A method for preparing nano tin dioxide-based gas sensitive material by recycling electrolytic tin anode slime

Abstract

The application belongs to the technical field of resource recycling and semiconductor gas sensitive material preparation, and particularly relates to a method for recycling and preparing nano tin dioxide-based gas sensitive material by using electrolytic tin anode slime. The application uses the anode slime generated in electrolytic tin refining, and obtains the porous nano SnO2 solid through the following steps: pickling and removing impurities, hydrothermal pore forming modification, and loading gallium after compounding a porous structure regulator, so that the structure is uniform, the catalytic activity is higher, the response to formaldehyde is fast, and the selectivity is good. The method is suitable for large-scale preparation and has a wide application prospect in the field of environmental monitoring.

Description

Technical Field

[0001] This invention belongs to the field of resource recycling and semiconductor gas-sensitive material preparation technology, specifically relating to a method for preparing nano-tin dioxide-based gas-sensitive materials by recycling electrolytic tin anode mud. Background Technology

[0002] During the electrolytic refining of crude tin, impurities in the anode material continuously accumulate and deposit, generating a large amount of electrolytic tin anode mud. This type of industrial solid waste is rich in tin components and is a high-quality renewable resource for preparing tin dioxide gas-sensitive materials, with enormous resource utilization potential. Formaldehyde is a toxic and harmful volatile pollutant. Nano-tin dioxide gas-sensitive materials, with their large specific surface area and excellent stability, have broad application prospects in the field of rapid formaldehyde detection.

[0003] Currently, the recycling of electrolytic tin anode mud mainly focuses on precious metal extraction and crude tin recovery, neglecting the high-value-added utilization of tin resources. Conventional recycling and modification methods often employ high-energy ball milling and barium / iron doping, which easily lead to particle agglomeration, pore structure collapse, and weak gas adsorption and diffusion capabilities. At the same time, traditional doping elements have limited formaldehyde catalytic activity, resulting in gas-sensitive materials with low sensitivity, high operating temperature, and slow response recovery speed, making it difficult to meet the requirements for high-performance formaldehyde detection.

[0004] To address the aforementioned issues, it is urgent to develop high-performance formaldehyde gas-sensitive materials to achieve high-value utilization of solid waste while effectively improving the performance defects of existing materials. Summary of the Invention

[0005] To address the problems of easy agglomeration, poor pore structure, and low formaldehyde sensitivity in existing tin-based formaldehyde gas-sensitive materials using barium and iron doping and ball milling processes, and to solve the shortcomings of low utilization rate of electrolytic tin anode mud and insufficient selectivity of conventional tin dioxide, this invention provides a method for preparing formaldehyde gas-sensitive materials by recycling electrolytic tin anode mud. This invention employs solvothermal porous control combined with gallium loading modification, which, unlike traditional ball milling processes, results in a material with uniform structure, higher catalytic activity, faster formaldehyde response, and better selectivity, achieving high-value utilization of solid waste.

[0006] To achieve the above objectives, on the one hand, the present invention provides a nano-SnO2 gas sensor. The device has a planar structure and consists of interdigitated gold-plated electrodes on the front side of a ceramic substrate, a sensitive material film coated on the interdigitated electrodes, and a micro high-temperature heating plate on the back side of the ceramic substrate. The sensitive material film is a porous nano-SnO2 gas-sensitive material obtained by acid washing to remove impurities, hydrothermal pore-forming modification, and composite with a porous structure regulator and gallium loading.

[0007] On the other hand, this application also provides a method for preparing the above-described nano-SnO2 gas sensor, the method comprising the following steps: (1) Nitric acid solution is added to electrolytic tin anode mud, and after stirring, the reaction solution is washed with deionized water and ethanol respectively, dried and calcined to obtain pretreated tin mud; the mass fraction of the nitric acid solution is 5%~15%; (2) The pretreated tin mud was mixed with citric acid, deionized water and ethanol and stirred. Then, porous structure regulator powder was added and stirred for 1 hour to obtain a mixture. The mixture was reacted at 140~160℃ for 8~12h. After the reaction was completed, it was naturally cooled to room temperature. It was washed with deionized water and anhydrous ethanol respectively and dried. The dried powder was then calcined to obtain porous nano SnO2. (3) Porous nano-SnO2 was dispersed in polyethylene glycol 400 and the corresponding gallium precursor was added. Sodium sulfite solution was slowly added during magnetic stirring and stirring was continued for 1 hour. After centrifugation and washing with deionized water and anhydrous ethanol, the material was dried to obtain a porous SnO2 gas-sensitive material co-loaded with a porous structure regulator and a metal. The solid-liquid ratio of the porous nano-SnO2 to polyethylene glycol was 1:20 g / ml. The drying temperature was 100℃ and the time was 10 hours. (4) The porous SnO2 gas-sensitive material prepared in step (3) is mixed with deionized water at a mass ratio of 1~3:1 and ground into a slurry. The slurry is coated on a ceramic substrate with interdigitated electrodes. After natural drying, the working electrode and the heating electrode are welded to the gas-sensitive element base to obtain a nano SnO2 gas sensor.

