Method for preparing TiO2 / g-C3N4 / BN composite photocatalyst by electrospinning and application thereof

Abstract

The application belongs to the field of photocatalysis, and relates to a method for preparing a TiO2 / g-C3N4 / BN composite photocatalyst by electrospinning and application. BN quantum dots, carbon-nitrogen precursors, butyl titanate and polymers are matched into an outer layer spinning solution, an oil substance is used as an inner layer spinning solution, a skin-core composite fiber is prepared by coaxial electrospinning, and the TiO2 / g-C3N4 / BN composite photocatalyst is obtained after solvent washing and calcination. The method is simple in process, convenient in operation and low in cost. The nano-fiber structure prepared by electrospinning is helpful for rapid migration of electrons, weakening of the combination of holes and photo-generated electrons, and improvement of catalytic performance. Compared with a common TiO2 powder catalyst, the composite photocatalyst prepared by the application has a large specific surface area, effectively improves adsorption capacity, enhances degradation capacity of pollutants in water, and has high catalyst quantum efficiency, can be repeatedly used, and has good photocatalytic degradation capacity of organic sewage.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of photocatalysis, and relates to a method for preparing a TiO2 / g-C3N4 / BN composite photocatalyst by electrospinning and application thereof. BACKGROUND

[0002] TiO2 has excellent photoelectric performance and photocatalytic performance, good weather resistance, corrosion resistance and chemical stability, and is a common semiconductor material. However, its wide band gap and high photoelectron-hole recombination rate can only utilize a small proportion of visible light and ultraviolet light, which seriously hinders its development in the field of photocatalysis. As a metal-free photocatalyst, g-C3N4 is non-toxic, pollution-free, has good thermal stability and chemical stability, and is cheap and easy to obtain, and is highly concerned in the fields of photoelectricity and catalysis. Huang Xiaozhen et al. prepared a spinning solution by mixing butyl titanate and g-C3N4, calcined after electrospinning, and obtained a TiO2 / g-C3N4 photocatalytic material (Preparation and photocatalytic performance of coaxial electrospun TiO2 / g-C3N4[J]. Chemical Industry and Engineering, 2021, 38(05): 35-41.). Patent CN107456987A discloses a method for preparing a carbon nitride / titanium dioxide heterojunction photocatalyst by electrospinning one-step method, a carbon-nitrogen precursor such as melamine, guanidine hydrochloride or urea and butyl titanate are mixed to prepare a spinning solution, and a carbon nitride / titanium dioxide heterojunction photocatalyst is obtained after electrospinning and calcination. Although the combination of g-C3N4 and TiO2 can improve the catalytic activity of TiO2 to a certain extent, these catalysts still have weak visible light absorption, and photoelectrons and holes are easy to recombine, resulting in low utilization rate of visible light. SUMMARY

[0003] In view of the above technical problems, the application provides a method for preparing a TiO2 / g-C3N4 / BN composite photocatalyst by electrospinning and application thereof. The method is simple in process, easy to operate and low in cost, and the prepared TiO2 / g-C3N4 / BN composite photocatalyst has good photocatalytic degradation capacity for organic wastewater.

[0004] In order to achieve the above purpose, the technical scheme of the application is as follows:

[0005] A method for preparing a TiO2 / g-C3N4 / BN composite photocatalyst by electrospinning, comprising the following steps:

[0006] (1) BN quantum dot preparation: 0.4 g of BN powder is added in 50 mL of organic solvent (volume ratio of N,N-dimethylformamide to anhydrous ethanol is 1.25:1), ultrasonic crushing is performed for 6 h with an output power of 600 W to peel the BN powder into nanosheets, N2 degassing is performed for 30 min to remove oxygen in the dispersion liquid, the dispersion liquid is degassed to a high-pressure kettle with a filling factor of 2 / 3, solvent thermal treatment is performed at 180°C in a vacuum drying box for 12 h, natural cooling is performed to room temperature, the obtained suspension is centrifuged at 10000 rpm for 5 min, the precipitate is removed, the supernatant containing BN quantum dots is collected and freeze-dried to obtain BN quantum dots;

[0007] (2) Spinning solution preparation: 0.003-0.02 g of BN quantum dots is added in 10-20 mL of organic solvent, ultrasonic stirring is performed to uniformly disperse the BN quantum dots in the solution, 0.5-2 g of carbon-nitrogen precursor, 0.6-2 g of glacial acetic acid, 2-4 g of butyl titanate and 0.6-3 g of polymer are added, ultrasonic stirring is performed to obtain an outer layer spinning solution; and an oil substance is used as an inner layer spinning solution;

