A floating composite photocatalytic material and its preparation method and application

Abstract

The present invention belongs to the field of photocatalytic water treatment technology, and discloses a floating composite photocatalytic material, its preparation method and application. The preparation method is as follows: using bioregenerated diatomaceous earth as raw material, hydrophobically modified with a silane coupling agent to obtain hydrophobically modified diatomaceous earth; compounding the hydrophobically modified diatomaceous earth with a binder and a coating liquid to obtain a floating carrier; forming a mixed liquid with a photocatalyst powder and a polyvinyl alcohol solution; immersing the floating carrier in the mixed liquid and then heating and curing it to stably load the photocatalyst on the hydrophobic floating carrier to obtain an amphiphilic floating composite photocatalytic material. The preparation method of the present invention has simple process operation, and the raw materials used are easily available and low in cost. The direct combination of the photocatalyst component and the carrier in the floating composite photocatalytic material of the present invention has a good effect, is not limited by the color and turbidity of the water body, can effectively improve the photocatalytic performance of the floating composite photocatalytic material, and greatly improves the removal effect of the organic pollutants to be removed.

Description

Technical Field

[0001] This invention relates to the field of photocatalytic water treatment technology, and in particular to a floating composite photocatalytic material, its preparation method, and its application. Background Technology

[0002] Urban wastewater treatment plants are considered a major source of organic pollutants in receiving rivers. While conventional biological wastewater treatment processes are effective at removing conventional pollutants such as nitrogen and phosphorus, they are ineffective at removing polycyclic aromatic hydrocarbons (PAHs) and their derivatives due to their recalcitrant nature, high bioaccumulation rate, and significant carcinogenic, teratogenic, and mutagenic effects. PAHs and their derivatives are highly toxic and bioaccumulative, posing potential environmental risks even at low concentrations. Therefore, enhanced removal of PAHs and SPAHs from wastewater treatment plant effluents is of practical significance.

[0003] Currently, among the technologies for removing PAHs pollutants in the aquatic environment, photocatalytic oxidation technology has become one of the most promising technologies for controlling PAHs pollutants due to its low selectivity for pollutants during the removal process, as well as its advantages such as being environmentally friendly, stable, and having recyclable high-efficiency photocatalysts. Furthermore, photocatalytic oxidation technology with semiconductor catalytic materials as its core has significant advantages in treating recalcitrant and highly toxic organic wastewater.

[0004] BiOBr is an indirect bandgap semiconductor. Its unique electronic structure, stable chemical properties, and excellent visible light absorption capabilities have led to its widespread application in visible light photocatalytic degradation. However, its utilization rate of visible light is significantly lower than that of TiO2 for ultraviolet light. Moreover, BiOBr is usually in powder form, and the catalyst particles are relatively fine and tend to agglomerate after being added to an aqueous environment, making it difficult to separate and recover from the reaction solution after use. This also limits its application range to some extent.

[0005] To address the aforementioned technical problems, those skilled in the art have proposed loading the catalyst onto a support material to facilitate its recycling. Currently, existing technologies for composite photocatalysts and support materials primarily employ methods such as spraying and coating. However, these methods suffer from cumbersome, complex, and costly preparation steps. Furthermore, the resulting composite material exhibits poor bonding between the photocatalyst and the support, leading to easy detachment of the photocatalyst from the support surface during use. In addition, the wastewater surface often has poor transparency, limiting the photocatalytic performance of the composite material due to water color and turbidity, thus significantly restricting its ability to remove organic pollutants from the aquatic environment. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a floating composite photocatalytic material, its preparation method, and its application.

[0007] The present invention provides a floating composite photocatalytic material, its preparation method, and its application, which are achieved through the following technical solutions:

[0008] The first objective of this invention is to provide a method for preparing a floating composite photocatalytic material, comprising the following steps:

[0009] Step 1, hydrophobic modification treatment of bio-regenerated diatomaceous earth:

[0010] Using bio-regenerated diatomaceous earth obtained through bio-regeneration technology as raw material, and silane coupling agent as hydrophobic modifier, the surface of the bio-regenerated diatomaceous earth is subjected to hydrophobic modification treatment to obtain hydrophobic modified diatomaceous earth.

[0011] Step 2, Surface hydrophilization treatment:

[0012] The hydrophobic modified diatomaceous earth is mixed with the binder to form a blank; the blank is pressed into a sheet 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 the coating liquid solidifies to form a layer of polyvinyl alcohol on the surface of the sheet-like blank, thus obtaining a floating carrier.

[0013] Step 3: Loading the photocatalyst onto the floating support:

[0014] The photocatalyst powder is dispersed in a polyvinyl alcohol solution to obtain a mixture; the floating carrier is immersed in the mixture, and then impregnated and dried at 55℃~60℃ to allow the mixture to solidify and form a film on the surface of the carrier, thereby achieving stable loading of the photocatalyst on the floating carrier to obtain a floating composite photocatalyst material.

[0015] In step 1, it should be noted that the present invention takes into account the use of waste diatomaceous earth, which is discarded due to pore blockage and reduced adsorption capacity generated from the beer filtration process, as raw material. This not only enables the resource reuse of waste diatomaceous earth and alleviates environmental pressure, but also allows the waste diatomaceous earth to regain its pollutant adsorption capacity through its unique porous structure after undergoing deproteinization treatment using biological regeneration technology.

[0016] It should also be noted that the biological deproteinization technology used in this invention is referenced in DOI 10.1016 / j.jbiosc.2018.08.004, entitled "Highly efficient deproteinization with anammonifying bacteria". Lysinibacillus fusiformis The biological deproteinization process, which is isolated from brewery spentdiatomite, is carried out under the optimal conditions in the prior art. Therefore, the present invention will not elaborate on it here. For specific operation details, please refer to the prior art.

[0017] During the exploration process, this invention discovered that the presence of numerous hydroxyl groups on the surface of regenerated diatomaceous earth gives it strong hydrophilicity and water absorption. When directly added to an aquatic environment as a floating carrier, it rapidly settles. Organic pollutants PAHs and SPASHs, being lipophilic, hydrophobic, and low in density, tend to accumulate and float on the surface of wastewater. Therefore, directly using regenerated diatomaceous earth as a floating carrier reduces the photocatalytic performance of PAHs and SPASHs. To avoid this, this invention preferably uses a silane coupling agent as a hydrophobic modifier. By modifying the bio-regenerated diatomaceous earth with this agent, it acquires floating properties, enabling it to float on the water surface. This effectively improves the photocatalytic degradation of PAHs and SPASHs while also effectively avoiding the influence of water color and turbidity on the photocatalyst. Meanwhile, since the hydrophobically modified regenerated diatomaceous earth not only has good floating properties, but also its rich pore structure 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.

[0018] In some preferred embodiments of the present invention, the silane coupling agent used is KH570. After hot hydrolysis, KH570 can undergo a condensation reaction with the hydroxyl groups on the surface of the regenerated diatomaceous earth, and finally encapsulate the surface of the regenerated diatomaceous earth with an organic hydrophobic layer through chemical bonding, thereby realizing the transformation of the surface of the regenerated diatomaceous earth from hydrophilic to hydrophobic.

