A method for synthesizing spinel nanomaterials based on subcritical technology

Abstract

The application discloses a method for synthesizing spinel nanomaterials based on subcritical technology, and the specific preparation method is as follows: precursor solution and additives are put into a high-pressure reaction kettle for mixing, then the characteristics of high diffusion coefficient, high reaction rate and low surface tension of subcritical water are utilized, a heating device (160-180 DEG C) and different reaction atmospheres (oxygen, helium or nitrogen) are used to promote the uniform mixing and high-efficiency reaction between reactants, and the reaction is kept for 30-180 min, so that the crystal nucleates rapidly and forms nanoparticles. Compared with traditional synthesis methods of spinel nanomaterials, the method has good safety, stability and controllability, and is a subcritical technology method for synthesizing spinel nanomaterials with wide prospect.

Description

Technical Field

[0001] This invention belongs to the field of preparation technology of multi-metal materials, specifically relating to a method for synthesizing spinel-type nanomaterials based on subcritical technology. Background Technology

[0002] With the continuous advancement of nanotechnology and the deepening of interdisciplinary research, nanomaterials have attracted much attention due to their advantages such as relatively small volume, large specific surface area, and high surface energy and surface binding energy. By precisely controlling the composition, distribution, and microstructure of different metal elements, these materials can significantly improve their catalytic performance, electrical properties, magnetic properties, and biocompatibility, thus playing a crucial role in multiple fields such as catalytic chemistry, energy conversion and storage, biomedicine, and electronic information devices.

[0003] However, traditional methods for synthesizing spinel-type nanomaterials, such as sol-gel, coprecipitation, and hydrothermal methods, often suffer from problems such as long preparation times, difficulty in controlling the reaction atmosphere, and uneven product morphology and size distribution. For example, although the sol-gel method allows for controllable and easy doping of components, its raw materials are expensive and the reaction time is long; although the coprecipitation method produces small and uniform particles, the materials are prone to agglomeration and the atmosphere cannot be precisely controlled to obtain the desired material with specific functions in one step; although the hydrothermal method produces products with high purity and narrow particle size distribution, the preparation time is too long and the reaction atmosphere cannot be precisely controlled.

[0004] Subcritical technology is a method that utilizes the unique properties (such as density, solubility, and diffusivity) of fluids (usually water or organic solvents) to facilitate chemical reactions and material synthesis under specific temperatures and pressures. The principle involves mixing precursor solutions and additives in a mixer, followed by rapid heating in a reactor, causing crystals to nucleate quickly and nanoparticles to precipitate. Compared to traditional methods, subcritical technology offers advantages such as shorter reaction times, easier control of the reaction atmosphere, milder processing, and smaller and more uniform particle size distribution, providing a significantly advantageous approach for constructing spinel-type nanomaterials and micromaterials. Summary of the Invention

[0005] To overcome the shortcomings and deficiencies of existing technologies, the present invention aims to provide a method for synthesizing spinel-type nanomaterials based on subcritical technology. By adjusting the temperature and introducing different reaction atmospheres during the reaction process, the reaction rate and the growth rate of the nanostructures can be controlled, thereby achieving structural regulation of the spinel-type nanomaterials.

[0006] The subcritical technique for synthesizing spinel-type nanomaterials is characterized by the following steps:

[0007] 1) Dissolve various metal salts in ultrapure water, sonicate them evenly, and set aside. Then weigh out organic additives and dissolve them in ultrapure water. Mix the solutions to obtain a mixture, and transfer it to a subcritical high-pressure reactor after sonication.

[0008] 2) Disperse the alkaline additive in ultrapure water to obtain an alkaline solution. Add the alkaline solution dropwise to the mixture obtained in step 1) and stir to mix evenly. Seal the reactor and introduce air or other gases to remove air and dissolved oxygen from the system. Under magnetic stirring, use heating and pressurization devices to precisely control the temperature and pressure inside the subcritical high-pressure reactor and maintain it for 30~180 min to form a subcritical fluid with a certain pressure inside the subcritical high-pressure reactor.

[0009] 3) After the reaction is complete, the solution prepared in step 2) is centrifuged, washed with ultrapure water and anhydrous ethanol to remove residual salts, and dried in an oven overnight to obtain spinel-type nanomaterials.