[0008] (3) Coaxial electrospinning: the outer layer spinning solution and the inner layer spinning solution are connected to the outer layer and the inner layer of a coaxial needle respectively, the ratio of the feeding rate of the inner layer spinning solution to the feeding rate of the outer layer spinning solution in the electrospinning process is adjusted to 1:(1-9), and the total feeding rate is 0.3-6 mL / h, meanwhile, the coaxial needle is connected to a high-voltage static generator to perform electrospinning, the spun fibers are received by a roller or a flat plate to obtain a skin-core composite fiber;

[0009] (4) Inner layer removal: the skin-core composite fiber is placed in a solvent for 12-48 h of washing, the inner layer substance is removed, and drying is performed to obtain a composite fiber;

[0010] (5) Calcination to prepare carbon nitride: the composite fiber is heated to 500-600°C in air or oxygen, reaction is performed for 3-8 h, natural cooling is performed to room temperature, and a TiO2 / g-C3N4 / BN composite photocatalyst is obtained.

[0011] Further, the organic solvent in the step (2) is a mixed solvent with a volume ratio of N,N-dimethylformamide to anhydrous ethanol being 1.25:1.

[0012] Further, the carbon-nitrogen precursor in the step (2) is any one or a combination of multiple of urea, melamine, dicyandiamide or thiourea.

[0013] Further, the polymer in the step (2) is any one or multiple of polyvinylpyrrolidone, polyethylene oxide, polyethylene glycol or polymethyl methacrylate.

[0014] Further, the total mass of BN quantum dots, carbon-nitrogen precursor powder, glacial acetic acid, butyl titanate and polymer in the outer layer spinning solution in the step (2) is 15-35% of the total mass of the outer layer spinning solution.

[0015] Further, the inner layer spinning solution in the step (3) is an oil substance, and the oil substance is any one or a combination of mineral oil, dimethyl silicone oil or edible oil.

[0016] Further, the pressure of the high-voltage electrostatic generator in the step (3) is 17-18 kV, and the receiving distance is 15 cm.

[0017] Further, the solvent in the step (4) is any one or a combination of n-octane, n-hexane or turpentine.

[0018] Further, the TiO2 / g-C3N4 / BN composite photocatalyst prepared by the above method.

[0019] Further, the application of the TiO2 / g-C3N4 / BN composite photocatalyst in photocatalytic degradation of dye wastewater.

[0020] The present application has the following beneficial effects:

[0021] 1. The application prepares a sheath-core composite fiber by using coaxial electrospinning, with BN quantum dots, carbon-nitrogen precursors such as melamine, and butyl titanate and polymers being prepared into an outer layer spinning solution, and an oil substance being used as an inner layer spinning solution; the inner layer substance is removed by washing in a solvent such as n-octane to obtain a composite fiber; and after calcination, a porous TiO2 / g-C3N4 / BN composite photocatalyst is obtained. In the application, firstly, the presence of glacial acetic acid makes the carbon-nitrogen precursors such as melamine more easily dissolved. Secondly, the nanofiber structure prepared by electrospinning helps the rapid migration of electrons, weakens the recombination of holes and photo-generated electrons, and thus improves the catalytic performance. Thirdly, during the calcination process, the carbon-nitrogen precursors and butyl titanate are subjected to high temperature to form TiO2 and g-C3N4, and the heterojunction formed between the two phases changes the TiO2 band gap and enhances the utilization rate of sunlight of the composite material. Then, the polymers such as polyvinylpyrrolidone uniformly distributed in the sample undergo thermal decomposition during the calcination process, resulting in the formation of a large number of pores on the fiber surface. The porous material has many advantages, such as the multiple scattering in the pores enhancing the light trapping ability of the mesoporous material, and the porous structure promoting the migration of electrons and inhibiting the recombination of carriers. Finally, h-BN is a wide-bandgap semiconductor material, which has good chemical stability, high temperature resistance, and high thermal conductivity, and other characteristics that traditional catalyst carriers do not have. After being prepared into BN quantum dots, due to the existence of nitrogen vacancies or carbon impurity defects on the surface of the BN quantum dots, the surface negative charge of the BN quantum dots attracts photo-generated holes after being combined with the semiconductor, increasing the separation efficiency of the photo-generated electron-hole pairs of the semiconductor and reducing the recombination probability of the electrons and holes, and finally a porous TiO2 / g-C3N4 / BN composite photocatalyst with high catalytic efficiency is prepared.

[0022] 2. The specific surface area of the nanofiber structure prepared by the electrospinning of the application is as high as 367.8 m 2 / g, which is much higher than the 50 m 2 / g of the TiO2 / g-C3N4 fiber photocatalyst prepared in the related reports. The larger specific surface area provides a large number of surface active sites for adsorption and photocatalytic reaction. And the addition of BN quantum dots significantly narrows the band gap of TiO2 / g-C3N4, making Eg change from 2.81 eV to 2.53 eV. Obviously, the TiO2 / g-C3N4 / BN composite material prepared in the application can absorb more visible light, which helps to improve the photocatalytic activity of the composite material.

