GB2618635A

GB2618635A - Photocatalytic material for degrading tetracycline in wastewater and preparation method thereof

Info

Publication number: GB2618635A
Application number: GB2216790.2A
Authority: GB
Inventors: Song Zhi; Liu Boxia
Original assignee: North Minzu University
Current assignee: North Minzu University
Priority date: 2022-05-10
Filing date: 2022-11-10
Publication date: 2023-11-15
Also published as: CN114700093B; GB202216790D0; CN114700093A

Abstract

A method for preparation of a photocatalytic material for the degradation of tetracycline in wastewater. Zinc oxide nanorods are placed into an aqueous suspension comprising tungsten trioxide, polyvinyl pyrrolidone. A silver salt is then added to the suspension followed by a phosphate salt. A second aqueous mixture comprising aluminium hydroxide, sodium hydroxide, tetrapropylammonium hydroxide and colloidal silica is aged between 75 and 95 ℃ for between 8 and 24 h to obtain a molecular sieve synthesis agent. The molecular synthesis agent is added to the zinc oxide nanorod suspension and mixed using an ultrasonic treatment, the mixture is then subjected to a microwave hydrothermal reaction at 120 to 180 ℃ for 10 to 120 mins to obtain the photocatalytic material.

Description

PHOTOCATALYTIC MATERIAL FOR DEGRADING TETRACYCLINE IN

WASTEWATER AND PREPARATION METHOD THEREOF

TECHNICAL FIELD

100011 The present disclosure relates to the technical field of photocatalytic materials, in particular to a photocatalytic material for degrading tetracycline in wastewater and a preparation method thereof

BACKGROUND

100021 Tetracycline antibiotics play an important role in the treatment of human diseases and livestock and poultry diseases and in promoting the growth of livestock and poultry, and are widely used in the medical industry and animal husbandry. As one of the main producing areas of tetracycline active pharmaceutical ingredients (APIs) in China, Ningxia plays an extremely important role in the development of tetracycline antibiotics in China.

100031 However, due to a stable nature, tetracycline is difficult to degrade in the natural environment and has ecotoxicity, posing a threat to the ecological environment. Therefore, it has become a highly important problem in the development of local economic sustainable line to deal with the residual tetracycline in pharmaceutical wastewater.

100041 To this end, those skilled in the art have proposed a technology based on photocatalytic degradation of tetracycline in wastewater. The photocatalytic degradation technology can conduct reactions at a room temperature, and has reaction products of water and carbon dioxide without secondary pollution, which integrates environmental protection and cost-effectiveness. Therefore, this technology has a bright future in environmental governance. A commonly used photocatalytic material in the prior art is carbon nitride, but the carbon nitride has a poor photocatalytic degradation effect on tetracycline, and is difficult to recover, easily leading to secondary pollution. Therefore, it is quite necessary to find a novel photocatalytic technology.

100051 In order to solve the above problems, the present disclosure proposes a photocatalytic material for degrading tetracycline in wastewater and a preparation method thereof

SUMMARY

100061 In order to solve the above deficiencies in the prior art, the present disclosure provides a photocatalytic material for degrading tetracycline in wastewater and a preparation method thereof In the present disclosure, the photocatalytic material has a high visible light response, and can efficiently degrade the tetracycline in wastewater under visible light.

100071 In the present disclosure, the photocatalytic material for degrading tetracycline in wastewater and the preparation method thereof are achieved by the following technical solutions: [0008] A first objective of the present disclosure is to provide a preparation method of a photocatalytic material for degrading tetracycline in wastewater, including the following steps: [0009] immersing a zinc oxide (ZnO) nanorod array into a suspension A, adding a silver salt, mixing well by stirring, adding a phosphate and mixing well by stirring to obtain a uniform suspension B; [00101 dispersing aluminum hydroxide, sodium hydroxide, and tetrapropylammonium hydroxide evenly in an aqueous solvent, adding colloidal silica and mixing well, and subjecting an obtained mixture to aging at 75°C to 95°C for 8 h to 24 h to obtain a molecular sieve synthesis agent; [0011] adding the molecular sieve synthesis agent to the suspension B to conduct an ultrasonic treatment, and conducting a microwave hydrothermal reaction at 120°C to 180°C for 10 mm to 120 min to obtain the photocatalytic material; where [0012] the suspension A is prepared from tungsten trioxide, polyvinylpyrrolidone, and the aqueous solvent.

