Heterojunction photocatalyst, method for preparing same, and use thereof

Abstract

This invention belongs to the field of environmental functional materials technology, and relates to a heterojunction photocatalyst, its preparation method, and its application. The heterojunction photocatalyst has a Z-shaped band structure, comprising bundled h-BN and Ag3PO4 nanoparticles supported on the bundled h-BN, wherein the Ag3PO4 nanoparticles have a particle size of 1 nm-20 nm. The heterojunction photocatalyst of this invention exhibits an initial degradation rate of ≥88% for levofloxacin hydrochloride within 60 min under visible light, and the degradation rate remains above 80% after four cycles.

Description

Technical Field

[0001] This invention belongs to the field of environmental functional materials technology, and specifically relates to a heterojunction photocatalyst, its preparation method, and its application. Background Technology

[0002] Photocatalysis technology has attracted widespread attention as a method for treating antibiotic wastewater that is widely applicable, has a fast reaction rate, strong oxidation capacity, and produces little or no pollution. Photocatalysts prepared using semiconductor materials can generate hydroxyl or superoxide radicals with strong oxidizing effects under sunlight, thereby degrading antibiotic molecules.

[0003] Ag3PO4 exhibits excellent visible light response (band gap 2.36 eV) and is a common active component in photocatalysts. However, the photogenerated electrons present in Ag3PO4 reduce Ag... + To Ag 0 The reaction easily leads to photocorrosion, resulting in a 60% deactivation rate of pure Ag3PO4 after 120 min of light irradiation. At the same time, Ag3PO4 has a high surface energy, which promotes the agglomeration of Ag3PO4 particles, resulting in a particle size of generally above 500 nm. This leads to a decrease in the specific surface area of ​​Ag3PO4 particles, a sharp reduction in active sites, and thus a decrease in photocatalytic activity.

[0004] Therefore, there is an urgent need to provide a heterojunction photocatalyst with advantages such as high photocatalytic activity and good stability, as well as its preparation method. Summary of the Invention

[0005] To address the aforementioned problems in existing technologies, this invention provides a heterojunction photocatalyst, its preparation method, and its applications. The heterojunction photocatalyst of this invention possesses a Z-shaped band structure and small Ag3PO4 nanoparticle size, exhibiting not only high photocatalytic activity but also good stability, making it suitable for degrading fluoroquinolone antibiotics, especially levofloxacin hydrochloride.

[0006] To address the aforementioned problems, a first aspect of the present invention provides a heterojunction photocatalyst, wherein the heterojunction photocatalyst has a Z-shaped band structure, comprising bundled h-BN and Ag3PO4 nanoparticles supported on the bundled h-BN, wherein the Ag3PO4 nanoparticles have a particle size of 1 nm-20 nm.

[0007] A second aspect of the present invention provides a method for preparing a heterojunction photocatalyst, wherein the method includes the following steps:

[0008] (1) The bundled h-BN was pretreated by contacting it with acid to obtain pretreated h-BN;

[0009] (2) The pretreated h-BN is contacted with silane in solution I for modification treatment to obtain modified h-BN; wherein the silane contains -NH2 groups;

[0010] (3) The modified h-BN is dispersed in solution II and contacted with AgNO3 to carry out a coordination reaction to obtain a dispersion;

[0011] (4) Under microwave irradiation, Na2HPO4 is added to the dispersion to carry out a precipitation reaction to obtain a heterojunction photocatalyst.

[0012] The third aspect of this invention provides the application of the heterojunction photocatalyst described in the first aspect of this invention, or the heterojunction photocatalyst prepared by the preparation method described in the second aspect of this invention, in the degradation of fluoroquinolone antibiotics.

[0013] Compared with the prior art, the present invention has the following beneficial technical effects:

[0014] 1) The heterojunction photocatalyst provided by the present invention has small Ag3PO4 nanoparticle size and uniform distribution on bundled h-BN, which can provide more active sites and help improve the photocatalytic activity of the heterojunction photocatalyst.