[0023] 3、The preparation method provided by the application has simple process, convenient operation and low cost, the prepared catalyst has high quantum efficiency, can be repeatedly used and has good ability of photocatalytic degradation of organic sewage. 50 mg of the catalyst is added into 50 mL of a rhodamine B aqueous solution containing 30 mg / L, and photocatalytic degradation is carried out, the degradation rate is 95.7% after irradiation for 120 min, and the degradation efficiency is about 85% after the catalyst is repeatedly used for 5 times, and the repeatability is good. 50 mg of the catalyst is added into 50 mL of a rhodamine B aqueous solution containing 10 mg / L, and photocatalytic degradation is carried out, the degradation rate is 98.3% after irradiation for 40 min; 50 mg of the catalyst is added into 50 mL of a methyl orange solution containing 30 mg / L, and the degradation rate is 96% after 50 min. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative effort on the basis of these drawings.

[0025] Figure 1 The effect diagram of the photocatalyst prepared in the application example 1, the comparative example 1 and the comparative example 2 on degrading 30 mg / L rhodamine B.

[0026] Figure 2 The recycling effect diagram of the TiO2 / g-C3N4 / BN photocatalyst prepared in the application example 1.

[0027] Figure 3 The N2 adsorption-desorption isotherm of the TiO2 / g-C3N4 / BN photocatalyst prepared in the application example 1.

[0028] Figure 4 The pore size distribution diagram of the TiO2 / g-C3N4 / BN photocatalyst prepared in the application example 1.

[0029] Figure 5 The ultraviolet-visible spectrum of the photocatalyst prepared in the application example 1, the comparative example 1 and the comparative example 2.

[0030] Figure 6 The band gap calculation diagram of the photocatalyst prepared in the application example 1, the comparative example 1 and the comparative example 2.

[0031] Figure 7 The effect diagram of the photocatalyst prepared in the application example 1, the comparative example 1 and the comparative example 2 on degrading 10 mg / L rhodamine B.

[0032] Figure 8 Figure of the effect of the photocatalyst prepared for Example 1, Comparative Example 1 and Comparative Example 2 on the degradation of 30 mg / L methyl orange. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present application will be apparently and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without any creative effort fall within the protection scope of the present application.

[0034] In the present application, the raw materials used in the following embodiments are commercially available products, unless otherwise specified.

[0035] The preparation method of BN quantum dots is as follows: 0.4 g of BN powder is added into 50 mL of organic solvent (N,N-dimethylformamide and anhydrous ethanol in a volume ratio of 1.25:1), and ultrasonic crushing is performed for 6 h at an output power of 600 W to peel the BN powder into nanosheets. The dispersion liquid is degassed for 30 min with N2 to remove oxygen in the dispersion liquid. The dispersion liquid is degassed into an autoclave at a filling factor of 2 / 3. The solvent is thermally treated at 180 ℃ in a vacuum drying box for 12 h, and naturally cooled to room temperature. The obtained suspension is centrifuged at 10,000 rpm for 5 min, and the precipitate is removed. The supernatant containing BN quantum dots is collected and freeze-dried to obtain BN quantum dots.

[0036] Example 1

[0037] The present embodiment is a preparation method of TiO2 / g-C3N4 / BN composite photocatalyst, and the steps are as follows:

[0038] The preparation method of TiO2 / g-C3N4 / BN composite photocatalyst is as follows: 0.005 g of BN quantum dots is added into 15 mL of organic solvent (a mixed solution of N,N-dimethylformamide and anhydrous ethanol in a volume ratio of 1.25:1), and ultrasonic stirring is performed to disperse uniformly. 0.6 g of urea is added, and then 1.2 mL of glacial acetic acid, 3 g of butyl titanate and 1.2 g of polyvinylpyrrolidone are added. Ultrasonic stirring is performed to obtain a uniform outer solution. Dimethyl silicone oil is used as an inner spinning solution. The outer solution and the inner solution are respectively input into the outer layer and the inner layer of a coaxial needle. The coaxial needle is connected to a high-voltage electrostatic generator at 17 kV, and the receiving distance is 15 cm. The supply of the inner spinning solution and the outer spinning solution is 0.4 mL / h and 1.8 mL / h, respectively. The fiber is received by a drum, dried, and a skin-core composite fiber is obtained. The skin-core composite fiber is treated with n-octane for 24 h, and then air-dried. The temperature is slowly increased from room temperature to 550 ℃, and then kept for 4 h. The temperature is naturally cooled to room temperature, and finally TiO2 / g-C3N4 / BN composite photocatalyst is obtained.

