Metal oxide / carbon nitride nanotube photocatalyst as well as preparation method and application thereof

Abstract

The invention provides a metal oxide / carbon nitride nanotube photocatalyst as well as a preparation method and application thereof. The preparation method comprises the following steps: self-assembling to form a melamine-melamine uric acid supramolecular polymer; preparing a carbon nitride nanotube precursor; carbon nanotubes are nitrided; loading a metal oxide on the carbon nitride nanotube by an ultrasonic-assisted blending-calcining method; according to the preparation method disclosed by the invention, the metal oxide is loaded on the carbon nitride nanotube through an ultrasonic-assisted blending-calcining method to construct the composite photocatalyst, the light absorption range of the photocatalyst is widened to a wider visible light wave band, and the generation quantity of photo-induced electron-hole pairs is increased; meanwhile, by utilizing proper energy level matching between the metal oxide and the carbon nitride nanotube, effective transfer and separation of photo-induced electrons and holes between the metal oxide and the carbon nitride nanotube are promoted, and the performance of the photocatalyst is remarkably improved, so that efficient degradation of organophosphorus pesticides and in-situ adsorption of mineralized product inorganic phosphorus are realized.

Description

Technical Field

[0001] The present invention belongs to the technical fields of composite material preparation and environmental catalysis, and particularly relates to a metal oxide / carbon nitride nanotube photocatalyst, a preparation method thereof, and an application thereof. Background Art

[0002] The excessive presence of pesticides and inorganic phosphorus in natural water bodies mainly stems from the discharge of agricultural return water and urban sewage, which poses a serious threat to the ecological environment and human health. In China, organophosphorus pesticides dominate the pesticide market, accounting for more than 80%. As a precious non-renewable strategic resource, a large amount of phosphorus is discharged into the environment every year, which not only causes a great waste of phosphorus resources, but also leads to ecological environment problems such as water eutrophication, seriously threatening the balance of the aquatic ecosystem; therefore, removing organophosphorus pesticides from water bodies and recovering inorganic phosphorus in water is of great practical significance for alleviating the current situation of water phosphorus pollution and phosphorus ore resource shortage.

[0003] For the removal of organic phosphorus and inorganic phosphorus in water bodies, a variety of methods have been developed at home and abroad. For the removal of organic phosphorus, it mainly includes biological methods, adsorption methods, and advanced oxidation technologies (AOPs), among which photocatalytic oxidation, electrocatalytic oxidation, Fenton method, and persulfate advanced oxidation technology are the most widely studied advanced oxidation methods. In particular, the photocatalytic synergistic persulfate advanced oxidation method (SR-AOPs), with its strong oxidation ability and high degradation effect, is recognized as an efficient and environmentally friendly treatment technology.

[0004] For the removal of inorganic phosphorus, it mainly includes biological methods, crystallization methods, chemical precipitation methods, ion exchange methods, adsorption methods, etc. Among these methods, the adsorption method is widely regarded as one of the optimal methods due to its high efficiency and convenience in practical applications; especially when using metal oxides as adsorbents, it shows significant advantages such as high adsorption capacity and selectivity for inorganic phosphorus.

[0005] In the research of photocatalytic synergistic persulfate advanced oxidation technology, the preparation and optimization of green and efficient photocatalysts are the key. As a two-dimensional material with excellent chemical stability, a suitable band gap structure, and a unique electronic structure, carbon nitride nanotubes show great application potential in the photocatalytic degradation of organic pollutants. By modification or compounding with other materials, its photocatalytic performance can be further improved.

[0006] In the photocatalytic process, organophosphorus pesticides are gradually oxidized and decomposed into small molecule organic fragments and finally converted into inorganic phosphorus. This process not only effectively reduces the toxicity of organophosphorus pesticides, but also realizes their transformation into environmentally friendly products. However, for the removal of the mineralization product inorganic phosphorus, it is of great significance to develop an adsorbent with selectivity, high efficiency, and reusability after desorption for removing inorganic phosphorus in water. MgO, Fe 2O 3 、Al 2 O 3 、La 2 O 3 、ZrO 2 Metal oxides such as these, due to their porosity and high specific surface area, can provide more adsorption sites and have a strong adsorption capacity for inorganic phosphate ions.

[0007] Although a large number of studies have reported the application of carbon nitride nanotubes in photocatalytic degradation of pollutants and the ability of metal oxides as adsorbents in phosphorus removal, the research on combining these two for photocatalytic degradation of organophosphorus pesticides and in-situ adsorption and recovery of inorganic phosphorus products is currently blank. Therefore, developing a new treatment technology that combines carbon nitride nanotubes with metal oxides to achieve efficient degradation of organophosphorus pesticides and in-situ recovery of inorganic phosphorus has important research value and practical significance. Summary of the Invention

[0008] Aiming at the problems of current degradation of organophosphorus pesticides and eutrophication caused by excessive phosphorus in water bodies after degradation, the purpose of the present invention is to provide a metal oxide / carbon nitride nanotube photocatalyst, its preparation method and application, to construct a composite photocatalytic system, efficiently realize the photocatalytic conversion of organophosphorus in pesticides in water and the in-situ adsorption of mineralized product inorganic phosphorus, provide new ideas for the development of bifunctional composites to degrade organophosphorus pesticides and in-situ adsorb inorganic phosphorus, and explore new solutions to alleviate the contradiction between the shortage of phosphate rock resources and water body phosphorus pollution.

[0009] To achieve the above purpose, the present invention adopts the following technical solutions:

[0010] In the first aspect of the present invention, a preparation method of a metal oxide / carbon nitride nanotube photocatalyst is provided, including the following steps:

[0011] S1. Using melamine and cyanuric acid as raw materials, self-assemble to form a melamine-cyanuric acid supramolecular polymer;

[0012] S2. Remove the unassembled melamine and cyanuric acid in step S1 to obtain a supramolecular polymer flocculent precipitate. After freeze-drying the supramolecular polymer flocculent precipitate, a carbon nitride nanotube precursor is obtained;

[0013] S3. Calcinate the carbon nitride nanotube precursor obtained in step S2 under an argon atmosphere to obtain carbon nitride nanotubes;

[0014] S4. Ultrasonically disperse the metal oxide and the carbon nitride nanotubes obtained in step S3 in a methanol solution. After drying, grind and calcine the obtained powder to obtain a metal oxide / carbon nitride nanotube photocatalyst; wherein, the metal oxide is one or more of MgO, Fe 2 O 3 、Al 2 O 3 、La 2 O 3 、ZrO 2 .

