A magnetic bismuth tungstate-based nanocomposite, its preparation method and application

Abstract

The present invention relates to a zinc oxide / iron oxide / bismuth tungstate / reduced graphene oxide nanomaterial (ZnO / Fe3O4 / Bi2WO6 / RGO) for the removal of microcystin LR (MC-LR) in water and its preparation method, belonging to the technical field of nanomaterials and their applications. In the present invention, ZnO, Fe3O4, Bi2WO6 and RGO are compounded to prepare a ZnO / Fe3O4 / Bi2WO6 / RGO visible light catalytic material, and the material has magnetism. When the ZnO / Fe3O4 / Bi2WO6 / RGO involved in the present invention is used for the removal of MC-LR, when the initial concentration of MC-LR is 1-7 mg / L, the material dosage is 6 mg, and pH = 7, the removal rate of MC-LR is 55.0%-100% within 180 min. When the initial concentration of MC-LR is 3 mg / L, the material dosage is 200-800 mg / L, and pH = 7, the removal rate of MC-LR is 34.3%-100% within 180 min. When the fulvic acid concentration is 1-5 mg / L, the material dosage is 6 mg, and pH = 7, the removal rate of MC-LR is 65.6%-84.6% within 180 min. When the algal cell density is 1×10 6 -5×10 6 cells / mL, the material dosage is 6 mg, and pH = 7, the removal rate of MC-LR is 62.2%-90.2% within 180 min. ZnO / Fe3O4 / Bi2WO6 / RGO can efficiently degrade MC-LR in water under visible light irradiation, and can be recovered by a magnet after the degradation is completed.

Description

Technical Field

[0001] The present invention belongs to the technical field of nanomaterials and their applications, and particularly relates to a preparation method and application of a zinc oxide / iron oxide / bismuth tungstate / reduced graphene oxide composite material Background Art

[0002] The increasingly severe eutrophication of water bodies has led to frequent outbreaks of cyanobacteria blooms. As the most common cyanobacteria, Microcystis aeruginosa releases algal toxins during blooms (Tian Huijie, Han Bangzhong. Research on the monitoring technology of microcystin in reservoirs [J]. China Resources Comprehensive Utilization, 2021, 39(2): 122-124.). Among them, the most common, abundant and toxic algal toxin is microcystin (MCs). The presence of MCs has a serious impact on human health and is also a major hidden danger in drinking water (Yao Hangyong, Xia Liangliang, Min Hao. Photocatalytic degradation of microcystin LR [J]. Environmental Protection Science and Technology, 2011, 17(2): 5-9.). 2

[0003] Photocatalytic technology has the advantages of being green, environmentally friendly, low-cost, safe and pollution-free. In recent years, a large number of studies have used bismuth tungstate (Bi 2 WO 6 ) as a photocatalyst to degrade organic pollutants in water bodies. It has the advantages of high activity, easy availability and environmental friendliness. However, Bi 2 WO 6 has problems such as a narrow visible light absorption range and a high recombination rate of photogenerated carriers, which limits the application and popularization of Bi 2 WO 6 in the removal of microcystin. In addition, powdered Bi 2 WO 6 has the problem of being difficult to recover in actual water bodies, and the nanomaterials exposed to the water environment will harm aquatic animals and humans. By combining bismuth tungstate with zinc oxide, iron oxide and reduced graphene oxide, not only can the separation of photogenerated electrons and holes of bismuth tungstate be promoted, but also the utilization efficiency of visible light can be improved. In addition, after degrading microcystin, the zinc oxide / iron oxide / bismuth tungstate / reduced graphene oxide composite material can be separated from the aqueous solution by an external magnetic field

[0004] Therefore, the present invention proposes a preparation method and application of a magnetically recyclable zinc oxide / iron oxide / bismuth tungstate / reduced graphene oxide composite material Summary of the Invention

[0005] The object of the present invention is to provide a zinc oxide / iron oxide / bismuth tungstate / reduced graphene oxide composite material

[0006] ​The second object of the present invention is to provide a preparation method of zinc oxide / iron oxide / biotungstate / reduced graphene oxide composite material for the degradation of microcystin LR.