[0013] Further, the molecular sieve synthesis agent and the suspension B have a volume ratio of 1:(1-3).

[0014] Further, in the molecular sieve synthesis agent, the aluminum hydroxide, the sodium hydroxide, the tetrapropylammonium hydroxide, and the aqueous solvent have a dosage ratio of 0.3 mmol: (7-8) mmol: (1-2) mL. (1-1 5) mL; and [0015] the colloidal silica and the aluminum hydroxide have a mass ratio of (25-30):1.

[0016] Further, in the suspension A, the tungsten trioxide, the polyvinylpyrrolidone, and the aqueous solvent have a dosage ratio of 1 mmol: 0.1 g: (20-40) mL [0017] Further, the silver salt is selected from the group consisting of silver acetate and silver nitrate; and [0018] the phosphate is selected from the group consisting of sodium phosphate and ammonium dihydrogen phosphate.

[0019] Further, the silver salt and the suspension A have a dosage ratio of (10-20) mmol: 100 mL; and [0020] the silver salt and the phosphate have a molar ratio of (2-4):1.

[0021] Further, the stirring after adding the silver salt is conducted at 150 r/min to 250 r/min for 20 min to 40 min; and [0022] the stirring after adding the phosphate is conducted at 50 r/min to 150 r/min for 30 min to 60 min 100231 Further, the ZnO nanorod array is prepared by the following steps: [0024] dispersing a zinc salt A and hexamethylenetetramine uniformly in the aqueous solvent to obtain a uniform ZnO precursor solution for later use; [0025] dispersing a zinc salt B and ethanolamine uniformly in 2-methoxyethanol to form a seed layer solution; immersing a cleaned substrate into the seed layer solution to prepare a ZnO seed layer on the substrate, to obtain a substrate with the ZnO seed layer on a surface; and [0026] immersing the substrate with the ZnO seed layer on a surface in the ZnO precursor solution, and conducting a hydrothermal reaction to obtain the ZnO nanorod array; where [0027] the zinc salt A and the zinc salt B each are any one selected from the group consisting of zinc nitrate, zinc chloride, zinc sulfate, zinc acetate, zinc citrate, zinc gluconate, and zinc lactate.

[0028] Further, the zinc salt A, the hexamethylenetetramine, and the aqueous solvent have a dosage ratio of 1 mmol: 1 mmol: (20-40) ml; and [0029] the zinc salt B, the ethanolamine, and the 2-methoxyethanol have a dosage ratio of (0.5-2) mmol: 1 mmol: (30-60) ml.

[0030] Further, the microwave hydrothermal reaction is conducted at 2.45 Gliz and 800 W. [0031] A second objective of the present disclosure is to provide a photocatalytic material prepared by the preparation method.

[0032] Compared with the prior art, the present disclosure has the following beneficial effects: [0033] In the present disclosure, a layer of dense ZnO (ZnO) nanorod array is formed on a ZnO seed crystal through a hydrothermal reaction. The ZnO nanorod array as a seed crystal is immersed in a suspension A prepared by tungsten trioxide, polyvinylpyrrolidone, and an aqueous solvent, such that substances in the suspension A (such as the tungsten trioxide) can be uniformly distributed inside and around the ZnO nanorod array. Sequentially; a silver salt and a phosphate are added into the suspension A and mixed uniformly to form a uniform suspension B. During the stirring, a part of the silver salt and phosphate may form A831304 crystal nuclei on a surface of the ZnO nanorod array, thus changing hydrophilicity of the ZnO nanorod array surface. In addition, the crystal nucleus of Ag3PO4 is formed in an aqueous solution containing tungsten trioxide, such that the tungsten trioxide can effectively protect the crystal nucleus of Ag51304 to stably exist in the aqueous solution, which is helpful for the formation of a ZnO-Ag3PO4-W03 composite in a later stage of the hydrothermal reaction. By the ultrasonic treatment, components in the molecular sieve synthesis agent are uniformly dispersed around the ZnO-Ag3PO4-W03 composite; and after the microwave hydrothermal reaction, the ZnO-A834'04-W03 composite can be rapidly encapsulated in pores of a zeolite with a hierarchically porous MFI nanosheet structure (ZSM-5) during gradual formation of the zeolite with a hierarchically porous MFI nanosheet structure, thereby obtaining the photocatalytic material of the present disclosure. Through mutual cross-linking or intercalation between the components, a heterogeneous interface is formed between the components and a recombination efficiency of electron-hole pairs in the material is reduced, thereby improving a visible light absorption properties of the material and thereby improving a photocatalytic efficiency of the material.