[0015] Furthermore, the preparation of the supramolecular polymer in step S1 specifically includes the following steps:

[0016] S11. Weigh melamine and cyanuric acid according to a mass ratio of melamine:cyanuric acid = 1:1 to 1.2, dissolve them separately in deionized water and stir until completely dissolved to obtain a melamine solution and a cyanuric acid solution;

[0017] S12. Slowly add the melamine solution to the cyanuric acid solution that is being stirred evenly for the self-assembly of melamine and cyanuric acid to form a melamine-cyanuric acid supramolecular polymer.

[0018] Furthermore, in step S12, the self-assembly conditions of melamine and cyanuric acid are: assemble at 70-90°C for 1-2 hours.

[0019] Furthermore, the preparation of the carbon nitride nanotube precursor in step S2 specifically includes the following steps:

[0020] S21. After centrifuging the solution that has completed the self-assembly reaction in step S12, wash it 2-4 times with deionized water at 70-90°C to remove unassembled melamine and cyanuric acid, then filter it. The filtered product is redispersed in deionized water and precipitated at room temperature for 12-15 h, and the supernatant is removed to obtain a flocculent precipitate;

[0021] S22. Freeze-dry the flocculent precipitate obtained in step S21 to obtain a carbon nitride nanotube precursor.

[0022] Furthermore, in step S22, the conditions for freeze-drying the flocculent precipitate are: freeze-dry at -40 to -80°C and 0.05 to 0.1 Mpa for 40 to 48 hours.

[0023] Further, the preparation of carbon nitride nanotubes in step S3 specifically includes the following steps: placing the carbon nitride nanotube precursor obtained in step S22 in a tube furnace and calcining it at 500 - 550 °C for 2 - 3 hours under an argon atmosphere. As the temperature rises, the supramolecular polymer gradually undergoes thermal polycondensation to form carbon nitride nanotubes; among them, the heating rate of the tube furnace is 2 °C / min.

[0024] Further, the preparation of the metal oxide / carbon nitride nanotube photocatalyst in step S4 specifically includes the following steps:

[0025] S41. Weigh a certain amount of carbon nitride nanotubes and stir them to disperse in methanol. Subsequently, add a certain amount of metal oxide nanoparticles to this solution while stirring. After the addition is completed, continue to stir and mix for 10 - 20 min. Further ultrasonically treat the obtained mixed solution. The ultrasonic conditions are: ultrasonic treatment at 40 - 80 kHz for 40 - 60 min; after the ultrasonic treatment, dry it at 80 - 90 °C for 20 - 25 hours;

[0026] S42. Grind and refine the powder obtained after drying in step S41, and then place it in a muffle furnace and calcine it at 120 - 150 °C for 2 - 3 hours to obtain the metal oxide / carbon nitride nanotube photocatalyst.

[0027] Further, in step S41, the mass ratio of the metal oxide to the carbon nitride nanotubes is 1:4 - 5.

[0028] The second aspect of the present invention lies in providing a metal oxide / carbon nitride nanotube photocatalyst, which is prepared according to the above-mentioned preparation method of the metal oxide / carbon nitride nanotube photocatalyst.

[0029] The third aspect of the present invention lies in providing an application of the metal oxide / carbon nitride nanotube photocatalyst in the deep purification of phosphorus-containing wastewater. The metal oxide / carbon nitride nanotube photocatalyst is the above-mentioned metal oxide / carbon nitride nanotube photocatalyst or is prepared by the preparation method of the above-mentioned metal oxide / carbon nitride nanotube photocatalyst.

[0030] Compared with the prior art, the present invention has at least the following beneficial effects:

[0031] 1. The preparation method of the metal oxide / carbon nitride nanotube photocatalyst of the present invention uses ultrasonic-assisted co - blending - calcination method to combine metal oxides (MgO, Fe 2 O 3 、Al 2 O 3 、La 2 O 3 、ZrO 2)Loaded on carbon nitride nanotubes to construct a composite photocatalyst, which can extend the light absorption range of the photocatalyst to a wider visible light band, thereby increasing the generation number of photo-generated electron-hole pairs, significantly improving the performance of the photocatalyst; at the same time, using the appropriate energy level matching between metal oxides (MgO, Fe 2 O 3 、Al 2 O 3 、La 2 O 3 、ZrO 2 ) and carbon nitride nanotubes to promote the effective transfer and separation of photo-generated electrons and holes between the two, reduce their recombination probability, enhance the utilization of visible light, further improve the photocatalytic efficiency of the photocatalyst, and generate more photo-generated carriers to degrade organophosphorus pesticides.

[0032] 2. Preparation method of the metal oxide / carbon nitride nanotube photocatalyst of the present invention. Load metal oxides (MgO, Fe 2 O 3 、Al 2 O 3 、La 2 O 3 、ZrO 2 ) on carbon nitride nanotubes. The carbon nitride nanotubes are tubular structures with a large specific surface area, which is conducive to the uniform loading of metal oxides and also provides channels for the adsorption and diffusion of pollutants; and the surface characteristics of the carbon nitride nanotubes (the surface of the carbon nitride nanotubes is smooth, the size is uniform, and its surface has a certain charge and good conductivity, etc.) are conducive to the uniform dispersion of metal oxides, can effectively prevent the agglomeration of metal oxides, and enable the metal oxides to be loaded with small particle sizes, thereby increasing the active sites of the catalyst.

[0033] 3. Preparation method of the metal oxide / carbon nitride nanotube photocatalyst of the present invention. Load metal oxides (MgO, Fe 2 O 3 、Al 2 O 3 、La 2 O 3 、ZrO 2Loaded on carbon nitride nanotubes, compared with other porous carbon materials, the photocatalytic performance of carbon nitride nanotubes is significantly improved. Moreover, the pore structure of carbon nitride nanotubes is ordered and the pore size distribution is uniform. After combining with metal oxides, it can ensure the adsorption efficiency of the mineralization product inorganic phosphorus, which is beneficial to the recovery of inorganic phosphorus, the mineralization product after the degradation of organophosphorus pesticides. In the present invention, metal oxides and carbon nitride nanotubes are compounded, and a composite photocatalyst is constructed by using the synergistic effect between the two, which acts on the deep purification of phosphorus-containing wastewater and promotes each other in aspects such as photocatalysis and adsorption, so as to achieve efficient degradation of organophosphorus pesticides and in-situ adsorption of inorganic phosphorus, the mineralization product. It provides a new idea for the development of a bifunctional composite material to degrade organophosphorus pesticides and in-situ adsorb inorganic phosphorus, and explores a new solution to alleviate the contradiction between the shortage of phosphate rock resources and water body phosphorus pollution.

