A BN-g-C3N4 / Cs3Bi2Br9 composite photocatalyst for degrading chloroquine phosphate and its synthesis method

Abstract

The application discloses a BN-g-C3N4 / Cs3Bi2Br9 composite photocatalyst for degrading chloroquine phosphate and a synthesis method thereof. The BN-g-C3N4 / Cs3Bi2Br9 composite photocatalyst is characterized by the fact that, as shown by a scanning electron microscope, Cs3Bi2Br9 is in-situ grown on the surface of BN-g-C3N4, and the two monomers form a composite material, and the size and morphology of the two are not obviously changed. The synthesis method of the composite photocatalyst is simple, the photocatalytic activity is high, the method is easy to enlarge, and the composite photocatalyst has good stability and reusability, and has a good engineering application prospect.

Description

Technical Field

[0001] This invention belongs to the field of photocatalysis technology, and particularly relates to a BN-g-C3N4 / Cs3Bi2Br9 composite photocatalyst for degrading chloroquine phosphate and its synthesis method. Background Technology

[0002] In recent years, chloroquine phosphate (CQ) has become increasingly popular. 18 H 32 Chloroquine phosphate (ClN3O8P2) is primarily used to treat malignant malaria and also plays a role in the prevention of severe malaria. Due to its water solubility, stability, and difficulty in volatilization, chloroquine phosphate and its metabolites can easily affect the living environment of animals, plants, and humans, potentially causing irreversible harm. It is noteworthy that photodegradation technology has attracted widespread attention because it can utilize sunlight to generate reactive oxygen species (such as superoxide radicals, singlet oxygen, and hydroxyl radicals) that can efficiently degrade organic pollutants. Constructing novel, efficient, and low-cost composite photocatalysts is a crucial step in this process.

[0003] Graphitic carbon nitride (g-C3N4) is a conjugated polymer, insoluble in acids, alkalis, and organic solvents, exhibiting strong visible light absorption, stable physicochemical properties, and a favorable electronic structure. However, the poor photocatalytic activity and rapid carrier recombination of pure g-C3N4 hinder its practical application. Therefore, extensive modification studies have been conducted on g-C3N4. Introducing doping and defects into non-metallic heteroatoms (B, C, N, O, S, P, and I) is one of the effective strategies to improve the visible light photocatalytic activity of g-C3N4. Compared to single-element doping, B and N co-doped g-C3N4 has been shown to possess higher photocatalytic activity and unusual physicochemical properties (Adv. Mater. 2019, 31, 1903545).

[0004] Halide perovskites and their derivatives (such as Cs3Bi2Br9) possess broad absorption spectra, large extinction coefficients, low exciton binding energies, fast charge carrier mobility, and unique photoelectric and physicochemical properties, making them highly promising green and practical photocatalysts. However, the activation effect of halide perovskite surfaces in composite photocatalysts, which is closely related to the reaction rate and photocatalytic efficiency of surface chemical reactions, has received little attention. Constructing composite photocatalysts is often used as a useful strategy to promote photocatalytic processes involving halide perovskites and their derivatives. Meanwhile, the reaction efficiency of composite photocatalysts mainly depends on factors such as interfacial charge transport processes, light absorption capacity, morphology, and surface active sites. Summary of the Invention

[0005] The purpose of this invention is to provide a boron-doped nitrogen-defective graphitic carbon nitride / halogen perovskite (BN-g-C3N4 / Cs3Bi2Br9) composite photocatalyst for the efficient degradation of chloroquine phosphate, and its synthesis method. This photocatalyst exhibits excellent degradation ability, good stability, and photocatalytic activity. This invention enables the efficient degradation of chloroquine phosphate wastewater through photocatalytic technology, meeting the needs of practical production.

[0006] The specific technical solution for achieving the objective of this invention is as follows:

[0007] A method for synthesizing a BN-g-C3N4 / Cs3Bi2Br9 composite photocatalyst for degrading chloroquine phosphate, comprising the following steps:

[0008] Step 1: Synthesis of graphitic carbon nitride (g-C3N4)

[0009] Weigh a certain amount of melamine (C3H6N6), place it in a crucible, and heat it to 520-550℃ in an air atmosphere using a tube furnace at a heating rate of 5-10℃ / min. Hold the temperature for 3-5 hours, then cool it to room temperature and grind it for later use.