100341 In the present disclosure, the catalytic material has ZnO/Ag3PO4/W03 ternary nanoclusters. In the ZnO/Ag11304/W03 ternary nanoclusters, the ECB of WO3 (0.61 eV-vs-NHE) is more negative than that of E-(02/H202) (0.68 eV-vs-NHE), such that excited electrons are finally captured by 02 molecules adsorbed on a surface of the ZnO-Ag3PO4-W03 nanoclusters to generate H202, and the H202 provides OH by accepting electrons. In addition, the ECB of WO; is more positive than that of E (02/02) (-0.33 eV vs NEE), and dissolved 02 molecules cannot be directly oxidized to 02-by the excited electrons; meanwhile, the EVB (2.64 eV vs NHE) of Ag31304 is more positive than that of E (01110H) (1.99 eV vs NEE), and holes generated in the Ag3PO4 can oxidize H20/0H-to form OH radicals. Therefore, the ZnO/Ag31304/W03 ternary nanoclusters enable the catalytic material of the present disclosure to help improve photo-induced charge transfer, suppress a charge recombination rate, and promote generation of more oxidants (OH and holes). In addition, the ZnO/Ag31304/W03 ternary nanoclusters are encapsulated in the zeolite with a hierarchically porous MFI nanosheet structure, so as to avoid the self-agglomeration of ZnO-Ag31304-W03, such that the ZnO-Ag31304-W03 ternary nanoclusters exist uniformly and stably. Thus, a stability of properties of the photocatalytic material is ensured, thereby further improving a photocatalytic activity.

[0035] In the present disclosure, the photocatalytic material has a high visible light response, and can efficiently degrade the tetracycline in wastewater under visible light. In addition, the photocatalytic material is fixed on a glass substrate to participate in a catalytic reaction, which does not dissolve in water to cause secondary pollution to water, and is convenient for recycling.

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] FIG. 1 shows a schematic diagram of element distribution in a photocatalytic material of Example 1; [0037] FIG. 2 shows a test result of a degradation efficiency of tetracycline by the photocatalytic material of the present disclosure; and [0038] FIG. 3 shows a test result of a stability of a photocatalytic performance of the photocatalytic material of Example 1.

DETAILED DESCRIPTION OF THE EMBODIMENTS

100391 The technical solutions in the examples of the present disclosure will be clearly and completely described below with reference to the accompanying drawings in the examples of the

present disclosure.

[0040] Example 1

100411 In this example, a preparation method of a photocatalytic material for degrading tetracycline in wastewater included the following steps: [0042] 1) Preparation of a substrate with a ZnO seed layer on a surface: 100431 a zinc salt B and ethanolamine were uniformly dispersed in 2-methoxyethanol to form a seed layer solution; 50 mL of the seed layer solution was coated on a substrate by a dip-coating method to form a ZnO seed layer, to obtain a substrate with the ZnO seed layer on a surface; where 100441 the zinc salt B, the ethanolamine, and the 2-methoxyethanol had a dosage ratio of 1 mmol: 1 mmol: 40 ml; and [0045] the zinc salt B was zinc nitrate.

[0046] 2) Preparation of a ZnO precursor solution: [0047] according to a dosage ratio of 1 mmol: 1 mmol: 30 ml, a zinc salt A and hexamethylenetetramine were uniformly dispersed in an aqueous solvent, and an obtained mixture was magnetically stirred at 60°C to form a homogeneous ZnO precursor solution; where [0048] the zinc salt A was zinc acetate.