[0007] The third object of the present invention is to provide the application of the magnetic nano-composite photocatalytic material in removing microcystin LR.

[0008] A zinc oxide / iron oxide / biotungstate / reduced graphene oxide composite material, which is composed of reduced graphene oxide, biotungstate, iron oxide and zinc oxide.

[0009] The zinc oxide / iron oxide / biotungstate / reduced graphene oxide composite material (hereinafter referred to as this material) described in the present invention has magnetism and can still maintain a high removal efficiency in actual water bodies.

[0010] The preparation method of the zinc oxide / iron oxide / biotungstate / reduced graphene oxide composite material described in the present invention includes the following steps:

[0011] 1) Graphene oxide is prepared by using the improved Hummers method, and then a graphene oxide dispersion is obtained by ultrasonic dispersion.

[0012] 2) FeCl 3 ·6H 2 O and CH 3 COONa are added to 40 mL of ethylene glycol and stirred evenly, and then a solvothermal method is used to react at 200 °C for 6 h to obtain Fe 3 O 4 nanoparticles. The Fe 3 O 4 nanoparticles are treated in 1 M HNO 3 aqueous solution to protonate the surface of Fe 3 O 4 .

[0013] 3) The protonated Fe 3 O 4 , Bi(NO 3 ) 3 ·5H 2 O and Na 2 WO 4 ·2H 2 O are added to the graphene oxide dispersion and stirred evenly, and a hydrothermal method is used to prepare iron oxide / biotungstate / reduced graphene oxide (Fe 3 O 4 / Bi 2 WO 6 / RGO).

[0014] 4) Fe 3 O4 / Bi 2 WO 6 After the / RGO was uniformly dispersed in deionized water, ZnCl was added 2 , and then NaOH was dissolved in deionized water. Under a certain temperature and magnetic stirring, the NaOH solution was added dropwise to the mixture containing Fe 3 O 4 / Bi 2 WO 6 / RGO and ZnCl 2 . After the reaction, zinc oxide / iron oxide / tungstic acid bismuth / reduced graphene oxide (ZnO / Fe 3 O 4 / Bi 2 WO 6 / RGO) can be obtained.

[0015] In the solution of the present invention, step 1 is specifically as follows: 1 g of graphite powder is added to 23 mL of concentrated sulfuric acid and stirred for 12 - 24 h, and then 0.5 g of NaNO is added 3 and stirring is continued for 3 h. 3 g of KMnO is slowly added while keeping the temperature of the reaction system not higher than 10 °C 4 . The temperature is raised to 35 °C and maintained for 30 min, and then the temperature is further raised to 38 °C and maintained for 2 h. 46 mL of deionized water is slowly added, and after 15 min, 140 mL of deionized water and 10 mL of 30% H 2 O 2 solution are added. After standing for 4 h to obtain a solid product, it is repeatedly washed 4 - 8 times with 5% HCl solution and deionized water until there is no residual sulfate ion and chloride ion, and the product is stored by freeze-drying. By means of ultrasonic wave, graphene oxide is uniformly dispersed in water, and the power of ultrasonic wave is 80 W and the ultrasonic time is 20 min, wherein the ratio of graphene oxide to water is 2 mg:1 mL.

[0016] In the solution of the present invention, step 2 is specifically as follows: FeCl 3 ·6H 2 O and CH 3 COONa are added to ethylene glycol according to a molar ratio of 1:17.6, and stirred at 800 rpm / min for 1 - 3 h under magnetic stirring. Subsequently, the mixture of FeCl 3 ·6H 2 O and CH 3 COONa is transferred to a 100 mL high-pressure reaction kettle with a polytetrafluoroethylene inner liner. The reaction kettle is placed in a hydrothermal reaction at 180 - 220 °C for 4 - 8 h., and naturally cooled to room temperature. The product is filtered by suction, and then washed 3 - 6 times with absolute ethanol and deionized water respectively, and dried in an oven at 60 °C. By means of ultrasonic wave in 1 M HNO3 In an aqueous solution, the surface of Fe 3 O 4 is protonated, the ultrasonic power is 80 - 120 W, and the ultrasonic time is 40 - 80 min.

