to tetravalent tin, and improves the utilization rate of hydrogen peroxide.

[0018] (2) This invention achieves a high-efficiency oxidation reaction at low temperature (temperature is 20-30℃), and the tin dissolution rate can reach more than 99%, realizing the low-energy-consumption and high-efficiency conversion of tin.

[0019] (3) The present invention significantly improves the utilization rate of hydrogen peroxide, reduces the amount of hydrogen peroxide used, and significantly shortens the reaction time. Attached Figure Description

[0020] Figure 1 The solubility of tin under ultrasonic enhancement and conventional (without ultrasonication) conditions at different temperatures;

[0021] Figure 2 Scanning electron microscope (SEM) images of the microstructure of tin sheet raw material, the remaining tin sheet after conventional (without ultrasonic treatment at 20℃) treatment for 60 min, and the remaining tin sheet after ultrasonic strengthening treatment at 20℃ for 10 min.

[0022] Figure 3 The image shows the surface microstructure of the remaining tin sheet after conventional treatment (without ultrasonication at 20°C) for 60 minutes.

[0023] Figure 4 The image shows the surface microstructure of the remaining tin sheet after ultrasonic strengthening treatment at 20℃ for 10 min, as captured by scanning electron microscopy (SEM). Detailed Implementation

[0024] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the content described.

[0025] Example 1: A method for preparing sodium stannate at low temperature using ultrasonically enhanced tin oxide sheets, the specific steps of which are as follows:

[0026] (1) Add high-purity tin sheet to a sodium hydroxide solution with a concentration of 4 mol / L. Under ultrasonic conditions (ultrasonic power of 240W, frequency of 24kHz), control the temperature of the sodium hydroxide solution at 20℃, and slowly add hydrogen peroxide at a rate of 3 mL / min until the preset total addition amount is 25%, and continue ultrasonic enhancement oxidation reaction for 10 min. The mass concentration of the hydrogen peroxide is 30%, and the preset total addition amount of hydrogen peroxide is 1.5 times the molar amount of high-purity tin sheet. The solid-liquid ratio of high-purity tin sheet to sodium hydroxide solution is 1:6 g:mL.

[0027] (2) Under ultrasonic conditions (ultrasonic power of 240W, frequency of 24kHz) and solution temperature of 20℃, hydrogen peroxide was slowly added in portions (each time at a rate of 2mL / min), and the ultrasonic-enhanced oxidation reaction was continued for 7 minutes. The amount of hydrogen peroxide added each time was 15% of the preset total amount, and the ultrasonic-enhanced oxidation reaction was continued for 7 minutes after each addition of hydrogen peroxide. After the hydrogen peroxide was completely added according to the preset total amount, the ultrasonic-enhanced oxidation reaction was continued until the tin sheet was completely dissolved to obtain a sodium stannate solution. The total time of the hydrogen peroxide oxidation reaction in this embodiment was 60 minutes.

[0028] (3) The sodium stannate solution is successively filtered to remove impurities, concentrated and crystallized under reduced pressure, separated by centrifugation, washed and dried to obtain sodium stannate product;

[0029] In this embodiment, the total time of hydrogen peroxide oxidation reaction at 20°C is 60 minutes, and the tin sheet dissolution rate reaches 100%.

[0030] Comparative Example 1: The difference between this comparative example and Example 1 is that: no ultrasound was introduced, and the entire reaction time was 100 min; the tin sheet dissolution rate was only 72.3%, while in Example 1, the tin dissolution rate was increased by 27.7% compared to this comparative example; Figure 2-4 As shown, the ultrasonic cavitation effect promotes the generation of free radicals (·OH) with stronger oxidizing properties from hydrogen peroxide, and the ultrasonic mechanical action generates a strong impact on the tin sheet, which breaks and perforates the tin sheet, increases the reaction contact surface, and promotes the reaction. Under the same reaction conditions, the tin sheet after ultrasonic treatment becomes significantly thinner and has many cracks and holes on its surface, while the tin sheet after conventional treatment is still thicker and has a denser surface.

[0031] Comparative Example 2: The only difference between this comparative example and Example 1 is that hydrogen peroxide was added to the solution all at once, and the tin oxide sheet was ultrasonically strengthened for 80 minutes.

[0032] In this comparative example, the tin dissolution rate was 79.3%. In Example 1, the tin dissolution rate was increased by 20.7% by optimizing the addition method of hydrogen peroxide.