[0049] 3) Preparation of a ZnO nanorod array: [0050] the substrate with the ZnO seed layer on a surface was immersed in the ZnO precursor solution, followed by conducting a hydrothermal reaction at 98°C for 4 h, a product was cooled to a room temperature, filtered, washed with deionized water 3 times, and air-dried naturally to obtain the ZnO nanorod array; where reaction mechanisms were as follows: 100511 (CH2)6N4+H2 0 ->HCHO+NTL. H20 (1) [0052] NH3 H20->INH4-+OH-(2) [0053] Zn(NO3)2+2NH4OH->Zn(OH)2,1+2NE4IN-03 (3) [0054] Zn(OH)2+4NE140H->Zn(NH3)42++20H-+4H20 (4) [0055] Zn(NH3),42++01-1--,Zn04,+4NH3+H20 (5).

[0056] A ZnO seed layer was prepared on the substrate, the ZnO seed layer was placed in the ZnO precursor solution, and a very uniform ZnO nanorod array was obtained through a hydrothermal reaction.

[0057] 4) Preparation of a suspension B: [0058] according to a dosage ratio of 1 mmol 01 g: 30 mL, W03 and polyvinylpyrrolidone were uniformly distributed in deionized water by an ultrasonic treatment to obtain a suspension A; where the polyvinylpyrrolidone could enhance an adhesiveness of the suspension A, thereby improving adhesion or coating of the W03 on a surface of ZnO or Ag3PO4; [0059] the ZnO nanorod array was immersed in the suspension A, such that a part of the W03 in the suspension A could enter an interior or gap of the ZnO nanorod array, so as to form a ZnO/W03 composite structure in the ZnO nanorod array; other tungsten trioxide was evenly distributed around the ZnO nanorod array, and the W03 distributed in the suspension A could prevent the subsequent Ag3PO4 crystal nuclei from dissolving in water; as a result, the Ag31304 crystal nuclei were stably exist in the aqueous solution, which was helpful for a catalyst stability of the photocatalytic material during use; and [0060] a silver salt was added, and stirred at 200 r/min for 30 min, a phosphate was added, and stirred at 100 r/min for 40 min to form a uniform suspension B; during the stirring, after a part of the silver salt and phosphate met, the Ag3PO4 crystal nuclei were formed on a surface of the ZnO nanorod array; meanwhile, a part of W03 in the suspension B could be coated on the surface of the ZnO nanorod array together with the A83PO4 crystal nuclei to form ZnO/A83PO4/W03 clusters; where [0061] the silver salt was silver acetate; [0062] the phosphate was ammonium dihydrogen phosphate; [0063] the silver salt and the suspension A had a dosage ratio of 15 mmol 100 m L and [0064] the silver salt and the phosphate had a molar ratio of 3:1.

[0065] 5) Microwave hydrothermal synthesis of the photocatalytic material: [0066] aluminum hydroxide, sodium hydroxide, and tetrapropylammonium hydroxide were dispersed evenly in an aqueous solvent, colloidal silica was added and mixed well, and an obtained mixture was subjected to aging at 85°C for 12 h to obtain a molecular sieve synthesis agent; where [0067] the aluminum hydroxide, the sodium hydroxide, the tetrapropylammonium hydroxide, and the aqueous solvent had a dosage ratio of 0.3 mmol: 7.6 mmol: 1.6 ml: 1.2 mL; and [0068] the colloidal silica and the aluminum hydroxide had a mass ratio of 27:1; and [0069] the suspension B was added dropwise to the molecular sieve synthesis agent, and components in the molecular sieve synthesis agent were uniformly dispersed in the surrounding of ZnO/Ag3PO4/W03 clusters by an ultrasonic treatment for 30 min, and a microwave hydrothermal reaction was conducted at 160°C for 30 min; during the microwave hydrothermal reaction, with the rapid transfer of temperature, zeolite with a hierarchically porous MN nanosheet structure was gradually formed around the ZnO/A83PO4/W03 clusters, thereby rapidly encapsulating the ZnO/A83PO4/W03 clusters in pores of the zeolite with a hierarchically porous MFI nanosheet structure (ZSM-5), avoiding self-aggregation of the ZnO/Ag3PO4/W03 clusters; after the reaction, a collected solid product was alternately washed three times with absolute ethanol and deionized water, and then dried at 85°C to obtain the photocatalytic material.