[0015] 2) The heterojunction photocatalyst provided by this invention forms a Z-shaped channel between the deep valence band of h-BN and the conduction band of Ag3PO4, allowing the Ag3PO4 valence band to retain its strong oxidizing properties. + It can inhibit the reduction of Ag by photogenerated electrons. + To Ag 0 The reaction reduces the risk of photocorrosion and helps improve the stability of heterojunction photocatalysts, especially their cycle stability.

[0016] 3) The preparation method of the heterojunction photocatalyst provided by this invention uses bundled h-BN as raw material, including acid pretreatment, silane modification treatment, and coordination reaction (Ag... + The four-step process of anchoring, microwave precipitation, and micro-precipitation has the advantages of simple process and low energy consumption. It can significantly reduce the particle size of Ag3PO4 nanoparticles and prepare heterojunction photocatalysts with Z-shaped band structure.

[0017] 4) The heterojunction photocatalyst provided by this invention has an initial degradation rate of levofloxacin hydrochloride of ≥88% within 60 min under visible light, and the degradation rate remains above 80% after four cycles. It not only has high catalytic activity, but also good cycle stability, and is especially suitable for the degradation of levofloxacin hydrochloride. Attached Figure Description

[0018] Figure 1 The image shows the XRD pattern of the h-BN / Ag3PO4 heterojunction photocatalyst prepared in Example 2 of this invention.

[0019] Figure 2 The image shows the TEM spectrum of the h-BN / Ag3PO4 heterojunction photocatalyst prepared in Example 2 of this invention. Detailed Implementation

[0020] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0021] A first aspect of the present invention provides a heterojunction photocatalyst, wherein the heterojunction photocatalyst has a Z-shaped band structure, comprising bundled h-BN and Ag3PO4 nanoparticles supported on the bundled h-BN, wherein the Ag3PO4 nanoparticles have a particle size of 1 nm-20 nm.

[0022] In this invention, the bundled h-BN (i.e., bundled hexagonal boron nitride) has a layered bundle structure, which provides nanoscale channels, restricts the particle size of Ag3PO4, and prevents Ag3PO4 from agglomerating. Ag3PO4 nanoparticles with a particle size of less than 20 nm are distributed on the bundled h-BN, which enhances the adsorption capacity, provides more active sites, and helps improve the photocatalytic activity of the heterojunction photocatalyst. The valence band of h-BN and the conduction band of Ag3PO4 form a Z-shaped channel, allowing the Ag3PO4 valence band to retain its strong oxidizing properties. + It can inhibit the reduction of Ag by photogenerated electrons. + To Ag 0 The reaction reduces the risk of photocorrosion and helps improve the stability of heterojunction photocatalysts.

[0023] In a preferred embodiment of the present invention, the particle size of the Ag3PO4 nanoparticles can be 1nm, 3nm, 5nm, 7nm, 10nm, 13nm, 15nm, 17nm, 20nm, or any number between these values. For example, the particle size of the Ag3PO4 nanoparticles is preferably 5nm-10nm.

[0024] In this invention, when the particle size of Ag3PO4 nanoparticles is within the range defined above, the contact area between the small-sized particles and the support is larger, which is conducive to the formation of a tighter heterojunction, further promoting charge separation and transport, and helping to further improve the photocatalytic activity of the heterojunction photocatalyst.

[0025] In a preferred embodiment of the present invention, the length of the bundle-shaped h-BN is 0.5μm-10μm, preferably 1μm-5μm; the diameter is 20nm-150nm, preferably 80nm-120nm.

[0026] In this invention, when the length and diameter of the bundled h-BN are within the range defined above, the bundled h-BN is a nanowire with a higher specific surface area, which can provide more active sites, promote the separation and transport of photogenerated electrons and holes, and help to further improve the photocatalytic activity of the heterojunction photocatalyst.

[0027] In a preferred embodiment of the present invention, the mass content of the Ag3PO4 nanoparticles is 10%-50% based on the total mass of the photocatalyst. For example, it can be 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or any number between these values. For example, the mass content of the Ag3PO4 nanoparticles is preferably 25%-35% based on the total mass of the photocatalyst.

[0028] In this invention, Ag3PO4 is readily reduced to Ag under light irradiation. Excessive loading accelerates this process, leading to material structural damage and reduced activity. This invention limits the mass content of Ag3PO4 nanoparticles within the aforementioned range, and especially within the preferred range, which further reduces the risk of photocorrosion and helps improve the catalytic activity and stability of the heterojunction photocatalyst.