[0010] Further, the metal salt mentioned in step 1) is a nitrate or chloride salt of aluminum, cobalt, manganese, zinc, bismuth, indium or iron.

[0011] Further, the organic additive mentioned in step 1) is citric acid, thioacetamide, hexadecyltrimethylammonium bromide or urea, and the ratio of the total molar amount of metal atoms in the metal salt solution to the molar amount of the added organic additive is 1:0.8~5.

[0012] Further, the alkaline additive mentioned in step 2) is sodium hydroxide, ammonia, carbonate or bicarbonate, and the ratio of the amount of alkali added in the alkaline solution to the total molar amount of metal atoms in the metal salt solution is 2~8:1.

[0013] Furthermore, in step 2), the temperature is controlled at 160-180℃, and when the prepared spinel-type nanomaterial is a sulfide catalyst, nitrogen is used, and when the prepared spinel-type nanomaterial is an oxidation catalyst, oxygen is used.

[0014] The beneficial effects achieved by this invention are:

[0015] 1) The ZnIn2S4 catalyst prepared by the subcritical technology of this invention has a more open petal structure, a larger and more uniform particle surface area without agglomeration, and its efficiency in photocatalytic degradation of SMX is improved by 17.5% compared with the ZnIn2S4 catalyst prepared by the hydrothermal method; the ZnCo2O4 catalyst prepared by the subcritical technology has a nanoparticle cluster structure, and its conversion rate in the catalytic reaction of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid is improved by 9.8% and the yield is improved by 11.5% compared with the ZnCo2O4 catalyst prepared by the hydrothermal method.

[0016] 2) This invention has discovered that in the process of preparing catalysts using subcritical technology, different atmospheres are suitable for different catalyst types. The growth environment of nanostructures can be controlled by adjusting the atmosphere, thereby adjusting the particle morphology of the material. When preparing spinel-type sulfide catalysts, nitrogen atmosphere is more suitable, while oxygen atmosphere is more suitable when preparing spinel-type oxidation catalysts. Attached Figure Description

[0017] Figure 1 XRD and SEM images of CoAl2O4 prepared in Example 1;

[0018] Figure 2 XRD and SEM images of CoAl2O4 prepared in Example 2;

[0019] Figure 3 XRD and SEM images of CuCo2O4 prepared in Example 3;

[0020] Figure 4 XRD, SEM, and TEM images of ZnCo2O4 prepared in Example 4;

[0021] Figure 5 XRD, SEM, and TEM images of ZnIn2S4 prepared in Example 5;

[0022] Figure 6 SEM image of ZnCo2O4 prepared in Comparative Example 1;

[0023] Figure 7 SEM comparison images of ZnIn2S4 prepared in Example 6 and Comparative Example 2;

[0024] Figure 8 This is a diagram of a subcritical fluid reactor apparatus.

[0025] In the diagram: 1. Gas storage tank; 2. Intermediate container; 3. Subcritical high-pressure reactor; 4. Manual pump. Detailed Implementation

[0026] The present invention will be further described below with reference to specific embodiments and accompanying drawings, but the scope of protection of the present invention is not limited thereto.

[0027] The apparatus used in the subcritical technology in the following embodiments is as follows: Figure 8 As shown, the gas storage tank 1 is connected to the intermediate container 2. The water storage end of the intermediate container 2 is connected to the manual pump 4, and the gas storage end of the intermediate container 2 is connected to the subcritical high-pressure reactor 3. The manual pump 4 pushes pressure to the intermediate container 2, so that the gas enters the subcritical high-pressure reactor 3.

[0028] Example 1: CoAl2O4 catalyst synthesized using subcritical technology, the steps of which are as follows:

[0029] Dissolve 0.291 g Co(NO3)2·6H2O and 0.750 g Al(NO3)3·9H2O in 20 mL of ultrapure water, and sonicate until homogeneous. Then weigh 0.630 g citric acid and dissolve it in 20 mL of ultrapure water. Mix the two solutions to obtain a citric acid chelate metal mixture. After sonication, transfer the mixture to a subcritical high-pressure reactor. Then weigh 0.360 g NaOH and disperse it in another 40 mL of ultrapure water to obtain an alkaline solution. The alkaline solution was slowly added dropwise to the above-mentioned citric acid chelated metal mixture and stirred until homogeneous. The reactor was sealed, and oxygen was introduced to purge the air from the system. Under magnetic stirring, the pressure inside the subcritical high-pressure reactor was controlled at 0.1 MPa by operating a manual pump, and the temperature inside the subcritical high-pressure reactor was controlled at 180℃ by the control panel and temperature measuring line. After maintaining the reaction for 120 min, the reactor was centrifuged. The obtained solid was washed three times with ultrapure water and anhydrous ethanol to remove residual salts, and then vacuum dried in an oven at 60℃ to obtain the CoAl2O4 catalyst.

[0030] The XRD pattern of the CoAl2O4 catalyst prepared in Example 1 shows that the method of the present invention successfully prepared the CoAl2O4 catalyst (e.g. Figure 1 (a)); SEM images show that the CoAl2O4 prepared by the method of this invention has a granular spherical nanostructure (e.g., Figure 1 (b) in the middle.

[0031] Example 2: CoAl2O4 catalyst synthesized using subcritical technology, the steps of which are as follows:

[0032] Dissolve 0.291 g Co(NO3)2·6H2O and 0.750 g Al(NO3)3·9H2O in 20 mL of ultrapure water, and sonicate until homogeneous. Then weigh 0.630 g citric acid and dissolve it in 20 mL of ultrapure water. Mix the two solutions to obtain a citric acid chelate metal mixture. After sonication, transfer the mixture to a subcritical high-pressure reactor. Then weigh 0.360 g NaOH and disperse it in another 40 mL of ultrapure water to obtain an alkaline solution. The alkaline solution was slowly added dropwise to the above-mentioned citric acid chelated metal mixture and stirred until homogeneous. The reactor was sealed, and nitrogen gas was introduced to purge air and dissolved oxygen from the system. Under magnetic stirring, the pressure inside the high-pressure reactor was controlled to 0.1 MPa by operating a manual pump, and the temperature inside the supercritical high-pressure reactor was controlled to 180℃ by the control panel and temperature measuring line. After maintaining the reaction for 120 min, the mixture was centrifuged. The obtained solid was washed three times with ultrapure water and anhydrous ethanol to remove residual salts, and then vacuum dried in an oven at 60℃ to obtain the CoAl2O4 catalyst.

[0033] The XRD pattern of the CoAl2O4 catalyst prepared in Example 2 shows that the method of the present invention successfully prepared the CoAl2O4 catalyst (e.g. Figure 2 (a)); SEM images show that the CoAl2O4 particles prepared by the method of this invention have an uneven structure, containing both plate-like structures and small particle structures (e.g., Figure 2 (b) in the middle.

[0034] SEM images of CoAl2O4 prepared in Examples 1 and 2 (e.g.) Figure 1 (b) and Figure 2 The comparison in (b) shows that the atmosphere introduced during the preparation of spinel-type oxide catalysts differs. Example 1 used oxygen, while Example 2 used nitrogen. Introducing oxygen resulted in more uniform particles compared to introducing nitrogen. This is because when the catalyst is a spinel-type oxide, the introduction of nitrogen can cause interference, leading to changes in the catalyst's crystal structure. Oxygen, a strong oxidant, can easily oxidize the desired substance, and in an oxygen-rich environment, it promotes uniform particle growth, preventing excessive agglomeration or irregular growth. Therefore, when the desired substance is a spinel-type oxide, introducing oxygen results in more uniform catalyst particles.

[0035] Example 3: A CuCo2O4 catalyst synthesized using a subcritical technique, the steps of which are as follows:

[0036] Dissolve 0.242 g Cu(NO3)2·3H2O and 0.582 g Co(NO3)2·6H2O in 20 mL of ultrapure water, and sonicate until homogeneous. Then weigh 0.630 g citric acid and dissolve it in 20 mL of ultrapure water. Mix the two solutions to obtain a citric acid chelate metal mixture. After sonication, transfer the mixture to a subcritical high-pressure reactor. Then weigh 0.360 g NaOH and disperse it in another 40 mL of ultrapure water to obtain an alkaline solution. The alkaline solution was slowly added dropwise to the above-mentioned citric acid chelated metal mixture and stirred until homogeneous. The reactor was sealed, and oxygen was introduced to purge the air from the system. Under magnetic stirring, the pressure inside the high-pressure reactor was controlled to 0.1 MPa by operating a manual pump, and the temperature inside the supercritical high-pressure reactor was controlled to 180℃ by the control panel and temperature measuring line. After maintaining the reaction for 120 min, the mixture was centrifuged. The obtained solid was washed three times with ultrapure water and anhydrous ethanol to remove residual salts, and then vacuum dried in an oven at 60℃ to obtain the CuCo2O4 catalyst.