[0070] Example 2

100711 In this example, a preparation method of a photocatalytic material for degrading tetracycline in wastewater included the following steps: 100721 1) Preparation of a substrate with a ZnO seed layer on a surface: [0073] a zinc salt B and ethanolamine were dispersed uniformly in 2-methoxyethanol to form a seed layer solution; a cleaned substrate was immersed into the seed layer solution to prepare a ZnO seed layer on the substrate, to obtain a substrate with the ZnO seed layer on a surface; where [0074] the zinc salt B, the ethanolamine, and the 2-methoxyethanol had a dosage ratio of 0.5 mmol: 1 mmol: 30 ml; and 100751 the zinc salt B was zinc acetate.

[0076] 2) Preparation of a ZnO precursor solution: [0077] according to a dosage ratio of 1 mmol: 1 mmol: 20 ml, a zinc salt A and hexamethylenetetramine were uniformly dispersed in an aqueous solvent, and an obtained mixture was magnetically stirred at 60°C to form a homogeneous ZnO precursor solution; where [0078] the zinc salt A was zinc chloride.

[0079] 3) Preparation of a ZnO nanorod array: 100801 the substrate with the ZnO seed layer on a surface was immersed in the ZnO precursor solution, followed by conducting a hydrothermal reaction at 90°C for 5 h, a product was cooled to a room temperature, filtered, washed with deionized water 3 times, and air-dried naturally to obtain the ZnO nanorod array.

100811 4) Preparation of a suspension B 100821 according to a dosage ratio of 1 mmol: 0.1 g: 20 mL, tungsten trioxide and polyvinylpyrrolidone were uniformly distributed in deionized water by an ultrasonic treatment to obtain a suspension A; and 100831 the ZnO nanorod array was immersed into the suspension A, a silver salt was added, and stirred at 150 r/min for 20 min, a phosphate was added, and stirred at 50 r/min for 30 min to obtain a uniform suspension B; where 100841 the silver salt was silver nitrate; [0085] the phosphate was ammonium dihydrogen phosphate; 100861 the silver salt and the suspension A had a dosage ratio of lOmmol 100 mL and 100871 the silver salt and the phosphate had a molar ratio of 2:1.

100881 5) Microwave hydrothermal synthesis of the photocatalytic material: [0089] aluminum hydroxide, sodium hydroxide, and tetrapropylammonium hydroxide were dispersed evenly in an aqueous solvent, colloidal silica was added and mixed well, and an obtained mixture was subjected to aging at 75°C for 24 h to obtain a molecular sieve synthesis agent; where [0090] the aluminum hydroxide, the sodium hydroxide, the tetrapropylammonium hydroxide, and the aqueous solvent had a dosage ratio of 0.3 mmol: 7 mmol: 1 ml. 1 mL; and [0091] the colloidal silica and the aluminum hydroxide had a mass ratio of 25:1; and [0092] the suspension B was added dropwise to the molecular sieve synthesis agent to conduct an ultrasonic treatment for 10 mm, and a microwave hydrothermal reaction was conducted at 120°C for 120 min to obtain the photocatalytic material.

[0093] Example 3

[0094] In this example, a preparation method of a photocatalytic material for degrading tetracycline in wastewater included the following steps: [0095] 1) Preparation of a substrate with a ZnO seed layer on a surface: [0096] a zinc salt B and ethanolamine were dispersed uniformly in 2-methoxyethanol to form a seed layer solution; a cleaned substrate was immersed into the seed layer solution to prepare a ZnO seed layer on the substrate, to obtain a substrate with the ZnO seed layer on a surface; where [0097] the zinc salt B, the ethanolamine, and the 2-methoxyethanol had a dosage ratio of 2 mmol 1 mmol: 60 ml; and 100981 the zinc salt B was any one selected from the group consisting of zinc nitrate, zinc chloride, zinc sulfate, zinc acetate, zinc citrate, zinc gluconate, and zinc lactate.