[0034] 4. The preparation method of the metal oxide / carbon nitride nanotube photocatalyst of the present invention can effectively compound metal oxides and carbon nitride nanotubes, and is relatively stable after loading, without the problem of desorption of metal oxides.

[0035] 5. The metal oxide / carbon nitride nanotube photocatalyst of the present invention is used for the deep purification of phosphorus-containing wastewater, which can significantly improve the removal rate of organophosphorus pesticides and the adsorption rate of inorganic phosphorus, the mineralization product, achieve an efficient PMS activation effect and effectively degrade organophosphorus pesticides, and effectively inhibit the problem of secondary pollution of inorganic phosphorus, the mineralization product (water eutrophication, soil property change, ecosystem food chain impact), providing a new idea for the treatment of pesticide pollution residues in the water environment. Description of the Drawings

[0036] Figure 1 Figure a in the middle is the scanning electron microscope image of carbon nitride nanotubes (CNNTs) prepared in Example 1 of the present invention, and Figure b is the scanning electron microscope image of magnesium oxide / carbon nitride nanotube photocatalyst (MgO@CNNTs) prepared in Example 1 of the present invention.

[0037] Figure 2 It is the X-ray diffraction pattern of magnesium oxide (MgO), carbon nitride nanotubes (CNNTs) and magnesium oxide / carbon nitride nanotube photocatalyst (MgO@CNNTs) in Example 1 of the present invention.

[0038] Figure 3 It is the comparison chart of the degradation rates of glyphosate in Examples 1-5 and Comparative Examples 1-3 of the present invention.

[0039] Figure 4 It is the comparison chart of the adsorption amounts of inorganic phosphorus, the mineralization product of photocatalytic degradation of glyphosate-containing wastewater in Examples 1-5 and Comparative Examples 1-3 of the present invention. Detailed Description of the Invention

[0040] The present invention will be further described below in conjunction with the accompanying drawings through specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention.

[0041] The preparation method of the metal oxide / carbon nitride nanotube photocatalyst of the present invention loads metal oxides (MgO, Fe 2 O 3 , Al 2 O 3 , La 2 O 3 , ZrO 2 ) on carbon nitride nanotubes through an ultrasonic-assisted co-blending-calcination method to construct a composite photocatalyst. On the one hand, it can expand the light absorption range of the photocatalyst to a wider visible light band to generate more photo-generated electron-hole pairs, significantly improving the performance of the photocatalyst; at the same time, due to the appropriate energy level matching between the metal oxide and the carbon nitride nanotubes, when illuminated, photo-generated electrons and holes can be effectively transferred and separated between the two, reducing their recombination probability, enhancing the utilization of visible light, further improving the photocatalytic efficiency of the photocatalyst, and generating more photo-generated carriers to degrade organophosphorus pesticides; on the other hand, it can efficiently achieve the photocatalytic conversion of organophosphorus pesticides in water and the in-situ adsorption of the mineralized product inorganic phosphorus, providing new ideas for the development of bifunctional composite materials to degrade organophosphorus pesticides and in-situ adsorb inorganic phosphorus, and exploring new solutions to alleviate the contradiction between the shortage of phosphate rock resources and water body phosphorus pollution.

[0042] Example 1

[0043] The preparation of the magnesium oxide / carbon nitride nanotube photocatalyst (MgO@CNNTs) in this example includes the following steps:

[0044] I. Using melamine and cyanuric acid as raw materials, self-assembling to form a melamine-cyanuric acid supramolecular polymer:

[0045] S11. Weigh 2 g of melamine and 2 g of cyanuric acid and dissolve them separately in 500 ml of deionized water. Stir at 80 °C for about 10 minutes until completely dissolved to obtain a melamine solution and a cyanuric acid solution;

[0046] S12. Slowly add the melamine solution to the cyanuric acid solution that is being evenly stirred for the self-assembly of melamine and cyanuric acid, and self-assemble at 80 °C for 1 hour to form a melamine-cyanuric acid supramolecular polymer.

[0047] II. Preparation of the carbon nitride nanotube precursor:

[0048] S21. After centrifuging the solution that has completed the self-assembly reaction in step S12, wash it twice with deionized water at 80 °C to remove unassembled melamine and cyanuric acid, and then filter. The filtered product is redispersed in deionized water and precipitated at room temperature for 12 h. Remove the supernatant to obtain a flocculent precipitate;

[0049] S22. Freeze-dry the flocculent precipitate obtained in step S21 at -50 °C and 0.05 Mpa for 48 hours to obtain a carbon nitride nanotube precursor.

[0050] III. Preparation of carbon nitride nanotubes (CNNTs):

[0051] S3. Weigh 2 g of the carbon nitride nanotube precursor obtained in step S22 and introduce it into a covered ceramic crucible. Place it in a tube furnace and calcine it under an argon atmosphere. As the temperature rises, the supramolecular polymer gradually thermally polycondenses into carbon nitride nanotubes CNNTs; among them, set the heating rate of the tube furnace to 2 °C / min and the target temperature to 500 °C; when the temperature reaches 500 °C, maintain this temperature and calcine for 100 minutes.

[0052] IV. Preparation of magnesium oxide / carbon nitride nanotube photocatalyst (MgO@CNNTs):

[0053] S41. Weigh 1.0 g of the carbon nitride nanotubes obtained in step S3 and disperse them by magnetic stirring in 150 mL of methanol for 20 min. Then add 0.2 g of magnesium oxide nanoparticles to this solution while stirring. After the addition, continue to stir the mixture for 15 min. Further ultrasonically process the obtained mixed solution. The ultrasonic conditions are: ultrasonic for 45 min at 40 kHz; after the ultrasonic treatment, dry it in an oven at 85 °C for 24 h;

[0054] S42. Grind and refine the powder obtained after drying in step S41, and then place it in a muffle furnace and calcine it at 150 °C for 2 hours to obtain the magnesium oxide / carbon nitride nanotube photocatalyst MgO@CNNTs.