[0019] During the exploration process, it was discovered that in some preferred embodiments of the present invention, when the amount of silane coupling agent KH570 added is too small, it cannot effectively modify the hydrophobicity of regenerated diatomaceous earth, making it unable to float on the water surface. As the amount of KH570 added increases, the hydrophobicity and self-floating ability of the regenerated diatomaceous earth are significantly enhanced. However, when the amount of silane coupling agent KH570 added is too large, the siloxane anions generated by the hydrolysis of excessive KH570 will bond with the surface of the hydrophobically modified diatomaceous earth, causing the regenerated diatomaceous earth powder to agglomerate, thus leading to a decrease in floating performance. Therefore, in some preferred embodiments of the present invention, when preparing the hydrophobically modified diatomaceous earth, 0.6 mL to 1.5 mL of silane coupling agent is added per 10 g of bio-regenerated diatomaceous earth to ensure that the hydrophobically modified diatomaceous earth prepared by the present invention has good floating performance. In some preferred embodiments of the present invention, when preparing the hydrophobically modified diatomite, 1.2 mL to 1.5 mL of silane coupling agent is added per 10 g of bio-regenerated diatomite, at which point the floating performance is optimal.

[0020] In some preferred embodiments of the present invention, the hydrophobically modified diatomaceous earth is specifically prepared through the following steps:

[0021] (1) Mix alcohol solvent and water in equal volumes to obtain a dispersion solvent; disperse the regenerated diatomaceous earth in the dispersion solvent to obtain a regenerated diatomaceous earth dispersion.

[0022] (2) Disperse the silane coupling agent in water to hydrolyze the silane coupling agent to obtain a modified solution.

[0023] (3) After mixing the modified liquid with the regenerated diatomaceous earth dispersion solution, the mixture is stirred at 65℃~75℃, filtered, washed and dried to obtain hydrophobic modified diatomaceous earth.

[0024] It should be noted that the present invention improves the hydrophobic modification effect of the silane coupling agent on the regenerated diatomaceous earth by first preparing solutions of the regenerated diatomaceous earth and the silane coupling agent separately, then mixing them, and then stirring to ensure that the silane coupling agent and the regenerated diatomaceous earth are in full contact and react.

[0025] In some more preferred embodiments of the present invention, the alcohol solvent used is ethanol.

[0026] In some more preferred embodiments of the present invention, when preparing the regenerated diatomaceous earth dispersion, 8g to 12g of regenerated diatomaceous earth is added per 200mL of dispersion solvent.

[0027] In some more preferred embodiments of the present invention, when preparing the modified liquid, 50 mL of water is added for every 0.6 mL to 1.5 mL of silane coupling agent.

[0028] In some more preferred embodiments of the present invention, when mixing the regenerated diatomaceous earth dispersion and the modified liquid, the amount of regenerated diatomaceous earth in the regenerated diatomaceous earth dispersion and the amount of silane coupling agent in the modified liquid are such that 0.8 mL to 1.5 mL of silane coupling agent is added for every 10 g of biologically regenerated diatomaceous earth.

[0029] In some more preferred embodiments of the present invention, the stirring time of the stirring treatment is 2h to 6h.

[0030] 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 (PVDF) and polytetrafluoroethylene (PTFE). In some more preferred embodiments of the present invention, by comprehensively considering the mechanical strength, buoyancy, and pollutant adsorption capacity of the floating carrier, the present invention preferably uses corrosion-resistant PVDF as the adhesive and polyvinyl alcohol (PVA) as the coating agent, so that a layer of PVA is formed on the surface of the sheet-like preform. PVA has superhydrophilicity, thereby forming a hydrophilic film on the surface of the sheet-like preform, improving the mass transfer process of pollutants between the floating carrier and the water body, thus facilitating the penetration of organic pollutants in the water through the hydrophilic film and their binding with the hydrophobically modified diatomaceous earth and photocatalyst, thereby enhancing the subsequent photocatalytic degradation effect.

[0031] This invention first mixes an adhesive and an organic solvent to form an adhesive liquid, then mixes the hydrophobically modified diatomaceous earth with the adhesive liquid to improve the bonding effect between the hydrophobically modified diatomaceous earth and polyvinyl alcohol through the adhesive. Furthermore, in some preferred embodiments of this invention, when preparing the blank, 0.6 mL to 1 mL of the adhesive liquid is added per 1 g of the hydrophobically modified diatomaceous earth to avoid insufficient adhesive addition, which would lead to poor bonding with polyvinyl alcohol and consequently poor bonding with the photocatalyst; it also avoids excessive adhesive addition, which would make it difficult to compress into sheets.

[0032] 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 liquid, 10 mL of organic solvent is added for every 1 g to 2 g of polyvinylidene fluoride to ensure that the concentration of adhesive in the formed adhesive liquid can effectively improve the bonding effect between hydrophobic modified diatomaceous earth and polyvinyl alcohol.

[0033] To ensure that a layer of polyvinyl alcohol as a hydrophilic film can be formed on the surface of the hydrophobically modified diatomaceous earth, in some preferred embodiments of the present invention, 0.3 mL to 0.4 mL of coating liquid is added for every 0.1 g of the sheet preform when coating the film.

[0034] In some preferred embodiments of the present invention, the coating solution is prepared by the following steps:

[0035] Polyvinyl alcohol was used as the coating agent. It was dispersed in water and stirred to dissolve at 80°C to 90°C. Then, a crosslinking agent was added and mixed well. The mixture was cooled to room temperature to obtain the coating solution.

[0036] It should be noted that, considering the poor water resistance of polyvinyl alcohol (PVA), this invention incorporates a dicarboxylic acid compound as a crosslinking agent to improve the water resistance of PVA. The dicarboxylic acid compound is a compound containing two carboxylic acid functional groups. This allows the carboxylic acid groups on the added crosslinking agent to react with the hydroxyl groups on PVA to form ester groups, reducing solubility and enhancing its water resistance and film-forming mechanical properties. Furthermore, in some more preferred embodiments of this invention, the dicarboxylic acid compound may be selected from either succinic acid or maleic acid.

[0037] In some more preferred embodiments of the present invention, when preparing the coating solution, 8 g to 10 g of polyvinyl alcohol is added per 100 mL of water; and 0.012 mol to 0.015 mol of crosslinking agent is added per 100 mL of water.

[0038] In step 3, it should be noted that this invention does not limit the specific type of photocatalyst powder; all existing photocatalyst powders in the art can be prepared using the method of this invention. In some preferred embodiments of this invention, the photocatalyst includes a catalytic matrix, and reduced graphene oxide and Ag element supported on the surface of the catalytic matrix. The catalytic matrix is ​​a BiOBr hollow microsphere; the loading amount of reduced graphene oxide is 2.0 wt% to 4.0 wt% of the mass of the catalytic matrix; and the loading amount of Ag element is 1.0 wt% to 2.0 wt% of the mass of the catalytic matrix. For ease of description, the photocatalyst used in this invention will be referred to as Ag / rGO / BiOBr below.

[0039] In some preferred embodiments of the present invention, the photocatalyst Ag / rGO / BiOBr is prepared through the following steps:

[0040] (1) Graphene oxide prepared by the modified Hummers method was ultrasonically dispersed in ethylene glycol to obtain a graphene oxide suspension. 100 mL of ethylene glycol was added for every 90 mg to 110 mg of graphene oxide.

[0041] (2) Disperse bismuth nitrate in ethylene glycol to obtain a bismuth nitrate solution. For every 2 mmol of bismuth nitrate, add 25 mL to 35 mL of ethylene glycol.

[0042] (3) Disperse potassium bromide in ethylene glycol to obtain a potassium bromide solution. For every 2 mmol of potassium bromide, add 25 mL to 35 mL of ethylene glycol.