[0099] 2) Preparation of a ZnO precursor solution: [0100] according to a dosage ratio of 1 mmol: 1 mmol: 40 ml, a zinc salt A and hexamethylenetetramine were uniformly dispersed in an aqueous solvent, and an obtained mixture was magnetically stirred at 60°C to form a homogeneous ZnO precursor solution; where [0101] the zinc salt A was any one selected from the group consisting of zinc nitrate, zinc chloride, zinc sulfate, zinc acetate, zinc citrate, zinc gluconate, and zinc lactate.

[0102] 3) Preparation of a ZnO nanorod array: [0103] the substrate with the ZnO seed layer on a surface was immersed in the ZnO precursor solution, followed by conducting a hydrothermal reaction at 98°C for 4 h, a product was cooled to a room temperature, filtered, washed with deionized water 3 times, and air-dried naturally to obtain the ZnO nanorod array.

[0104] 4) Preparation of a suspension B [0105] according to a dosage ratio of 1 mmol: 0.1 g: 40 mL, tungsten trioxide and polyvinylpyrrolidone were uniformly distributed in deionized water by an ultrasonic treatment to obtain a suspension A; and [0106] the ZnO nanorod array was immersed into the suspension A, a silver salt was added, and stirred at 250 r/min for 40 min, a phosphate was added, and stirred at 150 r/min for 60 min to obtain a uniform suspension B; where [0107] the silver salt was silver acetate; 101081 the phosphate was sodium phosphate; [0109] the silver salt and the suspension A had a dosage ratio of 20mmol 100 mL and [0110] the silver salt and the phosphate had a molar ratio of 4:1.

[01111 5) Microwave hydrothermal synthesis of the photocatalytic material: [0112] aluminum hydroxide, sodium hydroxide, and tetrapropylammonium hydroxide were dispersed evenly in an aqueous solvent, colloidal silica was added and mixed well, and an obtained mixture was subjected to aging at 95°C for 8 h to obtain a molecular sieve synthesis agent; where [0113] the aluminum hydroxide, the sodium hydroxide, the tetrapropylammonium hydroxide, and the aqueous solvent had a dosage ratio of 0.3 mmol: 8 mmol: 2 ml: L5 mL; and [0114] the colloidal silica and the aluminum hydroxide had a mass ratio of 30:1; and [0115] the suspension B was added dropwise to the molecular sieve synthesis agent to conduct an ultrasonic treatment for 50 min, and a microwave hydrothermal reaction was conducted at 180°C for 10 min to obtain the photocatalytic material.

[0116] Comparative Example 1 [0117] This comparative example differed from Example 1 only in that: [0118] in this comparative example, after the molecular sieve synthesis agent was added dropwise to the suspension B, the microwave hydrothermal reaction was directly conducted without the ultrasonic treatment.

[0119] Comparative Example 2 [0120] This comparative example differed from Example 1 only in that: 101211 In this comparative example, no molecular sieve synthesis agent was added, and the suspension B was directly subjected to the microwave hydrothermal reaction after the ultrasonic treatment.

[0122] It should be noted that, in the above examples of the present disclosure, the substrate was an FTO conductive glass of 50 mmx15 mm 2.2 mm, and a cleaning treatment thereof was as follows: the FTO conductive glass was immersed in anhydrous ethanol to conduct ultrasonic cleaning for 10 min, and then immersed in acetone, and then immersed in deionized water to conduct ultrasonic cleaning for 10 min, and then dried with a hair dryer to obtain a cleaned FTO conductive glass. [0123] It should also be noted that, in the present disclosure, there was no special limitation on specific microwave conditions in the microwave hydrothermal reaction. Optionally, the microwave hydrothermal reaction was conducted at 2.45 GHz and 800 W. [0124] In the present disclosure, the W03 was synthesized by a hydrothermal method: [0125] 0.004 mol of WCI6 was uniformly dispersed in 80 mL of absolute ethanol, a resulting solution was transferred into a 100 mL Teflon-lined autoclave, and then kept at 160°C for 24 h; after cooling to a room temperature, a filter residue was collected by filtration, and washed with distilled water and absolute ethanol for several times in sequence to remove impurities on a surface of the filter residue; the filter residue was dried in an oven at 60°C for 12 h, and a dried product was sintered at 500°C for 1 h to obtain W03 nanoparticles.

