Floating type composite photocatalytic material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of photocatalytic water treatment, and discloses a floating type composite photocatalytic material as well as a preparation method and application thereof. The preparation method comprises the following steps: with biological regenerated diatomite as a raw material, carrying out hydrophobic modification with a silane coupling agent to obtain hydrophobic modified diatomite; compounding the hydrophobic modified diatomite with the bonding liquid and the coating liquid to obtain a floating carrier; mixing the photocatalyst powder with a polyvinyl alcohol solution to form a mixed solution; dipping a floating carrier in the mixed solution, and heating and curing to stably load the photocatalyst on the hydrophobic floating carrier, thereby obtaining the amphiphilic floating type composite photocatalytic material. The preparation method is simple in process operation, the adopted raw materials are easy to obtain and low in cost, the direct combination effect of the photocatalyst component and the carrier in the floating type composite photocatalytic material is good, limitation of the color and turbidity of a water body is avoided, the photocatalytic performance of the floating type composite photocatalytic material can be effectively improved, and the application prospect is wide. The removal effect on the organic pollutants to be removed is greatly improved.

Description

Technical Field

[0001] The invention relates to the technical field of photocatalytic water treatment, and in particular to a floating composite photocatalytic material and a preparation method and application thereof. Background Art

[0002] Urban sewage treatment plants are considered to be the main source of organic pollutants in receiving rivers. Although conventional sewage biological treatment processes have a significant removal effect on conventional pollutants such as nitrogen and phosphorus, PAHs and PAH derivatives are difficult to degrade, easy to accumulate, and have obvious "three-hazard" effects, which makes it difficult for conventional sewage biological treatment processes to effectively remove PAHs and PAH derivatives. Among them, the full name of PAHs in English is Polycyclic Aromatic Hydrocarbon, referred to as PAHs, and the full name of PAH derivatives in English is Substituted Polycyclic Aromatic Hydrocarbon, referred to as SPAHs. Moreover, PAHs and SPAHs also have high toxic effects and bioaccumulation, which make them a potential environmental risk even at low concentrations. Therefore, the enhanced removal of PAHs and SPAHs in the effluent of sewage treatment plants is of practical significance.

[0003] At present, among the technologies for removing PAHs pollutants in water environments, photocatalytic oxidation technology has become one of the most promising technologies for controlling PAHs pollutants due to its low selectivity for pollutants in the process of removing water pollution, and its advantages such as environmental protection, stability, and recyclable high-efficiency photocatalysts. In addition, photocatalytic oxidation technology with semiconductor catalytic materials as the core has obvious advantages in treating difficult-to-degrade and highly toxic organic wastewater.

[0004] BiOBr is an indirect bandgap semiconductor. Its unique electronic structure, stable chemical properties and excellent visible light absorption ability make it widely used in the field of visible light catalytic degradation. However, its utilization rate of visible light is significantly lower than that of TiO 2 Moreover, BiOBr is usually in powder form, the catalyst particles are fine and tend to agglomerate after being added into a water environment, and it is difficult to separate and recover it from the reaction solution after use, which also limits its application scope to a certain extent.

[0005] In order to solve the above technical problems, those skilled in the art have proposed to load the catalyst onto a carrier material so as to realize the recycling of the catalyst material. At present, the existing technology mainly uses spraying and coating methods when compounding photocatalysts and carrier materials, but the above methods all have the problems of cumbersome and complicated preparation steps and high cost, and the bonding effect between the photocatalyst and the carrier in the formed composite material is poor, resulting in the photocatalyst easily falling off from the surface of the photocatalytic device carrier during use. In addition, the surface of the sewage to be treated often has poor transparency, resulting in the above composite material being limited by the color and turbidity of the water body, which greatly affects the photocatalytic performance of the composite material, and thus greatly limits the removal of organic pollutants in the water environment. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a floating composite photocatalytic material and a preparation method and application thereof.

[0007] The floating composite photocatalytic material and its preparation method and application of the present invention are realized by the following technical solutions: The first object of the present invention is to provide a method for preparing a floating composite photocatalytic material, comprising the following steps: Step 1, hydrophobic modification of bioregenerated diatomaceous earth: The bioregenerated diatomite obtained by bioregeneration technology is used as a raw material, and a silane coupling agent is used as a hydrophobic modifier to perform hydrophobic modification on the surface of the bioregenerated diatomite to obtain hydrophobically modified diatomite.

[0008] Step 2, surface hydrophilization treatment: The hydrophobically modified diatomaceous earth is mixed with a binding liquid to form a blank; the blank is pressed into sheets and dried to obtain a sheet-like blank; a layer of the coating liquid is coated on the surface of the sheet-like blank and then dried, so that a layer of polyvinyl alcohol is formed on the surface of the sheet-like blank after the coating liquid is solidified to obtain a floating carrier.

[0009] Step 3, loading the photocatalyst on the floating carrier: The photocatalyst powder is dispersed in a polyvinyl alcohol solution to obtain a mixed solution; the floating carrier is immersed in the mixed solution, and then immersed and dried at 55°C to 60°C to allow the mixed solution to form a solidified film on the carrier surface, thereby achieving stable loading of the photocatalyst on the floating carrier to obtain a floating composite photocatalytic material.

[0010] In step 1, it should be noted that the present invention takes into account the use of waste diatomaceous earth produced in the beer filtration process and discarded due to pore blockage and reduced adsorption capacity as raw material, which can not only realize the resource recycling of waste diatomaceous earth and alleviate environmental pressure, but also the present invention uses biological regeneration technology to deproteinize the waste diatomaceous earth, which can restore and release the pore structure and surface structure of the waste diatomaceous earth, thereby allowing the treated diatomaceous earth to regain the ability to adsorb pollutants through its unique porous structure.

[0011] It should also be noted that the biological deproteinization treatment technology used in the present invention is referenced to DOI number 10.1016 / j.jbiosc.2018.08.004 and entitled “Highly efficient deproteinization with anammonifying bacteria Lysinibacillus fusiformis The process is carried out under the optimal conditions of biological deproteinization treatment in the prior art of "isolated from brewery spent diatomite", so the present invention will not be repeated here. For specific operations, please refer to the prior art.

[0012] The present invention has found in the process of exploration that due to the presence of a large number of hydroxyl groups on the surface of regenerated diatomite, it has strong hydrophilicity and water absorption. When the regenerated diatomite is directly added to the water environment as a floating carrier, it will settle rapidly. However, due to the lipophilicity, hydrophobicity and low density of organic pollutants PAHs and SPAHs, organic pollutants PAHs and SPAHs are more inclined to gather and float on the upper water surface of sewage. Therefore, when regenerated diatomite is directly used as a floating carrier, the photocatalytic performance of PAHs and SPAHs is reduced. Therefore, in order to avoid the above situation, the present invention preferably uses a silane coupling agent as a hydrophobic modifier, and the bio-regenerated diatomite is hydrophobically modified by a silane coupling agent, thereby giving the bio-regenerated diatomite a floating property, so that it can float on the water surface, so that the photocatalytic degradation of organic pollutants PAHs and SPAHs can be effectively improved, and the influence of water color and turbidity on the photocatalyst can also be effectively avoided. At the same time, since the hydrophobically modified regenerated diatomaceous earth not only has good floating performance, but also has its own rich pore structure that has an adsorption effect on organic pollutants, and the hydrophobic functional groups on the surface of the hydrophobically modified diatomaceous earth can directly form a strong interaction with the organic pollutants to be removed, the hydrophobically modified diatomaceous earth of the present invention can also improve the removal effect of the organic pollutants to be removed.

[0013] In some preferred embodiments of the present invention, the silane coupling agent used is KH570. After thermal hydrolysis, KH570 can undergo a condensation reaction with the hydroxyl groups on the surface of the regenerated diatomite, and finally an organic hydrophobic layer is wrapped on the surface of the regenerated diatomite through chemical bonds, thereby achieving the final transformation of the regenerated diatomite surface from hydrophilic to hydrophobic.