[0029] A second aspect of the present invention provides a method for preparing a heterojunction photocatalyst, wherein the method includes the following steps:

[0030] (1) The bundled h-BN was pretreated by contacting it with acid to obtain pretreated h-BN;

[0031] (2) The pretreated h-BN is contacted with silane in solution I for modification treatment to obtain modified h-BN; wherein the silane contains -NH2 groups;

[0032] (3) The modified h-BN is dispersed in solution II and then contacted with AgNO3 to carry out a coordination reaction to obtain a dispersion;

[0033] (4) Under microwave irradiation, Na2HPO4 is added to the dispersion to carry out a precipitation reaction to obtain a heterojunction photocatalyst.

[0034] In step (1):

[0035] In a preferred embodiment of the present invention, the length of the bundle-shaped h-BN is 0.5μm-10μm, preferably 1μm-5μm; the diameter is 20nm-150nm, preferably 80nm-120nm.

[0036] In this invention, the bundled h-BN with length and diameter within the aforementioned defined ranges are nanowires, possessing a higher specific surface area, which can reach 200 m². 2 / g or more can provide a large number of nanoscale channels with pore sizes between 2nm and 5nm, which helps to limit the growth size of Ag3PO4, prevent Ag3PO4 from agglomerating, and provide more active sites.

[0037] In a preferred embodiment of the present invention, the acid solution is selected from one or more of nitric acid, hydrochloric acid, sulfuric acid, and acetic acid, preferably nitric acid, and more preferably dilute nitric acid. The molar content of HNO3 in the dilute nitric acid is 1.5M-4.5M, preferably 2.5M-3.5M.

[0038] In this invention, the pretreatment of bundled h-BN with acid can remove oxides from the surface of bundled hexagonal boron nitride, which helps to further improve the catalytic activity of the photocatalyst.

[0039] In a preferred embodiment of the present invention, based on 1g of the bundled h-BN, the amount of acid solution used is 50mL-200mL, preferably 100mL-150mL.

[0040] In a preferred embodiment of the present invention, the pretreatment operating conditions include: a pretreatment temperature of 60℃-100℃, preferably 70℃-90℃; and a pretreatment time of 2h-10h, preferably 4h-8h.

[0041] In this invention, when the pretreatment temperature and time are limited to the above-mentioned range, the removal effect of oxides on the surface of bundled h-BN is better, and the heterojunction photocatalyst prepared thereby has better photocatalytic activity.

[0042] In step (2):

[0043] In a preferred embodiment of the present invention, the silane is selected from one or more of (3-aminopropyl)triethoxysilane, (3-aminopropyl)trimethoxysilane, and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane.

[0044] In this invention, silane can be used to graft -NH2 groups onto the surface of pretreated h-BN, and the -NH2 groups can enhance the affinity of h-BN for Ag. + Its adsorption properties allow it to react with Ag in subsequent coordination reactions.+ Forms a stable [Ag(NH3)2] + Coordination compounds.

[0045] In a preferred embodiment of the present invention, the solution I is selected from an alcohol solution, wherein the alcohol solution is selected from one or more of methanol, ethanol, n-propanol, and isopropanol.

[0046] In this invention, pretreated h-BN can be first dispersed in an alcohol solution before adding silane. The contact between pretreated h-BN and silane in the alcohol solution improves the mixing effect, resulting in a more uniform distribution of -NH2 groups on the pretreated h-BN, which helps to further improve the stability of the photocatalyst's catalytic activity.

[0047] In a preferred embodiment of the present invention, based on 1g of the bundled h-BN, the amount of silane used is 1mL-5mL, preferably 2mL-3mL; the amount of solution I used is 20mL-80mL, preferably 40mL-60mL. When the amount of silane is less than 1mL, the adsorption between Ag3PO4 and h-BN is mainly physical, and Ag3PO4 is easily detached. When the amount of silane exceeds 5mL, it may block the pores on the bundled h-BN, resulting in the masking of active sites.