[0043] (4) The bismuth nitrate solution and the potassium bromide solution are mixed in equal volumes to obtain a first mixed solution. The graphene oxide suspension is added to the first mixed solution, mixed well, and transferred to the polytetrafluoroethylene liner of a high-pressure reactor. The mixture is then subjected to a solvothermal reaction at 145℃~155℃ for 8h~16h. After washing and drying, the precursor material is obtained. 0.6mL~1.5mL of graphene oxide suspension is added to every 30mL of the first mixed solution.

[0044] (5) Disperse the above-prepared precursor material in water to obtain a precursor solution. Add 90 mL to 110 mL of water for every 1 g of precursor material.

[0045] (6) Disperse silver nitrate in water to form a silver nitrate solution. Add 7.8 mg to 31.5 mg of silver nitrate to every 50 mL of water.

[0046] (7) Disperse NaBH4 in water to obtain NaBH4 solution.

[0047] (8) The silver nitrate solution is added to the precursor solution and mixed to obtain a second mixed solution. The mass ratio of silver nitrate provided in the silver nitrate solution to the precursor provided in the precursor solution is 7.8~31.5:1.

[0048] (9) Under stirring conditions, the NaBH4 solution is added dropwise to the second mixed solution, and the molar ratio of NaBH4 provided by the NaBH4 solution to silver nitrate provided by the silver nitrate solution is 2:1.

[0049] (10) After filtering the reaction product of step (9) above, wash and dry it, and collect the solid product to obtain the Ag / rGO / BiOBr.

[0050] It should also be noted that, in order to improve the binding effect between the photocatalyst and the floating support, this invention uses a material with the same hydrophilic film composition as the photocatalyst dispersion material as the surface of the floating support. Therefore, in some preferred embodiments of this 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 and mixing, cooling to room temperature to obtain the polyvinyl alcohol solution. Specifically, 8g to 10g of polyvinyl alcohol is added per 100mL of water; 0.012mol to 0.015mol of a dicarboxylic acid compound is added per 100mL of water, and the dicarboxylic acid compound can be selected from either succinic acid or maleic acid.

[0051] This invention utilizes a hydrophilic membrane coating to successfully combine powdered photocatalytic materials with a floating support, thereby improving the photocatalytic performance, as well as the recyclability and reusability of the photocatalytic materials. Furthermore, the hydrophilic membrane formed by this invention exhibits strong mass transfer properties, does not affect the adsorption and binding of organic pollutants to the hydrophobic support, nor does it impede the contact between pollutants and the catalyst. This allows for the aggregation and adsorption of pollutants, which also contributes to enhancing the photocatalytic degradation process.

[0052] In some preferred embodiments of the present invention, when preparing the mixture, 1g to 2g of the photocatalyst is added to every 10mL of polyvinyl alcohol solution to ensure that the photocatalyst can be uniformly dispersed in the polyvinyl alcohol solution, thereby facilitating the uniform coating of a photocatalytic material layer on the surface of the floating carrier.

[0053] Furthermore, this invention also explains that, because the polyvinyl alcohol solution and the hydrophilic film composition on the surface of the floating carrier are the same, the prepared floating composite photocatalytic material has a core-shell structure. The inner layer is hydrophobically modified diatomaceous earth, and the outer layer is a functional layer of polyvinyl alcohol-coated photocatalyst. The hydrophobicity of the inner hydrophobically modified diatomaceous earth provides more adsorption sites for organic pollutants such as PAHs and SPAHs; while the outer functional layer is hydrophilic, providing transport channels for pollutants in the aqueous phase. Based on the above, the floating composite photocatalytic material of this invention has amphiphilic properties. Its unique structure, with a hydrophilic surface and hydrophobic interior, allows for sufficient contact with pollutants, thereby improving its photocatalytic degradation performance of organic pollutants in water.

[0054] The second objective of this invention is to provide a floating composite photocatalytic material prepared by the above-described preparation method.

[0055] A third objective of this invention is to provide an application of the above-mentioned floating composite photocatalytic material in the removal of organic pollutants from water.

[0056] Compared with the prior art, the present invention has the following beneficial effects:

[0057] This invention uses a silane coupling agent as a hydrophobic modifier to hydrophobically modify bio-regenerated diatomaceous earth, thereby endowing it with floating properties. This allows it to float on water, effectively improving the photocatalytic degradation of organic pollutants PAHs and SPHAs, while also effectively avoiding the influence of water color and turbidity on the photocatalyst. Furthermore, because the hydrophobically modified regenerated diatomaceous earth not only has excellent floating properties, but its rich porous structure also adsorbs organic pollutants. Additionally, the hydrophobic functional groups on the surface of the hydrophobically modified diatomaceous earth can form strong interactions with the organic pollutants to be removed, further enhancing the removal efficiency of these pollutants.

[0058] This invention uses polyvinylidene fluoride as a binder and polyvinyl alcohol as a coating agent to form a polyvinyl alcohol layer on the surface of the sheet-like preform. Polyvinyl alcohol has superhydrophilicity, which allows a hydrophilic film to be formed on the surface of the sheet-like preform. This is beneficial for further improving the composite effect of hydrophobically modified diatomite and photocatalyst in an aqueous environment.

[0059] The preparation method of this invention is simple to operate, the raw materials used are readily available and low in cost, and the photocatalyst components of this invention have a good direct binding effect with the carrier. Furthermore, the floating composite photocatalyst material prepared by this invention is not limited by the color and turbidity of the water body, and can effectively improve the photocatalytic performance of the floating composite photocatalyst material, greatly improving the removal effect of the organic pollutants to be removed. Attached Figure Description

[0060] Figure 1 The contact angle test results are for the hydrophobically modified diatomaceous earth prepared in Examples 1-3 and Comparative Example 1. Figure 1 In the figures, (a) shows the contact angle test results of the bio-regenerated diatomite in Comparative Example 1, (b) shows the contact angle test results of the bio-regenerated diatomite in Example 2, (c) shows the contact angle test results of the bio-regenerated diatomite in Example 1, and (d) shows the contact angle test results of the bio-regenerated diatomite in Example 3.

[0061] Figure 2 The results show the internal structure and surface contact angle of the floating composite photocatalyst material prepared in Example 3. Figure 2 In the figure, (a) shows the contact angle test results of the internal structure of the floating composite photocatalyst material prepared in Example 3, and (b) shows the contact angle test results of the surface of the floating composite photocatalyst material prepared in Example 3.

[0062] Figure 3The images are scanning electron microscope (SEM) images of the hydrophobically modified diatomite of Example 3, the bio-regenerated diatomite of Comparative Example 1, and commercially available new diatomite. Figure 3 In the figures, (a) is a scanning electron microscope (SEM) image of commercially available new diatomite, (b) is a scanning electron microscope (SEM) image of bio-regenerated diatomite of Comparative Example 1, (c) is a scanning electron microscope (SEM) image of hydrophobic modified diatomite of Example 3 at the 2 μm scale, and (d) is a scanning electron microscope (SEM) image of hydrophobic modified diatomite of Example 3 at the 1 μm scale.

