Preparation method and application of supported photocatalyst with photocatalytic performance in high-chlorine environment

Abstract

The application relates to a preparation method of a supported photocatalyst with photocatalytic performance in a high-chlorine environment and application thereof, and aims to solve the problem that the photocatalytic activity of most photocatalytic materials is obviously inhibited in a complex environment of high salt and high chlorine, leading to a low antibiotic removal rate in water bodies. The preparation method comprises the following steps: S1, synthesizing g-C3N4; S2, dissolving the g-C3N4 and anthraquinone-2-carboxylic acid in an acetonitrile solution, stirring and reacting to obtain an AQ-C3N4 photocatalytic composite material; S3, soaking polyurethane sponge in a polyethylene imine solution; and S4, preparing a suspension of the photocatalytic composite material, and then soaking the polyurethane sponge material with positive surface charges in the suspension. In the AQ-C3N4 photocatalytic material prepared by the application, AQ molecules are loaded on the surface of the g-C3N4 through covalent bond chemical coupling and pi-pi stacking, the separation and transmission efficiency of photoinduced carriers of the composite material is significantly enhanced, and the composite material has excellent photocatalytic activity.

Description

Technical Field

[0001] This invention relates to a method for preparing a supported photocatalyst with excellent photocatalytic performance in a high-chlorine environment, and to the application of the photocatalyst to treat antibiotics in high-chlorine water. Background Technology

[0002] With the advancement of modern industry and urbanization, increasingly complex organic compounds are being discharged into natural water bodies during production and daily life, posing a severe challenge to water environment protection and management. Taking the increasingly popular mariculture industry as an example, intensive mariculture often involves the excessive use of antibiotics, such as sulfadiazine, sulfamethoxazole, and tetracycline, to prevent diseases in farmed organisms like fish and shrimp. This long-term, unregulated, and excessive use of antibiotics significantly enhances their biotoxic effects in the environment, increases the probability of antibiotic resistance in aquatic microorganisms, and induces the development of antibiotic resistance genes. How to effectively treat these antibiotic pollutants in natural water bodies has become a hot topic.

[0003] Photocatalysis, due to its unique advantages, has broad application prospects in environmental remediation, including: readily available reaction conditions (i.e., close to ambient temperature and most ambient pressures); the ability to generate powerful oxidants from oxygen in the air; and the use of solar radiation as an energy source; the ability to completely decompose organic pollutants into harmless inorganic molecules such as CO2 and H2O; strong redox capabilities; low cost; no adsorption saturation; and long durability. Therefore, photocatalysis has increasingly gained worldwide attention and is widely used in new energy generation and environmental control strategies. Furthermore, wastewater discharged from the mariculture industry in coastal areas has caused increasingly serious antibiotic and resistance gene pollution in the marine environment. How to remove antibiotics from these high-salt, high-chlorine water bodies has become a key focus and challenge for researchers. Summary of the Invention

[0004] The purpose of this invention is to solve the problem that the photocatalytic activity of most photocatalytic materials is significantly inhibited in complex environments such as high salt and high chlorine, resulting in a low removal rate of antibiotics in water. The invention provides a method for preparing a photocatalyst with high photocatalytic performance in high chlorine water, and immobilizes the photocatalyst to remove antibiotics from the water.

[0005] The preparation method of the supported photocatalyst with photocatalytic performance under high chlorine environment of the present invention is carried out according to the following steps:

[0006] 1. Melamine is placed in a crucible and treated at 500-600℃ for 3-5 hours. After cooling to room temperature, it is washed and dried to obtain g-C3N4.