[0039] Example 2

[0040] The present embodiment is a preparation method of a TiO2 / g-C3N4 / BN composite photocatalyst, and the steps are as follows:

[0041] 0.003 g BN quantum dots were added to 16 mL of an organic solvent (a mixed solution of N,N-dimethylformamide and ethanol with a volume ratio of 1.25:1), ultrasonically stirred and dispersed uniformly, 0.9 g of melamine was added, and then 0.6 mL of glacial acetic acid, 2.2 g of butyl titanate and 0.8 g of polyvinylpyrrolidone were added, ultrasonically stirred and dispersed uniformly to obtain a uniform outer solution; dimethyl silicone oil was used as an inner spinning solution. The outer solution and the inner solution were respectively input into the outer layer and the inner layer of a coaxial needle, the supply of the inner spinning solution and the outer spinning solution was set to 0.6 mL / h and 2.8 mL / h respectively, the coaxial needle was connected to a high-voltage electrostatic generator of 18 kV, the receiving distance was 15 cm, and the fiber was received by a drum, dried, and a sheath-core composite fiber was obtained. The sheath-core composite fiber was treated with n-octane for 24 h, air-dried, slowly heated from room temperature to 550 ℃, kept for 4 h, naturally cooled to room temperature, and finally a TiO2 / g-C3N4 / BN composite photocatalyst was obtained.

[0042] Example 3

[0043] The present embodiment is a preparation method of a TiO2 / g-C3N4 / BN composite photocatalyst, and the steps are as follows:

[0044] 0.007 g BN quantum dots were added to 15 mL of an organic solvent (a mixed solution of N,N-dimethylformamide and ethanol with a volume ratio of 1.25:1), ultrasonically stirred and dispersed uniformly, 1.0 g of melamine was added, and then 0.8 mL of glacial acetic acid, 2.5 g of butyl titanate and 0.9 g of polyvinylpyrrolidone were added, ultrasonically stirred and dispersed uniformly to obtain a uniform outer solution; dimethyl silicone oil was used as an inner spinning solution; the outer solution and the inner solution were respectively input into the outer layer and the inner layer of a coaxial needle, the supply of the inner spinning solution and the outer spinning solution was set to 0.4 mL / h and 2.7 mL / h respectively, the coaxial needle was connected to a high-voltage electrostatic generator of 17 kV, the receiving distance was 15 cm, and the fiber was received by a drum, and a sheath-core composite fiber was obtained. The sheath-core composite fiber was treated with n-octane for 24 h, air-dried, slowly heated from room temperature to 540 ℃, kept for 4 h, naturally cooled to room temperature, and finally a TiO2 / g-C3N4 / BN composite photocatalyst was obtained.

[0045] Example 4

[0046] The present embodiment is a preparation method of a TiO2 / g-C3N4 / BN composite photocatalyst, and the steps are as follows:

[0047] 0.009 g BN quantum dots were added to 16 mL of organic solvent (a mixed solution of N,N-dimethylformamide and ethanol with a volume ratio of 1.25:1), ultrasonic stirring was performed to disperse uniformly, 1.8 g of carbon-nitrogen precursor (equal mass of thiourea and urea) was added, and then 1.0 mL of glacial acetic acid, 2.5 g of butyl titanate and 1.0 g of polyvinylpyrrolidone were added, ultrasonic stirring was performed to obtain a uniform outer solution; dimethyl silicone oil was used as the inner spinning solution; the outer solution and the inner solution were respectively input into the outer layer and the inner layer of a coaxial needle, the supply of the inner spinning solution and the outer spinning solution was set to 0.5 mL / h and 2.8 mL / h respectively, the coaxial needle was connected to a high-voltage electrostatic generator of 17 kV, the receiving distance was 15 cm, and the drum received the fiber to obtain a sheath-core composite fiber. The sheath-core composite fiber was treated with n-octane for 24 h, and then air-dried, slowly heated from room temperature to 520 ℃, kept for 4 h, naturally cooled to room temperature, and finally TiO2 / g-C3N4 / BN composite photocatalyst was obtained.

[0048] Example 5

[0049] This example is a preparation method of TiO2 / g-C3N4 / BN composite photocatalyst, and the steps are as follows:

[0050] 0.01 g BN quantum dots were added to 14 mL of organic solvent (a mixed solution of N,N-dimethylformamide and ethanol with a volume ratio of 1.25:1), ultrasonic stirring was performed to disperse uniformly, 0.9 g of dicyandiamide was added, and then 0.6 mL of glacial acetic acid, 3 g of butyl titanate and 0.6 g of polyethylene oxide were added, ultrasonic stirring was performed to obtain a uniform outer solution; mineral oil was used as the inner spinning solution; the outer solution and the inner solution were respectively input into the outer layer and the inner layer of a coaxial needle, the supply of the inner spinning solution and the outer spinning solution was set to 0.6 mL / h and 2.8 mL / h respectively, the coaxial needle was connected to a high-voltage electrostatic generator of 18 kV, the receiving distance was 15 cm, and the drum received the fiber to obtain a sheath-core composite fiber. The sheath-core composite fiber was treated with turpentine for 12 h, and then air-dried, slowly heated from room temperature to 600 ℃, kept for 3 h, naturally cooled to room temperature, and finally TiO2 / g-C3N4 / BN composite photocatalyst was obtained.

