Fe-n single-atom catalyst supported by thin carbon net of sugarcane pith, and preparation method and application thereof

Abstract

The present application relates to a kind of Fe-N single-atom catalysts of sugarcane pith thin carbon net load and its method preparation and application, belong to catalyst technical field, the present application uses sugarcane pith as carbon source, realizes the plasmolysis of sugarcane pith cell and the anchoring of iron by two-step hydrothermal reaction, and finally obtains a kind of Fe-N single-atom catalysts of sugarcane pith thin carbon net load, the catalyst obtained, iron is loaded in the coordination structure of Fe-N-C in sugarcane pith thin carbon net, the catalyst obtained has good photocatalytic decomposition effect to tetracycline antibiotics, not only provides new insight for the exploration of single-atom catalyst photodegradation phenolic substance, simultaneously realizes the high value utilization of sugarcane pith.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts, and in particular relates to a sugarcane pith thin carbon mesh loaded Fe-N single atom catalyst and a preparation method and application thereof. Background Art

[0002] Tetracycline antibiotics are produced and used in large quantities in my country, and lack corresponding emission standards. High concentrations of tetracycline antibiotics have certain lethal and sublethal effects on organisms in the aquatic environment, seriously affecting the normal growth of aquatic organisms. Fenton-like catalytic oxidation technology and photocatalytic technology based on PMS are increasingly being explored. Traditional catalysts for the degradation of antibiotics mainly use metals, metal oxides, metal-organic frameworks and other materials as carriers, and load metal nanoparticles and dissolved metal ions as active ingredients. However, traditional catalysts for the degradation of antibiotics have problems such as high metal loading, high cost, and low metal utilization.

[0003] Sugarcane is my country's primary sugar crop. Bagasse, the residue left after sugar extraction and crushing, is one of the country's largest agricultural waste streams. Approximately 50% of the fiber in the bagasse left after sugar extraction can be used to make paper. However, some of the pith lacks interwoven strength and is removed before pulping. This pith, the residue remaining after sugar production and pulping and papermaking, accounts for approximately 30% of the bagasse. Currently, pith is primarily burned as fuel to recover heat, resulting in low utilization rates and economic added value, leading to a waste of resources. Summary of the Invention

[0004] In view of the problems existing in the background technology, the inventors are committed to proposing a low-cost catalyst loaded with metal active ingredients, and finally obtained a sugarcane pith thin carbon network loaded Fe-N single atom catalyst. In the obtained catalyst, iron is loaded in the sugarcane pith thin carbon network in the form of Fe-NC coordination structure. The obtained catalyst has a good photocatalytic decomposition effect on tetracycline antibiotics, which not only provides new insights into the exploration of single-atom catalysts for the photodegradation of phenolic substances, but also provides a new idea for the resource utilization of sugarcane pith.

[0005] To achieve the above objectives, the present invention provides a sugarcane pith thin carbon mesh supported Fe-N single atom catalyst and a preparation method and application thereof.

[0006] The sugarcane pith thin carbon mesh loaded Fe-N single atom catalyst has single atom iron as an active component and the carrier is the sugarcane pith thin carbon mesh.

[0007] The method for preparing the sugarcane pith thin carbon mesh-supported Fe-N single-atom catalyst comprises the following steps:

[0008] (1) Immerse the sugarcane pith particles in a mixture of FeCl3 in ethanol and hydrochloric acid and seal them under pressure;

[0009] (2) washing and drying the reactant obtained in step (1);

[0010] (3) adding the dried product obtained in step (2) to a urea solution for reaction;

[0011] (4) heating the reaction product of step (3) under an inert atmosphere for carbonization;

[0012] (5) The carbonized product of step (4) is crushed to obtain a sugarcane pith thin carbon network loaded Fe-N single atom catalyst.

[0013] Furthermore, in step (1), the sugarcane pith particles have a particle size of 20-100 mesh.