[0017] In the solution of the present invention, step 3 is specifically: adding the surface - protonated Fe 3 O 4 , Bi(NO 3 ) 3 ·5H 2 O and Na 2 WO 4 ·2H 2 O into the graphene oxide dispersion liquid and stirring at 500 rpm / min for 3 - 5 h under magnetic stirring. Among them, the molar mass of the added protonated Fe 3 O 4 is 0.30 - 0.75 mmol, and the molar ratio of Bi(NO 3 ) 3 .5H 2 O to Na 2 WO 4 .2H 2 O is 2:1. Subsequently, transfer the mixture of the surface - protonated Fe 3 O 4 , Bi(NO 3 ) 3 ·5H 2 O, Na 2 WO 4 ·2H 2 O and graphene oxide mixed liquid to a 100 - mL autoclave with a polytetrafluoroethylene liner, place the autoclave in a hydrothermal reaction at 160 - 200 °C for 12 - 20 h, and then naturally cool to room temperature. Filter the product by suction, and then wash it 3 - 6 times with anhydrous ethanol and deionized water respectively, and dry it in an oven at 60 °C to obtain Fe 3 O 4 / Bi 2 WO 6 / RGO.

[0018] In the solution of the present invention, step 4 is specifically: after dispersing 0.46 - 1.84 g of Fe 3 O 4 / Bi 2 WO 6 / RGO evenly in 15 mL of deionized water, add ZnCl 2 , and then dissolve NaOH in deionized water, where the molar ratio of ZnCl 2 to NaOH is 1:2. Control the temperature at 50 - 70 °C, and add the NaOH solution dropwise to the solution containing Fe3 O 4 / Bi 2 WO 6 / RGO and ZnCl 2 In the mixed solution of, stir at 500 rpm / min for 10 - 50 min under magnetic stirring to obtain zinc oxide / iron oxide / zirconium tungstate / bismuth tungstate / reduced graphene oxide (ZnO / Fe 3 O 4 / Bi 2 WO 6 / RGO).

[0019] When the initial concentration of microcystin LR is 1 - 7 mg / L, the dosage of the zinc oxide / iron oxide / zirconium tungstate / bismuth tungstate / reduced graphene oxide composite material described in the present invention is 6 mg, and when the pH value is 7, the removal efficiency of microcystin LR is 55.0% - 100% in 180 min.

[0020] When the initial concentration of microcystin is 3 mg / L, the dosage of the zinc oxide / iron oxide / zirconium tungstate / bismuth tungstate / reduced graphene oxide composite material described in the present invention is 200 - 800 mg / L, and when the pH value is 7, the removal efficiency of microcystin LR is 34.3% - 100% in 180 min.

[0021] When the concentration of fulvic acid is 1 - 5 mg / L, the dosage of the zinc oxide / iron oxide / zirconium tungstate / bismuth tungstate / reduced graphene oxide composite material described in the present invention is 6 mg, and when the pH value is 7, the removal efficiency of microcystin LR is 65.6% - 84.6% in 180 min.

[0022] When the density of algal cells is 1×10 6 -5×10 6 cells / mL, the dosage of the zinc oxide / iron oxide / zirconium tungstate / bismuth tungstate / reduced graphene oxide composite material described in the present invention is 6 mg, and when the pH value is 7, the removal efficiency of microcystin LR is 62.2% - 90.2% in 180 min.

[0023] Zinc oxide / iron oxide / zirconium tungstate / bismuth tungstate / reduced graphene oxide can efficiently degrade microcystin LR in water under visible light irradiation. After the degradation is completed, it can be separated by a magnet, and then recycled after washing and drying. Description of the Drawings

[0024] Figure 1 ZnO / Fe prepared under the condition that the reaction system temperature is 60 °C in Example 1 3 O 4 / Bi 2 WO 6XRD pattern of ZnO / Fe

[0025] Figure 2 O / Bi 3 O 4 / Bi 2 WO 6 / RGO composite photocatalytic material's hysteresis loop diagram.