[0048] In a preferred embodiment of the present invention, the operating conditions for the modification treatment include: a modification treatment temperature of 60℃-95℃, preferably 70℃-80℃; and a modification treatment time of 8h-16h, preferably 10h-14h.

[0049] In this invention, when the temperature and time of the modification treatment are within the above-defined range, especially the preferred range, the reaction between the pretreated h-BN and the silane is more complete, and the modification effect is better.

[0050] In step (3):

[0051] In a preferred embodiment of the present invention, based on 0.1g of the modified h-BN, the mass of the AgNO3 is 0.02g-0.085g, preferably 0.04g-0.07g.

[0052] In this invention, modifying the -NH2 group in h-BN can affect Ag. + It acts as an anchoring agent, binding with Ag in AgNO3. + A coordination reaction occurs, generating [Ag(NH3)2] on the modified h-BN. +The complex forms stable sites, inhibiting the aggregation of silver nanoparticles and thus helping to improve photocatalytic performance. Moreover, the amount of AgNO3 added can ensure that the mass content of Ag3PO4 nanoparticles in the prepared heterojunction photocatalyst is 10%-50%, preferably 25%-35%.

[0053] In a preferred embodiment of the present invention, the coordination reaction is carried out in the dark for 8-16 hours at room temperature, preferably 10-14 hours.

[0054] In this invention, by controlling the reaction temperature and reaction time of the coordination reaction, the anchoring density of Ag⁺ can be controlled, avoiding aggregation and helping to further improve the stability of photocatalysis.

[0055] In step (4):

[0056] In a preferred embodiment of the present invention, the Na2HPO4 is added dropwise to the dispersion in the form of a Na2HPO4 solution. Specifically, in this invention, the concentration of Na2HPO4 in the Na2HPO4 solution can be 0.05M-0.15M, preferably 0.08M-0.12M.

[0057] In a preferred embodiment of the present invention, the mass ratio of Ag element in the dispersion to P element in Na2HPO4 is 10-12:1, preferably 10.3-10.8:1.

[0058] In this invention, Na2HPO4 and [Ag(NH3)2] are used. + The complex undergoes a precipitation reaction, resulting in Ag3PO4 nanoparticles that grow on h-BN nanobundles. The valence band of h-BN (+4.2 eV) and the conduction band of Ag3PO4 (+0.45 eV) form a Z-shaped channel, allowing the Ag3PO4 valence band to retain its strong oxidizing properties. + A heterojunction with a Z-shaped band structure is formed. The addition of Na2HPO4 ensures an appropriate loading of Ag3PO4 nanoparticles, which can further reduce the risk of photocorrosion and help improve the stability of the heterojunction photocatalyst.

[0059] In a preferred embodiment of the present invention, the operating conditions of the precipitation reaction include: the temperature of the precipitation reaction is 50℃-80℃, preferably 60℃-70℃; the microwave power is 200W-400W, preferably 250W-350W; and the microwave time is 5min-15min, preferably 8min-12min.

[0060] In this invention, by limiting the microwave reaction temperature and microwave power within the aforementioned range, instantaneous nucleation can be induced. Compared with the traditional precipitation method, this significantly shortens the reaction time, for example, from 12 hours to 10 minutes. Furthermore, it can further reduce the grain size of Ag3PO4 and improve the bonding force between the in-situ grown Ag3PO4 nanoparticles and the bundled h-BN, thereby helping to improve the catalytic activity and stability of the heterojunction photocatalyst.

[0061] The third aspect of this invention provides the application of the heterojunction photocatalyst described in the first aspect of this invention, or the heterojunction photocatalyst prepared by the preparation method described in the second aspect of this invention, in the degradation of fluoroquinolone antibiotics.

[0062] The heterojunction photocatalyst provided by this invention has an initial degradation rate of ≥88% for levofloxacin hydrochloride within 60 min under visible light, and the degradation rate of levofloxacin hydrochloride remains above 80% after four cycles, making it particularly suitable for degrading levofloxacin hydrochloride.

[0063] The present invention will now be described in detail with reference to specific embodiments thereof, but it should be understood that the scope of protection of the present invention is not limited to the embodiments.