[0014] Furthermore, in step (1), the mass ratio of sugarcane pith to FeCl3 is 1:4~3:13.5; the volume ratio of ethanol to hydrochloric acid is 4~9:1, the concentration of the ethanol / hydrochloric acid solution of FeCl3 is 0.05~0.5mol / L, and the concentration of hydrochloric acid is 1mol / L~6mol / L.

[0015] Furthermore, the reaction temperature of step (1) is 120-140° C., and the reaction time is 2-4 h.

[0016] Furthermore, the drying in step (2) refers to evaporating the water in the reactants after centrifugation.

[0017] Furthermore, in step (3), the mass ratio of sugarcane pith to urea is 1:4-6; the reaction temperature is 80-100°C, and the reaction time is 12-24h.

[0018] Furthermore, the carbonization temperature of step (4) is 600-800°C, and the carbonization time is 2-4 hours.

[0019] The sugarcane pith thin carbon mesh loaded Fe-N single atom catalyst prepared by any of the above methods all fall within the protection scope of the present invention.

[0020] The invention discloses an application of the sugarcane pith thin carbon mesh loaded Fe-N single atom catalyst in the degradation of tetracycline antibiotics.

[0021] Beneficial effects of the present invention:

[0022] The preparation method of the present invention realizes plasmolysis of sugarcane pith cells and anchoring of iron through two hydrothermal reactions, anchoring single Fe atoms on a thin carbon network of sugarcane pith to form an iron single-atom catalyst (Fe-SAC). In the obtained catalyst, iron is loaded in the thin carbon network of sugarcane pith in the form of single atoms. The obtained catalyst can degrade tetracycline antibiotics under simulated light conditions, which is a new application of single-atom catalysts for photodegradation of phenolic substances and provides a new idea for the resource utilization of sugarcane pith. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is an XRD comparison diagram of the sugarcane pith thin carbon mesh supported Fe-N single atom catalyst of the present invention and other catalysts;

[0024] Figure 2 TEM image of the sugarcane pith thin carbon mesh supported Fe-N single atom catalyst obtained in Example 1 of the present invention;

[0025] Figure 3 Energy dispersive X-ray spectroscopy (EDS) of the sugarcane pith thin carbon mesh supported Fe-N single atom catalyst of Example 1 of the present invention;

[0026] Figure 4 This is a high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM-100nm) image of the sugarcane pith thin carbon mesh supported Fe-N single atom catalyst according to Example 1 of the present invention;

[0027] Figure 5 This is a high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM-5nm) image of the sugarcane pith thin carbon mesh supported Fe-N single atom catalyst of Example 1 of the present invention;

[0028] Figure 6 This is a comparison chart of the dark adsorption and photocatalytic degradation of tetracycline by the catalysts obtained in Comparative Examples 1-4 of the present invention;

[0029] Figure 7 1 is a comparison chart of the adsorption effects of the catalysts obtained in Example 1 of the present invention and Comparative Example 4 on tetracycline;

[0030] Remark: Figure 5 The middle circle contains monatomic iron;

[0031] In all the figures, C represents pure sugarcane pith carbon catalyst, CN represents nitrogen (urea) doped sugarcane pith carbon catalyst, Fe-C represents sugarcane pith supported ferric chloride catalyst; Fe-SAC represents sugarcane pith fiber nano-mesh carbon layer supported Fe-N catalyst. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and beneficial effects of the present invention more clear, the technical solution of the present invention will be described in detail below. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without making creative efforts shall fall within the scope of protection of the present invention.

[0033] A method for preparing a sugarcane pith thin carbon mesh-supported Fe-N single-atom catalyst comprises the following steps:

[0034] (1) Primary hydrothermal reaction

[0035] Immerse 20-100 mesh sugarcane pith particles in a mixture of FeCl3 and ethanol / hydrochloric acid. Allow the pith and ethanol / hydrochloric acid solution to fully mix at room temperature for 2-4 hours. This enhances the hydrochloric acid's ability to decompose the pith cell walls during the high-temperature, high-pressure hydrothermal reaction. The mass ratio of pith to FeCl3 is 1:4 to 3:13.5; the volume ratio of ethanol to hydrochloric acid is 4:1 to 9:1; the concentration of the FeCl3 / ethanol / hydrochloric acid solution is 0.05-0.5 mol / L, and the concentration of the hydrochloric acid is 1-6 mol / L.