[0063] Figure 4 This is a scanning electron microscope image of the floating composite photocatalyst material prepared in Example 3. Figure 4 In the figures, a) is a scanning electron microscope (SEM) image of the surface of the floating composite photocatalyst material prepared in Example 3 at a scale of 5 μm; b) is a scanning electron microscope (SEM) image of the cross-sectional structure of the floating composite photocatalyst material prepared in Example 3 at a scale of 10 μm; c) is a scanning electron microscope (SEM) image of the surface of the floating composite photocatalyst material prepared in Example 3 at a scale of 1 μm; d) is a scanning electron microscope (SEM) image of the cross-sectional structure of the floating composite photocatalyst material prepared in Example 3 at a scale of 5 μm; e) is a scanning electron microscope (SEM) image of another region of the surface of the floating composite photocatalyst material prepared in Example 3 at a scale of 1 μm; and f) is a scanning electron microscope (SEM) image of the cross-sectional structure of the floating composite photocatalyst material prepared in Example 3 at a scale of 1 μm.

[0064] Figure 5 The floating behavior of the floating composite photocatalyst material prepared in Example 3 over 21 days is shown. Figure 5 Figure a shows the floating state of 15 pieces of the floating composite photocatalyst material prepared in Example 3 after being placed in an open beaker filled with tap water; Figure b shows the floating state of 15 pieces of the floating composite photocatalyst material prepared in Example 3 after being placed in an open beaker filled with tap water for 7 days; Figure c shows the floating state of 15 pieces of the floating composite photocatalyst 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 state of 15 pieces of the floating composite photocatalyst material prepared in Example 3 after being placed in an open beaker filled with tap water for 21 days.

[0065] Figure 6 The results show the photocatalytic degradation performance of the floating composite photocatalytic material in Example 3 on Phe, Ant, Pyr, 3,6-DMP, 2-MAQ and 1-NP.

[0066] Figure 7 The image shows the electron spin resonance spectrum of the floating composite photocatalytic material in Example 3. Figure 7In Figure (a), the electron spin resonance spectra of the floating composite photocatalyst material of Example 3 under different light conditions are shown; in Figure (b), the electron spin resonance spectra of the floating composite photocatalyst material of Example 3 under different light conditions are shown. - The electron spin resonance spectrum.

[0067] Figure 8 The degradation efficiency of floating composite photocatalytic materials for Phe and 3,6-DMP in 5 photocatalytic degradation cycles was determined.

[0068] Figure 9 The results are the morphological characterization analysis of the floating composite photocatalytic material before and after five photocatalytic degradation cycles. Figure 9 In the figure, a) is a macroscopic morphology photograph of the original floating composite photocatalyst material before undergoing 5 photocatalytic degradation cycles; b) is a macroscopic morphology photograph of the recovered floating composite photocatalyst material after 5 photocatalytic degradation cycles; c) is an internal morphology image of the recovered floating composite photocatalyst material after 5 photocatalytic degradation cycles; and d) is a surface morphology image of the recovered floating composite photocatalyst material after 5 photocatalytic degradation cycles.

[0069] Figure 10 The contact angle test results are for the surface and internal cross-sections of the floating composite photocatalytic material recovered after five photocatalytic degradation cycles. Figure 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 Implementation

[0070] The technical solutions in the embodiments of the present invention will be clearly and completely described below. It should be noted that the bio-regenerated diatomaceous earth used in the following embodiments of the present invention is based on DOI number 10.1016 / j.jbiosc.2018.08.004, entitled "Highly efficient deproteinization with anammonifying bacteria". Lysinibacillus fusiformis The biological deproteinization process, which is isolated from brewery spentdiatomite, is carried out under the optimal conditions in the prior art. Therefore, the present invention will not elaborate on it here. For specific operation details, please refer to the prior art.

[0071] In the following embodiments of the present invention, the photocatalysts used are all photocatalysts with BiOBr hollow microspheres as the catalytic matrix and reduced graphene oxide and Ag elemental supported on the surface. For ease of description, they are referred to as Ag / rGO / BiOBr, and the Ag / rGO / BiOBr used is specifically prepared through the following steps:

[0072] (1) 100 mg of graphene oxide prepared by the modified Hummers method was ultrasonically dispersed in 100 mL of ethylene glycol to obtain a graphene oxide suspension.

[0073] (2) Disperse 2 mmol of bismuth nitrate in 15 mL of ethylene glycol to obtain a bismuth nitrate solution.

[0074] (3) Disperse 2 mmol of potassium bromide in 15 mL of ethylene glycol to obtain a potassium bromide solution.

[0075] (4) Mix the above bismuth nitrate solution and the potassium bromide solution in equal volumes to obtain a first mixed solution. Add 1 mL of the graphene oxide suspension obtained in step (1) to the first mixed solution, mix well, transfer to the polytetrafluoroethylene liner of a high-pressure reactor, and solvothermal react at 150°C for 12 h. After washing and drying, the precursor material is obtained.

[0076] (5) Disperse 1g of the above-prepared precursor material in 100mL of deionized water to obtain a precursor solution.

[0077] (6) Disperse 19 mg of silver nitrate in 50 mL of deionized water to form a silver nitrate solution.

[0078] (7) Disperse NaBH4 in deionized water to obtain NaBH4 solution.

[0079] (8) Add the silver nitrate solution prepared above to the precursor solution prepared above and mix well to obtain a second mixed solution.

[0080] (9) Under stirring conditions, the NaBH4 solution is added dropwise to the second mixed solution, and the molar ratio of NaBH4 provided by the NaBH4 solution to silver nitrate provided by the silver nitrate solution is 2:1.

[0081] (10) After filtering the reaction product of step (9) above, wash and dry it, and collect the solid product to obtain the Ag / rGO / BiOBr.

[0082] Example 1

[0083] This embodiment provides a method for preparing a floating composite photocatalytic material, including the following steps:

[0084] Step 1, hydrophobic modification treatment of bio-regenerated diatomaceous earth:

[0085] Step 1.1: Mix ethanol and water in equal volumes to obtain a dispersion solvent; disperse 8g~12g of regenerated diatomaceous earth in 200mL of dispersion solvent to obtain a regenerated diatomaceous earth dispersion.

[0086] Step 1.2: Disperse 1.2 mL of silane coupling agent KH570 in 50 mL of deionized water to hydrolyze the silane coupling agent KH570 and obtain the modified solution.

[0087] Step 1.3: After mixing the modified liquid obtained above with the regenerated diatomaceous earth dispersion obtained above, the mixture is stirred at 70°C for 4 hours, filtered to obtain the solid component, washed three times alternately with anhydrous ethanol and deionized water, and dried at 60°C for 6 hours to obtain hydrophobic modified diatomaceous earth.

[0088] Step 2, Surface hydrophilization treatment:

[0089] Step 2.1: Disperse 1.5g of polyvinylidene fluoride in 10mL of N,N-dimethylacetamide to obtain an adhesive solution. Then, mix 1g of hydrophobically modified diatomaceous earth with 0.8mL of the adhesive solution to form a blank.

[0090] Step 2.2: Add the blank to a mold with a diameter of 1 cm, press it into a sheet, demold it, and then dry it at 80°C for 6 hours to obtain a sheet blank, each sheet blank weighing 0.1 g.

[0091] Step 2.3: Using polyvinyl alcohol as the coating agent, 9g of polyvinyl alcohol is dispersed in 100mL of deionized water and stirred at 85℃ to dissolve; then 0.0135mol, i.e. 1.6g of succinic acid, is added and mixed well, and cooled to room temperature to obtain the coating solution.

[0092] Step 2.4: Add 0.3 mL of the above-prepared coating solution to a plastic perforated plate with a pore size of 1.4 cm, place the sheet blank in the plate and immerse it completely. After the coating solution evenly coats the surface of the diatomaceous earth sheet, add 0.1 mL of coating solution. Place the perforated plate in an oven at 60°C until the sheet diatomaceous earth is completely dry and naturally demolded to obtain the floating carrier, denoted as RD.