[0010] Step 2: Synthesis of boron-doped nitrogen-defective graphitic carbon nitride (BN-g-C3N4)

[0011] Weigh g-C3N4 and sodium borohydride (NaBH4) in a mass ratio of (0.8-1):(0.5-0.7) and place them in a mortar. Grind for 5-10 min and then transfer the powder to a crucible. In a tube furnace under nitrogen protection, heat the powder to 300-500℃ at a rate of 5-10℃ / min and heat for 1-2 h. After cooling to room temperature, remove the powder and grind it for later use.

[0012] Step 3: Add 100-200 ml of isopropanol (IPA) as a solvent, add 50-150 g of BN-g-C3N4 and stir for 1-2 hours using a magnetic stirrer at a speed of 800-900 rpm. This solution is labeled A1. Add CsBr and BiBr3 in 10-500 ml of dimethyl sulfoxide (DMSO) at a mass ratio of (62.6-125.3):(89.6-179.3) until fully dissolved. This solution is labeled A2. Slowly add solution A2 dropwise to solution A1. Pale yellow crystals will precipitate. Stir for 2-3 hours to complete the reaction.

[0013] Step 4: Centrifugal washing to recover solid powder

[0014] Specifically, the centrifuge speed is 6000-8000 rpm, the centrifugation time is 5-10 min, the IPA is washed 3-5 times, and finally the product is placed in a vacuum drying oven at a drying temperature of 60-80℃ for 12-15 h, and then ground to obtain the BN-g-C3N4 / Cs3Bi2Br9 composite photocatalyst.

[0015] A BN-g-C3N4 / Cs3Bi2Br9 composite photocatalyst prepared by the above method was shown by scanning electron microscopy to have a morphology of Cs3Bi2Br9 grown in situ on the surface of BN-g-C3N4. Under low-power white LED irradiation, the catalyst can rapidly generate reactive oxygen species, efficiently degrading chloroquine phosphate in wastewater, with a degradation efficiency reaching up to 98.6% after 60 minutes of illumination.

[0016] The application specifically includes: placing the catalyst in chloroquine phosphate wastewater with a concentration of 5-50 mg / L; adsorbing in the dark for 30-60 minutes, and after reaching adsorption equilibrium, turning on the light source for irradiation for 5-60 minutes; wherein the mass ratio of the catalyst to the volume of the drug wastewater is 5-100 mg: 50-100 ml.

[0017] The present invention has the following advantages:

[0018] 1. The BN-g-C3N4 / Cs3Bi2Br9 composite photocatalyst of the present invention exhibits excellent photodegradation and cycling stability for CQ.

[0019] 2. Compared with g-C3N4, BN-g-C3N4 co-modified with B and N atoms improves the adsorption capacity for CQ.

[0020] 3. The composite photocatalyst formed by BN-g-C3N4 and Cs3Bi2Br9 promoted the generation of reactive oxygen species under light irradiation. Attached Figure Description

[0021] Figure 1 Scanning electron microscope images of g-C3N4, BN-g-C3N4, Cs3Bi2Br9, and BNCN-CBB-3;

[0022] Figure 2 XRD patterns of g-C3N4, BN-g-C3N4, Cs3Bi2Br9 and BNCN-CBB-3;

[0023] Figure 3 Degradation performance diagrams of g-C3N4, BN-g-C3N4, Cs3Bi2Br9 and BNCN-CBB series composite materials;

[0024] Figure 4A schematic diagram of the photodegradation cycle performance of CQ by BNCN-CBB-3;

[0025] Figure 5 XRD and SEM images of BNCN-CBB-3 before and after the fifth cycle test;

[0026] Figure 6 This is a capture experiment diagram of BNCN-CBB-3 obtained in Example 3 of the present invention;

[0027] Figure 7 The electron paramagnetic resonance image of BNCN-CBB-3 obtained in Example 3 of this invention;

[0028] Figure 8 This is a schematic diagram of the degradation pathway of CQ by BNCN-CBB-3. Detailed Implementation

[0029] The invention will be further described with reference to the accompanying drawings. All reagents used in the following examples are conventional reagents of analytical purity and do not require further purification before use; the related preparation and detection methods are conventional methods.