[0037] The XRD pattern of the CuCo2O4 catalyst prepared in Example 3 shows that the method of the present invention successfully prepared the CuCo2O4 catalyst (e.g. Figure 3(a)); SEM images show that the CuCo2O4 prepared by the method of this invention has a nanoparticle cluster structure (e.g., Figure 3 (b) in the middle.

[0038] Example 4: Synthesis and application of ZnCo2O4 catalyst using subcritical technology, the steps of which are as follows:

[0039] Dissolve 0.298 g Zn(NO3)2·6H2O and 0.582 g Co(NO3)2·6H2O in 20 mL of ultrapure water, and sonicate until homogeneous. Then weigh 0.630 g citric acid and dissolve it in 20 mL of ultrapure water. Mix the two solutions to obtain a citric acid chelate metal mixture. After sonication, transfer the mixture to a subcritical high-pressure reactor. Then weigh 0.360 g NaOH and disperse it in another 40 mL of ultrapure water to obtain an alkaline solution. The alkaline solution was slowly added dropwise to the above-mentioned citric acid chelated metal mixture and stirred until homogeneous. The reactor was sealed, and oxygen was introduced to purge the air from the system. Under magnetic stirring, the pressure inside the subcritical high-pressure reactor was controlled at 0.1 MPa by operating a manual pump, and the temperature inside the subcritical high-pressure reactor was controlled at 160℃ by the control panel and temperature measuring line. After maintaining the reaction for 120 min, the reactor was centrifuged. The obtained solid was washed three times with ultrapure water and anhydrous ethanol to remove residual salts, and then vacuum dried in an oven at 60℃ to obtain the ZnCo2O4 catalyst.

[0040] The XRD pattern of the ZnCo2O4 catalyst prepared in Example 4 shows that the method of the present invention successfully prepared the ZnCo2O4 catalyst (e.g. Figure 4 (a) in the image); SEM image (e.g. Figure 4 (b) shows that the ZnCo2O4 prepared by the method of the present invention has a nanoparticle cluster structure, and the TEM image shows that the nanoparticles have a polyhedral structure (e.g., Figure 4 (c) in the middle.

[0041] The ZnCo2O4 sample prepared in Example 4 was used to catalyze the conversion of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid. The specific process is as follows:

[0042] 1) A microreactor device with a 25 mL inner liner was used, heated and temperature controlled by a heating mantle. 50 mg of ZnCo2O4 material prepared in Example 3 was added, along with 0.042 g of sodium bicarbonate and 5 mL of a 50 mM 5-hydroxymethylfurfural solution. The microreactor was sealed, and magnetic stirring was continuously performed at 600 rpm. Oxygen was pressurized to 1.5 MPa, and the reaction temperature was raised to 130°C at a rate of 2°C / min. Timing was started after the temperature reached 130°C, and samples were collected after a reaction time of 8 hours.

[0043] 2) The reaction temperature was controlled at 130℃ for the oxidation of 5-hydroxymethylfurfural. After the oxidation reaction of 5-hydroxymethylfurfural reached stability, the conversion rate of 5-hydroxymethylfurfural (HMF) reached 86.7%, and the yield of 2,5-furandicarboxylic acid (FDCA) reached a maximum of 36.2%, as shown in Table 1.