[0064] Example 1

[0065] (1) 1g of bundled h-BN (1μm in length and 80nm in diameter) was added to 100mL of 3M dilute nitric acid for pretreatment. The mixture was refluxed at 80℃ for 6h, then centrifuged and washed with deionized water until neutral to obtain pretreated h-BN.

[0066] (2) The pretreated h-BN was dispersed in 50 mL of ethanol, and 2 mL of (3-aminopropyl)triethoxysilane was added. After mixing evenly, the mixture was modified and stirred at 70 °C for 12 h. Then, the mixture was centrifuged and washed to obtain modified h-BN.

[0067] (3) Disperse 0.1g of the above modified h-BN in 50mL of water, sonicate for 30min, add 0.04g of AgNO3 to carry out the coordination reaction, stir at room temperature in the dark for 12h to obtain the dispersion;

[0068] (4) Add 0.1M Na2HPO4 aqueous solution to the above dispersion. The mass ratio of Ag element in the dispersion to P element in Na2HPO4 is 10.5:1. Then transfer it to a microwave reactor for precipitation reaction. Irradiate at 60℃ and 300W for 10min. Then centrifuge, wash with ethanol / water 3 times, and dry under nitrogen protection at 60℃ for 6h to obtain heterojunction photocatalyst.

[0069] Example 2

[0070] (1) 1g of bundled h-BN (3μm in length and 100nm in diameter) was added to 150mL of 2.5M dilute nitric acid for pretreatment. The mixture was refluxed at 90℃ for 4h, then centrifuged and washed with deionized water until neutral to obtain pretreated h-BN.

[0071] (2) The pretreated h-BN was dispersed in 60 mL of ethanol, and 3 mL of (3-aminopropyl)triethoxysilane was added. After mixing evenly, the mixture was modified and stirred at 80 °C for 10 h. Then, the mixture was centrifuged and washed to obtain modified h-BN.

[0072] (3) Disperse 0.1g of the above modified h-BN in 50mL of water, sonicate for 30min, add 0.052g of AgNO3 to carry out the coordination reaction, stir at room temperature in the dark for 10h to obtain the dispersion;

[0073] (4) Add 0.1M Na2HPO4 aqueous solution to the above dispersion. The mass ratio of Ag element in the dispersion to P element in Na2HPO4 is 10.5:1. Then transfer it to a microwave reactor for precipitation reaction. Irradiate at 65℃ and 350W for 12min. Then centrifuge, wash with ethanol / water 3 times, and dry under nitrogen protection at 60℃ for 6h to obtain heterojunction photocatalyst.

[0074] Example 3

[0075] (1) 1g of bundled h-BN (5μm in length and 120nm in diameter) was added to 125mL of 3.5M dilute nitric acid for pretreatment. The mixture was refluxed at 70℃ for 8h, then centrifuged and washed with deionized water until neutral to obtain pretreated h-BN.

[0076] (2) The pretreated h-BN was dispersed in 40 mL of ethanol, and 2.5 mL of (3-aminopropyl)triethoxysilane was added. After mixing evenly, the mixture was modified and stirred at 75 °C for 14 h. Then, it was centrifuged and washed to obtain modified h-BN.

[0077] (3) Disperse 0.1g of the above modified h-BN in 50mL of water, sonicate for 30min, add 0.066g of AgNO3 to carry out the coordination reaction, stir at room temperature in the dark for 14h to obtain the dispersion;

[0078] (4) Add 0.1M Na2HPO4 aqueous solution to the above dispersion. The mass ratio of Ag element in the dispersion to P element in Na2HPO4 is 10.5:1. Then transfer it to a microwave reactor for precipitation reaction. Irradiate at 70℃ and 250W for 8 min. After centrifugation, wash with ethanol / water 3 times and dry under nitrogen protection at 60℃ for 6 h to obtain heterojunction photocatalyst.

[0079] Example 4

[0080] (1) 1g of bundled h-BN (0.5μm in length and 50nm in diameter) was added to 200mL of 1.5M dilute nitric acid for pretreatment. The mixture was refluxed at 100℃ for 2h, then centrifuged and washed with deionized water until neutral to obtain pretreated h-BN.