[0014] The present invention has been found in the process of exploration that in some preferred embodiments of the present invention, when the amount of silane coupling agent KH570 added is too little, the hydrophobic modification of the regenerated diatomite cannot be effectively achieved, so that it cannot float on the water surface. As the amount of KH570 added increases, the hydrophobicity of the regenerated diatomite is significantly enhanced and the self-floating ability is enhanced, but when the amount of silane coupling agent KH570 added is too much, the siloxane anions generated by the hydrolysis of excess KH570 will bond with the surface of the hydrophobically modified diatomite, causing the agglomeration of the regenerated diatomite powder, and then causing the floating performance to decrease. Therefore, in some preferred embodiments of the present invention, when preparing the hydrophobically modified diatomite, 0.6mL~1.5mL of silane coupling agent is added per 10g of biologically regenerated diatomite to ensure that the hydrophobically modified diatomite prepared by the present invention has good floating performance. In some more preferred embodiments of the present invention, when preparing the hydrophobically modified diatomaceous earth, 1.2 mL to 1.5 mL of silane coupling agent is added per 10 g of bio-regenerated diatomaceous earth, and the floating performance is optimal at this time.

[0015] In some preferred embodiments of the present invention, the hydrophobically modified diatomaceous earth is prepared by the following steps: (1) An alcohol solvent and water are mixed in equal volumes to obtain a dispersion solvent; and the regenerated diatomaceous earth is dispersed in the dispersion solvent to obtain a regenerated diatomaceous earth dispersion.

[0016] (2) Dispersing a silane coupling agent in water to hydrolyze the silane coupling agent to obtain a modified liquid.

[0017] (3) After mixing the modified liquid with the regenerated diatomite dispersion solution, stirring the mixture at 65° C. to 75° C., filtering, washing, and drying the mixture, hydrophobically modified diatomite is obtained.

[0018] It should be noted that, in the present invention, the regenerated diatomite and the silane coupling agent are first prepared into solutions, and then mixed, and stirred to allow the silane coupling agent and the regenerated diatomite to fully contact and react, thereby improving the hydrophobic modification effect of the silane coupling agent on the regenerated diatomite.

[0019] In some more preferred embodiments of the present invention, the alcohol solvent used is ethanol.

[0020] In some more preferred embodiments of the present invention, when preparing the regenerated diatomite dispersion, 8 g to 12 g of regenerated diatomite is added per 200 mL of dispersion solvent.

[0021] In some more preferred embodiments of the present invention, when preparing the modified solution, 50 mL of water is added for every 0.6 mL to 1.5 mL of the silane coupling agent.

[0022] In some more preferred embodiments of the present invention, when the regenerated diatomite dispersion and the modifying liquid are mixed, the amount of the regenerated diatomite in the regenerated diatomite dispersion and the silane coupling agent in the modifying liquid satisfies the addition of 0.8 mL to 1.5 mL of silane coupling agent per 10 g of biologically regenerated diatomite.

[0023] In some more preferred embodiments of the present invention, the stirring time of the stirring treatment is 2h~6h.

[0024] In step 2, it should be noted that in some preferred embodiments of the present invention, the adhesive is one or both of polyvinylidene fluoride and polytetrafluoroethylene. In some more preferred embodiments of the present invention, the present invention takes into account the mechanical strength, floating performance and pollutant adsorption capacity of the floating carrier, and preferably uses corrosion-resistant polyvinylidene fluoride as the adhesive, and polyvinyl alcohol as the coating agent, so that a layer of polyvinyl alcohol is formed on the surface of the sheet blank, and the polyvinyl alcohol has super hydrophilicity, so that a layer of hydrophilic film is formed on the surface of the sheet blank, which improves the mass transfer process of pollutants between the floating carrier and the water body, thereby facilitating the organic pollutants in the water body to penetrate the hydrophilic film and combine with the hydrophobically modified diatomaceous earth and the photocatalyst, thereby enhancing the subsequent photocatalytic degradation effect.

[0025] The present invention first mixes an adhesive and an organic solvent to form an adhesive liquid, and then mixes the hydrophobically modified diatomite with the adhesive liquid, so as to improve the bonding effect of the hydrophobically modified diatomite and polyvinyl alcohol through the adhesive. In some preferred embodiments of the present invention, when preparing the blank, 0.6 mL to 1 mL of the adhesive liquid is added per 1 g of the hydrophobically modified diatomite to avoid adding too little adhesive, resulting in poor bonding with polyvinyl alcohol, and then resulting in poor bonding with the photocatalyst; at the same time, it can also avoid adding too much adhesive, which makes it difficult to press into sheets.

[0026] In some preferred embodiments of the present invention, the organic solvent used is one or more of N,N-dimethylacetamide, N-methylpyrrolidone, triethyl phosphate and dimethyl sulfoxide, and when preparing the adhesive solution, 10 mL of organic solvent is added for every 1 g to 2 g of polyvinylidene fluoride to ensure that the concentration of the adhesive in the formed adhesive solution can effectively improve the bonding effect of the hydrophobically modified diatomaceous earth and polyvinyl alcohol.

[0027] In order to ensure that a layer of polyvinyl alcohol can be formed on the surface of the hydrophobically modified diatomaceous earth as a hydrophilic film, in some preferred embodiments of the present invention, when wrapping the coating liquid, 0.3 mL to 0.4 mL of the coating liquid is added for every 0.1 g of the sheet-like body.

[0028] In some preferred embodiments of the present invention, the coating liquid is prepared by the following steps: Polyvinyl alcohol is used as a coating agent, which is dispersed in water and then stirred and dissolved at 80° C. to 90° C.; a cross-linking agent is then added and mixed, and the mixture is cooled to room temperature to obtain the coating liquid.

[0029] It should be noted that, in consideration of the poor water resistance of polyvinyl alcohol, the present invention uses a dicarboxylic acid compound as a crosslinking agent to improve the water resistance of the polyvinyl alcohol. The dicarboxylic acid compound is a compound containing two carboxylic acid functional groups, so that the carboxylic acid group on the added crosslinking agent can react with the hydroxyl group on the polyvinyl alcohol to form an ester group, thereby reducing solubility and enhancing its water resistance and film-forming mechanical properties. In some more preferred embodiments of the present invention, the dicarboxylic acid compound can be selected from any one of succinic acid and maleic acid.

[0030] In some more preferred embodiments of the present invention, when preparing the coating solution, 8 g to 10 g of polyvinyl alcohol is added to every 100 mL of water; and 0.012 mol to 0.015 mol of a cross-linking agent is added to every 100 mL of water.

[0031] In step 3, it should be noted that the present invention does not limit the specific type of photocatalyst powder, and the existing photocatalyst powders in the art can be prepared by the method of the present invention. In some preferred embodiments of the present invention, the photocatalyst used includes a catalytic substrate, and reduced graphene oxide and Ag single substance loaded on the surface of the catalytic substrate. Among them, the catalytic substrate is BiOBr hollow microspheres; the loading amount of the reduced graphene oxide is 2.0wt%~4.0wt% of the mass of the catalytic substrate; the loading amount of the Ag single substance is 1.0wt%~2.0wt% of the mass of the catalytic substrate. For ease of description, the photocatalyst used in the present invention is represented by Ag / rGO / BiOBr.

[0032] In some preferred embodiments of the present invention, the photocatalyst Ag / rGO / BiOBr is prepared by the following steps: (1) Graphene oxide prepared by the improved Hummers method is ultrasonically dispersed in ethylene glycol to obtain a graphene oxide suspension, wherein 100 mL of ethylene glycol is added for every 90 mg to 110 mg of graphene oxide.

[0033] (2) Dispersing bismuth nitrate in ethylene glycol to obtain a bismuth nitrate solution, wherein 25 mL to 35 mL of ethylene glycol is added for every 2 mmol of bismuth nitrate.