[0036] The reaction in this step was carried out in a polytetrafluoroethylene-lined stainless steel autoclave. After standing, the autoclave was sealed and placed in an oven at 140°C so that the absolute temperature in the autoclave reached 413.15 Kelvin. After heating for 2 h, it was naturally cooled to room temperature.

[0037] In this hydrothermal reaction, the cellulose and hemicellulose in the sugarcane pith cell wall are hydrolyzed and separated, and the sugarcane pith cells form a plasmolysis state, which makes Fe 3+ It can more easily enter sugarcane medullary cells, providing a large amount of Fe 3+ Provides chelation sites.

[0038] (2) Washing and drying

[0039] The reactant obtained in step (1) is washed and dried.

[0040] Washing is done by centrifugation, and ethanol or water can be used for washing until the supernatant is colorless. 3+ is removed to avoid the subsequent agglomeration of Fe nanoparticles during high-temperature carbonization.

[0041] (3) Secondary hydrothermal reaction

[0042] The dried product obtained in step (2) is added to a urea solution for reaction, wherein the mass ratio of sugarcane pith to urea is 1:4 to 1:6; the reaction temperature is 80 to 100°C, and the reaction time is 12 to 24 hours.

[0043] In this hydrothermal reaction, urea provides sufficient nitrogen source to enable the formation of a stable Fe-NC structure after subsequent high-temperature carbonization. The single-atom Fe active sites can be effectively increased. The single Fe atom in the carbon support is the active center of the catalyst. The introduction of single Fe atoms can significantly improve the electron transfer ability and chemical reaction activity of the carbon support.

[0044] (4) Carbonization

[0045] The reaction product of step (3) is heated and carbonized under an inert atmosphere.

[0046] Carbonization temperature is 600~800℃, and carbonization time is 2~4h.

[0047] Sugarcane pith is composed of numerous fiber bundles interwoven into a network, forming a complex fibrous web. The pith cell wall is characterized by its primary composition of cellulose, hemicellulose, and lignin, giving it high strength and toughness. Using sugarcane pith as a carbon support, its high surface area, tunable pore structure, and excellent thermal stability facilitate the chelation of single Fe atoms and their formation of an Fe-NC coordination structure with an external nitrogen source (urea). Ultimately, after two hydrothermal reactions, the Fe atoms are anchored on the thin pith carbon network, forming an iron single-atom catalyst.

[0048] (5) Crushing or grinding

[0049] The carbonized product of step (4) is fully ground to obtain a sugarcane pith thin carbon network loaded Fe-N single atom catalyst (Fe-SAC).

[0050] The invention mainly utilizes agricultural waste sugarcane pith as raw material, has simple process operation, and is green and environmentally friendly in preparation method. It also realizes efficient degradation of tetracycline antibiotics under simulated light and efficient utilization of renewable resource waste.

[0051] In order to illustrate the present invention more clearly, the following examples are provided for detailed description. Example 1

[0052] The preparation method of sugarcane pith thin carbon mesh supported Fe-N single atom catalyst comprises the following steps:

[0053] (1) Primary hydrothermal reaction: The crushed sugarcane pith was further sieved into 20-100 mesh. 3 g of sugarcane pith was then immersed in 50 mL of a 0.05 M FeCl3 anhydrous ethanol / hydrochloric acid (1 mol / L) mixture, where the volume ratio of ethanol to HCl was 4:1. The mixture was placed in a 150 mL polytetrafluoroethylene-lined stainless steel autoclave. After standing at room temperature for 2 h, the autoclave was sealed and placed in a 140°C oven until the absolute temperature in the autoclave reached 413.15 Kelvin. The mixture was heated for 2 h and then cooled naturally to room temperature.