[0055] Characterize the carbon nitride nanotubes (CNNTs) prepared in step S3 of this example using a scanning electron microscope to obtain Figure 1 a, as can be seen from Figure 1 a: The carbon nitride nanotubes exhibit a typical tubular structure and their surface is relatively smooth;

[0056] Characterize the magnesium oxide / carbon nitride nanotube photocatalyst (MgO@CNNTs) prepared in step S42 of this example using a scanning electron microscope to obtain Figure 1 b, as can be seen from Figure 1As can be seen from b, magnesium oxide particles are evenly distributed on the surface of carbon nitride nanotubes, indicating that the loading of magnesium oxide on carbon nitride nanotubes has been successfully achieved;

[0057] In this example, the XRD patterns of magnesium oxide (MgO), carbon nitride nanotubes (CNNTs) prepared in step S3, and magnesium oxide / carbon nitride nanotube photocatalyst (MgO@CNNTs) prepared in step S42 are as Figure 2 shown. As can be seen from Figure 2 it, the magnesium oxide / carbon nitride nanotube photocatalyst simultaneously exhibits the characteristic peaks of carbon nitride nanotubes and magnesium oxide, indicating that the crystal structures of the two are not severely damaged after loading, and the composite material has been successfully prepared.

[0058] The above-prepared magnesium oxide / carbon nitride nanotube photocatalyst (MgO@CNNTs) is used to activate PMS to degrade organophosphorus (glyphosate, malathion, trichlorfon, dimethoate, parathion) pesticides; among them, (1) is glyphosate-containing phosphorus wastewater; (2) is malathion-containing phosphorus wastewater; (3) is trichlorfon-containing phosphorus wastewater; (4) is dimethoate-containing phosphorus wastewater; (5) is parathion-containing phosphorus wastewater; the reaction conditions are: the dosage of magnesium oxide / carbon nitride nanotube photocatalyst (MgO@CNNTs) is 0.2 g / L, and the dosage of PMS is 0.3 mM; the concentrations of the above organophosphorus pesticides are all 10 mg / L, the pH is 7, and the temperature is 25 °C;

[0059] After reacting for 45 min, the phosphorus-containing wastewater after the above degradation is detected, and the photocatalytic degradation rate results of each phosphorus-containing wastewater are as follows: glyphosate is 88.7% (see Figure 3 ), malathion is 86.1%, trichlorfon is 82.9%, dimethoate is 85.3%, and parathion is 87.2%; the adsorption amounts of the photocatalytic degradation products of inorganic phosphorus in each phosphorus-containing wastewater are as follows: glyphosate is 28.1 mg / g (see Figure 4 ), malathion is 30.1 mg / g, trichlorfon is 29.6 mg / g, dimethoate is 28.2 mg / g, and parathion is 26.7 mg / g.

[0060] Example 2

[0061] The preparation of the iron oxide / carbon nitride nanotube photocatalyst (Fe 2 O 3 @CNNTs) in this example includes the following steps:

[0062] First, using melamine and cyanuric acid as raw materials, self-assemble to form a melamine-cyanuric acid supramolecular polymer:

[0063] S11. Weigh 2 g of melamine and 2 g of cyanuric acid respectively, dissolve them in 500 ml of deionized water, and stir at 80 °C for about 10 minutes until completely dissolved to obtain a melamine solution and a cyanuric acid solution;

[0064] S12. Slowly add the melamine solution to the cyanuric acid solution that is being stirred evenly to carry out the self-assembly of melamine and cyanuric acid. Self-assemble at 80 °C for 1 hour to form a melamine-cyanuric acid supramolecular polymer.

[0065] II. Preparation of carbon nitride nanotube precursor:

[0066] S21. After centrifuging the solution that has completed the self-assembly reaction in step S12, wash it twice with deionized water at 80 °C to remove unassembled melamine and cyanuric acid, then filter it. The filtered product is redispersed in deionized water and precipitated at room temperature for 12 h. Remove the supernatant to obtain a flocculent precipitate;

[0067] S22. Freeze-dry the flocculent precipitate obtained in step S21 at -50 °C and 0.05 Mpa for 48 hours to obtain a carbon nitride nanotube precursor.

[0068] III. Preparation of carbon nitride nanotubes (CNNTs):

[0069] S3. Weigh 2 g of the carbon nitride nanotube precursor obtained in step S22, introduce it into a covered ceramic crucible, and place it in a tube furnace for calcination under an argon atmosphere. As the temperature rises, the supramolecular polymer gradually thermally polycondenses into carbon nitride nanotubes CNNTs; among them, set the heating rate of the tube furnace to 2 °C / min and the target temperature to 500 °C; when the temperature reaches 500 °C, maintain this temperature for calcination for 100 minutes.

[0070] IV. Preparation of iron oxide / carbon nitride nanotube photocatalyst (Fe 2 O 3 @CNNTs):

[0071] S41. Weigh 1.0 g of the carbon nitride nanotubes obtained in step S3 and disperse them by magnetic stirring in 150 mL of methanol for 20 min. Then add 0.2 g of iron oxide nanoparticles to this solution while stirring. After the addition, continue to stir the mixture for 15 min. Further ultrasonically treat the obtained mixed solution. The ultrasonic conditions are: ultrasonic treatment at 40 kHz for 45 min; after the ultrasonic treatment, dry it in an oven at 85 °C for 24 h;

[0072] S42. Grind and refine the powder obtained after drying in step S41, and then calcine it in a muffle furnace at 150 °C for 2 hours to obtain the iron oxide / carbon nitride nanotube photocatalyst Fe 2 O3 @CNNTs.

[0073] The prepared iron oxide / carbon nitride nanotube photocatalyst (Fe 2 O 3 @CNNTs) is used to activate PMS for the degradation of organophosphorus (glyphosate, malathion, trichlorfon, dimethoate, parathion) pesticides; among them, (1) is glyphosate-containing phosphorus wastewater; (2) is malathion-containing phosphorus wastewater; (3) is trichlorfon-containing phosphorus wastewater; (4) is dimethoate-containing phosphorus wastewater; (5) is parathion-containing phosphorus wastewater; the reaction conditions are as follows: the dosage of the iron oxide / carbon nitride nanotube photocatalyst (Fe 2 O 3 @CNNTs) is 0.2 g / L, and the dosage of PMS is 1 mM; the concentrations of the above-mentioned organophosphorus pesticides are all 10 mg / L, the pH is 7, and the temperature is 25 °C;

[0074] After reacting for 45 min, the phosphorus-containing wastewater after the above degradation is detected, and the photocatalytic degradation rate results of each phosphorus-containing wastewater are as follows: glyphosate is 89.1% (see Figure 3 ), malathion is 84.7%, trichlorfon is 85.9%, dimethoate is 88.4%, and parathion is 87.7%; the adsorption amounts of the photocatalytic degradation products of inorganic phosphorus in each phosphorus-containing wastewater are as follows: glyphosate is 31.4 mg / g (see Figure 4 ), malathion is 28.3 mg / g, trichlorfon is 30.1 mg / g, dimethoate is 28.6 mg / g, and parathion is 27.7 mg / g.