[0034] (3) Disperse potassium bromide in ethylene glycol to obtain a potassium bromide solution, wherein 25 mL to 35 mL of ethylene glycol is added for every 2 mmol of potassium bromide.

[0035] (4) After mixing equal volumes of the bismuth nitrate solution and the potassium bromide solution, a first mixed solution is obtained. The graphene oxide suspension is added to the first mixed solution, mixed evenly, transferred to the polytetrafluoroethylene liner of the autoclave, and subjected to solvent thermal reaction at 145°C to 155°C for 8h to 16h, washed and dried to obtain a precursor material. Among them, 0.6mL to 1.5mL of the graphene oxide suspension is added to every 30mL of the first mixed solution.

[0036] (5) Dispersing the precursor material prepared above in water to obtain a precursor solution, wherein 90 mL to 110 mL of water is added per 1 g of the precursor material.

[0037] (6) Disperse silver nitrate in water to form a silver nitrate solution, wherein 7.8 mg to 31.5 mg of silver nitrate is added to every 50 mL of water.

[0038] (7) NaBH 4 Dispersed in water to obtain NaBH 4 Solution.

[0039] (8) Adding the silver nitrate solution to the precursor solution and mixing them to obtain a second mixed solution, wherein the mass ratio of the silver nitrate provided in the silver nitrate solution to the precursor provided in the precursor solution is 7.8-31.5:1.

[0040] (9) Under stirring conditions, the NaBH 4 The solution was added dropwise to the second mixed solution, and the NaBH 4 Solution provided by NaBH 4 The molar ratio of the silver nitrate to the silver nitrate provided in the silver nitrate solution is 2:1.

[0041] (10) The reaction product of step (9) is filtered, washed, dried, and the solid product is collected to obtain the Ag / rGO / BiOBr.

[0042] It should also be noted that in order to improve the bonding effect between the photocatalyst and the floating carrier, the present invention uses the same material as the hydrophilic film component on the surface of the floating carrier as the dispersing material of the photocatalyst. Therefore, in some preferred embodiments of the present invention, the modified polyvinyl alcohol solution is prepared by the following steps: dispersing polyvinyl alcohol in water, then stirring and dissolving at 80°C to 90°C; then, adding a dicarboxylic acid compound, mixing, and cooling to room temperature to obtain the polyvinyl alcohol solution. Among them, 8g to 10g of polyvinyl alcohol is added to every 100mL of water; 0.012mol to 0.015mol of dicarboxylic acid compound is added to every 100mL of water, and the dicarboxylic acid compound can be selected from any one of succinic acid and maleic acid.

[0043] The present invention successfully combines the powdered photocatalytic material with the floating carrier through the coating of the hydrophilic film, thereby improving the photocatalytic performance of the photocatalytic material, as well as the recyclability and regeneration performance. The hydrophilic film formed by the present invention has a strong mass transfer performance, does not affect the adsorption and combination of organic pollutants with the hydrophobic carrier, and does not affect the contact between the pollutants and the catalyst. The aggregation and adsorption of pollutants is achieved, which is also conducive to improving the photocatalytic degradation process.

[0044] In some preferred embodiments of the present invention, when preparing the mixed solution, 1g~2g of the photocatalyst is added to every 10mL of polyvinyl alcohol solution to ensure that the polyvinyl alcohol solution used can evenly disperse the photocatalyst, which is conducive to evenly coating a layer of photocatalytic material on the surface of the floating carrier.

[0045] The present invention also needs to explain that, since the polyvinyl alcohol solution has the same hydrophilic film component as the surface of the floating carrier, the prepared floating composite photocatalytic material has a core-shell structure, wherein the interior is hydrophobically modified diatomaceous earth, and the outer layer is a functional layer of polyvinyl alcohol-coated photocatalyst, wherein the hydrophobicity of the internal hydrophobic modified diatomaceous earth can provide more adsorption sites for organic pollutants such as PAHs and SPAHs; and the functional layer of the outer layer is hydrophilic, which can provide a transmission channel for pollutants in the water phase. Based on the above, it can be seen that the floating composite photocatalytic material of the present invention has an amphiphilic function, and its unique structure of hydrophilic surface and hydrophobic interior enables it to fully contact with pollutants, thereby enabling it to improve the photocatalytic degradation performance of organic pollutants in water.

[0046] The second object of the present invention is to provide a floating composite photocatalytic material prepared by the above preparation method.

[0047] The third object of the present invention is to provide an application of the above-mentioned floating composite photocatalytic material in removing organic pollutants in water.

[0048] Compared with the prior art, the present invention has the following beneficial effects: The present invention uses a silane coupling agent as a hydrophobic modifier, and performs hydrophobic modification on the bioregenerated diatomite through the silane coupling agent, thereby giving the bioregenerated diatomite a floating property, so that it can float on the water surface, so that the photocatalytic degradation of organic pollutants PAHs and SPAHs can be effectively improved, and the influence of water color and turbidity on the photocatalyst can be effectively avoided. At the same time, since the hydrophobically modified regenerated diatomite not only has good floating performance, but also has its own rich pore structure that has an adsorption effect on organic pollutants, and the hydrophobic functional groups on the surface of the hydrophobically modified diatomite can directly form a strong interaction with the organic pollutants to be removed, the hydrophobically modified diatomite of the present invention can also improve the removal effect of the organic pollutants to be removed.

[0049] The present invention uses polyvinylidene fluoride as an adhesive and polyvinyl alcohol as a coating agent, so that a polyvinyl alcohol layer is formed on the surface of the sheet-like body. The polyvinyl alcohol has super hydrophilicity, so that a hydrophilic film is formed on the surface of the sheet-like body, which is beneficial to further improve the composite effect of hydrophobically modified diatomaceous earth and photocatalyst in the aqueous solution environment.

[0050] The preparation method of the present invention has simple process operation, and the raw materials used are easily available and low in cost. The photocatalyst component of the present invention is directly combined with the carrier for good effect. The floating composite photocatalytic material prepared by the present invention is not limited by the color and turbidity of the water body, and can effectively improve the photocatalytic performance of the floating composite photocatalytic material, greatly improving the removal effect of the organic pollutants to be removed. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 The contact angle test results of the hydrophobically modified diatomaceous earth prepared in Examples 1 to 3 and Comparative Example 1 are as follows: Figure 1 , (a) shows the contact angle test result of the bioregenerated diatomaceous earth of comparative example 1, (b) shows the contact angle test result of the bioregenerated diatomaceous earth of embodiment 2, (c) shows the contact angle test result of the bioregenerated diatomaceous earth of embodiment 1, and (d) shows the contact angle test result of the bioregenerated diatomaceous earth of embodiment 3.

[0052] Figure 2 The internal structure and surface contact angle test results of the floating composite photocatalytic material prepared in Example 3 are as follows: Figure 2 In the figure, (a) shows the contact angle test result of the internal structure of the floating composite photocatalytic material prepared in Example 3, and (b) shows the contact angle test result of the surface of the floating composite photocatalytic material prepared in Example 3.

[0053] Figure 3 The electron scanning electron microscope images of the hydrophobically modified diatomaceous earth of Example 3, the bioregenerated diatomaceous earth of Comparative Example 1 and the commercially available new diatomaceous earth are shown in FIG. Figure 3 In the figure, (a) is a scanning electron microscope image of commercially available new diatomaceous earth, (b) is a scanning electron microscope image of the bioregenerated diatomaceous earth of Comparative Example 1, (c) is a scanning electron microscope image of the hydrophobically modified diatomaceous earth of Example 3 at a scale of 2 μm, and (d) is a scanning electron microscope image of the hydrophobically modified diatomaceous earth of Example 3 at a scale of 1 μm.