[0051] Example 6

[0052] This example is a preparation method of TiO2 / g-C3N4 / BN composite photocatalyst, and the steps are as follows:

[0053] 0.012 g BN quantum dots were added to 14 mL of organic solvent (a mixed solution of N,N-dimethylformamide and ethanol with a volume ratio of 1.25:1), ultrasonic stirring was performed to disperse uniformly, 0.8 g (equal mass of urea, dicyandiamide and thiourea which were ground uniformly) was added, then 0.6 mL of glacial acetic acid, 2.2 g of butyl titanate and 0.6 g of polyethylene glycol were added, ultrasonic stirring was performed to obtain a uniform outer solution; edible oil was used as the inner spinning solution; the outer solution and the inner solution were respectively input into the outer layer and the inner layer of a coaxial needle, the liquid supply of the inner spinning solution and the outer spinning solution was set to 0.5 mL / h and 2.1 mL / h respectively, the coaxial needle was connected to a high-voltage electrostatic generator of 18 kV, the receiving distance was 15 cm, and the fibers were received by a drum to obtain a sheath-core composite fiber. The sheath-core composite fiber was treated with turpentine oil for 12 h, air-dried, slowly heated from room temperature to 600 ℃, kept for 3 h, naturally cooled to room temperature, and finally TiO2 / g-C3N4 / BN composite photocatalyst was obtained.

[0054] Example 7

[0055] The present example is a preparation method of TiO2 / g-C3N4 / BN composite photocatalyst, and the steps are as follows:

[0056] 0.014 g BN quantum dots were added to 13 mL of organic solvent (a mixed solution of N,N-dimethylformamide and ethanol with a volume ratio of 1.25:1), ultrasonic stirring was performed to disperse uniformly, 0.6 g (equal mass of urea, thiourea and dicyandiamide which were ground uniformly) was added, then 0.8 mL of glacial acetic acid, 2 g of butyl titanate and 0.7 g of polymethyl methacrylate were added, ultrasonic stirring was performed to obtain a uniform outer solution; dimethyl silicone oil was used as the inner spinning solution; the outer solution and the inner solution were respectively input into the outer layer and the inner layer of a coaxial needle, the liquid supply of the inner spinning solution and the outer spinning solution was set to 0.3 mL / h and 2.6 mL / h respectively, the coaxial needle was connected to a high-voltage electrostatic generator of 18 kV, the receiving distance was 15 cm, and the fibers were received by a drum to obtain a sheath-core composite fiber. The sheath-core composite fiber was treated with n-octane for 48 h, air-dried, slowly heated from room temperature to 500 ℃, kept for 3 h, naturally cooled to room temperature, and finally TiO2 / g-C3N4 / BN composite photocatalyst was obtained.

[0057] Example 8

[0058] The present example is a preparation method of TiO2 / g-C3N4 / BN composite photocatalyst, and the steps are as follows:

[0059] 0.016 g BN quantum dots were added to 19 mL of organic solvent (a mixed solution of N,N-dimethylformamide and ethanol with a volume ratio of 1.25:1), ultrasonic stirring was performed to disperse uniformly, 0.7 g (1:2:1 mass ratio of urea, thiourea and dicyandiamide which were ground uniformly) was added, then 1.1 mL of glacial acetic acid, 2 g of butyl titanate and 0.8 g of polyvinylpyrrolidone were added, ultrasonic stirring was performed to obtain a uniform outer solution; equal mass of edible oil and mineral oil were used as the inner spinning solution; the outer solution and the inner solution were respectively input into the outer layer and the inner layer of the coaxial needle, the supply of the inner spinning solution and the outer spinning solution was set to 0.4 mL / h and 2.4 mL / h respectively, the coaxial needle was connected to a high-voltage electrostatic generator of 18 kV, the receiving distance was 15 cm, and the drum received the fiber to obtain a sheath-core composite fiber. The sheath-core composite fiber was treated with turpentine oil for 36 h, and then air-dried, slowly heated from room temperature to 510℃, kept for 6 h, naturally cooled to room temperature, and finally TiO2 / g-C3N4 / BN composite photocatalyst was obtained.