[0026] Figure 3 For the ZnO / Fe 3 O 4 / Bi 2 WO 6 / RGO composite photocatalytic material prepared in Example 1 under the conditions that the reaction system temperature is 60 °C, the initial microcystin-LR concentration is set to 1 / 3 / 5 / 7 mg / L, the solution volume is 10 mL, and the pH value is 7.0 ± 0.2, the removal efficiency diagram of the microcystin-LR solution.

[0027] Figure 4 For the ZnO / Fe 3 O 4 / Bi 2 WO 6 / RGO composite photocatalytic material prepared in Example 1 under the conditions that the reaction system temperature is 60 °C, the initial microcystin-LR concentration is set to 3 mg / L, the solution volume is 10 mL, the pH value is 7.0 ± 0.2, and the mass of the material added is set to 2 / 4 / 6 / 8 mg, the removal efficiency diagram of the microcystin-LR solution.

[0028] Figure 5 For the ZnO / Fe 3 O 4 / Bi 2 WO 6 / RGO composite photocatalytic material prepared in Example 1 under the conditions that the reaction system temperature is 60 °C, the initial microcystin-LR concentration is set to 3 mg / L, the solution volume is 10 mL, the pH value is 7.0 ± 0.2, and the concentration of humic acid fulvic acid (FA) is set to 1 / 3 / 5 mg / L, the removal efficiency diagram of the microcystin-LR solution.

[0029] Figure 6 For the ZnO / Fe 6 prepared in Example 1 under the conditions that the reaction system temperature is 60 °C, the initial microcystin-LR concentration is set to 3 mg / L, the solution volume is 10 mL, the pH value is 7.0 ± 0.2, and the concentration of algal cells is set to 1 / 3 / 5×10 3 O 4 / Bi 2 WO 6 Removal efficiency diagram of microcystin-LR solution by / RGO. Detailed implementation mode

[0030] The present invention is further described in detail through the following embodiments, so that the methods, steps, and advantages of the present invention are clearer. However, the present invention is not limited to the following embodiments. Without departing from the essence of the present invention, any modification or replacement of the methods, steps, or conditions of the present invention belongs to the scope of protection of the present invention.

[0031] Example 1

[0032] Add 1 g of graphite powder to 23 mL of concentrated sulfuric acid and stir for 12 - 24 h, then add 0.5 g of NaNO 3 Continue to stir for 3 h. Slowly add 3 g of KMnO while maintaining the temperature of the reaction system not higher than 10 °C 4 . Heat to 35 °C and maintain for 30 min, then continue to heat to 38 °C and maintain for 2 h. Slowly add 46 mL of deionized water, and after 15 min, continue to add 140 mL of deionized water and 10 mL of 30% H 2 O 2 solution. Let it stand for 4 h to obtain a solid product, and then wash it 4 - 8 times repeatedly with 5% HCl solution and deionized water until there is no residual sulfate ion and chloride ion. The product is stored after freeze-drying. By ultrasonic means, graphene oxide is evenly dispersed in water, and the ultrasonic power is 80 W and the ultrasonic time is 20 min to obtain a graphene oxide dispersion.

[0033] Add FeCl 3 ·6H 2 O and CH 3 COONa into ethylene glycol in a molar ratio of 1:17.6, stir at 800 rpm / min for 2 h under magnetic stirring, and then transfer the mixture of FeCl 3 ·6H 2 O and CH 3 COONa to a 100 mL high-pressure reaction kettle with a polytetrafluoroethylene liner. Place the reaction kettle in water at 200 °C for hydrothermal reaction for 6 h., and then cool it naturally to room temperature. Filter the product by suction, and then wash it 3 - 6 times with absolute ethanol and deionized water respectively, and dry it in an oven at 60 °C. By ultrasonic means, protonate the surface of Fe 3 in an aqueous solution of 1 M HNO 3 O 4 , and the ultrasonic power is 100 W and the ultrasonic time is 60 min.