[0030] Example 1

[0031] (1) The synthesis method of g-C3N4 is as follows: weigh a certain mass of melamine, place it in a crucible, use a tube furnace to heat it to 550°C in an air atmosphere at a rate of 5°C / min, heat and hold for 3 hours, cool to room temperature and take it out, grind it for later use.

[0032] (2) The synthesis method of BN-g-C3N4 is as follows: g-C3N4 and sodium borohydride (NaBH4) in a mass ratio of 0.8:0.5 are placed in a mortar and ground for 5 min. The powder is then transferred to a crucible and heated to 500℃ at a rate of 5℃ / min in a tube furnace under nitrogen protection. After heating for 1 h, the mixture is cooled to room temperature and then ground for later use.

[0033] (3) Add 100 ml of isopropanol (IPA) as a solvent, add 50 g of BN-g-C3N4 and stir for 1-2 h. The stirring method is magnetic stirring at a speed of 800-900 rpm. This solution is called solution A1. Add CsBr and BiBr3 in 10-50 ml of dimethyl sulfoxide (DMSO) at a mass ratio of 62.6:89.6. After the solution is fully dissolved, this solution is called solution A2. Slowly add solution A2 to solution A1. Pale yellow crystals precipitate out. Stir for 2 h to complete the reaction.

[0034] (4) The solid powder was recovered by centrifugation and washing. Specifically, the centrifuge speed was 6000 rpm, the centrifugation time was 5 min, the IPA was washed 3 times, and finally it was placed in a vacuum drying oven at 60℃ for 12-15 h and ground. The obtained solid powder was named BNCN-CBB-1.

[0035] Example 2

[0036] (1) The synthesis method of g-C3N4 is as follows: weigh a certain mass of melamine, place it in a crucible, use a tube furnace to heat it to 550°C in an air atmosphere at a rate of 5°C / min, heat and hold for 3 hours, cool to room temperature and take it out, grind it for later use.

[0037] (2) The synthesis method of BN-g-C3N4 is as follows: weigh g-C3N4 and sodium borohydride (NaBH4) in a mass ratio of 0.8:0.5 and place them in a mortar. After grinding for 5-10 min, transfer the powder to a crucible and heat it to 500℃ at a rate of 5-10℃ / min in a tube furnace under nitrogen protection. After heating for 1 h, cool it to room temperature and take it out for grinding.

[0038] (3) Add 100 ml of isopropanol (IPA) as a solvent, add 85 g of BN-g-C3N4 and stir for 1-2 h. The stirring method is magnetic stirring at a speed of 800-900 rpm. This solution is called solution A1. Add CsBr and BiBr3 in 10-500 ml of dimethyl sulfoxide (DMSO) at a mass ratio of 94.0:134.5. After the solution is fully dissolved, this solution is called solution A2. Slowly add solution A2 to solution A1. Pale yellow crystals precipitate out. Stir for 2 h to complete the reaction.

[0039] (4) The solid powder was recovered by centrifugal washing; specifically, the centrifuge speed was 6000 rpm, the centrifugation time was 5 min, the IPA was washed 3 times, and finally it was placed in a vacuum drying oven at 60℃ for 12 h and ground; the obtained solid powder was named BNCN-CBB-2.

[0040] Example 3

[0041] (1) The synthesis method of g-C3N4 is as follows: weigh a certain mass of melamine, place it in a crucible, use a tube furnace to heat it to 550°C in an air atmosphere at a rate of 5°C / min, heat and hold for 3 hours, cool to room temperature and take it out, grind it for later use.