[0060] Example 9

[0061] The present embodiment is a preparation method of TiO2 / g-C3N4 / BN composite photocatalyst, and the steps are as follows:

[0062] 0.02 g BN quantum dots were added to 20 mL of organic solvent (a mixed solution of N,N-dimethylformamide and ethanol with a volume ratio of 1.25:1), ultrasonic stirring was performed to disperse uniformly, 0.6 g (1:2:1 mass ratio of urea, thiourea and dicyandiamide which were ground uniformly) was added, then 1.0 mL of glacial acetic acid, 2 g of butyl titanate and 0.6 g of polyethylene oxide were added, ultrasonic stirring was performed to obtain a uniform outer solution; edible oil and dimethyl silicone oil with a mass ratio of 3:1 were used as the inner spinning solution; the outer solution and the inner solution were respectively input into the outer layer and the inner layer of the coaxial needle, the supply of the inner spinning solution and the outer spinning solution was set to 0.5 mL / h and 2.5 mL / h respectively, the coaxial needle was connected to a high-voltage electrostatic generator of 18 kV, the receiving distance was 15 cm, and the drum received the fiber to obtain a sheath-core composite fiber. The sheath-core composite fiber was treated with n-hexane for 20 h, and then air-dried, slowly heated from room temperature to 580℃, kept for 8 h, naturally cooled to room temperature, and finally TiO2 / g-C3N4 / BN composite photocatalyst was obtained.

[0063] Example 10

[0064] The present embodiment is a preparation method of TiO2 / g-C3N4 / BN composite photocatalyst, and the steps are as follows:

[0065] The 0.013 g BN quantum dots were added into 18 mL organic solvent (a mixed solution of N,N-dimethylformamide and ethanol with a volume ratio of 1.25:1), ultrasonic stirring and dispersing uniformly, 1.2 g (equal mass ratio of urea, thiourea, melamine and dicyandiamide) was added, and then 1.5 mL glacial acetic acid, 4 g butyl titanate and 1.5 g polyvinyl pyrrolidone were added, ultrasonic stirring and dispersing uniformly to obtain an outer solution; edible oil was used as an inner spinning solution; the outer solution and the inner solution were respectively input into the outer layer and the inner layer of a coaxial needle, the supply of the inner spinning solution and the outer spinning solution was set to 0.4 mL / h and 2.0 mL / h respectively, the coaxial needle was connected to a high-voltage electrostatic generator of 18 kV, the receiving distance was 15 cm, and the fibers were received by a drum to obtain a sheath-core composite fiber. The sheath-core composite fiber was treated with turpentine oil for 24 h, and then air-dried, slowly heated from room temperature to 560 ℃, kept for 5 h, naturally cooled to room temperature, and finally obtained a TiO2 / g-C3N4 / BN composite photocatalyst.

[0066] Comparative Example 1

[0067] The comparative example 1 is a preparation method of an anatase TiO2 photocatalyst prepared by electrospinning, and the steps are as follows:

[0068] The 3 g butyl titanate, 1.2 mL glacial acetic acid and 1.2 g polyvinyl pyrrolidone were added into 15 mL organic solvent (a mixed solution of N,N-dimethylformamide and ethanol with a volume ratio of 1.25:1), stirring to obtain an outer solution; dimethyl silicone oil was used as an inner spinning solution. The outer solution and the inner solution were respectively input into the outer layer and the inner layer of a coaxial needle, the supply of the inner spinning solution and the outer spinning solution was set to 0.4 mL / h and 1.8 mL / h respectively, the coaxial needle was connected to a high-voltage electrostatic generator of 17 kV, the receiving distance was 15 cm, and the fibers were received by a drum to obtain a sheath-core composite fiber. The sheath-core composite fiber was treated with n-octane for 24 h, and then air-dried, slowly heated from room temperature to 550 ℃, kept for 4 h, naturally cooled to room temperature, and finally obtained a TiO2 photocatalyst.

[0069] Comparative Example 2

[0070] The comparative example is a preparation method of a TiO2 / g-C3N4 composite photocatalyst prepared by electrospinning, and the steps are as follows:

[0071] 0.6 g urea, 1.2 mL glacial acetic acid, 3 g butyl titanate and 1.2 g polyvinylpyrrolidone were added to 15 mL of organic solvent (a mixed solution of N,N-dimethylformamide and ethanol in a volume ratio of 1.25:1) to obtain a uniform outer solution; dimethyl silicone oil was used as an inner spinning solution. The outer solution and the inner solution were respectively input into the outer layer and the inner layer of a coaxial needle, the feeding of the inner spinning solution and the outer spinning solution was 0.4 mL / h and 1.8 mL / h respectively, the coaxial needle was connected to a high-voltage electrostatic generator of 17 kV, the receiving distance was 15 cm, the drum received the fiber, and after drying, a sheath-core composite fiber was obtained. The sheath-core composite fiber was treated with n-octane for 24 h, and after air drying, it was slowly heated from room temperature to 550 ℃, kept for 4 h, and naturally cooled to room temperature, and finally a TiO2 / g-C3N4 composite photocatalyst was obtained.