[0034] Protonate the surface of Fe 3 O 4, Bi(NO 3 ) 3 ·5H 2 O and Na 2 WO 4 ·2H 2 O were added to the graphene oxide dispersion and stirred at 500 rpm / min for 4 h under magnetic stirring. Among them, the molar mass of protonated Fe 3 O 4 was 0.60 mmol, and the molar ratio of Bi(NO 3 ) 3 .5H 2 O to Na 2 WO 4 .2H 2 O was 2:1. Subsequently, the surface-protonated Fe 3 O 4 , Bi(NO 3 ) 3 ·5H 2 O, Na 2 WO 4 ·2H 2 O and the graphene oxide mixture were transferred to a 100 mL autoclave with a polytetrafluoroethylene liner. The autoclave was placed in a hydrothermal reaction at 180 °C for 16 h and then naturally cooled to room temperature. The product was filtered by suction, and then washed 3 - 6 times with absolute ethanol and deionized water, and dried in an oven at 60 °C to obtain.

[0035] 0.92 g of Fe 3 O 4 / Bi 2 WO 6 / RGO was dispersed evenly in 15 mL of deionized water, and then ZnCl 2 was added. Subsequently, NaOH was dissolved in deionized water, and the molar ratio of ZnCl 2 to NaOH was 1:2. The temperature was controlled at 60 °C, and the NaOH solution was added dropwise to the mixture containing Fe 3 O 4 / Bi 2 WO 6 / RGO and ZnCl 2 . Stir at 500 rpm / min for 30 min under magnetic stirring to obtain zinc oxide / iron oxide / bismuth tungstate / reduced graphene oxide (ZnO / Fe 3 O 4 / Bi 2 WO 6 / RGO).

[0036] As Figure 1 shown, the ZnO / Fe prepared above3 O 4 / Bi 2 WO 6 / RGO composite photocatalytic material and Bi 2 WO 6 's standard card (JCPDS No.73 - 2020), Fe 3 O 4 's standard card (JCPDS No.19 - 0629) and ZnO's standard card (JCPDS No.36 - 1451) match and there are no impurity peaks. Since the content of RGO in the ZnO / Fe 3 O 4 / Bi 2 WO 6 / RGO nanocomposite is low, no characteristic peaks of RGO are found.

[0037] As Figure 2 shown, the prepared ZnO / Fe 3 O 4 / Bi 2 WO 6 / RGO composite photocatalytic material has magnetism, with a saturation magnetization intensity of 16.3 emu / g and a coercivity of 74.6 Oe.

[0038] Example 2

[0039] Add 1 g of graphite powder to 23 mL of concentrated sulfuric acid and stir for 12 - 24 h, then add 0.5 g of NaNO 3 Continue to stir for 3 h. Slowly add 3 g of KMnO 4 while keeping the temperature of the reaction system not higher than 10 °C. 2 O 2 Raise the temperature to 35 °C and keep it for 30 min, then continue to raise the temperature to 38 °C and keep it for 2 h. Slowly add 46 mL of deionized water, and after 15 min, continue to add 140 mL of deionized water and 10 mL of 30% H

[0040] Add FeCl 3 ·6H 2 O and CH 3 COONa into ethylene glycol in a molar ratio of 1:17.6, stir at 800 rpm / min for 2 h under magnetic stirring, and then add FeCl 3 ·6H 2 O and CH3 The mixed solution of COONa was transferred to a 100 mL high-pressure reactor with a polytetrafluoroethylene liner. The reactor was placed in hydrothermal reaction at 200 °C for 6 h, and then naturally cooled to room temperature. The product was filtered by suction, and then washed 3 - 6 times with absolute ethanol and deionized water respectively, and dried in an oven at 60 °C. The surface of Fe 3 was protonated in an aqueous solution of 1 M HNO 3 O 4 with a ultrasonic power of 100 W and a ultrasonic time of 60 min.

[0041] The surface-protonated Fe 3 O 4 , Bi(NO 3 ) 3 ·5H 2 O and Na 2 WO 4 ·2H 2 O were added into the graphene oxide dispersion and stirred at 500 rpm / min for 4 h under magnetic stirring. The molar mass of the added protonated Fe 3 O 4 was 0.60 mmol, and the molar ratio of Bi(NO 3 ) 3 .5H 2 O to Na 2 WO 4 .2H 2 O was 2:1. Subsequently, the surface-protonated Fe 3 O 4 , Bi(NO 3 ) 3 ·5H 2 O, Na 2 WO 4 ·2H 2 O and the graphene oxide mixed solution were transferred to a 100 mL high-pressure reactor with a polytetrafluoroethylene liner. The reactor was placed in hydrothermal reaction at 180 °C for 16 h, and then naturally cooled to room temperature. The product was filtered by suction, and then washed 3 - 6 times with absolute ethanol and deionized water respectively, and dried in an oven at 60 °C to obtain Fe 3 O 4 / Bi 2 WO 6 / RGO.