[0054] (2) Washing and drying: The sugarcane pith after the hydrothermal treatment was taken out, washed by centrifugation with water and ethanol until the supernatant was colorless, and dried at 80°C for 12 h.

[0055] (3) Secondary hydrothermal reaction: The dried sugarcane pith was immersed in 100 ml of urea aqueous solution for 24 h (mass ratio of urea to sugarcane pith = 4:1).

[0056] (4) Carbonization: The sugarcane pith treated with FeCl3 / urea was placed in a quartz boat, transferred to a tube furnace under 60 sccm of nitrogen, and then heated at 5°C / min. - 1 Heat to 800°C and maintain for 2 h.

[0057] (5) Pulverization: The high-temperature carbonized product was fully ground in an agate mortar to obtain a black powder (expressed as Fe-SAC). Figure 2 This is a TEM image of the Fe-SAC prepared in this example. From the image, it can be observed that the Fe-N single-atom catalyst supported by the prepared sugarcane pith thin carbon network forms lattice fringes of graphite carbon, and the single-atom Fe is anchored in the graphite lattice.

[0058] Figure 1 The XRD comparison diagram of the sugarcane pith thin carbon mesh supported Fe-N single atom catalyst obtained in this example and other catalysts (C represents pure sugarcane pith carbon catalyst, CN represents nitrogen (urea) doped sugarcane pith carbon catalyst, Fe-C represents sugarcane pith supported ferric chloride catalyst) is shown in FIG. Figure 1 It can be seen that the prepared sugarcane pith carbon-supported iron single-atom catalyst exhibits two broad diffraction peaks in the ranges of 20.0-30.0° and 40.0-50.0°, corresponding to the (002) and (101) crystal planes of graphitic carbon, respectively. In addition, the other samples all exhibit a sharp peak at 2θ = 26.4°, corresponding to the (002) of graphitic carbon, indicating that a certain amount of graphitization has occurred in the amorphous carbon. Only diffraction peaks belonging to C and SiO2 were observed in the different catalysts, and no diffraction peaks of the Fe element appeared, indicating that the Fe loading was extremely small and uniformly dispersed.

[0059] Figure 3 TEM and energy dispersive X-ray spectra (EDS) of the sugarcane pith thin carbon network supported Fe-N single atom catalyst obtained in this example. It can be seen from the figure that there are no Fe nanoclusters on the carbon-nitrogen base, but it is clearly proved that the Fe, N and C elements are uniformly distributed on the entire Fe-SAC. The EDS element mapping results further confirm the existence of uniformly dispersed N and Fe on the carbon skeleton. Figure 1 The XRD results are consistent with those of .

[0060] Figure 4 and 5The high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) image of the Fe-N single atom catalyst obtained in the present embodiment is combined with spherical aberration to verify the existence form of the single atom again. The Fe atom in the Fe-SAC catalyst is detected by aberration-corrected high-angle annular dark field scanning transmission electron microscopy (AC-HAADF-STEM), and many dispersed white spots are found in other areas of the Fe-SAC, which indicates that Fe atoms are formed therein.

[0061] The Fe-N single atom catalyst obtained in the present embodiment is used in the degradation experiment of tetracycline hydrochloride.

[0062] In a 100 ml beaker, 50 ml of 10 mg / l tetracycline hydrochloride solution is added and the Ph is adjusted to about 7, and then 0.5 g / L of Fe-SAC catalyst is added. After irradiation for 2 h with a 200-400 mW / cm² xenon lamp (420 nm filter), the photocatalytic removal rate is 96.8-100% (as shown in Table 1). Figure 6

[0063] In a 100 ml beaker, 50 ml of 10 mg / l tetracycline hydrochloride solution is added and the Ph is adjusted to about 7, and then 0.5 g / L of Fe-SAC catalyst is added. After irradiation for 2 h with a 200-400 mW / cm² xenon lamp (420 nm filter), the photocatalytic removal rate is 96.8-100% (as shown in Table 1). Figure 6