[0008] Furthermore, in step (1), the solid-liquid ratio of the electrolytic tin anode mud to the nitric acid solution is (8-12):(100-150) (g / ml).

[0009] Furthermore, in step (3), the amount of sodium sulfite used is 1.5 to 3 times the molar equivalent of the theoretical reduction amount of metal ions.

[0010] Furthermore, in step (3), the solid-liquid ratio of the porous nano-SnO2 to polyethylene glycol 400 is 1.5:20-30 (g / ml).

[0011] Furthermore, in step (3), the concentration of the gallium precursor is 2-8 mol%.

[0012] Furthermore, in step (1), the stirring temperature is 50~80℃ and the stirring time is 0.5~2h.

[0013] Furthermore, in step (2), the roasting temperature is 140~160℃ and the time is 8~12 hours.

[0014] Furthermore, in step (2), the calcination temperature is 400~500℃ and the time is 1~3 hours.

[0015] Furthermore, in step (1), the drying temperature is 60~80℃ and the drying time is 8~12 hours; in step (2), the drying temperature is 50~80℃ and the drying time is 8~12 hours.

[0016] Beneficial effects (1) Using electrolytic tin anode mud as raw material, we can realize the high-value utilization of tin resources, reduce raw material costs, and reduce solid waste storage pollution.

[0017] (2) By regulating the porous structure, the specific surface area is increased, providing more gas adsorption and reaction sites, and significantly improving the response sensitivity.

[0018] (3) The use of solvothermal porous construction + gallium doping improves the selectivity and response recovery characteristics of formaldehyde. Unlike the existing Ba / Fe doping and ball milling process, the material is more uniform, more sensitive and faster in response.

[0019] (4) The process is simple, the conditions are mild, and the repeatability is good. It is suitable for large-scale preparation and has broad application prospects in the field of environmental monitoring.

[0020] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Detailed Implementation

[0021] The embodiments of this application will now be described in more detail. While embodiments of this application are shown below, it should be understood that this application can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to make this application more thorough and complete, and to fully convey the scope of this application to those skilled in the art.

[0022] The gas-sensitive response value of this invention is tested using the static gas mixing method. The gas-sensitive testing system measures and records the steady-state resistance value Ra of the sensor in clean air and the steady-state resistance value Rg of the target formaldehyde gas. The response value is calculated using the formula: S=Ra / Rg. The sensor performance is comprehensively judged by the response value (sensitivity), optimal operating temperature, response time, recovery time, selectivity, and long-term stability.

[0023] Method for fabricating gallium-doped tin dioxide-based formaldehyde gas sensor in Example 1 1) Place 8-12g of electrolytic tin anode mud in a container, add 100-150ml of 5%-15% nitric acid solution, and stir the mixture at 50-80℃ for 0.5-2 hours. After the reaction is complete, centrifuge the mixture and wash it three times each with deionized water and anhydrous ethanol until neutral. Dry the solid product in air at 50-80℃ for 8-12 hours, then calcine it in a muffle furnace at 500-600℃ for 1-3 hours. After natural cooling, grind the product to obtain pretreated anode mud powder. 2) Weigh the pretreated anode mud powder. The mass-to-volume ratio of anode mud (g): citric acid (g): deionized water (ml): anhydrous ethanol (ml) is approximately 8:1:(20~30):(20~30). Mix thoroughly, then add 3~7 mol% of the porous structure regulator, graphitic carbon nitride (g-C3N4), and continue stirring until there are no obvious agglomerated particles. After standing for 1 minute, there is no obvious stratification, and the mixture is in a uniform suspension state. Transfer the mixture to a high-pressure reactor, seal it, and react at a constant temperature of 140~180℃ for 6~12 hours. After the reaction was completed, the product was naturally cooled to room temperature. It was then centrifuged at 3000-5000 r / min for 8-10 min, washed three times each with deionized water and anhydrous ethanol until the pH was neutral, dried at 50-80℃ for 8-12 hours, and finally calcined in air at 400-500℃ for 1-3 hours to obtain porous nano-tin dioxide (SnO2) solid powder, which provides abundant gas adsorption and reaction sites. 3) Disperse 1-2g of the above porous nano-tin dioxide powder in 25-30ml of dispersant (polyethylene glycol 400), add 4-6mol% of gallium precursor gallium nitrate, and slowly add sodium sulfite aqueous solution with a theoretical reduction capacity of 1.5-3 times the molar equivalent of gallium ions. Stir the reaction at room temperature for 0.5-2 hours. After the reaction is complete, centrifuge at 3000-5000r / min for 8-10min to collect the solid product. Wash it alternately with deionized water and anhydrous ethanol (volume ratio of 1:1), and dry it at 80-120℃ for 8-12 hours to obtain a tin dioxide gas-sensitive material co-doped with a porous structure regulator and gallium. 4) Mix the obtained gas-sensitive material with deionized water at a mass ratio of 1 to 3:1 and grind it into a slurry. Coat the slurry evenly on the surface of a ceramic substrate with interdigitated gold-plated electrodes. After air drying at room temperature, weld the working electrode and heating electrode of the ceramic substrate to the gas-sensitive element base to obtain the formaldehyde gas sensor.