[0093] Step 3: Loading the photocatalyst onto the floating support:

[0094] Step 3.1: Disperse 9g of polyvinyl alcohol in 100mL of deionized water and stir to dissolve at 85℃; then add 1.6g of succinic acid, mix well, and cool to room temperature to obtain a modified polyvinyl alcohol solution.

[0095] Step 3.2: Disperse 1.5g of photocatalyst powder Ag / rGO / BiOBr in 10mL of the modified polyvinyl alcohol solution obtained in step 3.1 above to obtain a mixture.

[0096] Step 3.3: Add 0.3 mL of the mixture to a plastic perforated plate with a pore size of 1.4 cm, then place the floating support RD in it. After the floating support RD is completely submerged, add another 0.1 mL of the mixture. Place the perforated plate in an oven and immerse it at 58°C to dry it, so that the mixture can be solidified and coated on the surface of the support, thereby achieving stable loading of the photocatalyst on the floating support and obtaining a floating composite photocatalyst material, denoted as Ag / rGO / BiOBr-RD.

[0097] Example 2

[0098] This embodiment provides a method for preparing a floating composite photocatalytic material, including the following steps:

[0099] Step 1, hydrophobic modification treatment of bio-regenerated diatomaceous earth:

[0100] Step 1.1: Mix ethanol and water in equal volumes to obtain a dispersion solvent; disperse 12g of regenerated diatomaceous earth in 200mL of dispersion solvent to obtain a regenerated diatomaceous earth dispersion.

[0101] Step 1.2: Disperse 0.6 mL of silane coupling agent KH570 in 50 mL of deionized water to hydrolyze the silane coupling agent KH570 and obtain the modified solution.

[0102] Step 1.3: After mixing the modified liquid obtained above with the regenerated diatomaceous earth dispersion obtained above, the mixture is stirred at 65°C for 6 hours, filtered to obtain the solid component, washed three times alternately with anhydrous ethanol and deionized water, and dried at 60°C for 6 hours to obtain hydrophobic modified diatomaceous earth.

[0103] Step 2, Surface hydrophilization treatment:

[0104] Step 2.1: Disperse 1g of polytetrafluoroethylene in 10mL of N-methylpyrrolidone to obtain an adhesive liquid. Then, mix 1g of hydrophobically modified diatomaceous earth with 0.6mL of the adhesive liquid to form a blank.

[0105] Step 2.2: Add the blank to a mold with a diameter of 1 cm, press it into a sheet, demold it, and then dry it at 80°C for 6 hours to obtain a sheet blank, each sheet blank weighing 0.1 g.

[0106] Step 2.3: Using polyvinyl alcohol as the coating agent, disperse 8g of polyvinyl alcohol in 100mL of deionized water and stir to dissolve at 80℃; then add 0.012mol of maleic acid, mix well, and cool to room temperature to obtain the coating solution.

[0107] Step 2.4: Add 0.3 mL of the above-prepared coating solution to a plastic perforated plate with a pore size of 1.4 cm, place the sheet blank in the plate and immerse it completely. After the coating solution evenly coats the surface of the diatomaceous earth sheet, add 0.1 mL of the above-prepared coating solution. Place the perforated plate in an oven at 60°C until the sheet diatomaceous earth is completely dry and naturally demolded to obtain the floating carrier, denoted as RD.

[0108] Step 3: Loading the photocatalyst onto the floating support:

[0109] Step 3.1: Disperse 8g of polyvinyl alcohol in 100mL of deionized water and stir to dissolve at 80℃; then add 1.5g of maleic acid, mix well, and cool to room temperature to obtain a modified polyvinyl alcohol solution.

[0110] Step 3.2: Disperse 1g of photocatalyst powder Ag / rGO / BiOBr in 10mL of the modified polyvinyl alcohol solution obtained in step 3.1 above to obtain a mixture.

[0111] Step 3.3: Add 0.3 mL of the mixture to a plastic perforated plate with a pore size of 1.4 cm, then place the floating carrier RD in it. After the floating carrier RD is completely submerged, add another 0.1 mL of the mixture. Place the perforated plate in an oven and immerse it at 55°C to dry it, so that the mixture can be solidified on the surface of the carrier to form a film, thereby stably loading the photocatalyst onto the floating carrier and obtaining a floating composite photocatalyst material, denoted as Ag / rGO / BiOBr-RD.

[0112] Example 3

[0113] This embodiment provides a method for preparing a floating composite photocatalytic material, including the following steps:

[0114] Step 1, hydrophobic modification treatment of bio-regenerated diatomaceous earth:

[0115] 1.1) Mix ethanol and water in equal volumes to obtain a dispersion solvent; disperse 12g of regenerated diatomaceous earth in 200mL of dispersion solvent to obtain a regenerated diatomaceous earth dispersion.

[0116] 2) Disperse 1.5 mL of silane coupling agent KH570 in 50 mL of deionized water to hydrolyze the silane coupling agent KH570 and obtain the modified solution.

[0117] 3) After mixing the modified liquid obtained above with the regenerated diatomaceous earth dispersion obtained above, the mixture was stirred at 75°C for 2 hours, filtered, and the solid component was obtained. After washing with anhydrous ethanol and deionized water three times alternately, the solid component was dried at 60°C for 6 hours to obtain hydrophobic modified diatomaceous earth.

[0118] Step 2, Surface hydrophilization treatment:

[0119] Step 2.1: Disperse 2g of polyvinylidene fluoride in 10mL of dimethyl sulfoxide to obtain an adhesive liquid. Then, mix 1g of hydrophobically modified diatomaceous earth with 1mL of the adhesive liquid to form a blank.

[0120] Step 2.2: Add the blank to a mold with a diameter of 1 cm, press it into a sheet, demold it, and then dry it at 80°C for 6 hours to obtain a sheet blank, each sheet blank weighing 0.1 g.

[0121] Step 2.3: Using polyvinyl alcohol as the coating agent, 10g of polyvinyl alcohol is dispersed in 100mL of deionized water and stirred at 90℃ to dissolve; then 0.015mol of succinic acid is added and mixed well, and cooled to room temperature to obtain the coating solution.

[0122] Step 2.4: Add 0.3 mL of the above-prepared coating solution to a plastic perforated plate with a pore size of 1.4 cm, place the sheet blank in the plate and immerse it completely. After the coating solution evenly coats the surface of the diatomaceous earth sheet, add 0.1 mL of coating solution. Place the perforated plate in an oven at 60°C until the sheet diatomaceous earth is completely dry and naturally demolded to obtain the floating carrier, denoted as RD.

[0123] Step 3: Loading the photocatalyst onto the floating support:

[0124] Step 3.1: Disperse 10g of polyvinyl alcohol in 100mL of deionized water and stir to dissolve at 90℃; then add 1.7g of succinic acid, mix well, and cool to room temperature to obtain a modified polyvinyl alcohol solution.

[0125] Step 3.2: Disperse 2g of photocatalyst powder Ag / rGO / BiOBr in 10mL of the modified polyvinyl alcohol solution obtained in Step 3.1 above to obtain a mixture.

[0126] Step 3.3: Add 0.3 mL of the mixture to a plastic perforated plate with a pore size of 1.4 cm, then place the floating carrier RD in it. After the floating carrier RD is completely submerged, add another 0.1 mL of the mixture. Place the perforated plate in an oven and immerse it at 60°C to dry it, so that the mixture can be solidified on the surface of the carrier to form a film, thereby stably loading the photocatalyst onto the floating carrier and obtaining a floating composite photocatalyst material, denoted as Ag / rGO / BiOBr-RD.