[0126] In the present disclosure, the ZnO seed layer was prepared on the substrate by the following steps: [0127] A cleaned substrate was hung on a dip coater at a room temperature, the substrate was immersed in the seed layer solution and allowed to stand for 1 min, and dip coating was conducted at 200 mm/min; a coated substrate was dried in a constant-temperature drying oven at 85°C, and the dip coating was repeated 7 times to form 7 layers of coating on a surface of the substrate; the coated substrate was completely dried, and placed in a muffle furnace to anneal at 350°C for 30 min in an air atmosphere, such that an amorphous coating on the substrate formed a crystalline nano-ZnO seed layer to obtain a substrate with the ZnO seed layer.

[0128] Experimental part [0129] (I) Element distribution test [0130] In order to verify that the photocatalytic material prepared by the present disclosure was indeed a composite, the photocatalytic material of Example I was taken as an example, and an element distribution test was conducted. The results were shown in FIG. 1, and it was seen that elements (Si, 0, Zn, W, and Ag) in the photocatalytic material of Example 1 were uniformly distributed, [0131] (II) Photocatalytic degradation test [0132] In the present disclosure, tetracycline was prepared into a solution of 20 mg/L as wastewater to be treated; the photocatalytic materials of Examples 1 to 3 and Comparative Examples 1 and 2 each were used as a photocatalyst; a 300 W xenon lamp was used as a light source to simulate sunlight exposure conditions.

[0133] The specific test conditions were as follows: [0134] 30 mg of the photocatalytic materials of Examples Ito 3 and Comparative Examples 1 and 2 were separately added to 100 mL of the wastewater to be treated, mixed uniformly, and reacted in the dark for 30 min; after reaching adsorption and desorption equilibrium, a photocatalytic reaction was conducted under irradiation of the 300 W xenon lamp for 60 min; samples were sampled and centrifuged at 10,000 r/min for 10 min, each supernatant was collected and detected on a UV-Vis spectrophotometer to calculate a removal efficiency of tetracycline. The results were shown in FIG. 2. [0135] As was seen from FIG. 2, the degradation effects of Comparative Examples 1 and 2 were much lower than those of Examples 1 to 3, indicating that during the preparation process, the molecular sieve synthesis agent and the ultrasonic treatment after adding the molecular sieve synthesis agent each were critical to synthesis of the photocatalytic material of the present disclosure. This might be related to an effect of the two factors on uniform distribution of the components in the photocatalytic material.

[0136] (III) Stability test of photocatalytic performance 101371 Taking the photocatalytic material of Example 1 as an example, a photocatalytic performance of the photocatalytic material of the present disclosure was tested.

[0138] 30 mg of the photocatalytic material was placed in 100 mL of the wastewater to be treated, and then vigorously stirred for 30 min in the dark to achieve adsorption and desorption equilibrium.

After irradiating with the 300 W xenon lamp for 30 min, 5 mL of a suspension was aspirated for centrifugal separation, and an absorbance was determined using an UV-Vis spectrophotometer. After the photocatalytic experiment was completed, an obtained suspension was recovered by centrifugal separation, and dried for a next round of the photocatalytic experiment, where the experiment was cycled five times. The degradation rates results of five cycles were shown in FIG. 3.

[0139] It was seen from FIG. 3 that a first degradation efficiency was 68.4%, and a fifth degradation efficiency was 62.3%; after five repetitions, the degradation efficiency of the photocatalytic material of the present disclosure was not much lower than that of the first time, indicating that the photocatalytic material had a high stability and reusability.

[0140] Based on the above examples, in the present disclosure, the catalytic material has ZnO/A83PO4/W03 ternary nanoclusters. In the ZnO/Ag31304/W03 ternary nanoclusters, the ECB of W03 (0.61 eV. vs.NHE) is more negative than that of E*(09/H209) (0.68 eV*vs.NHE), such that excited electrons are finally captured by 09 molecules adsorbed on a surface of the ZnO-Ag3PO4-W0.3 nanoclusters to generate H202, and the H202 provides OH by accepting electrons. In addition, considering that the ECB of W03 is more positive than that of E (09/09) (-0.33 eV vs NEE), such that dissolved 09 molecules cannot be directly oxidized into 09-by the excited electrons. On the other hand, since the EVB (2.64 eV vs NHE) of Ag3PO4 is more positive than that of E (OH-/OH) (1.99 eV vs NTIE), such that holes generated in the Ag3PO4 can oxidize H20/0H-to form OH free radicals. Therefore, the photocatalytic material of the present disclosure can help to improve photo-induced charge transfer, inhibit a charge recombination rate, and promote generation of more oxidants (OH and holes), thereby improving a photocatalytic activity.