[0042] (2) The synthesis method of BN-g-C3N4 is as follows: weigh g-C3N4 and sodium borohydride (NaBH4) in a mass ratio of 0.8:0.5 and place them in a mortar. After grinding for 5 minutes, transfer the powder to a crucible and heat it to 500℃ at a rate of 5-10℃ / min in a tube furnace under the protection of nitrogen. After heating for 1 hour, cool it to room temperature and take it out for grinding.

[0043] (3) Add 100 ml of isopropanol (IPA) as a solvent, add 115 g of BN-g-C3N4 and stir for 1-2 h. The stirring method is magnetic stirring at a speed of 800-900 rpm. This solution is called solution A1. Add CsBr and BiBr3 in 10-500 ml of dimethyl sulfoxide (DMSO) at a mass ratio of 109.6:159.6. After the solution is fully dissolved, this solution is called solution A2. Slowly add solution A2 to solution A1. Pale yellow crystals precipitate out. Stir for 2 h to complete the reaction.

[0044] (4) The solid powder was recovered by centrifugal washing; specifically, the centrifuge speed was 6000 rpm, the centrifugation time was 5 min, the IPA was washed 3 times, and finally it was placed in a vacuum drying oven at 60℃ for 12-15 h and ground; the obtained solid powder was named BNCN-CBB-3.

[0045] Example 4

[0046] (1) The synthesis method of g-C3N4 is as follows: weigh a certain mass of melamine, place it in a crucible, use a tube furnace to heat it to 550°C in an air atmosphere at a rate of 5°C / min, heat and hold for 3 hours, cool to room temperature and take it out, grind it for later use.

[0047] (2) The synthesis method of BN-g-C3N4 is as follows: weigh g-C3N4 and sodium borohydride (NaBH4) in a mass ratio of 0.8:0.5 and place them in a mortar. After grinding for 5-10 min, transfer the powder to a crucible and heat it to 500℃ at a rate of 5-10℃ / min in a tube furnace under nitrogen protection. After heating for 1 h, cool it to room temperature and take it out for grinding.

[0048] (3) Add 100 ml of isopropanol (IPA) as a solvent, add 150 g of BN-g-C3N4 and stir for 1-2 h. The stirring method is magnetic stirring at a speed of 800-900 rpm. This solution is called solution A1. Add CsBr and BiBr3 in 10-500 ml of dimethyl sulfoxide (DMSO) at a mass ratio of 125.3:179.3. After the solution is fully dissolved, this solution is called solution A2. Slowly add solution A2 to solution A1. Pale yellow crystals precipitate out. Stir for 2 h to complete the reaction.

[0049] (4) The solid powder was recovered by centrifugal washing; specifically, the centrifuge speed was 6000 rpm, the centrifugation time was 5 min, the IPA was washed 3 times, and finally it was placed in a vacuum drying oven at 60℃ for 12 h and ground; the obtained solid powder was named BNCN-CBB-4.

[0050] Example 5

[0051] Weigh out 50 mg of the catalyst and 50 ml of a 10 mg / L CQ solution, and place them in a 100 ml photocatalytic reactor. Allow the reactor to adsorb in the dark for 60 min until adsorption equilibrium is reached. Then, turn on the light source (white LED) for 5-60 min. Take a 3 mL sample every 10 min using a pipette, filter the catalyst using a 0.22 μm organic filter, and use a liquid UV spectrophotometer to detect the absorbance change at 342 nm. Calculate the photodegradation efficiency based on the test results.

[0052] After testing, the catalyst was recovered by centrifugation and washed 3–5 times with water and ethanol solutions, respectively. Finally, it was placed in a vacuum drying oven and dried at 60°C for 12 hours. This process was repeated 5 times, constituting 5 test cycles, to demonstrate the structural stability of the catalyst.

[0053] Example 6

[0054] The types of photocatalytically active substances in BNCN-CBB-3 were explored through capture experiments. 1 mmol / L of quenchers, such as isopropanol (IPA for ·OH quenching) and benzoquinone (BQ for ·O), were added to a typical photocatalytic reaction solution. 2- quenching), L-histidine (used for...) 1 O2 quenching) and triethanolamine (TEOA is used for h + (Quenching). The testing method is the same as the original photocatalytic reaction operation.