[0064] Comparative Example 1 (omit the second hydrothermal reaction, and the first hydrothermal reaction does not add FeCl3)

[0065] A method for preparing a catalyst, the steps are as follows:

[0066] (1) Hydrothermal reaction: The sugarcane pulp is crushed and sieved into 20-100 mesh particles, then 3 g of sugarcane pulp is soaked in 50 ml of anhydrous ethanol / hydrochloric acid (1 mol / l) mixed solution, the volume ratio of ethanol to HCl is 4:1, in a 150 ml polytetrafluoroethylene lined stainless steel high-pressure reaction kettle. After standing at room temperature for 2 h, the high-pressure reaction kettle is sealed and placed in a 140°C oven to make the absolute temperature in the high-pressure reaction kettle reach 413.15 Kelvin, and after heating for 2 h, it is naturally cooled to room temperature

[0067] (2) Washing and drying: The hydrothermally treated sugarcane pulp is taken out, washed by centrifugation with water and ethanol until the supernatant is colorless, and dried at 80°C for 12 h.

[0068] (3) Carbonization: The dried sugarcane pulp is loaded into a quartz boat and transferred to a tube furnace under 60 sccm of nitrogen, then heated to 800°C at a rate of 5°C / min - 1 and kept for 2 h. ​​

[0069] (4) Grinding: The high-temperature carbonized product was fully ground in an agate mortar to obtain a black powder, which was named catalyst C.

[0070] Application experiment of the obtained catalyst C in the degradation of tetracycline:

[0071] Add 50ml of 10mg / l tetracycline hydrochloride solution to a 100ml beaker and adjust the pH to 7. Then add 0.5g / l of catalyst C. Irradiate with a 200-400mW / cm² xenon lamp for 2h. The photocatalytic removal rate is 22.6-25.8%. (See attached Figure 6 ).

[0072] Comparative Example 2 (one-step hydrothermal without FeCl3)

[0073] (1) Sugarcane pith was crushed and sieved to obtain 20-100 mesh particles. 3 g of sugarcane pith was then immersed in 50 mL of anhydrous ethanol / 1 mol / l hydrochloric acid (ethanol:1 mol / l HCl) (4:1, v / v) in a 150 mL polytetrafluoroethylene-lined stainless steel autoclave. After standing at room temperature for 2 h, the autoclave was sealed and placed in an oven heated at 140°C. After 2 h, it was naturally cooled to room temperature.

[0074] (2) After hydrothermal treatment, the sugarcane pith was removed, washed by centrifugation with water and ethanol until the supernatant was colorless, and dried at 80°C for 12 h.

[0075] (3) Then immerse it in 100 ml of urea aqueous solution (mass ratio of urea to sugarcane pith = 4:1) for 24 h at a reaction temperature of 80°C.

[0076] (4) The sugarcane pith treated with anhydrous ethanol / (1 mol / l) hydrochloric acid and urea was placed in a quartz boat and transferred to a tube furnace under 60 sccm of nitrogen, and then heated at 5°C / min. - 1 Heat to 800°C and maintain for 2 h.

[0077] (5) The high-temperature carbonized product was thoroughly ground in an agate mortar to obtain a black powder, which was named catalyst CN.

[0078] Application experiment of the obtained catalyst CN in the degradation of tetracycline:

[0079] Add 50ml of 10mg / l tetracycline hydrochloride solution to a 100ml beaker and adjust the pH to 7. Then add 0.5g / l of catalyst. Irradiate with a 200-400mW / cm² xenon lamp for 2 hours. The photocatalytic removal rate is 44.8-48.6%. (See attached) Figure 6 ).

[0080] Comparative Example 3 (omitting secondary hydrothermal treatment)

[0081] (1) Sugarcane pith was crushed and sieved to obtain 20-100 mesh particles. 3 g of sugarcane pith was then immersed in 50 mL of a mixture of 0.05 M FeCl3 anhydrous ethanol and hydrochloric acid (1 mol / L) (the volume ratio of ethanol to HCl was 4:1) in a 150 mL polytetrafluoroethylene-lined stainless steel autoclave. After standing at room temperature for 2 h, the autoclave was sealed and placed in an oven at 140°C for 2 h before being naturally cooled to room temperature.