[0054] Figure 4 This is a scanning electron microscope image of the floating composite photocatalytic material prepared in Example 3. Figure 4 In the figure, Figure a is an electron scanning electron microscope image of the surface of the floating composite photocatalytic material prepared in Example 3 at a scale of 5 μm, Figure b is an electron scanning electron microscope image of the cross-sectional structure of the floating composite photocatalytic material prepared in Example 3 at a scale of 10 μm, Figure c is an electron scanning electron microscope image of the surface of the floating composite photocatalytic material prepared in Example 3 at a scale of 1 μm, Figure d is an electron scanning electron microscope image of the cross-sectional structure of the floating composite photocatalytic material prepared in Example 3 at a scale of 5 μm, Figure e is an electron scanning electron microscope image of another area on the surface of the floating composite photocatalytic material prepared in Example 3 at a scale of 1 μm, and Figure f is an electron scanning electron microscope image of the cross-sectional structure of the floating composite photocatalytic material prepared in Example 3 at a scale of 1 μm.

[0055] Figure 5 The floating condition of the floating composite photocatalytic material prepared in Example 3 within 21 days. Figure 5 In the figure, Figure a shows the floating condition of 15 pieces of the floating composite photocatalytic material prepared in Example 3 after being placed in an open beaker filled with tap water, Figure b shows the floating condition of 15 pieces of the floating composite photocatalytic material prepared in Example 3 after being placed in an open beaker filled with tap water for 7 days, Figure c shows the floating condition of 15 pieces of the floating composite photocatalytic material prepared in Example 3 after being placed in an open beaker filled with tap water for 14 days, and Figure d shows the floating condition of 15 pieces of the floating composite photocatalytic material prepared in Example 3 after being placed in an open beaker filled with tap water for 21 days.

[0056] Figure 6 These are the test results of the photocatalytic degradation performance of the floating composite photocatalytic material of Example 3 on Phe, Ant, Pyr, 3,6-DMP, 2-MAQ and 1-NP.

[0057] Figure 7 This is the electron spin resonance spectrum of the floating composite photocatalytic material of Example 3, Figure 7 In the figure, (a) is the electron spin resonance spectrum of DMPO-·OH of the floating composite photocatalytic material of Example 3 under different light conditions, (b) is the electron spin resonance spectrum of DMPO-·O of the floating composite photocatalytic material of Example 3 under different light conditions.2 - Electron spin resonance spectrum.

[0058] Figure 8 The degradation efficiency of the floating composite photocatalytic material for Phe and 3,6-DMP after 5 photocatalytic degradation cycles.

[0059] Fig. 9 The morphological characterization and analysis results of the floating composite photocatalytic material before and after 5 photocatalytic degradation cycles. Fig. 9 In the figure, Figure a is a macroscopic morphology photograph of the original floating composite photocatalytic material that has not undergone 5 photocatalytic degradation cycles, Figure b is a macroscopic morphology photograph of the floating composite photocatalytic material recovered after 5 photocatalytic degradation cycles, Figure c is an internal morphology image of the floating composite photocatalytic material recovered after 5 photocatalytic degradation cycles, and Figure d is a surface morphology image of the floating composite photocatalytic material recovered after 5 photocatalytic degradation cycles.

[0060] Fig.10 The contact angle test results of the surface and internal cross-section of the floating composite photocatalytic material recovered after 5 photocatalytic degradation cycles are shown in Figure 2. Fig.10 In the figure, Figure a shows the contact angle test results of the internal structure of the floating composite photocatalytic material recovered after 5 photocatalytic degradation cycles, and Figure b shows the contact angle test results of the surface of the floating composite photocatalytic material recovered after 5 photocatalytic degradation cycles. DETAILED DESCRIPTION

[0061] The technical solutions in the embodiments of the present invention are described clearly and completely below. It should be noted that the bioregenerated diatomaceous earth used in the following embodiments of the present invention is based on the DOI number 10.1016 / j.jbiosc.2018.08.004 and is entitled “Highly efficient deproteinization with anammonifying bacteria Lysinibacillus fusiformis The process is carried out under the optimal conditions of biological deproteinization treatment in the prior art of "isolated from brewery spent diatomite", so the present invention will not be repeated here. For specific operations, please refer to the prior art.

[0062] In the following embodiments of the present invention, the photocatalysts used are all BiOBr hollow microspheres as the catalytic matrix, and the surface is loaded with reduced graphene oxide and Ag single substance photocatalysts. For the convenience of description, it is recorded as Ag / rGO / BiOBr, and the Ag / rGO / BiOBr used is specifically prepared by the following steps: (1) 100 mg of graphene oxide prepared by the improved Hummers method was ultrasonically dispersed in 100 mL of ethylene glycol to obtain a graphene oxide suspension.

[0063] (2) Disperse 2 mmol of bismuth nitrate in 15 mL of ethylene glycol to obtain a bismuth nitrate solution.

[0064] (3) Disperse 2 mmol of potassium bromide in 15 mL of ethylene glycol to obtain a potassium bromide solution.

[0065] (4) After mixing equal volumes of the bismuth nitrate solution and the potassium bromide solution, a first mixed solution is obtained. 1 mL of the graphene oxide suspension obtained in step (1) is added to the first mixed solution, mixed evenly, transferred into the polytetrafluoroethylene liner of a high-pressure reactor, subjected to solvothermal reaction at 150° C. for 12 h, washed and dried, and a precursor material is obtained.

[0066] (5) Disperse 1 g of the precursor material prepared above in 100 mL of deionized water to obtain a precursor solution.

[0067] (6) Disperse 19 mg of silver nitrate in 50 mL of deionized water to form a silver nitrate solution.

[0068] (7) NaBH 4 Dispersed in deionized water to obtain NaBH 4 Solution.

[0069] (8) Add the silver nitrate solution prepared above to the precursor solution prepared above and mix well to obtain a second mixed solution.

[0070] (9) Under stirring conditions, the NaBH 4 The solution was added dropwise to the second mixed solution, and the NaBH 4 Solution provided by NaBH 4 The molar ratio of the silver nitrate to the silver nitrate provided in the silver nitrate solution is 2:1.

[0071] (10) The reaction product of step (9) is filtered, washed, dried, and the solid product is collected to obtain the Ag / rGO / BiOBr.

[0072] Example 1 This embodiment provides a method for preparing a floating composite photocatalytic material, comprising the following steps: Step 1, hydrophobic modification of bioregenerated diatomaceous earth: Step 1.1, ethanol and water are mixed in equal volumes to obtain a dispersion solvent; 8 g to 12 g of regenerated diatomaceous earth is dispersed in 200 mL of the dispersion solvent to obtain a regenerated diatomaceous earth dispersion.

[0073] Step 1.2, dispersing 1.2 mL of silane coupling agent KH570 in 50 mL of deionized water to hydrolyze the silane coupling agent KH570 to obtain a modified solution.

[0074] Step 1.3, after mixing the modified liquid prepared above with the regenerated diatomite dispersion solution prepared above, stirring at 70° C. for 4 hours, filtering to obtain a solid component, washing it alternately with anhydrous ethanol and deionized water for 3 times, and drying it at 60° C. for 6 hours to obtain hydrophobically modified diatomite.

[0075] Step 2, surface hydrophilization treatment: Step 2.1, 1.5 g of polyvinylidene fluoride is dispersed in 10 mL of N,N-dimethylacetamide to obtain a binding solution. Subsequently, 1 g of hydrophobically modified diatomaceous earth is mixed with 0.8 mL of the binding solution to form a blank.

[0076] Step 2.2, adding the blank into a mold with a diameter of 1 cm, demolding after pressing into sheets, and then drying at 80° C. for 6 hours to obtain sheet-like blanks, each sheet-like blank weighing 0.1 g.

[0077] Step 2.3, using polyvinyl alcohol as the coating agent, dispersing 9 g of polyvinyl alcohol in 100 mL of deionized water, and stirring to dissolve at 85° C.; then adding 0.0135 mol, i.e. 1.6 g of succinic acid, mixing well, and cooling to room temperature to obtain a coating solution.