[0007] II. 0.3-0.5 g of g-C3N4 obtained in step I and 70-90 mg of anthraquinone-2-carboxylic acid (AQ-COOH) are dissolved in acetonitrile solution, and after ultrasonic mixing, stirring reaction is carried out at a temperature of 40-60 DEG C, and after cooling to room temperature, the surface negative electric AQ-C3N4 photocatalytic composite material is obtained after washing and drying;

[0008] III. The polyurethane sponge (PUF) is first soaked in deionized water and treated by ultrasonic, and after washing and drying, the dried polyurethane sponge is obtained, then the dried polyurethane sponge is soaked in a polyethyleneimine solution (PEI) with a concentration of 0.4-0.6 wt%, and after washing and drying, the surface positive electric polyurethane sponge (PUF) material is obtained;

[0009] IV. The AQ-C3N4 photocatalytic composite material and polyvinylpyrrolidone (PVP) are dissolved in deionized water, and after ultrasonic treatment, a suspension is obtained, then the surface positive electric polyurethane sponge material is immersed in the suspension, and after repeated taking out, extruding and soaking, the immobilized photocatalyst with photocatalytic performance (AQ-C3N4-PUF composite photocatalytic sponge) is obtained after ultrasonic cleaning and drying in turn.

[0010] The application of the supported photocatalyst with photocatalytic performance in a high-chlorine environment is that the photocatalyst is placed in a high-chlorine water body, and sulfonamide antibiotic pollutants are photocatalytically degraded under light conditions.

[0011] The g-C3N4 prepared in the application has a relatively thick graphite layer stack structure, a relatively smooth surface, and no obvious pore size, and the AQ coupling does not affect the surface morphology of the g-C3N4.

[0012] Through photocatalytic degradation of SDZ experiment analysis, the g-C3N4 material modified by anthraquinone-2-carboxylic acid has the optimal photocatalytic activity in a high-chlorine water body, and as the AQ loading amount increases, the degradation efficiency is obviously improved, and the degradation rate of 20% AQ-C3N4 to SDZ reaches 89% within 120 min, and the reaction rate is 5.12 times that of pure g-C3N4. The morphology and structure characteristics of the g-C3N4 material after AQ loading do not change obviously, the surface chemical property analysis result shows that the AQ molecules are loaded on the surface of the g-C3N4 through covalent bond chemical coupling and π-π stacking; the optical property analysis result shows that the band gap of the pure g-C3N4 and the AQ-C3N4 composite material is basically the same, but the conduction band position (CB) is-0.833 and-0.503 V (vs. NHE) respectively; the photoelectric effect analysis result shows that the separation and transmission efficiency of the photo-generated carriers of the composite material after AQ loading is significantly enhanced, and the photocatalytic activity is more excellent.

[0013] The AQ-C3N4 photocatalytic material prepared in the application has AQ molecules loaded on the surface of g-C3N4 by covalent bond chemical coupling and π-π stacking and the like, the separation and transmission efficiency of photo-generated carriers of the composite material is significantly enhanced, and the photocatalytic activity is more excellent. The degradation rate of the optimal composite material 20% AQ-C3N4 to SDZ in a high-chlorine water body within 180 min reaches 93.7%. The degradation rate of the AQ-C3N4-PUF composite photocatalytic sponge prepared in the application to SDZ in a high-chlorine water body within 120 min reaches 100%. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 The scanning electron microscope images of the AQ-C3N4 photocatalytic material prepared in the examples, wherein (a) and (b) respectively show the 5k and 10k SEM images of g-C3N4, (c) and (d) respectively show the low-magnification and high-magnification SEM images of the AQ-C3N4 composite material;

[0015] Figure 2 The degradation rate curve of the AQ-C3N4 photocatalytic material in the examples to SDZ in different systems;

[0016] Figure 3 The pseudo-first-order reaction kinetics fitting curve of the AQ-C3N4 photocatalytic material in the examples to SDZ in different systems;

[0017] Figure 4 The degradation rate curve of the AQ-C3N4 photocatalytic material prepared in the examples to SDZ under different dosages;

[0018] Figure 5 The pseudo-first-order reaction kinetics fitting curve of the AQ-C3N4 photocatalytic material prepared in the examples to SDZ under different dosages;