[0033] Comparative Example 3: A method for preparing sodium stannate at low temperature from tin oxide sheets, the specific steps of which are as follows:

[0034] High-purity tin sheets were added to a 4 mol / L sodium hydroxide solution. Under ultrasonic conditions (ultrasonic power 240 W, frequency 24 kHz), the sodium hydroxide solution temperature was controlled at 20 °C. Hydrogen peroxide was slowly added at a rate of 3 mL / min, and the ultrasonic-enhanced oxidation reaction was continued for 80 min. The mass concentration of the hydrogen peroxide was 30%, and the preset total amount of hydrogen peroxide added was 1.5 times the molar amount of the high-purity tin sheets. The solid-liquid ratio of the high-purity tin sheets to the sodium hydroxide solution was 1:6 (g:mL).

[0035] The tin dissolution rate in this comparative example was 82.9%, while in Example 1, the tin dissolution rate was increased by 17.1% by optimizing the addition method of hydrogen peroxide.

[0036] Comparative Example 4: The difference between this comparative example and Example 1 is that: no ultrasound is introduced, and hydrogen peroxide is slowly added at a rate of 2 mL / min at a temperature of 60°C until the tin sheet is completely dissolved.

[0037] The total time for the hydrogen peroxide oxidation reaction in this comparative example reached 130 min, and the total amount of hydrogen peroxide consumed was 2.21 times that in Example 1. Therefore, Example 1 can significantly shorten the time and reduce the amount of hydrogen peroxide used at low temperature (20°C).

[0038] Example 2: A method for preparing sodium stannate at low temperature using ultrasonically enhanced tin oxide sheets, the specific steps of which are as follows:

[0039] (1) Add high-purity tin sheet to a sodium hydroxide solution with a concentration of 3 mol / L. Under ultrasonic conditions (ultrasonic power of 200W, frequency of 20kHz), control the temperature of the sodium hydroxide solution at 25℃, and slowly add hydrogen peroxide at a rate of 3 mL / min until the preset total addition amount is 20%, and continue ultrasonic enhancement oxidation reaction for 10 min. The mass concentration of the hydrogen peroxide is 15%, and the preset total addition amount of hydrogen peroxide is twice the molar amount of the high-purity tin sheet. The solid-liquid ratio of high-purity tin sheet to sodium hydroxide solution is 1:8 g:mL.

[0040] (2) Under ultrasonic conditions (ultrasonic power of 200W, frequency of 20kHz) and solution temperature of 25℃, hydrogen peroxide was slowly added in portions (each time at a rate of 1mL / min), and the ultrasonic-enhanced oxidation reaction was continued for 5 minutes. The amount of hydrogen peroxide added each time was 10% of the preset total amount, and the ultrasonic-enhanced oxidation reaction was continued for 5 minutes after each addition of hydrogen peroxide. After the hydrogen peroxide was completely added according to the preset total amount, the ultrasonic-enhanced oxidation reaction was continued until the tin sheet was completely dissolved to obtain a sodium stannate solution. In this embodiment, the total time of hydrogen peroxide oxidation reaction was 80 minutes, and the total reaction time was 95 minutes.

[0041] (3) The sodium stannate solution was successively filtered to remove impurities, concentrated and crystallized under reduced pressure, centrifuged, washed and dried to obtain the sodium stannate product; in this example, the tin sheet dissolution rate reached 100% under the conditions of hydrogen peroxide oxidation reaction at 25℃ for a total time of 80 min.

[0042] Example 3: A method for preparing sodium stannate at low temperature using ultrasonically enhanced tin oxide sheets, the specific steps of which are as follows:

[0043] (1) Add high-purity tin sheet to a sodium hydroxide solution with a concentration of 4 mol / L. Under ultrasonic conditions (ultrasonic power of 400W, frequency of 24kHz), control the temperature of the sodium hydroxide solution at 25℃, and slowly add hydrogen peroxide at a rate of 3 mL / min until the preset total addition amount is 26%, and continue ultrasonic enhancement oxidation reaction for 20 min. The mass concentration of the hydrogen peroxide is 30%, and the preset total addition amount of hydrogen peroxide is 1.8 times the molar amount of high-purity tin sheet. The solid-liquid ratio of high-purity tin sheet to sodium hydroxide solution is 1:5 g:mL.

[0044] (2) Under ultrasonic conditions (ultrasonic power of 400W, frequency of 24kHz) and solution temperature of 25℃, hydrogen peroxide was slowly added in portions (each time at a rate of 2mL / min) and the ultrasonic-enhanced oxidation reaction was continued. The amount of hydrogen peroxide added each time was 12% of the preset total amount. The ultrasonic-enhanced oxidation reaction was carried out for 5 minutes after each addition of hydrogen peroxide. After the hydrogen peroxide was completely added according to the preset total amount, the ultrasonic-enhanced oxidation reaction was continued until the tin sheet was completely dissolved to obtain a sodium stannate solution. In this embodiment, the total time of hydrogen peroxide oxidation reaction was 58 minutes and the total reaction time was 83 minutes.