[0078] Step 2.4, add 0.3 mL of the above-prepared coating liquid to a plastic perforated plate with a pore size of 1.4 cm, put the sheet blank in and immerse it completely, and after the coating liquid is evenly wrapped on the surface of the diatomite sheet, add 0.1 mL of the coating liquid, put the porous plate in an oven, and dry it at 60°C until the diatomite sheet is completely dried and naturally demolded to obtain a floating carrier, recorded as RD.

[0079] Step 3, loading the photocatalyst on the floating carrier: Step 3.1, disperse 9 g of polyvinyl alcohol in 100 mL of deionized water, and stir to dissolve at 85° C.; then add 1.6 g of succinic acid, mix well, and cool to room temperature to obtain a modified polyvinyl alcohol solution.

[0080] Step 3.2, dispersing 1.5 g of photocatalyst powder Ag / rGO / BiOBr in 10 mL of the modified polyvinyl alcohol solution obtained in the above step 3.1 to obtain a mixed solution.

[0081] Step 3.3, add 0.3 mL of the mixed solution into a plastic well plate with a pore size of 1.4 cm, then put in the floating carrier RD, and add 0.1 mL of the mixed solution after the floating carrier RD is completely immersed. Put the porous plate into an oven and immerse and dry it at 58°C to allow the mixed solution to complete the change of the solidified film on the surface of the carrier, so as to stably load the photocatalyst on the floating carrier, and obtain a floating composite photocatalytic material, recorded as Ag / rGO / BiOBr-RD.

[0082] Example 2 This embodiment provides a method for preparing a floating composite photocatalytic material, comprising the following steps: Step 1, hydrophobic modification of bioregenerated diatomaceous earth: Step 1.1, ethanol and water are mixed in equal volumes to obtain a dispersion solvent; 12 g of regenerated diatomaceous earth is dispersed in 200 mL of the dispersion solvent to obtain a regenerated diatomaceous earth dispersion.

[0083] Step 1.2, dispersing 0.6 mL of silane coupling agent KH570 in 50 mL of deionized water to hydrolyze the silane coupling agent KH570 to obtain a modified solution.

[0084] Step 1.3, after mixing the modified liquid prepared above with the regenerated diatomite dispersion solution prepared above, stirring at 65° C. for 6 hours, filtering to obtain a solid component, washing it alternately with anhydrous ethanol and deionized water for 3 times, and drying it at 60° C. for 6 hours to obtain hydrophobically modified diatomite.

[0085] Step 2, surface hydrophilization treatment: Step 2.1, 1 g of polytetrafluoroethylene is dispersed in 10 mL of N-methylpyrrolidone to obtain a binding solution. Subsequently, 1 g of hydrophobically modified diatomaceous earth is mixed with 0.6 mL of the binding solution to form a blank.

[0086] Step 2.2, adding the blank into a mold with a diameter of 1 cm, demolding after pressing into sheets, and then drying at 80° C. for 6 hours to obtain sheet-like blanks, each sheet-like blank weighing 0.1 g.

[0087] Step 2.3, using polyvinyl alcohol as the coating agent, dispersing 8 g of polyvinyl alcohol in 100 mL of deionized water, and stirring to dissolve at 80° C.; then adding 0.012 mol of maleic acid, mixing, and cooling to room temperature to obtain a coating solution.

[0088] Step 2.4, after adding 0.3 mL of the above-prepared coating liquid to a plastic perforated plate with a pore size of 1.4 cm, put the sheet blank in and immerse it completely. After the coating liquid is evenly wrapped on the surface of the diatomite sheet, add 0.1 mL of the above-prepared coating liquid, put the porous plate in an oven, and dry it at 60°C until the diatomite sheet is completely dried and naturally demolded to obtain a floating carrier, recorded as RD.

[0089] Step 3, loading the photocatalyst on the floating carrier: Step 3.1, disperse 8 g of polyvinyl alcohol in 100 mL of deionized water, and stir to dissolve at 80° C.; then add 1.5 g of maleic acid, mix well, and cool to room temperature to obtain a modified polyvinyl alcohol solution.

[0090] Step 3.2, dispersing 1 g of photocatalyst powder Ag / rGO / BiOBr in 10 mL of the modified polyvinyl alcohol solution obtained in the above step 3.1 to obtain a mixed solution.

[0091] Step 3.3, add 0.3 mL of the mixed solution into a plastic well plate with a pore size of 1.4 cm, then put in the floating carrier RD, and add 0.1 mL of the mixed solution after the floating carrier RD is completely immersed. Put the porous plate into an oven and immerse and dry it at 55°C to allow the mixed solution to complete the change of the solidified film on the surface of the carrier, so as to stably load the photocatalyst on the floating carrier, and obtain a floating composite photocatalytic material, recorded as Ag / rGO / BiOBr-RD.

[0092] Example 3 This embodiment provides a method for preparing a floating composite photocatalytic material, comprising the following steps: Step 1, hydrophobic modification of bioregenerated diatomaceous earth: 1.1) Ethanol and water are mixed in equal volumes to obtain a dispersion solvent; 12 g of regenerated diatomaceous earth is dispersed in 200 mL of the dispersion solvent to obtain a regenerated diatomaceous earth dispersion.

[0093] 2) Disperse 1.5 mL of silane coupling agent KH570 in 50 mL of deionized water to hydrolyze the silane coupling agent KH570 to obtain a modified solution.

[0094] 3) The modified liquid prepared above was mixed with the regenerated diatomite dispersion solution prepared above, and then stirred at 75° C. for 2 h. The solid component was filtered to obtain a solid component, and then washed alternately with anhydrous ethanol and deionized water for 3 times, and then dried at 60° C. for 6 h to obtain hydrophobically modified diatomite.

[0095] Step 2, surface hydrophilization treatment: Step 2.1, 2 g of polyvinylidene fluoride is dispersed in 10 mL of dimethyl sulfoxide to obtain a binding solution. Subsequently, 1 g of hydrophobically modified diatomaceous earth is mixed with 1 mL of the binding solution to form a blank.

[0096] Step 2.2, adding the blank into a mold with a diameter of 1 cm, pressing into sheets, demoulding, and then drying at 80° C. for 6 h to obtain sheet-like blanks, each sheet-like blank weighing 0.1 g.

[0097] Step 2.3, using polyvinyl alcohol as the coating agent, dispersing 10 g of polyvinyl alcohol in 100 mL of deionized water, and stirring to dissolve at 90° C.; then adding 0.015 mol of succinic acid, mixing, and cooling to room temperature to obtain a coating solution.

[0098] Step 2.4, add 0.3 mL of the above-prepared coating liquid to a plastic perforated plate with a pore size of 1.4 cm, put the sheet blank in and immerse it completely, and after the coating liquid is evenly wrapped on the surface of the diatomite sheet, add 0.1 mL of the coating liquid, put the porous plate in an oven, and dry it at 60°C until the diatomite sheet is completely dried and naturally demolded to obtain a floating carrier, recorded as RD.

[0099] Step 3, loading the photocatalyst on the floating carrier: Step 3.1, disperse 10 g of polyvinyl alcohol in 100 mL of deionized water, and stir to dissolve at 90° C.; then add 1.7 g of succinic acid, mix well, and cool to room temperature to obtain a modified polyvinyl alcohol solution.

[0100] Step 3.2, dispersing 2 g of photocatalyst powder Ag / rGO / BiOBr in 10 mL of the modified polyvinyl alcohol solution obtained in the above step 3.1 to obtain a mixed solution.

[0101] Step 3.3, add 0.3 mL of the mixed solution into a plastic well plate with a pore size of 1.4 cm, then put in the floating carrier RD, and add 0.1 mL of the mixed solution after the floating carrier RD is completely immersed. Put the porous plate in an oven and immerse and dry it at 60°C to allow the mixed solution to complete the change of the solidified film on the surface of the carrier, so as to achieve the stable loading of the photocatalyst on the floating carrier, and obtain a floating composite photocatalytic material, recorded as Ag / rGO / BiOBr-RD.