[0055] Referring to the accompanying drawings of this invention, the characteristics of the composite photocatalyst of this invention can be fully demonstrated. Figure 1 Scanning electron microscopy revealed that pure g-C3N4 formed a bulk morphology due to thermal condensation, while BN-g-C3N4, co-modified with B and N atoms, exhibited more wrinkles and exposed a larger specific surface area. This is attributed to the strong reduction of NaBH4 under high-temperature conditions. Figure 1 a and Figure 1 b). The Cs3Bi2Br9 sample exhibited polygonal nanosheets with an average size of 200 nm, demonstrating good uniformity and crystallinity. Figure 1 c). After the synthesis of the composite photocatalyst, Cs3Bi2Br9 nanosheets were grown in situ on the surface of BN-g-C3N4 ( Figure 1 d) The size and shape of both remain unchanged.

[0056] Figure 2 X-ray diffraction showed that the two characteristic peaks of g-C3N4 and BN-g-C3N4 at 13.1° and 27.4° corresponded to the (100) and (002) crystal planes, respectively. These two peaks can be attributed to the planar stacking of triazine groups and the interlayer stacking of aromatic structures, and also indicate that the structure of g-C3N4 remains unchanged during the doping of B and N atoms. The main diffraction peaks of Cs3Bi2Br9 were at 13.1, 16.1, 22.4, 27.2, 35.8, 39.4 and 45.5° (2θ), respectively, corresponding to the planes (100), (101), (102), (003), (202), (212) and (220). It is worth noting that the 27.3° diffraction peak in BNCN-CBB-3 is significantly broadened, while the intensities of other crystal planes are reduced. This not only indicates a strong interaction between BN-g-C3N4 and Cs3Bi2Br9, but also shows that the composite material has been successfully prepared.

[0057] Figure 3 The photodegradation test results showed that BNCN-CBB-3 could achieve a degradation efficiency of up to 98.6% for CQ within 60 minutes, which was much higher than that of the raw materials g-C3N4, BN-g-C3N4 and Cs3Bi2Br9. Figure 4 After five consecutive cycles, the CQ degradation rate of BNCN-CBB-3 still reached 90.3%, and significant inactivation was observed. Furthermore, according to XRD patterns after the fifth run... Figure 5 a) and SEM Figure 5 (b) The structure and morphology of BNCN-CBB-3 were found to be stable, indicating that it can be reused and has good structural stability. Therefore, BNCN-CBB-3 can be regarded as a highly efficient photocatalyst with potential applications in water treatment.

[0058] The types of reactive oxygen species produced by photocatalytic reactions were detected using capture experiments and electron spin resonance spectroscopy. For example... Figure 6 As shown, the degradation efficiency without any scavenging agent was 98.6%, while the addition of BQ and L-histidine reduced the degradation efficiency to only 15.6% and 22.9%, respectively. Therefore, it can be inferred that... 2- and· 1 O2 is the main active substance in the photodegradation of CQ by BNCN-CBB-3. Figure 7 As shown, under dark conditions, almost no obvious characteristic peaks were observed, which means there are very few or no O peaks. 2- or· 1 O2 species are produced. And under light conditions, DMPO-·O2- Four peaks with an intensity ratio of 1:2:2:1 were observed in the spectrum. Figure 7 a) and in TEMP-· 1 O2 was observed to have three peaks with an intensity ratio of 1:1:1. Figure 7 b) This indicates that under illumination, more superoxide radicals and singlet oxygen are generated, thereby stimulating carrier separation and inhibiting charge recombination.