[0075] Example 3

[0076] The preparation of the alumina / carbon nitride nanotube photocatalyst (Al 2 O 3 @CNNTs) in this example includes the following steps:

[0077] I. Using melamine and cyanuric acid as raw materials, self-assembling to form a melamine-cyanuric acid supramolecular polymer:

[0078] S11. Weigh 2 g of melamine and 2 g of cyanuric acid and dissolve them in 500 ml of deionized water respectively. Stir at 80 °C for about 10 minutes until completely dissolved to obtain a melamine solution and a cyanuric acid solution;

[0079] S12. Slowly add the melamine solution to the cyanuric acid solution that is being stirred evenly, perform the self-assembly of melamine and cyanuric acid, and self-assemble at 80 °C for 1 hour to form a melamine-cyanuric acid supramolecular polymer.

[0080] II. Preparation of the carbon nitride nanotube precursor:

[0081] S21. After centrifuging the solution that has completed the self-assembly reaction in step S12, wash it twice with deionized water at 80 °C to remove unassembled melamine and cyanuric acid, then filter it. The filtered product is redispersed in deionized water and precipitated at room temperature for 12 h. Remove the supernatant to obtain a flocculent precipitate;

[0082] S22. Freeze-dry the flocculent precipitate obtained in step S21 at -50 °C and 0.05 Mpa for 48 hours to obtain a carbon nitride nanotube precursor.

[0083] III. Preparation of carbon nitride nanotubes (CNNTs):

[0084] S3. Weigh 2 g of the carbon nitride nanotube precursor obtained in step S22 and introduce it into a covered ceramic crucible. Place it in a tubular furnace and calcine it under an argon atmosphere. As the temperature rises, the supramolecular polymer gradually thermally polycondenses into carbon nitride nanotubes CNNTs; among them, set the heating rate of the tubular furnace to 2 °C / min and the target temperature to 500 °C; when the temperature reaches 500 °C, maintain this temperature and calcine for 100 minutes.

[0085] IV. Preparation of alumina / carbon nitride nanotube photocatalyst (Al 2 O 3 @CNNTs):

[0086] S41. Weigh 1.0 g of the carbon nitride nanotubes obtained in step S3 and disperse them by magnetic stirring in 150 mL of methanol for 20 min. Then add 0.2 g of iron oxide nanoparticles to this solution while stirring. After the addition, continue to stir the mixture for 15 min. Further ultrasonically treat the obtained mixed solution. The ultrasonic conditions are: ultrasonic at 40 kHz for 45 min; after the ultrasonic treatment, dry it in an oven at 85 °C for 24 h;

[0087] S42. Grind and refine the powder obtained after drying in step S41, and then calcine it in a muffle furnace at 150 °C for 2 hours to obtain the alumina / carbon nitride nanotube photocatalyst Al 2 O 3 @CNNTs.

[0088] Use the above-prepared alumina / carbon nitride nanotube photocatalyst (Al 2 O 3 @CNNTs) to activate PMS to degrade organophosphorus (glyphosate, malathion, trichlorfon, dimethoate, parathion) pesticides; among them, (1) is glyphosate-containing phosphorus wastewater; (2) is malathion-containing phosphorus wastewater; (3) is trichlorfon-containing phosphorus wastewater; (4) is dimethoate-containing phosphorus wastewater; (5) is parathion-containing phosphorus wastewater; the reaction conditions are: alumina / carbon nitride nanotube photocatalyst (Al 2 O3 The dosage of @CNNTs was 0.4 g / L, and the dosage of PMS was 1.5 mM; the concentration of each of the above-mentioned organophosphorus pesticides was 10 mg / L, the pH was 7, and the temperature was 25 °C;

[0089] After reacting for 45 min, the phosphorus-containing wastewater after degradation was detected, and the photocatalytic degradation rate results of each phosphorus-containing wastewater were as follows: glyphosate was 90.1% (see Figure 3 ), malathion was 87.2%, trichlorfon was 84.0%, dimethoate was 87.9%, and parathion was 85.4%; the adsorption amounts of inorganic phosphorus, the photocatalytic degradation products of each phosphorus-containing wastewater, were as follows: glyphosate was 27.9 mg / g (see Figure 4 ), malathion was 28.6 mg / g, trichlorfon was 30.5 mg / g, dimethoate was 26.1 mg / g, and parathion was 29.3 mg / g.

[0090] Example 4

[0091] The preparation of the lanthanum oxide / carbon nitride nanotube photocatalyst (La 2 O 3 @CNNTs) in this example includes the following steps:

[0092] I. Using melamine and cyanuric acid as raw materials, self-assembling to form a melamine-cyanuric acid supramolecular polymer:

[0093] S11. Weigh 2 g of melamine and 2 g of cyanuric acid and dissolve them separately in 500 ml of deionized water. Stir at 80 °C for about 10 minutes until completely dissolved to obtain a melamine solution and a cyanuric acid solution;

[0094] S12. Slowly add the melamine solution to the cyanuric acid solution that is being stirred evenly for the self-assembly of melamine and cyanuric acid, and perform self-assembly at 80 °C for 1 hour to form a melamine-cyanuric acid supramolecular polymer.

[0095] II. Preparation of the carbon nitride nanotube precursor:

[0096] S21. After centrifuging the solution that has completed the self-assembly reaction in step S12, wash it 2 times with deionized water at 80 °C to remove unassembled melamine and cyanuric acid, then filter it. The filtered product is redispersed in deionized water and precipitated at room temperature for 12 h, and the supernatant is removed to obtain a flocculent precipitate;

[0097] S22. Freeze-dry the flocculent precipitate obtained in step S21 at -50 °C and 0.05 Mpa for 48 hours to obtain the carbon nitride nanotube precursor.

[0098] III. Preparation of carbon nitride nanotubes (CNNTs):

[0099] S3. Weigh 2 g of the carbon nitride nanotube precursor obtained in step S22, introduce it into a covered ceramic crucible, place it in a tube furnace, and calcine it under an argon atmosphere. As the temperature rises, the supramolecular polymer gradually undergoes thermal polycondensation to form carbon nitride nanotubes CNNTs. Among them, set the heating rate of the tube furnace to 2 °C / min and the target temperature to 500 °C. When the temperature reaches 500 °C, maintain this temperature and calcine for 100 minutes.

