Preparation method of nitrogen-doped biochar-loaded iron nitride composite material

Abstract

The present invention relates to the technical field of nanopowder preparation, and discloses a method for preparing a nitrogen-doped biochar-loaded iron nitride composite material. The process is as follows: (1) potassium ferrate, urea, and waste tea powder are ground and mixed in proportion to obtain a first mixture; (2) the first mixture is reacted in a temperature range of 50-70°C to obtain a second mixture; (3) the second mixture is reacted in a temperature range of 600-800°C for 1-3 hours, and then cooled to room temperature to obtain a third mixture; (4) the third mixture is washed and dried to obtain a nitrogen-doped biochar-loaded iron nitride composite material. Compared with the existing preparation process, the beneficial effect of the present invention is that the operation steps only include grinding, stirring, heating, etc., the operation is simpler, the overall process only involves one pyrolysis, the energy consumption is lower, and the toxic gas ammonia is not used, and the operation is safer. The material can degrade trichloroethylene without an anaerobic environment and can be used for the remediation of organochlorine-contaminated groundwater environment.

Description

Technical Field

[0001] The present invention relates to the technical field of nano powder preparation, and in particular to a method for preparing a nitrogen-doped biochar-loaded iron nitride composite material. Background Art

[0002] Trichloroethlene (TCE) is a typical organic halogenated pollutant in underground industrial environments, exhibiting high biotoxicity. Given its strong chemical stability and migration capacity, effective remediation and complete mineralization of TCE in groundwater are urgently needed. Nanoscale zero-valent iron (ZVI) in-situ reduction treatment technology holds great promise, but untreated ZVI suffers from drawbacks such as low electron selectivity, easy aggregation, short lifespan, and poor overall performance.

[0003] In recent years, studies have found that nano-zero-valent iron can be nitrided to obtain nano-iron nitride, and then the nano-iron nitride can be loaded on carbon materials such as biochar to finally obtain a biochar-loaded iron nitride composite material. This type of composite material has the advantages of being less susceptible to corrosion in water, having a long service life, high stability, and being able to quickly dechlorinate TCE. For example, patent application number 202210145314.5 discloses a nitrogen-doped zero-valent iron nanomaterial, a preparation method, and an application. This method uses gelatin and ferrous acetate as nitrogen sources and iron sources, respectively, and synthesizes nitrogen-doped zero-valent iron nanomaterials by dissolving, mixing, stirring, drying, grinding, and high-temperature firing. However, this patent has the following defects: 1. The preparation process is complicated and includes multiple steps such as stirring, ultrasound, and pyrolysis. 2. When degrading TCE, the reaction vessel needs to be vacuumed and anaerobic water needs to be used during the reaction process. The operating conditions are harsh, which is not conducive to the promotion and use of the product in actual working conditions. For example, patent application number 201410785030.8 discloses a method for preparing nano-iron nitride. This method uses ferric nitrate and amine organic matter as iron and nitrogen sources, and synthesizes nano-iron nitride by dissolving, heating, concentrating, and drying. However, this patent has the following defects: toxic gas ammonia must be continuously introduced during the heating and concentration stage, posing a safety hazard during the operation.

[0004] In view of this, the present invention aims to provide a nitrogen-doped biochar-loaded iron nitride composite material (Fe x The preparation method of N / NBC (N / NBC) is based on the selection of appropriate iron, carbon, and nitrogen source precursors. Through simple operation, nitrogen-doped biochar-loaded iron nitride composite materials can be obtained through a one-step pyrolysis at a low temperature (minimum 600°C), without the use of toxic ammonia. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a preparation method of a nitrogen-doped biochar-loaded iron nitride composite material with simple operation, safer preparation process and lower energy consumption and its application.

[0006] The present invention is achieved through the following technical solutions.