[0081] (2) The pretreated h-BN was dispersed in 80 mL of ethanol, and 4 mL of (3-aminopropyl)trimethoxysilane was added. After mixing evenly, the mixture was modified and stirred at 95 °C for 8 h. Then, the mixture was centrifuged and washed to obtain modified h-BN.

[0082] (3) Disperse 0.1g of the above modified h-BN in 50mL of water, sonicate for 30min, add 0.022g of AgNO3 to carry out the coordination reaction, stir at room temperature in the dark for 8h to obtain the dispersion;

[0083] (4) Add 0.1M Na2HPO4 aqueous solution to the above dispersion. The mass ratio of Ag element in the dispersion to P element in Na2HPO4 is 10.5:1. Then transfer it to a microwave reactor for precipitation reaction. Irradiate at 80℃ and 200W for 15min. Then centrifuge, wash with ethanol / water 3 times, and dry under nitrogen protection at 60℃ for 6h to obtain heterojunction photocatalyst.

[0084] Example 5

[0085] (1) 1g of bundled h-BN (10μm in length and 150nm in diameter) was added to 50mL of 4M dilute nitric acid for pretreatment. The mixture was refluxed at 60℃ for 10h, then centrifuged and washed with deionized water until neutral to obtain pretreated h-BN.

[0086] (2) The pretreated h-BN was dispersed in 20 mL of ethanol, and 1 mL of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane was added. After mixing evenly, the mixture was modified and stirred at 60 °C for 16 h. Then, the mixture was centrifuged and washed to obtain modified h-BN.

[0087] (3) Disperse 0.1g of the above modified h-BN in 50mL of water, sonicate for 30min, add 0.081g of AgNO3 to carry out the coordination reaction, stir at room temperature in the dark for 16h to obtain the dispersion;

[0088] (4) Add 0.1M Na2HPO4 aqueous solution to the above dispersion. The mass ratio of Ag element in the dispersion to P element in Na2HPO4 is 10.5:1. Then transfer it to a microwave reactor for precipitation reaction. Irradiate at 50℃ and 400W for 5min. Then centrifuge, wash 3 times with ethanol / water, and dry under nitrogen protection at 60℃ for 6h to obtain heterojunction photocatalyst.

[0089] Comparative Example 1

[0090] (1) 1g of ordinary flake h-BN (100μm in length, 80μm in width, and 50nm in thickness) was added to 150mL of 2.5M dilute nitric acid for pretreatment. The solution was refluxed at 90℃ for 4h, then centrifuged and washed with deionized water until neutral to obtain pretreated h-BN.

[0091] (2) Disperse 0.1g of the above pretreated h-BN in 50mL of water, sonicate for 30min, add 0.052g of AgNO3, stir at room temperature in the dark for 10h to obtain a dispersion;

[0092] (3) Add 0.1M Na2HPO4 aqueous solution to the above dispersion. The mass ratio of Ag element in the dispersion to P element in Na2HPO4 is 10.5:1. Then transfer it to a microwave reactor for precipitation reaction. Irradiate at 65℃ and 350W for 12min. Then centrifuge, wash with ethanol / water 3 times, and dry under nitrogen protection at 60℃ for 6h to obtain heterojunction photocatalyst.

[0093] Comparative Example 2

[0094] (1) 1g of bundled h-BN (3μm in length and 100nm in diameter) was added to 150mL of 2.5M dilute nitric acid for pretreatment. The mixture was refluxed at 90℃ for 4h, then centrifuged and washed with deionized water until neutral to obtain pretreated h-BN.

[0095] (2) Disperse 0.1g of the above pretreated h-BN in 50mL of water and sonicate for 30min to obtain solution A;

[0096] (3) Dissolve 0.052g of AgNO3 in 20mL of water, then add 0.1M Na2HPO4 aqueous solution dropwise, stir at room temperature in the dark to obtain solution B, in which the mass ratio of Ag to P in solution B is 10.5:1;

[0097] (4) Add solution B dropwise into solution A, heat in a water bath at 85°C until the solution evaporates to dryness, then centrifuge, wash three times with ethanol / water, and dry in an oven for 6 hours to obtain a heterojunction photocatalyst.