[0100] IV. Preparation of lanthanum oxide / carbon nitride nanotube photocatalyst (La 2 O 3 @CNNTs):

[0101] S41. Weigh 1.0 g of the carbon nitride nanotubes obtained in step S3 and disperse them by magnetic stirring in 150 mL of methanol for 20 min. Subsequently, add 0.2 g of lanthanum oxide nanoparticles to this solution while stirring. After the addition, continue to stir the mixture for 15 min. Further ultrasonically treat the resulting mixed solution. The ultrasonic conditions are: ultrasonic treatment at 40 kHz for 45 min. After the ultrasonic treatment, dry it in an oven at 85 °C for 24 h.

[0102] S42. Grind and refine the powder obtained after drying in step S41, and then place it in a muffle furnace and calcine it at 150 °C for 2 hours to obtain the lanthanum oxide / carbon nitride nanotube photocatalyst La 2 O 3 @CNNTs.

[0103] Use the above-prepared lanthanum oxide / carbon nitride nanotube photocatalyst (La 2 O 3 @CNNTs) to activate PMS for the degradation of organophosphorus (glyphosate, malathion, trichlorfon, dimethoate, parathion) pesticides. Among them, (1) is glyphosate-containing phosphorus wastewater; (2) is malathion-containing phosphorus wastewater; (3) is trichlorfon-containing phosphorus wastewater; (4) is dimethoate-containing phosphorus wastewater; (5) is parathion-containing phosphorus wastewater. The reaction conditions are: the dosage of the lanthanum oxide / carbon nitride nanotube photocatalyst (La 2 O 3 @CNNTs) is 0.4 g / L, and the dosage of PMS is 1.5 mM. The concentrations of the above organophosphorus pesticides are all 10 mg / L, the pH is 7, and the temperature is 25 °C.

[0104] After reacting for 45 min, detect the phosphorus-containing wastewater after the above degradation. The photocatalytic degradation rate results of each phosphorus-containing wastewater are as follows: glyphosate is 89.1% (see Figure 3), malathion was 84.2%, trichlorfon was 87.8%, dimethoate was 90.7%, and parathion was 87.5%; the adsorption amounts of inorganic phosphorus in the photocatalytic degradation products of each phosphorus-containing wastewater were as follows: glyphosate was 30.9 mg / g (see Figure 4 ), malathion was 28.7 mg / g, trichlorfon was 29.0 mg / g, dimethoate was 27.3 mg / g, and parathion was 28.7 mg / g.

[0105] Example 5

[0106] The preparation of the zirconia / carbon nitride nanotube photocatalyst (ZrO 2 @CNNTs) in this example includes the following steps:

[0107] I. Using melamine and cyanuric acid as raw materials, self-assembling to form a melamine-cyanuric acid supramolecular polymer:

[0108] S11. Weigh 2 g of melamine and 2 g of cyanuric acid and dissolve them in 500 ml of deionized water respectively. Stir at 80 °C for about 10 minutes until completely dissolved to obtain a melamine solution and a cyanuric acid solution;

[0109] S12. Slowly add the melamine solution to the cyanuric acid solution that is being stirred evenly for the self-assembly of melamine and cyanuric acid. Self-assemble at 80 °C for 1 hour to form a melamine-cyanuric acid supramolecular polymer.

[0110] II. Preparation of the carbon nitride nanotube precursor:

[0111] S21. After centrifuging the solution that has completed the self-assembly reaction in step S12, wash it twice with deionized water at 80 °C to remove unassembled melamine and cyanuric acid, then filter. The filtered product is redispersed in deionized water and precipitated at room temperature for 12 h. Remove the supernatant to obtain a flocculent precipitate;

[0112] S22. Freeze-dry the flocculent precipitate obtained in step S21 at -50 °C and 0.05 Mpa for 48 hours to obtain the carbon nitride nanotube precursor.

[0113] III. Preparation of carbon nitride nanotubes (CNNTs):

[0114] S3. Weigh 2 g of the carbon nitride nanotube precursor obtained in step S22 and introduce it into a covered ceramic crucible. Place it in a tubular furnace and calcine it under an argon atmosphere. As the temperature rises, the supramolecular polymer gradually thermally polycondenses into carbon nitride nanotubes CNNTs; among them, set the heating rate of the tubular furnace to 2 °C / min and the target temperature to 500 °C; when the temperature reaches 500 °C, maintain this temperature and calcine for 100 minutes.

[0115] IV. Preparation of Zirconia / Carbon Nitride Nanotube Photocatalyst (ZrO 2 @CNNTs):

[0116] S41. Weigh 1.0 g of the carbon nitride nanotubes obtained in step S3 and disperse them by magnetic stirring in 150 mL of methanol for 20 min. Subsequently, add 0.2 g of zirconia nanoparticles to this solution while stirring. After the addition, continue to stir the mixture for 15 min. Further ultrasonic treat the resulting mixed solution under the ultrasonic conditions: ultrasonic for 45 min at 40 kHz; after the ultrasonic treatment, dry it in an oven at 85 °C for 24 h;

[0117] S42. Grind and refine the powder obtained after drying in step S41, and then calcine it in a muffle furnace at 150 °C for 2 hours to obtain the zirconia / carbon nitride nanotube photocatalyst ZrO 2 @CNNTs.

[0118] Use the above-prepared zirconia / carbon nitride nanotube photocatalyst (ZrO 2 @CNNTs) to activate PMS for degrading organophosphorus (glyphosate, malathion, trichlorfon, dimethoate, parathion) pesticides; among them, (1) is glyphosate-containing phosphorus wastewater; (2) is malathion-containing phosphorus wastewater; (3) is trichlorfon-containing phosphorus wastewater; (4) is dimethoate-containing phosphorus wastewater; (5) is parathion-containing phosphorus wastewater; the reaction conditions are: the dosage of zirconia / carbon nitride nanotube photocatalyst (ZrO 2 @CNNTs) is 0.4 g / L, and the dosage of PMS is 1.5 mM; the concentrations of the above various organophosphorus pesticides are all 10 mg / L, the pH is 7, and the temperature is 25 °C;

[0119] After reacting for 45 min, detect the phosphorus-containing wastewater after the above degradation. The photocatalytic degradation rate results of each phosphorus-containing wastewater are as follows: glyphosate is 87.9% (see Figure 3 ), malathion is 86.5%, trichlorfon is 89.7%, dimethoate is 91.2%, and parathion is 89.3%; the adsorption amounts of the photocatalytic degradation products of inorganic phosphorus in each phosphorus-containing wastewater are as follows: glyphosate is 30.9 mg / g (see Figure 4 ), malathion is 29.4 mg / g, trichlorfon is 27.5 mg / g, dimethoate is 29.9 mg / g, and parathion is 28.6 mg / g.