[0019] Figure 6 The degradation rate curve of the AQ-C3N4 photocatalytic material prepared in the examples to SDZ under different Cl - concentrations;

[0020] Figure 7 The pseudo-first-order reaction kinetics rate constant K - of the AQ-C3N4 photocatalytic material prepared in the examples to SDZ under different Cl obs test graphs;

[0021] Figure 8 The degradation efficiency test graphs of the AQ-C3N4 photocatalytic material prepared in the examples to different SAs, wherein sulfanilamide (SA), sulfonamides quinolone (SQX), sulfamethoxazole (SMX), sulfapyridine (SP) and sulfadiazine (SDZ);

[0022] Figure 9 The 4-cycle test graph of the AQ-C3N4 photocatalytic material prepared for the example to photocatalytic degradation of SDZ;

[0023] Figure 10 The degradation rate curve of the AQ-C3N4-PUF photocatalytic sponge prepared for the example under different systems SDZ;

[0024] Figure 11 The schematic diagram of the photocatalytic mechanism of the AQ-C3N4 photocatalytic material prepared for the example in the high-chlorine water body. DETAILED DESCRIPTION

[0025] Specific implementation one: the preparation method of the supported photocatalyst with photocatalytic performance in a high-chlorine environment is implemented according to the following steps:

[0026] I. Melamine is placed in a crucible and treated at a temperature of 500-600°C for 3-5h. After cooling to room temperature, the g-C3N4 is obtained after washing and drying;

[0027] II. 0.3-0.5g of g-C3N4 obtained in step I and 70-90mg of anthraquinone-2-carboxylic acid (AQ-COOH) are dissolved in an acetonitrile solution, and after ultrasonic mixing, the reaction is stirred at a temperature of 40-60°C. After cooling to room temperature, the AQ-C3N4 photocatalytic composite material with a negative surface charge is obtained after washing and drying;

[0028] III. The polyurethane sponge (PUF) is first immersed in deionized water and ultrasonically treated, and then washed and dried to obtain dry polyurethane sponge. Then the dry polyurethane sponge is immersed in a polyethyleneimine solution (PEI) with a concentration of 0.4-0.6wt%, and after washing and drying, the polyurethane sponge (PUF) material with a positive surface charge is obtained;

[0029] IV. The AQ-C3N4 photocatalytic composite material and polyvinylpyrrolidone (PVP) are dissolved in deionized water, and after ultrasonic treatment, a suspension is obtained. Then the polyurethane sponge material with a positive surface charge is immersed in the suspension, and after repeated taking out, squeezing and soaking, it is sequentially ultrasonically cleaned and dried to obtain the immobilized photocatalyst (AQ-C3N4-PUF composite photocatalytic sponge) with photocatalytic performance.

[0030] In this embodiment, g-C3N4 and AQ-COOH are used as raw materials for the photocatalyst in a high-chlorine environment, and are prepared by heat treatment and direct catalytic coupling. Under visible light irradiation, the electrons on the AQ-C3N4 composite material jump from the valence band to the conduction band, generating photo-generated electrons (e - ) and photo-generated holes (h+ ). Subsequently, anthraquinone molecules (AQ) will quickly capture photo-generated electrons to generate semiquinone radicals (AQ ·- ), which in turn continue to react with O2 to generate ·O2 - and are oxidized to AQ, which is much faster than O2 directly obtaining e - , while inhibiting the recombination rate of photo-generated carriers. On the other hand, h + and OH - react to produce ·OH, which further reduces the recombination of carriers, and then ·OH quickly reacts with Cl - to generate ·Cl, which continues to react with Cl - to generate ·Cl2 - , and in addition, h + can also directly transfer electrons to pollutants, and finally ·O2 - , h + and ·Cl2 - jointly act on the degradation process of SDZ.