[0059] Qualitative analysis of the model compound CQ and its major degradation products was performed using electrospray quadrupole electrostatic field orbital trap mass spectrometry (ESI-Q Orbitrap MS) in positive ion mode. Figure 8 The initial substrate was ionized in positive ion mode of mass spectrometry to yield the quasi-molecular ion [M+H] of the proton adduct of the corresponding product. + The product m / z is 320. First, the CN bond attached to the quinoline breaks to give product m / z 159, which further undergoes deamination to give product m / z 142. Next, CN bond cleavage yields products aminochloroquinoline m / z 179 and m / z 142. Further deethylation via deethyleneization yields product m / z 114, which then undergoes deethylation via deethyleneization to give product m / z 86, or deethylation via deethanering to give product m / z 112, which then undergoes deethylation via deethanering to give product m / z 84. Product m / z 142 is further oxidized to give product m / z 158, which further degrades via C / C bond cleavage to give product m / z 130 or triethylamine m / z 102. It is speculated that the oxidative degradation of these products yields small-molecule acids, ultimately producing H2O, CO2, and CO3. 2- NH4 + This allows for the complete degradation of the compound.

[0060] As illustrated by the above embodiments, the boron-doped nitrogen-defective graphitic carbon nitride / halogen perovskite (BN-g-C3N4 / Cs3Bi2Br9) of this invention possesses excellent structural stability and can efficiently treat CQ wastewater using photocatalysis. The preparation process is simple, exhibits high photocatalytic activity, and is easy to scale up. This research provides theoretical reference and data support for designing novel heteroatom-modified graphitic carbon nitride / halogen perovskite heterojunction photocatalysts for the removal of pollutants from water bodies.

Claims

1. The application of a BN-g-C3N4 / Cs3Bi2Br9 composite photocatalyst in the degradation of chloroquine phosphate, characterized in that, The preparation of the composite photocatalyst includes the following steps: Step 1: Synthesis of g-C3N4 Weigh out melamine, place it in a crucible, and heat it to 520-550 ℃ in an air atmosphere using a tube furnace at a heating rate of 5-10 ℃ / min. Hold the temperature for 3-5 h, then cool it to room temperature and grind it for later use. Step 2: Synthesis of BN-g-C3N4 Weigh g-C3N4 and sodium borohydride in a mass ratio of (0.8-1): (0.5-0.7) and place them in a mortar. Grind for 5-10 min and then transfer the powder to a crucible. In a tube furnace under nitrogen protection, heat the powder to 300-500 ℃ at a rate of 5-10 ℃ / min and heat for 1-2 h. After cooling to room temperature, remove the powder and grind it for later use. Step 3: Add 100-200 ml of isopropanol as a solvent, add 50-150 g of BN-g-C3N4 and stir for 1-2 h using a magnetic stirrer at a speed of 800-900 rpm. This solution is labeled A1. Add CsBr and BiBr3 in 10-500 ml of dimethyl sulfoxide at a mass ratio of (62.6-125.3):(89.6-179.3) until fully dissolved. This solution is labeled A2. Slowly add solution A2 dropwise to solution A1. Pale yellow crystals will precipitate. Stir for 2-3 h to complete the reaction. Step 4: Centrifugal washing to recover solid powder Specifically, the centrifuge speed is 6000~8000 rpm, the centrifugation time is 5~10 min, the IPA is washed 3~5 times, and finally it is placed in a vacuum drying oven at a drying temperature of 60~80 ℃ for 12~15 h, and then ground; the BN-g-C3N4 / Cs3Bi2Br9 composite photocatalyst is obtained. The prepared catalyst was placed in chloroquine phosphate wastewater with a concentration of 5-20 mg / L, mixed evenly, and adsorbed in the dark for 30-60 min. After reaching adsorption equilibrium, a low-power white LED was turned on for irradiation for 5-60 min. The mass ratio of the catalyst to the volume of the wastewater was 5-100 mg: 50-100 mL. Under the low-power white LED irradiation, the catalyst generated a large amount of active oxygen to catalyze the degradation of chloroquine phosphate precursor, and the degradation efficiency reached 68.5-98.6% after 60 min of irradiation.

2. The application of the BN-g-C3N4 / Cs3Bi2Br9 composite photocatalyst according to claim 1 in the degradation of chloroquine phosphate, characterized in that, Scanning electron microscopy revealed that the composite photocatalyst, with its Cs3Bi2Br9 grown in situ on the surface of BN-g-C3N4, showed no significant changes in size or morphology.

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