[0042] After dispersing 0.92 g of Fe 3 O 4 / Bi 2 WO 6 / RGO evenly in 15 mL of deionized water, ZnCl 2, Subsequently, NaOH was dissolved in deionized water, where the molar ratio of ZnCl 2 to NaOH was 1:2. The temperature was controlled at 50 °C, and the NaOH solution was added dropwise to the mixture containing Fe 3 O 4 / Bi 2 WO 6 / RGO and ZnCl 2 . Stir at 500 rpm / min for 30 min under magnetic stirring to obtain zinc oxide / iron oxide / bismuth tungstate / reduced graphene oxide (ZnO / Fe 3 O 4 / Bi 2 WO 6 / RGO).

[0043] Example 3

[0044] 1 g of graphite powder was added to 23 mL of concentrated sulfuric acid and stirred for 12 - 24 h, then 0.5 g of NaNO 3 was added and stirring was continued for 3 h. 3 g of KMnO 4 was slowly added while maintaining the temperature of the reaction system not higher than 10 °C. The temperature was raised to 35 °C and maintained for 30 min, and then continued to be raised to 38 °C and maintained for 2 h. 46 mL of deionized water was slowly added, and after 15 min, 140 mL of deionized water and 10 mL of 30% H 2 O 2 solution were added. After standing for 4 h to obtain a solid product, it was washed repeatedly with 5% HCl solution and deionized water for 4 - 8 times until there was no residual sulfate ion and chloride ion, and the product was stored by freeze-drying. By ultrasonic method, graphene oxide was evenly dispersed in water, and the ultrasonic power was 80 W and the ultrasonic time was 20 min to obtain a graphene oxide dispersion.

[0045] FeCl 3 ·6H 2 O and CH 3 COONa were added to ethylene glycol in a molar ratio of 1:17.6 and stirred at 800 rpm / min for 2 h under magnetic stirring. Subsequently, the mixture of FeCl 3 ·6H 2 O and CH 3 COONa was transferred to a 100 mL autoclave with a polytetrafluoroethylene liner. The autoclave was placed in water at 200 °C for hydrothermal reaction for 6 h, and then naturally cooled to room temperature. The product was filtered by suction, and then washed 3 - 6 times with anhydrous ethanol and deionized water respectively, and dried in an oven at 60 °C. By ultrasonic method, Fe 3 was in 1 M HNO 3 aqueous solution of O 4Surface protonation was carried out with the ultrasonic power of 100 W and the ultrasonic time of 60 min.

[0046] Add the surface-protonated Fe 3 O 4 , Bi(NO 3 ) 3 ·5H 2 O and Na 2 WO 4 ·2H 2 O into the graphene oxide dispersion and stir at 500 rpm / min for 4 h under magnetic stirring. The molar mass of the added protonated Fe 3 O 4 is 0.60 mmol, and the molar ratio of Bi(NO 3 ) 3 .5H 2 O to Na 2 WO 4 .2H 2 O is 2:1. Subsequently, transfer the mixture of surface-protonated Fe 3 O 4 , Bi(NO 3 ) 3 ·5H 2 O, Na 2 WO 4 ·2H 2 O and graphene oxide to a 100 mL autoclave with a polytetrafluoroethylene liner, place the autoclave in an oven at 180 °C for hydrothermal reaction for 16 h, and then cool it naturally to room temperature. Filter the product by suction, and then wash it 3 - 6 times with anhydrous ethanol and deionized water respectively, and dry it in an oven at 60 °C to obtain Fe 3 O 4 / Bi 2 WO 6 / RGO.