[0031] In this embodiment, the supported photocatalyst in a high-chlorine environment is prepared by using AQ-C3N4 and polyurethane sponge as raw materials through electrostatic self-assembly method. Among them, the AQ-C3N4 photocatalyst surface is negatively charged, the polyurethane sponge material surface is positively charged after being modified by polyethyleneimine, and the AQ-C3N4 photocatalyst is dispersed in water by using polyvinylpyrrolidone. The photocatalyst is tightly fixed on the surface of the polyurethane sponge through the electrostatic effect, forming a fixed photocatalytic material.

[0032] Specific implementation method two: the difference between this embodiment and specific implementation method one is that in step one, the temperature is raised to 500-600°C at a rate of 2.5-5°C·min -1 , and then the temperature is kept for 3-5h.

[0033] Specific implementation method three: the difference between this embodiment and specific implementation method one or two is that in step one, the washing is repeated washing with anhydrous ethanol and deionized water.

[0034] Specific implementation method four: the difference between this embodiment and one of specific implementation methods one to three is that in step two, the stirring reaction time is 10-14h at a temperature of 40-60°C.

[0035] Specific implementation method five: the difference between this embodiment and one of specific implementation methods one to four is that in step two, the drying temperature is 50-70°C.

[0036] Specific embodiment six: the difference between this embodiment and one of the specific embodiments one to five is that in step two, 0.4 g of g-C3N4 obtained in step one and 80 mg of anthraquinone-2-carboxylic acid (AQ-COOH) are dissolved in an acetonitrile solution, and after ultrasonic mixing, the reaction is stirred at a temperature of 40-60°C for 10-12 h.

[0037] Specific embodiment seven: the difference between this embodiment and one of the specific embodiments one to six is that in step three, the polyurethane sponge is soaked in deionized water and ultrasonic treatment is performed for 20-40 min.

[0038] Specific embodiment eight: the difference between this embodiment and one of the specific embodiments one to seven is that in step three, the dry polyurethane sponge is soaked in a polyethyleneimine solution with a concentration of 0.4-0.6 wt% for 8-12 min.

[0039] Specific embodiment nine: the difference between this embodiment and one of the specific embodiments one to eight is that in step four, the mass concentration of the AQ-C3N4 photocatalytic composite in the suspension is 1-5 g / L.

[0040] Example: the preparation method of the supported photocatalyst with photocatalytic performance in a high chlorine environment is implemented according to the following steps:

[0041] I. 10 g of melamine is placed in an aluminum chloride crucible, which is placed in a muffle furnace and heated at a rate of 2.5°C·min -1 to 550°C and kept for 3 h. After cooling to room temperature, the light yellow powder collected is repeatedly washed with anhydrous ethanol and deionized water to remove unreacted melamine. After drying at a temperature of 60°C, g-C3N4 is obtained;

[0042] II. 0.4 g of g-C3N4 obtained in step one and 80 mg of anthraquinone-2-carboxylic acid (AQ-COOH) are dissolved in 40 ml of acetonitrile solution. After ultrasonic treatment of the suspension for 30 min, the reaction is stirred at a temperature of 50°C for 12 h. After cooling to room temperature, the remaining AQ-COOH is removed by repeatedly washing with anhydrous ethanol and deionized water several times. After filtration and drying (drying temperature is 60°C), a negatively charged AQ-C3N4 photocatalytic composite material is obtained;

[0043] III. The polyurethane sponge is first soaked in deionized water and ultrasonic treated for 30 min, and then repeatedly washed with anhydrous ethanol and deionized water. The dried polyurethane sponge is obtained by drying in an oven at 60°C for 24 h. Then, the dried polyurethane sponge is soaked in a polyethyleneimine solution (PEI) with a concentration of 0.5 wt% for 10 min. The positively charged PEI is protonated and used as a surface coating. After washing with deionized water and drying, a positively charged polyurethane sponge (PUF) material is obtained.