[0007] In a first aspect, the present invention provides a method for preparing a nitrogen-doped biochar-loaded iron nitride composite material, characterized in that it comprises the following steps:

[0008] S1. Potassium ferrate, urea and waste tea powder are placed in a mortar in proportion and ground until thoroughly mixed to obtain a first mixture;

[0009] S2. The first mixture is reacted in a protective gas atmosphere at a temperature range of 50 to 70 ° C to obtain a second mixture;

[0010] S3. The second mixture is reacted in a protective gas atmosphere at a temperature range of 600 to 800 ° C for 1 to 3 hours, and then cooled to room temperature to obtain a third mixture;

[0011] S4. Washing and drying the third mixture to obtain the composite material.

[0012] Compared to other preparation methods, the method of the present invention involves only simpler steps, such as grinding, heating, washing, and drying, and only involves a single pyrolysis step, resulting in lower energy consumption. The method of the present invention also avoids the presence of toxic ammonia, making the overall process safer.

[0013] As a further improvement of the present invention, the waste tea powder is prepared by washing and drying the waste tea leaves after brewing tea, then crushing and sieving through a 50-mesh test sieve to obtain the waste tea powder. The present invention uses treated waste tea powder as a carrier, making the material readily available and easy to handle, reducing the cost of preparing the composite material and facilitating its widespread use. Sieving through a 50-mesh test sieve produces a smaller particle size of waste tea powder, which facilitates its full contact with the remaining raw materials during mixing, resulting in a more uniform mixing.

[0014] As a further improvement of the present invention, the mass ratio of potassium ferrate, urea, and waste tea powder in S1 is 1:2:2. The composite material prepared at this ratio has a more uniform iron nitride phase and is less likely to produce impurities such as iron oxide.

[0015] As a further improvement of the present invention, inert gas is introduced into S2 and S3 to provide a protective atmosphere. Drying in an inert gas atmosphere can achieve the effect of dehumidification and deoxygenation, preventing potassium ferrate from reacting with water under high temperature conditions, which could result in the formation of iron oxide impurities in the final product. Furthermore, the use of inert gas makes the operation process safer.

[0016] As a further improvement of the present invention, nitrogen is injected into S2 and S3 to provide a protective gas atmosphere. Drying in a nitrogen atmosphere can also achieve the effect of dehumidification and deoxygenation.

[0017] As a further improvement of the present invention, deionized water is used to wash the mixture in S4 to prevent contamination of the third mixture. Since the composite material uses waste tea powder as a carrier, drying in a vacuum environment at 60°C for 10 hours can achieve a drying effect while preventing the material from being damaged by high temperature.

[0018] As a further improvement of the present invention, the reaction time of the first mixture in S2 is 100 minutes.

[0019] As a further improvement of the present invention, a heating rate of 6-8°C / min is used to reach the reaction temperature in S2 and S3.

[0020] In a second aspect, the present invention provides a nitrogen-doped biochar-loaded iron nitride composite material prepared by the above method.

[0021] Thirdly, the present invention provides an application of a nitrogen-doped biochar-loaded iron nitride composite material. This composite material can be used to denitrify trichloroethylene, achieving a 90% TCE removal rate after just two hours. This efficiency is significantly higher than other products, such as untreated commercially available nano-zero-valent iron (nZVI). Furthermore, the removal reaction does not require an anaerobic environment; it only requires the presence of light. This high removal efficiency and low reaction requirements broaden the product's application scenarios and facilitate its widespread adoption in practical applications.

[0022] Therefore, the present invention has the following beneficial effects:

[0023] 1. The preparation process is simple and easy to operate, which is conducive to the production of composite materials. At the same time, the overall process only involves one pyrolysis, which has relatively lower energy consumption and is more environmentally friendly.