[0024] Tests showed that the sensor in this embodiment has a response value of 28~32 for 100ppm formaldehyde gas, with a typical value of 29.8. The optimal operating temperature is 200~220℃, the response time is ≤12s, the recovery time is ≤18s, and the overall performance is optimal.

[0025] Example 2: Preparation method of a low-doped gallium tin dioxide-based formaldehyde gas sensor This embodiment discloses a method for preparing a gallium-doped tin dioxide-based formaldehyde gas sensor based on the recovery of electrolytic tin anode mud. Except for the following steps, the remaining steps are the same as in Embodiment 1.

[0026] 2) Weigh the pretreated anode mud powder. The mass-to-volume ratio of anode mud (g): citric acid (g): deionized water (ml): anhydrous ethanol (ml) is approximately 5:1:(20~30):(20~30). Mix thoroughly, then add 3~7 mol% of the porous structure regulator, graphitic carbon nitride (g-C3N4), and continue stirring until there are no obvious agglomerated particles. After standing for 1 minute, there is no obvious stratification, and the mixture is in a uniform suspension state. Transfer the mixture to a high-pressure reactor, seal it, and react at a constant temperature of 140~180℃ for 6~12 hours. After the reaction was completed, the product was naturally cooled to room temperature. It was then centrifuged at 3000-5000 r / min for 8-10 min, washed three times each with deionized water and anhydrous ethanol until the pH was neutral, dried at 50-80℃ for 8-12 hours, and finally calcined in air at 400-500℃ for 1-3 hours to obtain porous nano-tin dioxide (SnO2) solid powder, which provides abundant gas adsorption and reaction sites. 3) Disperse approximately 1.5g of the porous nano-tin dioxide powder in 25-30ml of polyethylene glycol 400 dispersant, add 1-3mol% of gallium precursor gallium nitrate, and slowly add sodium sulfite aqueous solution with a theoretical gallium ion reduction capacity of 1.5-3 times the molar equivalent. Stir the reaction at room temperature for 0.5-2 hours. After the reaction is complete, centrifuge at 3000-5000r / min for 8-10min to collect the solid product. Wash the solid product alternately with deionized water and anhydrous ethanol, and dry it at 80-120℃ for 8-12 hours to obtain a tin dioxide gas-sensitive material co-doped with a porous structure regulator and gallium.

[0027] Tests showed that the sensor in this embodiment has a response value of 22~25 for 100ppm formaldehyde gas, with a typical value of 23.5, an optimal operating temperature of 220~240℃, a response time of ≤15s, and a recovery time of ≤20s, demonstrating good gas sensing performance.

[0028] Example 3: Preparation method of highly doped gallium tin dioxide-based formaldehyde gas sensor This embodiment discloses a method for preparing a gallium-doped tin dioxide-based formaldehyde gas sensor based on the recovery of electrolytic tin anode mud. Except for the following steps, the remaining steps are the same as in Embodiment 1.