[0047] Disperse 0.92 g of Fe 3 O 4 / Bi 2 WO 6 / RGO evenly in 15 mL of deionized water, then add ZnCl 2 . Subsequently, dissolve NaOH in deionized water, and the molar ratio of ZnCl 2 to NaOH is 1:2. Control the temperature at 70 °C, and add the NaOH solution dropwise to the mixture containing Fe 3 O 4 / Bi 2 WO 6 / RGO and ZnCl 2In the mixed solution, stir at 500 rpm / min for 30 min under magnetic stirring to obtain zinc oxide / iron oxide / bismuth tungstate / reduced graphene oxide (ZnO / Fe 3 O 4 / Bi 2 WO 6 / RGO).

[0048] Example 4

[0049] Add 6 mg of ZnO / Fe 3 O 4 / Bi 2 WO 6 / RGO prepared at 60 °C into a 10 mL solution of microcystin LR. The microcystin solution was prepared with deionized water, and the initial microcystin concentration was set at 1 / 3 / 5 / 7 mg / L. The pH of the algal solution was adjusted to 7.0 with 0.5 M HCl and 0.5 M NaOH. The temperature of the reaction system was controlled at 25 ± 0.2 °C. Before turning on the xenon lamp, first allow the composite material to undergo a dark reaction for 1 h to reach adsorption saturation, and then turn on the xenon lamp. Take a solution every 20 min, and use high performance liquid chromatography to test the concentration of microcystin LR.

[0050] As Figure 3 shown, the degradation efficiency of ZnO / Fe 3 O 4 / Bi 2 WO 6 / RGO for microcystin LR decreases with the increase in the concentration of microcystin.

[0051] As Figure 3 shown, when the initial concentration of microcystin LR is 1 - 7 mg / L, the removal efficiency of microcystin LR is 55.0% - 100% in 180 min.

[0052] Example 5

[0053] Add 2 / 4 / 6 / 8 mg of ZnO / Fe 3 O 4 / Bi 2 WO 6 / RGO prepared at 60 °C into a 10 mL solution of microcystin LR. The microcystin solution was prepared with deionized water, and the initial microcystin concentration was set at 3 mg / L. The pH of the algal solution was adjusted to 7.0 with 0.5 M HCl and 0.5 M NaOH. The temperature of the reaction system was controlled at 25 ± 0.2 °C. Before turning on the xenon lamp, first allow the composite material to undergo a dark reaction for 1 h to reach adsorption saturation, and then turn on the xenon lamp. Take a solution every 20 min, and use high performance liquid chromatography to test the concentration of microcystin LR.

[0054] As Figure 4 shown, the degradation efficiency of microcystin-LR by ZnO / Fe 3 O 4 / Bi 2 WO 6 / RGO prepared at 60 °C increases with the increase of the dosage of the material.

[0055] As Figure 4 shown, at the dosage of 200 - 800 mg / L, the removal efficiency of microcystin-LR within 180 min is 34.3% - 100%.

[0056] Example 6

[0057] 6 mg of ZnO / Fe 3 O 4 / Bi 2 WO 6 / RGO prepared at 60 °C was added to 10 mL of a solution of microcystin-LR with an initial concentration of 3 mg / L. The microcystin solution was prepared with deionized water, and the concentration of humic acid fulvic acid (FA) was set at 1 / 3 / 5 mg / L. The pH of the algal solution was adjusted to 7 with 0.5 M HCl and 0.5 M NaOH respectively. The temperature of the reaction system was controlled at 25 ± 0.2 °C. Before turning on the xenon lamp, the composite material was first allowed to react in the dark for 1 h to reach adsorption saturation. Then the xenon lamp was turned on, and the solution was taken every 20 min. The concentration of microcystin-LR was measured by high performance liquid chromatography.

[0058] As Figure 5 shown, the degradation efficiency of microcystin-LR by ZnO / Fe 3 O 4 / Bi 2 WO 6 / RGO prepared at 60 °C decreases with the increase of the fulvic acid concentration.

[0059] As Figure 5 shown, when the concentration of fulvic acid is 1 - 5 mg / L, the removal efficiency of microcystin-LR within 180 min is 65.6% - 84.6%.