[0024] 2. The preparation process does not involve toxic gas ammonia, and the overall process is safer;

[0025] 3. Using waste tea powder made from waste tea leaves as the iron nitride carrier reduces the production cost of the composite material and is conducive to the promotion and application of the composite material;

[0026] 4. It can achieve efficient denitrification of trichloroethylene and has low requirements for the working environment, which is conducive to promoting the use of composite materials in actual scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings to help understand the objects and advantages of the present invention, wherein:

[0028] Figure 1 Fe was obtained at a drying temperature of 60°C and a reaction temperature of 600°C. x X-ray diffraction (XRD) results of N / NBC composite materials;

[0029] Figure 2 Fe was obtained at a drying temperature of 60°C and a reaction temperature of 600°C. x Scanning Electron Microscope (SEM) test results of the N / NBC composite material;

[0030] Figure 3 Fe was obtained at a drying temperature of 60°C and a reaction temperature of 600°C. x Local SEM results of N / NBC composite material;

[0031] Figure 4 Fe was obtained at a drying temperature of 60°C and a reaction temperature of 600°C. x Energy dispersive spectroscopy (EDS) results of the entire N / NBC composite material;

[0032] Figure 5 Fe was obtained at a drying temperature of 60°C and a reaction temperature of 600°C. x EDS results of carbon elements in N / NBC composite materials;

[0033] Figure 6 Fe was obtained at a drying temperature of 60°C and a reaction temperature of 600°C. x EDS results of nitrogen in N / NBC composite materials;

[0034] Figure 7 Fe was obtained at a drying temperature of 60°C and a reaction temperature of 600°C. x EDS results of oxygen elements in N / NBC composite materials;

[0035] Figure 8 Fe was obtained at a drying temperature of 60°C and a reaction temperature of 600°C. xEDS results of iron element in N / NBC composite material;

[0036] Figure 9 Fe was obtained at a drying temperature of 60°C and a reaction temperature of 600°C. x Fourier Transform Infrared Spectroscopy (FT-IR) test results of N / NBC composite materials;

[0037] Figure 10 Fe was obtained at a drying temperature of 50°C and a reaction temperature of 700°C. x XRD results of N / NBC composite materials;

[0038] Figure 11 Fe was obtained at a drying temperature of 70°C and a reaction temperature of 800°C. x XRD results of N / NBC composite materials;

[0039] Figure 12 Nano-zero-valent iron (nZVI), Fe x N material, NBC material and Fe prepared at 60℃ drying temperature and 600℃ reaction temperature x Removal kinetics curve of TCE by N / NBC composite material. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to illustrate the present invention, rather than to represent all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without creative work are within the scope of protection of the present invention.

[0041] Example 1:

[0042] S1. Take the spent tea leaves after brewing tea, wash and dry them, then crush them, and finally sieve them using a 50-mesh test sieve to obtain spent tea powder.

[0043] S2. Weigh potassium ferrate, urea, and waste tea powder in a mass ratio of 1:2:2 and grind them until they are fully mixed to obtain a first mixture.

[0044] In step S3, the first mixture is placed in a tube furnace, nitrogen is introduced into the furnace, the temperature in the furnace is raised to 60°C at a heating rate of 7°C / min, and the reaction is carried out at this temperature for 100 minutes to dehumidify and deoxygenate the first mixture, thereby obtaining a second mixture.

[0045] S4. The second mixture is retained in the tube furnace, and the temperature in the furnace is raised to 600°C at a heating rate of 7°C / min, and reacted at this temperature for 2 hours to obtain a third mixture.

[0046] S5. When the reaction time is up, heating is stopped. After the third mixture is cooled to room temperature, the third mixture is washed with deionized water and then dried under vacuum at 60°C for 10 hours to obtain a Fe3N / NBC composite material.

[0047] The XRD results of the Fe3N / NBC composite material are shown in Figure 2. Figure 1 As shown in Figure 2, the iron nitride phase obtained under this condition is more uniform; the SEM results of the Fe3N / NBC composite material are shown in Figure 2. Figure 2 and Figure 3 As shown by Figure 2 It can be seen that the waste tea powder in the composite material has a rich surface wrinkle structure, that is, a large surface area. Figure 3 It can be seen that most of the iron nitride particles loaded on the waste tea powder have a particle size between 10 and 50 nanometers, and some can reach about 100 nanometers. In addition, there is basically no agglomeration of the iron nitride particles, and they are evenly distributed on the surface of the waste tea powder. x EDS results of N / NBC composite material as a whole and each element, namely Figures 4 to 8 It can be seen that Fe3N / NBC composite materials contain Fe, C, N, O and other elements, among which N element is widely and evenly distributed. Combined with the FT-IR results of Fe3N / NBC composite materials Figure 9 The presence of CN functional groups in the sample indicates that the waste tea powder also contains N elements.