[0044] Four, AQ-C3N4 photocatalytic composite material and 40 mg PVP were dissolved in deionized water, the concentration of AQ-C3N4 photocatalytic composite material in deionized water was 5 g / L, a suspension was obtained after ultrasonic treatment for 10 min, then the surface positive charged PUF material was immersed in the suspension for 10 min, and after repeated taking out, extruding and soaking, after drying, the catalyst material with poor loading was removed by repeatedly cleaning with anhydrous ethanol and deionized water, and the immobilized photocatalyst with photocatalytic performance (AQ-C3N4-PUF composite photocatalytic sponge) was obtained after drying.

[0045] The AQ-C3N4-PUF composite photocatalytic sponge obtained in this example was used for experiments. In the process of photocatalytic degradation of high concentration Cl - under the condition of SDZ, in addition to the photo-generated electrons and holes generated by the excitation of the composite material, there are a series of active free radicals such as · O2 - , H2O2, chlorine free radical ( · Cl) and super chloro radical ( · Cl2 - ). - In order to confirm the interaction of AQ-C3N4 composite material, Cl - and visible light, photocatalytic degradation experiments of Cl - / sunlight, AQ-C3N4 / sunlight, AQ-C3N4 / Cl - / sunlight, g-C3N4 / sunlight and g-C3N4 / Cl - / sunlight were carried out.

[0046] The removal effect of SDZ under high concentration Cl - light is less than 3%, and it is basically not photolyzed. When g-C3N4 is added as a photocatalytic material, the degradation rate of the system is only 52.07% in 180 min, and after adding 0.5M Cl - , the degradation rate of the system decreases to 42.65%, which shows that g-C3N4 can be excited to degrade SDZ under sunlight, but high concentration Cl - can inhibit the photocatalytic efficiency. In the system with AQ-C3N4 composite material, the degradation rate of SDZ in 180 min reaches 86.77%, which is greatly improved compared with unmodified g-C3N4, and after adding 0.5M Cl - , the degradation rate of the system increases to 93.72%. AQ-C3N4 / illumination, AQ-C3N4 / Cl - / illumination, C3N4 / illumination and C3N4 / ClThe light rate constant k values are 0.004, 0.0028, 0.011 and 0.014 min -1 , wherein AQ-C3N4 / Cl - The k value of the light system is C3N4 / Cl - 5 times, which shows that the AQ-C3N4 composite material can not only significantly improve the photocatalytic activity, but also may and Cl - Synergistically act on the degradation process of SDZ.

[0047] AQ-C3N4 composite material, Cl - and visible light synergistically promote the degradation of SDZ, and the SDZ degradation rate reaches 94% within 180 min under the optimal reaction condition, and the reaction rate constant k value is C3N4 / Cl - 5 times; from the three aspects of removal efficiency, reaction rate and dosage cost, the most suitable reaction condition is determined as 0.5 g / L of AQ-C3N4 composite material and 30 g / L of NaCl.

[0048] The AQ-C3N4-PUF composite photocatalytic sponge obtained in this embodiment is used for experiments. In order to confirm the efficiency of the AQ-C3N4-PUF composite sponge photocatalytic degradation of high-concentration Cl - under the condition of SDZ, photocatalytic degradation experiments of three systems of adsorption, photolysis and AQ-C3N4-PUF composite photocatalytic sponge are carried out. The prepared composite sponge material has extremely excellent photocatalytic activity, and realizes 100% degradation rate of SDZ in high-chlorine water body within 120 min, which is because the sponge surface is loaded with a large amount of AQ-C3N4 composite material, which provides more active sites for the reaction.