[0060] Example 7

[0061] 6 mg of ZnO / Fe 3 O 4 / Bi 2 WO 6 / RGO prepared at 60 °C was added to 10 mL of a solution of microcystin-LR with an initial concentration of 3 mg / L. The microcystin solution was prepared with deionized water, and the concentration of algal cells was set at 1 / 3 / 5×10 6When the concentration is 1×10 6 -5×10 6 cells / mL, the pH of the microcystin-LR solution is adjusted to 7 with 0.5 M HCl and 0.5 M NaOH, and the temperature of the reaction system is controlled at 25±0.2 °C. Before turning on the xenon lamp, the composite material is first subjected to a dark reaction for 1 h to reach adsorption saturation, and then the xenon lamp is turned on. A solution sample is taken every 20 min, and the concentration of microcystin-LR is measured using high performance liquid chromatography.

[0062] As Figure 6 shown, the degradation efficiency of ZnO / Fe 3 O 4 / Bi 2 WO 6 / RGO for microcystin-LR decreases with the increase of algal cell density.

[0063] As Figure 6 shown, when the algal cell density is 1×10 6 -5×10 6 cells / mL, the removal efficiency of microcystin-LR is 62.2%-90.2% within 180 min.

Claims

1. A zinc oxide / iron oxide / biobismuth tungstate / reduced graphene oxide composite material, Characterized in that, The composite material has magnetism; The preparation method of the zinc oxide / iron oxide / biobismuth tungstate / reduced graphene oxide composite material comprises the following steps: 1) Prepare graphene oxide by using the improved Hummers method, and then obtain a graphene oxide dispersion by ultrasonic dispersion; 2) Add FeCl 3 ·6H 2 O and CH 3 COONa to 40 mL of ethylene glycol, stir evenly, and then react at 200 °C for 6 h using the solvothermal method to obtain Fe 3 O 4 nanoparticles; Treat the Fe 3 O 4 nanoparticles in 1 M HNO 3 aqueous solution to protonate the surface of Fe 3 O 4 ; 3) Add protonated Fe 3 O 4 , Bi(NO 3 ) 3 ·5H 2 O and Na 2 WO 4 ·2H 2 O to the graphene oxide dispersion and stir evenly. Prepare Fe 3 O 4 / Bi 2 WO 6 / RGO by hydrothermal method; 4) Add Fe 3 O 4 / Bi 2 WO 6 / RGO into deionized water and disperse it evenly. Then add ZnCl 2 . Subsequently, dissolve NaOH in deionized water. Under a certain temperature and with magnetic stirring, gradually add the NaOH solution dropwise to the mixture containing Fe 3 O 4 / Bi 2 WO 6 / RGO and ZnCl 2 . After the reaction, zinc oxide / iron oxide / tungstic acid bismuth / reduced graphene oxide ZnO / Fe 3 O 4 / Bi 2 WO 6 / RGO can be obtained; The Fe described in step 4) 3 O 4 / Bi 2 WO 6 / RGO is added in an amount of 0.46 - 1.84 g, and the volume of deionized water is 15 mL; the molar ratio of ZnCl 2 to NaOH is 1:2; the temperature is controlled at 50 - 70 °C; the magnetic stirring is carried out at 500 rpm for 10 - 50 min.

2. The composite material according to claim 1, Characterized in that, By ultrasonic means, graphene oxide is uniformly dispersed in water, and the ultrasonic power is 60-100 W, and the ultrasonic time is 10-30 min.

3. The composite material according to claim 1, Characterized in that, Mix FeCl 3 ·6H 2 O and CH 3 COONa and stir at 800 rpm for 1 - 3 h under magnetic stirring.

4. The composite material according to claim 1, Characterized in that, Protonate the surface of Fe 3 O 4 by ultrasound, with the ultrasound power being 80 - 120 W and the ultrasound time being 40 - 80 min.

5. The composite material according to claim 1, Characterized in that, Protonated Fe 3 O 4 、Bi(NO 3 ) 3 ·5H 2 O and Na 2 WO 4 ·2H 2 O were added to the graphene oxide dispersion, and stirred at 500 rpm for 3 - 5 h under magnetic stirring.

6. The composite material according to claim 1, Characterized in that, Hydrothermal reaction is carried out at a temperature of 160-200 °C for 12-20 h.

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