[0102] Comparative Example 1 The difference between this comparative example and Example 3 is that: In this comparative example, no silane coupling agent was added, that is, the bio-regenerated diatomaceous earth was not subjected to hydrophobic modification.

[0103] Comparative Example 2 The difference between this comparative example and Example 3 is that: In this comparative example, when preparing the hydrophobically modified diatomaceous earth, 1.8 mL of silane coupling agent was added per 10 g of bioregenerated diatomaceous earth.

[0104] Experimental Section 1. Hydrophobicity test The present invention takes the bioregenerated diatomite of comparative example 1 and the hydrophobically modified diatomite of examples 1 to 3 as examples, and performs hydrophobicity tests on them respectively by using the contact angle test, and the test results are as follows: Figure 1 shown.

[0105] Figure 1 The contact angle test results of the hydrophobically modified diatomaceous earth prepared in Examples 1 to 3 and Comparative Example 1 are as follows: Figure 1 , (a) shows the contact angle test result of the bioregenerated diatomaceous earth of comparative example 1, (b) shows the contact angle test result of the bioregenerated diatomaceous earth of embodiment 2, (c) shows the contact angle test result of the bioregenerated diatomaceous earth of embodiment 1, and (d) shows the contact angle test result of the bioregenerated diatomaceous earth of embodiment 3.

[0106] Figure 1 By comparing Figure (b) and Figure (a), it can be seen that the contact angle of the hydrophobically modified diatomite obtained after the modification treatment in Example 1 is increased from 39.9° to 64.8° compared with the unmodified bio-regenerated diatomite in Comparative Example 1, which indicates that the present invention can indeed achieve hydrophobic modification of the surface of the bio-regenerated diatomite by using a silane coupling agent as a hydrophobic modifier. Figure 1 By comparing Figure (c), Figure (d) and Figure (a), it can be seen that when the amount of silane coupling agent added is increased, the contact angle of the hydrophobically modified diatomaceous earth modified in Example 2 and Example 3 is 113.3°~114.6°, showing strong hydrophobicity.

[0107] When the amount of silane coupling agent added in the present invention is further increased to 1.8 mL of silane coupling agent per 10 g of bio-regenerated diatomite, the siloxane anions generated by the hydrolysis of excess KH570 will bond with the surface of the hydrophobically modified diatomite, causing agglomeration of the regenerated diatomite powder, which is not conducive to its hydrophobic floating.

[0108] Therefore, based on the above, the present invention preferably adds 0.6mL~1.5mL of silane coupling agent per 10g of bioregenerated diatomite when preparing the hydrophobically modified diatomite to ensure that the hydrophobically modified diatomite prepared by the present invention has good floating performance. More preferably, 1.2mL~1.5mL of silane coupling agent is added per 10g of bioregenerated diatomite. And because the hydrophobically modified diatomite prepared in the above-mentioned Examples 1 to 3 has similar properties, the floating composite photocatalytic material finally prepared therefrom also has similar properties. In order to avoid redundant description, the following part of the present invention will take Example 3 as an example to analyze the structure and properties of the floating composite photocatalytic material prepared by the present invention.

[0109] The present invention also takes the floating composite photocatalytic material prepared in Example 3 as an example, and uses the contact angle test to test the hydrophobicity of the overall structure surface and the internal structure after the section, and the test results are as follows: Figure 2 shown.

[0110] Figure 2 The internal structure and surface contact angle test results of the floating composite photocatalytic material prepared in Example 3 are as follows: Figure 2 In the figure, (a) shows the contact angle test result of the internal structure of the floating composite photocatalytic material prepared in Example 3, and (b) shows the contact angle test result of the surface of the floating composite photocatalytic material prepared in Example 3.

[0111] Figure 2 As can be seen from Figure (a), the internal structure of the floating composite photocatalytic material prepared in Example 3 is the same as that of the hydrophobically modified diatomaceous earth, maintaining good hydrophobicity, and the hydrophobic angle is >133°. As can be seen from Figure (b), the surface of the floating composite photocatalytic material prepared in Example 3 exhibits good hydrophilicity due to the presence of the PVA film. Figure 2 It is clear that there is a significant difference in the hydrophobicity of the interior and surface of the floating composite photocatalytic material prepared by the present invention, that is, the floating composite photocatalytic material of the present invention is amphiphilic, and the hydrophobic property of the hydrophobic modified diatomaceous earth inside it can provide more adsorption sites for organic pollutants such as PAHs and SPAHs, while the hydrophilic PVA outer film on the surface provides a transmission channel for pollutants in the water phase. The unique structure of the hydrophilic surface and hydrophobic interior of the floating composite photocatalytic material of the present invention enables it to fully contact with pollutants and lays the foundation for the subsequent photocatalytic degradation process of pollutants.

[0112] (II) Morphological and structural characteristics In order to further observe the effect of KH570 hydrophobic modification on the microstructure of regenerated diatomite, the present invention also takes the hydrophobic modified diatomite of Example 3, the biologically regenerated diatomite of Comparative Example 1 and the commercially available new diatomite as examples, and performs electron scanning electron microscopy tests on them respectively, and the test results are as follows: Figure 3 shown.

[0113] Figure 3 The electron scanning electron microscope images of the hydrophobically modified diatomaceous earth of Example 3, the bioregenerated diatomaceous earth of Comparative Example 1 and the commercially available new diatomaceous earth are shown in FIG. Figure 3 In the figure, (a) is a scanning electron microscope image of commercially available new diatomaceous earth, (b) is a scanning electron microscope image of the bioregenerated diatomaceous earth of Comparative Example 1, (c) is a scanning electron microscope image of the hydrophobically modified diatomaceous earth of Example 3 at a scale of 2 μm, and (d) is a scanning electron microscope image of the hydrophobically modified diatomaceous earth of Example 3 at a scale of 1 μm.

[0114] Figure 3 As can be seen from Figure (a), the microstructure of the new diatomite is a disc with a smooth surface, and a large number of pore channels are evenly distributed in the middle and edge parts of the disc.

[0115] Figure 3 By comparing Figure (b) and Figure (a), it can be seen that the bioregenerated diatomite obtained by the bioregeneration treatment of the present invention is consistent with the microscopic morphology of the new diatomite, with a smooth surface and rich pore structure.

[0116] Figure 3 By comparing Figure (c), Figure (d) and Figure (a), it can be seen that the hydrophobically modified diatomite after hydrophobic modification of the present invention is also consistent with the microscopic morphology of the new diatomite, which indicates that the hydrophobic modification treatment of the present invention mainly hydrophobically modifies the diatomite by chemical bonding, and will not cause blockage and change to the pore structure of the regenerated diatomite.

[0117] The present invention also takes the floating composite photocatalytic material prepared in Example 3 as an example, and performs electron scanning electron microscopy tests on its surface morphology and internal structure morphology of the cross section, and the test results are as follows: Figure 4 shown.

[0118] Figure 4 This is a scanning electron microscope image of the floating composite photocatalytic material prepared in Example 3. Figure 4In the figure, Figure a is an electron scanning electron microscope image of the surface of the floating composite photocatalytic material prepared in Example 3 at a scale of 5 μm, Figure b is an electron scanning electron microscope image of the cross-sectional structure of the floating composite photocatalytic material prepared in Example 3 at a scale of 10 μm, Figure c is an electron scanning electron microscope image of the surface of the floating composite photocatalytic material prepared in Example 3 at a scale of 1 μm, Figure d is an electron scanning electron microscope image of the cross-sectional structure of the floating composite photocatalytic material prepared in Example 3 at a scale of 5 μm, Figure e is an electron scanning electron microscope image of another area on the surface of the floating composite photocatalytic material prepared in Example 3 at a scale of 1 μm, and Figure f is an electron scanning electron microscope image of the cross-sectional structure of the floating composite photocatalytic material prepared in Example 3 at a scale of 1 μm.