[0049] Figure 1 The scanning electron microscope graph of g-C3N4 has a relatively thick graphite layer stack structure, and the surface is relatively smooth, without obvious pore size, and the AQ coupling does not affect the surface morphology of g-C3N4. Figures 2-3 The degradation effect of SDZ in different reaction systems can be seen that the AQ-C3N4 composite material can not only significantly improve the photocatalytic activity, but also may and Cl - Synergistically act on the degradation process of SDZ. Figures 4-5 The dosage of the AQ-C3N4-PUF composite photocatalytic sponge affects the SDZ degradation curve, which shows that 0.5 g / L can be selected as the optimal dosage of the catalyst material AQ-C3N4-PUF except the carrier part in the actual application. Figures 6-7 It can be seen that when the chlorine ion concentration in the high-chlorine water body reaches a certain value, the photocatalyst reaction rate is extremely fast. Figures 8-9It can be seen that the AQ-C3N4 composite material has excellent performance in the degradation of various sulfonamide antibiotics, and the feasibility in actual wastewater treatment is guaranteed. After 4 cycles, the material photocatalytic degradation rate can still maintain above 65%, so it is considered to have good stability and reusability. From Figure 10 It can be seen that the supported photocatalyst AQ-C3N4-PUF has excellent treatment performance in high-chlorine water bodies, so the immobilization method is feasible and effective. Figure 11 It can be seen from the above that AQ and Cl - The system promotes the photocatalytic degradation of SDZ.

Claims

1. A method for preparing a supported photocatalyst with photocatalytic performance under high chlorine conditions, characterized in that... The preparation method is realized according to the following steps: I. Melamine is placed in a crucible, treated at a temperature of 500-600 DEG C for 3-5 h, and after cooling to room temperature, washed, dried to obtain g-C3N4. II. 0.3-0.5 g of g-C3N4 obtained in step I and 70-90 mg of anthraquinone-2-carboxylic acid are dissolved in acetonitrile solution, uniformly mixed by ultrasonic, and stirred at a temperature of 40-60 DEG C for reaction, cooled to room temperature, washed, dried to obtain a surface negative charged AQ-C3N4 photocatalytic composite material; III. The polyurethane sponge is first soaked in deionized water and treated by ultrasonic for 20-40 min, washed, dried to obtain dry polyurethane sponge, then the dry polyurethane sponge is soaked in a polyethyleneimine solution with a concentration of 0.4-0.6 wt%, the soaking time is 8-12 min, washed, dried to obtain a surface positive charged polyurethane sponge material; IV. The AQ-C3N4 photocatalytic composite material and polyvinylpyrrolidone are dissolved in deionized water, treated by ultrasonic to obtain a suspension, the mass concentration of AQ-C3N4 photocatalytic composite material in the suspension is 1-5 g / L, then the surface positive charged polyurethane sponge material is immersed in the suspension, repeatedly taken out, squeezed and soaked, then sequentially washed by ultrasonic and dried to obtain a supported photocatalyst with photocatalytic performance.

2. The method for preparing the supported photocatalyst having photocatalytic properties in a high chlorine environment according to claim 1, characterized in that In step one, the temperature is 2.5~5℃•min -1 The temperature is increased to 500-600℃ at a certain rate, and then kept at that temperature for 3-5 hours.

3. The method for preparing the supported photocatalyst having photocatalytic properties in a high chlorine environment according to claim 1, characterized in that The washing in step I is repeated washing with anhydrous ethanol and deionized water.

4. The method for preparing the supported photocatalyst having photocatalytic properties in a high chlorine environment according to claim 1, characterized in that In step II, the stirring reaction is carried out at a temperature of 40-60 DEG C for 10-14 h.

5. The method for preparing the supported photocatalyst having photocatalytic properties in a high chlorine environment according to claim 1, characterized in that The drying temperature in step II is 50-70 DEG C.

6. The method for preparing the supported photocatalyst having photocatalytic properties in a high chlorine environment according to claim 1, characterized in that In step II, 0.4 g of g-C3N4 obtained in step I and 80 mg of anthraquinone-2-carboxylic acid are dissolved in acetonitrile solution, uniformly mixed by ultrasonic, and stirred at a temperature of 40-60 DEG C for 10-12 h.

7. The use of the supported photocatalyst with photocatalytic properties prepared according to the method of claim 1. The supported photocatalyst with photocatalytic performance is placed in a high-chlorine water body, and the sulfonamide antibiotic pollutants are photocatalytically degraded under light conditions.

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