[0120] Comparative Example 1

[0121] This comparative example uses carbon nitride nanotube photocatalyst (CNNTs) to activate PMS for degrading organophosphorus (glyphosate, malathion, trichlorfon, dimethoate, parathion) pesticides:

[0122] The preparation of the carbon nitride nanotube photocatalyst (CNNTs) in this comparative example includes the following steps:

[0123] I. Using melamine and cyanuric acid as raw materials, self-assembling to form a melamine-cyanuric acid supramolecular polymer:

[0124] S11. Weigh 2 g of melamine and 2 g of cyanuric acid and dissolve them separately in 500 ml of deionized water. Stir at 80 °C for about 10 minutes until completely dissolved to obtain a melamine solution and a cyanuric acid solution.

[0125] S12. Slowly add the melamine solution to the cyanuric acid solution that is being stirred evenly for the self-assembly of melamine and cyanuric acid. Carry out self-assembly at 80 °C for 1 hour to form a melamine-cyanuric acid supramolecular polymer.

[0126] II. Preparation of the carbon nitride nanotube precursor:

[0127] S21. After centrifuging the solution that has completed the self-assembly reaction in step S12, wash it twice with deionized water at 80 °C to remove unassembled melamine and cyanuric acid. Then carry out filtration. The filtered product is redispersed in deionized water and precipitated at room temperature for 12 h. Remove the supernatant to obtain a flocculent precipitate.

[0128] S22. Freeze-dry the flocculent precipitate obtained in step S21 at -50 °C and 0.05 Mpa for 48 hours to obtain the carbon nitride nanotube precursor.

[0129] III. Preparation of the carbon nitride nanotube photocatalyst (CNNTs):

[0130] S3. Weigh 2 g of the carbon nitride nanotube precursor obtained in step S22 and introduce it into a covered ceramic crucible. Place it in a tubular furnace and calcine it under an argon atmosphere. As the temperature rises, the supramolecular polymer gradually thermally polycondenses into the carbon nitride nanotube photocatalyst CNNTs. Among them, set the heating rate of the tubular furnace to 2 °C / min and the target temperature to 500 °C. When the temperature reaches 500 °C, maintain this temperature and calcine for 100 minutes.

[0131] Use the above-prepared carbon nitride nanotube photocatalyst (CNNTs) to activate PMS to degrade organophosphorus (glyphosate, malathion, trichlorfon, dimethoate, parathion) pesticides. Among them, (1) is glyphosate-containing phosphorus wastewater; (2) is malathion-containing phosphorus wastewater; (3) is trichlorfon-containing phosphorus wastewater; (4) is dimethoate-containing phosphorus wastewater; (5) is parathion-containing phosphorus wastewater. The reaction conditions are as follows: the dosage of the carbon nitride nanotube photocatalyst (CNNTs) is 0.4 g / L, the dosage of PMS is 1.5 mM; the concentration of each of the above organophosphorus pesticides is 10 mg / L, the pH is 7, and the temperature is 25 °C.

[0132] After 45 minutes of reaction, the phosphorus-containing wastewater after the above degradation was detected, and the photocatalytic degradation rate results of each phosphorus-containing wastewater were as follows: glyphosate was 70.9% (see Figure 3 ), malathion was 64.2%, trichlorfon was 47.0%, dimethoate was 74.9%, parathion was 74.0%; the adsorption amounts of inorganic phosphorus, the photocatalytic degradation products of each phosphorus-containing wastewater, were as follows: glyphosate was 2.8 mg / g (see Figure 4 ), malathion was 5.4 mg / g, trichlorfon was 1.5 mg / g, dimethoate was 0.9 mg / g, parathion was 3.9 mg / g.

[0133] Comparative Example 2

[0134] In this comparative example, magnesium oxide was used to activate PMS to degrade organophosphorus (glyphosate, malathion, trichlorfon, dimethoate, parathion) pesticides:

[0135] Magnesium oxide was used to activate PMS to degrade organophosphorus (glyphosate, malathion, trichlorfon, dimethoate, parathion) pesticides; among them, (1) was phosphorus-containing wastewater of glyphosate; (2) was phosphorus-containing wastewater of malathion; (3) was phosphorus-containing wastewater of trichlorfon; (4) was phosphorus-containing wastewater of dimethoate; (5) was phosphorus-containing wastewater of parathion; the reaction conditions were: the dosage of magnesium oxide was 0.4 g / L, and the dosage of PMS was 1.5 mM; the concentrations of the above organophosphorus pesticides were all 10 mg / L, pH was 7, and the temperature was 25 °C;

[0136] After 45 minutes of reaction, the phosphorus-containing wastewater after the above degradation was detected, and the photocatalytic degradation rate results of each phosphorus-containing wastewater were as follows: glyphosate was 18.7% (see Figure 3 ), malathion was 9.8%, trichlorfon was 11.2%, dimethoate was 4.0%, parathion was 14.6%; the adsorption amounts of inorganic phosphorus, the photocatalytic degradation products of each phosphorus-containing wastewater, were as follows: glyphosate was 30.0 mg / g (see Figure 4 ), malathion was 43.5 mg / g, trichlorfon was 35.7 mg / g, dimethoate was 42.3 mg / g, parathion was 47.9 mg / g.

[0137] Comparative Example 3

[0138] In this comparative example, no photocatalyst was added, and PMS was used to directly oxidize and degrade organophosphorus (glyphosate, malathion, trichlorfon, dimethoate, parathion) pesticides; among them, (1) was phosphorus-containing wastewater of glyphosate; (2) was phosphorus-containing wastewater of malathion; (3) was phosphorus-containing wastewater of trichlorfon; (4) was phosphorus-containing wastewater of dimethoate; (5) was phosphorus-containing wastewater of parathion; the reaction conditions were: the dosage of PMS was 1.5 mM; the concentrations of the above organophosphorus pesticides were all 10 mg / L, pH was 7, and the temperature was 25 °C;

[0139] After 45 minutes of reaction, the degraded phosphorus-containing wastewater was detected, and the degradation rate results of each phosphorus-containing wastewater were as follows: glyphosate was 6.7% (see Figure 3 ), malathion was 12.1%, trichlorfon was 8.3%, dimethoate was 3.9%, and parathion was 7.1%; the adsorption amounts of inorganic phosphorus, the photocatalytic degradation product of each phosphorus-containing wastewater, were as follows: glyphosate was 0 mg / g (see Figure 4 ), malathion was 0 mg / g, trichlorfon was 0 mg / g, dimethoate was 0 mg / g, and parathion was 0 mg / g.