[0029] 2) Weigh the pretreated anode mud powder. The mass-to-volume ratio of anode mud (g): citric acid (g): deionized water (ml): anhydrous ethanol (ml) is approximately 10:1:(20~30):(20~30). Mix thoroughly, then add 3~7 mol% of the porous structure regulator, graphitic carbon nitride (g-C3N4), and continue stirring until there are no obvious agglomerated particles. After standing for 1 minute, there is no obvious stratification, and the mixture is in a uniform suspension state. Transfer the mixture to a high-pressure reactor and seal it. React at a constant temperature of 140~180℃ for 6~12 hours. After the reaction was completed, the product was naturally cooled to room temperature. It was then centrifuged at 3000-5000 r / min for 8-10 min, washed three times each with deionized water and anhydrous ethanol until the pH was neutral, dried at 50-80℃ for 8-12 hours, and finally calcined in air at 400-500℃ for 1-3 hours to obtain porous nano-tin dioxide (SnO2) solid powder, which provides abundant gas adsorption and reaction sites. 3) Disperse approximately 1.5g of the porous nano-tin dioxide powder in 25-30ml of polyethylene glycol 400 dispersant, add 7-9mol% gallium precursor gallium nitrate, and slowly add sodium sulfite aqueous solution with a theoretical gallium ion reduction capacity of 1.5-3 times the molar equivalent. Stir the reaction at room temperature for 0.5-2 hours. After the reaction, centrifuge at 3000-5000 r / min for 8-10 min to collect the solid product. Wash the solid product alternately with deionized water and anhydrous ethanol, and dry it at 80-120℃ for 8-12 hours to obtain a tin dioxide gas-sensitive material co-doped with a porous structure regulator and gallium.

[0030] Tests showed that the sensor in this embodiment has a response value of 25~28 for 100ppm formaldehyde gas, with a typical value of 26.2, an optimal operating temperature of 215~235℃, a response time of ≤13s, a recovery time of ≤19s, high sensitivity, and excellent long-term stability.

[0031] The various embodiments of this application have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A nano-SnO2 gas sensor, the device having a planar structure, comprising interdigitated gold-plated electrodes on the front side of a ceramic substrate, a thin film of sensitive material coated on the interdigitated electrodes, and a miniature high-temperature heating element on the back side of the ceramic substrate, characterized in that... The sensitive material film is a porous nano-SnO2 gas-sensitive material obtained by acid washing to remove impurities, regulating the porous structure, and combining it with a porous structure regulator and gallium loading.

2. A method for preparing a nano-SnO2 gas sensor according to claim 1, characterized in that, The preparation method includes the following steps: (1) Nitric acid solution is added to electrolytic tin anode mud, and after stirring, the reaction solution is washed with deionized water and ethanol respectively, dried and calcined to obtain pretreated tin mud; the mass fraction of the nitric acid solution is 5%~15%; (2) The pretreated tin mud was mixed with citric acid, deionized water and ethanol and stirred. Then, porous structure regulator powder was added and stirred for 1 hour to obtain a mixture. The mixture was reacted at 140~160℃ for 8~12h. After the reaction was completed, it was naturally cooled to room temperature. It was washed with deionized water and anhydrous ethanol respectively and dried. The dried powder was then calcined to obtain porous nano SnO2. (3) Porous nano-SnO2 was dispersed in polyethylene glycol 400 and the corresponding gallium precursor was added. Sodium sulfite solution was slowly added during magnetic stirring and stirring was continued for 1 hour. After centrifugation and washing with deionized water and anhydrous ethanol, the material was dried to obtain a porous SnO2 gas-sensitive material co-loaded with a porous structure regulator and a metal. The solid-liquid ratio of the porous nano-SnO2 to polyethylene glycol was 1:20 g / ml. The drying temperature was 100℃ and the time was 10 hours. (4) The porous SnO2 gas-sensitive material prepared in step (3) is mixed with deionized water at a mass ratio of 1~3:1 and ground into a slurry. The slurry is coated on a ceramic substrate with interdigitated electrodes. After natural drying, the working electrode and the heating electrode are welded to the gas-sensitive element base to obtain a nano SnO2 gas sensor.

3. The preparation method according to claim 2, characterized in that, In step (1), the solid-liquid ratio of the electrolytic tin anode mud to the nitric acid solution is (8-12):(100-150) (g / ml).

4. The preparation method according to claim 2, characterized in that, In step (3), the amount of sodium sulfite used is 1.5 to 3 times the molar equivalent of the theoretical reduction amount of metal ions.

5. The preparation method according to claim 2, characterized in that, In step (3), the solid-liquid ratio of the porous nano-SnO2 to polyethylene glycol 400 is 1.5:20-30 (g / ml).

6. The preparation method according to claim 2, characterized in that, In step (3), the concentration of the gallium precursor is 2-8 mol%.

7. The preparation method according to claim 2, characterized in that, In step (1), the stirring temperature is 50~80℃ and the stirring time is 0.5~2h.

8. The preparation method according to claim 2, characterized in that, In step (2), the roasting temperature is 140~160℃ and the time is 8~12 hours.

9. The preparation method according to claim 2, characterized in that, In step (2), the calcination temperature is 400~500℃ and the time is 1~3 hours.

10. The preparation method according to claim 2, characterized in that, In step (1), the drying temperature is 60~80℃ and the drying time is 8~12 hours; in step (2), the drying temperature is 50~80℃ and the drying time is 8~12 hours.