[0048] Example 2:

[0049] S1. Take the spent tea leaves after brewing tea, wash and dry them, then crush them, and finally sieve them using a 50-mesh test sieve to obtain spent tea powder.

[0050] S2. Weigh potassium ferrate, urea, and waste tea powder in a mass ratio of 1:2:2 and grind them until they are fully mixed to obtain a first mixture.

[0051] In step S3, the first mixture is placed in a tube furnace, argon gas is introduced into the furnace, the temperature in the furnace is raised to 60°C at a heating rate of 7°C / min, and the reaction is carried out at this temperature for 100 minutes to dehumidify and deoxygenate the first mixture, thereby obtaining a second mixture.

[0052] S4. The second mixture is retained in the tube furnace, and the temperature in the furnace is raised to 600°C at a heating rate of 7°C / min, and reacted at this temperature for 2 hours to obtain a third mixture.

[0053] S5. When the reaction time is up, heating is stopped. After the third mixture is cooled to room temperature, deionized water is used to wash the third mixture, and the mixture is dried under vacuum at 60° C. for 10 hours to obtain a Fe3N / NBC composite material.

[0054] The obtained product is basically the same as that in Example 1. During the operation, the method of filling inert gas argon to form a protective gas atmosphere is adopted to make the overall process safer.

[0055] Example 3:

[0056] S1. Take the spent tea leaves after brewing tea, wash and dry them, then crush them, and finally sieve them using a 50-mesh test sieve to obtain spent tea powder.

[0057] S2. Weigh potassium ferrate, urea, and waste tea powder in a mass ratio of 1:2:2 and grind them until they are fully mixed to obtain a first mixture.

[0058] In step S3, the first mixture is placed in a tube furnace, nitrogen is introduced into the furnace, the temperature in the furnace is raised to 50°C at a heating rate of 6°C / min, and the mixture is reacted at this temperature for 100 minutes to dehumidify and deoxygenate the first mixture, thereby obtaining a second mixture.

[0059] S4. The second mixture is retained in the tube furnace, and the temperature in the furnace is raised to 700°C at a heating rate of 6°C / min, and reacted at this temperature for 1 hour to obtain a third mixture.

[0060] S5. When the reaction time is up, heating is stopped, and after the third mixture is cooled to room temperature, deionized water is selected to wash the third mixture, and the mixture is dried under vacuum at 60 ° C for 10 hours to obtain Fe x N / NBC composite material.

[0061] Fe x The XRD results of N / NBC composite materials are shown in the figure Figure 10 As shown in the figure, the iron nitride phase composition is more complex, but it still has a good removal effect on TCE.

[0062] Example 4:

[0063] S1. Take the spent tea leaves after brewing tea, wash and dry them, then crush them, and finally sieve them using a 50-mesh test sieve to obtain spent tea powder.

[0064] S2. Weigh potassium ferrate, urea, and waste tea powder in a mass ratio of 1:2:2 and grind them until they are fully mixed to obtain a first mixture.

[0065] S3: Place the first mixture in a tube furnace, introduce nitrogen into the furnace, raise the temperature in the furnace to 70°C at a heating rate of 8°C / min, and react at this temperature for 100 minutes to dehumidify and deoxygenate the first mixture, thereby obtaining a second mixture.

[0066] S4. The second mixture is retained in the tube furnace, and the temperature in the furnace is raised to 800°C at a heating rate of 8°C / min, and reacted at this temperature for 3 hours to obtain a third mixture.

[0067] S5. When the reaction time is up, heating is stopped, and after the third mixture is cooled to room temperature, deionized water is selected to wash the third mixture, and the mixture is dried under vacuum at 60 ° C for 10 hours to obtain Fe x N / NBC composite material.