[0141] Apparently, the above described examples are merely a part rather than all of the examples of the present disclosure. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present disclosure without creative efforts shall fall within the protection scope of the present disclosure.

Claims

WHAT IS CLAIMED IS: 1. A preparation method of a photocatalytic material for degrading tetracycline in wastewater, comprising the following steps: immersing a zinc oxide (ZnO) nanorod array into a suspension A, adding a silver salt, mixing well by stirring, adding a phosphate, and mixing well by stirring to obtain a uniform suspension B; dispersing aluminum hydroxide, sodium hydroxide, and tetrapropylammonium hydroxide evenly in an aqueous solvent, adding colloidal silica and mixing well, and subjecting an obtained mixture to aging at 75°C to 95°C for 8 h to 24 h to obtain a molecular sieve synthesis agent; and adding the molecular sieve synthesis agent to the suspension B to conduct an ultrasonic treatment, and conducting a microwave hydrothermal reaction at 120°C to 180°C for 10 mm to 120 min to obtain the photocatalytic material; wherein the suspension A is prepared from tungsten trioxide, polyvinylpyrrolidone, and the aqueous solvent.
2. The preparation method according to claim 1, wherein the molecular sieve synthesis agent and the suspension B have a volume ratio of 1:(1-3).
3. The preparation method according to claim 1, wherein in the molecular sieve synthesis agent, the aluminum hydroxide, the sodium hydroxide, the tetrapropylammonium hydroxide, and the aqueous solvent have a dosage ratio of 0.3 mmol: (7-8) mmol: (1-2) mL. (1-1 5) mL; and the colloidal silica and the aluminum hydroxide have a mass ratio of (25-30): L
4. The preparation method according to claim 1, wherein in the suspension A, the tungsten trioxide, the polyvinylpyrrolidone, and the aqueous solvent have a dosage ratio of 1 mmol: 0.1 g: (20-40) mL
5. The preparation method according to claim 1, wherein the silver salt is selected from the group consisting of silver acetate and silver nitrate; and the phosphate is selected from the group consisting of sodium phosphate and ammonium dihydrogen phosphate.
6. The preparation method according to claim 1, wherein the silver salt and the suspension A have a dosage ratio of (10-20) mmol: 100 mL; and the silver salt and the phosphate have a molar ratio of (2-4):1.
7. The preparation method according to claim I, wherein the stirring after adding the silver salt is conducted at 150 r/min to 250 r/min for 20 min to 40 min; and the stirring after adding the phosphate is conducted at 50 r/min to 150 r/min for 30 min to 60 min.
8. The preparation method according to claim 1, wherein the ZnO nanorod array is prepared by the following steps: dispersing a zinc salt A and hexamethylenetetramine uniformly in the aqueous solvent to obtain a uniform ZnO precursor solution for later use; dispersing a zinc salt B and ethanolamine uniformly in 2-methoxyethanol to form a seed layer solution; coating the seed layer solution on a substrate to form a ZnO seed layer by a dip-coating method, to obtain a substrate with the ZnO seed laver on a surface; and immersing the substrate with the ZnO seed layer on a surface in the ZnO precursor solution, and conducting a hydrothermal reaction to obtain the ZnO nanorod array; wherein the zinc salt A and the zinc salt B each are any one selected from the group consisting of zinc nitrate, zinc chloride, zinc sulfate, zinc acetate, zinc citrate, zinc gluconate, and zinc lactate.
9. The preparation method according to claim 8, wherein the zinc salt A, the hexamethylenetetramine, and the aqueous solvent have a dosage ratio of 1 mmol: 1 mmol: (20-40) ml; and the zinc salt B, the ethanolamine, and the 2-methoxyethanol have a dosage ratio of (0.5-2) mmol: 1 mmol: (30-60) ml.
10. A photocatalytic material prepared by the preparation method according to any one of claims Ito 9.