[0044] Comparative Example 1: Preparation of ZnCo2O4 by hydrothermal method, the steps are as follows:

[0045] 0.298 g of Zn(NO3)2·6H2O and 0.582 g of Co(NO3)2·6H2O were dissolved in 20 mL of ultrapure water and sonicated until homogeneous. 0.630 g of citric acid was then dissolved in 20 mL of ultrapure water. The two solutions were mixed to obtain a citric acid-chelated metal mixture, which was then sonicated and transferred to a reaction vessel. 0.360 g of NaOH was dispersed in another 40 mL of ultrapure water to obtain an alkaline solution. The alkaline solution was slowly added dropwise to the citric acid-chelated metal mixture, and after thorough mixing, it was transferred to a 50 mL stainless steel autoclave lined with polytetrafluoroethylene. The autoclave was then sealed and heated in an oven at 160°C for 16 h. After the autoclave cooled naturally to room temperature, the prepared ZnCo2O4 was collected and washed three times with deionized water and anhydrous ethanol. The collected powder was dried overnight in a vacuum oven at 60°C to obtain the ZnCo2O4 catalyst.

[0046] SEM images of the ZnCo2O4 catalyst prepared in Comparative Example 1 show that the ZnCo2O4 prepared by the method described in Comparative Example 1 has a particulate nanostructure, but the particle size is uneven and agglomeration occurs. Figure 6 .

[0047] The ZnCo2O4 sample prepared in Comparative Example 1 was used to catalyze the conversion of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid. The specific process is as follows:

[0048] 1) A microreactor device with a 25 mL inner liner was used, heated and temperature controlled by a heating mantle. 50 mg of ZnCo₂O₄ material prepared in Comparative Example 1, 0.042 g of sodium bicarbonate, and 5 mL of 50 mM 5-hydroxymethylfurfural solution were added. The microreactor was sealed, magnetically stirred continuously at 600 rpm, oxygen was pressurized to 1.5 MPa, and the reaction temperature was raised to 130 °C at a rate of 2 °C / min. Timing was started after reaching 130 °C, and samples were collected after a reaction time of 8 hours.

[0049] 2) The reaction temperature was controlled at 130℃ for the oxidation of 5-hydroxymethylfurfural. After the oxidation reaction of 5-hydroxymethylfurfural reached stability, the conversion rate of 5-hydroxymethylfurfural reached 76.9%, and the yield of 2,5-furandicarboxylic acid reached a maximum of 24.7%. This indicates that the ZnCo2O4 catalyst prepared by this method can be used to catalyze the conversion of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid, and the conversion rate and yield are higher than those of the ZnCo2O4 catalyst prepared by the hydrothermal method (see Table 1).

[0050] Table 1. Comparison of catalytic effects of ZnCo2O4 catalysts prepared by different methods

[0051]

[0052] Example 5: The multi-metal nano-microstructure catalyst ZnIn2S4 was synthesized using a subcritical technique, and the steps are as follows:

[0053] 0.068 g ZnCl2 and 0.293 g InCl3·4H2O were dissolved in 20 mL of ultrapure water and sonicated until homogeneous. 0.15 g thioacetamide was then dissolved in 20 mL of ultrapure water. The two solutions were mixed to obtain a mixture. After sonication, the mixture was transferred to a subcritical high-pressure reactor. 0.360 g NaOH was then dispersed in another 40 mL of ultrapure water to obtain an alkaline solution. The alkaline solution was slowly added dropwise to the above citric acid chelate metal mixture and stirred until homogeneous. The reactor was sealed, and nitrogen gas was introduced to purge air and dissolved oxygen from the system. Under magnetic stirring, the pressure inside the subcritical high-pressure reactor was controlled at 0.1 MPa by operating a manual pump, and the temperature inside the reactor was controlled at 160℃ by the control panel and temperature measuring wire. After maintaining the reaction for 120 min, the mixture was centrifuged. The obtained solid was washed three times with ultrapure water and anhydrous ethanol to remove residual salts, and then vacuum dried in an oven at 60℃ to obtain the ZnIn2S4 catalyst.

[0054] The XRD pattern of the ZnIn2S4 catalyst prepared in Example 5 shows that the method of the present invention successfully prepared the ZnIn2S4 catalyst (e.g. Figure 5 (a)); SEM images show that the ZnIn2S4 prepared by the method of the present invention has a hexagonal flower-like microsphere structure, with uniform particle size and no agglomeration between particles (e.g. Figure 5 In (b) of the image, the TEM image shows that the microspheres are self-assembled from nanosheets on the core (e.g., Figure 5 (c) in the middle.