[0098] The analytical results of the heterojunction photocatalysts prepared in the examples and comparative examples are shown in Table 1. The length and particle size of h-BN were measured using transmission electron microscopy (TEM); the nanoparticle size of Ag3PO4 was measured using TEM; the mass content of Ag3PO4 was measured using EDS energy dispersive spectroscopy; and the heterojunction structure was determined using UV-Vis diffuse reflectance and XPS valence band structure analysis. VBTests combined with judgment.

[0099] Table 1

[0100]

[0101] By comparing Example 2 with Comparative Examples 1 and 2, it can be seen that the morphology of h-BN, silane modification, coordination reaction, and microwave precipitation have a significant impact on the growth and distribution of Ag3PO4 nanoparticles in the heterojunction photocatalyst, as well as the formation of the Z-shaped band structure. Using the method of this invention, heterojunction photocatalysts with initial Ag3PO4 nanoparticle sizes between 1 nm and 20 nm and possessing a Z-shaped band structure can be prepared.

[0102] Test Example 1

[0103] The heterojunction photocatalyst prepared in Example 2 was characterized by XRD and transmission electron microscopy, respectively. The results are as follows: Figure 1 and Figure 2 As shown. Among them, Figure 1 The image shows the XRD pattern of the h-BN / Ag3PO4 heterojunction photocatalyst prepared in Example 2. Figure 1 As can be seen, no impurity peaks of silver metal or other silver salts appeared in the spectrum, indicating that the Ag3PO4 prepared by this method is pure, has high crystallinity on the surface, and forms a good bond with h-BN. Figure 2 The TEM image of the h-BN / Ag3PO4 heterojunction photocatalyst prepared in Example 2 is shown below. Figure 2 It can be seen that Ag3PO4 is dispersed in the surface and interstices of the h-BN bundled structure, and the average particle size of Ag3PO4 nanoparticles is 8 nm, with no aggregation.

[0104] Test Example 2

[0105] 10 mg of the heterojunction photocatalyst prepared in the examples and comparative examples were dispersed in 50 mL of 25 μmol / L levofloxacin hydrochloride solution. First, the solution was placed in the dark for 30 min for dark adsorption. Then, the photocatalytic experiment was carried out under 800 W xenon lamp irradiation. Samples were taken every 10 min, and the content of levofloxacin hydrochloride in the solution was analyzed by high performance liquid chromatography (Agilent 1260 HPLC). The removal rate of levofloxacin was calculated. The test results are shown in Table 2.

[0106] Table 2

[0107]

[0108] Note: -30min refers to the removal rate of levofloxacin hydrochloride at the initial 30min of placement in a light-protected environment, and 0min refers to the removal rate of levofloxacin hydrochloride after 30min of placement in a light-protected environment, that is, at the beginning of light exposure.

[0109] As shown in Table 2, the heterojunction photocatalyst prepared in this invention exhibits an initial degradation rate of over 88% for levofloxacin hydrochloride within 60 minutes under visible light irradiation. Comparison of Example 2 with Comparative Examples 1 and 2 demonstrates that the small particle size and Z-shaped band structure of Ag3PO4 nanoparticles significantly enhance the degradation rate of levofloxacin hydrochloride by the heterojunction photocatalyst.

[0110] Referring to Table 1, a comparison between Example 2 and Comparative Example 1 shows that the sheet-like h-BN is not conducive to limiting the growth size of Ag3PO4, affecting the composite effect and leading to a decrease in catalyst removal efficiency. A comparison between Example 2 and Comparative Example 2 also shows that silane modification and microwave precipitation can effectively prevent the aggregation of Ag3PO4 nanoparticles and promote the formation of Z-shaped band structures. In Comparative Example 2, h-BN and Ag3PO4 are simply physically combined, with Ag3PO4 nanoparticles agglomerated on the h-BN surface, resulting in poor overall removal efficiency.

[0111] Test Example 3

[0112] 10 mg of the heterojunction photocatalysts prepared in the examples and comparative examples were dispersed in 50 mL of a 25 μmol / L levofloxacin hydrochloride solution. First, the solution was placed in a dark environment for 30 min for dark adsorption. Then, photocatalysis was performed under 800 W xenon lamp irradiation. After 60 min, samples were taken to analyze the levofloxacin hydrochloride content in the solution, and the photocatalyst was separated by passing it through a 0.22 μm filter membrane. The separated photocatalyst was placed in an oven and baked at 60 °C for 5 h to obtain the regenerated photocatalyst. The degradation test of levofloxacin hydrochloride was repeated on the regenerated photocatalyst, for a total of four regenerations. The test results are shown in Table 3.