[0068] Fe x The XRD results of N / NBC composite materials are shown in the figure Figure 11 As shown in the figure, the iron nitride phase composition is more complex, but it still has a good removal effect on TCE.

[0069] Example 5:

[0070] S1. Potassium ferrate and urea were weighed in a mass ratio of 1:2 and ground until fully mixed to obtain a first mixture. The remaining reaction steps were the same as in Example 1 to finally obtain Fe x N material; urea and waste tea powder were weighed in a mass ratio of 1:1 and ground until fully mixed to obtain a second mixture. The remaining reaction steps were the same as in Example 1 to finally obtain NBC material.

[0071] S2. At room temperature, 20 mg of degradation material, namely the Fe x N / NBC composite materials, commercially available nano-zero-valent iron (nZVI), Fe prepared in S1 x The N material and the NBC material prepared in S1 were placed in four brown conical flasks with lids, and 20 mL of deionized water was added to each flask.

[0072] S3. Inject 37 μL of 10.8 g / L TCE liquid into each of the four conical flasks so that the initial TCE concentration in the conical flasks is 20 mg / L.

[0073] S4. Add a stirring magnet to each of the four Erlenmeyer flasks and begin the stirring reaction. At 30, 60, and 120 minutes, remove 4 mL of water from each Erlenmeyer flask. Filter each sample through a 0.22 μm filter and add it to a headspace vial containing 1 g / L sodium chloride. Measure the TCE concentration in the water samples using headspace gas chromatography-mass spectrometry.

[0074] The removal kinetics curves of TCE by each degradation material in Example 5 are shown in FIG. Figure 12 As shown. x The N / NBC composite material can degrade TCE relatively quickly. When the reaction is carried out for 2 hours, Fe x The removal rate of TCE by N / NBC composite material can reach 90%.

[0075] Finally, it should be noted that the above implementation cases are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above implementation cases, ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the above implementation cases, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the implementation cases of the present invention.

Claims

1. A method for preparing a nitrogen-doped biochar-loaded iron nitride composite material, characterized in that: The steps include: S1. Potassium ferrate, urea, and waste tea powder are placed in a mortar at a mass ratio of 1:2:2 and ground until thoroughly mixed to obtain a first mixture; S2. The first mixture was reacted in a protective gas atmosphere at a temperature range of 50 to 70 ° C for 100 minutes to obtain a second mixture; S3. The second mixture is reacted in a protective gas atmosphere at a temperature range of 600 to 800 ° C for 1 to 3 hours, and then cooled to room temperature to obtain a third mixture; S4. Washing and drying the third mixture to obtain the composite material.

2. The method for preparing the nitrogen-doped biochar-loaded iron nitride composite material according to claim 1, characterized in that: The waste tea powder is prepared by the following method: The waste tea leaves after brewing tea are washed and dried, then crushed and sieved through a 50-mesh inspection sieve to obtain waste tea powder.

3. The method for preparing the nitrogen-doped biochar-loaded iron nitride composite material according to claim 2, characterized in that: In said S2 and S3, a protective gas atmosphere is provided by filling inert gas.

4. The method for preparing the nitrogen-doped biochar-loaded iron nitride composite material according to claim 2, characterized in that: The protective gas atmosphere is provided by filling nitrogen in S2 and S3.

5. The method for preparing the nitrogen-doped biochar-loaded iron nitride composite material according to claim 2, characterized in that: In S4, the mixture is washed with deionized water, and then dried under a vacuum environment at 60° C. for 10 hours.

6. The method for preparing the nitrogen-doped biochar-loaded iron nitride composite material according to claim 2, characterized in that: The reaction temperature in S2 and S3 was reached using a heating rate of 6-8°C / min.

7. A nitrogen-doped biochar-loaded iron nitride composite material, characterized by: The method is prepared by any one of claims 1 to 6.

8. An application of the nitrogen-doped biochar-loaded iron nitride composite material according to claim 7, characterized in that: The nitrogen-doped biochar-loaded iron nitride composite material can achieve dechlorination of trichloroethylene without being in an anaerobic environment.

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