[0140] Comparing Figure 3 and Figure 4 with the degradation rate data and adsorption amount data of glyphosate in Examples 1-5 and Comparative Examples 1-3, it can be seen that the zirconia / carbon nitride nanotube photocatalyst and its preparation method provided by the present invention are used for the deep purification of phosphorus-containing wastewater. By ultrasonic-assisted co-blending-calcination method, metal oxides (MgO, Fe 2 O 3 , Al 2 O 3 , La 2 O 3 , ZrO 2 ) were loaded on carbon nitride nanotubes to construct a composite photocatalyst, significantly improving the photocatalytic performance of carbon nitride nanotubes (CNNTs), and enabling efficient degradation of organophosphorus pesticides and in-situ adsorption and mineralization of the product inorganic phosphorus.

[0141] The above embodiments are only for illustrating the technical concept and features of the present invention, and the purpose is to enable those familiar with this technology to understand the content of the present invention and implement it accordingly, and it cannot be used to limit the protection scope of the present invention. Any equivalent transformation or modification made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for preparing a metal oxide / carbon nitride nanotube photocatalyst, characterized in that: The following steps are involved: S1. Using melamine and cyanuric acid as raw materials, self-assembly forms melamine-cyanuric acid supramolecular polymer; S2. removing the unassembled melamine and cyanuric acid in step S1 to obtain a supramolecular polymer flocculent precipitate, and freeze-drying the supramolecular polymer flocculent precipitate to obtain a carbon nitride nanotube precursor; S3. The carbon nitride nanotube precursor obtained in step S2 is calcined under an argon atmosphere to obtain carbon nitride nanotubes; S4. Ultrasonic dispersion treatment is performed on the metal oxide and the carbon nitride nanotubes obtained in step S3 in a methanol solution. After drying, the obtained powder is ground and calcined to obtain a metal oxide / carbon nitride nanotube photocatalyst; wherein the metal oxide is one or more of MgO, Fe2O3, Al2O3, La2O3, and ZrO2.

2. The method for preparing the metal oxide / carbon nitride nanotube photocatalyst according to claim 1, characterized in that: The preparation of the supramolecular polymer in step S1 specifically comprises the following steps: S11. Weigh melamine and cyanuric acid in a mass ratio of melamine: cyanuric acid = 1:1 to 1.2, dissolve them in deionized water and stir until completely dissolved to obtain a melamine solution and a cyanuric acid solution; S12. Slowly adding the melamine solution into the uniformly stirred cyanuric acid solution to carry out self-assembly of melamine and cyanuric acid to form a melamine-cyanuric acid supramolecular polymer.

3. The method for preparing the metal oxide / carbon nitride nanotube photocatalyst according to claim 2, characterized in that: In step S12, the self-assembly conditions of melamine and cyanuric acid are: assembling at 70-90° C. for 1-2 hours.

4. The method for preparing the metal oxide / carbon nitride nanotube photocatalyst according to claim 1, characterized in that: The preparation of the carbon nanotube nitride precursor in step S2 specifically includes the following steps: S21. After the solution in step S12 in which the self-assembly reaction is completed is centrifuged, it is washed 2 to 4 times with deionized water at 70 to 90° C. to remove unassembled melamine and cyanuric acid, and then filtered. The filtered product is redispersed in deionized water, precipitated at room temperature for 12 to 15 hours, and the supernatant is removed to obtain a flocculent precipitate; S22. Freeze-dry the flocculent precipitate obtained in step S21 to obtain a carbon nitride nanotube precursor.

5. The method for preparing the metal oxide / carbon nitride nanotube photocatalyst according to claim 4, characterized in that: In step S22, the conditions for freeze drying the flocculent precipitate are: -40 to -80°C, 0.05 to 0.1 MPa, and freeze drying for 40 to 48 hours.

6. The method for preparing the metal oxide / carbon nitride nanotube photocatalyst according to claim 1, characterized in that: The preparation of carbon nitride nanotubes in step S3 specifically includes the following steps: placing the carbon nitride nanotube precursor obtained in step S22 in a tubular furnace and calcining at 500-550° C. for 2-3 hours under an argon atmosphere, and as the temperature rises, the supramolecular polymer gradually thermally shrinks into carbon nitride nanotubes; wherein the heating rate of the tubular furnace is 2° C. / min.

7. The method for preparing the metal oxide / carbon nitride nanotube photocatalyst according to claim 1, characterized in that: The preparation of the metal oxide / carbon nitride nanotube photocatalyst in step S4 specifically comprises the following steps: S41. Weigh a certain amount of carbon nitride nanotubes and disperse them in methanol by stirring, then add a certain amount of metal oxide nanoparticles to the solution, stir while adding, continue stirring and mixing for 10 to 20 minutes after the addition is completed, and further ultrasonically treat the obtained mixed solution under the ultrasonic conditions of: ultrasonication at 40 to 80 kHz for 40 to 60 minutes; after the ultrasonication is completed, dry at 80 to 90° C. for 20 to 25 hours; S42. Grind the powder obtained after drying in step S41 into fine powder, and then place it in a muffle furnace and calcine it at 120-150° C. for 2-3 hours to obtain a metal oxide / carbon nitride nanotube photocatalyst.

8. The method for preparing the metal oxide / carbon nitride nanotube photocatalyst according to claim 7, characterized in that: In the step S41, the mass ratio of the metal oxide to the carbon nitride nanotubes is 1:4-5.

9. A metal oxide / carbon nitride nanotube photocatalyst, characterized in that: The photocatalyst is prepared according to the method for preparing the metal oxide / carbon nitride nanotube photocatalyst according to any one of claims 1 to 8.

10. Use of a metal oxide / carbon nitride nanotube photocatalyst in deep purification of phosphorus-containing wastewater, wherein the metal oxide / carbon nitride nanotube photocatalyst is the metal oxide / carbon nitride nanotube photocatalyst according to claim 9 or is prepared by the preparation method of the metal oxide / carbon nitride nanotube photocatalyst according to any one of claims 1 to 8.

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