[0113] Table 3

[0114]

[0115] As shown in Table 3, the heterojunction photocatalyst of this invention has a high initial degradation rate of levofloxacin hydrochloride, and the degradation rate of levofloxacin hydrochloride decreases by no more than 10% after four cycles, indicating that the heterojunction photocatalyst has high cycling stability.

[0116] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A heterojunction photocatalyst, characterized in that, The heterojunction photocatalyst has a Z-shaped band structure, including bundled h-BN and Ag3PO4 nanoparticles supported on the bundled h-BN, wherein the particle size of the Ag3PO4 nanoparticles is 1nm-20nm. The bundled h-BN has a length of 0.5 μm-10 μm and a diameter of 20 nm-150 nm; based on the total mass of the heterojunction photocatalyst, the mass content of the Ag3PO4 nanoparticles is 10%-50%. The preparation method of the heterojunction photocatalyst includes the following steps: (1) The bundled h-BN was pretreated by contacting it with acid to obtain pretreated h-BN; (2) The pretreated h-BN is contacted with silane in solution I for modification treatment to obtain modified h-BN; wherein the silane contains -NH2 groups; (3) The modified h-BN is dispersed in solution II and then contacted with AgNO3 to carry out a coordination reaction to obtain a dispersion; (4) Under microwave irradiation, Na2HPO4 is added to the dispersion to carry out a precipitation reaction to obtain a heterojunction photocatalyst.

2. The heterojunction photocatalyst according to claim 1, characterized in that, The Ag3PO4 nanoparticles have a particle size of 5nm-10nm.

3. A method for preparing a heterojunction photocatalyst, characterized in that, The method includes the following steps: (1) The bundled h-BN was pretreated by contacting it with acid to obtain pretreated h-BN; (2) The pretreated h-BN is contacted with silane in solution I for modification treatment to obtain modified h-BN; wherein the silane contains -NH2 groups; (3) The modified h-BN is dispersed in solution II and then contacted with AgNO3 to carry out a coordination reaction to obtain a dispersion; (4) Under microwave irradiation, Na2HPO4 is added to the dispersion to carry out a precipitation reaction to obtain a heterojunction photocatalyst.

4. The preparation method according to claim 3, characterized in that, The length of the bundled h-BN is 0.5μm-10μm, and the diameter is 20nm-150nm; And / or, the acid is selected from one or more of nitric acid, hydrochloric acid, sulfuric acid, and acetic acid; And / or, based on 1g of the bundled h-BN, the amount of acid solution used is 50mL-200mL; And / or, the pretreatment operating conditions include: a pretreatment temperature of 60℃-100℃ and a pretreatment time of 2h-10h.

5. The preparation method according to claim 3, characterized in that, The silane is selected from one or more of (3-aminopropyl)triethoxysilane, (3-aminopropyl)trimethoxysilane, and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane; And / or, based on 1g of the bundled h-BN, the amount of silane used is 1mL-5mL; And / or, the operating conditions for the modification treatment include: a modification treatment temperature of 60℃-95℃ and a modification treatment time of 8h-16h.

6. The preparation method according to claim 3, characterized in that, Based on 0.1g of the modified h-BN, the mass of the AgNO3 is 0.02g-0.085g; And / or, the coordination reaction is carried out in the dark for 8-16 hours at room temperature.

7. The preparation method according to claim 3, characterized in that, The mass ratio of Ag element in the dispersion to P element in Na2HPO4 is 10-12:1; And / or, the operating conditions for the precipitation reaction include: a precipitation reaction temperature of 50℃-80℃, a microwave power of 200W-400W, and a microwave time of 5min-15min.

8. The application of the heterojunction photocatalyst according to claim 1 or 2, or the heterojunction photocatalyst prepared by any one of claims 3-7, in the degradation of fluoroquinolone antibiotics.

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