[0045] (3) The sodium stannate solution is successively filtered to remove impurities, concentrated and crystallized under reduced pressure, separated by centrifugation, washed and dried to obtain sodium stannate product;

[0046] In this embodiment, the tin sheet dissolution rate is 100%.

[0047] Example 4: A method for preparing sodium stannate at low temperature using ultrasonically enhanced tin oxide sheets, the specific steps of which are as follows:

[0048] (1) Add high-purity tin sheet to a sodium hydroxide solution with a concentration of 4 mol / L. Under ultrasonic conditions (ultrasonic power of 300W, frequency of 24kHz), control the temperature of the sodium hydroxide solution at 30℃, slowly add hydrogen peroxide at a rate of 3 mL / min to 30% of the preset total addition amount, and continue ultrasonic enhancement oxidation reaction for 8 min; the mass concentration of the hydrogen peroxide is 30%, and the preset total addition amount of hydrogen peroxide is 1.5 times the molar amount of high-purity tin sheet; the solid-liquid ratio of high-purity tin sheet to sodium hydroxide solution is 1:5 g:mL.

[0049] (2) Under ultrasonic conditions (ultrasonic power of 300W, frequency of 24kHz) and solution temperature of 30℃, hydrogen peroxide was slowly added in portions (each time at a rate of 2mL / min) and the ultrasonic-enhanced oxidation reaction was continued. The amount of hydrogen peroxide added each time was 10% of the preset total amount. The ultrasonic-enhanced oxidation reaction was carried out for 8 minutes after each addition of hydrogen peroxide. After the hydrogen peroxide was completely added according to the preset total amount, the ultrasonic-enhanced oxidation reaction was continued until the tin sheet was completely dissolved to obtain a sodium stannate solution. In this embodiment, the total time of hydrogen peroxide oxidation reaction was 55 minutes and the total reaction time was 71 minutes.

[0050] (3) The sodium stannate solution is successively filtered to remove impurities, concentrated and crystallized under reduced pressure, separated by centrifugation, washed and dried to obtain sodium stannate product;

[0051] In this embodiment, the tin sheet dissolution rate is 100%.

[0052] The specific embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for preparing sodium stannate at low temperature using ultrasonically enhanced tin oxide sheets, characterized in that, The specific steps are as follows: (1) Add high-purity tin sheet to sodium hydroxide solution. Under ultrasonic conditions, control the temperature of sodium hydroxide solution at 20~30℃, slowly add hydrogen peroxide to 20~30% of the preset total addition amount, and continue ultrasonic enhancement oxidation reaction for 7~10 min; the addition rate of hydrogen peroxide is 2~4 mL / min. (2) Under ultrasonic conditions and a solution system temperature of 20-30℃, hydrogen peroxide is slowly added in multiple portions and then ultrasonically enhanced oxidation reaction is continued. The amount of hydrogen peroxide added each time is 10-15% of the preset total amount. After each addition of hydrogen peroxide, ultrasonic enhanced oxidation reaction is carried out for 4-8 minutes. After the hydrogen peroxide is completely added according to the preset total amount, ultrasonic enhanced oxidation reaction is continued until the tin sheet is completely dissolved to obtain sodium stannate solution. The addition rate of hydrogen peroxide is 1-4 mL / min. (3) The sodium stannate solution is filtered, concentrated, separated, washed and dried to obtain sodium stannate product.

2. The method for preparing sodium stannate at low temperature from ultrasonically enhanced tin oxide sheets according to claim 1, characterized in that: Step (1) The concentration of sodium hydroxide solution is 3~6 mol / L, and the solid-liquid ratio of high-purity tin sheet to sodium hydroxide solution is 1:4~8 g:mL.

3. The method for preparing sodium stannate at low temperature from ultrasonically enhanced tin oxide sheets according to claim 1, characterized in that: The hydrogen peroxide concentration is 15-30%, and the preset total amount of hydrogen peroxide added is 1.2-2 times the molar amount of high-purity tin sheet.

4. The method for preparing sodium stannate at low temperature from ultrasonically enhanced tin oxide sheets according to claim 1, characterized in that: The ultrasonic power is 180~300W and the frequency is 20~40kHz.

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