[0127] Comparative Example 1

[0128] The difference between this comparative example and Example 3 is that:

[0129] In this comparative example, no silane coupling agent was added, meaning that the bio-regenerated diatomaceous earth was not hydrophobically modified.

[0130] Comparative Example 2

[0131] The difference between this comparative example and Example 3 is that:

[0132] In this comparative example, 1.8 mL of silane coupling agent was added for every 10 g of bio-regenerated diatomaceous earth during the preparation of the hydrophobic modified diatomaceous earth.

[0133] Experimental Section

[0134] (a) Hydrophobicity test

[0135] This invention uses the bio-regenerated diatomaceous earth of Comparative Example 1 and the hydrophobically modified diatomaceous earth of Examples 1 to 3 as examples, and conducts hydrophobicity tests on them using contact angle tests, and the test results are as follows. Figure 1 As shown.

[0136] Figure 1 The contact angle test results are for the hydrophobically modified diatomaceous earth prepared in Examples 1-3 and Comparative Example 1. Figure 1 In the figures, (a) shows the contact angle test results of the bio-regenerated diatomite in Comparative Example 1, (b) shows the contact angle test results of the bio-regenerated diatomite in Example 2, (c) shows the contact angle test results of the bio-regenerated diatomite in Example 1, and (d) shows the contact angle test results of the bio-regenerated diatomite in Example 3.

[0137] 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 increased from 39.9° to 64.8° compared with the unmodified bio-regenerated diatomite in Comparative Example 1. This shows that the present invention can indeed achieve hydrophobic modification treatment of the surface of the bio-regenerated diatomite by using silane coupling agent as hydrophobic modifier. Figure 1 By comparing Figures (c), (d), and (a), it can be seen that when the amount of silane coupling agent added is increased, the contact angle of the hydrophobic modified diatomite obtained in Examples 2 and 3 is 113.3°~114.6°, which shows strong hydrophobicity.

[0138] However, when the amount of silane coupling agent added is further increased to 1.8 mL per 10 g of bio-regenerated diatomaceous earth, the excessive amount of siloxane anions generated by the hydrolysis of KH570 will instead bond with the surface of the hydrophobically modified diatomaceous earth, causing the regenerated diatomaceous earth powder to agglomerate, which is not conducive to its hydrophobic floating.

[0139] Therefore, based on the above, in the preferred embodiment of the present invention, 0.6 mL to 1.5 mL of silane coupling agent is added per 10 g of bio-regenerated diatomaceous earth during the preparation of the hydrophobic modified diatomaceous earth to ensure that the hydrophobic modified diatomaceous earth prepared by the present invention has good floating properties. More preferably, 1.2 mL to 1.5 mL of silane coupling agent is added per 10 g of bio-regenerated diatomaceous earth. Furthermore, since the hydrophobic modified diatomaceous earth prepared in Examples 1 to 3 above has similar properties, the floating composite photocatalytic material finally prepared from them also has similar properties. To avoid redundancy, the following section of the present invention will use Example 3 as an example to analyze the structure and properties of the floating composite photocatalytic material prepared by the present invention.

[0140] This invention also uses the floating composite photocatalytic material prepared in Example 3 as an example, and tests the hydrophobicity of its overall structural surface and its internal structure after cross-section using contact angle testing, and the test results are as follows: Figure 2 As shown.

[0141] Figure 2 The results show the internal structure and surface contact angle of the floating composite photocatalyst material prepared in Example 3. Figure 2 In the figure, (a) shows the contact angle test results of the internal structure of the floating composite photocatalyst material prepared in Example 3, and (b) shows the contact angle test results of the surface of the floating composite photocatalyst material prepared in Example 3.

[0142] Figure 2 As shown in Figure (a), the internal structure of the floating composite photocatalyst material prepared in Example 3 is similar to that of the hydrophobically modified diatomaceous earth, maintaining good hydrophobicity with a hydrophobic angle >133°. As shown in Figure (b), the surface of the floating composite photocatalyst material prepared in Example 3 exhibits good hydrophilicity due to the presence of the PVA film. Figure 2 It is clear that the floating composite photocatalytic material prepared in this invention exhibits a significant difference in hydrophobicity between its interior and surface. Specifically, the floating composite photocatalytic material of this invention is amphiphilic; the hydrophobic properties of the hydrophobic modified diatomaceous earth inside provide more adsorption sites for organic pollutants such as PAHs and SPAHs, while the hydrophilic PVA outer membrane on the surface provides a transport channel for pollutants in the aqueous phase. Furthermore, the unique structure of the floating composite photocatalytic material of this invention—hydrophilic on the surface and hydrophobic inside—allows for sufficient contact with pollutants, laying the foundation for the subsequent photocatalytic degradation process of pollutants.

[0143] (II) Morphological and structural characteristics

[0144] To further observe the effect of KH570 hydrophobic modification on the microstructure of regenerated diatomite, this invention also used the hydrophobic modified diatomite of Example 3, the bio-regenerated diatomite of Comparative Example 1, and commercially available new diatomite as examples, and conducted scanning electron microscopy tests on them respectively. The test results are as follows: Figure 3 As shown.

[0145] Figure 3 The images are scanning electron microscope (SEM) images of the hydrophobically modified diatomite of Example 3, the bio-regenerated diatomite of Comparative Example 1, and commercially available new diatomite. Figure 3 In the figures, (a) is a scanning electron microscope (SEM) image of commercially available new diatomite, (b) is a scanning electron microscope (SEM) image of bio-regenerated diatomite of Comparative Example 1, (c) is a scanning electron microscope (SEM) image of hydrophobic modified diatomite of Example 3 at the 2 μm scale, and (d) is a scanning electron microscope (SEM) image of hydrophobic modified diatomite of Example 3 at the 1 μm scale.

[0146] Figure 3 As can be seen from Figure (a), the microstructure of the new diatomite is a smooth disc-shaped structure with a large number of pore channels evenly distributed in the middle and edge of the disc.

[0147] Figure 3 As can be seen from the comparison between Figure (b) and Figure (a), the bio-regenerated diatomite obtained by the bio-regeneration treatment of the present invention has the same microstructure as the new diatomite, with a smooth surface and rich pore structure.

[0148] Figure 3 By comparing Figures (c), (d), and (a), it can be seen that the hydrophobically modified diatomite after the hydrophobic modification of the present invention is consistent with the microstructure of the new diatomite. This indicates that the hydrophobic modification treatment of the present invention mainly modifies the diatomite through chemical bonding and will not cause blockage or change to the pore structure of the regenerated diatomite.

[0149] This invention also takes the floating composite photocatalytic material prepared in Example 3 as an example, and performs scanning electron microscopy tests on its surface morphology and internal structure morphology of cross sections, and the test results are as follows: Figure 4 As shown.

[0150] Figure 4 This is a scanning electron microscope image of the floating composite photocatalyst material prepared in Example 3. Figure 4In the figures, a) is a scanning electron microscope (SEM) image of the surface of the floating composite photocatalyst material prepared in Example 3 at a scale of 5 μm; b) is a scanning electron microscope (SEM) image of the cross-sectional structure of the floating composite photocatalyst material prepared in Example 3 at a scale of 10 μm; c) is a scanning electron microscope (SEM) image of the surface of the floating composite photocatalyst material prepared in Example 3 at a scale of 1 μm; d) is a scanning electron microscope (SEM) image of the cross-sectional structure of the floating composite photocatalyst material prepared in Example 3 at a scale of 5 μm; e) is a scanning electron microscope (SEM) image of another region of the surface of the floating composite photocatalyst material prepared in Example 3 at a scale of 1 μm; and f) is a scanning electron microscope (SEM) image of the cross-sectional structure of the floating composite photocatalyst material prepared in Example 3 at a scale of 1 μm.