[0082] (2) Take out the sugarcane pith after hydrothermal treatment and dry it at 80℃ for 12h.

[0083] (3) The sugarcane pith treated with FeCl3 anhydrous ethanol / hydrochloric acid was placed in a quartz boat, transferred to a tube furnace under 60 sccm of nitrogen, and then heated at 5°C / min. - 1 The temperature was raised to 800°C and maintained for 2 hours. Finally, the high-temperature carbonized product was thoroughly ground in an agate mortar to obtain a black powder, which was named Fe-C. Figure 3 For the Fe-C prepared in this example, 50 ml of a 10 mg / l tetracycline hydrochloride solution was added to a 100 ml beaker and adjusted to pH ≈ 7. 0.5 g / l of catalyst was then added. The reaction was irradiated with a 200-400 mW / cm² xenon lamp for 2 hours, and the photocatalytic removal rate was 48.3-54.5%. (See attached figure.) Figure 6 ).

[0084] Comparative Example 4 (one-step hydrothermal process with simultaneous addition of FeCL3 and urea)

[0085] (1) The sugarcane pith was crushed and sieved into particles of 20-100 mesh. Then 3 g of sugarcane pith, 13.5 g of ferric chloride hexahydrate, and 7 g of urea were fully mixed in 100 ml of pure water and stirred magnetically for half an hour. The mixed solution was then poured into a 150 ml polytetrafluoroethylene-lined stainless steel autoclave. After the autoclave was sealed, it was placed in an oven and heated at 140 °C for 2 h, and then naturally cooled to room temperature.

[0086] (2) The sugarcane pith after hydrothermal treatment was taken out, washed three times with water and ethanol, and dried at 80°C for 12 hours to obtain a mixed solid.

[0087] (3) The mixed solid was placed in a quartz boat, transferred to a tube furnace under 60 sccm of nitrogen, and then heated at 5°C / min. - 1 The temperature was raised to 800°C and maintained for 2 hours. Finally, the high-temperature carbonized product was thoroughly ground in an agate mortar to obtain a black powder, which was named traditional Fe catalyst.

[0088] Application experiment of the obtained traditional Fe catalyst in the degradation of tetracycline:

[0089] Add 50ml of 10mg / l tetracycline hydrochloride solution to a 100ml beaker and adjust the pH to 7, then add 0.5g / l of catalyst. Irradiate with a 200-400mW / cm² xenon lamp for 2h. The photocatalytic removal rate is 97.3%-100%, but the total dark adsorption rate is also 100% in the dark environment, making it impossible to distinguish whether the sample is a catalyst or an adsorbent (e.g., attached). Figure 7 ). Example 2

[0090] (1) Primary hydrothermal reaction: The crushed sugarcane pith was further sieved into 20-100 mesh. 3 g of sugarcane pith was then immersed in 50 mL of a 0.05 M FeCl3 anhydrous ethanol / hydrochloric acid (1 mol / L) mixture, where the volume ratio of ethanol to HCl was 4:1. The mixture was placed in a 150 mL polytetrafluoroethylene-lined stainless steel autoclave. After standing at room temperature for 2 h, the autoclave was sealed and placed in a 140°C oven until the absolute temperature in the autoclave reached 413.15 K. The mixture was heated for 2 h and then naturally cooled to room temperature.

[0091] (2) Washing and drying: The sugarcane pith after the hydrothermal treatment was taken out, washed by centrifugation with water and ethanol until the supernatant was colorless, and dried at 80°C for 12 h.

[0092] (3) Secondary hydrothermal reaction: The dried sugarcane pith was immersed in 100 ml of urea aqueous solution for 24 h (mass ratio of sugarcane pith to urea = 1:5).