[0119] It can be seen from the test results of 4 that in the floating composite photocatalytic material prepared in Example 3, the surface of the RD carrier is flat and the inside is rough, the boundary between the PVA outer film and the regenerated diatomite matrix is ​​clear, and the pore morphology of the regenerated diatomite is complete. After Ag / rGO / BiOBr is loaded, the surface of the carrier remains smooth, but regular round convexities appear, which corresponds to the hollow microsphere structure of Ag / rGO / BiOBr shown in Figure c. Further observation of the PVA film part in the cross section of the floating composite photocatalytic material shows that the hollow and microsphere structures belonging to Ag / rGO / BiOBr are clearly visible, proving that Ag / rGO / BiOBr is successfully loaded on the surface of the RD carrier.

[0120] (III) Floating performance test The present invention takes the floating composite photocatalytic material prepared in Example 3 as an example. 15 pieces of the floating composite photocatalytic material prepared in Example 3 are placed in an open beaker filled with tap water and continuously magnetically stirred for 21 days. The floating conditions are recorded every 7 days, and the recorded results are organized as follows: Figure 5 shown.

[0121] Figure 5 The floating condition of the floating composite photocatalytic material prepared in Example 3 within 21 days. Figure 5 In the figure, Figure a shows the floating condition of 15 pieces of the floating composite photocatalytic material prepared in Example 3 after being placed in an open beaker filled with tap water, Figure b shows the floating condition of 15 pieces of the floating composite photocatalytic material prepared in Example 3 after being placed in an open beaker filled with tap water for 7 days, Figure c shows the floating condition of 15 pieces of the floating composite photocatalytic material prepared in Example 3 after being placed in an open beaker filled with tap water for 14 days, and Figure d shows the floating condition of 15 pieces of the floating composite photocatalytic material prepared in Example 3 after being placed in an open beaker filled with tap water for 21 days.

[0122] Depend on Figure 5It can be seen from the recorded results that the floating composite photocatalytic material prepared in Example 3 is light in weight. After being added to the beaker, it quickly contacts with water, and the PVA film on its surface is quickly soaked and completely floats on the water surface. After being placed for 21 days, the floating rate of the floating composite photocatalytic material prepared in Example 3 is still 100%, which shows that the floating composite photocatalytic material prepared in the present invention has excellent floating performance.

[0123] (IV) Photocatalytic degradation performance The present invention selects 3-ring phenanthrene and anthracene, 4-ring pyrene and its corresponding derivatives 3,6-dimethylphenanthrene, 2-methylanthraquinone and 1-nitropyrene as target pollutants, and uses the floating composite photocatalytic material prepared in Example 3 as a photocatalyst to explore the photocatalytic degradation ability of the floating composite photocatalytic material of the present invention on different PAHs and SPAHs, and the test results are as follows: Figure 6 For the convenience of description, the present invention will use Phe to represent phenanthrene, Ant to represent anthracene, Pyr to represent pyrene, 3,6-DMP to represent 3,6-dimethylphenanthrene, 2-MAQ to represent 2-methylanthraquinone, and 1-NP to represent 1-nitropyrene.

[0124] The test method is: 2 mL of sample is taken at each sampling time point, centrifuged to remove particulate matter, and then diluted 1:1 with acetonitrile, filtered through a 0.22 μm needle with a 1 mL syringe, and transferred to a 1.5 mL brown injection bottle for testing. The concentrations of Phe, Ant, Pyr, 3,6-DMP, 2-MAQ and 1-NP are determined by high performance liquid chromatography.

[0125] A high performance liquid chromatography instrument of Agilent 1260II was used, equipped with an Eclipse Plus 95A C18 column with a size of 3.5 μm and 4.6×150 mm. The specific test conditions were: methanol and water with a volume ratio of 85:15 as the mobile phase. Isocratic elution, flow rate 0.8 mL / min, column temperature 30°C, injection volume 10 μL.

[0126] Figure 6 These are the test results of the photocatalytic degradation performance of the floating composite photocatalytic material of Example 3 on Phe, Ant, Pyr, 3,6-DMP, 2-MAQ and 1-NP.

[0127] Depend on Figure 6It can be seen that after 12 hours of dark reaction, the floating composite photocatalytic material of Example 3 has reached adsorption equilibrium for the six target pollutants of Phe, Ant, Pyr, 3,6-DMP, 2-MAQ and 1-NP, and the adsorption removal rates of the floating composite photocatalytic material of Example 3 for these six pollutants are all in the range of 5.4% to 29.2%. Among them, the adsorption removal rates of the floating composite photocatalytic material for Ant and 1-NP are significantly lower than those for other pollutants. This may be because the water solubility of Ant and 1-NP is slightly lower than that of other pollutants, which makes them hindered when passing through the hydrophilic PVA membrane, and even requires a longer water exchange time to fully combine with the internal hydrophobic carrier. Although the adsorption removal rate of Ant is the lowest in the dark reaction stage, the degradation effect of the floating composite photocatalytic material on it under sunlight conditions is significantly better than that of other pollutants. After 12 hours of photocatalytic degradation by the floating composite photocatalytic material, most PAHs and SPAHs except 1-NP can achieve a removal rate of more than 70%, among which 3-ring Phe and 3,6-DMP, and 4-ring Pyr are relatively close in degradation effect and degradation rate. It can be seen that compared with NPAHs, OPAHs and MPAHs can be better degraded by floating composite photocatalytic materials. Although there are literature reports that the higher the number of PAHs rings, the easier it is to be photodegraded, the floating composite photocatalytic material of the present invention is a core-shell structure with a hydrophilic surface and a hydrophobic interior, and its contact mode with pollutants is more complicated than that of powdered photocatalytic materials.

[0128] In order to further explore the photocatalytic degradation mechanism of the floating composite photocatalytic material of Example 3, the present invention conducted free radical detection and analysis under visible light and ultraviolet light conditions, and the test results are as follows: Figure 7 shown.

[0129] Figure 7 This is the electron spin resonance spectrum of the floating composite photocatalytic material of Example 3, Figure 7 In the figure, (a) is the electron spin resonance spectrum of DMPO-·OH of the floating composite photocatalytic material of Example 3 under different light conditions, (b) is the electron spin resonance spectrum of DMPO-·O of the floating composite photocatalytic material of Example 3 under different light conditions. 2 - The electron spin resonance spectrum of Figure 7 The test results show that O was detected under both visible light and ultraviolet light conditions. 2 - The generation of ·OH and ·OH, which are strong surface oxidative free radicals, plays a major role in the photocatalytic degradation of PAHs and SPAHs by floating composite photocatalysts. 2 -The characteristic peak intensity of ·OH is close to that of ·OH, which may be because Ag / rGO / BiOBr is loaded on the floating regenerated diatomite carrier RD in the form of a hydrophilic PVA film. The presence of PVA changes the interaction between Ag / rGO / BiOBr and H 2 O and O 2 The contact mode and exchange efficiency affect the intensity of the generated free radicals.

[0130] (V) Analysis of regeneration performance of floating composite photocatalytic materials The catalytic stability and recycling performance of solid photocatalysts are important bases for the feasibility of their practical application. The present invention retrieves and recycles the sheet-like floating composite photocatalytic material floating above the water surface after the photocatalytic degradation of Phe and its methyl derivative 3,6-DMP in the above-mentioned part (IV), and reuses the recovered floating composite photocatalytic material for the photocatalytic degradation of Phe and its methyl derivative 3,6-DMP in a cyclic degradation manner. The photocatalytic degradation cycle is repeated 5 times, and the degradation efficiency of the floating composite photocatalytic material on Phe and 3,6-DMP in the 5 photocatalytic degradation cycles is analyzed to evaluate the regeneration performance of the floating composite photocatalytic material of Example 3. The test results are as follows: Figure 8 shown.