[0055] The ZnIn2S4 sample prepared in Example 5 was used for photocatalytic degradation of sulfamethoxazole (SMX). The specific process is as follows:

[0056] The photocatalytic degradation of SMX under room temperature visible light (λ>420 nm) irradiation was conducted in a quartz reactor. The light source was a 300W Xe lamp with a cutoff filter of 420 nm. 10 mg of the ZnIn2S4 photocatalyst prepared in Example 5 was added to 50 mL of a reaction solution containing SMX (1.5 mg / L). The prepared reaction mixture was sonicated for 1 min, and the initial pH was adjusted to within ± 0.2 using NaOH (0.5 M) and H2SO4 (0.25 M). The quartz reactor was placed on a magnetic stirrer and stirred for 30 min to allow the SMX and photocatalyst to reach adsorption-desorption equilibrium, followed by irradiation for the reaction.

[0057] Experiments show that when the reaction time is 60 min, the efficiency of ZnIn2S4 photocatalytic degradation of SMX can reach 61.2% (see Table 2).

[0058] Example 6: The multi-metal nano-microstructure catalyst ZnIn2S4 was synthesized using a subcritical technique, and the steps are as follows:

[0059] 0.068 g ZnCl2 and 0.293 g InCl3·4H2O were dissolved in 20 mL of ultrapure water and sonicated until homogeneous. 0.15 g thioacetamide was then dissolved in 20 mL of ultrapure water. The two solutions were mixed to obtain a mixture. After sonication, the mixture was transferred to a subcritical high-pressure reactor. 0.360 g NaOH was then dispersed in another 40 mL of ultrapure water to obtain an alkaline solution. The alkaline solution was slowly added dropwise to the above citric acid chelate metal mixture and stirred until homogeneous. The reactor was sealed, and oxygen was introduced to purge air from the system. Under magnetic stirring, the pressure inside the subcritical high-pressure reactor was controlled at 0.1 MPa by operating a manual pump, and the temperature was controlled at 160℃ by the control panel and temperature measuring wire. After maintaining the reaction for 120 min, the mixture was centrifuged. The resulting solid was washed three times with ultrapure water and anhydrous ethanol to remove residual salts, and then vacuum dried at 60℃ in an oven to obtain the ZnIn2S4 catalyst.

[0060] Comparative Example 2: Preparation of ZnIn2S4 by hydrothermal method, the steps are as follows:

[0061] 0.068 g ZnCl2 and 0.293 g InCl3·4H2O were dissolved in 20 mL of ultrapure water and sonicated until homogeneous. 0.15 g thioacetamide was then dissolved in 20 mL of ultrapure water. The two solutions were mixed to obtain a mixture, which was then sonicated and transferred to a reaction vessel. 0.360 g NaOH was dispersed in another 40 mL of ultrapure water to obtain an alkaline solution. This alkaline solution was slowly added dropwise to the citric acid-chelated metal mixture, and after thorough mixing, it was transferred to a 50 mL stainless steel autoclave lined with polytetrafluoroethylene. The autoclave was then sealed and heated in an oven at 160 °C for 16 h. After the autoclave cooled naturally to room temperature, the prepared ZnIn2S4 was collected and washed three times with deionized water and anhydrous ethanol. The collected powder was dried overnight in a vacuum oven at 60 °C to obtain the ZnIn2S4 catalyst.

[0062] The SEM image of Example 5 shows that the ZnIn2S4 prepared by the method of the present invention has a hexagonal flower-like microsphere structure, with uniform particle size and no agglomeration between particles (e.g., Figure 5 (b) in Example 6; SEM image (e.g.) Figure 7 (a) shows that the ZnIn2S4 prepared by the method of the present invention has a hexagonal flower-like microsphere structure, but compared with... Figure 5 Compared to (b), its petals are smaller and some particles are agglomerated; the SEM image of the ZnIn2S4 catalyst prepared in Comparative Example 2 shows that the ZnIn2S4 prepared by the method described in Comparative Example 2 has a hexagonal flower-like microsphere structure, but the petals are smaller and there is agglomeration between particles (see Figure 7 (b) in the middle);

[0063] SEM images of ZnIn2S4 prepared in Examples 5 and 6 (e.g.) Figure 5 (b) and Figure 7 The comparison in (a) shows that the atmosphere introduced during the preparation of spinel-type sulfides differs. In Example 5, nitrogen was introduced, while in Example 6, oxygen was introduced. Introducing nitrogen resulted in more uniform particles compared to introducing oxygen. This is because when the catalyst is a spinel-type sulfide, the sulfide is easily oxidized if oxygen is introduced. Nitrogen, being an inert gas, can expel air and moisture from the apparatus, providing a stable protective environment and preventing oxidation or contamination of the material during preparation, thus ensuring the high purity and performance of the nanomaterials. Therefore, if the desired substance is a spinel-type sulfide, the catalyst particles prepared by introducing nitrogen will be more uniform.