[0072] Application Example

[0073] The photocatalysts prepared in Example 1, Comparative Example 1 and Comparative Example 2 were used to photocatalytically degrade rhodamine B and methyl orange dye wastewater respectively, and the steps were as follows:

[0074] 1. 50 mg of the photocatalysts prepared in Example 1, Comparative Example 1 and Comparative Example 2 were respectively added to 50 mL of dye wastewater, a rhodamine B aqueous solution with a concentration of 30 mg / L, stirred in the dark room for 30 min to reach adsorption saturation, and then subjected to photocatalytic degradation experiment under the irradiation of a 300W xenon lamp light source. The sample was taken, centrifuged and the photocatalyst was removed every certain time interval, and the residual concentration of rhodamine B in the aqueous solution was tested by ultraviolet-visible light spectrophotometer.

[0075] 2. 50 mg of the photocatalysts prepared in Example 1, Comparative Example 1 and Comparative Example 2 were respectively added to 50 mL of dye wastewater, a rhodamine B aqueous solution with a concentration of 10 mg / L, stirred in the dark room for 30 min to reach adsorption saturation, and then subjected to photocatalytic degradation experiment under the irradiation of a 300W xenon lamp light source. The sample was taken, centrifuged and the photocatalyst was removed every certain time interval, and the residual concentration of rhodamine B in the aqueous solution was tested by ultraviolet-visible light spectrophotometer.

[0076] 3. 50 mg of the photocatalysts prepared in Example 1, Comparative Example 1 and Comparative Example 2 were respectively added to 50 mL of dye wastewater, a methyl orange aqueous solution with a concentration of 30 mg / L, stirred in the dark room for 30 min to reach adsorption saturation, and then subjected to photocatalytic degradation experiment under the irradiation of a 300W xenon lamp light source. The sample was taken, centrifuged and the photocatalyst was removed every certain time interval, and the residual concentration of methyl orange in the aqueous solution was tested by ultraviolet-visible light spectrophotometer.

[0077] Figure 1The effect diagram of the photocatalyst prepared in Example 1 of the present application, Comparative Example 1 and Comparative Example 2 in catalyzing degradation of rhodamine B.

[0078] Figure 2 The recycling effect diagram of the photocatalyst prepared in Example 1 of the present application. It can be seen from Figure 1 , Figure 2 that, in the photocatalytic degradation of rhodamine B aqueous solution containing 30 mg / L, the degradation rate is 95.7% after 120 min of illumination experiment using the photocatalyst prepared in Example 1 of the present application, which is much higher than the catalytic efficiency of other catalysts, and the degradation efficiency is about 85% after repeated use for 5 times, which has good repeatability.

[0079] Figure 3 The N2 adsorption-desorption isotherm of the photocatalyst prepared in Example 1 of the present application. It can be seen from Figure 3 that the specific surface area of the photocatalyst prepared in Example 1 of the present application is as high as 367.8 m 2 / g, which is much higher than the catalysts reported in the literatures of electrospun TiO2 and TiO2 / g-C3N4 photocatalysts for catalytic degradation of pollutants in water. The higher surface area in the present application helps to absorb organic pollutant molecules and improve the photocatalytic performance.

[0080] Figure 4 The pore size distribution diagram of the photocatalyst prepared in Example 1 of the present application. It can be seen from Figure 4 that the catalyst has many mesopores (31.2 nm) and macropores (65.3 nm and 122.0 nm), and the rich pore channels increase the speed of charge transfer and product molecule diffusion for the catalytic reaction.

[0081] Figure 5 The UV-visible spectrum of the photocatalyst prepared in Example 1 of the present application, Comparative Example 1 and Comparative Example 2. It can be seen from Figure 5 that the absorption edge of TiO2 / g-C3N4 / BN is obviously red-shifted compared with pure TiO2 and TiO2 / g-C3N4 samples.

[0082] Figure 6 The band gap calculation diagram of the photocatalyst prepared in Example 1 of the present application, Comparative Example 1 and Comparative Example 2. It can be seen from Figure 6 that after adding g-C3N4 and BN quantum dots, the band gap of TiO2 fiber is significantly reduced, and Eg is shortened from 3.05 eV to 2.53 eV, which means that TiO2 / g-C3N4 / BN catalyst can absorb more visible light.