[0131] Figure 8 is the degradation efficiency of the floating composite photocatalytic material for five photocatalytic degradation cycles of Phe and 3,6-DMP, Figure 8 It can be seen from the test results that after 5 photocatalytic degradation cycles, the degradation efficiency of the floating composite photocatalytic material prepared in Example 3 for Phe and 3,6-DMP is maintained above 83% and 72%, respectively, which indicates that the floating composite photocatalytic material prepared by the present invention has excellent photocatalytic stability.

[0132] The present invention also collects and recycles the floating composite photocatalyst material after five cycles of photocatalytic degradation, removes ions and washes it, then performs low-temperature forced air drying at 40°C, and characterizes the morphology of the recovered floating composite photocatalyst material and the morphology of the original floating composite photocatalyst material that has not undergone photocatalytic degradation, respectively. The characterization analysis results are as follows: Fig. 9 shown.

[0133] Fig. 9 The morphological characterization and analysis results of the floating composite photocatalytic material before and after 5 photocatalytic degradation cycles. Fig. 9In the figure, Figure a is a macroscopic morphology photograph of the original floating composite photocatalytic material that has not undergone 5 photocatalytic degradation cycles, Figure b is a macroscopic morphology photograph of the floating composite photocatalytic material recovered after 5 photocatalytic degradation cycles, Figure c is an internal morphology image of the floating composite photocatalytic material recovered after 5 photocatalytic degradation cycles, and Figure d is a surface morphology image of the floating composite photocatalytic material recovered after 5 photocatalytic degradation cycles.

[0134] Fig. 9 By comparing the test results of Figure b and Figure a, it can be seen that compared with the original floating composite photocatalytic material that has not undergone a photocatalytic degradation cycle, the surface of the recycled floating composite photocatalytic material has some wrinkles. However, from the test results of Figure c and Figure d, it can be seen that the PVA film structure on the surface of the floating composite photocatalytic material recycled after the photocatalytic degradation cycle is intact, and the regenerated diatomaceous earth carrier inside it still maintains good hydrophobic properties, which shows that the floating composite photocatalytic material prepared by combining the photocatalytic material with the carrier in the present invention can not only improve the light energy utilization rate of the catalytic material, but also facilitate secondary recycling, and the recycled floating composite photocatalytic material still has stable floating performance, which provides a good prerequisite for its practical application.

[0135] The present invention also conducted a hydrophobic analysis on the surface and internal cross-section of the above-mentioned floating composite photocatalytic material recovered after 5 photocatalytic degradation cycles through contact angle experiments, and the results are as follows: Fig.10 shown.

[0136] Fig.10 The contact angle test results of the surface and internal cross-section of the floating composite photocatalytic material recovered after 5 photocatalytic degradation cycles are shown in Figure 2. Fig.10 In the figure, Figure a shows the contact angle test results of the internal structure of the floating composite photocatalytic material recovered after 5 photocatalytic degradation cycles, and Figure b shows the contact angle test results of the surface of the floating composite photocatalytic material recovered after 5 photocatalytic degradation cycles.

[0137] Depend on Fig.10It can be seen from the test results that the surface contact angle of the floating composite photocatalyst material recovered after 5 photocatalytic degradation cycles decreased from the original 70° to 44°, which indicates that the hydrophilicity of the PVA film of the floating composite photocatalyst material is significantly enhanced, which is more conducive to the transfer of pollutants from the water phase to the catalytic material. The surface contact angle of the regenerated diatomaceous earth matrix inside the floating composite photocatalyst material is 117°, which indicates that the hydrophobicity of the regenerated diatomaceous earth matrix inside the floating composite photocatalyst material of the present invention is well maintained, which is not only conducive to the adsorption and binding of organic pollutants on the catalytic material, but also fully guarantees the floating stability of the synthetic photocatalyst material. The above shows that the recovery and regeneration method of the floating composite photocatalyst prepared by the present invention is simple, and the floating composite photocatalyst material has a stable structure, stable photocatalytic activity and stable floating performance.

[0138] Obviously, the above embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Claims

1. A method for preparing a floating composite photocatalytic material, characterized in that: The following steps are involved: Using bioregenerated diatomite obtained by bioregeneration technology as raw material and silane coupling agent as hydrophobic modifier, the surface of the bioregenerated diatomite is subjected to hydrophobic modification treatment to obtain hydrophobically modified diatomite; The hydrophobically modified diatomaceous earth is mixed with a binding liquid to form a blank; the blank is pressed into a sheet, and dried to obtain a sheet-like blank; a layer of coating liquid is coated on the surface of the sheet-like blank, and then dried, so that the coating liquid forms a hydrophilic film on the surface of the sheet-like blank after solidification, thereby obtaining a floating carrier; The photocatalyst powder is dispersed in a polyvinyl alcohol solution to obtain a mixed solution; the floating carrier is immersed in the mixed solution, and then dried to solidify the mixed solution into a film, so as to stably load the photocatalyst on the floating carrier to obtain a floating composite photocatalytic material.

2. The method for preparing a floating composite photocatalytic material according to claim 1, characterized in that: The photocatalyst comprises a catalytic substrate, and reduced graphene oxide and Ag elemental substance loaded on the surface of the catalytic substrate; Wherein, the catalytic matrix is ​​BiOBr hollow microspheres; The loading amount of the reduced graphene oxide is 2.0wt% to 4.0wt% of the mass of the catalytic substrate; The loading amount of the Ag single substance is 1.0wt%~2.0wt% of the mass of the catalytic substrate.

3. The method for preparing a floating composite photocatalytic material according to claim 1, characterized in that: The silane coupling agent is KH570; When preparing the hydrophobically modified diatomaceous earth, 0.6 mL to 1.5 mL of silane coupling agent is added per 10 g of biologically regenerated diatomaceous earth.

4. The method for preparing a floating composite photocatalytic material according to claim 1, characterized in that: The adhesive liquid is obtained by mixing an adhesive and an organic solvent; Wherein, the adhesive is one or both of polyvinylidene fluoride and polytetrafluoroethylene; The organic solvent is one or more of N,N-dimethylacetamide, N-methylpyrrolidone, triethyl phosphate and dimethyl sulfoxide; When preparing the adhesive solution, 10 mL of organic solvent is added for every 1 g to 2 g of polyvinylidene fluoride.

5. The method for preparing a floating composite photocatalytic material according to claim 1, characterized in that: When preparing the blank, 0.6 mL to 1 mL of the binding liquid is added per 1 g of the hydrophobically modified diatomaceous earth.

6. The method for preparing a floating composite photocatalytic material according to claim 1, characterized in that: The coating liquid is prepared by the following steps: Using polyvinyl alcohol as a coating agent, dispersing it in water, stirring and dissolving it at 80° C. to 90° C.; then adding a cross-linking agent, mixing, and cooling to room temperature to obtain the coating liquid; Wherein, the cross-linking agent is a dicarboxylic acid compound; Add 8g~10g polyvinyl alcohol per 100mL water; 0.012 mol to 0.015 mol of the cross-linking agent is added per 100 mL of water.

7. The method for preparing a floating composite photocatalytic material according to claim 1, characterized in that: When wrapping the coating liquid, 0.3 mL to 0.4 mL of the coating liquid is added per 0.1 g of the sheet-like green body.

8. The method for preparing a floating composite photocatalytic material according to claim 1, characterized in that: The modified polyvinyl alcohol solution is prepared by the following steps: Dispersing polyvinyl alcohol in water, and then stirring and dissolving at 80° C. to 90° C.; then adding a dicarboxylic acid compound, mixing, and cooling to room temperature to obtain the modified polyvinyl alcohol solution; Among them, 8g~10g of polyvinyl alcohol is added to every 100mL of water; Add 0.012mol~0.015mol of dicarboxylic acid compound per 100mL of water; When preparing the mixed solution, 1 g to 2 g of the photocatalyst is added to every 10 mL of polyvinyl alcohol solution.

9. A floating composite photocatalytic material prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the floating composite photocatalytic material according to claim 9 for removing organic pollutants in water.

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