[0093] (4) Carbonization: The sugarcane pith treated with FeCl3 / urea was placed in a quartz boat, transferred to a tube furnace under 60 sccm of nitrogen, and then heated at 5°C / min. - 1 Heat to 800°C and maintain for 2 h.

[0094] (5) Crushing: The product after high-temperature carbonization was fully ground in an agate mortar to obtain a black powder. The application experiment of the obtained catalyst in the degradation of tetracycline:

[0095] In a 100ml beaker, add 50ml of a 10mg / l tetracycline hydrochloride solution and adjust the pH to ≈ 7. Then, add 0.5g / l of a catalyst. Irradiate with a 200-400mW / cm² xenon lamp for 2 hours, and the photocatalytic removal rate is 95.5%-98.6%. Example 3

[0096] (1) Primary hydrothermal reaction: The crushed sugarcane pith was further sieved into 20-100 mesh. 3 g of sugarcane pith was then immersed in 50 mL of a 0.05 M FeCl3 anhydrous ethanol / hydrochloric acid (1 mol / L) mixture, where the volume ratio of ethanol to HCl was 4:1. The mixture was placed in a 150 mL polytetrafluoroethylene-lined stainless steel autoclave. After standing at room temperature for 2 h, the autoclave was sealed and placed in a 140°C oven until the absolute temperature in the autoclave reached 413.15 K. The mixture was heated for 2 h and then naturally cooled to room temperature.

[0097] (2) Washing and drying: The sugarcane pith after the hydrothermal treatment was taken out, washed by centrifugation with water and ethanol until the supernatant was colorless, and dried at 80°C for 12 h.

[0098] (3) Secondary hydrothermal reaction: The dried sugarcane pith was immersed in 100 ml of urea aqueous solution for 24 h (mass ratio of sugarcane pith to urea = 1:6).

[0099] (4) Carbonization: The sugarcane pith treated with FeCl3 / urea was placed in a quartz boat, transferred to a tube furnace under 60 sccm of nitrogen, and then heated at 5°C / min. - 1 Heat to 800°C and maintain for 2 h.

[0100] (5) Crushing: The product after high-temperature carbonization was fully ground in an agate mortar to obtain a black powder. The application experiment of the obtained catalyst in the degradation of tetracycline:

[0101] In a 100ml beaker, add 50ml of a 10mg / l tetracycline hydrochloride solution and adjust the pH to ≈ 7. Then, add 0.5g / l of a catalyst. Irradiate with a 200-400mW / cm² xenon lamp for 2 hours, and the photocatalytic removal rate is 97.8%-100%. Example 4

[0102] (1) Primary hydrothermal reaction: The crushed sugarcane pith was further sieved into 20-100 mesh. 3 g of sugarcane pith was then immersed in 50 mL of a 0.05 M FeCl3 anhydrous ethanol / hydrochloric acid (1 mol / L) mixture, where the volume ratio of ethanol to HCl was 4:1. The mixture was placed in a 150 mL polytetrafluoroethylene-lined stainless steel autoclave. After standing at room temperature for 2 h, the autoclave was sealed and placed in a 140°C oven until the absolute temperature in the autoclave reached 413.15 K. The mixture was heated for 2 h and then naturally cooled to room temperature.

[0103] (2) Washing and drying: The sugarcane pith after the hydrothermal treatment was taken out, washed by centrifugation with water and ethanol until the supernatant was colorless, and dried at 80°C for 12 h.

[0104] (3) Secondary hydrothermal reaction: The dried sugarcane pith was immersed in 100 ml of urea aqueous solution for 24 h (mass ratio of sugarcane pith to urea = 1:6).

[0105] (4) Carbonization: The sugarcane pith treated with FeCl3 / urea was placed in a quartz boat, transferred to a tube furnace under 60 sccm of nitrogen, and then heated at 5°C / min. - 1 The temperature was raised to 400°C and maintained for 2 h.