[0064] The ZnIn2S4 sample prepared in Comparative Example 2 was used for photocatalytic degradation of sulfamethoxazole (SMX). The specific process is as follows:

[0065] The photocatalytic degradation of SMX under room temperature visible light (λ>420 nm) irradiation was carried out in a quartz reactor. The light source was a 300W Xe lamp with a cutoff filter of 420 nm. 10 mg of the ZnIn2S4 photocatalyst prepared in Comparative Example 2 was added to 50 mL of a reaction solution containing SMX (1.5 mg / L). The prepared reaction mixture was sonicated for 1 min, and the initial pH was adjusted to within ± 0.2 using NaOH (0.5 M) and H2SO4 (0.25 M). The quartz reactor was placed on a magnetic stirrer and stirred for 30 min to allow the SMX and photocatalyst to reach adsorption-desorption equilibrium, followed by photocatalysis to carry out the reaction.

[0066] Experiments show that when the reaction time is 60 min, the ZnIn2S4 catalyst prepared by this invention can photocatalytically degrade SMX, and its photocatalytic degradation efficiency of SMX is higher than that of the ZnIn2S4 catalyst prepared by the hydrothermal method, as shown in Table 2.

[0067] Table 2 Catalytic effects of ZnIn2S4 catalysts prepared by different methods

[0068]

[0069] The contents described in this specification are merely an enumeration of the implementation forms of the inventive concept, and the scope of protection of this invention should not be regarded as limited to the specific forms described in the embodiments.

Claims

1. A method for synthesizing spinel-type nanomaterials based on subcritical technology, characterized in that, Includes the following steps: 1) Dissolve various metal salts in ultrapure water, sonicate them evenly, and set aside. Then weigh out organic additives and dissolve them in ultrapure water. Mix the solutions to obtain a mixture, and transfer it to a subcritical high-pressure reactor after sonication. 2) Disperse the alkaline additive in ultrapure water to obtain an alkaline solution. Add the alkaline solution dropwise to the mixture obtained in step 1) and stir to mix evenly. Seal the reactor and introduce gas. The subcritical high-pressure reactor is equipped with an external temperature and pressure control device. Under magnetic stirring, the temperature and pressure inside the subcritical high-pressure reactor are precisely controlled by heating and pressurizing devices and maintained for 30~180 min to form a subcritical fluid inside the subcritical high-pressure reactor. 3) After the reaction is complete, the solution prepared in step 2) is centrifuged, washed with ultrapure water and anhydrous ethanol to remove residual salts, and dried in an oven overnight to obtain spinel-type nanomaterials; In step 1), the metal salt is a nitrate or chloride of aluminum, cobalt, manganese, zinc, bismuth, indium, or iron; In step 1), the organic additive is citric acid, thioacetamide, hexadecyltrimethylammonium bromide, or urea; In step 2), the temperature is controlled at 160~180℃ and the pressure is controlled at 0.1MPa. When the prepared spinel-type nanomaterial is a sulfide catalyst, nitrogen is used, and when the prepared spinel-type nanomaterial is an oxidation catalyst, oxygen is used.

2. The method for synthesizing spinel-type nanomaterials based on subcritical technology as described in claim 1, characterized in that, The molar ratio of total metal atoms in the metal salt solution to the amount of organic additives is 1:0.8~5.

3. The method for synthesizing spinel-type nanomaterials based on subcritical technology as described in claim 1, characterized in that, In step 2), the alkaline additive is sodium hydroxide, ammonia, carbonate or bicarbonate, and the molar ratio of the alkaline additive dosage in the alkaline solution to the total metal atoms in the metal salt solution is 2~8:1.

Images