[0151] The test results in Figure 4 show that in the floating composite photocatalytic material prepared in Example 3, the RD support has a smooth surface and a rough interior. The boundary between the PVA outer film and the regenerated diatomaceous earth matrix is ​​clear, and the pore morphology of the regenerated diatomaceous earth is intact. After loading Ag / rGO / BiOBr, the surface of the support remains smooth, but regular rounded convexities appear, which corresponds to the hollow microsphere structure of Ag / rGO / BiOBr shown in Figure c. Further observation of the PVA film portion in the cross-section of the floating composite photocatalytic material reveals that the hollow and microsphere structures belonging to Ag / rGO / BiOBr are clearly visible, proving that Ag / rGO / BiOBr was successfully loaded on the surface of the RD support.

[0152] (III) Floating performance test

[0153] Taking the floating composite photocatalytic material prepared in Example 3 as an example, 15 pieces of the floating composite photocatalytic material prepared in Example 3 were placed in an open beaker filled with tap water and continuously magnetically stirred for 21 days. The floating status was recorded every 7 days, and the results were compiled as follows: Figure 5 As shown.

[0154] Figure 5 The floating behavior of the floating composite photocatalyst material prepared in Example 3 over 21 days is shown. Figure 5 Figure a shows the floating state of 15 pieces of the floating composite photocatalyst material prepared in Example 3 after being placed in an open beaker filled with tap water; Figure b shows the floating state of 15 pieces of the floating composite photocatalyst material prepared in Example 3 after being placed in an open beaker filled with tap water for 7 days; Figure c shows the floating state of 15 pieces of the floating composite photocatalyst 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 state of 15 pieces of the floating composite photocatalyst material prepared in Example 3 after being placed in an open beaker filled with tap water for 21 days.

[0155] Depend on Figure 5The recorded results show that the floating composite photocatalyst material prepared in Example 3 is lightweight. After being added to a beaker, it quickly comes into contact with water, and the PVA film on its surface is rapidly wetted, allowing it to float completely on the water surface. Furthermore, after 21 days, the floating composite photocatalyst material prepared in Example 3 still maintains a 100% floatability, indicating that the floating composite photocatalyst material prepared in this invention has excellent buoyancy.

[0156] (iv) Photocatalytic degradation performance

[0157] This invention selects phenanthrene and anthracene (3-rings), pyrene (4-rings) 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 the photocatalyst to investigate the photocatalytic degradation ability of the floating composite photocatalytic material of this invention for different PAHs and SPAHs. The test results are as follows: Figure 6 As shown. In this invention, for ease of description, some terms will be represented by Phe for phenanthrene, Ant for anthracene, Pyr for pyrene, 3,6-DMP for 3,6-dimethylphenanthrene, 2-MAQ for 2-methylanthraquinone, and 1-NP for 1-nitropyrene.

[0158] The testing method was as follows: 2 mL samples were taken at each sampling time point, centrifuged to remove particulate matter, diluted 1:1 with acetonitrile, filtered through a 0.22 μm syringe using a 1 mL syringe, and then transferred to a 1.5 mL brown sample vial for testing. The concentrations of Phe, Ant, Pyr, 3,6-DMP, 2-MAQ, and 1-NP were determined by high performance liquid chromatography.

[0159] An Agilent 1260II high-performance liquid chromatography (HPLC) instrument was used, equipped with an Eclipse Plus 95A C18 column (3.5 μm, 4.6 × 150 mm). Specific test conditions were as follows: methanol and water (85:15 v / v) as the mobile phase; isocratic elution; flow rate 0.8 mL / min; column temperature 30 °C; injection volume 10 μL.

[0160] Figure 6 The results show the photocatalytic degradation performance of the floating composite photocatalytic material in Example 3 on Phe, Ant, Pyr, 3,6-DMP, 2-MAQ and 1-NP.

[0161] Depend on Figure 6It can be seen that after 12 hours of dark reaction, the floating composite photocatalyst material of Example 3 reached adsorption equilibrium for all six target pollutants: Phe, Ant, Pyr, 3,6-DMP, 2-MAQ, and 1-NP. The adsorption removal rates of these six pollutants by the floating composite photocatalyst material of Example 3 ranged from 5.4% to 29.2%. The adsorption removal rates of Ant and 1-NP by the floating composite photocatalyst material were significantly lower than those of other pollutants. This may be because the water solubility of Ant and 1-NP is slightly lower than that of other pollutants, which hinders their passage through the hydrophilic PVA membrane and may even require a longer water exchange time to fully combine with the internal hydrophobic carrier. Although the adsorption removal rate of Ant was the lowest in the dark reaction stage, the degradation effect of the floating composite photocatalyst material on Ant under sunlight conditions was significantly better than that of other pollutants. Furthermore, after 12 hours of photocatalytic degradation using the floating composite photocatalytic material, most PAHs and SPAHs, except for 1-NP, achieved removal rates exceeding 70%. Among them, the 3-ring Phe and 3,6-DMP, and the 4-ring Pyr showed similar degradation effects and rates. This demonstrates that OPAHs and MPAHs are better degraded by the floating composite photocatalytic material compared to NPAHs. Although some literature reports that higher ring numbers in PAHs facilitate photodegradation, the floating composite photocatalytic material of this invention has a core-shell structure with a hydrophilic surface and hydrophobic interior, resulting in a more complex contact mechanism with pollutants compared to powdered photocatalytic materials.

[0162] To further investigate the photocatalytic degradation mechanism of the floating composite photocatalytic material in Example 3, this invention conducted free radical detection and analysis under visible and ultraviolet light conditions, and the test results are as follows: Figure 7 As shown.

[0163] Figure 7 The image shows the electron spin resonance spectrum of the floating composite photocatalytic material in Example 3. Figure 7 In Figure (a), the electron spin resonance spectra of the floating composite photocatalyst material of Example 3 under different light conditions are shown; in Figure (b), the electron spin resonance spectra of the floating composite photocatalyst material of Example 3 under different light conditions are shown. - The electron spin resonance spectrum. (From...) Figure 7 The test results show that ·O2 was detected under both visible and ultraviolet light conditions. - The generation of ·OH radicals, which are strong oxidizing free radicals on the surface, plays a major role in the photocatalytic degradation of PAHs and SPAHs by floating composite photocatalytic materials. Furthermore, ·O2... -The characteristic peak intensity is close to that of ·OH, which may be because Ag / rGO / BiOBr is loaded on the floating regenerated diatomaceous earth carrier RD in the form of a hydrophilic PVA membrane. The presence of PVA changes the contact mode and exchange efficiency between Ag / rGO / BiOBr and H2O and O2, thereby affecting the intensity of the generated free radicals.