[0106] (5) Crushing: The product after high-temperature carbonization was fully ground in an agate mortar to obtain a black powder. The application experiment of the obtained catalyst in the degradation of tetracycline:

[0107] In a 100ml beaker, add 50ml of a 10mg / l tetracycline hydrochloride solution and adjust the pH to ≈ 7. Then, add 0.5g / l of a catalyst. Irradiate with a 200-400mW / cm² xenon lamp for 2 hours, and the photocatalytic removal rate is 69.5%-72.8%. Example 5

[0108] (1) Primary hydrothermal reaction: The crushed sugarcane pith was further sieved into 20-100 mesh. 3 g of sugarcane pith was then immersed in 50 mL of a 0.05 M FeCl3 anhydrous ethanol / hydrochloric acid (1 mol / L) mixture, where the volume ratio of ethanol to HCl was 4:1. The mixture was placed in a 150 mL polytetrafluoroethylene-lined stainless steel autoclave. After standing at room temperature for 2 h, the autoclave was sealed and placed in a 140°C oven until the absolute temperature in the autoclave reached 413.15 K. The mixture was heated for 2 h and then naturally cooled to room temperature.

[0109] (2) Washing and drying: The sugarcane pith after the hydrothermal treatment was taken out, washed by centrifugation with water and ethanol until the supernatant was colorless, and dried at 80°C for 12 h.

[0110] (3) Secondary hydrothermal reaction: The dried sugarcane pith was immersed in 100 ml of urea aqueous solution for 24 h (mass ratio of sugarcane pith to urea = 1:6).

[0111] (4) Carbonization: The sugarcane pith treated with FeCl3 / urea was placed in a quartz boat, transferred to a tube furnace under 60 sccm of nitrogen, and then heated at 5°C / min. - 1 The temperature was raised to 600°C and maintained for 2 h.

[0112] (5) Crushing: The product after high-temperature carbonization was fully ground in an agate mortar to obtain a black powder. The application experiment of the obtained catalyst in the degradation of tetracycline:

[0113] In a 100ml beaker, add 50ml of a 10mg / l tetracycline hydrochloride solution and adjust the pH to ≈ 7. Then, add 0.5g / l of a catalyst. Irradiate with a 200-400mW / cm² xenon lamp for 2 hours, and the photocatalytic removal rate is 80.6.5%-83.2%.

[0114] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. Application of sugarcane pith thin carbon mesh supported Fe-N single atom catalyst in photocatalytic degradation of tetracycline, characterized in that: The preparation method of the sugarcane pith thin carbon mesh supported Fe-N single atom catalyst comprises the following steps: (1) Immerse the sugarcane pith particles in a mixture of FeCl3, ethanol and hydrochloric acid, seal and pressurize, and perform a hydrothermal reaction; (2) washing and drying the reactant obtained in step (1); (3) adding the dried product obtained in step (2) to a urea solution for a secondary hydrothermal reaction; (4) heating the reaction product of step (3) under an inert atmosphere for carbonization; (5) The carbonized product of step (4) is crushed to obtain a sugarcane pith thin carbon network loaded Fe-N single atom catalyst.

2. The use according to claim 1, characterized in that In step (1), the particle size of the sugarcane pith particles is 20-100 mesh.

3. The use according to claim 1, characterized in that In step (1), the mass ratio of sugarcane pith to FeCl3 is 1:4~3:13.5; the volume ratio of ethanol to hydrochloric acid is 4~9:1, the concentration of hydrochloric acid is 1 mol / L~6 mol / L; and the concentration of FeCl3 in the mixed solution of ethanol and hydrochloric acid is 0.05~0.5 mol / L.

4. The use according to claim 3, characterized in that The reaction temperature of step (1) is 120-140° C., and the reaction time is 2-2.5 h.

5. The use according to any one of claims 1 to 4, characterized in that In step (3), the mass ratio of sugarcane pith to urea is 1:4-6; the reaction temperature is 80°C-100°C; and the reaction time is 12-24h.

6. The use according to claim 5, characterized in that The carbonization temperature of step (4) is 600-800°C, and the carbonization time is 2-4 hours.

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