[0083] Figure 7 The effect diagram of the photocatalyst prepared in Example 1 of the present application, Comparative Example 1 and Comparative Example 2 in degrading 10 mg / L rhodamine B. It can be seen from Figure 7It can be seen that 50 mg of the catalyst prepared in Example 1 is added to 50 mL of an aqueous solution containing 10 mg / L of rhodamine B for photocatalytic degradation, and the degradation rate is 98.3% after 40 min of illumination.

[0084] Figure 8 The effect diagram of photocatalyst degradation of 30 mg / L methyl orange is prepared for Example 1, Comparative Example 1 and Comparative Example 2 of the present application. Figure 8 It can be seen that the degradation rate is 96% after 50 min when it is put into 50 mL of a solution containing 30 mg / L of methyl orange.

[0085] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a TiO2 / g-C3N4 / BN composite photocatalyst by electrospinning, characterized in that, The steps are as follows: (1) the BN quantum dots are added into an organic solvent, ultrasonic stirring and dispersion for 3 hours, then carbon-nitrogen precursor, glacial acetic acid, butyl titanate and polymer are added and stirred uniformly to obtain an outer layer spinning solution; an oil substance is used as an inner layer spinning solution; coaxial electrospinning is performed to obtain a skin-core composite fiber; In the step (1), the BN quantum dots are prepared by adding BN powder into an organic solvent, ultrasonic crushing, N2 degassing, then solvent thermal treatment, cooling the obtained suspension to room temperature, centrifuging, collecting the supernatant and freeze-drying to obtain the BN quantum dots; In the step (1), the organic solvent is a mixed solvent of N,N-dimethylformamide and ethanol in a volume ratio of 1.25:1, the mass-volume ratio of the BN powder to the organic solvent is 0.4g:50mL, the ultrasonic crushing power is 600W, the ultrasonic crushing time is 6h, the N2 degassing time is 30min, the solvent thermal treatment temperature is 180℃, the solvent thermal treatment time is 12h, the centrifuging speed is 10000rpm, and the centrifuging time is 5min; (2) the skin-core composite fiber obtained in the step (1) is washed in a solvent to remove the inner layer solution, dried to obtain a composite fiber; (3) the composite fiber obtained in the step (2) is calcined in air or oxygen, the calcination temperature is 500-600℃, the calcination time is 3-8h, the calcination is completed, then the composite fiber is naturally cooled to room temperature to obtain a TiO2 / g-C3N4 / BN composite photocatalyst. 2.The method for preparing TiO 2 / g-C 3 N 4 / BN composite photocatalyst by electrostatic spinning according to claim 1, characterized in that: In the step (1), the organic solvent is a mixed solvent of N,N-dimethylformamide and anhydrous ethanol in a volume ratio of 1.25:1; the carbon-nitrogen precursor is any one or a combination of urea, melamine, dicyandiamide or thiourea; the polymer is any one or a combination of polyvinylpyrrolidone, polyethylene oxide, polyethylene glycol or polymethyl methacrylate; and the oil substance is any one or a combination of mineral oil, dimethyl silicone oil or edible oil. 3.The method for preparing TiO 2 / g-C 3 N 4 / BN composite photocatalyst by electrospinning according to claim 1 or 2, characterized in that: In the step (1), the mass ratio of the BN quantum dots, the carbon-nitrogen precursor, the glacial acetic acid, the butyl titanate and the polymer in the outer layer spinning solution is (0.003-0.02):(0.5-2):(0.6-2):(2-4):(0.6-3), and the mass fraction of these substances in the outer layer spinning solution is 15-35wt%. 4.The method for preparing TiO 2 / g-C 3 N 4 / BN composite photocatalyst by electrospinning according to claim 3, characterized in that: In the step (1), the coaxial electrospinning method is as follows: the outer layer spinning solution and the inner layer spinning solution are connected to the outer layer and the inner layer of a coaxial needle respectively, the ratio of the inner layer spinning solution to the outer layer spinning solution in the electrospinning process is adjusted to 1:(1-9), the total liquid supply rate is 0.3-6mL / h, a coaxial needle is connected to a high-voltage electrostatic generator for electrospinning, the fiber is received by a roller or a flat plate to obtain a skin-core composite fiber; the pressure of the high-voltage electrostatic generator is 17-18kV, and the receiving distance is 15cm. 5.The method for preparing TiO 2 / g-C 3 N 4 / BN composite photocatalyst by electrospinning according to claim 4, characterized in that: In the step (2), the solvent is any one or a combination of n-octane, n-hexane or turpentine; the washing time in the solvent is 12-48h. 6.The TiO 2 / g-C 3 N 4 / BN composite photocatalyst prepared by the method of any one of claims 1-5. 7.The application of the TiO 2 / g-C 3 N 4 / BN composite photocatalyst of claim 6 in photocatalytic degradation of dye wastewater.

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