[0164] (V) Analysis of the regeneration performance of floating composite photocatalytic materials

[0165] The catalytic stability and recyclability of solid photocatalysts are important indicators of their practical application feasibility. This invention involves the recovery of the sheet-like floating composite photocatalyst material floating on the water surface after photocatalytic degradation of Phe and its methyl derivative 3,6-DMP as described in Part (IV) above. The recovered floating composite photocatalyst material is then reused for photocatalytic degradation of Phe and its methyl derivative 3,6-DMP using a cyclic degradation method. This process is repeated five times. The degradation efficiency of the floating composite photocatalyst material for Phe and 3,6-DMP in these five photocatalytic degradation cycles is analyzed to evaluate the regeneration performance of the floating composite photocatalyst material in Example 3. The test results are as follows: Figure 8 As shown.

[0166] Figure 8 The degradation efficiency of the floating composite photocatalytic material for Phe and 3,6-DMP after 5 photocatalytic degradation cycles is given by... Figure 8 The test results show that after 5 photocatalytic degradation cycles, the floating composite photocatalytic material prepared in Example 3 maintained degradation efficiencies of over 83% and 72% for Phe and 3,6-DMP, respectively. This indicates that the floating composite photocatalytic material prepared in this invention has excellent photocatalytic stability.

[0167] In this invention, the floating composite photocatalytic material after five photocatalytic degradation cycles was retrieved and recovered, then washed with ionomers and dried at 40°C using a low-temperature forced-air drying method. The morphology of the recovered floating composite photocatalytic material and the original floating composite photocatalytic material that had not undergone photocatalytic degradation were characterized, and the characterization results are as follows: Figure 9 As shown.

[0168] Figure 9 The results are the morphological characterization analysis of the floating composite photocatalytic material before and after five photocatalytic degradation cycles. Figure 9In the figure, a) is a macroscopic morphology photograph of the original floating composite photocatalyst material before undergoing 5 photocatalytic degradation cycles; b) is a macroscopic morphology photograph of the recovered floating composite photocatalyst material after 5 photocatalytic degradation cycles; c) is an internal morphology image of the recovered floating composite photocatalyst material after 5 photocatalytic degradation cycles; and d) is a surface morphology image of the recovered floating composite photocatalyst material after 5 photocatalytic degradation cycles.

[0169] Figure 9 In the comparison of the test results in Figures b and a, it can be seen that, compared with the original floating composite photocatalyst material that has not undergone photocatalytic degradation cycle, the surface of the recovered floating composite photocatalyst material shows some wrinkles. However, the test results in Figures c and d show that the PVA film structure on the surface of the recovered floating composite photocatalyst material after photocatalytic degradation cycle is intact, and its internal regenerated diatomaceous earth support still maintains good hydrophobic properties. This indicates that the floating composite photocatalyst material prepared by combining the photocatalyst material with the support in this invention can not only improve the light energy utilization rate of the catalytic material but also facilitate secondary recycling. Furthermore, the recovered floating composite photocatalyst material still has stable floating performance, which provides a good prerequisite for its practical application.

[0170] This invention also conducted hydrophobic analysis on the surface and internal cross-sections of the floating composite photocatalytic material recovered after five photocatalytic degradation cycles using contact angle experiments, and the results are as follows: Figure 10 As shown.

[0171] Figure 10 The contact angle test results are for the surface and internal cross-sections of the floating composite photocatalytic material recovered after five photocatalytic degradation cycles. Figure 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.

[0172] Depend on Figure 10The test results show that after five photocatalytic degradation cycles, the surface contact angle of the recovered floating composite photocatalytic material decreased from the original 70° to 44°. This indicates that the hydrophilicity of the PVA membrane in the floating composite photocatalytic material is significantly enhanced, which is more conducive to the transfer of pollutants from the aqueous phase to the catalytic material. The surface contact angle of the regenerated diatomaceous earth matrix inside the floating composite photocatalytic material is 117°, indicating that the hydrophobicity of the regenerated diatomaceous earth matrix inside the floating composite photocatalytic material of this invention is well maintained. This not only facilitates the adsorption and binding of organic pollutants on the catalytic material, but also fully ensures the floating stability of the synthesized photocatalytic material. The above demonstrates that the recovery and regeneration method of the floating composite photocatalytic material prepared in this invention is simple, and the floating composite photocatalytic material exhibits stable structure, stable photocatalytic activity, and stable floating performance.

[0173] Obviously, the above embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for preparing a floating composite photocatalytic material, characterized in that, Includes the following steps: Using bio-regenerated diatomaceous earth obtained through bio-regeneration technology as raw material, and silane coupling agent as hydrophobic modifier, the surface of the bio-regenerated diatomaceous earth is subjected to hydrophobic modification treatment to obtain hydrophobic modified diatomaceous earth. The hydrophobic modified diatomaceous earth is mixed with a binder to form a blank; the blank is pressed into a sheet and dried to obtain a sheet-like blank; a coating liquid is coated on the surface of the sheet-like blank and then dried so that the coating liquid solidifies to form a hydrophilic film on the surface of the sheet-like blank, thus obtaining a floating carrier; The photocatalyst powder was dispersed in a modified polyvinyl alcohol solution to obtain a mixture; the floating support was immersed in the mixture and then dried to solidify the mixture into a film, thereby stably loading the photocatalyst onto the floating support to obtain a floating composite photocatalyst material. In preparing the hydrophobically modified diatomite, 0.6 mL to 1.5 mL of silane coupling agent is added per 10 g of bio-regenerated diatomite; The modified polyvinyl alcohol solution is prepared by the following steps: Polyvinyl alcohol was dispersed in water and then stirred at 80°C to 90°C to dissolve it. Then, a dicarboxylic acid compound was added and mixed well, and the mixture was cooled to room temperature to obtain the modified polyvinyl alcohol solution.

2. The preparation method of the floating composite photocatalytic material as described in claim 1, characterized in that, The photocatalyst includes a catalytic matrix and reduced graphene oxide and Ag element supported on the surface of the catalytic matrix. The catalyst matrix is ​​BiOBr hollow microspheres; The loading of the reduced graphene oxide is 2.0 wt% to 4.0 wt% of the mass of the catalytic matrix. The loading of Ag element is 1.0 wt% to 2.0 wt% of the mass of the catalyst matrix.

3. The preparation method of the floating composite photocatalytic material as described in claim 1, characterized in that, The silane coupling agent is KH570.

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

5. The preparation method of the floating composite photocatalytic material as described in claim 1, characterized in that, When preparing the blank, 0.6 mL to 1 mL of the binder is added for every 1 g of the hydrophobic modified diatomaceous earth.

6. The method for preparing the floating composite photocatalytic material as described in claim 1, characterized in that, The coating solution is prepared through the following steps: Polyvinyl alcohol was used as the coating agent. It was dispersed in water and stirred at 80°C to 90°C to dissolve it. Then, a crosslinking agent was added and mixed well. The mixture was then cooled to room temperature to obtain the coating solution. The crosslinking agent is a dicarboxylic acid compound; Add 8g~10g of polyvinyl alcohol per 100mL of water; Add 0.012 mol to 0.015 mol of the crosslinking agent per 100 mL of water.

7. The method for preparing the floating composite photocatalytic material as described in claim 1, characterized in that, When coating with the coating solution, 0.3 mL to 0.4 mL of coating solution is added for every 0.1 g of the sheet preform.

8. The method for preparing the floating composite photocatalytic material as described in claim 1, characterized in that, Add 8g~10g of polyvinyl alcohol per 100mL of water; Add 0.012 mol to 0.015 mol of dicarboxylic acid compound per 100 mL of water; When preparing the mixture, 1g to 2g of the photocatalyst is added to every 10mL 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. The application of the floating composite photocatalytic material of claim 9 in the removal of organic pollutants from water.

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